Turbo size


nautoncall

nautoncall

GT Owner
Mark II Lifetime
Apr 6, 2014
1,093
What size turbos are everyone running? I think Heffner and Hennessey are using Garrett GT35's. Anyone running Precision? My car has Precision 6162s. Here is the dyno at 16 psi. Thinking about upgrading to Precision 6266 but I am afraid my lag time will be worse. Tuner recommended to go with Precision 5858 to be more fun on the street with much more response on the low end. I think I would be happy with 800-850. Just a fun street car that makes good power and not much lag. Thanks in advance.
 

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By the way, my turbos are journal bearing. With the upgrade, I would obviously go to ball bearing.
 
Kevin at M2K Motorsports has only used Precision Turbos on his builds.

Thanks,
Mark
 
U want zero leg? Go twins over stock blower u will have the biggest smile on your face , I have read somewhere that one of Ray's car was done with the twins over stock blower and he couldn't belive how fast the car was
 
Yea, that's what Hennessey does and I know from reading the forum that Mullet's car is SC/TT. Just trying to do minor upgrades to my current set up. I know some lag is the trade off for twin turbos but just weighing my options.

I already have Precision so the easiest is to upgrade these....or just be happy with where I am.

HP is like a drug!!!! Can you ever get enough?
 
U want zero leg? Go twins over stock blower u will have the biggest smile on your face...
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There are trade-offs in any set-up. In this configuration, there's benefit at the low end but the SC becomes a liability on the high-end - adding increased heat to the charge and dragging HP from the engine. In Heffner's early experience with one of Ray's first TT cars, he experimented with this set-up and eventually discarded it in favor of TT-only. Subsequent to that, Hennessey offered that configuration and allegedly has some very happy clients with it.

My preference is for a properly set-up TT system. To the op, I think that graph indicates that there is a LOT of room for improvement. On the high-end, I thing you should be seeing 80-100HP more than is shown. More importantly, there is a lot of turbo-lag shown in that graph. I think there are areas in the low range where you can/should be making SUBSTANTIALLY more power - all of which would contribute to an entirely different driving characteristic. It is important, as you say, to get the right turbos but also as important is sizing the tubing in front of the turbos. Finally, making sure you have good wastegates (with no leakage) and pay attention to the exhaust tubing post-turbos. A/F's look acceptable if not good with just one area where the car is coming onto boost that is OK but should be watched.
 
I had a Hennessey built SC/TT GT and Precisions we're NOT used. When I had the car upgraded we then went with Precision. Different people use different turbos, but I would stick with Precision.
 
My question is what size? Are my NON ball bearing that much a problem . Plus they were rebuilt at that .


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op,

Here is a graph of a well-developed TT system on a FGT running 16 psi of boost on 91 octane. Using an in-car electronic boost controller, the driver can dial this up to 26psi (1017 RWHP) - although at this level we would recommend C16 fuel. You can reasonable call this a pinnacle FGT TT set-up as you'd be hard pressed to find any TT that brings on boost this low in the RPM range. Ball bearing, oil-lubed GT35 turbos. Turbos as close as possible to exhaust manifolds. Optimized exhaust tubing size between manifolds and turbos. (Note: At 4000rpm, there is a 240HP difference in RWHP!)

This isn't intended to discourage you - just the opposite. I hope it shows what is possible and that it is worthwhile to get there!

16psiTT_CoolTech.jpg
 
For a TT/SC I would suggest 67mm. Or, as I would say, go big or go home, I run 82/85mm Precisions on my GT... Okay, maybe don't go as big as I have....
 
Wow boys!!! Thanks


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MarkH said:
For a TT/SC I would suggest 67mm. Or, as I would say, go big or go home, I run 82/85mm Precisions on my GT... Okay, maybe don't go as big as I have....
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I agree, my SC/TT setup on my GT always used 67mm Precision turbos. Great all around setup for 95% of people who want 1000hp.
 
I have 61 mm GT35X turbos on mine. I think that's enough for me. It made just at 1000 rwhp with the race gas tune, but this motor has always been a little low. I had another blue car with a freak motor in it with the exact same set up that made quite a bit more.
 
DBK said:
I have 61 mm GT35X turbos on mine. I think that's enough for me. It made just at 1000 rwhp with the race gas tune, but this motor has always been a little low. I had another blue car with a freak motor in it with the exact same set up that made quite a bit more.
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Whatever happened to that blue TT car? It was really cool.
 
User mmlcobra on the forum bought it.

Selling that car was an own goal. Freak motor, killer looking TT setup, wheels looked good, whole car looked awesome.
 
DBK said:
User mmlcobra on the forum bought it.

Selling that car was an own goal. Freak motor, killer looking TT setup, wheels looked good, whole car looked awesome.
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That is one of the few GTs I regret not jumping on.
 
I'll give a nod towards Precision as well. I switched from a 35R to the new 6267 ball bearing with the billet wheel and haven't looked back since. Plus, the rep at FL2K told me every part of the manufacturing process is done in the US (I and a bunch of buddies thought they were Chinese turbos).
 
User ... What's your numbers? Any graph?? When does your boost come on??


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DBK said:
User mmlcobra on the forum bought it.

Selling that car was an own goal. Freak motor, killer looking TT setup, wheels looked good, whole car looked awesome.
Click to expand...
It's a great car.
And fast!
Steals the show where ever it goes.
Best,
Mark
 
Anyone go whipple 4.0 / TT setup? Any gains from a lower air temps charge from a more efficient blower.
 
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