924Board.org

[wdb]

I'm used to american cars,and my 80's intake system is very different than I'm used to.The air enters the system and immediatly makes a 90 degree turn into the filter box, than a 90 degree turn out of the filter box, than a 90 degree turn into the metering plate housing,than a 60 degree turn to the throttle body,than a 110 degree turn into the throttle body, than a 180 degree turn in the intake, than a 90 degree turn into the cylinders. this can not be good for clean air flow. It seems to me that making a intake manifold,so that you can turn the throttle body 150 degrees so the inlet points at the metering plate,should not be that difficult. a piece of thin walled 4" square tubing,5 " long(area to be used to mount cold start valve and other components that are attached to intake man.) with a plate on 1 end to mount the throttle body,and 4 pieces of 2" round tubing coming out the other end with small plates for attaching to head,should be a piece of cake for a welder or fabricator.1 of you racers has to know someone who can do this.ford,chrysler,and chevy developed cross ram and tunnel ram intakes for scca in the late 60's,because the agressive cams and HIGH comp. pistons needed to breath better in order to make full use of the engines potential. see cross ram and tunnel ram
http://victorylibrary.com/mopar/intake-tech-c.htm

[924RACR]

True, but one of the reasons for all this is to increase the length of the intake tract thereby improving torque output at lower revs. Turns like these are the best way to package it all into the engine bay.

Just wanted to set the record straight for the rookies out there; of course what you speak of is desirable for a race car, but the long intake works better for the street. A straight-in intake is like what they did on the D-prod cars. For me it's irrelevant since that'd be illegal. All I can do is try to improve my (originally very crude) cold-air intake.

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[larso]

Yup, same as exhaust, longer has advantages if you aren't sailing at 6600 RPM all the time.
If you are, well then go short, but not so short since your car can't do 10 000 RPM (for example running with just 1 inch headers and 0.5 inch intake pipes would be good if your car could do 9000 RPM 100 percent of the time you are driving)

[Dave]

So if I run longer headers on my 924S I will have better low end power??

[larso]

longer skinnier ones yes, generally a longer skinnier exhaust on NA cars gives you a wider power band and more low end, fat short pipes give you a more localized shot of power in the upper RPMS
but it's really hard to find out whats best for your car unless you test a whole bunch of different sizes out, expensive $$$