GT35R or GTX35R

[VRX]

Hey all,

I've spent hours online trying to get a definitive answer on this but to no avail so i thought i'd see if anyone here can help me make the right decision.

I'm in the middle of having a forged engine built for my 05 manual FWD magna a Mitsubishi 6G75 3.8l taken to 3.9l,a compression ratio of 8.5:1,balanced,headwork,HD springs,264 cams etc etc.

Originally i planned on using a supercharger running 12psi but i've decided against that and am now going single turbo,I just can't work out which turbo i should use the GT35R or GTX35R and which turbine housing .82 or 1.06.The 6G75 isn't a big revver so the limiter will be set in the mid 6's.The car will hopefully be setup to run dedicated LPG.Power will be capped at 400HP@wheels and i'd like the turbo coming on strong in the low to mid 2's.

So what i think my options are correct me if i'm wrong:

GT35R with .82 housing = responsive but may choke top end.

GT35R with 1.06 housing = a fair bit laggier but won't choke top end.

GTX35R with .82 housing = very responsive (possibly to responsive) might not restrict top end as bad as the GT35R with a .82.

GTX35R with 1.06 housing = moderately responsive with very strong top end.

*Turbo will most likely not see more then 16psi.

Also could anyone recommend what size external wastegate i'll need and what brand.

Cheers in advance.

[magic1]

GTX35R with .82 housing = very responsive (possibly to responsive) might not restrict top end as bad as the GT35R with a .82.

i would go with this 1

GTX35R with 1.06 housing = moderately responsive with very strong top end.

this will put a massive strain on an engine that is not really supported in the after market

[karnage]

with the new gtx series you can get tial specific rear housings for a tial wastegate. You should talk to Tengoku Imports (search them on facebook) as they bring in GTX turbos and know a reasonable amount about them

[Alt_F4]

GTX35R with 1.06 housing = moderately responsive with very strong top end.
+1
Look at the barra guys, they get gt35s with 1.06 sized turbos at moderate boost from factory.
Bear in mind this turbo will be good for over 500hp with healthy boost (you said you wanted 400hp), so take that into account when you make your choice.

[Madhav]

What is the problem with a turbo being too responsive? A lot of people told me that my turbo would be too small and would be too restrictive and would surge etc and this turned out to be all hearsay.

If you are aiming for 400whp max, depending on what boost you plan to run, I would say that both are too big. The GTX30 series are more suited for that power level. But then again if I were you I'd be asking someone like Tristan at WTF autos as he is very knowledgable about turbos and proper sizing, having experimented with every possible combination over the years on various cars.

[Yakky Bear]

gtx35 with a .82
call glen @ mtq and tell him your application and the turbos you are thinking of using.
he will tell you straight out whats the best combo is to use.

[zeroyon]

Power will be capped at 400HP@wheels

GTX3076R with 0.82 rear, easy do your power requirment.
Rated @ 640hp FW.

If you insist on going larger then gtx35 with .82 rear.

[azzada1]

On the built v6 i would have thought the gtx3076 with the 1.06 would be the go

[Miggy]

If you only want 400hp go with the .82 if you think you will want more power later on go with the 1.06.

[VRX]

Ok thanks all for your input.

Jezza from Tengoku Imports did get in contact with me and from the calculations he has done the GTX35R with .82 housing seems to fit the bill nicely,with the GTX30R being to small for topend.

Mahav - ''What is the problem with a turbo being too responsive?'' I'm concerned that at low throttle inputs in 1st and 2nd the car will have erratic drivability which could result in unwanted wheelspin especially in the wet.

One other issue i can see with the GTX30R is the extra boost i'd have to run to make the power which would be a problem with the LPG injectors as they only seem to take about 22psi before the pressure differential causes reversion of the gas.

So with the GTX35R running lower boost to get the same power i'll have some head room with the injectors and the compressor if i decide to chase more power.Please correct me if my theory is way off lol

[Madhav]

I would not recommend driving high powered turbo cars fast in the wet, no matter what turbo you have.

The turbo I have on my current setup is very similar size to the gtx30r, plus mine has the .63 a/r on it. It makes power all the way to redline. You can tune the car so the power comes on smoothly, less wheel spin.

I think if you speak with anyone here they will tell you the less lag and more powerband to play with the better, especially if you are not going to rev it much past 6k.

The 35r can make more power later on if you decide, yes, but take the gtx30r to 22psi and I'd expect 500whp from it.

[duste]

Just for a bit of insight, according to my rough calcs (assuming a lot of variables - 12.0 AFR, 50degC, 92% VE, 0.55 BSFC):

400hp@6000rpm: 11-12psi
500hp@6000rpm: 17-18psi

The pressure ratios and required air flow sit nicely inside the compressor maps I found for both the GTX3076R (though it does get in to the low 70% efficiency region at 500hp) and the GTX3582R (stays very close to the high 78% efficiency region for both 400 and 500hp), so it's really up to whether you want response or lag - and you'd be stupid to not want response. This is all purely theoretical though so obviously things could change in practical use.

Does your ECU have some form of launch control built in?

[VRX]

Some good points there guys,the GTX3076R is also a few hundred cheaper at $1740 including housing delivered :)

Duste hopefully i'll be using a Profire ECU but i don't think it has launch control however it does have traction control.

[Lump]

traction control, sounds like your gunna need it lol

[VRX]

lol yer most definitely.

[eaglesfandavid]

hey mate where are you planning on buying your turbo from?
i would suggest you shoot Paul from http://www.streettotrack.com/ an email he quoted me a much cheaper then $1740 for a GT35R because he imports them from the US.

Also consider other brands and options such a turbonetics. I did and ended up choosing a T66 from him instead for a very good price, way better price than the GT35R just not ball bearing, worth a thought.

[VRX]

Street to track is where i'm getting it from,$1740 is for the GTX3076R.

[Turbo2.6L]

GTX3076R with 0.82 rear, easy do your power requirment.
Rated @ 640hp FW.

If you insist on going larger then gtx35 with .82 rear.

^^This!
A 30 frame turbo, especially from the GTX series, will shit in 400hp with 16psi or less on a 3.9L engine. Will also give great response (which is most definitely what you want on an engine that doesn't rev hard) so win win!