Joe S.

From reading past posts the consensus is generally positive for removing the engine tray, better cooling & ability to catch oil leaks early. Are there any cons, such as negative aerodynamic effect for removing the engine tray? The reason I ask is I was watching a show the other night on the development of the new Ford GT, they were getting lifting or handling issues at high speeds, so they did some modifications underneath the car near the rear end for a fix. Just wondering if removing the engine tray would have a negative effect on the handling ground effects at high speed similar to this since the rest of the underneath of the car is covered until you get to the engine area with the tray removed, mind you this is a purely uneducated guess. Any opinions?

Novice

my $0.02

If you stuck in traffic a lot, remove it for better ventilation by convection.

On the other hand the air scoop toward the front of the tray probably is better in directing/piping cooler air thru the engine bay.

I have mine remove now, but am thinking of drilling 2”+ diameter holes toward the rear of the trade to get the best of both worlds

There are other factors to consider: weight, sounds, easier access, road debris ...etc

993tt

Does anyone have numbers on this mod? I keep hearing about this but at the same time I'm having a hard time beliving that Porsche would do something that stupid if it really meant the car would suffer in extreme conditions.

The fan sucks air from the top and pushes it out under the car, right? I guess strange things could happen with the airflow if you remove the undertray and go cruising 120MPH down the autobahn. Not to mention the abuse the engine have to take from all the gravel, asphalt and dirt!

I won't remove mine until someone proves that it will make a significant differens.

Just my thoughts...

Mark in Baltimore

Ever heard of rubber centered clutches that mimic hand grenades? How about head studs that actively sought divorce from their familial environment? Body corrosion that was so bad you could actually hear the metal flake away in your garage? For the newer cars, there's always the rear main seal.

Although Porsche makes fantastic cars, the company has not always been flawless in engineering or decisions, with many choices that were selected due to cost or regulatory issues. The engine cover was allegedly designed to help the 964/993 pass strict European sound regs.

Anyway, about a year ago, someone on the 964 board did an experiment, albeit uncontrolled and not empirically correct, where engine temps were measured with and without the engine tray. Do a search (it probably has a zillion responses in it) and reach your own conclusions.

I vote "off", as does Steve Weiner and many others.

Greg Fishman

The oil temps may not change but the heads will get more air and therefore extend the life of the engine components such as valves, and valve guides.

Rocks or other debris has never been an issue for me on my race or street cars. If you travel a lot of gravel roads, I would suggest a different car...

STLPCA

Mine goes on/off with my winter tires. From my research, the general consensus of experienced Porsche mechanics, based on empirical data, is that the tray contributes to excessive heat which reduces engine component/gasket longevity. That convinced me. What others choose to do is, of course, their decision.

swftiii

Off...

I've had mine off and at over 120 on the track my butt end has not been lifting and trying to fly, so I wouldn't say the aerodynamics are affected.

As for rocks and gravel - no probs here, but I don't usually try to go off roading.

To each his own, but most folks that are knowledgeable and understand what impacts the life of the 993/964 engines run with theirs off. Many say that operating oil temps won't be affected, but I believe mine runs a little cooler now and with the oil cooler fan override, I can really keep the engine temps down in the basement.

-Skip

Edward

I've never understood the "protects the engine from debris" argument. Porsche has never seen the need to "protect" via a cover any of their engines prior to the 964 (don't think so, anyway) so how can one say that our engines are now "exposed" to abuse or grime ....ALL engines are! Moreover, 911s have been thus exposed for decades and with no ill effects. No disrespect to those who believe such; I just don't follow the logic.

Edward

jford

Edward,
Read Kims post earlier in the thread. Regardless of the fact that 911 engines have been exposed for decades along with other car makers engines there can really be no argument that the tray offers some protection. The fact is the tray covers the engine therefore it does offer some degree of protection. Whether or not the protection offered outweighs the benefits of removing the tray is certainly a worthy subject of debate. My tray comes on and off depending on the weather and where I will be driving. It only takes a minute and if I think I will encounter bad weather the tray stays on. When its hot or I am at the track the tray is definatly off. No flame intended just my 2 cents.

Jamie

viperbob

Kim's issue was really that the transmission cover was off as that is where the debris hit his oil line. But same difference. I choose to leave mine off, and I recommend that my customers do the same. There is no benefit that I can see, except if you like the reflecting material on the inside reflecting the heat of the motor back towards the engine. Dirt and grime will find their way into the engine either way. When I do work on someones car, it is always interesting to drop this cover and see how much rock and debris has accumulated inside...

Joe S.

I took mine off last night. I could probably fill some pot holes with the asphalt that was trapped in it...

Ray Calvo

They had these under-engine trays in place in some Carreras in the '80's as well. Back then Porsche was honest and said they were installed in cars destined for Switzerland to cut down on ambient noise. With increased number of Greenpeace numnuts worldwide, Porsche had to expand the use of this undertray (my thoughts).

Car is very stable on back straight at Mid-Ohio and Watkins Glen at 140 MPH without this piece of junk in place. I left the tranny unit in place.

Edward

Jamie,

Yeah, I hear you! Coincidentlly, I was with Kim when he nailed that exhaust tip. I remember seeing and avoiding it; Kim had the misfortune of being right behind the car that lost it

But think about it. If, as you say, you take off the trays for the track, this is precisely where you are more likely to experience road abuse, especially if you go "off roading." On regular streets, however, the likelihood of something coming up and biting the undercarriage is diminished (of course now that I said that, others will share how crap came falling off the truck in front of them and damaged their car...gimme a break, I'm speculating here ). Ironically, I chomped up the rear edge of my tranny tray when I went off at Buttonwillow. Perhaps I would have avoided damage altogether if the tray weren't there?...who knows. Thus, I'd just as well leave the engine tray off and have kept the tranny one on as I haven't heard of anyone mentioning any heat-related ills with this one. Like you, all just my 2 cents.


Edward

roebedo

Off...

Just seams to make more sense. Also I've read more topics about advantages to remove, rather to leave on.

Feehliks

I guess, in Arizona the perspective of better cooling prevails.

All 996 don't have this cover anymore - for whatever reason, I don't know. I have learned from the Porsche Service Shop, that this missing cover presents an issue, if the car is driven hard in winter. The salt on the road attacks the aluminum-engine. The mechanic assured me that this is not an issue with 993s, due to this cover.

The cover was begun with in the 964 as part of a program to improve the aerodynamics of the car. As the rear cover has an upward slope towards the rear, it helps to reduce uplift at high speeds. With the 993, this upward slope could not be continued with, as the new exhaust demanded more space. Anyway, at American highways, the aerodynamcis shouldn't present an issue.

@Joe S.
That looks suspicious. Your cover should be clean inside, as it is taken off each oil change.

Best regards,

Felix