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Engine start injectors PW

Posted: Sun Dec 07, 2014 4:56 pm
by PBU
Noticed something on my log.
Why are injectors staying at zero (purple line , bottom is TPS) for long time ?
Sometimes time is shorter but they always start at 0 PW ( 1st moment that's normal of course) but take some time to rise.
Shouldn't they jump direct to start injector PW ?
I don't see prime pulse either.

PS: engine was hot

Image

Re: Engine start injectors PW

Posted: Sun Dec 07, 2014 6:44 pm
by Kurt
Prime pulse won't show in the Inj PW channel. There is no channel for this. The prime pulse happens when the EMU sees the first crank trigger tooth, so immediately when the engine starts spinning. The cranking fuel injections happens after the cam or missing tooth section is detected and the EMU is synchronized.

You only get prime pulse once after the EMU is powered up. So, your first cranking will get it. If engine doesn't start or if it stalls (and power stays on) then next cranking will not get the prime pulse, it will only get the cranking fuel. EMU has to be powered off and back on to get the prime pulse again for starting.

The batch all option gives you a lot more cranking fuel. With this off, one injector fires at a time in order while cranking. So, each injector would fire once per two revs with InjPW from the cranking fuel table. With batch all on, you get the same sequential injections, but instead of only one injector firing for each, you get all firing for each of the sequential injections. So, each injector will fire 6 times per two revs with a 6 cylinder engine. If you just turn this option on with the same cranking fuel table, you will get 6 times more cranking fuel for each cycle (4 times with a 4 cylinder).

If you have good starting with the batch all option off, but find you need more fuel for E85 starting when winter comes, you will want to turn batch all on. You will want to bring down the cranking fuel table, but it will not be 1/6th of original. Maybe 25-50% less. You will have to re-tune the cranking fuel if you change this option.

Re: Engine start injectors PW

Posted: Sun Dec 07, 2014 7:00 pm
by Kurt
Also, cranking fuel will be modified by the Fuel TPS Scale table. Usually this table is set to zero at 80-100% throttle to clear any flooding issues. You set it to 100% from 0-80% to get all cranking fuel. Or, if you want to set it to 50% from 0-20% throttle and slope up to 100% by 60-80% throttle, you can increase the cranking fuel with more throttle and also have it clear flooding at 100% throttle. This might be good to have if you haven't fully tuned colder temp cells. Setting this table to 50% will take half of the cranking fuel table value away but prime pulse will not be affected.

Re: Engine start injectors PW

Posted: Sun Dec 07, 2014 8:47 pm
by PBU
Ok ,but why is my injector PW staying at 0 for a long time when you see i start to give throttle.

Re: Engine start injectors PW

Posted: Sun Dec 07, 2014 9:06 pm
by Kurt
You'd have to post your log file and calibration to get an answer to that.

Re: Engine start injectors PW

Posted: Mon Dec 08, 2014 12:57 am
by PBU
Which settings can put the PW at 0 at start:

-fuel cut
-Idle settings
-VE table of course
-cranking fuel
-fuel tps scale

Any more ?

Re: Engine start injectors PW

Posted: Mon Dec 08, 2014 1:31 am
by PSI-Motor
Trigger sync

Re: Engine start injectors PW

Posted: Mon Dec 08, 2014 10:17 am
by PBU
PSI-Motor wrote:Trigger sync
Is ok.