The Big Problem With Modern Manual Transmissions - Rev Hang
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- čas přidán 23. 06. 2020
- What Is Rev Hang And How Does It Ruin Manual Transmission Shifting?
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What is rev hang? Rev hang is a common problem with modern manual transmissions where the engine RPM does not drop immediately once you press the clutch in, even if you're completely removed your foot from the throttle. This delay in engine RPM dropping causes the car to jerk & rough shifting in manual transmission vehicles.
What causes rev hang? Rev hang often gets blamed on heavy flywheels, but that's not actually what causes it. It's a result of modern cars switching to electronic throttle bodies. What's the difference between mechanical and electronic throttle bodies?
Overall, electronic throttle bodies are a good thing! They provide better tuning of cruise control, they allow for smoother shifts with automatic transmissions, they can improve how quickly catalytic converters heat up by controlling the balance of air/fuel ratios and throttle position, they can improve throttle control during cylinder deactivation, they can remove driving jerk in manual transmission vehicles, they can provide safety features like improvements for stability control, traction control, and reducing throttle input if the brake pedal is pressed, and the list goes on! However, they can also be used to improve vehicle emissions, and this often comes with the negative side effect of rev hang. Check out the video to learn all about it!
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Hello everyone and welcome! Today is my CZcams Birthday, and Engineering Explained is officially 9 years old! Thanks for joining in, I really appreciate it!
As for the video, I have wanted to make a video on rev hang for a long time, but wanted to make sure I had it right. I've discussed this with numerous powertrain engineers, read through academic literature that relates to the subject, and boiled it all down in this video. Quite excited about this one, hope you enjoy!!
Thank you for helping us understand complex systems and why they're used in the first place!
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It doesn't matter how hard or soft I shift, there's still a jerk in the driver's seat.
My passengers get jostled around like a friggin washing machine
@pete smyth quality comment 😂😂
And old people like my dad and mom think I don't drive stick very well because of the jerkyness. And my mom thinks my dad is better. I think I am way better than him.
if you want to avoid jerkiness, use more clutch. But to avoid burning through it you should be able to time correctly the gear, soft releasing of the clutch and rpm, and it'll go smooth as hot butter.
@@OscarSabaterCruz You dont need to use more clutch to shift smoothly. It depends on what you'r engine rpm's are when you release the clutch. You can shift basically shift smoother than most automatics if you know how. And without sliding the clutch. And there is no need to change gears like driving a freaking race car. Rev hang can be compensated with slower shifting. Its not like you lose any time shifting slightly slower in normal driving. All cars are different to drive and its only a matter of getting adapted to the vehicle you're driving.
I had a throttle body freeze up while going down a hill in winter, now THAT was some rev hang...
Oh geez 😆
I'll bet.
Was it a 76 Rabbit? Mine was.
Might be because of the increased fuel needed to start and keep engines running in winter... could also be a leaky injector. Get your engine checked out.
Drive by wire?
I surprisingly understood everything. And I'm a dentist. As they say.. if you can't explain it to a ten year old, you don't probably understand it yourself.
All I keep imagining, is a reverend throttling a dead body, and being sentenced to hang.
Never met a ten year old dentist before. Well done
@@Tom_Hadler beat me to it.
I'd wager he's probably pretty good at understanding most things if he's a ten year old dentist.
@@Tom_HadlerJudging by his login, he's from India. Everything's possible there 🤐
@@dehypnotizerz The founders of the internet started it in the hopes of making the world a better place to live.
They forgot to account for your existence.
You failed to mention that cable driven throttles usually have some mechanical non linearity built into them. If you look at the part the cable goes around, you will notice it's oval. Otherwise good video.
I have just converted my car to drive by wire with an aftermarket ecu, and can confirm no rev hang, it's all in the tuning, as you say, it's a deliberate thing built into Oem cars, not a limitation of the technology in general. Electronic throttle, when you can set it up yourself is awesome.
We use different throttle cams on our motorcycles to change this.
@@petebusch9069ya I'm really surprised a channel of this quality didn't mention that throttle cams are almost never actually just round and are almost always oval or egg shaped for this exact reason
The answer to any modern car problem: “it’s to control emissions”
Ikr. It's quite ironic that 90% of the cars in sale are crossovers. Because they are sooo eco-friendly
Yeah but it’s understandable I mean at least they are trying new technology to help save the planet
@@jupitersailing6911 I think it does not make any difference, whether you want to decrease emissions or not, it will not destroy a planet
and that's why we are going to shift to electric drive sooner or later, subsidized or not
Yes - and this is nice way to sell it to the public as: there is plenty more reason of course. For instance it is much cheaper and easier to have an additional cable in the harnees to to the engine, compared to the good old wire-able solutiion. And e-gas usually takes its data from a data-matrix in the cpu - data based on the manufactures measurements during vehicle developme'nt.
But some of theses e-gas just seem to be bad quality, cheap plastic etc. and often don't last very long. And the production, distribution and installation of replacement parts is as well effort, harming the environment.
good thing that my throttle is cable operated
then again my scooter doesnt have any gears...
Probably has a carburetor as well, doesn't it? Would be interested to see these curves of lean/rich mixture when closing or opening the throttle valve of a carburetor-engine :)
HECKproductions a Cushman possibly. Slowest scooter ever developed.
My scooter had cable operated throttle. It snapped @120km/h and stayed wide open when I had to brake for a corner. I'm alive only because I reacted fast and hit the engine kill switch
@@BoliMeKurac Learn to check cables! I had a drywall jack fall on my head because of a faulty cable.
same, but i dont even have a car
I would love to see a modern engine with today's materials and tolerances ran with all mechanical/carb then converted to all electronic and see the actual mpg differences and emissions.
Well EFI does help.
I can't say the same about Electronics throttle body
@@atarvhegde5210 All these things "help", I just wonder how much. 1-5-10 mpg. Something like a mid 70's slant 6, remade with all modern tolerances and materials comes to mind. That thing got nearly 20 mpg at 3.7L,,,, just at 125 HP, but it was a loose motor.
Eric man , you gotta come and live in the 21st century man
@@jeevanrohtak5126 Jeevan man, you gotta pay attention to what I said. I shall explain it to you, since you seemed to have missed it.
I am curious how much fuel efficiency is in the electronics, vs the upgrades machining technology and materials.
So, in short, pay attention to what I was saying, and not what ever thought just possessed you to type what you did, man.
There would be no way to make it streetable unless it had a much milder camshaft and smaller intake ports. Also, today's emissions standards almost require a dry intake manifold. That's why no throttle body fuel injection. It wets the intake just like a carb does.
Literally couldn't be a more intuitive and thorough explanation. That was an amazing video.
I’ve seen mechanical throttle bodies with a “cammed” lever so that the airflow increase is more proportional to input at the accelerator pedal.
thats really interesting, thanks for sharing!
I think that most have that.
@@aitorbleda8267 Yes; I was surprised he left that detail out. I was all but shouting at the screen over it.
I believe Porsche used that in their older (?) cars. So that the driver gets a more aggressive feel when applying the accelerator.
Honestly I haven't seen many that don't have a cammed lever.
I don't know why I'm watching this, I can't even afford to fix the suspension in my 1993 Audi 80.
Edit: As of last month, sadly she is deceased, had a crash at a car meet, front ended up totalled, wrecked intercooler. Spent some good years with her, Rest in Peace.
B4 2.0L?
@@toottootfuckshit8755 B4 1.9 Turbo Diesel
I have the 2.0
F
The people are supposed to meet, not the cars! Sorry to hear about your 80. I had an abusive relationship with a 4kq.
Idk why I'm watching this, my car is carbed.😂
Cus it's fun
Bro my exact thoughts as I clicked on this
W
I dont like my carb so im gettin a throttle body injector
I don’t know why I’m watching this, I can’t even afford a car.
I would love to see you take a shot at tuning a car. With all of your knowledge, that may be interesting to watch.
He had an s2000 which he supercharged (and then sold for the mx-5) and a integra he tried a small series of build vids on, but it got stolen or something.
With modern cars, tuning has become obsolete, impossible to do and unnecessary.
All "tuning" variables are controlled by the Engine Control Management computer via sensors and electric/hydraulic actuators. The ECM senses all properties of the air going in, the exhaust coming out and controls all aspects of combustion through throttle, spark, fuel and valve timings together with auto trans behaviour (if equipped).
This makes tuning a modern engine impossible as there is nothing to tune. Optimal operation is maintained on the fly, hundreds of times/sec and compensates for all external variables including changes in the engine as it ages and its internals get worn and fouled up. The only way to alter this behaviour is to re-map the ECM's memory using a proprietary, car make specific, ECM programmer, access to which is tightly regulated and controlled and the cost of which is very expensive.
As for older cars, he would most likely struggle and fail. Being an experienced mechanic and a knowledgeable engineer are two completely different professions comprising of very different sets of skills and abilities.
@@PushyPawn What fantasy world do you live in? have you ever heard of flash tuning? it exists for pretty much everything out there.
@@PushyPawn In current times, "tuning" is a word that refers to ECM/TCM recalibration via flashing the memory.
We aren't talking about the primitive engines of yore.
@@CalculatedRiskAK right lmao? like this isn't obvious information already/even inconsistent with the video, having "modern" in the title
Every video I see like this just gives me another reason to hang on to my 90's cars.
welcome to club. im still driving 1977 carb car with only electronic device being radio. ill take old car everyday over these pieces of junks they call cars nowadays. imo theyre more like robots. you cant even do what you want, emissions emissions emissions everywhere
I know, right? I kept my clydesdales and carts, and I never experience rev hang!
Ultil they are so old they fall to pieces.
Yea stay in a cave
This isn't a new problem. 1975 VW Rabbit had major rev hang. It had an "anti-backfire valve" that held the throttle open. It was pretty awful. Without the valve, it backfired EVERY shift.
My dad has a 19 Subaru Impreza, It's the first car I've driven to have so much rev hang that I needed to learn how to drive "around" the hang. I thought it was just a crazy heavy flywheel! Great video! I'll have to check it out later lol
Thanks for sharing, I have an Impreza from the same year and this makes me regret getting the cvt version less.
You totally nailed it. I used to do emissions testing at Ford back in the 80s when cars were transitioning to 3-way catalyst necessitating, prior to EFI, feedback carburetors to attempt to control to stoich AFR. But with carbs there were all sorts of AFR excursions during transient tip-in tip-out modes, and on a tip-out, all the wet fuel clinging inside the intake manifold suddenly vaporized and sent this huge HC spike which blew through the oxidation catalyst. Remember dashpots on the carburetor? This slowed the closing of the throttle to it's idle setting to attenuate the fuel vaporization rate, the first form of rev-hang. But even on my 93 Mustang with EFI and cable actuated throttle, it has the annoying rev-hang, but this is the idle speed control valve acting, like drive-by-wire throttle, to bypass air to achieve the same emission control goal. Just some retro perspective to ponder. The guy below said it succinctly, 'it's to control emissions'. Today, there are regulations to be met, vastly more stringent than the 80s. Give credit to the engineers that achieve them and build engines like the Coyote, LT6 and Hellcat.
4:07
This engine is super clean.
3:34 SUPER CLEAN
sUPeR ClEaN
Me: presses pedal to 25% hoping for 50% air
Gets 25% air. :O
Windbooster throttle controllers
I really enjoy your videos. As a car enthusiast, I feel it’s important for me to understand how cars and all their components work. Your videos make that easier for me!
This was a great video! It made me do some thinking about a 2002 Mustang 4.6L I had years ago. It had terrible rev hang, but mechanical TB. The fix was to restrict the airflow of one of the lines connected to the TB by inserting a metal plug in the line with a small hole drilled in it to allow a small amount of airflow.
I can only assume that this line was how the ECU added air when lifting off the throttle similar to what you explained here. By restricting that airflow, the rev hang was reduced.
I love watching these videos on my lunch breaks lol. Everyone assumes I’m taking an online math class or something lol
I’m doing that right now!
Lol on my lunch break too
Me too lol
Oh my lord I cant believe I'm not the only one
Well that's because you are LOL
Dude... I’ve been wondering about this for YEARS with my car and never thought it had anything to do with the drive by wire throttle, just the stock flywheel. Thanks!!!
Compared to my s10 or 10 speed big trucks my civic si is not as smooth due to this I'm not as consistent
My vehicle has a mechanical throttle, but I have lots of rev hang. I bet it's using the idle air valve to accomplish it.
@@nerdyengineer7943 me too. My 04 gto doesn’t have rev hang but the initial grab into 1st gear has always been the most finicky I’ve ever felt in a car. I had a 2001 cavalier z24 manual 5 speed (obvi with fwd and electronic throttle) and for some reason engaging first in that car was way simpler than the gto. Any other gear from second to 6th is completely normal (tho a bit slow due to the weak clutch/slave from the factory) but something about 1st gear in it with the drive by wire creates the most odd feeling 1st gear engagement
@@davidpistek6241 lol Im in the same bag. My s10 extreme drops the rpm’s fast so I can shift a lot faster. My type r…. The rims take forever to drop. I don’t go hard in the car but when I do I might bang gears. 6000+ rpm’s can’t be good for my clutch. Smells stronger than any car I’ve had. My s10 or Camaro ss have never smelled like burnt clutch while banging gears.
My 08 Ford expedition with drive-by-wire 1.4 low it changes the throttle input so if you bounce on the throttle it won't be jerky and full it changes the throttle input so if you bounce on the throttle it won't be jerky in low range four-wheel drive smooth
Excellent description! The other day, I drove a 2018 Jeep Wrangler with a manual and I noticed the rev-hang and the rpm being too high when I hit the next gear. I drive an older Alfa Spider that has no rev-hang and I can feel the rpm match as I up shift. With the Jeep, I was always at too high rpm.
I owned a 2017 Toyota Corolla iM and I also noticed the rev-hang. I thought it was due to how freely the motor revs. Now that I've watched this video, I understand the process.
Thanks again for another excellent video!
"Can remove driving jerk..."
*shows himself driving*
Oh so that's why my car sometimes jerks when I shift and keeps the revs longer than older cars when clutched in... Good to know :)
Yep. I just spent the past handful of months learning that the hard way, and then this video comes out. I learned to drive on a throttle cable - and when I got a newer manual it took me forever to drive it smoothly... and I have to wait sooo looong between gears. Yes yes fuel economy but I WANNA DRIVE
yep quicker, more difficult clutch jobs.
I just thought 5 years off the road had just made me rusty
When u shift up for example from 2nd gear to 3rd gear do not fully release accelator paddel try to keep u r car in 1500rpm when shifting up u r gear .. in this case ur car engine will be in motion and u r car will not jerk by releasing cluch
I was thinking iam shifting my car wrong all this time lol
Makes me remember looking at my BMW E46 shop manual and seeing the electronic throttle circuit labeled as "Torque Request". We know who's the boss now...
*Skynet sees you*
It ain't the driver. With antilock brakes, traction control and electronic throttles, the computer's in charge. Don't get me wrong: that stuff works amazingly well most of the time, but I do find that the traction control especially on occasion will cut the throttle back to nothing at the worst possible time.
That was the big thing that stuck out to me when I test drove my '13 Civic SI. Compared to the RX8 I was trading in, there seemed to be substantial rev hang.
There was zero rev hang on my RX-8
You absolutely nailed it when you explain the advantages of electric throttle for the driver feeling part. Thank you so much!
4:08 look at that SUPER CLEAN intake hose
Thought no one's gonna notice that LOL
Someone’s watching Chris fix videos 😉
bahahaha
I've had this for the first time with my Evo X and I thought I was just being a terrible shifter! I tried to explain it in the evox forums and everybody just said I was shifting wrong. Glad someone finally got this fully explained out, it was fantastic!
If you've driven older cars or a different model that drives properly then coming to this will frustrate you a lot.
I had the same exact thing happen to me in the Scion tC community. Everyone told me that I was either shifting wrong or Needed to get a lightweight flywheel 🤦♂️ I just wanted someone who could tune it out
Evo X also and first time I experienced it as well. Wondering if it can be tuned out during the performance tuning process.
I had a carbureted vehicle with a vacuum dashpot actuator to accomplish the delayed throttle butterfly closure, too. That general system was not exactly uncommon toward the end of the days of carburetors on on-road automobiles. It’s also interesting the discussion about how one _could_ use electronic throttle control to make the relationship between pedal position and delivered power more linear. Why I think it’s interesting is that we don’t see that actually done. What we see instead is that electronic throttles are programmed to provide ridiculously overdone tip-in, because that makes people _think_ their car is really fast.
What’s crazy is, I had no idea what I clicked on and was just trying to see another informative manual trans video. After watching, I realize that this situation implies to me so directly and I had no idea it was happening. My last car had so many emission problems to the point I dreaded my two year testing period 6 years straight. I see now I had a serious top out problem and my new car definitely solves the issue.
Can we just be happy that at the very least manual is still in some cars, we need to appreciate this more.
That wont be for long unfortunately
@@snowysysadmin59 Mine will never leave its body
I managed to get a 2012 Chevy Sonic with a 5 speed Manuel and I barely feel a jerk.
Ford just announced a new manual (the bronco) not that long ago hopefully this means they come back if it’s successful
@paul. Here's hoping
Rev hang kills the driving experience for me, and it’s why I will soon be selling my manual Crosstrek. It just feels like such a chore to drive.
Haha, the Crosstrek isn't exactly a great representation of a fun to drive vehicle, but it's an excellent car. I'm happy with the manual.
Crosstrek...the ultimate enthusiast driving vehicle.
I have a manual Honda Fit, and while I'm not thrilled with the shifting experience, I wasn't expecting much- it's an econobox, after all. Even with the complaints, though, it's slightly more fun to drive a manual Fit than a CVT, and more important to me is the fact that any extra physical engagement helps keep me that much more alert.
I feel the same way. I despise my Honda HR-V because of it. But now I can be at peace with it. But the first chance I get to burn it with fire... errr I mean sell it and get something better, I will
Realized with many cars with rev hang that if you lift off the gas pedal before pressing the clutch it usually works much better.
Completely counter intuitive but I tried this on many cars and it seems to work. Of course for race starts it doesn't work and shifting is awful 😊
I'd rather have the throttle response of a mechanical throttlebody as I'd like to tap the petal to revmatch and not stomp on it
I agree rev hang as described totally ruins the enjoyment of driving a manual transmission
If I am in control of the car I WANT THE CONTROL!!!
Windbooster throttle controllers
True, this is one problem I have with a drive-by wire gas pedal
I got one of those aftermarket adjustable electronic throttle controllers. It’s pretty sick not gonna lie.
@@LeDank when you get it?
This dude is so clear and concise on difficult to describe subjects. I love it
Sometimes I fail to understand half of what he's talking about, but despite my ignorance I always appreciate this man's passion to explain everything and how much he knows his stuff. Happy birthday btw, best wishes from Argentina
I've always heard that Subies had rev hang because it helped emissions and I'd always been curious as to how dropping the RPM slowly would do anything, so now I know! Great video, thanks!
the software throttle is also a pain for hill starts with cold engine (stickshift 2011 outback)
This is a lot of cars, the EGR feeds back into the intake and the idle-bypass will be open during liftoff so lots of rev hang. Its the same bypass that makes your engine idle high in cold starts.
They fixed this in the new wrx
My SF Forester has the most obvious hang of any car I've owned, it got more pronounced when I cleaned out the intake and Idle air solenoid, I thought I may have busted something at first.
I drove two Subaru's and to my knowledge, neither of them had it. Both were standard and one was an Impreza and the other one was a WRX. I have a Honda Civic Si Coupe now and that car has massive rev hang. I haven't experienced it in a Subaru yet to my knowledge but I know Honda cars have it in some of them. It's really noticeable in mine if you look at the rpm's closely when you're shifting the gears.
Incredibly interesting video; I notice this with my recent new cars and have learned to adjust for it by waiting for revs to drop before shifting. But it’s annoying.
this is so informative. Never knew electronic throttle had so many benefits. I have just written it off as newfangled over engineering. Especially with a stick shift I'm constantly tipping in and tipping out. Never knew that was creating more emissions.
Rev hang is my excuse when I lose to ecoboost mustangs in my base model 2019 Mazda3
Although in a race scenario it would help you go faster because it's kinda like a half of a power shift. But I got the joke lol
Nathanael Naused i was able to keep up with my friend’s ‘01 Audi A4 with a v6 so it perhaps helps a bit.
A first-gen Mazdaspeed 3 would put the hurt on an ecoboost stang
Few things are more satisfying than responsive revs, up or down. Rev hang ruins the manual experience
Got that right. I want my car to jerk left when I stomp on the gas, and jerk right just as fast when I let off. A motor should decelerate just as fast as it revs up...
I agree. Some modern manuals will prevent the engine from stalling or even restart automatically. Enough. Make manuals actually manual.
Right? Idgaf about emissions on my weekend car, I just want it to feel like a real car. Not like these babysitter cars that have 100 different electronic systems on them (like ESC) making everything feel numb and dull.
They should keep it electronic for automatics because of the listed advantages (especially as the sensors/computers get more complex they can boost efficiency) whereas manual should be a simpler mechanical system the way people understand (at the cost of some engine-level controls that are only possible with the computer system anyways)
Plus someday there's gonna be a significant split to self driving cars where there is no human-shifting or "pedal feeling" anyways
Gainz plz to be fair they have some advantages for performance too - humans only have so many limbs but the computer can control/monitor hundreds of points, but like he said it's up to how the computers are tuned/configured - most consumer cars right now are just meant for a smooth efficient ride... they should give more options to have either manual or power/control-tuned systems (interestingly, Tesla cars have some of this: because the motor is entirely electronic they can accurately control stuff like how much power is pumped into it at different speeds - apparently destroys your efficiency but gives crazy acceleration especially at low speeds )
Definitely need more modern cars that keep the "fun manual" experience one way or another though :/
Man I like your videos so much, even though I get bored about that part of mathematical calculations you always do.... still, you are a natural great teacher and I admire the energy and quality you put into your content. I will always support you no matter when you get boring. Congrats!
Informative and good explanation. Note that even some of the last generation of electronically modulated carbureted cars in the early to mid 80's used dashpots on the carburetor to delay throttle closing.
On one of my carbureted motorcycles it has different cable cams to change the rate the throttle is open in relation to the grip. Still if you wack it to WOT it’s still open but it does help make the throttle position to power out put more even. Also on fly by wire motorcycles the slight delay in throttle response is really noticeable. Every time I get on one it takes a few minutes to get used to it. On motorcycles where you’re so connected to the machine and road the fly by wire is not my favorite thing. I believe they can make it better and throttle hang has never been an issue I’ve noticed on them. Could be due to the ITB that motorcycles have.
Jake TheGardenSnake i have ridden newer bikes where you dont really feel the delay but older bikes with e throttle do really feel different. Also carb vs no carb.
I was thinking the same thing. Just take a cable cam that is elliptically shaped and it would start opening slowly and thereby straighten out the torque/throttle position curve. Cool to hear that they are using that on motorcycles!
The carbs on the old bikes I've messed with have a vacuum-regulated venturi downstream of the throttle plate. This is essentially a gate valve that restricts airflow like the throttle, but for the purpose of maintaining uniform air speed through the venturi to ensure consistent fuel draw and atomization.
I haven't ridden a motorcycle with electronic throttle, but I would expect any delay to be disturbing.
Hey, Jake! Wanna say some cars have the same "cam" on the throttle shaft.. love the vids!
Love your mt07 series Jake, but I couldn't get over the jerk throttle response of mine. Got a cbr650r. The jerk is still there but much more maneagble in a smooth 4 cyl.
I seem to remember that cars with a mechanical throttle would rev hang. There was a device called a dashpot that slowed the closing of the throttle thus reducing emissions.
Correct. Tune can help this or some physical mods to the valve.
Yep, exactly right. I think the N/A AW11 MR2s used a dashpot, but the supercharged ones didn't, for example. On the other hand, all 3 cars I've had have had mechanical throttle bodies without a dashpot, so I don't think this method really took off until the electronic throttle bodies made it trivially easy.
Those were mostly on cars with carburetors. They tended to run very rich coasting at minimum throttle, which meant they ran very dirty. The dashpots I remember were vacuum operated and would keep the throttle from closing fully until the RPMs came down.
Yup, a mechanical solution but for the same reason.
I loved that SUPER CLEAN easter egg above the intake conduct on the cleanest car.
I bought just recently a Focus from 2020 having driven a Punto from 95 and I always felt that jerkiness while driving my new car. Thought I was the only one. What I found out was that I have to hold the clutch slighty for about a second before fulling releasing it, and that probably gives time f or the revs to go down. However, if I'm pushing the throttle and going faster I can change gears faster. Makes 100% sense on what you said, very informative!
Thank you! After I got my manual BMW, I thought I had forgotten how to drive stick because I kept getting weird revving when I was shifting. Now I know what it is!
I too experienced the same thing. It is still driving me nuts after a year of owning the car
@@L39T I was learning to drive stick on a new Subarua and was pissed that I have to wait for something to happen when realising the clutch.
just give it some gass when you let the clutch bite. or a lot of gas; the 6 speed subaru transmission is pretty strong now :-)
Many manual BMWs also have clutch delay valves. Look up if yours has one and get it either removed or replaced with a valve that doesn't delay.
4:09 So considerate of Jason to thoroughly wash his engine bay so that it’s super clean on this video! 🙏
Looking for this!
Chrisfix has entered the building...
It’s not a grocery getter, it’s real world used.
@@nopleaseno2515
I think you might have missed the joke. Have a look at the fragment in the video. Jason had left a message there. At 4:09
@@Conservator. oh yes you’re correct. Guess the joke wasn’t funny.
Excellent explanation ! Years ago, carburetor dashpots were a crude attempt to accomplish the same thing - with the same Rev hanging problem. I have a cable connected to my gas peddle and I do NOT treat it like an on/off switch, though I'm certain I'm not as clean as a modern microprocessor - you'll have to pry cold dead hand off the shift lever on my 1996 GSR
I like how far you went to fully explain it. Precise and thorough
all this "smoothing" the ECU does leads to the driver instinctively counter those effect with harsher throttle control, defeating at least partially the purpouse. :)
100% real
Airbus had this problem with early fly by wire and pilots over adjusting controls due to the lag between pilot inputs and airplane adjustments.
I'm always flooring my manual and shifting low RPM, just so I can shift swiftly and smoothly O_O
Yes
Yep
Imagine this: carburetors would actually fix the throttle tip in and tip out problem.
I mean there's a million other problems it comes with but it fixes the problem.
he should make one big video about carburators. people these days are not familiar with carburators at all. with carburators once you let off throttle, the vactium starts sucking alot of fuel thru idle jet, and its massive amount that it sucks there. this was on old carbs so with old carbs you saved fuel when you went to neutral when letting off the throttle because it sucks tons of fuel when throttle is closed and rpms are over idling rpms. now newer carbs in the end had a valve that closed idle jet channel when rpms were over some certain rpms and throttle was fully closed. it opened back up if you press throttle or rpms droped below this certain rpm, but even this sort of system richens af ratio when coming off the throttle cuz it takes time to close that valve. but it did improve fuel consumption. now carb system itself always has problem that when you press on the accelerator the mixture is very lean for a moment, its that much that engine actually might want to shut off. this is mostly because some channels little bit flow down so the fuel isnt being sucked instantly and it takes slight time to suck them back up. to overcome this very lean mixture, all of the carbs (not including small scooter and chain saw carb cause their engine size is so small that theres no need for this thing) have a thing called accelerator pump which straight up pumps fuel into the intake while your pressing the throttle. full throttle press gives you about 10ml of fuel in the intake (this amount is taken from 1.5l inline 4 engine). now this fixes the problem of lean side, but it actually richens mixture alot so again you have bad emissions, so mixture with tip in and tip out is very rivh. now this accelerator pump is very useful for cold starting. you pump certain amount of fuel into the engine, and my car has started instantly even with -30degrees. something injectors never achieve cause they need first 2 rotations to get pressure up in fuel pump. carbs have, and always will have worse emissions compared to injection.
@@matufujiwara7493 I live in Puerto Rico back on the 80's and we let our cars in 2nd or third gear going down the mountains to preventing boiling the brake fluid b y over heating the brake caliper going down hill for 10 minutes straight. When throttle body is close, it can't take more fuel than the idle jet will allow because there is a size restriction that won't allow more fuel trough the passage. therefore It will use no more fuel than what it will use for idle.
You also just described what Banks monster pedal does. Good job as usual.
What a fantastic and educational video!! Really well explained and you answered all the questions I've been wondering about!! Thank you for solving all the mystery out of it!! 🙏☺️
I always thought it was due to the heavy flywheel! I hate the rev hang on the ND :) Thanks for teaching me something new once again
I'm not sure what you're comparing against, but rev hang on ND is actually quite minimal. The Crosstrek is awful haha.
I cant even drive any car thats drive by wire, my shifts turn to dogshit compared to my e34 bmws
@@EngineeringExplained The rev hang is definitely less than some other cars , but it's still very noticable on my ND when compared to my NB. I thought there was something wrong with my car when I first bought it, but I have since gotten used to it. Great video as always!
@@jesperviktorsson8027 practice makes improvement, surgeons are not born; they are made // hang in there :P you eventually master each setup ///
@@EngineeringExplained The rev-hang is much more pronounced in certain makes while others don't have it at all. If yours does, with practice it can be avoided by including ~1/2 second wait between lifting off the gas pedal and pushing in the clutch to change gear. With enough practice this timing becomes automatic, you stop noticing it and there's no time/performance penalty when changing gears.
Me: EE has a new video out but the topic doesn't really interest me
Also Me: Watches the entire video and learns more than I ever did in a day of school
SAME!
LOL did you pay attention in that day?
@@the_kombinator Absolutely not. This is all making sense now.
You know where he learned this stuff?
@@kyleklassen3660 At a Holiday Inn Express?
Awesome flick! Perfectly explained many aspects of my own car that I’ve always wondered about, thanks!
I enjoy the depths you go into every project! I’m a fan of both setups. Application of when and why you use these two types is real.
Great explanation. Wondered why I could never get my new Civic 6 speed to shift smooth, especially from 1st to 2nd.
Same here first to second is the worse in my mazda
I have an 18 si, rev hang used to be really bad, but with a tune, it's pretty much gone. I also have a new clutch with lightweight flywheel.
Yep. The thing I miss most about my 6th gen Civic is its gearbox. It gave close to zero fux, and shifted as fast and smooth as you could. Meanwhile my new car with its bigger and more powerful engine is WAY more sedate because shifting is more like throwing a baseball to someone across the field than tossing it between your own hands.
Same on my dads '13 1.6D focus
Get a Ktuner or Hondata. You will have the option to turn rev hang off (as well as many, many other things). You can also turn on launch control.
still haven’t decided if he looks more like a 23 or 46 year old yet.
he is a 46 year old 23 year old.
his skin is super smooth for a 46 year old so he's probably much younger than that.
Yes
He is like Tony Hawk. An old young adult. :)
isnt he like 30?
Your videos are amazing, I appreciate all of the graphs and numbers as an engineering student
This is a great clip! Would be great to see your thoughts on a diesel in the same situation. Am aware of things like lag etc. Residual boost, common rail and no air restriction. Plenty of diesels have over Rev when changing gears!
and i thought my car was broken, that clears things up
Me too!
MAP OTS tune with a Cobb access point eliminated my rev hang, gave more power, and no lift to shift for my WRX. Best 600 bucks I've ever spent.
But for real though, if I waited for my rpm to match for my upshift while going up a hill, my truck would literally be rolling backwards by the time the rpms matched.
Solution: shift into reverse
That's unfortunate and I know what you mean.
@@doogetube6017 nice
trucks also have very heavy flywheels because it helps with take-off when towing or offroading.
As the owner of a 2021 6.4L Hemi (all modern Hemi engines port-injected) Challenger with 6-spd manual, I appreciate this explanation very much! It explains the weird behavior on shifting that I noticed every since I bought the car. (All my previous manual-trans vehicles had mechanical throttle body.)
My 2016 Kia ceed direct injection had terrible rev hang and hated it for it. I always thought it was due to the flywheel, so thanks for the very informative video!
Finally know why shifting into second takes so long.
Also adding trickyness to the 1-2 shift is the fact that it’s also the largest gap and the revs have to drop the most. The gap is smaller for every successive shift, making rev hang less and less of an issue.
Unless you drive a semi. Each of the 18 gears has exactly the same space. You learn a rhythm and shifting a breeze. Most truckers only use the clutch to launch, and then shift every other gear without clutching. But that’s a whole other video ...
@@ianswitzer2915 I heard about shifting without clutch in semi trucks in America, but never heard about it in Europe. My dad who is a trucker here in Europe never heard about it. I think that a lot comes out of European truck's being made differently. But my dad now is happy, that he drives Volvo with new automated gearbox =)
Btw, clutchless shifting is very popular in motorcycles. Especially if you are more kind of sporty rider. Even without quickshifters, which cut ignition while doing gearchange (and that lovely bang when fuel get's burned in exhaust).
@@Stasiek_Zabojca if I recall, some (or many?) bike transmissions actually use dogs to engage the gears instead of the smaller teeth from synchronized gearboxes from most cars, so it happens easier.
Those 18 gear 'murrican semis are a beast of their own too, they don't have synchros from what I know, 6 gears on each normal, high and low, pneumatic assisted. I remember asking some truck driver how it is that he operates them, from what I remember he said pretty often he skips quite many of those gears or the entire section (low, normal or high) and so on, or just wack the shifter to the side, and the air assist shifts to the next gear.
It's also common to grind gears sometimes on those, no matter how experienced.
@@Stasiek_Zabojca Clutchless shifting WAS common in Europe back in the day when manual trucks were the only option. Synchronized transmissions were introduces quite early into trucks in Europe but the legendary Eaton-Fuller is not synchronized and requires clutchless shifting to work properly.
@@Kalvinjj
Every bike uses dogs.
Basically all sequential transmissions are dog boxes.
The Geo Metro was magnificent in its simplicity
That is the one main thing i miss about my old Suzuki Swift..(same as the Metro there) :( That throttle feel/response is whats missing from every other car i've driven...
I had 3-cyl metro with a 5speed. I absolutely love and miss that car.
@@joesdiy4260 Imagine that with the 1.3 86hp version.. For it's 850kg :))
...And got Hybrid-beating gas mileage, back in the early '90s. Incidentally, the only speeding ticket I ever got during that era was from flying downhill in a borrowed maroon 3-cylinder Geo Metro. 😁 You had to have driven one to understand.
Such good info my dude, keep up the amazing content! Love watching your channel
Well explained. Thank you. I've learn something on my car.
0:00 Oh my lord... graphs.. such beautiful beautiful graphs. this. this right here's is the reason I come to this channel.
Excellent explanation. Bought my first brand new car in '98 and within a few months my shifts were buttery smooth and my r/t at the track was consistently
This is absolutely STUNNING. Fantastic! Thank you for answering everything I've been trying to figure out with manual transmission frustration. Amazingly well researched and presented.😀
Thank you very much for the video. I was studying to replace my 2011 Chevrolet Celta flywheel to a lighter one thinking it was heavy and causing the rev hang that were really annoying me because I was thinking I was changing gears so fast that I had to keep pressing the clutch until it dropped RPM to stop unmatched gear shifts.
I noticed this happening when I first started driving.
I developed the habit of letting off the throttle before I disengage the clutch. Haven't experienced it anymore
Edit: or well, not perceiving it.
Yeah I feel like if you own a car then you get used to it and it’s not a huge issue, I wonder if he just notices it because he’s reviewing different cars all the time?
I've noticed this with rental cars. Throttle flat on the floor, then let off the throttle completely and... The car still seems to be accelerating for a moment or two
@@theydidntnameme put in sport mode, this enable the accelerator to react in a sharp mode, but normal driving consume less fuel because of these slow operation that discard some unwanted oscillations that our foot create (i.e. his mass and pot holes or uneven road)
I did this also.
Drove a 2008 manual with electric throttle for 9 years. This is exactly how I defeated the issue. Fuel deceleration cut off
The other way electronic throttles can improve efficiency with an automatic transmission is running the engine wide open in a higher gear, but still having pedal travel left to demand a downshift.
Gas pedal down until you feel it's about to shift, get off the gas a little as it shifts, push the pedal down a little after the shift and instead of dropping rpm with the shift and slowly crawling back up you get a nice shift and then Rev back up quickly. Love that feeling in a moderate to low horsepower car just getting up to speed. Smiles per gallon haha
That's true, reduced pumping losses.
@@averyalexander2303 Don't forget reduced frictional losses and accessory parasitic (hydraulic power steering, AC, iron losses in the alternator, belt, etc.) from reduced revs.
My V6 Tacoma: **Climbing a hill, losing speed** Don't worry, fren. We can lug up this hill in 6th gear.
Me: **Applies 6% more throttle**
My V6 Tacoma: Oh, I see you're asking for a tiny bit more torque. **DOWNSHIFTS TO 3RD, ENGINE SCREAMS!!**
20 Years or so ago and earlier, this function was served by a simple button/switch behind the gas pedal. The end of pedal travel matched full throttle but if pushed harder this would press that button signalling the auto trans to downshift.
I love your videos, I have a vortex super charger on a 2013
Mustang 5.0 automatic. I recently installed this module
From Hikeit with plugs into
The gas pedal connector and
Can program different throttle
Curves. The difference was dramatic and this video was do helpfull
Oh wow, very deeply explained
The way you explained and the study you did on this is much appreciated 👏👏
Thank you brother 👍😊
Thank you for solving a very heated debate between myself and 2 other senior techs at work. You've made me one very happy man.
But just think of how sad those 2 senior techs are now.
They’ve probably never driven manuals. Lol, jk.
I used to remove my ABS fuse to drive in the race track, that made my throttle body more responsive to make a perfect heel and toe. Now I know why it worked.
This makes so much sense. I have a Miata and a crosstrek 32 years apart. Miata is mechanical and performs as explained. However sometimes I need to go full foot down on crosstrek to get performance I’m looking for
I find myself back on your channel after about 10 years. You look so much older. Glad to see your still teaching us
Great video, Jason! Thanks to your videos, I enjoy driving my manual car even more, being aware of what exactly goes on inside the machine while I use my hands and feet. Great to know you enjoy manuals too. Pity they're going away so rapidly. The way you explain complex engineering concepts and devices is just amazing fun to watch and easy to follow. Keep it up! Cheers, Govind
Simple fix for rev-hang: install a tune. Installing Hondata's on my 2020 Civic Si completely changed the shifting experience.
Yeah. The rev-hang on my Si is horrible. Just horrible. Shouldn’t need to go aftermarket to fix - but it is what it is.
@@GregBalzer Same was with mine. But after installing the tune, it's a completely different car and the gearbox is among the finest you can get. Getting rid of the rev hand alone made the tune worth it, the added torque and horsepower available once you press the sport button, a VERY nice bonus.
Same with my '06... the hang at 8300 was about a second long after you push the clutch in before I got a tune and it would rock back and forth
Someday I will go down this path on my 2018 accord 2.0T with the 6MT. Rev hang sucks on this car, but I love every other aspect of it. I find that driving with AC on helps a bit, but with AC off it is awful.
I was wondering if a tune could help this. Might it cause problems during emissions testing?
1) Yet another excellent presentation. I am an engineer myself and I always learn a ton of new things from your videos. Thank you, sir!
2) 11:38 Literally laughed out loud at the 'Super Clean' written in the dirt build-up. ;o)
4:08 I agree with the statement. That is the cleanest engine bay I have ever seen
Thanks for the lesson once again! This is a big problem in my '19 Mustang GT when I'm on track. Imagine trying to shift into 4th at 110 mph and having to wait for the revs to slowly creep down from red line :(
If your doing track days you should look at getting a tune to fix that
Tunes usually change this behavior, or an experienced tuner can do it without much fuss if that's the only thing you want changed.
I had a 2015 mustang gt. Just get a tune, Id do e85 or flex tune if its in your area and simply ask to remove the rev hang. I think some tuners leave it in because some people like it like inexperienced drivers. It was always known the 1 to 2 shift always made the car jerk unless at red line so people just got the rev hang removed with the tunes.
Fuel not burning off when you let off the throttle to change gears?
Flat foot shift. Boom. Fixed your problem.
Perfectly clear. Thanks!
Wow I went to school today and learned something....excellent explanation....
On the race track the rev hang doesn't allow engine compression braking to slow the car and rotate it into a corner. You're left with having to use the brake to rotate the car so you lose one of the car control options available. BAD!!
If left in gear the rev hang time is minimal I think and I'm pretty sure that it can be turned off with a tune... it's also a tradeoff minimized by the potential for computerized rev matching on downshifts. I always had a hard time blipping the throttle with my heel during mid turn down shifts.
My Ford Focus ST is pretty good in this regard but I have driven other modern manuals where it was very bad, a Honda Accord sport comes to mind. My Tesla on the other hand, can’t get it out of first gear so it just hangs all the time. 🤪
My GTI isn’t bad but I had an 8th gen Civic Si and the rev hang was brutal.
Honda has killed the manual transmission because of this
That problem with the Tesla is easily fixed:
Just load it up with high octane and thats it.
Bam! Fixed.
K C You can get Hondata to fix the rev hang, a good friend of mine has a tastefully modded si that’s a real blast to drive. It’s so driver-focused
That's a great car drove one w 3 200lb dudes in it and it still got it done. Would recommend one, amazing brakes!
You’re really good at these things bro please continue 🔥🔥
I wish I found this video like 2 years ago. I had this question and no answer I got quite made sense but this explained it perfectly! Once again, thank you Jason
Some: MECHANICAL!!!
Others: ELECTRONIC!!
BMW: ValveTronic!
...in service as usual :)
Audi, mechatronic Bi*ch
Diesel: fuel throttled
@@timothyball3144 btw i heard somewhere even some diesels still have something alike throttle body and it wasn't meant as intake flaps probably but im not really sure. Somebody knows something about it?
an0nim11 may be used for inducing some engine brake during the downhills.
Cable throttle people, remember to check cable tightness, like a bicycle brake, will stretch over time giving you crappy throttle responses.
Protune will eliminate rev hang if tuner knows what to look for.
cheers mate, I wasn't aware of this.
That's not what he's talking about. A cable throttle is more responsive than an electric throttle, even if the cable needs adjusted. A loose cable doesn't really effect response, anyway, unless it is so loose that something else is obstructing the cable. It just allows the pedal to "wobble" more (move without doing anything), and at 100% at the pedal the throttle body won't be, so it goes slower.
That all isn't a concern, because cable wear isn't a concern. A bicycle brake cable transfers a LOT of force, and unless the throttle is broken, but the throttle cable doesn't. It could, but it doesn't. It's "overkill", for the usual purpose, and that big to avoid bad problems. I just checked my 95 Jeep (with ~260k miles), it's still fine, and was never expected to be an issue, so the throttle cable is *not* adjustable.
Some throttle cables can be adjustable, but for different reasons, and most cars don't meet the requirements to need adjustment. My motorcycles' throttle cables can by adjusted, but with those I'm opening between 2 and 4 throttle plates instead of one, in a wet environment (carb vs fuel injected), idle adjustment is needed (carb vs efi), with less movement (twist grip vs pedal), so higher cable loads.
who uses mechanical brakes on a bicycle?
@@sultanabran1 everybody, I've never seen hydraulic brakes on a bicycle.
That's what I was wondering. It sounded like something experienced tuners would have the ability to get rid of it in software.
This explains a lot. When i went from driving manual in my Nissan 300zx to driving manual in a gen 4 eclipse the sensation of rev hang was so pronounced I literally thought the throttle pedal was sticking at points.
Thank you for your detailed explanation; it explains to me why I experience so much frustration with my vehicle (Jeep Wrangler jk 3.8L V6 with 6-speed manual trans) and throttle hang. A major safety issue with the electronic throttle body is that when I begin going down a long steep hill or mountain pass in third gear for example from a lower speed with my foot off the gas and the brake pedal, the vehicle will initially coast down in a gradual manner with the tradition engine braking effect safely controlling the descent and avoiding me overheating the wheel brakes.
However once engine speed increases to about 3000rpm or so as the vehicle's road speed picks up, the electronic throttle body will suddenly open up and "hang" as you described, causing the vehicle to suddenly surge forward with an increase in speed, forcing me to jam on the brakes in an emergency stop in order to avoid either hitting the car in front of me or (even more dangerous) suddenly speeding up into a steep bend that I'm using engine breaking to control.
i’m with you man. i have a jeep with the same engine and the 6 speed. the rev hang absolutely sucks. it seems like the longer i drive the worse the rev hang gets. sometimes when i go to shift the RPMs don’t go down at all. im worried that this causes premature wear on the clutch as well.