MSefi.com read only forum (Jan.15,2018)

Recently read a post similar to "I have a good idle pulsewidth of 3m/s so set my cranking to 3.5m/s (warm) to 17m/s (cold)"

Well I have a good idle pulsewidth of 3.6m/s giving an AFR of 13.1,can anyone point me to where this instruction is?

1) The only Cranking Pulsewidth reference I can find is in relationship to the Req.Fuel numbers
2) What is the best idling AFR...is it 13.8 ?

Many Thanks
John

Can't answer no.1 but in respect of no. 2, it's whatever your engine wants. Now, emissions is a different matter......

So it's a case of setting all the bins at 1,crank,if it fires good,check the temp reading and that's the cranking pulsewidth for that temp....

If it doesn't fire,increase all the bins slightly and repeat...

Slowly building up different pulsewidths for different temperatures

John

I have similar concerns.

I have a very solid tune, been running the same/similar numbers for almost 4 years.

Recently I have made some changes to my setup, and now my problem lies with cranking. Once in awhile, when cold, it takes quite a few cranks before firing. Now, I can adjust idle valve cranking PW, and/or fuel cranking PW. There is basically no feedback. I can make changes, and try, but once it has cranked a few times, and/or sputtered, or started, then it no longer has any problems starting. The problem only applies to the first start, the first 10 seconds. Since there is essentially no feedback in this situation, how do I know what is going on and what is needed?

You could Datalog your starts,that's what I've been doing but not much progress so far....seems very hit and miss...

John

Ya, but what is our feedback? EGO? on the first start at -10C? Not only that, lets just go out on a limb for a moment and say that our ego in this situation is accurate and believable (thats a long limb). What O2 reading are we even shooting for? When you combine the low rpm of a crank, the low temperature of the motor, the fuel requirements of the first few revs, the ASE required to stop the motor from stalling... there are far too many variables to consider. Also it's a situation that is purely dynamic, there is nothing stable about it. We are trying to tune a transient between crank and run, almost all the inputs to ms (except maybe the tps) are changing at a very high rate. So what are you looking for in your data logs?

I think really the easiest way to do it would be to find an OEM setup as similar as possible to what we are running, and scope the injector PW on starts, at different temperatures.

Does anyone have any theory or links to any about cranking fuel/timing requirements?

Vinister

Turn everything OFF except cranking pulses,start at 0.1 and try starting,increase pulsewidths until it fires and you have your cranking pulsewidths at that temperature (and a flat battery)

John

that sounds helpful. So turn off ASE and WUE? What is 'everything'? and what about the Cranking idle valve PW? surely I cant turn the air valve 'off', the engine wont get any air at all. Any recommended procedures for tuning idle valve? I suppose the more you open it, the more fuel it will need for cranking PW. This is probably why my numbers are off, I changed my idle valve setup completely, so now my cranking PW is all out of whack for the amount of air I am giving it.