Garrett GTX3576R: the best turbo for a CIS 930?

[1100sport]

I've been browsing the web in search of info about the "new" GTX turbo range from Garrett lately and I've come across some interesting findings that I wanted to share and have your views on.

Basically the GTX is an improved GT turbo on the compressor side - it retains the same hot side as a "basic" GT. Garrett have developed a new compressor wheel which appears to be similar to what BW has adopted on its EFR turbos with the "extended lip" technology. Let's say that it is state of the art for the compressor wheel.

The advantage ? Well the flow capacity for a given wheel size is improved. So much so that, according to Garrett, a GTX3576R (a GTX turbo equipped with a new generation compressor wheel with a 76mm exducer) flow about the same as a GT3582r (about 65 flow rate).

Thus on paper, it seems like the GTX3576 would give the best of both worlds: the power of a GT3582 with an even better spool response thanks to its shorter/lighter compressor wheel. Yes it is known that spool time is primarily determined by the hot side specs, but a lighter compressor should also help and cut spool response by a few hundred rpms...

Of course those in quest for maximum performance will go straight to the GTX3582r, a turbo which should deliver 25/50 ch more than a gt3582 all things being equal and which should absolutely shine on an EFI 930. But on a CIS 930, a GT3582 is already as big a turbo as you will ever want it to be in terms of top end performance (close to maxing out CIS fueling capacity on an otherwise mostly stock engine), and thus a GTX3582 would more likely be overkill.

Another element to take into consideration is the fact that, when destined for a CIS operated 930 engine, the gt35 (or Gtx35) will often be ordered with an optional compressor housing allowing to retain the 3" compressor inlet and 2"outlet - making it much easier to fit on the factory CIS plumbing. However, in that case the Gt3582 or gtx3582 comes equipped with a t04E compressor housing (.6 AR) instead of the standard t04s with its slightly higher AR (.7 AR). The difference is marginal but one can wonder if the bigger .83 wheel can give its full potential in that case. When equipped with a 76mm exducer wheel, the GT turbo comes equipped from the factory with t04e housing.

On paper, the GTX3576r appears to be a fantastic turbo for the CIS930,but sometimes real world experience translates otherwise. Thus I am dying to hear if some of you have some insights to share on this set up (Chris @ Turbokraft if you read this please do not hesitate to chime in!)

Mathieu

[TurboKraft]

Happy New Year.

Extended lip aka extended tip = old tech, Holset has done this for ~20 years. Everything old is new again... Every manufacturer takes what works from their competitor and incorporates it.

How much boost do you want to run, and what do you expect at part throttle / moderate boost levels?

Those are really the deciding factors in GT vs. GTX turbos.

"Yes it is known that spool time is primarily determined by the hot side specs" ...
Correct.

"...but a lighter compressor should also help and cut spool response by a few hundred rpms..."
No, not really.

[911tracker85]

in process of full rebuild on my 78 3.3 motor.

has a K27-7006 if I recall. planning to upgrade. keeping CIS. rebuild/upgrade fuel head and air flow and WUR.

suggestion?

[1100sport]

Thanks a ton Chris! Happy new year to everyone.
I currently have 0.8b spring, and want to install a MBC to hold the boost at 0.9b (no more than 1b in any event).

My car is primarily used on street with a few track days per year - but it is quite a hard core set up with coil over suspension, mono ball everywhere and 935 spring plates. I use it on week ends to have a rush of adrenaline, for fun and excitement really.

The engine is a euro 930 3.3l freshly rebuilt from the ground up (no expense spared) with the following upgrades:
Kokeln long neck intercooler,with 3" 965 inlet tubing
964 cams
Rarlyl8 headers (38mm ID primaries) and free flow exhaust
Msd6AL2 ignition with programmable mapping (locked dizzy)
Lightweight flywheel
Sachs Sport clutch (934 style)
lightweight pulley (full AC delete)
BL WUR with RPM solenoid / 044 fuel pump up front

When it comes to my expectations, I would like a turbo which will push really hard to red line set at 6800tr/min (I want to have a kick in the pants when I rev it hard ;-)) and ideally a responsive turbo at part throttle... My HP goal is about 400WHP.

I have done some additional home work and I seem to understand that the GTX benefit only shows at high boost level (above 20psi) whereas the GT compressor wheel gives better results at lower boost levels...
Reading through your answer, I seem to understand that the GT3582R would fit my goal, or wouldn't it? Thanks ;-)

Originally Posted by TurboKraft

Happy New Year.

Extended lip aka extended tip = old tech, Holset has done this for ~20 years. Everything old is new again... Every manufacturer takes what works from their competitor and incorporates it.

How much boost do you want to run, and what do you expect at part throttle / moderate boost levels?

Those are really the deciding factors in GT vs. GTX turbos.

"Yes it is known that spool time is primarily determined by the hot side specs" ...
Correct.

"...but a lighter compressor should also help and cut spool response by a few hundred rpms..."
No, not really.

[quattrorunner]

Great looking car!
What is it? Is it really a 75?

[quattrorunner]

More pictures NOW!

[1100sport]

[1100sport]

[RarlyL8]

Unfortunately there is no "best" turbo for the CIS 930. Every engine build is a little different and every driver's expectations can be a LOT different.
Define your expectations and then build to meet them.
If you want a quick spooling street car with 300WHP then use a smallish turbo (K27-7200 or GT30), SC cams, and headers with smaller primary pipes. If you want big power and like the hard kick when the turbo hits then use a big turbo (K27-7006 or GT35), big cams, and larger tube headers. If you want BOTH you'll need to define where you want the torque curve, where you want peak horsepower, and how much power. Then choose the cams and turbo to match. Quick spool with big power will require a split plenum turbo and headers, attention to tune, and a good flat fuel curve.
Car looks fantastic!

[quattrorunner]

Beautiful! Love everything

[Hams930T]

Super bad ass car! I like the non-sunroof and the deletion of the rear bumperettes. Good stuff!!

Bigger turbo's have a trade-off no question. However; with the technology in the newer turbo's - you can make a lot more power and still have great response. The GTX35 would not disappoint.

[quattrorunner]

Is that a real 75 930?

[1100sport]

@quattrorunner: No ;-) the build target was to recreate a car that never existed (as if recreating an actual car was not difficult enough!): the one that was sidelined at the last moment, the 930 RS... The first 930 rolled off the production line for MY75 and I like the special features of those early IB cars - so this car has been extensively modified to resemble a MY75: Manual driver only flag mirror, AC/Sunroof delete, bright trim, pop out quarter window, early dashboard with speaker cover, manual heat with 2 levers, no central console, early sport seats with external hinges... The list goes on and on. We started with a Euro 1983 930 3.3l and it's a 3 year journey! I will detail the build in a specific thread at some point.

[1100sport]

Thanks Brian. My feeling (need dyno validation) is that my current turbo configuration (built around a true racing TR30R, similar to a GT30R) is on the small side for my application. With 964 cams and your rather large headers (fantastic by the way), it seems to beg for more thrust at higher revs.

Originally Posted by RarlyL8

Unfortunately there is no "best" turbo for the CIS 930. Every engine build is a little different and every driver's expectations can be a LOT different.
Define your expectations and then build to meet them.
If you want a quick spooling street car with 300WHP then use a smallish turbo (K27-7200 or GT30), SC cams, and headers with smaller primary pipes. If you want big power and like the hard kick when the turbo hits then use a big turbo (K27-7006 or GT35), big cams, and larger tube headers. If you want BOTH you'll need to define where you want the torque curve, where you want peak horsepower, and how much power. Then choose the cams and turbo to match. Quick spool with big power will require a split plenum turbo and headers, attention to tune, and a good flat fuel curve.
Car looks fantastic!

[93097004xx]

Originally Posted by 1100sport

@quattrorunner: No ;-) the build target was to recreate a car that never existed (as if recreating an actual car was not difficult enough!): the one that was sidelined at the last moment, the 930 RS... The first 930 rolled off the production line for MY75 and I like the special features of those early IB cars - so this car has been extensively modified to resemble a MY75: Manual driver only flag mirror, AC/Sunroof delete, bright trim, pop out quarter window, early dashboard with speaker cover, manual heat with 2 levers, no central console, early sport seats with external hinges... The list goes on and on. We started with a Euro 1983 930 3.3l and it's a 3 year journey! I will detail the build in a specific thread at some point.

This is a nice mod, well done. Although a 1983 930 is a pretty rare year.


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[SexOnTheBeach]

Best for your car will be a gtx3582r's, bullet proof combo for your specs, I myself have a 3.8 993tt using two gtx3576r's thou and they ate making 875hp without a hicup, for single turbo setups the 82's is the way to go, imho.

[krasuskyp]

whoa - I so love everything about what you did there

very well executed, lots of really neat details (drilled key! Sweet 917 balsa knob on a Wevo, etc.)

def one of my fave-ever builds here! More pics / details!

you said it started life as a MY75 and that you then went to re-create a... 75. confused 8-). With an '83 engine. Is the first "MY75" a typo?

[JFairman]

I wonder how much less the hood weighs with all those holes drilled in it.

[OldSpool87]

Very cool build. What's the story on the seat belts. It's funny how we each pick up on some detail. Very cool build and well thought out.

[jsveb]

Absolutely gorgeous car.

Is that a transmission cooler on the lh side?