Slight surging idle issues

baldeagle · Apr 16, 2020

1989 Foxbody 347 running on a microsquirt.

Im a noob with microsquirt and tunerstudio so bare with me. I cant for the life of me figure out my slightly surging idle. It will settle and idle nice if i give a few seconds. I do see my injector pw surging and i think it is causing the AFRs to swing. Im thinking that is why it is happening but i am not sure what cells need changed.Here is a log with it surging and then it settles out half way through, along with the tune.

Thanks!

a91what · Apr 16, 2020

I need to know more about the engine please.

baldeagle · Apr 16, 2020

Sorry, it’s a 347 bottom end 10:1 CR with ported e7 heads, F303 cam, Rpm performer 2 intake, BBK 70mm throttle body.

a91what · Apr 16, 2020

Looking at the log file, the AFR is fine and relatively stable. I do see the idle valve swing with the rpm, I also see the idle advance swinging to try and get the idle under control until they settle in.
Basically the two are fighting each other.
I want you to make some changes for me.
under general settings change the VE table size from 12x12 to 16x16
change the number of squirts from 4 to 2/alternating
Disable the idle advance and get the idle valve tuned correctly first, also extend the PID ramp to target time from 2s up to 5s
PID= p-70 I-50 d-1 lower the slider to 800
change the rpm window size to 1
you should be using MAT in the initial values table lookup, You also want the initial value set so that the idle comes in a bit high and settles in to target speed.
in your ignition table, watch the blue dot as the engine returns to idle. Add some timing in the overrun cells at 1200 and lower to slow the rate the RPM falls, this will help create a smooth return.

Try these and report back.

baldeagle · Apr 20, 2020

I changed everything you recommended, except when i switched number of squirts from 4 to 2, it was so rich it barely ran so i switched back to 4. The surge is still present but better than before. i took a log just sitting idling, one with driving (log25) and idling and one with the spark adder back on(log 26) which seemed to help some. Let me know what you think my next step should be thanks!

a91what · Apr 20, 2020

If altering the number of squirts affected the fueling that heavily then your injector dead times are incorrect

baldeagle · Apr 20, 2020

Interesting. I used the data off the ford performance site. I assumed that would be accurate information

a91what · Apr 20, 2020

What injectors are you running? I assume the LU47. with larger injectors the pw becomes very small at idle.
-You have EGO set to be active at idle, this is an issue if you do not have the fuel table ready and the PID loop tuned to your installation. set this to be active above 1300 rpm
- lock the timing at 20* and turn the set screw on the TB in until the car idles above 1k then unplug the IAC valve. The idle should be steady now, tune the fuel table to reach target.
- take a 1/8th turn out of the TB screw and check the AFR/ adjust the fuel, shoot for 13.8-14.2 AFR you should be able to achieve a 850 or so idle speed easily using this method.

Do the above first, if it wont idle steady with the timing locked and the IAC out of the equation then we may have to force it.

baldeagle · Apr 20, 2020

Yes im using the LU47 injectors. I’ll give that a shot and let you know how it goes. Thanks!

a91what · Apr 20, 2020

View: https://drive.google.com/open?id=1RdgYq9_oHddJLRqjgJ5k7_j2vGhNyRlP

here is the injector info for the lu47

baldeagle · Apr 22, 2020

I entered that injector data in and did as you directed. It is not perfect but much better than it was. I could probably live with it now but let me know what you think.

On a side note, after the car is up to temp and i shut it down for a few minutes it is super lean and stalls out a time or two. It will idle but remain super lean for roughly a minute then return to normal. Im using the ford IAT sensor and have it placed in the intake tube so i dont believe it is heat soaked. I provided a log for that as well. Thanks!

a91what · Apr 22, 2020

Take a look at the after start enrichment.

most base tunes send this with a value of 25 in the final row for full hot, increase this to 35 and take the taper out to 350. this should fix the hot start issue

baldeagle · Apr 24, 2020

That fixed the hot start issue! Thanks!

It still wants to surge slightly but it is only when the electric fans are running, when the fans are off its pretty smooth. Fans kick on and the idle drops to 500 rpm after a decel then surges alittle while until it settles. Here is a log if you can see why this may be happening. Fans kick on at 200 and off at 190.

baldeagle · Apr 24, 2020

Actually i think i figured it out. The voltage was dropping down closer to 13v when the fan would come on. I added some PMW idle voltage compensation and seems to have taken came of the issue. Thanks for all your help a91what!!!

a91what · Apr 24, 2020

No problem sir

Slight surging idle issues

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