Description

I currently have a set of ITBs which are set up as in figure 1 above (from this point of view, the butterfly opens clockwise, "towards" the injector). Is there any impact on fuel-air mixing, idling or small throttle input running by changing the direction the butterfly opens (fig. 2)?

For reference, the distance between the butterfly spindle axis and the injector port in the side of the throttle body is ~30mm and the butterflies are ~36mm diameter IIRC

Another point is that I have two banks of throttle bodies (it's a V6) - if there is a difference either negative or positive to having the two banks opening in different directions relative to the injectors? (As below)


Description

Chris

Wouldn't have thought it would make a difference as air will be drawn in past the butterfly on both sides of the spindle ??
IMHO of course

That is my thought also... I suppose considering draw-through flow, air would be being pulled into the port equally either side of the spindle. Hmm.

I have a cunning plan.

If your fitting them to a Mazda v6 it may be worth getting in touch with Clairetoo , IIRC she has carried out a similar conversion already

Yeah, it was my conversion. And it's her throttle bodies on my car. Unfortunately I'm having a weird problem with the bodies unbalancing themselves...!?! Trying to plan a change in the linkage to try and solve the problem.

Chris

Not too sure what the problem is with balance..............I havnt adjusted mine for about two years ?
I think if you go with the second setup as drawn , there would be some odd mixture problems at part throttle as the airflow (I think) would be directed away from the injectors on one set , but towards them on the other .
I think you may be having air leakage somewhere - what sort of sealant did you use on the `bodies and adapter plates ?

I can't really see that either way will affect mixture. If the mapping is ALPHA-N then surely whatever the TPS tells the ecu to deliver to the injectors will be the same, so it will all end up in the cylinder anyway.

Personally i prefer picture 1.

I believe (with no engineering background) that more air will get drawn in a more turbulent manner past the injector, this will help atomisation and the fuel to mix into the airstream.

quote:

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Originally posted by RazMan
I can't really see that either way will affect mixture. If the mapping is ALPHA-N then surely whatever the TPS tells the ecu to deliver to the injectors will be the same, so it will all end up in the cylinder anyway.

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Yeah - that was my fear. I've found that the main problem is that the downward-pointing crank (for the cross-link) on the right-hand head is hitting the head casting, and stopping the butterflies on that side closing. I suspect that the springs trying to close the butterflies on the left-hand bank against the impact of hitting the right-hand head with the crosslink was causing the "nose" to rotate around the left-hand bank's spindle - but was not being allowed to return due to the tightness of the connection.

Between bodies on the same bank, the balance holds nicely, but it's this cross-link which is giving me the headache. I'll take a piccy tonight of the interferance.

Otherwise, the car's all ready for it's MOT - especially since I remembered I had a spare set of front disks and pads to replace the 2-year's-worth-of-rust disks and useless-when-cold EBC Redstuffs. The car actually stops now! I just need it to go...

Chris