Need advice on ITBs and fuel management system for 1980 911

[JamesMacT]

Hi all,

I would really appreciate some help and advice on ITBs and EFI for my 911 Porsche ST.

I am new to the forum, and so have looked thought the forum for most recent advice on EFI systems for ITBs. However, have not found answers to my questions below. Any help greatly appreciated.

Background
I had a ground up restoration/rebuild of my 1980 911 S. Enhanced to a 3.2l ST look with a 964 header and crank. I kept the Autronic fuel management system and had it tuned/remapped, but have had quite a lot of problems with it. The car revs quite high at standstill (1000 RPM) and often stalls when I change gear, or at idle.
I want to change to ITBs with a new EFI system.
A friend suggested I use AT Power’s Throttle Installation Kit with MoTec ECU.

Questions
• Do any of you have experience with AT Power’s ITBs?
• Are there other ITB manufacturers you have used and would recommend?
• AT Power use MoTec M130 ECU. Do any of you have experience with MoTec M130, or are there better/newer system for ITBs.
Thanks again for any help you can give.
James

[Peter M]

James,
I'd suggest you figure out why the current engine runs poorly first before you go and change anything as there is a fair chance changing the ECU won't fix the problem.

Sure you haven't go an air leak in the intake somewhere?

[Arlo911]

Why not use a standard Motronic ECU with a Steve Wong chip? That would be the most cost effective and reliable option.
As for ITBs there are several options, PMO, AT Power, Kinsler, Rothsport, Jenvey, Nux's rollerbarrels, Rasant, RHD.
Better put some cash aside for several hours of mapping too... Find a good tuner that has experience with the Engine management you will be using, AEM or Motec seems to be the more popular options.
IMO putting itbs on an otherwise standard engine isn't worth the cost. Also keep in mind that an engine is a complete system, from intake size and length to header size, compression ratio, cam selection etc.
ITB's do sound great though!

[jpnovak]

Completely agree here. The Autronic is fully capable of running your 3.2 with whatever modifications are inside. Of course, that capability is always up to the skill level of the person/people that configure, assemble and tune the setup.

Sounds to me like whomever setup your Autronic didn't know how to properly interface with the stock idle control valve. I see the stock ICV in your picture. Its that silver cylindrical item in the top center of your manifold with the hose connecting by your air filter. These are pretty easy to configure. This link may help.

http://www.mrm-racing.se/bag/IAC.pdf

Additional places to look are fuel cut returns coming into idle off closed throttle, timing at low MAP readings (closed throttle) and overall idle speed control (balance of ICV and idle bypass screw.

Regarding ITBs, These present more complex problems to tuning. Idle control is not a strong suit for ITBs. Depending on your cam setup the cost/benefit may not favor ITBs.

[PhillIB]

Hi,
I run Triumph ITBs and Megasquirt2. Links if you are interested.

https://www.impactbumpers.com/forum/index.php?/topic/30976-phils-cis-to-efi/
https://www.impactbumpers.com/forum/index.php?/topic/32160-triumph-itb-conversion/

[3rd_gear_Ted]

Irregardless of the ITB choice, the ECU and the mapping done will need ongoing tech support. Its all about the support going forward. Still in the due diligence phase

[Mahler9th]

Are you in Europe?

I ask because the shop in the US with the greatest experience with AT Power is Reno Rennsport. They have done a bunch with these ITBs and I believe have worked closely with AT Power in the UK to develop the 911 application

I know the guys at Reno Rennsport really well-- they are good friends, and co-owner Mat Lowrance does my engine work (and has for ~20 years).

There are quite a few ITB choices... if I were going ITB near term, there would be no question-- AT Power. They make more power than conventional butterflies, and don't cost nearly as much as slides.

For ECU's there are a lot of good choices. My Haltech ECU is really, really old, but if I were going to upgrade for any reason, my starting point would be Haltech from a performance versus price standpoint.

[Mahler9th]

I think single plate throttle bodies have more idle challenges and part throttle than ITB's with cammed up engines. For years I ran a cammed up 3.8 liter engine with a large aftermarket 80 mm throttle body, and even with lots of tuning effort, it had idle and part throttle challenges.

For the part throttle stuff, my friend/engine builder recommended some "old school" throttle linkage mods that were easy to do and made a huge difference. Feel free to PM me for details, or check some old threads in these Forums.

[targa72e]

More information on your engine specifications might be useful. The single throttle intake you have with standard 3.2 Carrera or 964 cams should be pretty easy to tune. If you have cams with large overlap it will never work properly with common plenum intake do to reversion at low RPM, If the cams have large overlap the ITB would fix that issue as the intake revision on overlap is blocked by the throttle plate. That said in general ITB's are more difficult to tune than single throttle body.

john