radam

Hello all I am trying to pick out a turbo for my h2b and wanted to get some advice and thoughts. Motor is a stock euro r, will have headstuds, either a log or quick four manifold etc.. I am only looking to make between 300 and 325 hp with spool and transient boost response being my biggest concern. Basically I want a fun little street car that I might autocross. I seriously doubt I will ever want to make over 350 whp again. The turbos I am looking at are the gt2871r with t3 housing from atp, gt2876r and gt3071r. Is the h22 to big for the gt2871r? Does changing out to a t3 housing change the characteristics of the turbo? For the gt2876r it seems a little mismatched.

Any suggestions or comments are welcomed. If you think that there is a better option out there please feel free to post it.

viper_boy403

iTrader: (1)

My past 2 setups:

OEM RB25 turbo (ball bearing, small T3)





Precision 3431e .63 a/r





The small turbo was awesome for a street car, and great for autocross. The bigger one is still very responsive but nowhere near as much as the little guy. Love the 3431 though, very broad powerband

TheShodan

iTrader: (14)

You're asking several different things from the choices you're making with that displacement and use. If the 350hp to the wheels is the maximum you're trying to do with the car, I would feel safer to upgrade internals with more robust pistons and rods. If you're talking 350HP to the crankshaft, that translates to about 285whp (18% average difference), which is still within safe limits. (We go by power to the actual wheels for most reference points, not the crankshaft or Brake HP).

With that said, we need to know more of which areas you're going to focus on. That keeps it more into the GT2871R, or GT3071R. The differences really are more for the turbine wheel for midrange and upper rpm power. Not just the "spool up".

radam

I was talking whp. I was saying 350 as in a max that I might want to go in the future. My goals are 300 whp. Since this is a street car good midrange is what I am looking for. like I said the car will be used maybe for some autocross and having a little fun on backroads. Thanks for the responses

TheShodan

iTrader: (14)

Ok, I'll put it like this.

>50% on Autocross or circuit = GT2871R

>50% Streets and "backroads" = GT3071R

radam

Thanks for the response shodan. That actually makes sense. The car will mostly be a street car so the gt3071r sounds like it might be the winner. Any suggestions on exhaust housing size? Thanks in advance.

TheShodan

iTrader: (14)

T25 = .86A/R
T3 = .63A/R

Make sure you know that the housing that fits T3 is made for a GT CHRA as it is different than for the journal bearing series

This is assuming you're using the 60mm exhaust wheel with the double step heat shield (-22 numbered CHRA)

radam

Thank you sir

Geis

I thought the power loss to the wheels on fwd was more like 15%? On Ti everyone seems to think so, and they're pretty knowledgeable as I'm sure you are aware of. Elsewhere online I've seen turbo guys say for fwd it's closer to 10%, with rwd at 15% (can confirm I've seen this with rwd), and around 20% for awd. Bump the numbers up by 5% each and then you get another person's suggestion. I also believe I've seen awd with better than 20%. Can you help clear this up for me shodan?

TheShodan

iTrader: (14)

Nothing to clear up.. I overestimate all readings and don't try to split hairs like that. keeps from anyone getting precisely into the math mess you're trying to get into. So I take the average. Different dynamometers use different equations and factors in their calculations. In the end, its just a number, but knowing where you want to be makes a difference in one size of a turbocharger vs. another.

Geis

awww but I like math :<
Thanks for the help