RV8 Stepper Motor

[chassis 33]

I may of gotten this wrong but the stepper (on hotwire) engines, is purely added to the system to allow for an air flow when the throttle butterfly is shut. If you never intend your engine to idle, can these be removed, (why is the throttle not setup to stay slightly ajar for idle, does the stepper allow for greater fine tuning of the idle speed?)

The context of this is a race engine where, except in a minority of cases, revs wouldnt want to drop below 2k anyway, the exceptions are the paddock and holding area I guess, but even then sat there, a lumpy idle isnt going to upset anyone too much.

I'm hell bent on creating a reliable engine and if I can cut the stepper out of the setup then thats one less component count to fail.

Regards
Iain

[eliot]

You can remove the stepper idle and crack the throttle plate open a bit to maintain idle. but TBH, they are pretty reliable - even if it failed, it would only fail to idle - nothing else.

[chassis 33]

Yeah, at worst you clean them, I have some vaguely ulterior motives though, the prime one is it saves me having to make a stepper housing to mate to the Thor manifold, the Thor setup uses a PWM motor for its idle air which is incompatible with the hotwire setup.

Regards
Iain

[GreenV8S]

The amount of throttle needed to maintain a steady idle depends how hot the engine is, so unless you have some form of positive idle control you will find the idle is lower when it is cold and higher when it is hot. This in't the end of the world, I don't have provision for a stepper motor on my manifold and I've run with no idle control at all for the last year. It just means you might have to help it with the throttle for the first couple of minutes after a cold start. For a racer I don't suppose this would be any problem.

Removing the stepper motor also eliminates the problem of eratic idle speeds, the last thing you need is to be waiting on the line with an engine that can't be relied on to idle steadily so it's probably worth getting rid of it anyway just to be on the safe side.

[mongoose]

I dont use the stepper on mine,now its runs on the omex.Although i was a little aprehensive about the isc without it,it's turned out to be no problem.I dont even find the need for extra isc when the a/c compressor kicks in.Even cold idle seems to be no problem,so i'm chuffed,like you say its one less thing.I've never subscribed to the lucas hotwire system on these cars being particularly unreliable,but scince running the omex i've found it more reassuring without the afm,dizzy and stepper!