M20 RHD ITBs idle issues

[zaq123]

Ok. Setting up a Haltech and run into a few issues.
Base tune was rich at idle. Tunner had to lean it out a couple of times and now feeling is ok. The problem I'm having with the hight idle. It starts ok when the car is cold (ITBs fully closed, IAC plugged), if I bleep the throttle, It goes high to like 2500k and stays there with butterflies closed. mind you ITB butterflies are fully closed, idle screw is not even touching. If I choke trumpets, the car drops idle as expected. I understand ITBs don't close fully (I feel suction with my hand) but not sure what's happening. Smoke leak test showed no vacuum leaks except around TB butterfly shafts which is expected from what I understand.

Any ideas what's happening here ?

[digger]

you need to add a return spring so the throttles close consistently against the throttle stop. in my experience (very early version 10 years old) the springs provided are inadequate.

This is what i use, i note that the throttles rotate in the opposite direction and throttle cable setup is totally different now

[zaq123]

Thank you for that. I brought my spring to the max 180' as per RHD manual. I think my problem was idle screw that was protruding a little further and ever so slightly keeping throttles open upon the return. Combination of the spring and adjusting the screw got me idling steady at around 1k rpm. And that with ITBs fully closed. A little high in your opinion?

[digger]

Thank you for that. I brought my spring to the max 180' as per RHD manual. I think my problem was idle screw that was protruding a little further and ever so slightly keeping throttles open upon the return. Combination of the spring and adjusting the screw got me idling steady at around 1k rpm. And that with ITBs fully closed. A little high in your opinion?

what do you mean by ITB fully closed? The throttles are supposed to be always open slightly.

With the ICV blocked off i set throttle opening (governed by the idle stop) so it idles at 750-800rpm fully hot and heat soaked without assistance from ICV. Then the ICV pumps it to 950rpm or higher on cold start and during warmup.

[zaq123]

I meant IAC blocked off, butterflies fully closed, idle screw is barely touching the stop pin. Idle is just under 1k

[digger]

what is you idle ignition timing when the engine is hot?

[zaq123]

what is you idle ignition timing when the engine is hot?

this?

[digger]

you could try idle timing at around 15 degrees at 1000 rpm to see if that allows you to get the idle speed down assuming you have already played with the idle stop

[zaq123]

you could try idle timing at around 15 degrees at 1000 rpm to see if that allows you to get the idle speed down assuming you have already played with the idle stop

just a quick question about ITB throttle plates and adjustments. RHD ITB manual states that the pedal and cable travel does not go beyond WOT of ITBs. Ok that makes sense, adjust pedal stop etc.
Regarding ITB plates. IS WOT position needs to be right where ITB butterfly(plate) is exactly at 90 degrees? Does typical throttle body plate is considered at WOT even thought it's not at exactly 90 degrees?
Do I adjust the cable to have ITB plate at lets say 86 degrees for example and there is 4 degrees to account for any assembly hot/cold expansion so there is no stress on the assembly/cable?
Or WOT ITB plate has to be exactly at 90 for WOT and that's where pedal needs to get it to precisely?

As I side note, I'm familiar with TB adjustments on motorcycles. For example Ducati throttle plates stop at around 85 degrees at WOT because maximum airflow is already achieved at 82-85 degrees. Which I guess makes sense because at those opening angles, butterfly profile is no larger than Throttle body shaft diameter itself.

Would similar logic apply here with these ITBs?

[digger]

just a quick question about ITB throttle plates and adjustments. RHD ITB manual states that the pedal and cable travel does not go beyond WOT of ITBs. Ok that makes sense, adjust pedal stop etc.
Regarding ITB plates. IS WOT position needs to be right where ITB butterfly(plate) is exactly at 90 degrees? Does typical throttle body plate is considered at WOT even thought it's not at exactly 90 degrees?
Do I adjust the cable to have ITB plate at lets say 86 degrees for example and there is 4 degrees to account for any assembly hot/cold expansion so there is no stress on the assembly/cable?
Or WOT ITB plate has to be exactly at 90 for WOT and that's where pedal needs to get it to precisely?

As I side note, I'm familiar with TB adjustments on motorcycles. For example Ducati throttle plates stop at around 85 degrees at WOT because maximum airflow is already achieved at 82-85 degrees. Which I guess makes sense because at those opening angles, butterfly profile is no larger than Throttle body shaft diameter itself.

Would similar logic apply here with these ITBs?

Ideally when the pedal hits the pedal stop the cable has pulled the throttles to 90 degrees to maximise airflow.

You may need to clock the lever arm very slightly on the throttle shaft (from that shown on the install instructions) to get the sweet spot as the lever arm needs to be close to but not make contact (some small clearance so the pedal stop is the actual stop) with its own stop/post at that 90 degrees.

In you're case if the throttles are only at 86 degrees i doubt it matters as they are unlikely a restriction