Tuning for e85???

[Japeatr]

Dsteck, so dial in a pump gas tune; fill with e and change stoich?

[DSteck]

Dsteck, so dial in a pump gas tune; fill with e and change stoich?

Yep. If your pump gas tune was already done the CORRECT way, then you can just run that tank out, put in E85, change the stoich value, and be on your merry way. It'd be wise to enrich WOT a little bit because E85 likes to be richer than gasoline at WOT. For NA applications, WOT is best around 0.85 lambda on gas, but for E85, dropping to 0.8 (or even richer) seems to work out best.

[CarsonTech]

What you're suggesting is what people are referring to as raping the tune. You end up with totally inaccurate airflow measurements.

What I'm saying to do actually requires nothing. I could take a car, drain the gas tank, fill it with E85, and ONLY change the stoich value in the tune... and the car will start right up and drive perfect. I suggest you ACTUALLY try it before saying it's wrong and complicated.

http://www.hptuners.com/forum/showthread.php?t=22448

I see what your saying and it makes sense. I am going to see if I can re-explain this for my own, and others, benefit. If you have time to read over this, let me know if I am in the ballpark. I am still trying to learn

So, after changing the stoich value in the tune to the stoich point of e85, you would have to "change the transfer to represent a range of 6.61 to 11.89" (or somehere around there, depending on the resolutin you want). This is beacuse the wideband is just spittig out a voltage for whatever lambda it is reading (depending on what resolution you set for the wideband), and you want HP tuners to read the voltage and convert it into a recognizable and usable AFR for the type of fuel you are using. And so the %error histogram can compare that value to commanded AFR, which should be around what stoich is set, or below, depending on adders like PE and such. Oh and it looks like e85 likes to run a bit richer at WOTm so change that accordingly as well. Then retune VE and MAF like ussual.

And the other way that was suggested was to scale the injectors 30%, right? And keep the stoich value of e0 gasoline in the tune (~14.68), make a transfer function in the config that will convert the voltage from the wideband to an AFR range that is around e0 gasoline's stoich, like 11-18, and then fine tune the VE and MAF?

Sorry to keep dragging this out, even though there are already tons of threads on this. I think it will benefit the rest of the members to see this discussion, me especially, lol.

[DSteck]

The first way you described is fine. The second way is raping the tune.



Make life easy, and just display commanded lambda, and log your wideband as lambda, then set up your error calculation based on that... then, there's no worry of changing the scale for the wideband reading. You don't need to retune your VE/MAF if your tune was already correct on gasoline...

[CarsonTech]

Ahhh ha! I got it now. In the beginning I was missing a few peices of info, so both ways sounded a little simular. Now I see that the way I want to do it is the first way I described. I do not like scaling injectors, but to each their own.

[DSteck]

Ahhh ha! I got it now. In the beginning I was missing a few peices of info, so both ways sounded a little simular. Now I see that the way I want to do it is the first way I described. I do not like scaling injectors, but to each their own.

Scaling injectors should only be done if the injectors flow more than the hard coded limit in the PCM.

[skatinboarding]

Roderick lol calm down man. Thanks for pulling in some threads for my side of the debate. In our community it seems as its more accepted.

Dsteck I have a question for you. In all seriousness, why is multiplying the maf scale for e85 (the method Im using) bad? I would really like to know. What can go wrong? I thought thats what the scale was for.

There is a lot of people running this method of tuning in the lsj community and it seems like no one has had a problem with it. I do finally understand how just changing the stoich ratio will compensate for the fuel needed for the ethanol.

I might just have to try this method out just for the sake of this thread. I have a feeling it will run the exact same but just out of curiosity I would like to see first hand. Roderick I will keep in touch with you and let you know how it goes. Dsteck do you mind, if I have any questions, that I pm you?

[Japeatr]

can you keep it in this thread tho? your questions may answer my questions...LOL

[Fast9C1]

You know, I have been just sitting back and watching this conversation unfold since I am green enough to Gen3 tuning that I don't want to try to contribute.

My E85 station is a ways away and through a small scheduling snafu, I couldn't get up there without throwing a splash of plain gasoline (maybe 3 gallons) in the car. I didn't change the tune (really wanted to avoid having to re-flash away from home without a spare PCM), but did watch the scanner closely just in case. It was running closed loop SD (long term trims disabled) at the time and on gas, the trims went to the max. It must have been close enough at that point since it ran well enough without any black smoke...didn't idle too well, though.

Got to the station, filled up with E85, started it back up and watched the trims immediately settle in right around 5-6% rich. After I drove around for a while to see that it was consistent, changed the Stoich AFR to 10.36962 (from 9.765) and the trims went right back to almost zero.

This tank is about half gone now and I am anticipating that I can fill up with the E85, change the stoich back to 9.765 and all will be well. Easy as pie.

[DSteck]

Roderick lol calm down man. Thanks for pulling in some threads for my side of the debate. In our community it seems as its more accepted.

Dsteck I have a question for you. In all seriousness, why is multiplying the maf scale for e85 (the method Im using) bad? I would really like to know. What can go wrong? I thought thats what the scale was for.

There is a lot of people running this method of tuning in the lsj community and it seems like no one has had a problem with it. I do finally understand how just changing the stoich ratio will compensate for the fuel needed for the ethanol.

I might just have to try this method out just for the sake of this thread. I have a feeling it will run the exact same but just out of curiosity I would like to see first hand. Roderick I will keep in touch with you and let you know how it goes. Dsteck do you mind, if I have any questions, that I pm you?

When you cheat your air flow calculations, anything that references an airflow amount (such as MAT bias or air flow modes) goes out of calibration. Also, anything that references cylinder load goes out of calibration unless you scale ALL of that down accordingly, which isn't as easy as just multiplying the table by 30%. It just spills the inconsistency into so many other areas, and is pointless when you can just change the stoich value and be done with it.

People do it the wrong way because they don't truly understand lambda/stoich/air fuel ratios, and/or because they don't know any better.

You know, I have been just sitting back and watching this conversation unfold since I am green enough to Gen3 tuning that I don't want to try to contribute.

My E85 station is a ways away and through a small scheduling snafu, I couldn't get up there without throwing a splash of plain gasoline (maybe 3 gallons) in the car. I didn't change the tune (really wanted to avoid having to re-flash away from home without a spare PCM), but did watch the scanner closely just in case. It was running closed loop SD (long term trims disabled) at the time and on gas, the trims went to the max. It must have been close enough at that point since it ran well enough without any black smoke...didn't idle too well, though.

Got to the station, filled up with E85, started it back up and watched the trims immediately settle in right around 5-6% rich. After I drove around for a while to see that it was consistent, changed the Stoich AFR to 10.36962 (from 9.765) and the trims went right back to almost zero.

This tank is about half gone now and I am anticipating that I can fill up with the E85, change the stoich back to 9.765 and all will be well. Easy as pie.

Exactly.

[skatinboarding]

When you cheat your air flow calculations, anything that references an airflow amount (such as MAT bias or air flow modes) goes out of calibration. Also, anything that references cylinder load goes out of calibration unless you scale ALL of that down accordingly, which isn't as easy as just multiplying the table by 30%. It just spills the inconsistency into so many other areas, and is pointless when you can just change the stoich value and be done with it.

People do it the wrong way because they don't truly understand lambda/stoich/air fuel ratios, and/or because they don't know any better.


Exactly.

Alright. Thanks for the explanation. Now Im understanding this but now onto another question.

So I pulled my stock maf scale (33lb injectors) up just out of curiosity and compared it to my maf table when I was tuned on gas and 60lb injectors. There was a bit of a difference but it seemed pretty close.

Then I closed the 60lb tune and pulled up my 80lb/e85 tune and compared the maf table again to the stock maf table and it was actually closer in comparison to the stock maf table than my 60lb/gas injector tune.

Now this might have to do with other factors in the tune and that is my question. Is there something else contributing to this? Lets keep in mind that my airflow/fuel is based on 100% maf, if that matters.

[macca_779]

Alright. Thanks for the explanation. Now Im understanding this but now onto another question.

So I pulled my stock maf scale (33lb injectors) up just out of curiosity and compared it to my maf table when I was tuned on gas and 60lb injectors. There was a bit of a difference but it seemed pretty close.

Then I closed the 60lb tune and pulled up my 80lb/e85 tune and compared the maf table again to the stock maf table and it was actually closer in comparison to the stock maf table than my 60lb/gas injector tune.

Now this might have to do with other factors in the tune and that is my question. Is there something else contributing to this? Lets keep in mind that my airflow/fuel is based on 100% maf, if that matters.

Why would you change your MAF table when you change injectors? The main thing you guys have to learn is to not screw with things that haven't changed. In this case injectors. You haven't changed your MAF so don't change the MAF scale. You did change your injectors, hence you adjust IFR, Offsets etc.

[DSteck]

Did you actually enter in the correct calibration data for the injectors?...

[skatinboarding]

Yes it was all the correct injector data. The differences were minimal between maf scales. Im just trying to get some answers.

macca- Question for you, How do you tune fuel trims and wot without touching the maf scale? Example a little over a week or so ago, here we just got our "summer" blends of gas to our gas stations. I noticed that my fuel trims went to about -3%ish consistantly. What would you do then?

[DSteck]

Yes it was all the correct injector data. The differences were minimal between maf scales. Im just trying to get some answers.

macca- Question for you, How do you tune fuel trims and wot without touching the maf scale? Example a little over a week or so ago, here we just got our "summer" blends of gas to our gas stations. I noticed that my fuel trims went to about -3%ish consistantly. What would you do then?

Where'd you get the injector data from?

[macca_779]

Yes it was all the correct injector data. The differences were minimal between maf scales. Im just trying to get some answers.

macca- Question for you, How do you tune fuel trims and wot without touching the maf scale? Example a little over a week or so ago, here we just got our "summer" blends of gas to our gas stations. I noticed that my fuel trims went to about -3%ish consistantly. What would you do then?

For -3% I wouldn't even worry about it.

[Dainslaif]

First off, let me say that I understand that changing stoich is the proper method, and not just because I'd really only rather change one number if that's all it needs. >_>

That being said;

This. If you leave stoich at 14.69.... the O2 sensors are going to sense the difference in O2 concentration and are going to add 30% fuel (STFT +30). The car will run lean until it compensates and if you are on narrow band sensors (LNF cobalts have a WB O2) it will not compensate properly at WOT.

As I understand it a narrowband sensor runs off a lambda measurement to determine whether the car is running lean or rich. Since adding 30% more fuel via the MAF/VE tables should cause lambda to remain around 1 on e85, why would it peg the fuel trims?

Same goes for WOT. I thought when you're WOT the fueling is calculated involving the MAF table (or VE if you have it enabled), PE table and Stoich. Basically, with the table rape method you're moving the 30% bump from Stoich to the MAF table, so it should still run more or less at the expected AFR, shouldn't it?

Thanks.

[macca_779]

First off, let me say that I understand that changing stoich is the proper method, and not just because I'd really only rather change one number if that's all it needs. >_>

That being said;

As I understand it a narrowband sensor runs off a lambda measurement to determine whether the car is running lean or rich. Since adding 30% more fuel via the MAF/VE tables should cause lambda to remain around 1 on e85, why would it peg the fuel trims?

Same goes for WOT. I thought when you're WOT the fueling is calculated involving the MAF table (or VE if you have it enabled), PE table and Stoich. Basically, with the table rape method you're moving the 30% bump from Stoich to the MAF table, so it should still run more or less at the expected AFR, shouldn't it?

Thanks.

That is true. But what your failing to also consider is a MAF does more than just apply data to resolve fuelling. Funnily enough an Air Flow Sensor is also used for measuring Air Flow for Air Flow related tables.. Who would have thought.

[Dainslaif]

That is true. But what your failing to also consider is a MAF does more than just apply data to resolve fuelling. Funnily enough an Air Flow Sensor is also used for measuring Air Flow for Air Flow related tables.. Who would have thought.

I get what you're saying, but could you give an example of a calculation using the MAF table that isn't fueling related? I don't have my HPT in front of me but I thought that's all it was used for (which is probably why people on our forums have been doing it this way instead of just changing the stoich number). A specific example might help some of the people dead set on this method to understand why it's a bad way of doing it.

As an aside, big thanks to you and DSteck. I went from knowing little about tuning for E85 to understanding it in one evening thanks to this thread. I might actually go look for a pump next time I head down to the track. :-)

[macca_779]

I get what you're saying, but could you give an example of a calculation using the MAF table that isn't fueling related? I don't have my HPT in front of me but I thought that's all it was used for (which is probably why people on our forums have been doing it this way instead of just changing the stoich number). A specific example might help some of the people dead set on this method to understand why it's a bad way of doing it.

As an aside, big thanks to you and DSteck. I went from knowing little about tuning for E85 to understanding it in one evening thanks to this thread. I might actually go look for a pump next time I head down to the track. :-)

Pretty much anything to do with idle needs to know air charge volume.