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Discussion Starter #1
Just wondering what would be a good choice for a Garrett turbo at around 650bhp.

For 600, we all think the Garrett GT35R with a .82 housing is the one to go for.

What about for over 600? Garrett GT40R? What size housing?

For a Rb26 go for a .85, .95, or a 1.06 housing on a GT40R?

Can GT35R get away with 650bhp? Or will 600bhp be max on a .82 housing?
 

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the gt35r also have a 1.something housing option that should be good for that sort of figure. probably bang on infact.

I have read that with the GT35R runs best with the largest housing on too.

cheers
mart
 

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GT35R with a 1.05 housing should be able to do a bit over 650bhp, claims are 700, but i dunno.

.82 housing should do 650 easy, well im sure it has.

Seen .63 housing ones do over 600, but suffer from surge on a lot of motors.

Either way tho, to max out those power levels your gonna need to run big boost, ie 2bar+, something most GTRs arnt specced for.

Or have a well over optimistic transmission loss number, lol :p
 

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Discussion Starter #5
SteveN said:
Or have a well over optimistic transmission loss number, lol :p
gtr mart said:
I think you will find that this is a well respected form of engine tuning....
:p :p :p

Well, If I want to get 650bhp with 1.6bar with mininium lag, what would be the best bet? Right now my old age T45s turbo makes 1.2 bar at 4700rpm and have a pretty respectful power band. [email protected] at hub on 1.3bar. I am just thinking I want to remap the car for 1.5-1.6bar anyways, might be worth while to get raid of that fossil of a Turbo and get something modern.... :rolleyes:

Also, at what point does the crankshaft become an issue when runing big power? I got forge piston and H-beam conrod, but not sure on crank until I do more search on it.
 

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Discussion Starter #6
I have nick the dyno graph of Abbey off a previous owner.



So the question is, how does this look in term of lag? Is it really bad enough for me to spend £1000 and give up the T45s and go for something like a GT35R.

The graph is is power and torque. 1.2bar is reach at 4700rpm. boost pressure slowly go up to 1.3bar (19psi) at 7500rpm. I am sure this can be fix with a better map and a better set up boost controller.

If I want to turn this up to 1.6bar and beyond with a remap, would the torque cruve get very narrow? Signal old demo R32 use this T45s and make [email protected] with 1.8bar.

I have search and it seems the T45s is the same as the TA45, came off a old Desiel Truck (as we all have guessed), and are made for extreme heavy usages. Eveything in that turbo are made for extreme usage, takes alot of boost and also are made to spin very fast. Would be very happy running at 9000+ RPM some people have said.

So using a GT35R I would loose about 1000rpm of boost threshold (4K vs 5K), Power should remain the same. Just wondering if it is worth the cost of swapping the turbo.

Also, the T45s is the same as a T04R, so I guess the GT35R should bolt right on the manifold and downpipe, correct?
 

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Heres a dyno plot from a Cossie YB running a .86 or whatever housing GT35 for comparison.



Its got more torque at 4000rpm as the above plot at peak.

And 220lbft more than the car has at the same rpm.

In my opinion though, thats probably as much to do with the general engine spec rather than the turbo alone.
 

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SIHethers said:
And the fact it is running 2.1 bar of boost :D
But that IS due to engine spec, ie its running low enough comp to be able to safely do that.
But that dont affect the rpm its boosting on, which will affect what rpm it has whatever torque at...

Heres another which is massivley better, for comedy effect...

GT35R or GT40R on that one, cant remember.
 

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Discussion Starter #10
They dyno on my car, as fossil is the turbo, how will it drive in real life?

With the 272 step1 CAM, is it possible for me to make the torque down lower by adjusting the timing? And just hope to make the same power or a bit more with higher boost.

What Comp will you need to run higher bost (1.8-2.0)? 8.3:1??? Will the 272 CAM be good with the GT35R? Or should I go for 260, 9.15 Tomei PonCAM like TweenieRob did?

I know the GT35R will be a big improvement over what I have. I just want to justify the cost of spending all that money.

How will my car drive in real life at 1.6bar (after a remap and adjust cam timing if possible)? Will it be very laggy with high boost treshold? Or will it be manageable on the road at least?
 

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Discussion Starter #12
Yes, but since I make only 1.2 bar at 4700rpm.

I am wondering if it is possible for the turbo to make 1.6bar around 5000rpm and keep it there until the redline.

At least I will have 2500rpm of full 1.6bar of boost to play with. I am just wondering how bad would that be as a street car.
 
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