Yeap, FF is right on the money. Tray OFF especially if you are doing stop and go traffic, live in a very hot climate or running the car on the track.

 

One more reason that no one has yet mentioned.. it is almost impossible to get the rear of the car up on jack stands without jacking it up from the engine case. With the cover in place, you have no place to put your jack.

For dealerships that have a hoist, this shouldn't be a problem. For the average enthusiast, who works on their own car, the cover in place is a major PITA from a maintenance point of view.

 

Sorry, guys, but I have never understood the "protection" explanation. Porsche has had an exposed engine for over 3 decades on their air-cooled engines then suddenly we're supposed to buy the notion that the engine needs protecting? ...from what? And what about those scores of 914s, beetles, and buses that had their hapless engines exposed to the cruel environment for so long, oh the horror And exactly how many other cars had their engines "protected" with a full tray vs. the numbers with naked underbellies!
And the "aero reason" is similarly thin and unconvincing.

The bottom line is what one stands to gain with no tray vs what one stands to lose with it still mounted is enough to convince me.

Edward

 

thanks again guys - i didn't mean to start such a debate over the reasoning behind the trays, but i think i'll leave them both off for now. summer in KS is very hot and humid (90+ degree days with 90% or higher humidity) so it can't be helping - now if i can find the vaccum leak that's jacking with my a/c i'll be set

 

Let's look at these thoughts:

1) Yes, heat rises, but constriction of the airflow from underneath impedes the convective action. Also, the aerodynamics of the car and its wing are designed to draw air upward when in motion.

2) true, it is an extra layer of protection, but prior to the 964, all 911s were tray-less for 25 years. Debris were not a problem then and they are not a problem now.

3 & 4) true, again. Aircraft engines have some additional benefits that cars do not enjoy. First, they are always in motion. Stop and go is not an issue with a fixed wing aircraft. Second, the prop is a giant fan blowing air back into the cowl. Our cars do not enjoy the same benefits because they spend a lot of time at low speeds where the airflow is less than ideal. Also, the design criteria for aircraft versus cars are different. Due to those constraints our car's engine compartment is considerably more compacted than an aircraft. Aircraft do not have to go through a smog test.

Finn said it correctly. The under tray was an addition due to European noise laws. I think they measure engine noise and exhaust noises based on different standards. The under tray even had sound absorbent material on it.

The under tray probably does have an effect on aerodynamics, but it probably is almost unmeasurable. Certainly, the benefits of aerodynamics do not out weigh the benefits of cooling our cars.

Lastly, the 911 engine is cooled by convection (airflow) and conduction (oil flow). The heads are where the danger lies and they are cooled more by air than oil. Oil is used to regulate the temperature as well as lubricate. The cylinder head temperature will not always track the oil temperature.

Porsche will be mute on this because it is a government regulation and they can not legally recommend removing a regulated item from their cars.

However, what you do is your business and there are more advantages to removing the tray than keeping it on. Even if you do not buy into that statement, look at it from the reverse angle. The risk of removing it is essentially zero.

You have nothing to loose but heat.

Marv

 

its very very very very hot in TX in the summers....maybe i will try removing it for awhile and see if the difference is noticeable on my temp gauge...

wow, a very hotly debated topic...

 

ok, i want to take mine off, car i do it without jacking the car up and what tools do i need and what is the correct extraction process...does anybody have a lnk.....there are hundreds on this site and the first few threads do not contain any helpful info.....yes I am a novice when working on cars but intend to fix this over the coming years.......anybody in the DC area want to help me change my rotors and pads to make sure I do it right!!

 

i did it the easy way! i have a pair of Rhino Ramps from Auto Zone (the composite ramps) - they cost like $25 for the pair. i originally got them for changing the oil on my 944. i'm not sure you can drop the panel and pull it out from under the car unless you raise it because the panel goes up probably 10-12" on the sides into the engine compartment. the only tool you need is a phillips screwdriver. there are 4 or 5 half-turn phillips screws (1 on each side that are high up) and it just pops out. the one under the tranny has four half-turn phillips as well, then it has some tabs in the cross-member that just slide out. takes about 2 minutes once the car is in the air.

 

Yes, make sure the car is in the air before you attempt this...to put the tray back if the car is not jacked up is a PITA...ask me how I know...

https://rennlist.com/forums/993-forum/187638-just-did-something-stupid.html

 

You probably won't notice any difference in your oil temperature.

If, however you have a possibility to monitor your head temps, you might get different reading.

 

Actually it did when I was in Houston! Before the wisdom of RL I simply did not know and the tray was on... After I took it out I noticed my oil temps creeping up to 9 oclock only on very very hot days and with the tray off, when the car was in motion again the temps would go down faster than with the tray off. In a hote climate or on the track it does make a difference.

 

Yes Adrian is an expert. Be sure he is willing to pay your rebuild bill when the time comes before you listen to that advice...

 

Wow...the "tray" causes excessive heat indeed...you can tell by this thread's temperature! ;- )

Take care...

 

Yes, engine trays always a hot topic...get it...hot topic...oh, never mind

 

Mine dropped too after taking the tray off....

although its a tad up again since the dealer changed my oil from 15W-50 to 0W-40....engine oil consumption is drastically down though