Greetings from Toronto, Canada. I have a question regarding turbo selection for my turbo k series setup. youll have to excuse my newbness to the FI game, this is my first boost setup as ive only fucked with all motor setups before with pretty good luck.

The motor setup i have is a 2.1L darton sleeved k20a2, 9:1 comp with a built head and brian crower stg 2 turbo cams. I'm using a sheepey built sidewinder t4 twinscroll with dual tial mvr 44mm wastegates. oem fuel tank with aeromotive 340 lph and -8an lines and braided line replacing the steel units. precision 1000cc injectors, aem series 2 standalone and custom fabricated piping and ic.

the car will be mostly a highway stalker with it seeing some strip time (limited due to a stock 4.4 a2 transmission with only cryo treated gears and kaaz lsd).

im aiming for mid 500 around 20 psi with a 3.5 inch exhaust on pump gas, and later on i will tune the car on c16 at 28-30 psi, aiming for 700.

my first turbo i wanted to purchase was a garrett gt3788r bb twinscroll with a 1.11 turbine a/r. i was yold by our supplier that the 1.11 and the .99 a/r turbos are discontinued and hard to find, leaving me with the smaller .89 a/r size only. also considering a precision 6466 bb with a t4 divided flange and 1.15 turbine a/r.

some of you might be wondering why i chose a t4 frame setup and looking at quite large turbos. room to grow my friends.

anyway, just would like to hear reccommendations, thoughts, criticism, personal experience with either turbo and generally anything that could be constructive.

cheers!

 

My .02

It sounds like you have a pretty built up motor. If I were you, I would start by shooting for 10:1, unless you've already done the pistons, rods, crank. I would suggest to run E85 as getting mid 500's on, at best 93 octane, is a bit risky. You'll want the GT37 series to see that power, maybe larger, and since its so big, sticking with twin scroll would be a good way to go.

 

I forgot to mention the motor is finished already. And by pump gas i mean 94 octane. Thats our highest oct available in toronto, unfortunately we dont have e85 readily available here.

 

In that case. I would go bigger than a GT37 with only a 9:1. So you'll just have to get a good tuner, still shouldn't be too terribly much to ask to get mid 5's. I would have considered dual 38mm wastegates for a little better response, but I'm guessing that's already done too :lawl:

 

GTX3582R, 6766, etc...

 

I dont beleive they make the gtx turbos in a twinscroll t4 divided housing, and i think the 6766 is a little bit overkill. Im really leaning towards the 6466 but im just worries about longevity, the garrett is water cooled whereas the precision doesnt have such an option. But i dont know if that should even be a concern, im not planning to circuit the car or anything

 

Precision doesn't compare to garrett. The gtx series doesn't come in twin scroll, and 35 is too small anyways. A GT37 with a T4 twin scroll housing is the only way to go, IMO.

 

Actually they do come in divided housing. You simply need to call a Garrett dealer to have that put on. (none of which either of you are describing is considered to be a "twin scroll", but I won't get into that right now.) and there is the GTX series that is slightly larger than the GTX35R that would make th power levels you are requesting.. Not sure where you guys are looking.. But the divided housing will not help your responsiveness the way you think it will..

 

Would you mind pm'ing me and explaining twinscroll theory a little more in depth?

 

99% of turbine housings aren't true twin scroll, just simply divided.

On a divided housing each volute isn't totally separate from the other, there's just a divider that runs down the middle that tries to segregate gasses as long as it can

A true twin scroll has two completely separate volutes until it reaches the turbine wheel

 

I never said divided. I said a legitimate twin scroll housing.

 

Oh i see. I didnt know that about the housing and the length of individual exhaust gas channels within. That being said, with the turbos that i'm looking at, full boost wont be realized until 5k rpm or better especially with the 1.0 + a/r ratios that im selecting.

 

He said 500hp on pump fuel, and 700hp on C16... The GTX3582R will do that, no problem.

And you're right. Precision's don't compare, because they fall apart unlike the Garrett's.

 

Whoops. Missed the part about race fuel.

OP: why not just go straight to race fuel?

 

No Garretts are true twin scroll, just divided

The only one available right now are the Borg Warner EFR turbos

 

I knew this question would come up sooner or later. Yeah, i thought about it but the price point makes it unbearable as i still want to drive the car when i have free time (weekends only) and maybe participate in some non sanctioned street activites.

Race gas isnt as cheap up here and is quite expensive unless you buy a 55 gallon drum. Now, ive got money but not the type that burns a hole through my pockets. Our sunoco 94 does the trick. Its just like american 93 but with a little higher percentage of ethanol which ups the octane rating. The car will be retuned on c16 once the competition season starts in may. I think itll take me quite a while to get well acquainted with a big power turbo setup regardless.

 

Are you sure?

I was fairly certain the ones they advertised as twin scroll actually were separate volutes. If you are correct, then I'll have some thinking to do haha

Sounds good. Best you can do with the lack of E85

Have you considered a meth/water injection on top of the 94? They're pretty simple and cheap to run and will go right over top of an existing tune with vitually no interference.

 

Let me guess, an advertisement from Full-Race? No, they are not twin scroll and are simply divided housings, but they use the term (started about 2007) to help with marketing campaigns. They now have REAL twin scrolls from the EFR series. That and the OEM Mitsubishi Evolution turbos have them. Not the T4 stuff from Garrett.

 

That is quite interesting. Thanks for the correction!

 

Id go S366 ETT, im a firm believer in borgs

 

Funny you should ask, i just sold the aem water/meth kit i just had. Since this is my first boost setup i just want to have the car running properly and tuned, dialed in so to speak. At which point my next purchase will be a ppg gearset. Im not to concerned about meth injection just yet. Ive installed a couple in customer cars, but i dont feel its really necessary at this point.

 

Ill definitely do some research on the s366, ive heard of this model many times before. Its from their airwerks line correct? As in, its not an efr turbo? What was your setup and power/boost figures like?

 

Its not an EFR, they are still having casting issues with the turbine housings for most of the EFR models, I'd wait till they get that sorted before committing to an EFR.

Borg and Garrett are all solid choices, I would look into holset turbos as well, over built solid turbos, used on dodge Cummins diesel motors and various other diesels, DSM ad Honda guys love them... the bearing systems are tanks, they go 500,000 miles on over the road diesels without issue... I've also seen people run them without oil and they still won't die

An hx52 or hx55 would also be a good, cheap choice... and they have divided turbine housings as well.