vw type 1 vlog
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- čas přidán 31. 03. 2024
- sorry for the somewhat poor editing quality. lots of words in this one and i'm not a great speaker and was definitely not at my best in this one. the message i'm sending is there though. you will not make a significant change to head temperature by puking oil into the rocker box no matter how you do it.
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I've tried wrapping my head around more oil cooling the head by use of a spray bar. It seems a clever way to oil the springs but that's about it.
The oil jets I've seen in the case to hit the cylinder walls, that seems more beneficial. Maybe that is one you could break down in a video?
Another great video!
more oil mods coming. spray bars in the head could be useful for spot cooling as in direct the oil at the valve to guide interfaces and more specifically the 4 exhaust valves. everyone thinks that huge amounts of heat can be generally removed by generally spewing oil into the box instead of focusing on the head's major problems. they can thank bob for that.
I'm going to suggest that the exhaust port isn't overheating, as you would expect. If anything .. the heat is a beneficial requirement.
I believe the majority of the exhaust's "heat" is traded/exchanged with the Bernoulli effect (throat icing up / freezing) of the intake throats in the head, enabling a better/warmer intake vaporization. Otherwise, the intake throats in the heads would freeze over.
The heat generated in the head's exhaust ports ... is required by the head's intake ports.
And that heat is with great certainty... mandatory to enable and pre-heat the intake manifold, again to counter the Bernoulli effect.
And for evidence that the exhaust port's are not overly heating .. just look under the valve cover ... there is no more signs of oil being burnt at the exhaust port's area than at the intake port's area.
Aluminum is an amazingly fast conductor of heat.
If you have ever welded on a chunk of Aluminum .. you will see .. that by the time you get to a welding temperature on one end .. the other end is almost at the exact same temperature.
And I'm very certain that amazing heat conductivity is keeping the entire Aluminum head at almost one temperature, or at least as close as dam is to swearing. Maybe shoot the head after warm-up with a hand held temperature gun.
There also is a case to be made, that the exhaust port is also somewhat cooled by the cool air blowing across that huge aluminium heat-sink in the heat exchangers, which are almost a part of the head, except for a couple inches of pipe.
For me .. the oil is for lubrication, and as far as scavenging heat .. I'd put that on the very very low extreme, as vw never even attempted to direct any form of oil cooling in the rocker box. Evidence suggests that vw only had oil in the head for lubrication on their mind.
And as far as the exhaust valve guide getting hot ...
It's obviously not ever seen melting, suggesting that it's probably withing it's perfect range of operation.
Worst case scenario... it's certainly an easy access and easily replaced component.
If I observe anything .. the vw idling over dusty ground .. can kick up a fair bit of dust.
So, the amount of air exiting the fan shroud, and blowing over the head .. is more than sufficient to cool the aluminum head's fins and sufficient to cool the exhaust contained exhaust ports. The heads are truly air cooled, and thinking the head's are oil cooled to any degree ... is just not imaginable .. when you consider the amount, speed, and force of cooling air blowing over and around the head's.. compared to the miniscule amount of oil flowing through the heads.
Imho
aluminum is a rather remarkable material. keep in mind that a lot of the viewers of these vids are flying vw people. they push their engines harder than we car and bus people do. they have premature wear with their exhaust guides as a result of too much heat. they also have good ol' bob with his promises of miracle cures through hvx mods based on false physics. one other thing keep in mind that reciprocating motions like rocker arms and wrist pins can't be lubricated. the back and forth movement and high pressure prevents the formation of a fluid dynamic oil film. the oil at these places acts as a spot coolant, not a lubricant.
Great job breaking down this important subject - Thanks Scotty! I was hoping that oil spray could help reduce the localized heat islands around the exhaust valves that I read are the Achilles heal of VW head longevity - but your outline of heat transfer issues cools my interest in oil spray. What do you think about ceramic coating of the valve faces, combustion chamber and exhaust port? I haven't found any good real world data.
imho there is only one magic bullet for power and efficiency. compression. i've read some technical papers that show that coatings in the combustion chamber create hot spots within the coatings themselves causing knock. the fix is lower the compression or remove the coating. your choice. thermal barriers inside the exhaust port would perhaps work.
Just a collateral knowledge share about engine oil cooling vs air cooling.
I know, this is vid about oil cooling the heads.
A friend of mine has two temperature sensors, one at the front Oil pressure control valve,
and one at the rear pressure relief valve.
He says that while driving on the highway that he sees a 25' F temperature differential between the front and rear of the engine case.
Considering that is about 1/4 of the mass of the engine case, and the bulk of the hot oil flows over that area, that would be a considerable amount of oil cooling.
Thanks Scottie,
that's a great video, and I really appreciate your depth of research, on all your videos.
If I have any thoughts of oil cooling the heads, I'd say it's very small, in the ratio to air cooling.
The pushrod's oiling ports are small and muffled by the rocker-arm cup.
While the heat from the exhaust ports and the flame propagating under maximum compression, are large in comparison.
The rocker-box is not really much of an oil reservoir, giving very little time or volume for heat adsorption.
I'd say that the oil in the head is primarily for lubrication.
While heat picked-up by the oil in the head, is probably cooled/lost as it flows down through the 8 pushrod tubes, as they are in the path of the fan's output.
So, the rocker's oil supply is probably not a major contribution to head cooling via cast off rocker oil.
As far as heat build-up in the head from the exhaust flow exiting the heads via the exhaust ports, id like to suggest that the exhaust port is very short, and a very small part of the mass of the head. It's also cast as a bit of an island onto itself.
Almost left to fend for itself, and is obviously very air cooled, yet still a head heat contributer.
I believe the bulk of the heat in the head is a result of compression and the ignition flame propagating.
At the end of the day, I personally believe that the ratio of oil flowing through the heads is very very minor to the amount and volume of heat generated in the head from compression, ignition, and the exiting exhaust gasses.
Basically .. there just isn't enough oil volume flowing in the rocker-box to suggest it has any significance to cooling the heads of scavenged heat.
Bob H was off by a mile, and probably why he posted no evidence of such, to back up his statement.
Imho
Cheers
@@thestove2407 that's a good data point. you should think about that a bit more though. homework for the two of you.
@@thestove2407 "I'd say that the oil in the head is primarily for lubrication." try door number 2 - cooling. the rocker arm interface is metal on metal contact. can't be lubricated. too much force/pressure and reciprocating rather than rotating motion. i think i mention this in one of the hvx mod vids.
yah air is your friend iol is for sliding and rubbing.
yup. pretty simple concept.
Good day Scotty
I remember your math indicating the lifter area had some of the highest pressures generated in the vw engine.
Question:
Do you think drilling the pushrod tube's oilling-port a little bit larger at the lifter end .... could possibly (significantly) increase pressure and flow through the pushrod ?
I'm thinking along the lines of a garden hose with a spray nozzle at the user end. So, if the house-end's valve is only half open, it severely restricts performance at the sprayer nozzle end.
So, if the house valve is 100% open, the spray nozzle end can enjoy higher pressure, and perhaps increase both pressure and flow at the rocker-arm / rocker-shaft interface.
And, depending on the rocker's side-play shim spacing, (using a .002" gap) perhaps significantly increase the psi pressure between the rocker and rocker shaft.
I wouldn't open both ends of the pushrod, as that could detrimentally decrease the oil-pressure in the lifter bore.
if i really wanted as much pressure as i could get at the rocker/rocker shaft, i'd radius the inside the pushrod ends of the pushrod tips. what kills pressure is flow around sharp bends not flow through a smooth gallery. it's the bend inside the rocker arm that is going to get you.