nine64

My undertray is in a bad shape and start to coming loose..
should I replace it? or do I really need it?

John Boggiano

I'll go first...

Replace it!

(Depends somewhat on where you live, actually).

Andy Roe

Ok, I'll go second!

If you live somewhere very hot, take it off. Somewhere cold then leave it on. It's good at protecting the engine from salt etc in the winter.

Removing it will also reveal any oil leaks you may or may not have too & let them drip all over your drive!!

Johnny G Pipe

I've been pondering this sice I took mine off to G pipe the car.

A quick look at the archive suggests the clear reason for Porsche fitting an undertray - to give 964 owners something to argue about for years to come..

How about on for winter and off for summer? Or making a lightweight replacement? (they're pretty heavy, especially when soaked in Mobil 1..)

springer3

Any chance you can patch it up? I epoxyed a couple of broken places on mine, and so far it is holding together.

I say keep it on in any case. The adverse effect on engine temperature is a myth IMHO. Cooling air is ducted from the fan to the cylinders, heads, and oil cooler. The extra exposure for the underside of the engine is significant only when at speed, while most overheating problems are in traffic mostly at idle. In that case, the undertray can prevent recirculation of the hottest air, and may have slight benefit. There is probably some benefit from the under tray in winter, where it will slow the cooling rate for a warmed engine.

Bill Gregory

I'm in the take it off spring-summer-fall, and if you drive in winter, put it back on. You save some weight, and you provide for more air getting to the engine. If it served a sporting purpose, I would have expected the 964 Cup cars to run with the engine undertray on, and they didn't.

Our 3.6L engines are pretty much at the thermal limit for production air cooled engines (barring the limited run 3.8L models), and additional heat retained by the undertray and foil surround cladding can contribute to increased valve guide wear. That's one reason you won't see a 964 or 993 engine going 400,000 miles without a rebuild, as has been attributed to at least one 3.0L 911SC. Bruce Anderson has for years recommended on 993's that the undertray be removed to aid airflow around the engine, and given it's the same 'basic' design, I can appreciate removing the 964 undertray also. Recently, I read about one senior mechanic that thinks the seals on the valve stems may in fact work too well, contributing to valve guide wear.

Jacks911

A well respected Porsche specialist on the East side (Seattle) insisted on taking mine off even though we have moderate temps here all year round.
After reading many opinions on this, and knowing I would have far more opportunity to be stuck in traffic that to cruise at 140 mph, I agreed. I then got under the car and ripped out all the oily insulation. The other shields are still there but this engine runs very cool. If heat hurts, then I assume more cool is good?

But a question - ? is to cool any trouble? My car seldom gets above the second mark on the temp gauge - in traffic or at 70+ mph. Without leaving it sit at idle for many minutes it won't warm up enough to get a good read on oil level. Understand our normal day temps seldom get above 80 F.

Regards, Sweatless in Seattle, Jack

nine64

[QUOTE]Originally posted by springer3
[B]Any chance you can patch it up? I epoxyed a couple of broken places on mine, and so far it is holding together.

Springer3,
it's beyond help! been patch so many times don't have any more room to patch. Acually the whole thing is one big Patch.

Thanks for the reply everyone, but does it help protect the underside of the engine? come to think about it, the road where i live can be really rought sometime.

Does it help the air flow at hight speed or doesn't make a difference?

thanks

pete000

I just removed mine and I do not see any reason to put it back on. I do not drive in winter and the aero is not much a factor here in traffic laden LA CA. so I think it can live behind my shed in the back yard.

John Boggiano

FWIW, I once 'grounded' a friend's undertray whilst driving somewhat rapidly over a less than smooth surface. I'm glad it was the undertray and not the engine!

Arjan B.

All that I want to say about this is..........It is a hot discussed 964 issue. I did some testing last year in August in temprature data, with or without undertray.
Let me tell you this, withhas benefit's and without also, but I hope this discussion will not go as far as last year..........

I would replace it!

nine64

Thanks everyone
The undertray stay on and i will see if i can patch it some more if not order new one.

Arjan B.

Don't order the install set [speed nuts and screws] Those are from stainless steel and will cost a fortune at Porsche Parts........... Better look for a hardware store, probably 75 % cheaper then Porsche reckons.

nine64

Thanks Arjan! I will take a look.

Christer

nine64

There is no need to buy another one, there must be thousands lying left over at Porsche specialists all over the world, or hanging on someone's wall from people who have removed theirs. I did, and gave it away for free - if I still had it you could have just picked it up!

My vote: Don't bother.