12P runs very lean when cold

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12P runs very lean when cold

Postby Charlescrown » Tue Feb 26, 2019 9:35 am

I can't figure this out. I have tried adjusting the cold map but it makes no difference to the tune. Help appreciated.
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Re: 12P runs very lean when cold

Postby vlad01 » Tue Feb 26, 2019 9:49 am

It will be this map.

You have probably tuned it at a very high temp where the table suddenly goes rich which makes everything else at the lower temps lean. This weird kink in the high temp area is a factory fudge for stopping hot lean restarts. I normally change them to be linear and then tune the VE table and then you can change those area's back after it's done so the lean hot restarts don't happen. It's a bit of a cluster fuck that inverse temp table.

inverse temp.jpg
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Re: 12P runs very lean when cold

Postby Charlescrown » Tue Feb 26, 2019 10:45 am

Thanks. I have made it look closer to the actual in the areas of concern and will wait for the engine to cool down and try again. Will post the outcome.

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Re: 12P runs very lean when cold

Postby vlad01 » Tue Feb 26, 2019 12:08 pm

I can take a few goes to get it right. I would check against coolant temps just before full warm up, say around 80 or so and use that point as the reference. Move the whole VE table up or down to get it to match at that temp. Then work the rest of the inverse table from there.

It is likely just the whole VE table is offset some amount due to the weird values up at the top of the inverse table. Most engine will operate on the verge of that area so it does have influence depending on driving conditions. traffic and start stop will tend to go into that bad area of the table, open road barely ever hit it.

For me living in the country and tuning on open roads my inverse temps mostly only ever hit high 80s and low 90s so my tunes need little work for the inverse table. However once I tuned in the city and it was heat soaked all the time the inverse temp vs the VE went out of whack and did the same, real lean areas during warm up.


What engine is it anyway?
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Re: 12P runs very lean when cold

Postby delcowizzid » Tue Feb 26, 2019 1:02 pm

Target air fuel is saying 13.1 you may be over the cold engine coolant temp thresh hold so it isn't using that table.and that table doesn't do idle its open throttle
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Re: 12P runs very lean when cold

Postby Charlescrown » Tue Feb 26, 2019 1:56 pm

The cold engine temp is set to around 58 deg so below that. vlad01 I did what you said and it brought the air fuel ration down from 15.3 to 14.3 @48.5 deg. The target was 13.6 so it looks like a little more adjusting and it should be OK. I am using 20% E85 which I figure needs a hot air fuel ratio of around 13.5:1. Thanks for the advice.

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Re: 12P runs very lean when cold

Postby antus » Tue Feb 26, 2019 4:10 pm

The injector opening times vs volts table can also cause this. Small variations in fuelling due to temperature when the injectors are close to the opening threshold can really show up inaccuracy in the opening times table which are less obvious with unintentional corrections baked in to the higher fuel delivery parts of the VE. You could easily be delivering more than 50% inaccurate fueling only at idle because the pcm thinks the injectors are open when they are not, or vice versa for very small pulsewidths.
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Re: 12P runs very lean when cold

Postby delcowizzid » Tue Feb 26, 2019 7:48 pm

E20 you need to change the stoich a/f ratio constant and the fuel table to 13.12 ish instead of 14.7 for closes loop and smaller numbers for wot so the ecu can work its magic and calculate fueling correctly would probably help A great deal.
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Re: 12P runs very lean when cold

Postby Charlescrown » Wed Feb 27, 2019 6:53 am

Thanks antus. The injectors are supposed to be L67 but I have no idea if their genuine so the voltage offset is a guess but seems ok when hot. The charge temp scale did make a big difference. delcowizzid yes I understand that but I have turned off closed loop for tuning purposes and will get to that when I turn it back on. Thanks everyone for your input.

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Re: 12P runs very lean when cold

Postby delcowizzid » Wed Feb 27, 2019 7:51 am

It's not just about closed loop its about fuel calculations in the ecu if it says add 7% to the target when cold 7% of 14.7 is a lot different that 7% of 13.12.
Should be able to get the l67 injector data out of a stock bin easy enough there's a post on here by the1 about the vs ecu being 0.5ms wrong when used in 808 that needs to be accounted for
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