ok, i am officially stuck. i have a b20vtec with itbs and i have problems with the throttle actuation.

when the engine is not running, the throttle pedal is light.

but when the engine is running,the low pressure difference between the runners and outside air are making it hard to press on the throttle pedal

a) is this normal?

b) am i running too low an rpm for idling? (currently 1k)

c) Am i supposed to run a lopeyidle with ITBs?

 

HI,

What ecu software are you using. Post some videos of your problem.

Your symptoms are not normal. Idle is more than ok but should be smooth.

Jignesh

 

a) doesnt sound normal. my throttle "pressure" is about he same running or not w/my twm's

b) & c) idle really depends on the cams. what cams are you using?

what throttles are you using?

 

you may have your throttle plates completely closed as opposed to slightly opened? and just need to adjust your butterflies slightly? which ITBs, how do you have your vaccum hooked up to your collector?

 

Well, it's tuned and been used for quite a while.
The vacuum log is a custom unit, mounted below the runners. It's a small tube. about "1 dia x 3.5" long with screwed on barbs for the hoses.

It's an early gen OER ITBs (before they made those huge linkages) which makes me think that I'm pretty much stuck with this issue unless I change the ITBs.

The MAP reading when it's below 400mbar makes the throttle resistant to opening, but if I introduce a vacuum leak, the throttle become rather light, so I tried idling higher.

Tried increasing idle to 1.5K rpm, and it does solve the problem (idles at 1.5K at 500mbar)... but it's ridiculous to idle that high on a stoplight. I am hoping to idle at 1K or less, and I think a lopey idle cam would help in this case.

I'm running 11.8CR on stock R cams, so no lopey cams on this one unless I start playing with overlap.

 

Found one of the causes, the large vacuum log I had was causing the stiffness, now I changed to a smaller volume, and throttle is loads better, still harder than single TBs, but much more managable.