ako
21-07-2005, 10:37 PM
Okay - this wasn't a proper study or anything as such, its more something I've been playing with for forever and though I'd make a note of.
Facts: Colder the air going into your engine, the more oxygen there is in it (colder = denser), and the more power you can make.
Second fact: The inside of your airbox is under a surprising amount of vacuum when you're at full throttle.
Therein lies my little discovery :)
Normal practise: Get car, discard airbox, throw in pod filter, if you're feeling crafty maybe even point a cold air duct at it. If you feel like doing things properly, you'll even make up a whole cold air box for it.
Method I've found.. Keep stock airbox. Get a decent panel filter (simply cause its better than the crap paper offering the car comes with) - block off the stock feed to it, and make up your own pipe to somewhere directly in the airflow, I just pull out a spotlight and use that. Bigger is better here.
Theory: Even when the car isn't moving, the only air it recieves is at ambient temp. Once its at speed, a slight "ram -air" effect is created - offsetting the normal vacuum in the airbox, and in theory giving increased response and reducing the work the turbos have to do slightly.
Results: I can only give them on my car (94 6A12TT VR4), but its a damn good indicator at least. Current mods are uprated intercooler, bleed valve, exhaust - rest of the list is things yet to go in.
Pod filter in open engine bay: 15psi @ 3000, drops off to around 10 by redline, 4th gear full throttle maybe 11psi. Aiming cold air ducting made negligible difference.
Stock airbox, K+N panel, unmodified - 16psi @ 3000, drops to 12psi by redline, 4th gear run will hold 12 psi right through, overboosts at low revs/ high speeds
Airbox w/ ducting, K+N panel - 18 (!!) psi @ 3000, 5th gear = full boost by 2600 rpm, 3rd and 4th gear run holds 13psi right out to redline, more towards the end of 4th gear, car is also much more responsive, and noticably quicker on the same boost then before, also half throttle for passing in 5th gear is a lot quicker.
Temperature differences @ throttle body - 1st test, around 60 - 70 degrees C (with evo 4 cooler), second dropped to 50 degrees, last test netted temperatures at the throttle body of around 40 - 45 degrees (at 16-18psi on td025s!!), cooled down as speed went up (funnily enough). I never tested the car with the stock intercooler, but my last one showed very similar results.
Even though it looks like I only gain maybe 2 or 3 psi for all that, on the road the results are better than simply raising the boost up. And on my white car, the difference between having 11psi at redline, and 13-14psi at redline, was the difference between a 13.4, and a 12.6. Try telling me thats not results, and the black one is feels as though its responding in much the same fashion.
I'll put up the results of heat wrapping the intake once I get around to doing it, I get the feeling it'll do similarly good things :)
Facts: Colder the air going into your engine, the more oxygen there is in it (colder = denser), and the more power you can make.
Second fact: The inside of your airbox is under a surprising amount of vacuum when you're at full throttle.
Therein lies my little discovery :)
Normal practise: Get car, discard airbox, throw in pod filter, if you're feeling crafty maybe even point a cold air duct at it. If you feel like doing things properly, you'll even make up a whole cold air box for it.
Method I've found.. Keep stock airbox. Get a decent panel filter (simply cause its better than the crap paper offering the car comes with) - block off the stock feed to it, and make up your own pipe to somewhere directly in the airflow, I just pull out a spotlight and use that. Bigger is better here.
Theory: Even when the car isn't moving, the only air it recieves is at ambient temp. Once its at speed, a slight "ram -air" effect is created - offsetting the normal vacuum in the airbox, and in theory giving increased response and reducing the work the turbos have to do slightly.
Results: I can only give them on my car (94 6A12TT VR4), but its a damn good indicator at least. Current mods are uprated intercooler, bleed valve, exhaust - rest of the list is things yet to go in.
Pod filter in open engine bay: 15psi @ 3000, drops off to around 10 by redline, 4th gear full throttle maybe 11psi. Aiming cold air ducting made negligible difference.
Stock airbox, K+N panel, unmodified - 16psi @ 3000, drops to 12psi by redline, 4th gear run will hold 12 psi right through, overboosts at low revs/ high speeds
Airbox w/ ducting, K+N panel - 18 (!!) psi @ 3000, 5th gear = full boost by 2600 rpm, 3rd and 4th gear run holds 13psi right out to redline, more towards the end of 4th gear, car is also much more responsive, and noticably quicker on the same boost then before, also half throttle for passing in 5th gear is a lot quicker.
Temperature differences @ throttle body - 1st test, around 60 - 70 degrees C (with evo 4 cooler), second dropped to 50 degrees, last test netted temperatures at the throttle body of around 40 - 45 degrees (at 16-18psi on td025s!!), cooled down as speed went up (funnily enough). I never tested the car with the stock intercooler, but my last one showed very similar results.
Even though it looks like I only gain maybe 2 or 3 psi for all that, on the road the results are better than simply raising the boost up. And on my white car, the difference between having 11psi at redline, and 13-14psi at redline, was the difference between a 13.4, and a 12.6. Try telling me thats not results, and the black one is feels as though its responding in much the same fashion.
I'll put up the results of heat wrapping the intake once I get around to doing it, I get the feeling it'll do similarly good things :)