ITBs - jenvey vs AT Power... thoughts experiences

[TAV]

HI guys

Just about to put a Motec system on my rebuilt 3.6 with:
- cup cams
- GT racing headers.

Decided to put on ITbs now rather down the track, so less dyne time overall.

Any thoughts/experiences on either the Jenveys tapered kit or the AT Power shiftless ITB kit?

Thanks

[Tbone1209]

My friend just went through a thorough eval on both and talked to a lot of people. These are for a fully built 4.1L (you heard me right) with factory RSR heads and custom everything. After all the discussions, he decided to go with AT Power. They allegedly flow very well...

[Mahler9th]

I have no experience with either system.

I do know that Rothsport in Oregon has a lot of experience with Jenvey-based induction systems for various applications including those with large displacements. I am sure that they also have experience with other historically popular ITB systems including those from PMO and TWM/Borla. And of course with slide-based systems including their own. Excellent folks, with experience (at the highest levels for street, racing and mixed applications) and expertise.

The developer and distributor of the ATP systems for our Porsche applications is Reno Rennsport here in the US. My engine builder and friend co-owns Reno Rennsport with his son and a few others. He also has a lot of experience and expertise with all sorts of induction system designs and configurations, including factory slides and custom designs.

I am sure that both have done plenty of flow analysis work through the years, as part of pro, pro-am and am racing engine development.

I believe that the ATP system is a major breakthrough with the proprietary shaftless butterfly design.

I race here in Norcal and my class does not allow ITB's. But the ATP system is becoming very popular with classes that allow ITB's and their use is spreading very quickly. I know of another local engine builder with extensive Porsche racing experience (including World Championship winning teams) that has employed the ATP system in one of his customers cars.

I suspect that once everything is said and done, the community will conclude that the shaftless butterfly system is as close as you can get to slides at a fraction of the cost.

I would encourage you to contact Rothsport and Reno Rennsport with specific questions about induction systems that they may be able to design and sell based on Jenveys and ATP ITB's respectively.

[1ricardo]

Hello I'm in the processes of doing the same
ITB from Jenvey with Fueltech FT500
I not planing in gain horse power with this setup neither to race with the car, I'm doing this just for the looks of the ITBs on the engine bay, yeahh I know stupid right?! LOL
But any way, I barely start the install and a lot of issues already arose, plus many other that I don't even imagine so far...
For instance
1-) Where do I get the vacuum for the brake boost?
2-) Where do I get the vacuum for MAP?
3-) Which air filter to use?
4-) Where do I install the crankcase oil breather?
5-) Where do I install the air temperature thermometer?
6-) What do I use for ignition? ( I would like to use a single coil for each spark plug, but the 3.6 have 12 sparks plugs and I would like to build this within a budget)
7-) Do I use the original 3.6 knock sensor?
8-) I will not use a A/C, do I need a Idle regulator?
9-) Do I use the original 3.6 fuel regulator? IF not what type of fuel regulator to use?
10-) On the cylinder number 4 ,I guess, there is a pyrometer, at which temperature I should setup my FT500 to alarm me of a over heating cylinder?
That from the top of my head...

[Jeff Alton]

We ave built a few motors with Jenveys. Not familiar with AT Power at all....

[TAV]

Appreciate the replies. I'm leaning towards the AT Power ITBs

Thanks again!

[Omegaman]

Id say the AT power ITBs are the best bet...but......their dyno comparison chart using a stock euro SC motor seems a bit optimistic to say the least.

Given transmission loss of 15% RWHP for an Euro 3.o with ITBs, ECU and tubular exhaust system would be max 230HP giving around 260 flywheel.

They claim 260RWHP compared to standard ITBs giving 235RWHP. That's 300 flywheel HP......no way!!

[Mahler9th]

Those results are likely valid knowing the folks involved.

What is likely the largest group of Porsche folks running this induction system in the world will be at Sears Point two weekends from now.

Proprietors/racers from Reno Rennsport, their customers, and hopefully a visit from one of the most reknowned and experienced Porsche engine builders in the US.

[Jeff Alton]

An internally stock NA 3.0 is not making 300FWHP no matter what is bolted on to it. Period....

[Mahler9th]

15% loss? Is that a well accepted figure? Fuel injected Spec 911 motor in that #10 car. Spec 911 rules can be checked to see what internal mods are allowed if any.

In any case, I think the point of those dyno curves is to show comparisons, not absolutes. Dynos can vary quite a bit.

Like I said, talk to the people who have the experience and did the work. That is NOT me.

[Eagledriver]

As Mike has surmised, the error here is the power train loss assumptions. Based on engine dyno and chassis dyno numbers from many of the spec 911 cars, the loss is less than 10 percent.

-Andy