blown 944

Extremely fast.

VGT power strokes sound like little jet turbines at idle and the pressure out of the exhaust is strange considering they are only idling.

I would let josh know so he can keep your timing conservative for what you're doing.

One other option to make life a little easier is to make a turbo mount that lifts the turbo up using a manifold like dnovak's setup. You would have more room and access. It would however require a custom crossover but you'll need that anyway.

Thom

One thing I'm not too sure about with the QSV is gas flow as they enter the turbine - I imagine massive turbulence there with the flapper closed, as the cross section varies from the circular shape of the (single scroll) cross pipe to the brutally smaller and (relatively) rectangular shape of the turbine inlet.

This may create a fair bit more backpressure in the cross pipe than making a smooth transition from the cross pipe to the turbine inlet, for the same performance in spool.

Obviously the flapper opens as soon as back pressure reaches the point at which the engine is breathing most, so hopefully this shouldn't be too much of an issue in reality...?

Regardless, how bad would be the turbulence on the turbine flange with a single scroll mated to it directly?

blown 944

You'd want the flapper to open off of boost pressure I'm thinking. Backpressure would be too high for normal boost conttoller's maps. Turbulence shouldn't be too much of an issue as you'll want the valve opening at pretty low pressur or it'll overshoot and you'll be trying to balance two valves. With a bigger turbo I don't think it's as severe ie t66 or larger. But these smaller units with spool and spike much quicker.

IMO you really only want to use it to get the turbo "lit" then let the wg control map.

Thom

Yup, I may be splitting hair on this one.

Sid, how would you expect boost to build up with a GT35 with a T4 Divided 1.06 turbine housing with QSV on a 3.0 8V with stock intake/cam/headers?

On the DSM forum I read about Evo guys getting the same response with a GT35 set up in twin scroll as with a GT30 in single scroll - obviously they have the turbo much closer to headers than us, but it still sounds pretty exciting!

blown 944

I'd say that the DSM guys are hitting it pretty accurate.

Again, my experience with a t4 1.06 is that it is HUGE. So to be honest IMO (really my opinion from what I've seen) a t4 1.06 probably wouldn't spool until 4000 rpm using a qsv. I am basing this off of spool rpms using a .58 single entry and dividing the 1.06 in half. I tried a .96 and this was pretty accurate to what I saw.. Now this is with a Holset journal bearing turbo but with a .63 t3 I have seen them spool very quickly so again IMO it is a good comparison to a gt30 and 35.

If I were to pick a hotside for a 3.0 8v in a t4 configure using a gt35, I'd go for a .7ish t4 turbine housing. It would flow every bit of air needed when both sides were open and would probably hit 15psi around 3000 rpm or less.

Again this is from my experience with the hotsides I've seen. And I just looked at a gt42 1.0 ar and it confirms my sizing experience. The guys I work with sent it back or I'd compare it to a .82 gt2871 that is sitting on a ur head sitting ing front of me. Just an FYI, that housing was too big for a car they tune to run on the salt flats at around 800 rwhp. So if it's too big for them then I'd never use it.

blown 944

I was just looking online for a comparison photo and came across a vendor for gt35's

It looks like there are limited options in twin entry housings. All of the stuff I've ordered has been for p trim or stg 5. So there may not be the option I'd choose. I'll have to do some research tonight to see what the wheel size is and see if another size could be adapted. Considering I've adapted various Garrett hotsides to Holset turbos it shouldnt be too hard to adapt to s Garrett. But maybe .......

Thom

Thanks for your input.

I think I should probably review the intake side of things if considering a GT35. Even if I get the hotside right it sounds like a waste of a turbo with stock intake parts, just not enough exhaust flow to spool the thing early enough not to ruin streetability, and using a small A/R sounds counter productive on such a "large" turbo. I'm stuck with the ~8 Cr of Mahle pistons too.

A friend runs a pair of GT35 with 1.06 A/R single scroll turbines on his 5.7 GM block, turbos right after headers, and he mentions he is beginning to see boost no sooner than 3k rpm, which goes in line with what you are saying - lots of lag, even if he runs with a super aggressive cam, high CR.
Obviously a 5.7 small block may hardly feel quite as torqueless as a 951 engine off boost, so making a straight comparison remains pretty hard anyway...

blown 944

just to add a little info.

I was looking into differnt sizes and it looks like a stg5 turbine housing could be machined to accept a std gt35 turbine wheel pretty easily as teh size differnce is 2.46" for the gt35 and 2.43 for the stg5 wheel. The gt 35 inducer is just slightly smaller so it will fit easily.

here is another interesting find

for those wanting to continue to use the stock crossover this may open up a few options

Thom

If I'm not mistaken Vic at Pauertuning runs such a K24/K26-flanged Garrett turbine housing on his GT3076R, but he still had to have the cross pipe modified as the GT turbo will sit, if using the ATP mount on the stock engine mount, about an inch ahead of where the standard KKK turbine will usually sit.

Even if the stock cross pipe needs modifying, to me it still looks like a good idea as a downpipe that works with a KKK turbine housing may be reused without much modification, just have to add an appropriately-flanged intermediate pipe between the turbine outlet and the downpipe as the 4 bolts should be offset the same. Or cut the downpipe and weld the missing straight inch of tubing inbetween the downpipe and the flange so that the downpipe flange can be reused. Just thinking out loud.

On a 3.0 engine I feel it might be more appropriate to use such a KKK-flanged Garrett turbine housing with an A/R of 0.82 instead of a 0.63 though? (these being the two A/R available from ATP for this KKK-flanged Garrett turbine on a GT35)

ATP and Garrett mention a turbine wheel diameter on a GT35 of 68mm = 2.68", which may require a fair bit of machining to open up a St5 turbine housing.

pole position

Going to a KKK replica is a step back , or better, a couple of steps back IMO. Modifying the down/crossover pipe is really NOT that much of a deal, you can V band at the up section of the factory crossover to the turbo and one needs a 3 inch downpipe anyway with a turbo of this size so a little more fab work there. Ideally a new crossover with a a proper merge collector would be the way to go but the factory piece if not collapsed is pretty good.

Now back to the KKK stuff , this http://www.atpturbo.com/mm5/merchant...egory_Code=TTH or KKK ? LOL.

Thom

Sorry - in reply to Sid I was talking about the KKK-flanged Garrett turbine housing.

Discussing turbos sometimes requires such wordage that it's not hard to get mixed up and forget essential terms.

KKK turbines are not that bad actually, I run one on my custom hybrid turbo and for boost pressures below 18psi it doesn't seem to hinder street performance too much. I think a 2V engine would require major intake work to run more boost pressure on unleaded without knocking itself apart.

pole position

I understood that we were talking about the KKK garret flanges but pair the Tial housing with this http://store.forcedperformance.net/m..._Code=Turbo-FP.

Expensive, sure , worth it on a 3L with a stand alone, yes IMO.

blown 944

Thom, in regard to size the stg 5 is 2.79 and the gt35 is 2.68. So that fits easily. Idk about the other fitments. I'd never use that stuff anyway.

Actually I'll never use a gt35 really. I love these holsets, they are very tough, and rebuild able. The hx 35 7 blade can flow 60# s and with the billet wheel, even more. Using anti lag , spool doesn't matter as much and with a decent intercooler top notch efficiency isn't as critical. However, from what I've seen by helping design Dave's turbo, these things can spool crazy fast with a .63 garret hotside.

I also try to use trap speeds as comparisons on similar setups and my 40/35 seems to do fine. I talk to a Subaru guy pretty regularly when I go up and with a gt35 he is trapping just over me.

My next setup will be a full super40 using a .58t4. I've used a similar setup before with a slower spooling comp wheel and I had full boost by 4000 rpm with crap tuning. This should allow for better top end. Also with the larger engine it should spool by 3500.

My goal is to trap 130 but I'll be happy with 125.

pole position

Trapping 130 at 9000 ft elavation would be quite a accomplishment, weight reduction ,500+whp, dragradials and good driving might get you close. That would be high 130's at sea level......for a street car that is very,very fast.

blown 944

It is a bit more difficult up here. Most have to use a larger turbo, which is a double whammy on spool and drive ability.

I think my best trap could have been over 120 if the clutch were working proper. At the end the mph kept sliding down a little compared to the eigth mile.

We'll find out what it can do. Plus there are a few more that will be going up.

What I really love about playing with this platform is that what I do with it is not really where it shines. When I come across high dollar cars on the highway it is much easier to run them down. I havnt found too many that I can't keep up with

I've seen a couple cars trap 134 with my same turbo up here so it can be done. I just need a head that can flow it.