Geneqco

From what i understand, once they exceed I think somewhere around 150 - 160,000 rpm they self destruct - so i guess correct sizing is paramount.

gt37vgt

that is stratospheric rpm in any device and i gues they would perhaps see it as there is often no waste gate and a clearer flow path through the turbo with the vans open . .
other things often stop us ever seeing such rpm like waste gates electronic blow offs set to 24psi or just exhust back pressure capping engine performance

Geneqco

They say the problem arose as people wanted to get more out of them than they were really designed for - those early ones were quite small units from what i understand.

They say if that threshhold is exceeded due to incorrect vane control, the current units will have the same problem.

gt37vgt

hahahaha yeh yeh people getting greedy BOOST !! BOOST !! NOW !! NOW !! MORE MORE !! no waste gate no wasting my precious boost.

Bullwings

I'd be willing to pay $18k for a good VGT setup in our cars or an anti-lag setup that'll last 50k miles. If it meant full boost at around 1800 rpm with around 85% of the torque available from 1900-5500, I think $18K would be a bargain.

Porschefile

There is one thing that I see most people overlook when the whole variable geometry turbo discussion comes up in pretty much any forum. With the handful of production based VNT/VGT turbos out there, honestly there really isn't anything that would work too well in more of a "sports" type of application. I don't have any specs on the 997 VGT turbos, however due to the configuration with which they are used in OEM form, I'm sure they'd be a compromise on a different setup like a 951. Remember, to "properly" size a turbo for a motor you not only have to match the turbine, compressor and housings to the engine, but, you also have to match them to each other if you want a truly optimal setup.

Other than the 997 VGT turbos, and the few stock-sized VNT turbos out there, almost everything else is diesel-based. What does that mean? You have massive hotsides (usually 1.00+a/r), and large turbines which overall end up being a horrible compromise on any smaller displacement motor. Other than the OEM apps, there is no real source for any more realistic sized VNT/VGT turbine housings for a smaller displacement motor, so honestly none of these turbos are realistic for what pretty much anyone theorizing about them is looking for. You'd be better off experimenting with twin scroll setups or other methods of improving spool. All you'd have to choose from is some relatively small OEM VNT turbos rated at low power levels (like sub 250whp levels), and then a big leap up to big diesel stuff that still isn't rated to very high power levels relative to the component sizes. Take a look sometime at some of the OEM diesel turbos like GT37's, Holsets, etc. Many of them have a big turbine, big hotside, and paltry compressor in comparison which results in a moderate 400-600whp capability with excessive lag on a smaller motor compared to a properly sized turbo. It's nice to think about "neat" or obscure stuff like this but, in reality VNT/VGT turbos will never become "realistic" for aftermarket/modded apps unless a big manufacturer like Garrett starts releasing a big lineup/variety of VNT/VGT stuff.

Jesus, I get flamed trying to promote the awesomeness of Garrett GT series turbos, and here people are wanting to throw on some friggin Holset Duramax/Powerstroke crap! j/k lol One of these days after enough beating around the bush, this community will have exhausted all the wrong options and gotten it right! (again, j/k, but seriously) I on the other hand will not seeing as I can never complete a single project any more.

*rant on* %@#%_)*@@%+ BWWWAAAAAHHAHAHAAHA!!!! Willing to pay $18k for a VGT setup for a 951?! It amazes me some people here won't pay $5k for a GT series setup or $3-5k for an actual state of the art EMS (Motec, Autec, AEM, etc), but they'll go on all day about some obscure stuff that, in the end, won't really get you anywhere compared to buying the mainstream state of the art stuff that works. Jesus, browse some non-Porsche forums and figure it out already. I'm tired of being the heretic here, especially when I'm right! *rant off* *flamesuit engaged*

Oh yeah, and whoever hasn't figured it out, anti-lag destroys turbos. Stop fantasizing about some long-term daily driver anti-lag, VNT/VGT, super kryptonite-powered, uber stuff. This stuff is better left for Chevy Lumina forums or some other damn desolate interweb wasteland of powerless machinations.

gt37vgt

well i its clear that i will spent more time working on my car that driving it wow you crack me up almost as arrogant as me . Err both my crappy old vgt truck huffas are .8 exhaust AR . also every one I have ever spoken to who has them selfs first hand put a horrible deasil turbo on a car has been happy with it . .
Also Until i see a real world first hand failure of this concept it is completely feasible.

I realy get a kick out of people like you are convinced it wont work . i remeber getting the same story about the charge cooling set up on my propane turbo beemer ..

I am doing it for the sake of doing it to see what happens no doubt a well sized gt garret is the safe and sure option .

Bullwings

It's really funny that you mentioned that because that's EXACTLY what i paid for my turbo setup and tuning ($5k). It's a Garrett Racing GT30 turbo that Vision Motorsports had custom built for 951s... The car ended up spending lots of time in the shop since it took around a month for them to manufacture the turbo from scratch.

Still, if i could get an anti-lag setup that would last 50K miles, I would take that over VGT. Obviously, I know that's not happening, since rally cars change their turbos after a day or two worth of check points - not even 1000 miles... lol.

daigo

Hey Porschefile,
What ever happened to your project where you were going to use a GT series turbo on a 2.5? I was curious to see how that would have turned out.

mfloren

oph shnikes

RajDatta

It has already been done yrs back by Technodyne Racing.
Raj

Porschefile

I parted out my project (still have some stuff left) and sold the car to a friend. Honestly, as much as I love these cars, for all the stuff I was trying to do they are way too ridiculously expensive. I don't mind spending that kind of dough on my 911 because, it's a 911. Spending that on an archaic old 4 cylinder gets pretty lame. I just got tired of feeling like I was fighting an uphill battle.....with one hand behind my back.....hopping on one leg. I love the cars but, I so wish I would have just done the KISS approach for a more moderate power level as they are pretty good at that.

Judging by the references I've seen in the past to the Technodyne Racing GT setups, sounds like there were some less than optimal ones from them as well. Anyone that knows anything would know that the Gt2540r is a horrible turbo combo, excessively laggy for it's size (bad wheel mismatch), and definitely not optimal for a 2.5l. I know they used some other GT stuff as well but, I remember seeing more than one reference in the past to the Gt2540r setup and how much the GT series must suck because that one does (which isn't true). An off the shelf gt3076r in either .63 or .82 (depends on what you want) is pretty much the perfect turbo for these motors for most people's needs.

Sorry Gt37vgt but, there is a substantial difference between a properly sized turbo and some haggard diesel turbo being used on a much smaller displacement motor. I've known a few people to do the diesel turbo thing with their cars, and honestly most of those guys probably couldn't tell the difference between the 2. Will it work? I'm sure it'll work just fine BUT, it's like people using T4 setups on these cars to only achieve ~400whp. There are simply better and much more efficient ways to do things. Regardless of anything else, most diesel turbos are naturally used on much larger displacement engines, and therefore have much larger turbines as a result. Typically they'll probably be at least a stage 5 turbine if not a p-trim T4 or larger, and on a 3.0l or smaller motor under ~550-600whp that is simply overkill. What turbo are you using Gt37vgt? Sorry, I'm not trying to come off as arrogant.

When is someone going to come along and start producing T3 turbine housing conversions for these cars? That's what we really need, and hell I'd buy a 951 again if someone did (hey I'm lazy, I don't want to do it myself! ). I mean, there is such a huge selection of T3 frame stuff out there it would really open up a lot of possibilities. With the uber-small K26 housings and excessively large T4 setups for these cars, between 300whp and 600whp there is like NO gray area and plenty of compromise.

sawood12

It seems to me that there is no way Porsche have developed and utilised these turbos for some glossy marketing exercise - i'm pretty sure they are well up on the very latest that fixed geometry turbo technology has to offer but yet they still decided to go the variable vane route despite the increased cost and technical risk. I'm sure they do offer advantages over fixed geometry turbo's. One thing I can see that they offer as well as quick spool up time is the increased control the ECU can command. It is this very increase in control that has allowed the Tiptronic 997 turbo to out-accelarate the manual version because the ECU has control over both the gearbox and the turbo and makes the whole thing work optimally. And I imagine that we will see further exploitation of this when Porsche introduce direct injection in the facelift versions of the 997. This is something aftermarket fixed geometry turbo's cannot offer. You have control over the wastegate but that is about it. The variable vane system allows the ECU to control the speed of the turbo to optimise the shaft speed and maintain optimal efficiency over the rev range. I think it is pretty exciting technology. Whether or not we'll see it applied to the 951 in an affordable kit remains to be seen so thank god there are very technologically advanced and effective fixed geometry turbo's out there for us to choose from.

TurboTim

Jim Wolf has one on an Infiniti. I have seen it work firsthand. Full boost at idle or any rpm you want! It is called the hydraulic turbo.You can pretty much mount the turbo anywhere you want.

gt37vgt

well porschafile i will accept no apoligisies in regard to or disagreements as i realy enjoy debating a piont with some one with reasonable and intelligent points to make like your self

.You should apoligise if your leaving this forum as we would miss you .

I have 2 of these turbos a gt3571 and gt 3782 both have .82 ex A/R but what that means on a variable A/R set up i'm not sure .

I'm currently setting up the 35 on my 2.5 the map only goes to 39lbs of air per minute which is ok for a hopefully responsive 2.5 .

Do you know are all the mid frame garret gt turbos interchangeable in compressor wheels ??
because a 3076 wheel would be a better wheel and could go on to my 3.0 as well having trouble finding out I always consult turbobygarret.com for basic sizing an i agree the gt3076 is kind of benchmark from wich i would prefer not to stray to far from . both my turbos fall with in their hp and displacement sizing recommendations . i imagine i will stick with the gt 35 and hopefully upgrade the compressor when the 3.0 comes to be as it is a bit crazy mounting the gt 37 it will take up so space . I think if I can be convinced of your piont of the big turbines being a bother i will stick to the gt35 it's not so big ..13% bigger than a gt30 turbine

i think gennrally turbines on things are to small its cheaper and easier to change a compressor so the rest of the turbo is left behind.