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On an ‘87/‘88 auto with the 2.20 rear end average rpm is probably 2k or less. On an GT or GTS 5-speed average rpm is 3k or more and add-in engine braking. So the windage tray is more useful on 2.73 rear end 5-speeds than it is on 2.20 autos. In general.
Dave, I think I got the gist of the original question, but I did botch my response. Sorry. You are absolutely correct that a more frequent need could arise with a higher ratio rear end, but the original question took the 928 track driver out of the equation and focused instead on the street drivers. (is there any benefit to a GB windage tray set on a street driven 928 engine? More specifically on a 32V S3?)
Where can MOST people drive a 928 on the street that the speed or RPMs and the amount of time at those speeds or RPMs would actually warrant windage trays? The answer is usually pretty much nowhere.
But, if a driver wants windage trays, by all means these would be ones to get.
Dave, I think I got the gist of the original question, but I did botch my response. Sorry. You are absolutely correct that a more frequent need could arise with a higher ratio rear end, but the original question took the 928 track driver out of the equation and focused instead on the street drivers.
We're still not connecting here John. I haven't lost sight of Seth's context and what I posted was 'street pontification.' Here are some numbers in a street context:
S4 with a 2.20 rear end is turning roughly 2550 rpm on the highway at (a hypothetical, of course) 80 mph in 5th.
GT with a 2.73 rear end turns roughly 3200 rpm cruising at 80 mph in 5th.
A 928 with a 2.54 rear turns roughly 2950 at 80 mph in 5th.
Why is it that S4s with 2.20s use almost no oil(*) over a couple of thousand miles while GTs use a quart or two over the same distance? They have the exact same crank case breather setup yet the GTs eat oil like it's going out of style.
What's different? Average rpms. One might argue that the GT has a tad higher compression that might contribute.
The theory - my theory - is that the higher average rpm for GTs lead to - on average - more oil getting whipped into foam that fills the heads' oil returns thus making poor crank case ventilation worse when compared to an S4 w/2.20. And that is what 'helps' oil ingestion via the breather system.
If true, then the questions then become: Does a windage tray reduce or increase oil foam production? Are the effects non-linear with respect to rpm? (Or, in other words: does it do nothing useful below rpm X, reduce or increase from X to Y rpm, and increase or reduce foam after Y rpm? Or does it always reduce (or increase) oil foam production?)
I'm of the mind that a windage tray will reduce oil foam production at all rpms. Why? It seems logical and because Porsche put one in GTSs where that long crank throw gets the crank that much closer to the sump level. (Of course, a counterpoint is that that tray doesn't seem to 'work' on GTSs. On the other hand, we'd need someone to pull the tray from their GTS's pan and have them report back on oil consumption changes. Or, someone that put a GTS tray in a GT could report on oil consumption changes.)
(*) That's a generalization. No doubt there are some S4s that use oil and some GTs that don't, but in my experience, the generalization applies. It's also my experience that auto-transaxle 928s eat less oil than 5-speeds. And again, there, the difference is average rpm between autos and 5-speeds. I have no oil consumption 'data' for 2.54s, 2.63s. For whatever reason I seem to have clients with either 2.20s or 2.73s.
So...I have a silly, ne stupid question: is there any benefit to a GB windage tray set on a street driven 928 engine? More specifically on a 32V S3?
Dave, You have posted some great data in defense of your position and I agree with the points you make, BUT, don't S3s have a 2.20 rearend? And basically 70% of those manufactured are AT?
I appreciate your thoughts.
Last edited by soontobered84; 01-12-2020 at 10:18 AM.
Reason: highlight
We're still not connecting here John. I haven't lost sight of Seth's context and what I posted was 'street pontification.' Here are some numbers in a street context:
S4 with a 2.20 rear end is turning roughly 2550 rpm on the highway at (a hypothetical, of course) 80 mph in 5th.
GT with a 2.73 rear end turns roughly 3200 rpm cruising at 80 mph in 5th.
A 928 with a 2.54 rear turns roughly 2950 at 80 mph in 5th.
Why is it that S4s with 2.20s use almost no oil(*) over a couple of thousand miles while GTs use a quart or two over the same distance? They have the exact same crank case breather setup yet the GTs eat oil like it's going out of style.
What's different? Average rpms. One might argue that the GT has a tad higher compression that might contribute.
The theory - my theory - is that the higher average rpm for GTs lead to - on average - more oil getting whipped into foam that fills the heads' oil returns thus making poor crank case ventilation worse when compared to an S4 w/2.20. And that is what 'helps' oil ingestion via the breather system.
If true, then the questions then become: Does a windage tray reduce or increase oil foam production? Are the effects non-linear with respect to rpm? (Or, in other words: does it do nothing useful below rpm X, reduce or increase from X to Y rpm, and increase or reduce foam after Y rpm? Or does it always reduce (or increase) oil foam production?)
I'm of the mind that a windage tray will reduce oil foam production at all rpms. Why? It seems logical and because Porsche put one in GTSs where that long crank throw gets the crank that much closer to the sump level. (Of course, a counterpoint is that that tray doesn't seem to 'work' on GTSs. On the other hand, we'd need someone to pull the tray from their GTS's pan and have them report back on oil consumption changes. Or, someone that put a GTS tray in a GT could report on oil consumption changes.)
(*) That's a generalization. No doubt there are some S4s that use oil and some GTs that don't, but in my experience, the generalization applies. It's also my experience that auto-transaxle 928s eat less oil than 5-speeds. And again, there, the difference is average rpm between autos and 5-speeds. I have no oil consumption 'data' for 2.54s, 2.63s. For whatever reason I seem to have clients with either 2.20s or 2.73s.
Did you forget the GTS has missing oil drainback holes in its pistons?
That is the biggest appreciable difference in the engines and would explain the GTS' inordinate oil consumption.
Additionally, if no piston oil drainback holes was such a good idea, why is it the only engine on the planet which implemented it? And not-so coincidentally, it is an engine which consumes oil like a Model T with 500,000 miles - when brand new.
I think you think my use of “GTs” is intended to be the same as my use of “GTSs”. The former is the basis of comparison with S4s, whereas the latter was only used in a parenthetical off-handed remark.
The piston designer prescribes fully thru drilled drain holes when he thinks there is too much oil on the bore walls and reservoir holes that aren’t drilled thru when he thinks there is too little oil on the bore walls. Both are intentional designs.
There’s little to actual evidence on whether the various aftermarket windage trays help, hurt, or to nothing. One just has to go based on logic and published research. The one exception that I am aware of is Mike Simard testing his 7L 928 engine with and without windage screens and deciding to remove them after testing, but this was a dry-sumped engine.
Dave, I think I got the gist of the original question, but I did botch my response. Sorry. You are absolutely correct that a more frequent need could arise with a higher ratio rear end, but the original question took the 928 track driver out of the equation and focused instead on the street drivers. (is there any benefit to a GB windage tray set on a street driven 928 engine? More specifically on a 32V S3?)
Where can MOST people drive a 928 on the street that the speed or RPMs and the amount of time at those speeds or RPMs would actually warrant windage trays? The answer is usually pretty much nowhere.
But, if a driver wants windage trays, by all means these would be ones to get.
It is important to realize that I don't sell stuff to the general public, until I've proven it to work, here. I know where the trash can is...and many of my prototypes end up there.
If I sell something separately, it works alone. If it comes only in a "kit", you need the kit.
Your specific question about the S3 engine is a great one....not everyone understands the problems that S3 owners face.
The first time a person with an S3 engine removes the side plenums, of the intake, they understand one of the issues. These plenums gather up oil in "kitchen measuring cup" volumes. I've been working on these engines, for years, and to this day, I forget, tilt the plenums and ruin a shirt or a pair of shoes! From the intake, oil has only one place to go....into the combustion chamber, where it reduces the effective octane level of the fuel, and causes deposits, increasing engine knocking and reducing efficiency.
One of the very "best" improvements that one can do to the S3 engine is to reduce the amount of oil that gets to the combustion chamber. They run better, they run cleaner.
My windage trays do a great job keeping oil, that is spraying off of the crankshaft, from being "carried" around in the engine by the crankshaft. They further keep oil that does spray off the crankshaft from bouncing off the oil pan and getting picked back up by the crankshaft (rear of the engine). They also keep the oil in the "pick-up" area of the pan from being whipped up and carried around by the crankshaft (front of the engine).
The 928 engine has a built in "funnel" that pushes air and oil up into the filler neck area....which is immediately above the oil "pick-up". In the early 4.5 engines, Porsche put a screen over this area to keep oil from being picked up by the crankshaft. In the GTS engines, they install a metal plate to keep this from occurring. All the engines from '83 to '91 got nothing!
My windage trays are a fantastic addition to help with this problem.
If you can move the pan away from the crankshaft....any amount, this also helps.
Add in my filler neck oil baffle and what oil/air that gets tossed up into the filler neck area is further separated, before it makes it to the actual filler neck and into the intake.
Add in my valve cover oil separators and you've completed what you can do, without using a dedicated oil separator.
Oil in the intake plenums is will be reduced to being measured with the kitchen teaspoon set, instead of the kitchen measuring cup set.
And the great part, for everyone....the development/testing is already done! They all work independently, while complementing each other, when used together.
The piston designer prescribes fully thru drilled drain holes when he thinks there is too much oil on the bore walls and reservoir holes that aren’t drilled thru when he thinks there is too little oil on the bore walls. Both are intentional designs.
There’s little to actual evidence on whether the various aftermarket windage trays help, hurt, or to nothing. One just has to go based on logic and published research. The one exception that I am aware of is Mike Simard testing his 7L 928 engine with and without windage screens and deciding to remove them after testing, but this was a dry-sumped engine.
I would call pistons without oil return passages from the rings to the inside of the pistons an "experiment" that did not work. Very few engines contain this terrible "design".
If you take the time to show pistons to engineers at places that build custom pistons, they just stand there, with their mouths hanging open, unable to even talk. When they finally can speak, the very first thing that comes out of their mouths, 100% of the time, is, "Well, that won't work".
I've rebuilt literally dozens of GTS engines and have drilled the return oil holes in the pistons and left everything else stock. (I've even cleaned and reused the original rings several times, on low mileage engines.) Oil consumption, each and every time, goes from stupid high numbers to normal numbers. You can clean off the 1mm thick layer of super hard carbon off of the tops of the pistons and out of the combustion chambers and terrible pinging is eliminated. The engines run, much, much better....way more power.
It's the same old story...there's as many ideas about how to do things inside an internal combustion engine as one could ever dream up, in a lifetime.
Not all of those ideas are good...or work.
I would call pistons without oil return passages from the rings to the inside of the pistons an "experiment" that did not work. Very few engines contain this terrible "design".
If you take the time to show pistons to engineers at places that build custom pistons, they just stand there, with their mouths hanging open, unable to even talk. When they finally can speak, the very first thing that comes out of their mouths, 100% of the time, is, "Well, that won't work".
I've rebuilt literally dozens of GTS engines and have drilled the return oil holes in the pistons and left everything else stock. (I've even cleaned and reused the original rings several times, on low mileage engines.) Oil consumption, each and every time, goes from stupid high numbers to normal numbers. You can clean off the 1mm thick layer of super hard carbon off of the tops of the pistons and out of the combustion chambers and terrible pinging is eliminated. The engines run, much, much better....way more power.
It's the same old story...there's as many ideas about how to do things inside an internal combustion engine as one could ever dream up, in a lifetime.
Not all of those ideas are good...or work.
I think that the 928 engines have too much, not too little, oil on the bore walls. Therefore, the fully thru drilled drain hole design is better.
However, the decision to not drill the drain holes thru is not a manufacturing error, it’s a design decision by the engineering team. I just disagree with that design decision and we recently specified fully drilled holes to the new turbo piston catch we ordered.
I think you think my use of “GTs” is intended to be the same as my use of “GTSs”. The former is the basis of comparison with S4s, whereas the latter was only used in a parenthetical off-handed remark.
Unless you get new replacement .50mm oversize ones....they are undrilled, now.
Worked so badly on the GTS engines, they have apparently "backdated" the terrible engineering to cover more models, now....
I absolutely love that Porsche was replacing GTS engines, under warranty, for excessive oil consumption, and no one bothered to take one apart and figure out why!
I always try to remember that 50% of the mechanical engineers out there, finished in the lower half of their class.
Judging from the engineering "flubs" that they have had on almost every model, Porsche hires them, by the busload.
I think that the 928 engines have too much, not too little, oil on the bore walls. Therefore, the fully thru drilled drain hole design is better.
However, the decision to not drill the drain holes thru is not a manufacturing error, it’s a design decision by the engineering team. I just disagree with that design decision and we recently specified fully drilled holes to the new turbo piston catch we ordered.
Are you aware of an engine from another company that uses the undrilled design?
Dave, You have posted some great data in defense of your position and I agree with the points you make, BUT, don't S3s have a 2.20 rearend? And basically 70% of those manufactured are AT?
Looks like Greg weighed in on the S3 question. The few S3s I've worked on had ton's of oil - like Greg posted - in the intake plenums. So, oil ingestion isn't just an "S4 thing."
Porsche must have used the undrilled pistons for a very long time. I have a factory exchange S4 engine which I acquired as used defective in 2001. It has the undrilled pistons. I do not know when the engine first was sold to the original owner.
Åke
01-11-2020, 11:41 PM
