se7ensport
|
| posted on 7/5/12 at 06:35 PM |
|
|
Balancing ITB's Part 2.
Looking for confirmation that I'm going about the right approach to setting up my ITB's:
1. Set butterfly stops so that they only just close completely (without binding); will use a torch behind to check closed position.
2. Set balance between bodies so that they visually open and close in unison, this will be roughly correct.
3. Start car, warm to operating temp and balance idle circuit using manometer.
4. Increase tension on throttle cable so car idles at 2500, accurately set balance between throttle bodies using manometer I.e. fine tuning step 2.
Thoughts?
|
|
|
|
|
HowardB
|
| posted on 7/5/12 at 07:49 PM |
|
|
in the absence of other replies, I can only comment that it seems logical,...
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again  and goes zoom)
|
|
|
se7ensport
|
| posted on 7/5/12 at 09:39 PM |
|
|
From a lot of reading around bike forums suggest the throttle linkage should be balanced first with the idle air closed, once the butterflies are
accurately synchronised the idle circuit can be fine tuned. I'm struggling to see which is the most logical.
|
|
|
Dusty
|
| posted on 7/5/12 at 10:08 PM |
|
|
Are you still talking about balancing them off the car but on the manifold?
I think you have to consider the throttle body with the accelerator cable acting on it as the reference body. This will usually be at one end and
numbered one. It's immediate neighbour will be two and so on.
Slacken off all stops and linkage screws. Close all idle air balance screws.
Slowly adjust the throttle stop on the reference body to the point where it is just opening the merest fraction. Now slowly adjust the linkage screw
between one and two until two butterfly is also just opening the merest fraction. Then on to the link between two and three and finally three and
four. (If you have a central cable it will be acting directly only on one body, three or two, and this is the body that will have a throttle position
stop. Set this stop first. Then if the reference body is two, do the link to three, then one and four.
You should find now that if you fractionally loosen or tighten the stop on the reference body all the other butterflies will move in sync with the
reference body butterfly. There should be no delay, even between one and four. If they don't you have more adjusting to do in the linkages
between each throttle butterfly. When the linkages are perfectly adjusted all butterflies move as one.
Bolt on the manifold and repeat the above. Connect up the throttle cable making sure there is a bit of slack. Recheck that they all move in sync with
the reference bodies butterfly, both on adjusting the stop on the ref body and with the accelerator cable.
Set the ECU idle to 1000. Start the engine and adjust reference body stop roughly in the middle of the range that gives an idle of 1000. Don't
touch the idle screw on the reference body at all. Sit in car go brm brm for a while till engine is up to temperature. Reset idle to 1000 with ref
body stop if it has wandered. Check flow of all barrels. Regardless of how accurate you have been, at this stage the flows will be all different.
You now go along the linkages again starting between one and two and adjust the flow of two to match one. Use the linkage only, either in or out. OK?
Then reset idle to 1000 if needed on the reference body stop and do flow of three on the linkage between two and three. Reset idle to 1000 on the
reference body stop and do flow of four using the linkage screw between three and four. Reset throttle stop to mid range 1000.
You might find that you cannot get a good match. Open the throttle stop of the reference body a quarter turn and go along the links again. Or you may
find you can get a good match but can't get the idle down. Close the throttle stop screw a quarter turn and go along the links again.
You can now reset the ECU to give idle 800 or whatever you want your base idle to be. Adjust throttle stop again to mid range that gives idle of 800.
Do flows and go along the links again to match.
When you are very close you can make final tweaks to flow with the idle screw of two, three and four, possibly needing tiny tweaks of the links as
well but try to avoid this. I never touch the idle screw of the reference body.
Well that's how I do it. Whenever I have gone to a rolling road session they always check for matched flows early on when setting up and they
have never needed to adjust them.
|
|
|
