garrett376

I am amazed at all the undertray activity on the board, so I thought I'd add to the fun!

Here is my method to take advantage of the aerodynamic effect of the undertray as a diffuser as well as addressing any issues with the rumored "baking of the engine" by having the tray on. By not having any rear or side panels, there is plenty of ventilation/air movement around the engine, yet the underside of the car is so smooth! And by cleaning out about 5 pounds of oily crud, the undertray is not all that much of a weight addition!

pete000

Is it possible to remove the rear and side panels with out dropping the engine???

garrett376

Yes - just undo the hex bolts that attach the panels to the undertray, then the bolts that hook into the engine tin. To get the rear panels off, you'll need to undo the muffler and heater tube crossover pipe. All possible without dropping the engine

Red rooster

That is real sideways thinking!! I put my undertray and side panels in the garbage a few years ago so damm or is this a reason to get busy with a sheet of aluminum and get the aerodynamics better !!!!!

Geoff

PC2

Garrett - How many seconds you think you can shave off of your lap time with the under-tray on?

garrett376

In fact, I am hoping it will help reduce the chance of getting sideways!!!

garrett376

I think new tires will be the biggest help in that department!

DarrylH

How do you get the car off the jackstands now?

garrett376

You know... it's funny you say that!

Had I not had 4 floor jacks, and several 2x6's, I would have had to remove the undertray to get it down! I was laughing at myself last night when I went to put the wheels back on and realized the engine is my usual jacking point. Uggh! I had floor jacks all over the place - at one point I actually had a jack under the rear tire to raise the rear enough to put a jack in the place of the jackstand - then I could lower it! Next time I will wait to put the undertray back on! I was just too excited to take it for a drive last night and wake the neighbors, all before 9pm when Lost was on (and it was a re-run anyways!!)!

pete000

Thanks for the info I will drop the side shields soon, but the lower pan stays behind the garage.

I was thinking you could cut a hole where the jack goes under the engine to allow the use of a floor jack. Should only cost you a few tenths of a mile per hour on top speed.

I just noticed your shocks. Is that an adjuster **** I see.

williamreinecke

I like the idea, but aren't the shields there to protect the valves from the heat from the exhaust system?

garrett376

Who knows?! It depends who you ask, and I think all you'll get are opinions!

My opinion: the valves are tucked in so far (behind the valve cover, under the cam tower, splashed with oil) that I doubt valve temperature is increased by the radiating heat from the catalytic converter or secondary muffler. The only thing I thought about for a moment was the heat affecting the spark plug wires - but I zip tie them close to the valve covers, and with a cat bypass, and a secondary bypass, it's not a problem on my car - in my opinion. I used to worry about road crap hitting and maybe damaging the plug wires, but with the undertray on there - no worries!

garrett376

Yes... LEDA's



It's interesting that for POC classes (stock, improved, V-class), the rules state: "Chassis diffusers and or aerodynamic modifications to under carriage are not allowed."

Yet the smooth underbody (including undertrays) are stock on 964's, so they're permitted - it's nice we get this advantage thanks to the good ol' "80% new 964"!!

PC2

Darn, I was going to install my 964 undertray onto my new 911.

C24FUN

There seems to be 2 schools of thought: One side says the box is there to be a heat shield, Two says they were added to comply with strict European noise requirements. Personally I'm in camp number two (which I think is also supported by Adrian S.). When I bought my '90 C2 (at 90,000 km) it was complete with undertray and all shields. One of the first things I found when doing a major tune-up was wear on the cam exhaust lobes of the two cylinders on the front left. There was also wear in the same place on two of the "low mileage" cams I looked at buying to replace the worn one when I did my top end. Didn't seem to me that the heat proofing idea was working!

My solution was to remove all the foam padding in each side panel and drill 6 large holes (2.5- 3" if I recall) while making sure the stainless steel shields are properly fitted around the CAT. This way I minimize the heat load, get better air fow around the engine and still have all the support points for the undertray. (which is also cleaned of its 10 pounds of oil soaked foam).

My2 cents worth...

Jim