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No worries on my end. Years ago, Porsche came out and said it was a noise thing, it was not me. In any case, I have taken them off of every 964 and 993 I have owned. That is why I have two for sale.
With all due respect, I believe comparing a stock 993 with a cup car is a bit apples and oranges. The cup car has additional aero that is proven to be effective at high speeds whereas a stock 993 (even the turbo aero) doesn't generate any meaningful net downforce. With the lack of cup car aero, a stock 993 will be much more sensitive to the presence of the engine undertray, or lack thereof. My car, with the GT2 front and rear aero, was ran without an engine tray for 14 + years with no high speed stability issues. I recently removed my gt2 wing but kept the front splitter and that made the car feel really aerodynamically imbalanced. I'm on the quest to restore some of that balance without having to remove the front gt2 splitters (3 piece version), and I think the engine undertray will be an important part of that equation now that the rear gt2 wing is gone. I'd love to hear your thoughts on this. I've been obsessing recently on how to improve the underbody airflow and thus increase high speed stability / downforce without resorting to a big wing. Any thoughts / advice is welcome. Thanks!
I have a few extras sitting on the side of my house. If I recall, one for a wide-body and one for a narrow body car. Maybe one for a 964. If anyone needs one in the Dallas area, come on over...
Could someone share with me the actual data that shows the cylinder head temperatures increase or decrease with the addition or removal of the undertray? Or show me communication to dealers to remove them.
The argument for reducing sound is flawed - if this was an attempt to make these cars quieter then the engineers failed.
The factory spent some effort engineering these trays in order to reduce lift at the rear, and that is how they referred to them, see here:
The yellow marked text translation is: the under engine reduces the rear lift force. In German they say rear axle lift force.
The title says measurements of achieved aerodynamic improvements, or aerodynamic resistance.
This has been discussed on rennlist many times before.
Anyway, put your trays back on folks. They're there for a good reason!
^i have never seen supporting data but have heard anecdotal references to this issue from the likes of Bruce Anderson so I am ok removing mine in case there is any chance of creating a temp issue. I am not driving on the autobahn so I doubt there is any noticeable aero difference. In their home country where you could fly down the autobahn it probably makes a difference. My SoCal bumper to bumper traffic is already an issue for heat and stops me from testing the aero at 100mph - I would rather take additional precautions even if anecdotal.
With all due respect, I believe comparing a stock 993 with a cup car is a bit apples and oranges. The cup car has additional aero that is proven to be effective at high speeds whereas a stock 993 (even the turbo aero) doesn't generate any meaningful net downforce. With the lack of cup car aero, a stock 993 will be much more sensitive to the presence of the engine undertray, or lack thereof. My car, with the GT2 front and rear aero, was ran without an engine tray for 14 + years with no high speed stability issues. I recently removed my gt2 wing but kept the front splitter and that made the car feel really aerodynamically imbalanced. I'm on the quest to restore some of that balance without having to remove the front gt2 splitters (3 piece version), and I think the engine undertray will be an important part of that equation now that the rear gt2 wing is gone. I'd love to hear your thoughts on this. I've been obsessing recently on how to improve the underbody airflow and thus increase high speed stability / downforce without resorting to a big wing. Any thoughts / advice is welcome. Thanks!
I would agree, but please explain the down force argument with a 964 Carrera Cup. There was no additional aero on these. They ran these with stock body panels and No fixed rear wing.
I have also owned one of these Carrera Cups. There was no under tray..
Furthermore, I have owned an raced several Porsche factory races cars back in the 90s, and none of them had a rear tray. . At the speeds these cars are going, I don't think the rear tray is helping aero that much, if any. I can also say with some confidence, that the street cars are going somewhat slower.
The front two sections, I would agree would be very important as they create a smooth flow of air.
I am not trying to support any argument here, I am using actual experience.
By the way, if you are really interested, there is a great article in 12/98 Panorama magazine in the technical section. It is titled "Porsche Aerodynamic Aids" written by Allan Caldwell. It discusses the body and the underbody of the car as it pertains to stability for the 911, 914 and 928.
I would agree, but please explain the down force argument with a 964 Carrera Cup. There was no additional aero on these. They ran these with stock body panels and No fixed rear wing.
I have also owned one of these Carrera Cups. There was no under tray..
Furthermore, I have owned an raced several Porsche factory races cars back in the 90s, and none of them had a rear tray. . At the speeds these cars are going, I don't think the rear tray is helping aero that much, if any. I can also say with some confidence, that the street cars are going somewhat slower.
The front two sections, I would agree would be very important as they create a smooth flow of air.
I am not trying to support any argument here, I am using actual experience.
By the way, if you are really interested, there is a great article in 12/98 Panorama magazine in the technical section. It is titled "Porsche Aerodynamic Aids" written by Allan Caldwell. It discusses the body and the underbody of the car as it pertains to stability for the 911, 914 and 928.
I didn't realize the 964 cup cars had no additional aero. Question, the Porsche factory race cars you raced in the 90's, did they have any additional aero?
Thanks for sharing your experience, and for the lead on the panorama article. I'll post a link if I find one to the article.
I had a Carrera Cup, which had no downforce, I also had 2 US Carrera Cup that were for the US series, no downforce. I raced these at Daytona at pretty highs speeds and didn't feel any instability in the rear.
I also had 2 993 Supercups and the 993 Champion Porsche GT2 car, and, none of these had the under tray. The 993s had a fixed wings and front down force.
They didn't start using the fixed wing/spoilers until the 993 Supercup and 993 Carrera Cup.
Finally, I had a 996 Supercup, and if I can remember, it didn't have under tray in the rear either.
Quote from Bruce Anderson, from Excellence magazine, Technical Notes II, page 118: "I have been recommending that the trays under the engine be removed because I feel they cause engines to run hot, which results in premature exhaust guide wear....I know of about 15 964 engines that have been torn down, including my own, and all have had valve guide wear that exceeds what Porsche specifies"
Bottom line, I could be wrong, but I can honestly say the undertary provided little or no downforce or stability to the back of the 911 and if anything, I would think it would help maintain heat.
I had a Carrera Cup, which had no downforce, I also had 2 US Carrera Cup that were for the US series, no downforce. I raced these at Daytona at pretty highs speeds and didn't feel any instability in the rear.
I also had 2 993 Supercups and the 993 Champion Porsche GT2 car, and, none of these had the under tray. The 993s had a fixed wings and front down force.
They didn't start using the fixed wing/spoilers until the 993 Supercup and 993 Carrera Cup.
Finally, I had a 996 Supercup, and if I can remember, it didn't have under tray in the rear either.
Quote from Bruce Anderson, from Excellence magazine, Technical Notes II, page 118: "I have been recommending that the trays under the engine be removed because I feel they cause engines to run hot, which results in premature exhaust guide wear....I know of about 15 964 engines that have been torn down, including my own, and all have had valve guide wear that exceeds what Porsche specifies"
Bottom line, I could be wrong, but I can honestly say the undertary provided little or no downforce or stability to the back of the 911 and if anything, I would think it would help maintain heat.
Thanks for your feedback and insight. Much appreciated!
RE Noise: yes, I recall reading in a Porsche book (Frere's book?...can't recall exactly) that it was Swiss regs and a few Euro countries where the then-new 993 was hitting their sound db limit during R&D. So Porsche added the cover to just nudge it down enough to make the mark. Sidenote: there are tracks around the country where db limits cause folks to do all kind of strange things to get "just under" the ceiling ...I've seen quite a few creative examples at Laguna Seca And so for homologation --as they didn't want to have market x have a this device but market y does not-- Porsche made the cover a standard item.
Think about it: you have to certify a car for sale so you create work-arounds just to get it out to market. The US cars have the "school bus" suspension to meet DOT bumper-height regs that none of the RoW cars face. So the engine cover was an easy fix for them ...and an easy "upgrade" for us
09-13-2018, 12:27 PM
And so for homologation --as they didn't want to have market x have a this device but market y does not-- Porsche made the cover a standard item.