I posted this on Jose's message board and I still have not received and answer so what do you guys here think?

In going over the compressor maps for the T-70 and T-76
If I run a 355 LT1 @ 10 PSI
The Airflow usage chart I have shows that I will need about 34lb/min of air @ 3500RPM's @ 10# of boost
and up to 60lb/min AF @ 6200RPM's @ 10# of boost

I assume with both turbos, I will be at full boost around 4000-4300RPM's.
So looking at my usage pics:
The T-70 looks like I am @ MAX efficiency with the turbo spinning @ about 55,700RPM's when full boost kicks in. But then it looks like if I want to stay at 10# efficiency starts to fall off at about 4500RP's and drops to below 70% @ 6200RPM's (not sure exactly because this map didn't have efficiency %)..

The T-76 looks like I am right before it gets into MAX efficiency with the turbo spinning @ about 56,000RPM's when full boost kicks in. But then efficiency starts to fall off at about 5400RP's and drops to about 74% @ 6200RPM's..

My main question is do I want to be at max efficiency through the lets say 4000-5500 RPM range and then not worry about it falling off a little after that or is it better to be a little low on efficiency when you first hit full boost and then get into MAX efficiency through the rest of the RPM band?

And nothing says that I am even reading this correctly, but I really think I am...


BTW, before I get a lot of responses about this not working on my current setup, I know this.. I am just trying to get all the right info to make an educated choice when I do go with a new setup.

 

I hate doing TTT's but I thought this would be an easy question to answer...

When readining the maps above;
Do I want to be at max efficiency through the lets say 4000-5500 RPM range and then not worry about it falling off a little after that?
or
Is it better to be a little low on efficiency when you first hit full boost and then get into MAX efficiency through the rest of the RPM band?

 

With either turbo, you will see maximum boost before 4000 RPM. I'm spinning an H2D at the end of my exhaust, and I see maximum boost just before 4000 RPM. You should see full boost before 3000 RPM on a conventional setup.

You are reading the maps correctly. I would go with the T-76, as the T-70 may be near it's efficiencey limits on that application. My guess is like everyone else, you will want to increase your horsepower by increasing your boost. The T-76 will give you a little bit more room to grow.