Rothsport 3.4 , ITB, Garrett GT35R build

[rsscotty]

This is our latest 930 project, and what fun it was

3.4 liter twin plug turbo heads, wasted spark
911 SC camshafts
MoTec M84 running Bosch LSU 4.9 oxygen sensor closed loop
Garrett GT35R running .9 bar boost
Bosch EV 6 injectors
Bosch rising rate fuel pressure regulator
Full sized engine intercooler
Individual throttle bodies with custom plenum
Rothsport custom linkage and fuel pressure regulator breather console
Quick release couplers on all intake intercooler plumbing, intercooler and all pipes can be taken off in less than 5 minutes.
Factory exhaust with Turbosmart wastegate .... custom location in OEM heat exchanger...no boost creep.
Choice of straight pipe no muffler tailpipe, or 12" muffler version, both with quick disconnect v-band clamp at turbo outlet
Short gear ratios
Drives like a dream

[gtu935]

Really nice. We're looking for ITB manufacturer. We were using Mode but Bob stopped making them.

Bill Rudtner

[slow&rusty]

This would be my perfect build.

Where are the ITBs sourced from?

More details please.
Yasin

[TurboKraft]

rsscotty:
Nice job! Thumbs up for Jeff's tuning. What a great torque curve -- or is that a torque plateau? Really good numbers for just 0.9bar boost. It came out really clean. The black anodizing makes it all more subtle and serious.

slow&rusty and gtu935:
ITBs and super cool throttle linkage from Rothsport.
The ITB airhorns and plenums are TurboKraft. And the intercooler.

Glad we could contribute, the outcome is just awesome. :-)

[jpnovak]

Beautiful work and great results.

I too want to understand how you got that torque curve so flat! boost control?

[911nut]

Why the "factory" exhaust? Seems like your leaving a lot of power on the table.

[sundevil64]

Beautifully clean work!

I was wondering for those plenums were yours Chris.

[sjf911]

Now I know what I want on my next build, beautiful!
Why the rising rate fuel pressure regulator?

[torresmd]

Looks beautiful! Enjoy the hell out of it.

[Tippy]

524whp with just .9 bar of boost and stock exhaust?!?!

E85? Methanol injection?

[rsscotty]

Originally Posted by Tippy

524whp with just .9 bar of boost and stock exhaust?!?!

E85? Methanol injection?

Since we installed our Superflow dyno over ten years ago, our goal was to deliver the best finished product possible. Our dyno number represent the same numbers Porsche specs out for their stock engines, and that is what we see when we dyno stock engines. This is a consistent benchmark we strive to maintain, and that is why we keep detailed Superflow computer logs of all of our engines individually, along with detailed written logs of all changes. I guess you could say we know what works for our specialty builds. So the questioning of real world dyno numbers goes on. Our numbers represent our system which we believe is spot on. Again, consistency is the key.

Another advantage we have is sticking with Motec engine management. Once you accumulate a data base of maps, data logs, and analyze the results with Motec Interprter software, it clearly, in our opinion puts you at the top of your game.

So we work in conjunction with Chris at Turbokraft, not only testing and using his proven or new parts, but exchanging information. Hard to top that.

So answering your question.... premium Chevron 10% ethanol Oregon blend pump gas. No E85 or methanol injection..This is the only pump fuel we have ever used.

Visitors are welcome to stop by Rothsport any time and Jeff Gamroth or myself will give you a full tour.

Scotty

[Tippy]

Those are fantastic numbers for the boost level.

So, now I gotta ask, how about turning it up to 1.5-bar?

Numbers would have to be astronomical.

[rsscotty]

Originally Posted by sjf911

Now I know what I want on my next build, beautiful!
Why the rising rate fuel pressure regulator?

Differential pressure is the critical yardstick when discussing injectors in forced induction applications. As boost pressure increases inside the inlet manifold where the injectors are situated, the fuel rail pressure must also increase proportionally in order to maintain a constant pressure difference across the injector orifice. This is called a constant differential pressure fuel system. Less sophisticated fuel systems may not employ a constant differential pressure fuel supply - instead they maintain a constant fuel rail pressure that does not increase with increasing boost pressure. These are called constant fuel pressure systems and were only ever designed for naturally aspirated applications.

With a constant fuel pressure system, the pressure difference across the injector orifice drops as the boost pressure increases - and consequently the volume of fuel supplied by the injector drops as well. This can lead to engine damage through lean mixtures at moderate to high boost pressure levels.

The manifold referenced rising rate @ 1:1 addresses this issue and is a true constant differential pressure fuel system that maintains a constant pressure difference across the injector orifice. For every pound of boost the engine creates, you get an equal increase in fuel pressure. Hence the 1:1 ratio as it was referred to.

In conjunction with a single Bosch 044 fuel pump in the car, and a clean prefilter in the tank, I have found the data from Motec with the engine in the car replicates exactly what we see on the dyno, lambda numbers wise, which incorporates a high volume system using the 044 pump. Anything less than the above pump in the car is trouble for this particular engine. Data logs confirm... lean to very lean, and that was using the stock OEM twin pump system. Installed the 044, and results were the same lambda that was shown on the dyno. So installing this engine in the car and assuming the OEM fuel system would suffice would have meant trouble in some form down the road.

In order to ensure precise fuel pressure delivery at high horsepower levels, one 4.0 Bar fuel pressure regulator is used, and we have a center mounted Rothsport designed billet regulator housing to incorporate this regulator. In addition the fuel pressure regulator is vacuum/pressure referenced to the engine's intake manifold. In this way, fuel pressure across each injector orifice is maintained at a constant level regardless of the turbocharger boost pressure level - a configuration as found in the world's best turbocharged high performance production engines.

Shown below on another engine on the dyno is the regulator housing. The gold anodized part. It is also our pivot point for the Rothsport designed throttle linkage to work in conjunction with our individual throttle bodies. The regulator is towards the fan end of that piece.

[vinyl_tien]

Thinking to build one like this!!
Hi rsscotty, nice build, do you have picture without intercooler?

[rsscotty]

More photos as requested..

[vinyl_tien]

That is so cool, thanks!

[pkracer21j]

Amazing work Guys!
Your photos make me want to purchase a plane ticket for said shop tour!

Cheers

[willtel]

Man, that is just gorgeous.

In a turbo application what are the advantages of a individual throttle body setup like this over something else like a Carrera 3.2 manifold?

rsscotty, do you sell parts like the fuel pressure regulator housing to other customers or is all this stuff one off?

[sjf911]

Ah, I thought you meant one of these:

[totle]

What a cool build. Really like the ITB and plenums :-)