Engine tray and high speed stability.
10-16-2006, 06:24 PM
#16
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Some of the latest engine tray/high speed stability threads -
https://rennlist.com/forums/showthre...ht=Engine+tray
https://rennlist.com/forums/showthre...ht=Engine+tray
https://rennlist.com/forums/showthre...ht=Engine+tray
https://rennlist.com/forums/showthre...ht=Engine+tray
10-16-2006, 06:26 PM
#17
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Originally Posted by mborkow
as i recall from the last time this came up the conclusions were that at street speeds the tray was not at all necessary and should be removed, but that for track speeds the tray did provide important aerodynamic properties.
10-16-2006, 06:30 PM
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Originally Posted by ZombiePorsche44
That was my quote and was not meant to be a gauge of all 993's at speed. It is mearly my experience in my car with the tray on & off while hauling *** in a straight line.
I can honestly say that with the tray off at 150+ it feels like the car is becoming rear end nervous and I really wouldn't want to try a big sweeper turn in that configuration due to distinct possibility I might have to look in the rearview mirror to see where I'm going and what I'm about to hit.
Now when I get my new suspension installed and the car lowered to the RS ride height I will do it again to see how it feels.
ZP44
I can honestly say that with the tray off at 150+ it feels like the car is becoming rear end nervous and I really wouldn't want to try a big sweeper turn in that configuration due to distinct possibility I might have to look in the rearview mirror to see where I'm going and what I'm about to hit.
Now when I get my new suspension installed and the car lowered to the RS ride height I will do it again to see how it feels.
ZP44
10-16-2006, 07:21 PM
#20
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Originally Posted by Bull
Never had that sensation myself in the past four years with this car at highspeed straights like VIR, nor on the banking and straights at Pocono.
10-16-2006, 07:43 PM
#21
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Originally Posted by LAT
This quote is from another thread, and I am wondering if anyone else has experienced this effect from removing the engine tray.
10-16-2006, 08:08 PM
#22
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OK, after reviewing the threads of the engine undertray, here's what we have postively determined to be true:
1). The engine tray was designed to reduce noise
2). The engine tray was designed to aid in aerodynamics
3). The engine tray was designed to keep crud out of the engine
4). The engine tray will cause excessive heat build-up
5). The engine tray does not make any appreciable difference in engine temps
6). The engine ray will assist in better cooling.
Pick one or more. Some of the above were derived from conversations with reputable sources. Some of the above were derived from actual testing. Some of the above are seat of the pants experience. Some of the above are conclusions drawn from very unscientific experiences (but many of them).
Some Porsche engineers said it was for noise. Ruf says its for aero. There's a Porsche patent that indicates aero. Some thermocouple experiments indicate no appreciable difference in temps. Some reputable mechanics seem to find a correlation with the tray leading to more valve jobs required. Some seat-of-the-pants indicate aero, other seat-of-the-pants say it matters not. Good heavens.
My very personal opinion is that if I were to take Rufus to high speeds, I'd want the undertray on. But its easier to jack the car and inspect for oil leaks with the tray off. My tray is off because I thought it was a good idea until I read the thermocouple experiment. Now I don't know anymore. I guess I'll leave it off because I'm basically a lazy turd.
1). The engine tray was designed to reduce noise
2). The engine tray was designed to aid in aerodynamics
3). The engine tray was designed to keep crud out of the engine
4). The engine tray will cause excessive heat build-up
5). The engine tray does not make any appreciable difference in engine temps
6). The engine ray will assist in better cooling.
Pick one or more. Some of the above were derived from conversations with reputable sources. Some of the above were derived from actual testing. Some of the above are seat of the pants experience. Some of the above are conclusions drawn from very unscientific experiences (but many of them).
Some Porsche engineers said it was for noise. Ruf says its for aero. There's a Porsche patent that indicates aero. Some thermocouple experiments indicate no appreciable difference in temps. Some reputable mechanics seem to find a correlation with the tray leading to more valve jobs required. Some seat-of-the-pants indicate aero, other seat-of-the-pants say it matters not. Good heavens.
My very personal opinion is that if I were to take Rufus to high speeds, I'd want the undertray on. But its easier to jack the car and inspect for oil leaks with the tray off. My tray is off because I thought it was a good idea until I read the thermocouple experiment. Now I don't know anymore. I guess I'll leave it off because I'm basically a lazy turd.
10-16-2006, 09:04 PM
#25
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I don't doubt that Bull's & Mark's car's feel good at 150+mph without an engine tray but keep in mind that there is a HUGE difference in driving a prepared (upgraded suspension) car like Bull's or Mark's on a nice smooth track with a roll cage, 6pt harnesses and hans, helmet & driving suit on VS driving a bone stock suspension US ride height 993 on BFG street tires, in your Levi's & baseball hat, on an interstate highway with wavey grooved superslab concrete for surface with everyone else going about 100mph slower.
I invite either of them to come drive my car here in the same configuration and see if they disagree with my experience.
ZP44
I invite either of them to come drive my car here in the same configuration and see if they disagree with my experience.
ZP44
10-16-2006, 09:10 PM
#26
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Lots of 993's on the track at Daytona this past weekend. Don't think I saw a single one of them with a rear tray on them. Most were at least doing 145mph.
10-16-2006, 09:17 PM
#27
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Originally Posted by ZombiePorsche44
I invite either of them to come drive my car here in the same configuration and see if they disagree with my experience.
Really?BTW, in addition to other times with the Motons and Sparco drving suit, those VIR top speeds were done with PSS-9's, jeans and a thin t-shirt. But, then again, I raced my 993 two weekends ago with a broken front swaybar and a TON of oversteer, so maybe my ability to judge is a bit less discerning than other's.
10-16-2006, 09:46 PM
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Originally Posted by ZombiePorsche44
I don't doubt that Bull's & Mark's car's feel good at 150+mph without an engine tray but keep in mind that there is a HUGE difference in driving a prepared (upgraded suspension) car like Bull's or Mark's on a nice smooth track with a roll cage, 6pt harnesses and hans, helmet & driving suit on VS driving a bone stock suspension US ride height 993 on BFG street tires, in your Levi's & baseball hat, on an interstate highway with wavey grooved superslab concrete for surface with everyone else going about 100mph slower.
I invite either of them to come drive my car here in the same configuration and see if they disagree with my experience.
ZP44
I invite either of them to come drive my car here in the same configuration and see if they disagree with my experience.
ZP44
Anyway, the only way to test this is to do a test on the same day, same conditions, same road, same direction....with the cover on and off...BUT, the driver not being told when it is on and when it is off. The driver will tell us when he "felt" it on and when he "felt" it off.
Any of the other anecdotal information we all offer up is interesting popcorn time though, including mine!
10-16-2006, 11:03 PM
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Originally Posted by ca993twin
OK, after reviewing the threads of the engine undertray, here's what we have postively determined to be true:
1). The engine tray was designed to reduce noise
2). The engine tray was designed to aid in aerodynamics
3). The engine tray was designed to keep crud out of the engine
4). The engine tray will cause excessive heat build-up
5). The engine tray does not make any appreciable difference in engine temps
6). The engine ray will assist in better cooling.
Pick one or more. Some of the above were derived from conversations with reputable sources. Some of the above were derived from actual testing. Some of the above are seat of the pants experience. Some of the above are conclusions drawn from very unscientific experiences (but many of them).
Some Porsche engineers said it was for noise. Ruf says its for aero. There's a Porsche patent that indicates aero. Some thermocouple experiments indicate no appreciable difference in temps. Some reputable mechanics seem to find a correlation with the tray leading to more valve jobs required. Some seat-of-the-pants indicate aero, other seat-of-the-pants say it matters not. Good heavens.
My very personal opinion is that if I were to take Rufus to high speeds, I'd want the undertray on. But its easier to jack the car and inspect for oil leaks with the tray off. My tray is off because I thought it was a good idea until I read the thermocouple experiment. Now I don't know anymore. I guess I'll leave it off because I'm basically a lazy turd.
1). The engine tray was designed to reduce noise
2). The engine tray was designed to aid in aerodynamics
3). The engine tray was designed to keep crud out of the engine
4). The engine tray will cause excessive heat build-up
5). The engine tray does not make any appreciable difference in engine temps
6). The engine ray will assist in better cooling.
Pick one or more. Some of the above were derived from conversations with reputable sources. Some of the above were derived from actual testing. Some of the above are seat of the pants experience. Some of the above are conclusions drawn from very unscientific experiences (but many of them).
Some Porsche engineers said it was for noise. Ruf says its for aero. There's a Porsche patent that indicates aero. Some thermocouple experiments indicate no appreciable difference in temps. Some reputable mechanics seem to find a correlation with the tray leading to more valve jobs required. Some seat-of-the-pants indicate aero, other seat-of-the-pants say it matters not. Good heavens.
My very personal opinion is that if I were to take Rufus to high speeds, I'd want the undertray on. But its easier to jack the car and inspect for oil leaks with the tray off. My tray is off because I thought it was a good idea until I read the thermocouple experiment. Now I don't know anymore. I guess I'll leave it off because I'm basically a lazy turd.
