Setting up the throttle...?

[450Nick]

The next thing I need to do this week is re-set my throttle as I've just fitted a new throttle cable and have moved a few bits around. I have wound the cable in so it draws the throttle plate horizontal on full throttle, and snaps fully shut when I come off but I'm not sure what to do about the resting position. I've heard that some applications would like the throttle plate to have a bit of a gap at zero throttle to allow air to bypass the plate and help out the idle. Currently I have the standard stepper hole blanked off and have a 2 wire type stepper plumbed in-line with the throttle bypass hose which now runs into the old breather feed just before the throttle plate and ends up in the usual place at the back of the plenum (the normal feed by the throttle linkage is blocked off). I used the old breather feed as it was the same size and helps keep the install neat but it only has a 7mm oriface as it meets the inlet as opposed to the full 15ishmm on the normal attachment.

All of this means that the only air bypassing the throttle plate will now be through a 7mm hole via a 2 wire stepper motor which will be shut during normal driving conditions (only open for cold starts). Bearing this in mind, should I wind up the screw under throttle assembly in order to let some air pass through under zero throttle as it currently shuts very tight (it is a re-machined 72mm type). If so, how much should I open it by? Or could the same affect be found by opening up the bleed screw? Lastly, if I do need to move them, does anyone know what size allen key I need? I think its an imperial type one as none of my metrics fit! I know that this will require a re-map as the air flow will change, but the car is going off for a full re-map as soon as it's running so no problems there.

For info its a 450 supercharged running an Emerald ECU so no dizzy, AFM or Lucas to worry about...

[450Nick]

...Anyone??

[rev-erend]

Nick - I think the older TVR V8's using the 14CU system had no bypass.

I think if you initially set the gap at the throttle plate at 25 thou (inch) and adjust tickover from there..

I have the old efi manual but have not found a setting yet..

[rev-erend]

Just found a section in the old manual that states that no gap is needed.. but I guess there must be enough leakage of a small gap in the EAV (extra air valve) or the optional stepper motor for AC equiped cars.

If you have none of these .. well I cannot see the harm in a small gap on the throttle plate - you can always move it up or down to suit under running conditions.

[450Nick]

Thanks Alan, I'll either open it up a wee bit or crack the idle screw open a bit and see how it goes from there. Seems like the best route to take as I can't see how any air would get through under normal idle conditions otherwise!

[Johno]

I run without any IACV, just on a part open thrttle, although the engine still draws too much through the breeather side currently which I need to sort. There is an adjuster for the stop position, however you often need to remove it completely and then re screw it in from above as they're usually set to be adjusted from below, a little allen key grubber screw.

Didn't read all your post so excuse if you've already written this.

My idle is then set up from the throttle open position only, no motors needed. The gap will depend on what your engine will demand/stand.