Idle dip

[Wayno]

@ztan My idle is around 0.28 and up to 0.33 when AC is on. Would I need to zero 0.3 column in addition to 0.2?

[Fizz]

@ztan @Wayno I zero'd the 0.3 column as well recently and it seems better than previously when it was only zero'd till 0.2

On a sidenote, do you think there's any inherent danger in zero-ing further up? Say to 0.4 and then push the current 0.4 to 0.6 tables one step higher on the g/rev axis?

[ztan]

Originally Posted by Fizz

@ztan @Wayno I zero'd the 0.3 column as well recently and it seems better than previously when it was only zero'd till 0.2

On a sidenote, do you think there's any inherent danger in zero-ing further up? Say to 0.4 and then push the current 0.4 to 0.6 tables one step higher on the g/rev axis?

Probably not - a lot of engines running 100% DI, and stock tune uses 100% DI higher in the rev range under full load. Only would expect it to be a problem when the DI injectors run out of headroom high in the rev range or under FI loads.

[ztan]

Originally Posted by Wayno

@ztan My idle is around 0.28 and up to 0.33 when AC is on. Would I need to zero 0.3 column in addition to 0.2?

If you're getting dip at 0.33 load with AC, I'd try zeroing up above that (or change the scaling axes so 0.2 reads 0.35 or so). If you're not getting a big dip, don't worry about it.

As an aside, I just put on a 3" overpipe back x-force exhaust and my idle has been smoother again (as well as a bit louder).

[Fizz]

Originally Posted by ztan

Probably not - a lot of engines running 100% DI, and stock tune uses 100% DI higher in the rev range under full load. Only would expect it to be a problem when the DI injectors run out of headroom high in the rev range or under FI loads.

I'm still trying to get rid of the minor stutter/hesitation when moving off in 1st and 2nd gear under light throttle and low load. Zeroing up to 0.3 has helped abit, but I noticed the problem happens up to 0.6 as well....so i'm thinking of zeroing up to 0.4 or even 0.5 to see if it makes any more difference. Running sprintex kit, stock injectors.

The current FI tune has some PI from 0.9 onwards from 3200rpm and above.

[ztan]

Originally Posted by Fizz

I'm still trying to get rid of the minor stutter/hesitation when moving off in 1st and 2nd gear under light throttle and low load. Zeroing up to 0.3 has helped abit, but I noticed the problem happens up to 0.6 as well....so i'm thinking of zeroing up to 0.4 or even 0.5 to see if it makes any more difference. Running sprintex kit, stock injectors.

The current FI tune has some PI from 0.9 onwards from 3200rpm and above.

Have you been logging your PI duty? I suspect hesitation due to PI ratios would only be a problem if you are running a PI value under 0.6ms in the non-linear injector range.

Excluding manifold leaks, I'd wonder if playing with your EL comp table will help - the intake flow changes with a blower and intercooler will likely affect VE quite unpredictably (your MAF sits before both and may not be fully compensating for them).

[Kodename47]

It's likely to be actual fueling error that's causing it. EL Comp is worth a look. If you run 100% DI and then 100% PI in those regions and see whether you can get a indication of the change in error. It may be that those need some tweaking in the low RPM ranges. You could always increase your PI latency if you think that that is causing you issues.

[steve99]

Originally Posted by ztan

Can anyone with the idle dip problem set all 3 PI/DI ratio tables to have full DI up to 0.3 g/rev load (see figure)? My theory is that it may eliminate DI/PI switchover at low IPW where the port injectors get activated in the non-linear range and send the engine transiently lean - especially if the PI scaling is unbalanced to the lean side.

As per last post, I have had a bit of hesitation at low loads (2000-3500 rpm at part throttle, 0.2-0.3 g/rev load) with bigger injectors and doing this has solved the problem for me.

done this thanks

only did it for 0.2 load (my manual trans NA car idles at 0.2 load)
smoother idle , actually dropped my idle back to 700 from 750 rpm as a result of this change
no dip when a/c cuts in, actually get a slight bump up in rpm now as a/c cuts in at idle
no rattly sound when coasting to a stop in neutral

This is on E85 , NA

[yomny]

Thanks guys for the feedback and help, im sure this will help a lot of people out there because obviously the so called dealer flash isn't helping crap.

[ztan]

Originally Posted by steve99

done this thanks

only did it for 0.2 load (my manual trans NA car idles at 0.2 load)
smoother idle , actually dropped my idle back to 700 from 750 rpm as a result of this change
no dip when a/c cuts in, actually get a slight bump up in rpm now as a/c cuts in at idle
no rattly sound when coasting to a stop in neutral

This is on E85 , NA

Glad to be of help.

[frsdiy]

I have an update on the Idle dip with the AC on. I discovered that even if you spray lubricant on the pulleys if you have the stock Crank Pulley the idle dip will still happen. I lubricated the pulleys AND installed a lightweight crank pulley and the idle dip is much less noticeable and rarely causes the annoying clacking noise when the Idle dips with the AC on.