Kevin

I'm going to chime in and say that I support taking the under trays off. It's amazing to see how much heat builds up in the exhaust system and cat. Also, by removing the tray it might help relieve the static pressure from the cooling fan, which will help more air flow across the cylinders and heads.

Cupcar

My understanding is that the 964 Carrera Cup series cars did not run the engine cover pan. I suspect if there was a significant difference in handling or safty due to aerodynamic reasons the pans would have been left on.

964Cab

I took off not only the engine tray but also those tin engine cradle panels that foul one's access to the plugs and valve lash adj.

Patrick

GeoC2cab

High
Thom, I do believe for the mass air flow engine tray u will need to update ur cars body to the correct style, 90-94. I am surprised that K&N made one for a 1977 body.

Bill Wagner

If I'm not mistaken, the idea to pull the pans originated in the days of the ungasketted heads when mechanics were trying to figure out why some of the heads were having problems leaking. They made the assumption it was heat related and that removing the pans would assist in reducing the chance of the problems from occurring. Bruce Anderson has mentioned this, but I've never seen him (but I haven't read everything of his) say this was a requirement, and I think he attributed it to what other mechanics were telling him.

A good experiment might be to put a high temperature digital thermometer down near where the pan is and measure the temperature in that area with and without the pans (anyone out there brave enough to guess what the results would be??? ).

In the summer mine comes off, in the winter it goes back on. I don't drive at Autobahn speeds and there are no sound pollution requirements where I live to the best of my knowledge(even if there were, who would notice...the sound police???

Just my opinions,

Bill Wagner

Kevin

Bill;

The feared problem lies with the accelerated valve guide wear. The tray traps the airflow and act as an insulator.

Roland Kunz

Hello

Bin there allready, have T Shirt saying:

I´m sdupit
http://boards.rennlist.com/cgi-bin/9....pl?read=13710

Just ask any 944 Turbo driver on the race track if he removed the underpan to gain better cooling and handling and if the guy knows how to drive he will tell you a nice story.
Ask a Ferrari 355 owner why he didn´t removed the underpan for better cooling and better handling and he will tell you that you miss some screws.

Ask youself why several years ago Mercedes race cars airborned in Le Mans while the Porsche GT1 racer didn´t had problems ?
( not that GT1´s didn´t airborned too )
Ups maybe Mercedes removed the underpan to gain better cooling and aerodynamics ?

Porsche sure knows aerodynamics they paid a very high price by loosing some from the best fellows in races ( Bellof/Winkelhock ).

Grüsse

Adrian

Dear Roland,
Great response.
To J. Richard. We have a different exhaust system installed on our Swiss 964s. In fact all Swiss Porsches from 1976 have their own exhaust system as does everything else including aircraft. The 944 Turbo guys like them as compared to the ROW because the sound is much deeper. Quieter but drill the airbox and then see what is sounds like. No HP increase though.
Ask JD he can give you an explanation of the difference in sound between a US and Swiss 911, well using mine as a comparison anyway,
Ciao,
Adrian
911C4

Patrik S

My 964 Turbo 1991 does not have the engine cover pan! Did it have one when it left Porsche in 1991? And if the engine cover pan was never fitted on the Turbo was there any changes made to aid aerodynamic affects.
Is the Turbo in need of more air circulation to cool the turbo?

/Patrik

PeterH

Patrick,
I had the tin plate (3 panels costing about £500) replaced during my recent top-end as they were totally corroded. The specialist was adamant about them performing a vital function even though he was far more relaxed about leaving the undertray off. If you've taken these off, I'd get a professional opinion.
Rgds,
Peter C4

J richard

Roland,

Ask a Ferrari driver why he didn't remove his underpan? I doubt most ferrari drivers know what an underpan is let alone have the wrench to remove it..."Hey Jino, whhats he meen? I taek oof my underpan every nighte to wash ehm..."

Actually if you look at the rear end of a F355 I think you will get my point about aerodynamics. If you look under the Ferrari (or any LMP, SRP, F1, Carrera GT or current blend of GT cars) you will see a device known as a diffuser. It's purpose is to blend the flat underside of the car with the air flowing over the car to increase downforce and eliminate low pressure cavitation behind the car. This is the exact opposite of a flat bottomed back end.

If the underpan was a serious aerodynamic aid it much more attention would be paid to it's shape. In addition a diffuser must be stiff, most you will find are made of carbon fiber. The floppy thing hanging on my garage wall is semi rigid at best.

As far as the LMP cars becomming airborne the simple fact is that there was a hump in the road that allowed the angle of attack of the car to reach a point that it lost ground effect and became a very effective wing. Any LMP car at 180mph will become a aircraft if the front is lifted more than about 10". They have reworked that section of the track and shaved the hump down to eliminate this potential. I have a nice video of the Porsche doing a endover with all the underpan in place. I'll find the link and post it.

Anyway, Mine stays on the wall...

Regards

phil@tech9

Peter H,

The engine tinwork that you describe performs a very important function, that is ensuring that the cylinders receive adequate cooling.

These pieces should not be confused with the undertray.

On all 964 models it is very common for the rear tinwork, that is adjacent to cylinders 3 and 6 to corrode very badly, and disintegrate. If this is the case on anybodys car, I would recommend that it is replaced ASAP, to ensure that the rear cylinders to not run hot.

Adrian

Guys,
I agree with Phil on the engine cooling baffles. These also come loose and provide some of the strange noises people put to engine troubles.
The retention of the rear cover argument can go on forever. I have data from Porsche showing that it does serve an aerodynamic purpose. The covers are also optimised if sealed into place.
However retention or not, is as much an environmental and usage issue. If you live in cool or cold climes and drive in winter, leave it installed. If you are an owner who lives in the warmer climes, or does not drive the 964 in winter at all. Then maybe leave it off. There are other flavours as well such as heavy traffic usage etc.
A dry sumped engine needs to have the oil at operating temperature as soon as possible. Every assistance for this should be retained. If the weather or climate assists this action then remove it.
I would certainly leave it on if you have the opportunity for driving in excess of 125mph in cruise,
Ciao,
Adrian
911C4

PS: In winter I always cover my spoiler grill and the spoiler to try and reduce the cold soak of the engine. I also use 5W 30 Full Synthetic oil.

Danno1

Take screwdriver, remove screws, throw tray in trash. YOu would have to be pushing some serious speed to see the tray do any good. Do you want ot see my burnt exhaust valves due to the tray?

Jeff Curtis

964 Cab, while I am no professional...please put the tin side panels back on your engine. They are designed to reflect heat from your catalytic and secondary muffler away from the lower valve covers.

The exhaust valves on your engine already take quite a bit of heat, I dunno if the 3.6 has them, but I know the 3.0 engines in the SC had sodium filled valves for this purpose, they lasted quite a bit longer in heat.

If you look under your car, you will see that it is fairly obvious that they provide this function.

As for the lower tray issue, the first thing I did to my car was, uh, er, blow up the clutch...then I removed the undertray...and never put it back on.

To date, I have been to six track events, from Road America to VIR to Heartland Park, Roebling Roads and Summit Point...and my car has yet to take flight.

I think the real concern with these cars, while on track, is downforce. As I am becoming more comfortable with the car since purchasing and upgrading everything under the sun...the time has come to create downforce! Hence the addition of an RSA Tail (one piece, MA Shaw) and a front splitter (all the way across).

The electric "pop-up" wing creates pretty much ZILCH in the way of downforce.

I'm sure that last comment will create some conflict among the masses, but it's true.