Just to clarify, removing your undertray will not affect the temperature of the oil in the engine or system in any way. It does arguably help the ambient temperatures in certain parts of the engine bay, especially as someone pointed out during idling.

Personally, I got rid of the undertray when I swapped out the standard exhaust - it won't fit any more anyway. No problems doing 140mph+ from an aerodynamic point of view. Undertray does hide oil drips though...

I guess it is just a personal thing and there is no conclusive answer.

 

Your insurance company will cover road damage under your comprehensive coverage. Damage occurring from excess heat build up will come from your pocket. Just some food for thought.

 

This has been extensively covered in the past, but yeah, what are the odds ? all 911s before the 964 (?) didn't have a tray. My 83 put 170K miles without a tray, my 1960s 356 has more miles than anybody knows and doesn't have a tray. Never had any issue with hitting anything... OTOH leaving it ON practically guarantees higher localized temps that will cause issues at some point. Which odds do you like better ? ;-)

 

How about drilling holes on the tray to allow some air circulation and still have the engine protected? even better protection, mount some metal wire mesh over the holes.

 

I took mine off ages ago; no problems with 76K miles on the car. Porsche sez it's on there for aerodynamic purposes, but they started adding them in 1987 on Euro cars to pass noise standards (Switzerland, as I remember). This was WRITTEN in one of their Tech Bulletins describing changes for the 1987 model year (used to have a copy). So, I feel that is the real reason they added them on these cars, NOT aerodynamics.

When the 964 came out, I think this was the first year the undertray was added to US cars. Caused some excessive heat on the exhaust head side of the engine, prematurely failed some exhaust valve guides as I remember. The 993 was much less of a problem as far as heat retention (Bruce Anderson's stance, who I consider the 911 gospel). Still after cursing taking it off to do my first 993 oil change I decided to leave it off.

 

I agree with 993 Power. The only way I could spot lower valve cover gasket leaks was with the tray removed. I've been trayless for 2 years with no problems however I think the temperature differences are negligible.

 

One thing to remember when mentioning temperatures is that the temp shown on the dash gauge and the actual temp at the exhaust valve guides are two different things. It’s quite possible to remove the engine cover and have lower temps at or near the exhaust valve guides, but have no change reported on the dash gauge.

If I recall, the sender for the dash gauge is on the top of the engine. The area around the exhaust valve guides is on the bottom of the engine. Removing the tray might very well let heat escape from the exhaust valves, but make no change to the temp sender on the top of the engine.

My tray is off. It’s been off for over four years (as long as I’ve owned the car). No problems.

Tom
’95 993

 

The GT cars do not have engine trays so it surely not for aerodynamics. My dealer told me to keep mine on, but I removed it anyway as the engine runs cooler, especially during the summer months.

Only time I would put it back on is if I drove the car in the snow and there was rock salt/sand on the roads. Then I think you can cause some problems up in engine area.

 

What about engine cleanliness? Does it get dirtier w/o the tray? Don't get me wrong, this pales in the discussion of valve heat or even aerodynamics for that matter, but I am curious.

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by JPS:
<strong>What about engine cleanliness? Does it get dirtier w/o the tray? Don't get me wrong, this pales in the discussion of valve heat or even aerodynamics for that matter, but I am curious.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">That probably depends on the roads you drive on. The roads around here are clean, so is my engine. Some people who live in climates where there is a lot of snow, salt, mud, etc, leave the trays on during the bad weather months.

 

Is there anyone in the LA area that wants to sell me there old engine tray?? max max@blue3.net

 

Good point...thanks.

 

I don't think the aero issue is resolved by looking at the undertray-less race cars. The racers have BIG spoilers that would provide far more downforce/lift reduction than the undertray. The road cars don't have those big spoilers, so it remains a possibility in my mind that there is some aero benefit. I 'd be surprised if it's significant, though -- I'm taking my undertray off, now that summer is finally here.

 

Max,

Check your email.

Edward