Let's Talk Turbos!
 

Since I'm on vacation this week, I'm shopping for engine parts to get my car back together. Since my turbo is el kaput, I'm thinking of going with a Perrin rotated kit... GT3076R. But I'm not sure what AR to pick... .63 or .82. Hell, I don't even really know the difference, other than the .82 is supposed to spool about 400 rpm later, but what are the gains? All I know is that I want 350-400 awhp on race gas, with full spool before 4500 rpm. But most importantly, I want good throttle response and good even torque between 4000 and 6000 rpm where the car will spend most its time at the race track.

So, let's talk turbos. I'm pretty sure I want the GT3076R, but if anyone else has some different opinions (like the GT3071R or GT3582R... or something non-rotated, like the GT52) I'm all ears.

http://memimage.cardomain.net/member...1_144_full.jpg

Twin Scroll I believe the turbo is a GT40r
http://forums.nasioc.com/forums/show...1251701&page=6

Yes, I know there are twin scroll setups out there. Full-Race makes a GT3076R twin scroll kit... but it's $2000 more than the Perrin GT3076, and sure there's some great gains in response and spool with the twin scroll, but not at nearly twice the cost.

I have dyno charts of both the .63 and .82 GT3076R on 100 octane on GST's dyno, I will post them tonight. If you plan on doing autox at all and you want to go rotated I think you will be choosing between the .63 GT3076R and the .82 GT3071R (I don't have a chart for this one).

If you don't want to go rotated I have become a GT52 fanboi, I will post my chart up later as well :)

Is that the Subaru "fully independent fuel system?" :lol:

I was gonna say twinscroll but yea they are stupid expensive and Nick beat me to it. Alot of the evo guys make over 400 on the 3076r on pump + meth.

From what I have read though I agree with MikeK on the .63 AR > .82

Since the motor is apart though, why not go with a stroker kit and the .82 :devil:

Quicker spool on the .63 with less top end. Little later spool on the .82 but better top end.
On a track with proper gearing I'd opt for the .82. For AutoX/street combo I'm on the fence.

Sounds like I need to look into this GT52.

EDIT: also the .82 will be more efficient and might tolerate more timing/boost.

GT3076R .63 100 oct

GT3076R .82 100 oct

GT52 100 oct

That GT52's numbers look good... but be careful comparing dyno charts of cars tuned 2 years apart when the boost and supporting mods are not listed (not to mention ambient temp, etc.).

If you go rotated then GT3076 w/ .82A/R for track use.

Like people are saying... the GT3076 w/ the larger .82 AR seems to be the way to go for a track car that's going to be running 100 oct. It's not like I'm worried about autocrossing the car, and at the track, I'm between 4000 and redline in gears 3-4-5 pretty much exclusively with the 6MT.

The GT52 though does seem to be a damn nice turbo if you're not willing to go rotated... especially if you're running alky injection, or if you're streeting/autocrossing the car... in fact it's probably better than the GT30's handsdown if you're not building the car specifically for the track.

I am definitely no help with Garrett Turbos. I have been on their page to try and understand their numbering and lettering for turbos and I'm still lost on it. But allow me to introduce more abstract and most likely pointless ideas. Element Tuning has been doing great with some of the Time Attack events.

Its basically a 20g, but the have pulled some great results out of their STi.
http://elementtuning.com/Turbocharge...bochargers.htm

Its probably just a Garrett Turbo with an Element Tuning sticker on it and marked up $300 bucks, but I'm trying new ideas :lol:

Just wondering, but would you benefit from some sort of Meth injection or do you already have it?

gt52 would hit your goals i think and be alot cheaper than other options.

i think i know somewhere you can get a mildy used one cheap.

;)

A 20g turbo is a Mitsubishi turbo, not a Garrett... they're the factory WRX turbos:

TD04-13g = stock WRX turbo
TD05-20g = turbo on my car right now
TD06-20g = the most popular Mitsu turbo for the STi right now

Then there's the IHI turbo line, which are the VF's:

VF22 = the original "big" turbo for 2.0L WRX's, I think it came on the original STi
VF39 = the stock STi turbo '04-'05
VF42 = the stock STi turbo '06-'07
etc.

And the Garrett turbos are GTxxyyR, where xx is the frame size, yy is the compressor wheel size, the R on the end means it's a ball bearing turbo.

So the GT3076R that I'm looking at is a GT30 frame, with a 76mm compressor... and I'm looking at the .82 A/R, which is Area/Radius, and it relates the size of the housing to the size of the compressor or turbine. Since A/R on the cold size isn't very important, when people are talking about AR's they're pretty much always talking about the hot-side turbine A/R. In general the larger the A/R the more flow the turbo will have, but it will also have more lag.

So basically, this thread is really about what hot-side A/R I should be picking for a GT3076R turbo... MikeK posted some dyno charts of the two turbos, but like Matt said, without knowing the details on the two cars, it's hard to make a comparison. All I know is that the .82AR seems to peak only about 250 rpm later than the .63AR, and since I know it's a much more capable turbo at higher boost on 100 oct, I think taking that 250 rpm hit is probably going to be worth it overall.

But back to the nomenclature, the GT52 is a misnomer, since it's actually a GT30R with a 52 lb compressor... since it's not actually made by Garrett (it's just made of Garrett parts) it's received a name for marketing purposes.

Are you really getting rid of it?

If the price is right, I'd probably go for it. I don't want to drop $1000+ on a new 20G, and for around $1000 more than a new GT52, going GT30R rotated sounds worth it 'cause the EWG is supposed to be more responsive and the turbo does really well on race gas... but a well priced used GT52... now that's not something I expected to find.

How much you thinking? PM me!

20 psi before 4k and 375-400whp sure does sound nice

Thanks Scott, I knew about the IHI and Mitsubishi turbos. I thought that 20g was just a name for a certain sized turbo, in reference to the compressor wheel, not Mitsubishi specific. Thanks (BTW the 06-07 STi turbo is a VF43).

So what is your stance on Meth injection?

How about the new ATP turbo GT30r none rotated? I would venture to guess the GT3071 would make a nice little track turbo. We run the GT30r on our low compression motor and running 104 octane gas have it set at 420whp on it's full tilt map (the car can make more than this 30-40whp more but it's dialled back to last)

Personally given your setup and goals I would run either the rotated GT3076 with a .82 or the none rotated GT3071 .82 (ATP turbo) and clock the intake manifold and have someone shorten your IC piping, instant better throttle response and a significant gain in spool up.

Mike

Scott, please don't use meth on a tracked car!

Mike

Why is that? I was just wondering if he would benefit from it at all. I thought it would help him make that power and be able to run a smaller turbo.

I have yet to see an adequate reservior/pump pickup that would make me feel comfortable to being used in the high G arena such as track Auto X use, changes in flow due to inconsistent delivery would make me very nervous.

Mike

Oh, I didn't consider the thought of a slosh effect in a tank or anything. But what about the fail-safe systems of the Aquamist Package?

Like Mike said, I have a hard enough time with oil and fuel at high-G's, I don't need meth too. Plus, meth injection is illegal in SCCA (though water injection is legal... I tried that and keeping the system primed and working at the track is a headach, especially when you get more gain just from running 100 oct).

Which reminds me, I've got a full Aquamist 2D system with a spec-C tank if anyone wants to go to meth injection that isn't tracking their car. :)

Back to the turbos... I didn't know about the non-rotated GT3071.82R. That might be a decent option... but it depends on the cost. If it's in the $2000 range, I might as well just go with the rotated setup. Since I'm MAP based, it would be nice to run a big-ass 4" inntake from the fender to the turbo and not deal with the smaller inlet hose. The only reason I'd stay with a stock turbo location is if I can get a deal on a used turbo like dayofpain's which is an adequate turbo for my needs and has low mileage on it.

The drop in GT series turbo's are around $1700. Personally I think with the fact your speed density I would stay with something with the larger intake and keep the intake flow to a maximum. I would still rotate the intake manifold for the response gains.

Mike

How hard is the intake rotation? Just a matter of bolting it on backwards, routing the throttle cable, and re-plumbing the cold side of the intercooler piping?

I think the biggest headache is dealing with the A/C but I don't think you have that problem :)

To bad you have to deal with the throttle cable though.

Throttle cable is just a bracket not such a big deal, also a bracket to relocate the alternator as if I recall you don't have AC.

Intercooler piping is not a huge job either just requires some mad TIG skillz y0..

Mike

I hate to argue the rotated intake manifold thing, especially with Mike advocating it... but how much IC tubing length does that save? What - 2 or 3 feet of 2.75"OD tubing? That's about 200 cubic inches (or about 1/8 cubic foot) of volume. How long does it take for a 400whp turbo to pressurize 1/8 of a cubic foot? That would be the gain in response. 400whp is say 500bhp which is about 500cfm or 8 cubic feet per second for a whopping 0.015 sec reduction in response just SWAGging it. I dunno - there must be something I don't understand. And running speed density (or BTM) there is not the lag time between MAF reading and induction into the cylinders either - that's the thing I don't like about FMIC and its long tubing along with draw-thru MAF.

I can only offer what we see on the dyno which on the same car shows to be a 200-300rpm difference depending on gear and load, also the transient throttle response is greatly improved. This is based off a GT30r running a Hydra tested same day.

Depends on what's worthwhile for people I guess, from a racing standpoint where rule restrictions are in place I'll typically take it where I can get it and with it being a none to costly or timely modification it just makes sense to make the efficiency where ever you can.

Mike

I would guess it is due to fewer total degrees of tubing angle and thus turbulence in flow that makes the difference, not so much tubing length.

I think you have to factor in the fact that the whole system is feedback driven. If the turbo were simply spun at full speed by some outside force then you'd have a marginal improvement. But if you need to make exhaust to spin the turbo to make the boost to make more exhaust....I can see where there would be more benefit. Especially when going from no boost to full.

That's excellent info - no doubt. I just wish I understood the "why?" better. And is that both cold and hot sides changing when rotating the manifold?

This is a good point.

Yup no doubt, it's a total efficiency thing.

Mike