EFI University

mrx · Joined: 05 Nov 2005 Posts: 486

Hi,
i've just an idea in my head and would like to hear your oppinion.
what if i'am running a GT28RS .83ar T3 turbo and beeing quite happy with the response but searching for small improvements. Thats why i would try a T3 .48ar exhaust housing for better spoolup with the compromise of a little topend power loss, but maxing out the compressor at 21psi of boost.

How do you think, the same exahaust combination would play on a GT2871 compressor... so a GT2871 71mm w/ 56 trim with a T3 .48ar exhaust housing?

do you think it could work or will the larger compressor wheel destroy all the spoolup benefits from the .48ar housing or do you expect some other big drawbacks of the compressor/turbine missmatch?

Goal is, good spoolup, good powerband but the ability to run more then 21psi of boost...

4SFED4 · Joined: 05 Apr 2006 Posts: 119

Some solutions are a compromise, some are less or not at all.

A twin scroll housing or pre-turbo WI have very little if any compromise.

Changing turbine housings is a compromise, one way or the other.

Pre-turbo WI will improve spool and give you a little more headroom, i.e. shift the compressor map a little left and a little right without compromising TE.

If you are happy with TE power now going to the .48 A/R will only decrease it. Whether you like it or not is up to you. The GT2860RS is a responsive turbo... how much more response or low end do you want and what size motor are you running the turbo on?

Techsalvager · Joined: 21 Jun 2011 Posts: 140

what form of motorsports or just for daily driving?

mrx · Joined: 05 Nov 2005 Posts: 486

Thanks for the reply.
Of course i know that there will be a compromise. Thats sure, but i think that the effect of the smaller turbine housing will be bigger then pre-turbo WI isn't it?

The engine is a 1,6 Liter engine and you are right, the 28RS is very responsive... but on some tight tracks i need a bit sooner spoolup... let's say 500rpm would be nice, everything more would be bonus and great as soon as it doesn't totaly ruin the topend. If i for example loose 10-20hp @ 8k i have absolutly no problem with...

Problem is, that at 8000rpm the 28rs is almost a bit over it's compressor limit at 21psi, thats why the 2871 compressor idea came into my mind... of course it's clear that it's a compromise concerning spoolup again.

Question is, how much Wink

Usage is Auto-X or tight tarmec rallye stages... mostly between 60km/h -> 160km/h 2nd and 3rd gear primary used... driving style is also a bit more rallye like, so i need torque (if you can talk about real talk from 1.6L - i know) midrange... that's why i don't care so much about topend and think that i can life with the compromise of the smaller turbine housing (ex. pressure). I did some dataloging statistics and they show that i work basicaly between 3k-6k most of the time, above 6-7k it far below 10% of a stage. This is also caused by my transmission gearing which i unfortunatly can't change. Sad

Techsalvager · Joined: 21 Jun 2011 Posts: 140

why not try some mild form of antilag?

4SFED4 · Joined: 05 Apr 2006 Posts: 119

Yah, either anti-lag or given how you use the car go with the .48. I think you will lose more than 20 on the TE though.

My first response when I read you only want 500rpm was to say change your driving habit... apply gas a little earlier in corner exit but since you are AutoX and rally... that is not really an option most times. You are looking for an on/off switch. Perhaps an Evo III 16g, twin scroll header and variable cams is your best answer? Or swap up to the 2.0 liter and keep the potato!

Good luck.

mrx · Joined: 05 Nov 2005 Posts: 486

Thanks for the input... what do you think (even roughly) how much will i loose topend when going form the .83ar T3 to a .48ar T3 housing?

Driving style i tried, but as you already saied, it's not possible most of the time. I also tried ride and tire combinations to get more cornering speed to keep rpm's up, but there's a limit in 2nd gear for example.

more engine capacity is not an option... first because of class regulations and second because it's a personal goal to get this compromise as good as possible with the 1,6L engine... and of course it's fully build and i have it already and they are cheap in case if something brakes...

Therealdrevil · Joined: 09 May 2011 Posts: 25

What about a .63 housing?

I just got hold of a Gt28rs for my car and swapped out the .86 wastegated housing for a .63 none wastegate housing.

mrx · Joined: 05 Nov 2005 Posts: 486

4SFED4 · Joined: 05 Apr 2006 Posts: 119

I misread your first post. You wrote .83 I assumed a typo for .63... but if you are running the .82 A/R T3 framed then I COMPLETELY agree with MRX, the .63 is the way to go and you will surely pick up 500 RPM and lose little if any TE with a GT2860RS. I would reconsider.

mrx · Joined: 05 Nov 2005 Posts: 486

You mean you agree with Therealdrevil !?

Warpspeed · Joined: 05 Jun 2006 Posts: 483 Location: Melbourne

If you only want a little bit (500 rpm ?) and you cannot change the transmission gearing, how about a change of tire size ?

mrx · Joined: 05 Nov 2005 Posts: 486

giskard · Joined: 24 Oct 2005 Posts: 251

Reports show that the 2871 loses a lot of spool over the 2860. If you want more spool with similar power you're out of luck with turbo selection. As for a/r housing selection, give ATPturbo a call. They have experience there.

Check out the upcoming GTX2863. Slight loss of spool vs 2860, with power close to the midsize trim 2871.

skylinegtrhr · Joined: 14 Oct 2009 Posts: 30 Location: Croatia