How do you get the torque curve sooo flat? Really consistent boost thoughout the rpm range? Most of the Dynos of turbos I've seen, including mine, the torque curve looks more like an hp curve.

Jenveys Itb's, Rothsport linkage(Porsche motorsport copy), nice stuff from Jeff.,cheers, Stef.

This was an all new experience for us as far as the plenum and ITB's and we couldn't be more pleased with the results. The throttle response is instant, just like on our normally aspirated engines. We have yet to use a 3.2 intake with a turbo, so we have no dyno runs to compare to this setup. I have seen turbo engines using the black plastic 964 intake, and probably would use that intake before we would try a 3.2 intake. The combination of all the parts we chose worked out to what you see on the dyno sheet, I don't believe it was just one or two items.

We use our fuel pressure regulator housing on all of our most recent ITB builds, and all of our parts are for sale. I can't think of any one off's at the moment, but they have their place.

Is there any way to get a video free-revving? Not asking for high-RPM, just some quick "blips" to hear the throttle response of the ITB's.

This is the benchmark regarding induction (ITB's) and EFI (Motec) and wanted to hear just how quick these low-compression engines can rev. :)

There are a few good reasons why people use the 3.2 manifold over the 964 manifold. A couple of them are the 964 T/B shape and they are known to blow off the lower rubber boots or apart at the upper rubber boot with a good amount of boost put though them. The 3.2 is bolted down to the heads and has very little flex once you put pressure into it.

Very nice build by the way. Damn good job.

Besides the improved throttle response, some other advantages of the ITBs over a 3.2L Carrera manifold, or even a nylon 964/993 manifold:
* more efficient cylinder filling
* wider power band -- more low rpm torque, increased useable upper rpms
* more linear throttle control
* ability to make use of larger, higher overlap camshafts without the typical idle issues or flat spots in the power band.

On this last point:
This is because ITBs also stop the reversion caused by camshafts with greater overlap The intake pulse from one cylinder is stopped by the throttle plate a few inches above it, instead of crossing through the manifold and affecting other cylinders as is the case on single throttle systems. This allows big lumpy cams to act as smoothly as SC or 964 cams.

And then there's just the bad-*ss factor.


We built our beyond-GT2-Evo 3.8L Twin Turbo street engine using these same ITBs + same billet air horns & plenums and the throttle response was like a GT3 -- very crisp and snappy, completely controllable. Yet despite rather large camshafts and a very lightweight clutch & flywheel assembly, it had no flat spots in the power band and always settled into a smooth 950rpm idle. Similar builds with a single throttle 964/993 manifold usually peak at 6,200-6,400rpm, whereas this engine's power was still climbing at 7,500rpm.

Back to back vs a Carrera manifold?
On a Bob Holcombe MODE-tuned 3.5L TT 930 street engine already making 700hp/almost 600tq on his engine dyno, the ITBs added 50hp, another 1,200rpm useable rev range, and something like 90ft.lb. at 3,500rpm, IIRC.

Thank-you for the insights Chris.

Pretty amazing power band. :)

How much more are the ITB's in comparison to the 3.2 intake?

rsscotty -- what is Rothsport selling its ITB setup for, and what all is included? Does it still work with the original 3-bolt throttle console?

The ITB plenums and airhorns are all billet 6061 aluminum, with viton o-rings between all surfaces, stainless fasteners. I'll verify current price on them.

And for anyone concerned about 6AN fuel lines and rails being too small -- they support 800rwhp on e98.
Just sayin'. :-)

Yep EFI=Pressure not volume

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Chris,

Shown below is an engine (non-turbo) with the ITBs installed. For turbo applications you remove the black billet pieces on top of the throttle bodies and bolt on the Turbokraft stacks. The black billet pieces are to adapt to a 3.6 n/a plastic intake. The throttle linkage is as shown with the center pivot, breather cover with fuel regulator housing an option, as shown in a previous post picture, which is a lot cleaner and simple compared to it being on the end of a fuel injector rail.

The three bolt console in the picture is not required if you use the billet breather cover that incorporates the throttle pivot. So yes Chris @ Turbokraft, you can use the OEM 3 hole bellcrank mount.

Any price quotes can be addressed to Jeff at the shop, either by phone or email.



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Very clever linkage design. Beautiful!

Prrrreeettttycool!

How do you guys get that torque curve so flat from 3.4K rpms and about 260 HP all the way to 500+hp?

Was the dyno properly calibrated?

So cost wise, are we talking about 2600.00 to 3K just for the throttle bodies etc?

What about the Plenums?

Are the throttle bodies sized to stock 930 intake ports? Or are adapters or head porting required to get them to work?

Dyno calibration
 

We have a Superflow engineer come to the shop and check out our whole system including any software updates they deem important.

That is good enough for us. The numbers are real, no special button to push that says make torque line flat....results based on many years of experience I would hope.

Shown below is our dyno room facility, that includes state of the art air in /air out fresh air ventilation system, frequency drive electrical setup for absolute control of the system, and the best room that Jeff could build with the available space we had.
This accounts for the consistent test results that we strive for, and optimal conditions regarding room air temperature. We also incorporate double System 1 oil filtration system, filters checked and cleaned during and after every dyno session, and we use Brad Penn 30 wt. special engine break in oil on every engine. Did I say we are fussy?

We also use ECM laboratory grade lambda sensor system that is linked to the Superflow data. Trusting your a/f ratio data is critical.




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Our billet adapters fit in between the stock intake port and the throttle bodies. The transition is smooth and the adapters can be made to fit any intake port size.
The Jenvey throttle bodies sizing is based on how much horsepower per cylinder you are expecting. They have a specific guideline formula on their website.

Why SC cams?

ITB /Linkage/FP Regulator breather console
 

Chris @ Turbokraft needs to post his prices on the plenums, pipes and q/d couplers and intercooler.

Our ITB assembly with cylinder head adapters, linkage and billet breather console as seen in photo #13 is $4000.00 USD. The black adapters seen in post # 30 are part of another kit...not used for this turbo build.

Also................... go back to post #30 and re-read, as I have made some clarifications on using the OEM bellcrank mount.

Really cool project! Thanks for sharing and great workshop! Keep up the billet hardware! Curious what gearbox / clutch is this beast running?

Wouldn't the lower peak with a 964/993 manifold just be an indication that the plenum size and runner combination is on the small side?

Have you tried using twin plenums 962 style plenums, the itb plenums with one or two traditional throttle bodies or dual plenum?

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