How to tune for E85 using a maf recalibration

[EmPeEs6]

If you tune for a certain E-mix, let's say 25% E85, using an adjusted maf calibration to account for the increased fueling needs (i.e. maf curve increased by ~10%), what else has to be done:

- shift the "wot area" in the ignition and fuel part throttle tables from load 2.0 (and above) to load 2.25? (-> are load row values > 2.0 used by the ecu at all?)
- adjust the whole ignition tables (by shifting rows, inter- and extrapolation) so that the original assignment is met (i.e. for example with the new maf cal you set ign. for load 1.1 to the corresponding ignition value from the old maf cal tune (-> at load 1.0) and so on)
- increase timing (at least for wot) up to 20+x at rl
- lower wot afrs (to ~12.0)
...
Anything else?

[phate]

The tuning process is the same, you just need to realize the calculated load values will be x% higher, based on the x% maf scalar you're using to compensate for the E85. [Just confirming that you're on the right track.]

So anything that uses load should be considered. You can shift the OL/CL transitions upward, shift your ignition and fueling tables upward, etc etc. [You should also scale your ignition tables so you have resolution above 2.0 load. Yes, they work.]

For the AFR's, you use the same methods you used before, even the targets. O2 sensors measure lambda and convert it to whatever scale you're using - 14.7:1 in this case. Stoich is always stoich no matter what fuel you're using. I can explain that better if you don't understand.

[rfinkle2]

^ on point.

Only one thing to look after is if you scale the ignition tables, I've seen that automatically rescale the fueling tables.

Originally Posted by EmPeEs6 If you tune for a certain E-mix, let's say 25% E85, using an adjusted maf calibration to account for the increased fueling needs (i.e. maf curve increased by ~10%), what else has to be done: - shift the "wot area" in the ignition and fuel part throttle tables from load 2.0 (and above) to load 2.25? (-> are load row values > 2.0 used by the ecu at all?) - adjust the whole ignition tables (by shifting rows, inter- and extrapolation) so that the original assignment is met (i.e. for example with the new maf cal you set ign. for load 1.1 to the corresponding ignition value from the old maf cal tune (-> at load 1.0) and so on) - increase timing (at least for wot) up to 20+x at rl - lower wot afrs (to ~12.0) ... Anything else?

Don't just keep adding advance,, you will never knock on a strong concentration of e85. Pretty much, search > advanced search > phate > *timing* for details.

[EmPeEs6]

Originally Posted by phate The tuning process is the same, you just need to realize the calculated load values will be x% higher, based on the x% maf scalar you're using to compensate for the E85. [Just confirming that you're on the right track.] So anything that uses load should be considered.

That's clear, I just forgot to mention that (of course) the target load values and all other load depending tables have to be adjusted accordingly, too.

You can shift the OL/CL transitions upward, shift your ignition and fueling tables upward, etc etc. [You should also scale your ignition tables so you have resolution above 2.0 load. Yes, they work.] For the AFR's, you use the same methods you used before, even the targets. O2 sensors measure lambda and convert it to whatever scale you're using - 14.7:1 in this case. Stoich is always stoich no matter what fuel you're using. I can explain that better if you don't understand.

Do I really have to adjust/shift the fuel tables (apart from the wot-tables and the wot section in the part throttle tables, which makes it necessary to redo any interpolation upwards to lower load regions)? The increased fueling needs should be handled by the artificially increased maf cal. and for part throttle conditions there are still fuel trims corrections.

Concerning ign., the "timing database" here on msf should be a good starting point, and as far as I remember, for high E-ratios (>50%?) it's necessary to tune ignition with respect to the maf behaviour instead of looking for the occurrence of knock.

The meaning of lambda (which is the measured observable) and the difference to afr (used for internal calculations) is clear to me. Since I use VersaTuner I always do lambda-tuning.

[phate]

For the fueling tables, I just meant shift them upwards so the transition to richer fueling targets doesn't occur sooner than it needs to happen. You'll see worse mileage without moving that transition to higher load regions. [True for all fuels, actually.]

I do not believe in the maf behavior method for tuning timing. For a street tune, I still only go up to my comfort zone and looking at VD results, then get the car on a dyno where conditions are better controlled to take it the rest of the way up.

[EmPeEs6]

Originally Posted by rfinkle2 Only one thing to look after is if you scale the ignition tables, I've seen that automatically rescale the fueling tables.

What is the "automatic rescale of fueling tables"?

[sidekick]

This is my biggest gripe with VT. MAF scaling for E85 is a pain in the ass compared to Cobb's Fuel Injector Scalar.

[EmPeEs6]

Originally Posted by sidekick This is my biggest gripe with VT. MAF scaling for E85 is a pain in the ass compared to Cobb's Fuel Injector Scalar.

100% agreement - and just because of one single missing tuning parameter...I wonder why they included the fuel specific gravity but didn't provide access to the scalar...

[sidekick]

Originally Posted by EmPeEs6 100% agreement - and just because of one single missing tuning parameter...I wonder why they included the fuel specific gravity but didn't provide access to the scalar...

I honestly want to switch back to the AP mainly because of this feature and IMO, ATR is more refined than VT. But then I'm out ~$400, because VT is only a software license that is not transferrable and a ~$100 dollar cable.

They said they are going to be adding it to the next release, but who knows when that will happen. As far as I know it is only two people actually working on development. I believe I emailed them back in june/july when they told me that and no news yet.

[rfinkle2]

Originally Posted by EmPeEs6 What is the "automatic rescale of fueling tables"?

My apologies for not being more clear. When you guys were discussing rescaling the load axes, I have noticed that on occasion, when you scale the load axis e.g., on the ignition maps, some of the other load axis (as an example in this case fuel) are also altered unintentionally.

@sidekick; if you send me some logs I'll fit a decent curve on them for you.

Tag me if you need help.

[EmPeEs6]

A direct change of the load axes scaling is not possible in VersaTuner, that's why I was a little bit confused...

[phate]

Not a big deal, it will just ride the last load line through the rpm's. In the olden days, when we first started using E85 with AP/ATR, we didn't have fuel scalars or scalable load axes. Many, many cars were tuned like that and they did just fine (and made great power!). Scaling the MAF curve is pretty simple, and from there it just takes a normal MAF cal (maybe two if you are a ways off).

[sidekick]

Originally Posted by rfinkle2 My apologies for not being more clear. When you guys were discussing rescaling the load axes, I have noticed that on occasion, when you scale the load axis e.g., on the ignition maps, some of the other load axis (as an example in this case fuel) are also altered unintentionally. @sidekick; if you send me some logs I'll fit a decent curve on them for you. Tag me if you need help.

Thank you for the offer Rob! I'm just going to get the car re-tuned for E85 soon, because I've added some hard parts since finishing my tune with Justin anyways.