Brettus

Question :
Two identical turbos except for the compressor wheel , both flowing exactly the same amount of air.

Turbo1 : has 60% compressor efficiency
Turbo2 : has 70% compressor efficiency

Which one has lowest EGT and backpressure?

If you think it's turbo1 ...you need to read this :
From Corky Bell's book on turbocharging ....................The turbo is part of a system where Everything affects everything else".

TeamRX8

iTrader: (2)

It makes as much sense as a vendor posting their marketing hype on a website you can’t look at with out signing all your privacy rights away to join and view. Particularly when they have two or three company sites that haven’t had much posted on them the last year or two. Business must be good to blow off 30% or more of a market that isn’t signing up for that.

zx1441

When we ran hybrid turbo chargers on our motorcycles 20 years ago, the larger compressor wheels always made more power at even 16.psi would make 30%+ more, like 100 hp at 30 psi then our standard off the shelf GT35's- both using the same size exhuast wheel. We could also run a fuel with less octane when we had more compressor.

When you have 2 turbo chargers that are identical except for one having a larger compressor wheel, on the dyno you will see that the one with more compressor will make more horsepower per lb of boost, which in every single provable test will show LOWER emap. That is a fact. It doesn't matter if it's a rotary , piston or diesel.

TwinCharged RX7

iTrader: (14)

Yes. All else the same, the one with lower efficiency is using more energy. If it's using more energy to create the same close, that means exhaust is pushing harder on the turbine (higher emap) to create the higher boost in order to match the airflow of the turbo with the higher efficiency compressor.

If that's not true, then the compressor efficiency wouldn't matter.

dabigesii

iTrader: (4)

Just bumping this up for any new info.

BLUE TII

iTrader: (9)

I think you are wrong on the compressor efficiency.

Compressor efficiency refers to adiabatic efficiency or how close to the ideal gas law the compressor actually works.

More efficient compressor will provide a denser air charge to the motor.

More air molecules.

Coupled with more gasoline molecules to maintain the desired air fuel ratio.

Equals more power!

Equals more exhaust...

More exhaust in the same exhaust housing and same exhaust wheel means higher exhaust pressure.

The problem with blindly using the word efficiency...

Compressor efficiency has nothing to do with the amount of power required to spin the compressor.

Now, you are going to say the larger compressor turbo can be used at lower boost to make the same power as the smaller compressor turbo and so have less exhaust pressure because the compressor is requiring less work from the exhaust.

Yes!

The larger, lagier turbo used at lower boost will have lower exhaust pressure.

Its up to each user to decide where their sweet spot is in terms of turbo response vs power.

9280 vs 9180 and 8474 vs 8374 is pretty much all going to be a wash in this scenario in my opinion.

Its not like someone choosing between making 400whp on a 7670 at 18psi boost vs a 400hp on a 9180 at 14psi boost.

What matters in 9280 vs 9180 and 8474 and 8374 is the larger turbo can make a bit more peak power when maxed out.

So that is if you really want 600rwhp on the 8474 vs 550rwhp on 8374 or really want 750rwhp on the 9280 vs 700rwhp on the 9180.

Below that max power there will be more variance in power from porting, intercooler, intake manifild, wastegate size, etc.