aftermarket ecu /tunerstudio chat /help ...rich idle

[steveo3002]

i have a microsquirt on a polo , batch fire injectors

whatever i do i cant get it to run a lean idle , barely passed mot today for a 1988 car so co hovering around 3.5% hc was high too

so i fiddle with it , lean out the afr table around idle , anything much leaner than 13.8 idle gets uneven and see the afr dial spiking lean to indicate a lean mis fire/ guessing thats where the high hc is from ...richen to 13 or 13.5 and the afr needle sits rock solid , steady idle all great apart from its pig rich

okay i can get mot man to not mind too much , but it used to run much leaner on a carb

injectors are correct size and factory fit for this engine in a later model

so who has similar with batch fire ? can it run lean /mot pass or am i chasing my own tail and accept it wants to run 13.5 or so

[Tye Green]

batch fire using both injector channels?

have you tried changing the timing at idle ?

[steveo3002]

Tye Green said:

batch fire using both injector channels?

have you tried changing the timing at idle ?

yes both channels

and yes messed with timing....i got it into the 14 , can hear a lean mis , see it on the gauge , i tried timing from 2-26 degs and nothing helped the mis

[Tye Green]

have you set up injector dead times / is idle voltage consistent ?

[Tye Green]

also consider that the higher ambient temps this time of year can have a greater impact upon idle intake temps if the bonnet is shut.

this might be relevant at mot time if they have the bonnet shut with engine running for a while as they check other stuff like lights /seat belts etc. (i.e. afr was fine when you set it up with the bonnet open but when bonnet's shut at mot time the under bonnet temp can rise)

[steveo3002]

batt voltage is steady

deadtimes , i set it to what others with the same inj /car used , bit beyond me to figure it out myself

it does almost seem like theres no /poor injector control at low m.s

[Tye Green]

steveo3002 said:

batt voltage is steady

deadtimes , i set it to what others with the same inj /car used , bit beyond me to figure it out myself

it does almost seem like theres no /poor injector control at low m.s

what injectors are they? stock / bigger / what size compared to stock / snide copies etc?

[steveo3002]

stock for the car , original bosch /vag , have been sent away for cleaning /testing

0280150719 030906031A BOSCH

said to be 155cc , id buy another proven set with data , but theyre pretty small , would be easier if it took a popular size

[steveo3002]

any pointers on measuring dead time at home /diy

or anyone offer a service that can measure it , does sort of sound likley that could my issue

[GreenV8S]

I set up a simple test rig with a variable frequency/duty cycle signal generator and the usual pump/filter plumbing, injector squirting into a sealed jar, all in an enclosure. That's enough to confirm you've got a good spray pattern and consistent flow rates across all injectors under all conditions. And you can see how it behaves around the very low duty cycles you're using at idle and what errogation delay you need so you know what range of flow rates you can achieve consistently and what parameters you need to achieve that.

[fatjon]

I would retard the timing 5 degrees or so in the idle area, that will make the idle RPM dip. Fix the idle speed with a touch more idle throttle opening. The improved cylinder filling at idle will make it less cantankerous about a leaner idle mixture.

This has been my go to fix for this problem in a couple of decades of using micro/megasquirts. It usually works to a greater or lesser degree though not always and I never tried it on your engine.

[steveo3002]

fatjon said:

I would retard the timing 5 degrees or so in the idle area, that will make the idle RPM dip. Fix the idle speed with a touch more idle throttle opening. The improved cylinder filling at idle will make it less cantankerous about a leaner idle mixture.

This has been my go to fix for this problem in a couple of decades of using micro/megasquirts. It usually works to a greater or lesser degree though not always and I never tried it on your engine.

appreciate the reply , ive tried timing all over the place and nothing seems to help it , its around 15 deg at the moment

what would you say the leanest a batch fire should /can run at?

[GreenV8S]

fatjon said:

I would retard the timing 5 degrees or so in the idle area, that will make the idle RPM dip. Fix the idle speed with a touch more idle throttle opening. The improved cylinder filling at idle will make it less cantankerous about a leaner idle mixture.

This has been my go to fix for this problem in a couple of decades of using micro/megasquirts. It usually works to a greater or lesser degree though not always and I never tried it on your engine.

I do the same - but it does make the idle quite a bit hotter.

[fatjon]

steveo3002 said:

fatjon said:

I would retard the timing 5 degrees or so in the idle area, that will make the idle RPM dip. Fix the idle speed with a touch more idle throttle opening. The improved cylinder filling at idle will make it less cantankerous about a leaner idle mixture.

This has been my go to fix for this problem in a couple of decades of using micro/megasquirts. It usually works to a greater or lesser degree though not always and I never tried it on your engine.

appreciate the reply , ive tried timing all over the place and nothing seems to help it , its around 15 deg at the moment

what would you say the leanest a batch fire should /can run at?

A 1988 car does not need to run super lean to pass the MOT. 13.5:1 will pass easily but not if it’s missing as that drives up the HC. For your car the limits are 3.5% CO and 1200ppm HC, not at all hard to achieve.

[fatjon]

GreenV8S said:

fatjon said:

I would retard the timing 5 degrees or so in the idle area, that will make the idle RPM dip. Fix the idle speed with a touch more idle throttle opening. The improved cylinder filling at idle will make it less cantankerous about a leaner idle mixture.

This has been my go to fix for this problem in a couple of decades of using micro/megasquirts. It usually works to a greater or lesser degree though not always and I never tried it on your engine.

I do the same - but it does make the idle quite a bit hotter.

Yes, but only for 20 minutes if you know what I mean🤣