I looked at his setup and Ken has limited his air flow to the rad. by using the oil cooler opening but I would still think when you start getting above 100 the effects will be more pronounced I may be totally full of poop hope someone else will chime in that has experience with this at higher speeds than 100 I know I have lots of ground effects on my car and the handling chara. changed at 120 and again at 140. Good luck and just be aware of the possibility at speeds above 100 there will be handling changes most likely understeer.

Take a look...

Mine:
http://i18.photobucket.com/albums/b1...an/photo-6.jpg
His:
http://hatfield.homelinux.com/cooling/38.jpg

I don't get it? Please point out the differences... Also, my bumper is..

http://www.octanemotorsports.com/images/EXD-1053880.jpg
Which will be ducted on the underside to feed the rad, just as Ken has done..

An idea would be to seal off the bottom and duct the air out the side into the wheels wells and use it to cool the brakes ala Matteo's car. Just a thought. I would think at >100 Ken would have the same issue maybe not I am just going off how the ground effects are setup for high speed road cars they duct the air out and up away from the bottom.

I feel better with air coming out the bottom, rather than reduce the structural integrity of the entire front of the car by cutting away the sheet metal around the wheel arches and replacing it with a mesh.

The 50+LB of coolant, radiator, pumps, hoses will have more effect on downdraft than the 2800CFM fans will at full tilt. The fans are totally sealed to the radiator, and you cannot pull the air through the fins that quickly.

It s your car but just to give you some food for thought here is the link to how Matteo did it in your case you could attach the rigid duct to your airbox and flange it to the wheel arch and maybe add some structural reinforcement around this area. My last word on this and I think this is a cool project as well as Kens. Just giving you a different look at how to route the air.
http://forums.pelicanparts.com/porsche-911-technical-forum/260064-3-9-rsr-project-my-carrera-reborn-14.html

re: air flow
 

I can only speak for myself, but on custom projects, I believe that exchanges of ideas and experiences are important.

I too believe that cutting into the frame, ala the 3.9 RSR project, or a Rod Simpson type cooling system, wouldn't make me feel real secure at speed.

I would believe that the front valance design would be important and mbaran's would push more air under the car that the 930 type that I have, which, in theory, should push the air around, more than under, the car. I would think ride height would be an important variable, as well. My car is set to 25.5 inches ground to the bottoms of the fender openings.

I do know that connecting ductwork between the valance and the radiator box made a difference in fan run times and coolant temperature. The ductwork being connected made a huge (positive) difference. That being said I can only conclude that the air naturally wants to go around and under the radiator box, between the valance and the frame opening, unless forced into it.

My car is probably helped by having a the additional weight of the larger renegade full tank as well as the condenser, radiator, coolant, etc.

I suspect that the handling will change at some speed, but it won't be 140 as I'm electronically limited to 135 :).

Regards,
Ken

Ken,

How much temp change did you see with the ducting straight to the rad vs. without?

My car is very low, and with the splitter installed below the bumper, there is only a matter of a few inches between the ground and the bumper. The vacuum under the car will more than make up for any added air.

Did you notice any change in handling by pumping that air out underneath the car? My guess is since the underside of a car is a low pressure area, it just sucks that air from the back of the fans and is negligible.

radiator exhaust
 

ive run my longhood up to some rather high speeds and have not experienced any sudden frontend float that i would attribute to the radiator exhaust. i have often wondered just how much speed i might be able to attain before contol of the front end maybe got too hairy. not to high jack the thread but what might be the upper limits of stable speed for an early car....with rs flares and a ducktail.... with high horsepower. pic of front end of the car.http://forums.pelicanparts.com/uploa...1261968256.jpg

By cutting the gas tank in half you lost 9-10 gallons of gas I suspect at 7-8 lbs per gallon you lost 60-80 lbs of weight and added about the same the structural part of that area is above and below where you would attach the duct and my thought is if it reduced the structural integrity that much then why did they do it on race cars. Another thought is you cut the gas tank in half which is attached to the frame in a triangulated format when you cut it in half you take a third of that away and add flex.

The gastank is also fastened to the car with like 3 flat washer plates. It's not structural as much as the front sheet metal is.

I'm not saying there arent other ways to doing this, I'm just building a kit that mimic's the kit of Renegade Hybrids as best as I could and pretty much how I've seen every front radiator'd 911 done.

I'm sure there will be course corrections as we polish the final product.

gas tank
 

my front compartment is essentially the same as mbaran. i have used the cut down gas tank for several years and have not experienced what i would consider loss of structural integrity in the front of the car. as my car is solely for the street i do not worry about it. i probably stop more often for fuel to feed the all aluminum 434 sbc roller engine. but, with almost 600 chp i expect too!

mbaran,

The temp difference was on the order of 15 degrees Fahrenheit.
I didn't notice any handling difference with or without the ductwork.

I was going by the picture you posted earlier in the thread which didn't
show a splitter. The splitter should indeed help increase the vacuum
under the car.

Ken

i agree with pt109 about the front opening ductwork. my air opening is also connected and sealed to the radiator box. a few conversions have the radiator ducted to exit to the top through the front compartment lid. it would be interesting to see details of such???

Mine won't be entirely sealed, but I will seal off an appropriate sized section equivalent to the bumper you're both using.

There's a member here and at LS1Tech called LazyLongBoarder who has an LS1 964. I'll see how his is ducted.

Here is your link for the elephant racing bonnet conversion
ELEPHANT RACING Hood Vented Oil Cooler Project

Hi Ken, I looked at your conversion pics. You mention the A/C compressor. Did you get A/C working with you conversion? If so, so you mind sharing some of the details? Thanks, Mike

re:A/C
 

My air conditioning uses stock 911 parts for the evaporator, R134A expansion valve and dryer.

The compressor and brackets are off of a LS1 Camaro.

The condenser is a generic multi flow unit, I don't remember the size, but it was
the biggest one that would fit in the radiator box.

The lines are all custom made.

The radiator uses 2 Spahl fans oriented as pullers, the A/C adds a third
fan in front of the condenser oriented as a pusher.

The condenser went in the front as it had to be removed from the decklid
(as well as cutting the decklid and adding a tail) to make room for the air cleaner.

Any other questions just ask.

Ken

Cool project
I would like to add from my experiance with aerodynamics without making it to technical is:
1) The more air over the top of the car creates lift. exp. airplane wing
2) As in the pics at the Elephant Racing hood vent ,in front of the car there is a high preasure area that builds greater with speed and the air forced through a cooler becomes less
3)Oil coolers have been installed in the front of racing Porsches forever
4) It is not a fair to compare a 917 to a 911 as far as the frontal area is concerned,as the boundary layers and frontal preasures are not the same
I know I have been kind of direct and with all in involved I show my respect to all answers before this post
I could go on and on about aerodynamics ,but what you are doing is good and dont be suprised if the fans do caome on at a high rate of speed
just my thoughts

great project, it sure looks like a lot of work....

It is, but it's fun.