[Cloud9...68]

There's been a lot of discussion about the effectiveness of the underbody shields (or panels, or whatever they're called), and everybody says they are important for managing airflow, and therefore help keep engine temperatures down. But does anyone have actual engine temperature information with and without the middle shield? Mine is missing, and I know I should replace it, but am wondering if this is the best use of my next $200+ on the car. Thanks.

Partial Post: Please Login or Register to read the full post.

[oppositelock]

Cloud,

There will be no effect on engine temp. There are several 968ers that run without them. I think later years came without them and I am sure that any track dedicated 968 would run without them. Why have them? Clean underbody and small effect on high speed fuel mileage.

Mitch

Partial Post: Please Login or Register to read the full post.

[Darryl]

By no means an expert on this topic, but I always thought they were for aerodynamic purposes, not temperature purposes...



- Darryl

Partial Post: Please Login or Register to read the full post.

[SILVY968]

When I got my 968 the front, black piece was missing. I was told that that pan had to do with cooling. the second pan that covers the engine was more for airflow and protection than for temp.



Brian

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

Thanks. I was under the impression that the middle pan assisted the from pan with drawing air through the radiator and under the car, thus aiding engine cooling a bit. But it sounds like that effect is very minimal at best. Thanks; I'll prioritize this very low.

Partial Post: Please Login or Register to read the full post.

[flash]

it does make things run cooler - the thing is that you won't see the difference on your water temp gauge because of the thermostat - it will maintain the same running temp - you can see it in oil temps (if you had a gauge, though you would not generally even see that on the street) - you will also see it in under hood temps



i have not been recording the location by location data, but with the 3 pans in place, my underhood temps were down an average of 5 degrees over just the 2 pans - i did a "just for giggles test" with the front apron alone and temps went up 8 degrees



i managed to drop the underhood temps another 10 degrees overall by adding some more engine bay aerodynamic devices that further limited and reduced airflow into the engine bay



my last day out on the track, my oil temps never got above 235 - that is a full 30 degrees lower than the previous track day, and the ambient temp was less than 10 degrees different between the 2 days



i think i picked up about a mile to the gallon too

Partial Post: Please Login or Register to read the full post.

[S_Cal968]

Without performing testing in a controlled lab it would be hard to validate actual numbers, the variables vary greatly....

IMO the second cover is there to reduce drag at high speed. Without the cover the airflow would hit the engine cross-member causing turbulence. And, as a result air may be directed away from the cooling fins on the oil pan.

Generally any drag reduction [less drag coefficient] on the underside of the car will assist stability at high speed. The less turbulent air under the car the better. This why splitters are popular in racing - they direct air around the car instead of under it.

The first time I took a look under my car i noticed that it has a fairly clean air path, nothing hanging down obstructing the flow.

Partial Post: Please Login or Register to read the full post.

[bob blackwell]

I have been running my 968 without the second and third under engine covers for several years. No significant difference in the engine temperature. It is just a lot easier and quicker to change drain the oil without them, and there is a sleight reduction in weight. The first cover (black, plastic or rubber material), protects the engine oil cooler from highway debris and needs to be in place. Good luck, bob blackwell.

Partial Post: Please Login or Register to read the full post.

[S_Cal968]

That's news - with the talk about a third cover, I checked the PET and sure enough there is a 3rd cover panel. I've owned the car for 4 years and didn't know mine was MIA.

Once again I'm thankful for this forum...

Partial Post: Please Login or Register to read the full post.

[flash]

i agree that more controlled conditions would validate the "data" i have gathered, but i have been watching this pretty closely over months of driving post mod, and using a laser thermometer to measure the underhood temps, looking closely at specific areas to see what different mods are doing - the readings are pretty consistent



the oil temps have been the real winner for me - any time i would extend revs to beyond 5k for any long periods, my oil would go up to 250 or better - i have not been able to get it anywhere near that temp now, regardless of ambient temp



again, nobody will see the difference on their water temp gauge - the thermostat will tell the cooling system to keep the water at the same temp, regardless of the underhood temps (within reason of course)



the additional pans facilitate the negative pressure zone, which promotes airflow through the radiator, thereby increasing cooling efficiency - there is a very nice article here:



http://www.autospeed.com/A_2159/cms/article.html

http://www.autospeed.com/cms/A_2160/article.html

http://www.autospeed.com/cms/article.html?&A=2162



they also make some very nice aerodynamic improvements

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

Good discussion - thanks, everybody. Flash, you make some very good points - I asked for data, and you delivered! However, I don't understand why you say the water temp won't be impacted by improved airflow through the radiator. I can easily see the reading on the water temp gauge drop when running at a higher steady speed, vs at a lower speed, for the same engine rpm. I thought that once the water hit a specified temperature, the thermostat opens all the way, and doesn't really vary the water flow as a function of temperature, except possibly at extremely low ambient temperatures. Have I had it wrong all these years?



I wonder if the 2nd (and third) pan improves airflow under the hood and around the pan, as evidenced by Flash's lower under-hood readings and lower engine oil temperature, but not necessarily through the radiator(?). By the way, an oil temperature gauge sounds like a really good idea. Anybody know if 968 Engineering is still offering them? I'll take a look when I'm done here... [edit: I just checked, and 968 Engineering appears to have closed up shop. Anybody know of anybody who does something similar?).



One thing's for sure - look underneath any modern car (our new BMW 328i being a case in point), and it's amazing how completely sealed off everything is. The 328 has plastic covers pretty much under the whole car. Ferrari started doing this years ago, so there must be something to it.



Well, a new the middle cover is still on my list, but not near the top at this point, as I don't drive the car enough to likely see the benefits, and the tracks I've driven on are more "technical" in nature, as opposed to high speed.

Partial Post: Please Login or Register to read the full post.

[flash]

the temp fluctuations are most likely an airflow thing - what temp fan switch do you have? it may be as simple as your fans not coming on early enough



the indicator of how well your system runs is to go out and hold 5k or better for a few minutes - see what happens to your temps - if it's right, your water temp will never climb much above halfway, and never get to the 10 o'clock line



my car used to get up there to that line, but not since i added the pans and made the other mods



dave closed up shop with no comment toward reopening



the tracks i'm driving are also purely technical - not had it out on a high speed track yet - the changes i've made, and the benefits of the pans have been seen off the track, in the canyons as well - anytime i am running over 5k for more than a few seconds it shows up



i'm not saying your car is going to over heat without them - clearly unless you are in a heat wave, it won't - but, it will run cooler, and give you less drag with them installed, but none of it is huge, and likely not a real issue either way - i am after the "enth" degree, so it makes a difference to me - i'm still working the rest of the pans to finish off even more of the underside of the car

Partial Post: Please Login or Register to read the full post.