Do I even need idle air control?

[SQLGUY]

I am converting to fuel injection a 1982 Yamaha SECA 750. This is an air cooled inline 4 cylinder 4 cycle engine. I will be using a custom manifold with a 50mm Ford throttle body and port injection.

For a setup like this, do I need to setup for idle air control, or could I just get by with a warmup-based enrichment program?

Thanks,
Paul

[shadowplane676]

+1 to that lance. i have no IAC or fast idle valve and even on a 2 day cold soak at 40* or less, she starts up and runs fine its one less thing to break/tune

[Heribert]

but I have never been able to get idle control to work as well as I wanted
Been using MS 1 and the 2 wire Bosch valve .
So on two cars I have ended up with a very functional but slightly embarrasing solution
A 1/4 " ball alve hidden from view but easy to get at.
At start I judge the ambient temp, set the valve and start . After some 30-300 secs depending again on ambient temp I start to gradually close the valve.
Works great but not really in the MS spirit .

Both cars very auto gearbox and relied on a low, stable idle .

Promise to better myself, have started to read up a bit on stepper motor drivers
But I believe that a second idle loop by fine tuning by spark advance adjustment is mandatory for a "factory" quality idle control.
Heribert

[SQLGUY]

My thought was that the original carburetors didn't really do any idle air control, but did use a manual choke to enrich the mixture for cold starting.

It looks to me, from digging around in various articles, that idle air control is largely for two things:

1. Compensating for varying load from engine accessories (A/C, P/S, etc).

2. Reducing the amount of enrichment needed for cold start to conform with emissions requirements. It seems to be mostly for this reason that modern FI motorcycles include IAC.

I don't have the first and, for the second case, while I'd like the bike to run as cleanly as is reasonably possible for a 25 year old engine design, I expect that it will be much cleaner, even with choke-type enrichment, once converted for fuel injection, than it ever was with carbs.

The problem is, I am building a custom intake manifold. If I want to leave the option open to add IAC later, I need to at least build in the ports now. The Ford throttle body I'll probably use has a port in place for the air box side, but I'll still need to build one into the manifold for the other side of the bypass.

[S.Bretz]

I use no IAC either. I just used the cold advance and cranked it up to help it hold dile when its cold. It works pretty decent.

[chicksdigwagons]

I had the thought on my bike, somewhat in an effort to keep part of the classic feel, to have the manual choke actually open a fast idle valve or crack the throttle a nudge.

Part of what I love about the 35 year old bike is how manual it all is.

And part of what I don't is how manual it all is