area under the curve - reading dyno graphs
 

In general, smaller turbos spool faster, but power falls off on top end. And larger turbo's are slower to spool, but really sing on top end. Since RPMs may be limited to just 7500, isn't it entirely conceivable that a smaller turbo might produce as much total power from 3500 to 7500 as would a larger turbo from 4500 to 7500? Obviously, if you can rev to 8500, then the larger turbo is probably going to win the area under the curve contest. But aren't most guys running 3mm seals setting the rev limiter at 7500?

My question then is not which turbocharger makes the most PEAK power at 15lbs, but which one produces the largest total area under the curve at 15lbs. It would be the one that spools the quickest and holds in the efficiency range the longest. Which turbo is that?

your best bet is to look here for some general info on different sizes and results, but even then every car is different ! sadly enough with rotary cars nowadays theres a bit of dispairity between cars "running well" and "not running well" so its tough sometimes to look at other peoples graphs and pick the "best" turbo

http://dyno.zeroglabs.com/dyno.php

It depends how you use your car...do you rev it to red line and shift hard and fast. What is the RPM range you want to use? What is the boost level you like to run?

I like to get on it from 2nd-4th when I bump into somone around town or on the highway. I'm a little shy about shifting too hard and fast, as I've missed 3rd twice and broke shit. Playin' in the 17-24 lb range. 500rwhp is fast enough for me.

Race ported with plenty of fuel, air, spark, exhaust. T-61 BB Q-trim 1.0a/r.

I want to believe so bad that my absurdly expensive turbo was the best thing I could have bought, but the more I learn from reading here or there, the more I wonder if I should have bought a gt35rs or a gt40r. I've looked at the compressor maps I can't make heads or tails of it. I tried to compare dyno graphs but that's pointless because of the variables both known and unknown. I don't know if I should be comparing mine with the GT40 or the GT35rs.

Aside from performace differences, I also suspect that the gt series turbos will last longer than the t-series just due to advances in bearing design.

On my car, whats the main performance difference I would realize over my T-61 if I were to go either GT35rs or GT40r?

My car screams and I'm actually very happy with the performance, BUT if I know I could get the same results with less boost, then that's how I'd prefer to spend my hard earned money.

In 3rd gear, from 2500 rpm to 7000rpm what does your boost curve look like?

I don't honestly recall what rpm it hits full boost by. I found this graph of a t-61 on a stock block engine:http://dyno.zeroglabs.com/graph.php?...1&SUBMIT=GRAPH.

^I believe this was on a Mustang Dyno, and that this car ran an 11.3 at 126mph.