cranking pulsewidth

wuffwaff · Post by **wuffwaff** » Mon Apr 23, 2007 12:16 pm

Hi,

I´m just trying to change from MS-II to MS-II extra.
I´ve changed/filled out most of the tables etc. but I´ve got a problem with the cranking pulsewidth.
It is not in ms anymore but in %. I thought it was in % of required fuel but the default values are way to high for this.

My req fuel = 17, PW at -20°C = 12.8ms and at 65°C 4.2ms

What would this be in %?

thanks,

William

Post by **jsmcortina** » Mon Apr 23, 2007 12:20 pm

Try starting with the default values. Remember that during cranking it injects fuel on every event. So this is equivalent to 4 squirts simult on a 4 cyl engine.

James

mtlcafan79 · Post by **mtlcafan79** » Mon Apr 23, 2007 1:00 pm

How do we tune cranking pulsewidths? Mine takes a while to fire when starting. Sometimes I will let go of the key and it starts immediately on the second turn of the key. Do we just keep adding fuel if it takes too long to crank? To me it's hard to tune as it either starts or doesn't. There doesn't seem to be much feedback otherwise.

Post by **muythaibxr** » Mon Apr 23, 2007 1:18 pm

Just keep increasing the value at that temperature until it starts on the first try. I've always done that, and have never had an issue getting started after I've got it dialed in. For some people, first start of the day is a little different from starts after that.

Ken

wuffwaff · Post by **wuffwaff** » Mon Apr 23, 2007 1:27 pm

Hi,

isn´t it possible to convert my values to a percentage value? The car starts very well with those values and I don´t want to start tuning again.

William

Post by **jsmcortina** » Mon Apr 23, 2007 1:34 pm

Fair point and yes it is.
If you temporarily set yourself to 4 squirts simulataneous and remember the lower ReqFuel value then calculate a %age of that.

James

mattd860 · Post by **mattd860** » Mon Apr 23, 2007 1:44 pm

My required fuel is 15.5ms (2 squirts simultaniously). If I wanted a PW of 5ms, what will the formula be?

I tried 15.5 * X = 5ms but this isn't correct because 'X' ended up being somewhere around 2ms.

wuffwaff · Post by **wuffwaff** » Mon Apr 23, 2007 1:49 pm

thanks,

had just figured out how to do it with the stim but this is much simpler. Default values were a bit lean at lower temperatures. The 65°C value was almost spot on though.

William

wuffwaff · Post by **wuffwaff** » Mon Apr 23, 2007 2:27 pm

Hi,

somehow it doesn´t ad up.

I get a min req fuel of 17/4=4.3

To get 4ms at 65°C I would set the cranking pulse to 4/4.3=93%

The problem is that this returns a cranking pulse of 3.68ms instead of 4.

To get it right I have to set it to 135%

So now I´ve set everything by setting the stim to a given coolant temp, writing down the pulsewidth and changing the percentage accordingly.

The next problem is that 135% gives 4.0ms but 459% (at 0°C) gives 10.8ms instead of 459/135*4=13.6ms

Am I overlooking something?

William

Post by **jsmcortina** » Mon Apr 23, 2007 4:17 pm

Injector opening time perhaps? I didn't think of that earlier.

James

wuffwaff · Post by **wuffwaff** » Mon Apr 23, 2007 11:01 pm

Yep,

that´s the one. Thanks!

William