Jean

Well I will give just another opinion here..

Just as a disclaimer, I don't run a tray in my car and I never felt it unstable at high speeds, then again I do have aerodynamic aids..

The 993GT2 EVO in the picture below is one of the fastest and most powerful cars to ever run at the Nordschlieffe, in the words of Manthey very recently.. It is an RS Tuning 720HP race engine (which are more like 900HP on a dyno) with multiple, aerodynamic improvements.. This car has a Kevlar plate underneath the car all the way back from the front spoiler to the exhaust + diffusers at the end, it is one built specifically for it in the wind tunnel. It must be there for a reason I guess. You cannot see it from the pictures unfortunately but I saw it fitted.

The 993 tray is not the same thing of course, however it might add stability at high speeds, I don't think it can be discarded without tangible proof. Race cars don't have a tray because they not often reach very high speeds (>180mph), they need all the cooling they can get, and they need easy access to mechanical parts. The tradeoffs are different.

Might be true then. The person answering the email from RUF is the father of Marc Lieb, he also knows a thing or two in racing.. (I cannot believe I am taking sides with RUF )

Bull

OK, that convinces me! Right next to my "Track Pack" pile of spares, etc. that I load up for track days, I'm starting another supply of items....for my "Bonneville Days Pack", which will first and foremost include the engine tray!

We all should have known that those crafty Porsche Engineers would be taking care of any customers who were inclined to run at Bonnevile! Oh wait, THIS time we aren't going to listen to the engineers at the factory....it is the aftermarket guys who know better.

long_beach_968

Factory always knows best! ...... sometimes

Edward

The fact that Ruf IS in europe only substantiates the position (no, it's not "my" position) that these trays are there for noise ...they want to actually sell their cars to people beyond the automotive press and must, oh, pass regs just like the other guys. Now doesn't that make sound, economic sense? At the very least, it hints in part to their position.

And don't get me wrong, stability trumps engine heat, but just when are the masses going to be hitting anything clsoe to top speed ...maybe in europe, and even then how often? Weigh this with the greater liklihood that you're trapped on the 405 fwy (or a London, Paris, Stockholm equivalent), and that precious tray that is "designed for stability" is trapping all that luscious warmth comfortably in your engine bay ...cozy, isn't it? And just how much of this instability has been reported over the valve-guide issues most often attributed by the pros to heat retention? Yes, the horse is dead. Long live the horse.


Edward

ca993twin

Does anybody remember a thread on this forum (I think) where somebody tested cylinder head temps with and without the undercover? Please post a link... I'd like to review that data again.

Bull

And you won't find a cover on many of the factory Turbos either.....

BTW, if you have been inspired to go forth and test the aero advantages provided by this piece of plastic, I believe that you will find this product to be required:

http://kalecoauto.com/index.php?main...&products_id=4

chris walrod

Well it just so happens we do have a rolling road wind tunnel with plenty of time available for rent. Group buy

Only caveat is that we would need to build a 45% scale model..

pcar964

I don't buy it. Ask me how I know...

Allen

Personally, I don't really see a disagreement here. Most agree that the higher the speed, the more aero benefit...I've never doughted that. At lower speeds...the range that the vast majority of us are in 99.9% of the time...there is no aero benefit, but there is a cooling benefit. Also, I think most would agree (Mr. Ruf included) that the car is louder on the outside with the pan removed. Sooo...if you run high speed alot, or noise is an issue, leave it on. If you run regular speeds, and noise is not an issue...take it off. Mine remains off...

tj90

I think the proper argument is whether engine tray causes damage to the engine. I have not seen anyone present data that shows that engines prematurely wear with tray in place. Do you REALLY think that you are increasing wear of the heads if the head temp is 8C hotter at idle only??? I would argue - again based on data that I collected - that you are doing more damage idling your car on the freeway without the tray, instead of waiting to drive at times when you can coast along at 20 mph. Thats when you really see head temps climb!

Keep believing in your demogogues - sheeple!

Bull

"Demogogues"???? Is that as accurate as your "data I collected", or your assumptions? "idling your car on the freeway"...nope, none of that here, wouldn't live/drive in those conditions. You continue to believe what ever home brew you concoct...it is fine with me!

Terry Adams

I was an agnostic on this until my top end rebuild at 120K. My previous 3.2 had a rebuild at 116K, and valve guides were shot - smoke out the exhaust. But that car spent hours idling stuck in hot commuter traffic. This 993 goes for long trips- thousands of miles sometimes - so I was not surprised that the valve guides were only half worn. I read all there was about it here, and listened to 3 people with about 60 years of Porsche engine experience between them. It's off.

tj90

Bob - I wont attack or insult your intelligence - just show me your data! ... I thought so - just keep parroting what youve heard.

"Religion without science is blind" - Einstein

Terry - your findings are consistent with what Ive measured - idle will kill you (tray off or on). For those with the tray off and sitting on the 405 in 90 degree heat - good luck to you in believing that this mod will help your valve guides.

Coleman

I'm in with Terry.. All the mechanics whom have torn down west-coast engines I have spoken to have seen premature exhaust valve guide wear- there is a correlation to 964's and 993's with more wear on the exhaust guides whom have the tray in place in this climate and traffic conditions and a correlation to 964's and 993's with less wear on the exhaust guides whom have the tray removed in this climate and traffic conditions.. Now, I don't think that there is a databse with these results, but the simple fact that mechanics who are replacing the guides see this is enough data for me.. TJ, How many 993 & 964 engines have you rebuilt the heads on? I'm not bagging on you, I'm just wondering where you are getting your info from?

Coleman.

tj90

Coleman: I would not refute anything you are saying. I dont rebuild engines so I dont have a pool of data. But I would bet you a beer that if you measured the head temps you will come to the same conclusion I did when I instrumented my engine with thermocouple to determine temp differences. You can searxch on the thread, but there was NO MEASUREABLE DIFFERENCE in temperature of the heads while you are driving with the tray on or off. At idle, a tray may add ~5C of temp to the bottom of the engine with the tray on.

Honestly, I would be compelled to leave the tray off if I drove in stop-and-go traffic everyday - however, I dont (I probably would not own the car if I did).

What I think is BS is that while you are driving the engine is cooler without the tray. I think Porsche did a great job of ensuring air flow over the heads while you are driving.

I also believe that idling an engine - even a water pumper - would be considered severe duty and is hard on any engine.