Flex Fuel Tuning

[16GoManGoHC2]

1940 aircharge...at what rpm? Thats.....a lot lol

Yea, a little blending and smoothing inside the blower along with a ported inlet plate, snout and FM 95mm TB work well together on a 2.85 Hellraiser. A bit more tuning next spring and I’m sure it will put down 950 but I’m getting close to running out of fuel, may have to add a BAP or just call it enough especially if I don’t upgrade the bottom end this winter. I’m pretty happy with the results.

 

[Hpindy]

Yea, a little blending and smoothing inside the blower along with a ported inlet plate, snout and FM 95mm TB work well together on a 2.85 Hellraiser. A bit more tuning next spring and I’m sure it will put down 950 but I’m getting close to running out of fuel, may have to add a BAP or just call it enough especially if I don’t upgrade the bottom end this winter. I’m pretty happy with the results.

A properly ported supercharger does work pretty well . If I was you I would get a set of 1300's and a dual BAP then you will not have to worry about fuel volume for a little while .

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[Speedy!]

That's a good log, that thing is moving a lot of air for sure. My car sees high 1800s low 1900s in 50 degree air on a stock supercharger and a 2.72 pulley.

I figured out the positive fuel trims on my car. Back when I dialed in the injectors I wanted to always error on the side of it calculating LESS ethanol than actual, if it weren't dead on. I didn't want it to be way off, but I kept hearing "up to 10% is normal" so I made sure that 10% was lower than actual rather than higher. In my mind this was the safer way to do it so that the car wouldn't ever give timing for full E85 when only E50 was in the tank. The side effect to that is when it does calculate on the lower side of actual the fuel trims have to go positive to maintain commanded fueling.

I did some testing in the beautiful weather we had this weekend. Dropped 5 gallons of measured E82 in a near empty tank. In 82 seconds the car calculated it as exactly E82. Fuel trims cruising around are within 5-7% positive now and at WOT they were 12-15% positive. Previous fuel that measured E85 the car calculated at E80. It makes sense now, as with the amount of fuel volume E85 requires over gasoline a small under calc in ethanol content will require a larger trim for fueling to be right. As long as it doesn't go out of the adjustment range all's good, but I may experiment with adding a few breaks in the injector scale to see what that does, and there's one other table that I think impacts the target ethanol content I might play with just for fun.

 

[16GoManGoHC2]

That's a good log, that thing is moving a lot of air for sure. My car sees high 1800s low 1900s in 50 degree air on a stock supercharger and a 2.72 pulley.

I figured out the positive fuel trims on my car. Back when I dialed in the injectors I wanted to always error on the side of it calculating LESS ethanol than actual, if it weren't dead on. I didn't want it to be way off, but I kept hearing "up to 10% is normal" so I made sure that 10% was lower than actual rather than higher. In my mind this was the safer way to do it so that the car wouldn't ever give timing for full E85 when only E50 was in the tank. The side effect to that is when it does calculate on the lower side of actual the fuel trims have to go positive to maintain commanded fueling.

I did some testing in the beautiful weather we had this weekend. Dropped 5 gallons of measured E82 in a near empty tank. In 82 seconds the car calculated it as exactly E82. Fuel trims cruising around are within 5-7% positive now and at WOT they were 12-15% positive. Previous fuel that measured E85 the car calculated at E80. It makes sense now, as with the amount of fuel volume E85 requires over gasoline a small under calc in ethanol content will require a larger trim for fueling to be right. As long as it doesn't go out of the adjustment range all's good, but I may experiment with adding a few breaks in the injector scale to see what that does, and there's one other table that I think impacts the target ethanol content I might play with just for fun.

My E% always reads low so with E85 it’s only giving spark for E79 as it reads 5-7% low sometimes. I’d like to get it more accurate which would mean increasing something. What is that by chance?

 

[Speedy!]

I'm confused. On E85 it's reading E89? That would mean it's reading higher than actual I think.

 

[16GoManGoHC2]

I'm confused. On E85 it's reading E89? That would mean it's reading higher than actual I think.

Sorry, typo, that should have been 79 not 89, I’ll edit it to correct for future readers

 

[Speedy!]

Gotcha. So there's a table in the spark tab that is a flex fuel multiplier. It's scaled to blend the gasoline timing table and the alcohol timing table. Mine starts to feed the alcohol timing in about 60% and maxes at E85. However what I've found is that even at E70 I'm nearly 100% E85 timing, like maybe 1 deg difference.

Having said that if you are comfortable doing so you can lower the alcohol percent where you get max timing to something below 85%. 1.00 is full timing for reference.

Edited to add: I think it's pretty hard to get the calculated ethanol closer than 5-7%. The injector fuel trims are a major contributor to that calculation and as you know they do move around a bit even on gasoline. 5-7% is pretty dang good and might not be worth chasing for 12-14hp difference in 1 deg of timing but if you have the time and drive go for it.

 

[16GoManGoHC2]

Gotcha. So there's a table in the spark tab that is a flex fuel multiplier. It's scaled to blend the gasoline timing table and the alcohol timing table. Mine starts to feed the alcohol timing in about 60% and maxes at E85. However what I've found is that even at E70 I'm nearly 100% E85 timing, like maybe 1 deg difference.

Having said that if you are comfortable doing so you can lower the alcohol percent where you get max timing to something below 85%. 1.00 is full timing for reference.

This is what I’ve done already but I don’t think fueling is then right? Being that the higher the E% the lower the commanded lambda is ( I think? ) if I have 85% E in the tank but only target fueling for 77% but giving it the timing for 85% won’t the mix be lean by target lambda and more prone to knock? I have this concern as one of the ways to combat knock (on gasoline at least) is to throw fuel at the knock area verse taking spark away so being lean would be more prone to knock? I know the wide bands will adjust fueling but they adjust to a target which would not be correct if E% is not correct?

 

[Speedy!]

That's a problem if your fueling is wildly different between gasoline and E85. Mine are very close on lambda so it doesn't matter on mine.

 

[16GoManGoHC2]

That's a problem if your fueling is wildly different between gasoline and E85. Mine are very close on lambda so it doesn't matter on mine.

Don’t know, all I know for sure is target lambda and AFR differ as the E% climbs. I’m super new to this stuff, just learned how to use HPT about 6-8 weeks ago. I’ve got MUCH to learn!!

 

[Hpindy]

Don’t know, all I know for sure is target lambda and AFR differ as the E% climbs. I’m super new to this stuff, just learned how to use HPT about 6-8 weeks ago. I’ve got MUCH to learn!!

That you do young grasshopper

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[Speedy!]

It can be a bit confusing, especially with flex fuel and all the multipliers. I'd recommend getting a very good handle on standard gasoline fueling first, and forget AFR and focus only on Lambda. That'll make it a lot easier when you start thinking about flex.

The fueling table for my FF tune is COMPLETELY different than my strategy on just a gasoline tune.

 

[Hpindy]

It can be a bit confusing, especially with flex fuel and all the multipliers. I'd recommend getting a very good handle on standard gasoline fueling first, and forget AFR and focus only on Lambda. That'll make it a lot easier when you start thinking about flex.

The fueling table for my FF tune is COMPLETELY different than my strategy on just a gasoline tune.

And I will you guys know if there is much different when changing injectors .

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[Speedy!]

Spent some down time during the holidays to play with my flex fuel tune a bit. I'm still seeing positive fuel trims, so it must be expected for my model year. I'm seeing some items in my tune, as well as a stock 2016 Hellcat tune, that are modified to understand ethanol in 2018 and don't exist in 2019, and 2020 stock tunes I have that I think impact the trims.

These variables are in the stock 2016 Hellcat tune and not in 2019 and 2020. In the 2018 tune I have it's a table with ethanol % down the side rather than a fixed numeric like below.



I've now gotten my alcohol calcs to within 8-10% on Shell 93 consistently, I tested 4 times. On ethanol they're within 2%. I'm finding the sweet spot for me is in the E70 to E75 range to get max power and reduce the pressure on the fuel system in this cool air.

 

[Speedy!]

Upon further inspection only the 2018 Demon CRATE pcm has the table with ethanol reference. The base Demon tune doesn't reference those variables at all. Things that make you go hmmmmmm.

 

[16GoManGoHC2]

Those are the areas my tuner played with to dial in the E% as well, I’m 2016 also with a tune based on a 2017 or 18 previous tune the tuner used as a base it looks like??
I’m talking with Rick at Tapped about fuel pressure 81 psi at 94 commanded and 89% Pump DC and injector duty cycle ID1050X’s 85-86% on 85% E at 35 F ambient in minus 1000 DA 1950 Air Charge his opinion was the stock fuel pressure sending unit is restricting fuel volume to the rails. He suggested bigger injectors OR upgrade the fuel rails to Fore Rails with the center feed and new style pressure sensor with its Tee’d into the connection not pass through like the stock sensor is. He said fuel pressure would most likely not increase more then 1-3 psi but injector DC may gain 5-10% up top because there’s less pressure loss in the rails at the injector inlet verse stock setup. So the choice was upgrade to ID 1300’s or FIC1200’s and retune or try the rail theory. Since I just got this tune pretty dialed in I hate to start over in the spring with new injectors and I came across a Fore Rail set up with center Feed and lines and the sensor at a great price I’m going to try that route out and see if Ricks theory nets anything. If I could gain back 5-10% injector DC snd get down to 75% Inj DC at the same DA I was seeing 85% Inj DC I’ll be golden with the present setup for all of next season at least. I’ve been running 85% E for the past 2 weeks and the car hasn’t recalculated any other number then 85% with 3 fills now. Upon fill is goes up and down 83-87 % but settles right back to 85% in less then 10 miles and stays there. I ran a street 1/4 the other night which netted almost 142 mph in the 1/4 so I know it’s making good power now and pretty consistent following DA. Minus 1000 DA I get 141-142 1/4’s, -250 to +250 I see 139, 600-1000 DA I see 137-138, and 1500-2000 DA I see 136-137 1/4’s. Injector DC varies from 85-86% at minus 1000 DA to 78-80 at 2000 DA, I see corresponding Pr and Air Charge as well with the changing DA. It’s amazing how much more power is made as the DA gets deep negative. If only traction was there when it gets 35-40F out to make that DA currently where I live. I ran about 30 1/4’s in the past 3 weeks or so logging the changes and times with varying DA.

 

[Speedy!]

Good info. I was seeing 80% inj dc at 1700 aircharge, 6500rpm, and E75 today. DA was probably 200ish.

 

[fubar569]

Spent some down time during the holidays to play with my flex fuel tune a bit. I'm still seeing positive fuel trims, so it must be expected for my model year. I'm seeing some items in my tune, as well as a stock 2016 Hellcat tune, that are modified to understand ethanol in 2018 and don't exist in 2019, and 2020 stock tunes I have that I think impact the trims.

These variables are in the stock 2016 Hellcat tune and not in 2019 and 2020. In the 2018 tune I have it's a table with ethanol % down the side rather than a fixed numeric like below.

View attachment 30966

I've now gotten my alcohol calcs to within 8-10% on Shell 93 consistently, I tested 4 times. On ethanol they're within 2%. I'm finding the sweet spot for me is in the E70 to E75 range to get max power and reduce the pressure on the fuel system in this cool air.

Some of those values sound vaguely familiar to me. I will have to check and see what I have in my 18 FF tune.

Which table were you peeking at in the 18 tune? I want to say I remember a table with ethanol percent down the side and what the appropriate FAR would be for the given percentage?

Odd that it would be in the carte PCM but not the locked factory. Wonder which OS it is?

 

[Speedy!]

It was under the o2 sensor section of fuel.

 

[Speedy!]

Here's more detail on the differences I'm seeing:

This is the info from a Demon standard PCM. Notice no reference to Rich/Lean for O2 settings. This could have been because HPT hadn't mapped some items yet or something though.





This is from the Demon CRATE PCM. Notice the table for Rich/Lean:





From a 2019 Red Eye factory tune, doesn't exist at least under the O2 section where it was in 2018.



Finally, a 2020 Red Eye which has about half the values under O2 section. No idea why, again could be HPT hasn't mapped them dunno.