Quote Originally Posted by SnakeyesTx
I'm pretty curious why vanos is limiting the rpm range effectiveness of a turbo. Isn't Vanos is basically just variable valve timing like the Honda Vtec? This is supposed to get more air/fuel into the mix which you can noticably feel around 3400rpm. What's wrong with putting a little boost in there too?

I can't write too much here, as I am packing to go home on turkey break. But, one thing to keep in mind is that a VANOS motor and non VANOS motor are different in more ways than just VANOS control. The VANOS motor is 10.5:1 compression, making it less happy when it sees boost. Its still doable, but that extra .5:1 compression works against you. Additionally, VANOS motors have a 228 profile cam, while NON VANOS has a 244 - more ideal for boost. Again, the VANOS has 6mm valve stems vs NON VANOS having 7mm stems, and most importantly, the VANOS has single valve springs while the NON VANOS has double valve springs which help the car rev MUCH higher - I've had my motor up to 7500 rpm.

The harder part is controlling vanos - unless you know how to program the stock motronic DME, you need an aftermarket ECU. I am running full fuel and spark control on MegaSquirt EFI, and don't have VANOS to worry about trying to control. Its tricky - though its just a on/off solenoid, it makes your timing figures and VE table tricky.

Do not expect to just bolt a turbo, exhaust, and charge piping up on these cars and using the stock ECU and upping the fuel pressure. It's more complex than that and you will not have a well-driving car should you do that. It takes a lot of work and a lot of thought - both of which I can share later when I get home from school, but for now I will leave that for you guys to consider.

a '92 525i is probably the best platform to start this on other than a 535i or something without VANOS worries.