I haven't done all my research yet so don't slam me for asking this question prematurely. Ok slam if you must.
I wanted to get some opinions about AR ratios and why. My gut is currently telling me I need to be around .60-.70 on the exhaust and 1.0-1.1 on the intake with a TO4B. Where would this put boost levels approximately? Slow to spool or no? Too small for top end power?
Sure I just raised a thousand questions about how much boost, IC or not, what output am I striving for etc. If I need to get more specific to get real opinions I probably can later but right now time is short. Just thought I'd ask.
You are asking the wrong questions. Compressor cover a/r is almost irrelevant. Exhaust housing a/r is important but we need to know what your HP and boost goals are. Then you need to ask:
What compressor wheel and turbine are suitable?
With that turbine, what a/r is suitable?
Ya,
As a data point, the supra guys use compressor A/Rs in the 0.6 range. And those turbos make 500hp. Its the turbine that is more useful. Those same turbos will usally have a 1.0 on the turbine.
My T04b with H3 compressor(old) and 0.69 turbine P trim is tapped out at ~40lbs/min(~400hp)
I figured I'd be doing the can of worms ritualistic opening with this post so to help define things a bit;
I would like to start out in the 350+ range(Crank HP). My goal is to build a really quick, reliable street car with a ton of torque.
I don't want to exceed 15lbs of boost. I would like it as early as possible in the powerband but don't want stupid EGT's in the upper rev range.
My aim is to get the most hp I can without resorting to extreme boost levels. I am definitely going to run an intercooler but have not determined which type, size yet.
As I stated originally I have not done nearly enough research, or engineering on this project yet. I was just hoping to get some input from the people who have already crossed this threshold to help set some boundaries before I got too involved. Perhaps my first question was not the right first question to ask.
Ok slam if you must. 