Duke

The logic seems backwards to me.. The lag is mostly dictated by the turbine size. A GT35R compressor won't increase lag by much over the GT30R.
A 1.06 hotside over a 0.82 on the other hand will.

Going to the next step however (GT4088R) will increase the shaft size so weight (and lag) will be increased more compared to a 30 --> 35 step.

spoolin51

Porschefile: Will do. Talked to the shop today regarding the V-band. Thanks for the help

spoolin51

Duke: I agree......

Porschefile

That's true Duke, though also there are a whole host of other things that can cause weird performance characteristics. For example, mismatch of wheels even with "properly sized" hot/cold sides can still create a poor performing turbo. It's definitely a fine line to say the least.

Rogue_Ant

Porschefile,
What do you think of a GT35r/30r combo? The 35r compressor with a 30r turbine wheel/housing.


-Rogue

333pg333

What, or how much has changed in bb tech since the first Garrett ones came out on the market?

Also related to Rogue's question, what are the effects of the same wheel in different sized housings?
OT Rogue I put down a deposit on one of those trannys we talked about before...yikes!

Rogue_Ant

Thats awesome! I really look forward to seeing some drivetrain advancement on our cars. Its about time I start sorting out what direction I'm going...


-Rogue

333pg333

Well it remains to be seen just what else will suffer by virtue of strengthening this, but may as well aim high...

Porschefile

Not worth it IMO. Surprisingly, I have actually seen an example of where that combo on a 2.0l i4 actually spooled SLOWER than a straight Gt35r. The reason had to do with the smaller turbine not being large enough to make enough initial axial torque to get the compressor spinning. The result was the full size 35r spooled 100-200rpm sooner than the 35r/30r combo (also sometimes known as a 30/40r). I wish I still had the dyno charts to show you. The general consensus is that the 3076r and 3582r are basically well matched for their own respective wheels. It's a far better route to simply choose an intended power level and desired power band, then tailor your housing sizes around it, then just go with an off the shelf straight 30r or 35r. At least that's my opinion anyways, and you know what they say about those. And it doesn't necessarily have to do with just GT series turbos. Most reputable manufacturers put a heck of a lot of time, effort, engineering, and R&D into their turbo specs so it's a little hard to try and "out think" them when these companies have likely expended millions developing these damn things.

Patrick, turbo tech as far as I'm concerned hasn't really progressed quite as much in recent years despite the huge advancements in technology out there. There have been some great advancements, such as the Borg Warner VTG turbos of course, however there hasn't really been much of an advancement in a large scale production sense. Garrett's GT series were, at the time, a HUGE leap in technology over the stuff that was around at the time. Up until the late 80's to early 90's, turbo manufacturers had basically been operating off of 20+yr old turbo designs. There were of course always exceptions as manufacturers would sometimes produce limited runs of out of the ordinary high tech, exotic stuff. These days, there are companies producing low production high tech stuff with fully CNC'd, CAD/CFD designed wheels, exotic materials, etc etc. It's kind of like PC's though IMO. I think things probably can't progress too much farther using the same standard turbo technology before people will have to completely redesign the way they operate and are built. You can only adjust wheel trims, housing sizes, and wheel aerodynamics so much before you are only talking about hundredths or thousandths of a percentage of improvement.

I'll say this much to put it simply. The gt3076r and Gt3582r are great turbos as is. There is absolutely no reason to modify one, save for using different housings. With the 951 powertrain, judging by what I've seen there is still a ton of potential out there that has remained relatively untapped, or at the least is often overlooked. I'd leave the turbos alone and work on the inefficiencies of the 951 drivetrain as the turbos are about the best match for their respective purposes as one could ever hope to achieve, especially for an off the shelf turbo. There are so many things most people never do to their 951's like larger/redesigned intake manifolds and large IC's, that it's kind of pointless to mod the turbo when the net effect is not going to be that great while those inefficiencies remain the same. For being 20yr old "archaic" drive trains though, I still can't wait to see just how well they perform with all of these kinks and "inefficiencies" worked out plus a nice modern BB turbo, as they perform pretty damn well as is! I just can't wait until I can afford one again so I can put my money where my mouth is.

95ONE

?
The GT35 is a larger turbine as well as compressor - more lag. Are you confusing the A/R with the Turbine size? I threw in Garretts definiton of their GTR series turbos so that some would understand. The 35 part of the GT35 is what defines the larger TURBINE wheel. A/r can also give more lag, yes.

You guys have to understand that actual horsepower rarely plays a role in the ricers decision to buy a turbo. (I am NOT talking about Spoolin - he's clearly making the right decisions) I was so annoyed at the question I always got from strangers when working on customers turbo cars. It was NEVER "What kind of power is it going to make" It was, "What size turbo is that?" They didn't care if their car could handle the power it could make, as long as it was a "big" turbo they could brag about. Yeah. Major compensation issues.

in the end, we all agree. Spoolin is definately making all the right decisions at this point. Smaller turbo, smaller A/R. GT30R is a fantastic turbo. Still. If I was planning on staying at 400whp, I would have gone with the GT28 Disco Potato.

Duke

Sorry, I missunderstood you. IMHO people usually refer to the turbine housing when saying just "turbine" and not the turbine wheel.

333pg333

Ok so if a smaller wheel in a bigger housing doesn't equate to much more than a bit of lag (in some cases),
what about these 'Zero clearance' Turbos being touted on other websites? Obviously not Zero but I assume that the wheel is filling the housing almost completely. I haven't read too much about them. Probably pixie dust for the 996 crowd.

TRP951

from what I hear the zero clearance turbos are a coating to get the clearance down

Porschefile

Haha, and that's why there are several people running around here with T4 setups barely making 400whp. Go figure.

95ONE

Just pulled some hybrid T4Ebay turbo off a 1.8 liter '02 Toyots MRS. Just ridiculous. Wouldn't spool. Tried to though. Fixing that problem now.