E85 and cold corrections

[TimoL]

I'm not sure if this topic should actually be in the tuning section? But here's the deal:

I've switched to E85 for now and having difficulties tuning cold corrections. The starting is okay and it runs great if it just let it idle. The real problem is when I attempt to take off. Even if I apply just a tiny amount of throttle or the engine speed drops for any reason the engine will most like stall. I believe this to be because of change in manifold pressure which affects the evaporation of the fuel.  Fast throttle applications actually work very nicely, the accel enrich seems to tackle that very well.

I'ts not even very cold, about 15 Celsius (Finnish summer, yay ). I bet that at colder temps the car would not be driveable unless it's been let to idle several minutes. 

When engine is warmed up none of these problems are present. Fuel and ignition map have been tuned up to 180 kPA absolute (had to stop there because of fueling problems but that's another story).

I've attached a log and the current tune. This was a cold start (15C temp). I actually managed to stall the engine once. The logs don't show this but I'm 100% sure it was due to AFR leaning out. I took off lightly and then tried to replicate the problematic conditions by shifting a lot and decelerating & accelerating (see "Accel_and_decel.PNG").

I'm not sure if this can be tuned just by acceleration enrichment, unless switching to MAP based? To combat this, I think there would need to be a temperature based Accel Hold & Decay values. I was thinking of utilizing the Warm Up Enrichment table with the MAP Delta as load axis. But when looking at the logs, the MAP delta variable seems to hardly change at all?

 

-Timo

CurrentTune.pclr

Log 2018-06-30 2;40;04 pm.llg

[mikegt4dude]

Hi, These are my first impressions too, this table here helped clear it up for me.

credit to David V for his testing and ideas.

[Ducie54]

Add a second warm up enrichment table with E% and water temp on the axis.

[TimoL]

15 hours ago, mikegt4dude said:

Hi, These are my first impressions too, this table here helped clear it up for me.

credit to David V for his testing and ideas.

Thanks, I'll try if this works me

 

 

12 hours ago, Ducie54 said:

Add a second warm up enrichment table with E% and water temp on the axis.

 

Yes, I will definitely need different Warm up tables for Gasoline & E85. I have no plans on driving on E85 in winter tho .

[Davidv]

I have found some extra ign timing when cold helps too.

Overlay ign table with ect and load as axes. 

Thats with petrol only but would assume similar for e85.

Notice any difference with that for you, Mike? 

[TimoL]

I tried to adjust the injection timing as suggested but I made a table that has ECT as the Y-axis. When the engine is warm a timing of about 400 works best in the idle range. I have verified this by observing the AFR and transient response.

But things seem to be very different when cold. When I dropped the injection timing by 90 deg I noticed a drop of lambda value from 0.86 to 0.77 and the transient response was improved. The PW was constant.

I should try the ign cold advance as well. I pre viously had good results with my motorcycle (e85 too) wiith MS2.

Here's what I think:

When the engine is warm the fuel is injected on the hot intake valve (& port). This vaporizes the fuel just before the intake valve opens. But when the engine is cold, injecting to the closed valve does not help the vaporization, instead the fuel sticks to the valve & port walls. So the best way to get a biggest amount of fuel in to cylinder is to inject on the open intake valve. Smaller value means that fuel is injected later since its "BTDC", right ?

[mikegt4dude]

Yup you can now trim your fuel back to 0.86 lambda now.

 

Yup David that cold ignition advance table also had a good effect

 

But mostly that injection timing, I couldn't get my car up that hill in that driveway at the old house until around 40c otherwise haha

[Davidv]

On 7/4/2018 at 6:07 AM, TimoL said:

Here's what I think:

When the engine is warm the fuel is injected on the hot intake valve (& port). This vaporizes the fuel just before the intake valve opens. But when the engine is cold, injecting to the closed valve does not help the vaporization, instead the fuel sticks to the valve & port walls. So the best way to get a biggest amount of fuel in to cylinder is to inject on the open intake valve. Smaller value means that fuel is injected later since its "BTDC", right ?

Yep that was my original theory too which is what instigated the testing with myself and Mike. 
 I could end up pulling out a massive amount of fuel in idle conditions and car ran quieter and smoother.
And that was just with petrol then Mike tested with E85 to good results as well.

I'd like to have a play with E85 but my fuel system would shit a brick haha.

Ive found this works awesomely to make my car quieter and a lot nicer when cold as well, but not sure how well it translates to a map based setup (that load axis only available with maf)

There's no science to the numbers though was just a first guess to see how it pans out, and was an improvement.