Could someon please explain ITB's?

[Reaper930]

Originally Posted by James Brown

you can't really do that with a turbo in theory. As all the air goes into the turbo then the pressurized air goes to each cylinder. so it winds up being the same common plenum to each "throttle body". The air is being pushed in the cylinder vice being sucked in as with carbs or itb's. You can efi a turbo.

I did it on my twin turbo 3.8tt with TWM ITBs and MoTeC M600. Wasn't that hard to tune either.

[Raceboy]

Not a 911, but my 931 race-car with my custom made ITB turbo setup with original 924 GTR intercooler (but with custom end-tanks).
I'm in process of making similar setup to my 911 2.5 litre short-stroke turbo engine.

[Lukesportsman]

I'm with JohnJL, in that I'd like to hear more what others have done for connecting to an IAC. I've done EFI without using an IAC though with a large plenum in past with success. I (just last 2 weeks) have got another car running with EFI. This one has much more overlap and a very small plenum and IAC. When cold, that IAC is working overtime (read loudly) by the data and she still pulses some.

I'm now concerned ( just got test stand in) as I look at my slightly cam'd 3.0 with Jenveys that this could be an issue.

Is anyone RUNNING IAC with ITB? Maybe its time to start the google search for images maybe the Cobra kit cars as they are going this route a lot lately.

[Raceboy]

IAC is not an issue, but you should connect it separately from vacuum manifold. GSX-R/Hayabusa ITB's have two vacuum nipples per throttle and while one of each is connected to vacuum manifold on the 993 ITB project for FPR, ECU and brake booster signal, the second set of vacuum reference is for IAC and it works perfectly.

[Jim2]

On my custom ITB 3.6 build I installed one vacuum port on each TB and manifolded them together then used the vacuum signal for MAP sensor and FPR. Also made the fittings large enough to act as a idle air balance to minimize synchronization issues. Originally I didn't think MAP would work and I had planned to put a "T" in the circuit for an idle air solenoid which worked just fine for fast idle during warmup, but when I started running with the MAP sensor the idle air solenoid I installed messed with the signal to the MAP sensor so I ditched the IAC solenoid.

If I added a second set of vacuum taps onto each TB I could plumb in the IAC without issue. This is along the lines of what Raceboy says above.

[Lukesportsman]

Sounds good and thanks for the ideas on MAP and IAC as separate parallel circuits.

[zelrik911]

Originally Posted by Raceboy

Hayabusa throttles already have TPS on them. I have two of the throttles left (I bought two 4cyl sets of them), I can take a photos of it.

For early 2bolt intake the best route is to have the intake flange watercut from 10mm aluminium and then weld short (20-30mm long) runners to them and connect the ITB's to those with silicone hoses. Hayabusa throttles already have fuel injector mounts and one would just have to either make a custom fuel rails out of extrusion .

Hi Raceboy
Can I ask some questions. Which precise model Hayabusa throttle kit did you use? When I look at eBay pictures of throttle sets some look easier to separate from 4 down to 3.

Have you already done a throttle set for a 2bolt intake motor ( 3 litre SC ) ? Do you have contacts for fabricating the 2bolt intake flanges & runners.

Regards
Peter in Melbourne