MyE28.com

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.

Thanks, Greg.

Greg,

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?

Todd

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)

RussC

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.

T04E with a 50 trim wheel, P trim turbine and .58 housing sounds ideal for you.

You do not want a T04B. They are usually equipped with older style wheels that spool ~400-500rpm slower than a similar size wheel .

Todd

T_C_D wrote:T04E with a 50 trim wheel, P trim turbine and .58 housing sounds ideal for you.

You do not want a T04B. They are usually equipped with older style wheels that spool ~400-500rpm slower than a similar size wheel .

Todd

Are the old b series that much slower? Immm not so sure. But they are slower.

I didn't recommend the b, but if your budget concious and its nearly free...then....

The e's are better though. Map looks pretty good...


RussC

The available wheels in the B series suck. Not sure how much the cover actually contributes to the spool up and efficeincy.
Todd

T_C_D wrote:The available wheels in the B series suck. Not sure how much the cover actually contributes to the spool up and efficeincy.
Todd

Umm, maybe my ignorance is showing, but cant you put any wheel in the B series that fits? Like newer wheels with better efficiency?

But, then you might as well buy a newer turbo than go to that extent/expense.

RussC