Porschefile

I wasn't implying they are somehow inferior. Technically speaking, if a large turbo manufacturer would implement that technology on a wide scale in a majority of their turbo lineup, then technically it would work great and probably end up being superior to non-vgt stuff. You'd have a huge variety of wheels, housings, etc to choose from to more accurately size a turbo for a specific engine. As it is now, this does not currently exist in the current vnt/vgt turbocharger market. All you have to choose from is some turbos with hotsides oriented mainly towards large displacement low revving engines. Because of that, by default you are starting off with some big compromises. Due to the added complexity, cost, and relatively small potential market I honestly don't see VGT-based stuff making a huge jump into the aftermarket, at least not any time soon. The technology is great, it just hasn't reached the public in a realistic manner yet. Hell, I think it would be great if they would expand on this further. Can you imagine not only VGT but say VGC (variable compressor)? Imagine having a turbo that can spool up nearly instantaneous to full boost pretty much off-idle. You'd have B16 Hondas putting out pushrod torque curves!

gt37vgt

yeh but it appairs i can use standard medium frame compressor wheels and hopfully overcome the sizing comprimise i'm looking at

Porschefile

I'm honestly not trying to rag on you dude but, you mean small frame right? You realize mid/medium frame means actual T4 turbochargers, right? T4's are only necessary for diesels and stuff over ~550-600+whp in general. How much power are you looking for? If it's over 600whp, then yeah you could probably figure out a way to make a vgt/vnt T4 oriented turbo work, though in the end there's the possibility other stuff like a twin scroll T4 might work just as well or good enough and could be a lot easier to implement. Honestly, not to rag on anyone here but the T4 setups I have seen on some people's cars here have produced some pretty lackluster results. Hell, even ST has yet to exceed the power capabilities of the T3 frame Gt35r. T4 = built everything and lots of boost to make lots of power, otherwise it's just pointless and = waaaaaayyy more lag than you need. Sh*t this is why I constantly whine about getting some of you guys to look outside of this community to see what others are doing, to avoid wasting time on useless or wasteful stuff. This community isn't anywhere close to the cutting edge. Sorry but, that's the truth. What people have been doing here is largely stuff done 10-20yrs ago in the whole Japanese scene. The fact very few if any ever attempt such a project in other communities should be an indicator that it's not very realistic or probably doesn't work out as well as you might think.

gt37vgt

wel i'm obviously confused about this small medium large frame business i'm calling the gt35 med and 37 large frame according tto the turbobygarret web page my gt35 appeears to have t3 flanging so i can imagine how it relates to a t3 but i've just been told i cant use the gt28rs compressor wheel as there a different shaft size some else told me i can use a 60-1 but i want the later gt 3076 .
so get out your track suit carboard and a didas and break it on down

Porschefile

Oops, I see what you mean. Sorry about that. Looking at Garrett's website, looks like they call anything T3-based a medium frame turbo. I'm used to seeing T4's as medium and T6's as large, but they just kind of group them together. Once you see a T6 frame turbo in person (biggest I've seen is a Gt47 on a ~1500whp local drag Supra running 7.81's), I guess everything else is kind of small-framed! lol Anyways, what type of Gt35 do you have? Is it an actual Gt35r (Gt3582r), or is it the non ball bearing Gt3571? Link If it's the Gt3571, that's really a pretty bad mismatch as it comes with a 1.18a/r hotside, though with the wheel mismatch it's only rated to 390fwhp. For the power level, there is much more responsive stuff out there. As for the Gt28rs (Gt2860rs), it's a bit small and not really well matched to the displacement of these motors. It would work just fine and be super responsive. It's somewhat comparable in size to a K26/8 IIRC. 60-1's are old school wheels and pretty inefficient these days compared to their size. They work just fine and are cheap, but there is much better stuff available. At least T3 60-1's are pretty darn cheap and can still make plenty of power like over 500whp. For say ~$600-700 new from plenty of places it's really not that bad of a route even if there is better stuff out there.

Is price a concern? I mean, technically $1-1.2k for a GT30r isn't that much more than most turbos but, if you're on a budget I completely understand trying to find cheaper routes. If price is the concern, I'd highly recommend something from the Precision Turbo SC series t3/t4 lineup. Here's a few links: Link 1 Link 2 They are typically ~$700-900 US, made off of Garrett parts (PTE makes their own housings), and you can get a ton of different combos. If you want a Gt3076r, PTE's SC34 series is almost an exact match in size, performance and power output though it's not ball bearing. The SC34R series is ball bearing and pretty much identical to the 3076R but they're ~$900-1k. The nice thing about them, and probably the main reason I'd recommend them is there are a million options for different housings, wheel combos, etc so somewhere in their lineup you can find a close to perfect off the shelf turbo for your goals. All my whining aside, at the end of the day whatever works, works.

gt37vgt

i've told you 3 times its a 3571 but .81 vgt hotside so why do you call it a miss match? big turbine ? its not that big as i said 13% bigger than a the gt 30 . big hot side? well mines .81 vgt ? i think it needs i step up in compressor wheel and its fine. think i have it figured out if it works good on the 2.5 with ok exhuast back presuure I'll put a 3582 or 3076 in the front of it for the 3.0 and if its all crap the car will have a garret t3 mounting all done and i can bolt in a bbgt3076 .
if the time comes and the car is all cool accept the turbo yeh i will happy thow 1100 bucks at a nice bb turbo but if i can prove this 35vgt i will just spend up on a compressor wheel .
its still not clear wich compressors will go on it .

gt37vgt

hmmm on the tech page for 3571 there is a comp wheel / cover option of 54.8 /76 mmm one would hopet judgeing by size that would fall in between the 2876 and the 3076 and hopfully produce 50lbs of air I
'l start asking around

Porschefile

The stock 3571 basically has a Gt35r turbine and 2871r compressor. I keep saying it's a mismatch because the turbine is primarily what affects spool. While the smaller, lighter 2871r compressor (compared to the 35r compressor) will help in spool a bit, that 35r turbine is still going to cause a bit of lag relative to the power level that turbo will support. The optional compressor appears to be similar in size to a Gt3776 one.

I must have missed that, sorry. A .81 hotside isn't nearly as bad as a 1.00+a/r, though it's still overkill for 400hp. Here's what I'm getting at though. You have a turbine and hotside which are ultimately capable of flowing 600+whp worth of air (hell, .81's can support over 700-800whp), but you only have a compressor that combined with everything else can only flow ~400hp worth of air. You are going to have a much laggier setup than you might be thinking. Do it if you must but, I don't think it's going to turn out quite how you expect. To give you an idea, a Gt3076r w/ .63a/r hotside on 2.4l and 2.5l i4's typically will make 1 bar by ~3-3.2k rpm and can still support ~450whp, maybe a bit more. A 3076r w/ .82a/r will typically make 1 bar ~3.4-3.6k rpm and can support ~500-530whp. Even with the smaller .63a/r hotside, the 3076r can support more power than this 3571, and honestly I don't see how the 3571, vgt or not, will spool remotely that fast. On a 3.0l, you'll get some pretty insane spool with the 3076r series. Heck even a Gt35r would spool quick enough on a 3.0l. Sorry man, I'm not trying to knock your ideas. I'm just trying to point out that you'll likely save a lot of time, money, and effort going with an off the shelf turbo as opposed to the custom route, and you'd probably be happier in the long run.

As for compressor wheels, AFAIK you can't just buy GT series wheels. I've never seen them sold separately.

gt37vgt

so i think i've got a 3576 /3776 compressor lined up so I'll then have 500hp compressor and 600 hp hotside it kind of depends at what vane position the .82 is if its minimum maximum or average. so we may aswell stop talking exhuast A/R
so its one turbine bigger than the 3076 wich will make boost on a 2.5 @3k so on the 2.5 yep i'm looking at 3500rpm yep laggy but then you say the gt3582 will be better it has the same obease turbine you been raggin 68mm gt35 so why would that work ??? it it beceuse it would supply 30% more air at 50 000 rpm ?
you have certainly talked me down some what i will compleatly abandon and ideas i had for the gt3782.

it seems your saying the increased inertia of the larger turbine will be my problem ??
and perhaps the lack of compressor flow at lower turbine shaft speeds ??

so it realy comes down to between the 3576 and 3582 for compressor choice for the 3.0 i always thought the the size of the 3582 would make it less reponsive remeber the V is squared in the MVsquared equation?
and the 76 or 82 determine the magnigtude of that V.
but i realy don't mind the work and it is costing me very little money

Porschefile

If you are able to get a hold of a 3582 compressor, I'd do that. Then you'd basically have a 35r vgt. On a 3.0l, a 35r or something similar sized is still plenty responsive, though it might be a bit overkill if you are only looking for say ~400whp. Also, one thing to consider is surge. Does the turbo have an anti-surge housing on it? I'm not too sure how it would turn out but, with the vgt hotside you could potentially run into surge on the low-end.

I wasn't saying the 35r would be more responsive. All that I meant is, for how much power that combination might make, it might be a bit too laggy compared to something a bit more properly sized. Either way, a 3076r covers the 350-450+whp range pretty well and is about as responsive as it gets short of a twin scroll setup or something. IMO, if a turbo is making full boost before ~4-4.2k rpm, that's not really laggy. A bigger turbo like a 35r on a 2.5l will still make 1 bar ~3.7-4.2k (depending on .63 or .82), which isn't that bad.

George D

Garrity at Motorsport in SLC has done VGT's on 951's. We decided to not do this on my project for many reasons. He has made them work on our cars. If you are interested in his results, PM me and I will give you his number. It's not cost effective yet, but in a few years things will shake out and be available for many cars, including ours, at much more reasonable prices.

I'm going with a full garrett BB setup until the R&D is not at my expense.

George

gt37vgt

hmmm the most cost effective thing has to be a gt28rs putt into a kkk hotside those disco potatoes arn't the best turbo but they sure are good and there is so many of them they can be had for as little as $500.
my set up will cost me 500 from second hand turbos but if you were to cost out the work i'm doing to make it happen i can see how its not cost effective . I'm doing custom oil drain on engine mount all the turbo plumbing has to be done . and then to control the vgt that is an open cheque at this piont . and i'm sure i'll send plenty of time and money trying to get the egts down .
just so i can hopefully come back to brag to a bunch of guys I may never meet about how i got 3psi of boost 500rpm sooner than the guy with the bb turbo .lol