hey guys. i was wondering if the s5 intake manifold would work for an s4 fc. i have a 91 vert that has cooling problems and is now basically a parts car. if you can swap teh s5 mani to the s4 would it see any improvement on performance, driveability, etc? any help would be appreciated

 

Yes, it has been done before (including by me). This is one writeup: http://homepage.mac.com/carldavis/intake.html

It requires a little creativity and some tools like a grinder/dremel, but the S5 manifold with functional VDI has better midrange and topend torque than the S4. You'll need an air pump/rpm switch/solenoid setup to control the VDI valve like an S5 does.

 

i've done it a few times, to make everything functional takes a little bit of work, i personally have been a "wire the secondaries and VDI open" kinda guy... a lot of arguments have been started by the whole secondary thing, but my philosophy about the whole loss of low end power is... if your not revin' the **** out of it then you aren't driving it!!!!!!! by installing the s5 intake you will get larger intake ports and a little longer intake runner i believe which will give a a little more power and torque... but you really also need to take into consideration the other mods that need or have been done to the car as well to get the most out of the mod... you are opening up the intake so the only way to receive any "noticeable" results is to at the very least have some exhaust modifications... these cars have a lot of cats and they are like cancer to getting a car to breathe so open up the exhaust and you will see better results... whether this be gutting the cats or getting an exhaust that just eliminates them... this mod can be as easy as bolting it on, which i've done ( i only really recommend this for race use or high rpm driving), but you will have better results if you rig up the secondaries and vdi for a more streetable approach...


all i can really say at this point is... it's 11 p.m.... i need another shot.... good luck.... ALL HAIL THE ROTARY!!!!!!!!! PEACE I'M OUT

 

With the VDI closed, it's actually a 400 mm longer intake path than what's found on S4s. This means more midrange torque. With the VDI open, it's a 200mm shorter intake path than the S4 manifold, which equates to more peak power.

This chart from the S5 SAE paper shows the torque difference of various runner lengths.