Twin VNT's to replace stock units ?

[andyf]

Sorry chaps, I haven't actually done this or anything, I'm just posting out of curiosity

After a bit of discussion with some friends, it seems VNT turbos are starting to become suitable for petrol engined cars. The Renault 5 GTT (url=http://www.rtoc.org/boards/Default.asp]link[/url]) boys seem to have found quite a bit of success using a VNT turbo to replace their standard from as far back as late 2004.

The revelation of Turbo Technics now testing bigger-scale turbos for cars such as the 200SX looks very promising. Seeing as the GTR turbos are technically a pair of small units, it strikes me that once a T25 or T28 equivalent VNT is available, it might well become a very good choice for a majorly responsive, low-rev boosting Skyline.

I'm wondering if any of you on the board here have been keeping an eye on developments, and whether you see any future in this tech for Skylines ?

[drewby]

yes

[drewby]

yes m8 i do see a future in the variable nozzle turbine, they are fantastic, & would be the best turbo ever to go on the gtr, giving you a small housing off boost & a large one on boost, whot could be better , i will have some on as soon as, the prob is a lot of gtr owners are abit like sheep. & only get whot the other man gets eg HKS, or whot a tuner says, cant wait for the vnt my self, you can pm me with any vnt imfo you have. thanks for the post. good to see another view, cheers. D

[andyf]

Good idea, I'll try and make a decent summary of all the info I've seen so far. The renault board has a crapload of posts from people that have done the conversion so that's where I will start.

Regarding people following the brands, like HKS - I can't see this being a problem, because once the technology becomes established, I'm sure HKS will go with it - they were after all very proud of promoting their Ball Bearing range of turbos, so expect a similarly decent ad campaign for anything VNT.

[SteveN]

has anyone solved the fact that theyve never seemed to be able to stand the heat of a petrol car yet, and fail/stick quite soon?

hence why they generally only used on diesels as the EGTs are far lower

[andyf]

It would appear so given the Turbo Technics Sprint-Sierra running two units for (I think) over 500bhp.

Linky to the post about it on this forum earlier

The car uses a 2.9 scorpio cosworth engine using our own pistons, standard rods and standard crank. The heads have been modified with larger exhaust valves, and it uses our own 12 injector setup. It also uses apair of our own petrol VNT T28's, designed in house. The management is taken care of by a Pectel ecu.

The shell is a 3-door sierra shell with our own roll cage and coil-over suspension. Transmission is stock sierra XR4x4 running gear including gearbox and diffs.

Beleive it or not, this car only runs 15psi boost, which equates to 530bhp and 500lb-ft of torque. The engine can run 700bhp, but we are waiting on a Hewland box before we can take the power any further.

[drewby]

hi andy is this jeff,s car, seen it at curborough sprint 2-3 year ago, he said it was poss 600. whot time did he get round there, i do this track too & have done a 35,4 but in road trim eg 1,5 ton car a fair time & has got me first in 5 times this year, be good to kno whot he can do, his he there next year, i will be, & with an extra 150 hp be good to go head to head with him, whot class did he run in. cheers. D

[SteveN]

andyf- they run them on that sprint car, but SPRINT is the operative word, a car running for 40secs a time is VERY different to a road or track car doing lots of miles.

if they are gonna be reliable now, thats great, but yet to see proof, especially as seen so much testing showing they do **** up on high EGT petrol car, so would prefer to wait myself.

[andyf]

Definitely a good point. The only thing I can counter with is that, I think, there was some talk of fitting a kit to a 200SX built for drifting. If they can sit on a drifter car session-after-session, it would be a good way to demonstrate they have the lasting ability

[mambastu]

I had a chat with Dan at TT the other day about these turbos. I'm sure he'll be on soon to talk about them as he keeps an eye on the forum.

At the moment TT don't actually do a bolt on turbo for the GTR unfortunately although they are now looking at it. It seems that the flanges are all the wrong shape/stud pattern so you'd need to adapt everything. The turbine housing is relatively large compared to normal GTR turbos so you may be able to space the turbo away from the manifold or if that doesn't work, make new manifolds. Dan said that they would probably supply a turbo flange plate with the turbos. I think Dan said that they're are two actuators on each turbo too. I presume one for the wastegate and one for the VNT bit. The oil/water lines would have to be adapted.
The turbos can take an EGT of around 950 degrees before they start experiencing problems and they cost around £700 + vat each.

They do sound very promising and they certainly work well on Geoffs Sierra. Dan was saying that they get a couple of psi pretty much off idle revs and it would be better on a GTR because the Sierra runs very low compression.

It would be nice to see some pictures of the VNT's next to a GTR turbo to get some idea of how much work it would be to fit them.

[Cord]

Any pics of these turbo's anywhere? Am interested to see how big they are, and how much of a job to get them onto a gtr.

[SteveN]

Sounds good. Deffo seems to be a load of grief in a twin setup tho.

Best bet would be a single turbo conversion, a 800bhp+ rated turbo that spools nice n low would be cracking.

One issue people havent mentioned which has been a huge issue in the past with VNT and non-VNT turbos when flowing big at low rpm is copmpressor surge.
Its gonna take some work to enable the engine to consume the air the turbo is trying to feed it.

Its hard to have your cake and eat it unfortunatley.

[Crash Gordon]

I remember a few years back here in the states a company developed a twin turbo setup for the NSX using this technology, and they had a really hard time tuning the AFR. It seems that these turbo,s were somewhat erratic. I am sure that in the past few years that these problems have been eradicated, but I do know for a fact that that was a huge concern on the NSx.

[andyf]

Corky Bell and the Aerocharger units?
I think they were mentioned in his Turbo book. Very early units though, I'm assuming things have come on leaps and bounds.

[GTR-Zilla]

The sequential twin turbo setup on a supra works very well to.. you get good boost build up at just 1500 rpm with the first smaller turbo that goes very well untill 4k rpm at which point the bigger turbo kicks in...

would a setup like this not work or be made for a skyline?