Why I think removing engine tray is no good....
04-13-2006, 06:16 PM
#76
Three Wheelin'
Thread Starter
rkass - Im glad that you and others found this useful - I certainly did. I started this because I did not want to knowingly shorten engine life by driving around with the tray.
You should also thank JasonAndreas who is obviously very knowledgeable on this topic. Im a schmuck with a DMM, he provided much background information - patents, race history - to refute the Swiss noise law and Cup Car reasonings that we keep hearing about.
Im glad that the partcipants on the forum create an environment to debate these sorts or things. We can all have a "virtual beer" and still be all friends even though we disagree.
You should also thank JasonAndreas who is obviously very knowledgeable on this topic. Im a schmuck with a DMM, he provided much background information - patents, race history - to refute the Swiss noise law and Cup Car reasonings that we keep hearing about.
Im glad that the partcipants on the forum create an environment to debate these sorts or things. We can all have a "virtual beer" and still be all friends even though we disagree.
04-13-2006, 06:17 PM
#77
Three Wheelin'
Thread Starter
rkass - Im glad that you and others found this useful - I certainly did. I started this because I did not want to knowingly shorten engine life by driving around with the tray.
You should also thank JasonAndreas who is obviously very knowledgeable and educated on this topic. Im a schmuck with a DMM, he provided much background information - patents, race history - to refute the Swiss noise law and Cup Car reasonings that we keep hearing about.
Im glad that the partcipants on the forum create an environment to debate these sorts or things. We can all have a "virtual beer" and still be all friends even though we disagree.
You should also thank JasonAndreas who is obviously very knowledgeable and educated on this topic. Im a schmuck with a DMM, he provided much background information - patents, race history - to refute the Swiss noise law and Cup Car reasonings that we keep hearing about.
Im glad that the partcipants on the forum create an environment to debate these sorts or things. We can all have a "virtual beer" and still be all friends even though we disagree.
04-14-2006, 10:29 AM
#78
Great job on this thread. 
Your findings are not inconsistant with I have been told by three different Porsche Mechanics I have known for years. Cars in So Cal that sit in traffic a lot should really remove the cover. The cars that are in their shops with worn valves (mainly exhaust) and collapsed lifters and CEL issues are almost always cars with the cover in place. So I think the conclusions you have drawn are accurate in that Porsche made the cover Aerodynamic and used it to clean up the bottom of the car and improve perfomance at speed (A 94 Issue of Excellence Magazine makes this claim as well). As an engineer I always try to get a design to do more than one thing if I can. That is why I would not be suprised if the cover has a "secondary" purpose related to sound regs in Europe.
Since I am one of those So Cal drivers I have removed it. I also like the accessabilty I have to the engine with it removed (I'm sure that is why racing teams remove it). Anyhow good job!!!
Your findings are not inconsistant with I have been told by three different Porsche Mechanics I have known for years. Cars in So Cal that sit in traffic a lot should really remove the cover. The cars that are in their shops with worn valves (mainly exhaust) and collapsed lifters and CEL issues are almost always cars with the cover in place. So I think the conclusions you have drawn are accurate in that Porsche made the cover Aerodynamic and used it to clean up the bottom of the car and improve perfomance at speed (A 94 Issue of Excellence Magazine makes this claim as well). As an engineer I always try to get a design to do more than one thing if I can. That is why I would not be suprised if the cover has a "secondary" purpose related to sound regs in Europe.
Since I am one of those So Cal drivers I have removed it. I also like the accessabilty I have to the engine with it removed (I'm sure that is why racing teams remove it). Anyhow good job!!!
02-13-2007, 12:12 PM
#80
Rennlist Member
Originally Posted by ZombiePorsche44
<snip>
We will never agree and could do this till 2009 and still never really know the "TRUTH", if there is any. And even if we did, what would it really matter?
As for me, I'm just going to drive my car without the tray and not worry about it..............ZP44
We will never agree and could do this till 2009 and still never really know the "TRUTH", if there is any. And even if we did, what would it really matter?
As for me, I'm just going to drive my car without the tray and not worry about it..............ZP44
Does truth ever matter?
Usually, but often the path we travel in search of "truth" is quite interesting and well worth the effort.
As a newbie, i'm reading old threads and find this to be one of the most interesting I've come across.
Lottsa Science, some emotion, large doses of passion.
Most Excellent.
Maybe the trays should be manufactured out of a nearly perfectly conductve material (perhaps lead or gold) and left ON.
That would have the bonus affect of lowering the center of gravity.
Thanks
Craig
Last edited by cgfen; 02-13-2007 at 12:13 PM. Reason: typo
02-13-2007, 01:09 PM
#81
Burning Brakes
Originally Posted by tj90
Before you flame me - I did do a Rennlist search and other web resources and found that EVERYONE recommends removing engine tray. After a year of ownership, I did for this past weekend track day at Willow Springs. What I found is that oil temps were not any cooler and maybe a little higher. I know there are 100s of factors that dictate oil temp, but I did not see any improvement...
Sitting in the paddock, i thought about this harder and convinced myself that no engine tray may be bad. Heres why:
1) The engine tray keeps airflow under the car from upsetting the balance and flow of the fan in front of the alternator. Think about it, If I have an 80 mph wind blowing against the fan, I am creating eddys and potential hot areas of the engine for proper heat transfer.
2) There are 2 hot air ducts that route below the engine and out the outlets of the engine tray. Keeping the tray on keeps the hot air from entering the engine compartment. Kinda like insulating your air intake on a conventional car.
I am an engineer and actually do CFD thermal transfer modelling for a living. I would love to model the engine, car and simulate air flows to be data driven instead of asking others their opinion. You could imagine the amount of time, energy this would take outside my job so it wont be happening.
For now, I have to trust Porsche that they did this modelling and empirical analysis so my tray will be going back on... I just dont want to upset the manufacturers intentions on how airflow is supposed to move anound the engine. Think about the cooling fan. Im sure Dietrich in Germany slaved on the proper fan design for adequate airflows... My '95 motor has 100k miles and I assume that the engine tray has been on from day one.
What do you all think? I would think that an AUX oil cooler would do more for engine life that removing a cover...
Sitting in the paddock, i thought about this harder and convinced myself that no engine tray may be bad. Heres why:
1) The engine tray keeps airflow under the car from upsetting the balance and flow of the fan in front of the alternator. Think about it, If I have an 80 mph wind blowing against the fan, I am creating eddys and potential hot areas of the engine for proper heat transfer.
2) There are 2 hot air ducts that route below the engine and out the outlets of the engine tray. Keeping the tray on keeps the hot air from entering the engine compartment. Kinda like insulating your air intake on a conventional car.
I am an engineer and actually do CFD thermal transfer modelling for a living. I would love to model the engine, car and simulate air flows to be data driven instead of asking others their opinion. You could imagine the amount of time, energy this would take outside my job so it wont be happening.
For now, I have to trust Porsche that they did this modelling and empirical analysis so my tray will be going back on... I just dont want to upset the manufacturers intentions on how airflow is supposed to move anound the engine. Think about the cooling fan. Im sure Dietrich in Germany slaved on the proper fan design for adequate airflows... My '95 motor has 100k miles and I assume that the engine tray has been on from day one.
What do you all think? I would think that an AUX oil cooler would do more for engine life that removing a cover...
02-13-2007, 01:31 PM
#83
Technical Guru
Rennlist Member
Rennlist Member
I will paraphrase what I've been told since my last post in this thread.
- Michael Preiss designed the undertray for aerodynamic improvements.
- Other engineers in another department took the undertray and added the padding to comply with Swiss transmission/engine noise regulations.
- The sealed underside allowed Porsche to offer the 10 year/long life guarantee because the sealed panels were supposed to reduce corrosion problems.
- It was originally going to be fitted to the Swiss 964 but because of the expense and engine protection they decided to add it to all type 964, speading the cost out.
- The primary function of the side panels is for shielding the lower ignition wires and connectors from heat radiated by the catalytic converter and mufflers. Padding was added for the same reason as mentioned above.
02-13-2007, 02:55 PM
#84
Three Wheelin'
Thread Starter
jasonAndreas - thanks again for your summary - I did not consider the thermal radiation of the mufflers to the ignition wires. The exhaust is the hottest part of the car - seems to make sense to shield it from rubber components (ignition wire etc). Also, Interesting to note that the cat is outside the tray in the rear - probably for the same reason...
Tray on or off - dont extend your idling and avoid traffic at all costs if you are concerned with engine life. Dont kid yourself that taking a tray off and idling around in traffic is "lengthening" the life of your motor. The temperatures in the engine climb dramatically - tray on or off - with no forced airflow from driving around.
Tray on or off - dont extend your idling and avoid traffic at all costs if you are concerned with engine life. Dont kid yourself that taking a tray off and idling around in traffic is "lengthening" the life of your motor. The temperatures in the engine climb dramatically - tray on or off - with no forced airflow from driving around.
02-14-2007, 03:28 PM
#85
Instructor
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Excellent thread. Txs tj90 for the time and thourough approach. I did a mid way on mine. Its clear that long idling is a bad idea on an air cooled engine. And its possible that the tray may increase heat somewhat. I open the spoiler in these conditions (odd that nobody mentioned the manual oil cooler fan override). I also use synthetic oil.
I keep my tray on for several reasons: aerodynamics, protection (I would really hate a bolt or stone damaging my block!) and neatness. If you hoist the car you have to admire the smooth underside of it. I also cut two intakes on the front lip of the tray in line with the exhausts manifolds/exchangers so as to direct underside rushing air into them. I reckon if these run cooler while in motion, I buy some extra time at idle by starting with a lower temp.
And as far as who 'won', I think we all did.
Txs again.
I keep my tray on for several reasons: aerodynamics, protection (I would really hate a bolt or stone damaging my block!) and neatness. If you hoist the car you have to admire the smooth underside of it. I also cut two intakes on the front lip of the tray in line with the exhausts manifolds/exchangers so as to direct underside rushing air into them. I reckon if these run cooler while in motion, I buy some extra time at idle by starting with a lower temp.
And as far as who 'won', I think we all did.
Txs again.
03-22-2019, 05:21 PM
#88
Rennlist Member
Anyone remove the tray covering the trans? I have mine on, but may take it off this spring when I get the oil changed. I liked having it on when I drove in the winter- but haven't done that for 2 years.
03-22-2019, 10:06 PM
#89
RL Community Team
Rennlist Member
Rennlist Member
- Protects the oil return tubes and heater flap valve housings on the bottom of the engine from debris impact damage, my personal experience not using the tray
- Keeps minor oil leaks from messing up your garage floor
- Avoids setting piles of leaves on fire if you happen back over them, Personal experience w/o the tray
- May provide additional protection to the bottom of rear bumper cover from grounding as the tray probably will hit the ground first
- Pain in the *** to remove and replace it for every oil changes and other engine servicing
- Pain in the *** when putting the car up on jack stands for rear wheel removal
- Common sense says removing the tray improves cooling, although this can be debated.
- Hides oil leaks
