Discussion
Why bother? As soon as the car starts moving the negative pressure behind the back of the car will pull air out of the engine bay through the big hole in the back of the rear clip. It will also suck air from under the car, adding to down force. Stationary the hot air can escape up through the vents either side of the air scoop.
Well if standing still, fan ≥ hole. But at speed, the fan would only create drag. And generally engine temperature is quite proportional to speed (ie engine is working more to maintain speed), so I personally do not see any benefit to putting a fan there. If I needed to cool my engine after some lap work, I'd just open the clam.
AlexCim said:
Well if standing still, fan ≥ hole. But at speed, the fan would only create drag. And generally engine temperature is quite proportional to speed (ie engine is working more to maintain speed), so I personally do not see any benefit to putting a fan there. If I needed to cool my engine after some lap work, I'd just open the clam.
have you measured air speeds at the rear grill? If not then there is no way of knowing how much slower than road speed it will be, only that it will be! 
How many clams have you seen burnt or discoloured from engine bay heat?
My mechanic services a twin turbo CanAm and that is circa 850 BHP and that has only the standard heat cloth (zirtec coat on the headers)
Mine is s/charged and the clam is painted, I haven't had any problems with discolouration.
My mechanic services a twin turbo CanAm and that is circa 850 BHP and that has only the standard heat cloth (zirtec coat on the headers)
Mine is s/charged and the clam is painted, I haven't had any problems with discolouration.
F.C. said:
How many clams have you seen burnt or discoloured from engine bay heat?
My mechanic services a twin turbo CanAm and that is circa 850 BHP and that has only the standard heat cloth (zirtec coat on the headers)
Mine is s/charged and the clam is painted, I haven't had any problems with discolouration.
That's good to know as the clam on the Can-Am is just inches above the engine.My mechanic services a twin turbo CanAm and that is circa 850 BHP and that has only the standard heat cloth (zirtec coat on the headers)
Mine is s/charged and the clam is painted, I haven't had any problems with discolouration.
Funny how cooling always comes up at least once every 6mths, LOL!
What is it that people want to cool tho'? If it's the engine itself, well, I don't think that's a concern..... even idling in 30degree heat (stop/start traffic) for 90mins, my LS3 Can Am won't overheat. Oil & water temps are fine.
The clamshell itself, however, does get very hot (although my headers do run very close to the bodywork, so that's no surprise). I've burnt my hand on the metal vents before now
Also, inlet air temps get very hot, but that's more to do with making sure the airbox is insulated from the engine better and has better fresh airflow.
I'm not sure what a fan on the rear clam is going to achieve, if I'm honest.
What is it that people want to cool tho'? If it's the engine itself, well, I don't think that's a concern..... even idling in 30degree heat (stop/start traffic) for 90mins, my LS3 Can Am won't overheat. Oil & water temps are fine.
The clamshell itself, however, does get very hot (although my headers do run very close to the bodywork, so that's no surprise). I've burnt my hand on the metal vents before now
Also, inlet air temps get very hot, but that's more to do with making sure the airbox is insulated from the engine better and has better fresh airflow.
I'm not sure what a fan on the rear clam is going to achieve, if I'm honest.
AlexCim said:
Why bother? As soon as the car starts moving the negative pressure behind the back of the car will pull air out of the engine bay through the big hole in the back of the rear clip. It will also suck air from under the car, adding to down force. Stationary the hot air can escape up through the vents either side of the air scoop.
Completely agree that fitting fans wouldn't be a good idea... don't agree with every tying else stated, especially the air coming from under the car adding downforce... it defiantly helps cooling but its more likely to rob the car of downforce.andygtt said:
Completely agree that fitting fans wouldn't be a good idea... don't agree with every tying else stated, especially the air coming from under the car adding downforce... it defiantly helps cooling but its more likely to rob the car of downforce.
Agree, down-force of any significance would require quite some modification including but not exclusively a completely flat underside especially if you were trying to reduce drag at the same time.andygtt said:
Completely agree that fitting fans wouldn't be a good idea... don't agree with every tying else stated, especially the air coming from under the car adding downforce... it defiantly helps cooling but its more likely to rob the car of downforce.
Andy didn't you say once (sorry it might not have been you! ) that you thought that air actually was flowing IN the rear vent at speed? has anyone tested this? If this is the case, then where is the air going once it gets in the clam? chuntington101 said:
andygtt said:
Completely agree that fitting fans wouldn't be a good idea... don't agree with every tying else stated, especially the air coming from under the car adding downforce... it defiantly helps cooling but its more likely to rob the car of downforce.
Andy didn't you say once (sorry it might not have been you! ) that you thought that air actually was flowing IN the rear vent at speed? has anyone tested this? If this is the case, then where is the air going once it gets in the clam? You guys have a wonderful saying that is attributed to the Scottish "If it's not broke why fix it" At least I think it's Scottish. Think about it, most front engine cars today have tiny little openings in the front and all the hot air off of the radiator goes into the engine compartment which is about as stuffed as Dolly Parton's bra. The Ultima has quite a bit of room around the motor and multiple spots to bring air in and out. Southern Cal traffic and 100 degree track days logged on a Motec I have never seen any temps that really needed attention. Car is 5 years old and the gel coat on the clam shell looks as good as new. If your going to run the 24 hours Leman's maybe. Lee
UltimaCH said:
Perhaps some openings (gills) on the side of the clam of the GTR like MacGRacing have on their GTR would get some extra air flowing in the engine bay when on the move
We saw fuel temps drop significantly (10's of degrees from memory - would have to dig out the figures) when we fitted these, in back to back tests.There were also a couple of other mods done, such as removing the rear mesh.
Gassing Station | Ultima | Top of Page | What's New | My Stuff