thumpstick

I've been looking into doing a twin turbo set-up on my soon to be ls1 powered rx7. I want something that will spool up fast and still be able to make a good bit of power on a stock motor.

I found an air consumption chart for a stock ls1 and divided the 8psi numbers in half and graphed them on the gt28rs comp. map. I was hoping for some input from you guys who know more about this stuff than me (bout all of you)



I will be running a front mount and maybe a meth kit. the motor will have stock internals and I wont be running more than 8psi.

what do you guys suggest / how much power do you think this could be good for. Any input is greatly appreciated.

thanks,
-John

P.S. also, do you think the internal wastegates will be big enough if I'm only running 8psi? thanks...

cablebandit

iTrader: (37)

basically what an incon kit is...i did 736rwhp on those turbos and Onfire JUST ran a 9 with his kit with the gt2871 turbos. They should work well....8psi oughta get you around 550rwhp

thumpstick

wow, thats better than I expected. thanks for the input.

thumpstick

how about the wastegates, will they be enough or will I need to use external wastegates?

trtturbo

iTrader: (25)

We just finished a road race car with GT-35r's and the spool is great with them. We are still sorting out fuel issues(need more pump), but lifting at 5800 and only 14* timing, it did 589/521. I'm thinking around 630 with a little more timing and pulling to 6700. After that, we are bumping it to 12psi for hopefully around 700.

thumpstick

thats crazy..very impressive...what all is done to the motor itself, is it a 346ci?

cablebandit

iTrader: (37)

incon kit and gt2871 uses internal wastegates. For the same money, you can get gt3076 which flow even more

trtturbo

iTrader: (25)

347, Lunati stock stroke forged crank, Lunati Pro Billet rods, Wisecos -32cc pistons, VERY mildly ported heads with 2.0/1.6 stainless valves, 6.0 manifolds, 2.5 schedule 40 stainless to the turbos.
We used a cam that might actually hurt how it spools so that the power comes on a little slower. Coming out of the corners if it all hits at once, he will have traction issues. Its still going to be a handful. Torque was about 500ft lbs at 4000 and was almost completely flat until 5800 (521ftlbs).
I'll have another pump in it in a couple of days and post the final numbers.

thumpstick

Do you know the differences in spool times? I dont imagine that it would be much.

chuntington101

the Gt30s do take longer, not sure how much! if you would be very happy withthe power level the GT28s are cappable of then run them! you will see very little gain , if any, running the larger units!

plus i dont think the GT30s have internal gates, so more fab work needed!

thanks Chris.

DrTurbo

iTrader: (3)

The GT30's can be done with internal WG's. I know Jose has done them all the way to 35R's with internals. As for spool up, don't think you'll see a bit of difference between the 2 on that size engine. If it were a small little engine....maybe so. The incon kits spool almost instant....

thumpstick

Thanks for the info, I'll be looking into both turbos, but I would still like to know if the gt28's would be alright with the internal wastegates at 8psi.

thanks again,
-John

onfire

iTrader: (17)

Just make sure you spec the correct turbo. The GT2871R has internal gates with a T25 turbine size manifold. If all you want is 500-600rwhp they wil be loafing....many have gone over 700rwhp with two of these....8psi is cake.

If you think you want mega power down the road, spec the GT3076R with a T25 turbine size internal wastegate...they'll take you over 800rwhp.

Sounds like the GT2871R is what you need....it's NOT the turbo in the comp graph you posted above.

thumpstick

I'll take a look at the gt2871r. thanks for the input. 500whp is my goal, and in the rx7 (2800lbs give or take) it will be more than enough for me to get into some trouble. also, do you think that 500whp is posible with 8psi on those turbos (just want to be sure)?
-John

thumpstick

here ya go...does this look about right?

onfire

iTrader: (17)

500 at 8psi is cake with a good tune....you can keep the maf and make it drive like stock.

That comp map is closer but no cigar:

GT2871R

COMP: 53mm inducer, 71mm exducer, 56 trim 0.60 AR.

Turbine: 53.8mm inducer, 76 trim 0.86 AR.

The one you posted is for a 4 banger. The 0.86AR on the exhaust turbine is very important to reduce back pressure and make eff power.

The specs above will flow 44lbs/min each and support ~ 850 engine HP for 2.

onfire

iTrader: (17)

http://www.turbobygarrett.com/turbob...R_743347_2.htm

thumpstick

thanks, there were three gt2871r's in the garret catalog. I didnt know which one to choose.