Precision and Comp BB Turbos

[260DET]

Looking at replacing the present GT35R single turbo on either a VG30DET or a VG33E with similar power potential, the present back housing A/R is too big so rather than replace that housing it may be better to go with a complete later technology turbo and sell the present Garrett. A 6262 seems about right, it should spool a bit better and certainly should be capable of delivering say 450whp with a useable power band from 4000 to 7000rpm. Its for my road course S130 so acceleration from 3500-4000rpm in third and higher gears is crucial.

 

Anyone with experience with these turbos who can suggest which specs would be best and comment on their reliability?

[Brad-ManQ45]

The GT35R is already more than enough for either engine, provided you have the right turbine housing, which you allude to not having but don't specify which one you have.

 

In point of fact, for road racing, I would consider the 3076 w/a .82 exhaust housing (~same flow as the .63 GT35R housing).

 

Area under the curve is far more critical for road racing and I think the lower end response would really help more than later top end power...

 

You haven't mentioned how much boost you want to run either, so until we know more specifics you're just gonna get pot shots/guessing at what would be appropriate.

 

Not sure what you mean by later technology, the 6262 that you refer to seems to be a Precision turbo, and there is no "later technology" there.

[260DET]

Present back housing is a 1.06, was going to change to a .82. About 20 pounds boost will deliver 450whp with the DET engine, would expect the same with the 33 but a bit more boost is no problem if required. I'm a bit wary of having too much response at say 3500rpm in case it runs out of puff at high revs, the engine really needs to pull hard from 4000 up to 7000 with very good throttle response.

 

Precision and Comp are supposedly using smaller more efficient billet wheels than the GT35R has to give a faster spool and comparable power eg http://www.compturbo.com/products/index.php?folder1=Turbo_Chargers&folder2=CT4&product=CT4-6262

 

In car video of the car, 8000rpm tacho on the right, speedo on the left reads in km/h

[510six]

I just sent my T67 back to Precision for the second time to replace the ball bearing cartridge. I purchased a plain bearing T67 from Limit Motorsports and wished I had left it on the car as the cartridge from the Precision went bad running 7.5psi in less than 5k street miles and took out a motor due to oil contamination from the turbo. Unless major changes have been made to the ball bearing cartridges from Precision I would strongly suggest using a reliable product from another manufacturer.

[260DET]

Then there are Borg Warner turbos http://www.bullseyepower.com/S200.asp

[260DET]

The GT35R is already more than enough for either engine, provided you have the right turbine housing, which you allude to not having but don't specify which one you have.

 

In point of fact, for road racing, I would consider the 3076 w/a .82 exhaust housing (~same flow as the .63 GT35R housing).

 

............................

 

Thanks for the comment, finally decided to do the maths involved and bugger me it lands at the three intersection points used just barely to the left of the center island all the way up on the Garrett GT3582R map. Thats with the VG33 rated at 80% VE and 10, 15 and 20 pounds boost at 7000rpm which I guess means that at say 4000rpm the turbo will be operating well out of its efficiency range.

 

With the GT3076R map the same three points are in the center island to the right and up a bit, the 20psi point being up near the top tip of the center island. So I'm guessing that with this turbo between 20 and 25 psi would be a sensible limit and acceleration from 4000 rpm would be a lot better with a 7000 rpm limit about perfect.

Edited October 11, 2010 by 260DET

[Brad-ManQ45]

I THOUGHT you might like the 3076 once you really looked at it - you'll get a bit better response from the slightly smaller impeller wheel just to start.

 

You may want to consider the 1.06 turbine housing for top end - it's ~= to the .82 GT35R turbine housing, but I think I'd start with the .82 and see if it's holding you back any up top - for sure it'll be better getting to the top end.

 

Except for pure drag racing, I'd trade a small bit off the top for better response across the range any day.

 

Sometimes having a choice of gears lets me be a bit smoother and work a bit less.

 

I'd do a search of this site and look for the GT35 threads and check out what those that have swapped turbine housings have to say.

[260DET]

I THOUGHT you might like the 3076 once you really looked at it - you'll get a bit better response from the slightly smaller impeller wheel just to start.

 

You may want to consider the 1.06 turbine housing for top end - it's ~= to the .82 GT35R turbine housing, but I think I'd start with the .82 and see if it's holding you back any up top - for sure it'll be better getting to the top end.

 

Except for pure drag racing, I'd trade a small bit off the top for better response across the range any day.

 

Sometimes having a choice of gears lets me be a bit smoother and work a bit less.

 

I'd do a search of this site and look for the GT35 threads and check out what those that have swapped turbine housings have to say.

 

A 1.06 back housing makes sense for a 3076, I know that a .82 on the present GT35 would perform better. Have done a lot of research but so many use GT35's on ~three liter engines its hard to go past that, but a lot of them are drag cars or dyno queens. Will get hold of a proven calculator to check my maths though.

Edited October 11, 2010 by 260DET

[Brad-ManQ45]

Your math IS good - been there and done that already.