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Discussion Starter · #1 ·
As the title says i'm wandering what max efficent boost would be before the housings become maxed out.

GT28rs with 0.64 ar exhaust

Running a 2.0ltr with some head work, 264 cams, EMS if it relivent

Cheers
 

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It will become maxed out at every boost level as the engine's airflow approaches +/- 35 lbs/min. You can see that on the compressor map at http://www.turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT28/GT2860RS_739548_1.htm. On a stock VE engine that will be around 7200-7500 rpm as far as I can tell. This turbo was recently used as an example in the thread Turbine Efficiency Part 2 http://www.mr2oc.com/showthread.php?t=157929&highlight=turbine+efficiency. You can calculate your modified engine's airflow requirement and compare it to the compressor map using the formulas and procedure used in this thread http://www.mr2oc.com/showthread.php?t=159521&highlight=turbine+efficiency.

You will likely find that your modified VE engine will have exceeded this turbos ability to maintain full boost likely around 7000 rpm or so, and power will continue to fall off above 6000 rpm as compressor efficiency starts to drop off as you rev higher. I run 17 psi and hold it to 7500 rpm. If you want to run 22 psi that's fine also, but you will run out of flow sooner, and boost will drop as it does.

Your situation is the toughest of all to find a perfect turbo. The GT28RS provides the most power possible up to around 6000 rpm, but beyond that is where larger turbos like the TD06, SB 46T or GT3076R will show their high rpm flow strength.

Bruce

Edit: A lower turbine AR (ie .64) is used to maximize spool, whereas the higher AR (.86) would be chosen to maximize higher rpm flow...a goal consistent with the use of cams, as in your situation.
 

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Discussion Starter · #3 ·
ok cheers,

so this turbo is limited by its flow and drop off at higher RPM,s i was just wandering if there was a max psi boost like on the ct26 we say thats 15psi before things become impracticle.

I think i'm just going to tune this gt28rs to a boost and power level i'm happy with and upgrade if needed as like you say it might drop off at top end, maybe gt2871r or the gt3071r
 

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You're going backwards a bit with your setup, the GT28RS is really great for a stock VE 3S-GTE, but if you're putting those bigger cams in there (shifting your powerband up), but staying with the small turbo is just not right.

Things will be a lot better if it's matched properly. For those VE I suggest you run a bigger turbo, like a TD06.
 

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Discussion Starter · #5 ·
if i was building this all together i would be fitting a larger turbo. But i already have the GT28rs kit fitted to the car about to get mapped on a standard gen 3 internals engine and see what it makes.

The engines i'm building i've gone all out with but its still being used for street use only, So its not a big deal once built to see what the gt28rs put outs and if i want more just swap it over to the gt3071r or something similar to make over 400bhp.
 
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