Why are most professional "tuners" doing Flex Fuel timing wrong?

[gmtech16450yz]

This subject came up elsewhere so I figured I'd throw this thread up here for you smart guys to comment on.

I've looked at the tunes from several well known tuners and vendors, specifically looking at how they set up a vehicle for running E85. It appears to me that the common theme or approach is to simply add ignition timing to the AFR Correction/Alcohol table (12635). All the "Professional" tuners files I've looked at recently only had values added to this table and the other tables are still zeroed out. WTF???

Sorry but to me this seems like the second stupidest way to properly tune for E85 that you could do. The first obviously is simply adding ignition timing to the main High Octane table, that's a good way to blow an engine as soon as your customer goes from running E85 to pump gas. (Which amazingly enough, I've also seen done from "reputable" tuners. And on top of that they copy the High Octane to the Low Octane so the ECM really has no possible way of protecting itself from massively excessive ignition timing.)

So correct me if I'm wrong here. The way these guys are doing this by only adding timing to the AFR Correction table means that they're ONLY getting additional/different ignition timing when in PE or COT. WHY ON EARTH WOULD YOU WANT THAT? The whole point of running E85 is the fact that it needs/is ok with very different ignition timing than pump 91 or 93. So why would you want to still run on your 91/93 ignition timing during 90% of your driving and engine modes? I'll post a couple screen shots below, the first one will be of a log from a well known shop. The white trace is Flex Fuel Timing, the green is EQ Ratio (commanded). As you can see, it's only modifying the ignition timing when it's in PE. So the rest of the time the customer is getting no added benefit from running E85 as far as ignition timing goes. I would even take it one step further, without modifying the ignition timing for the E85, the engine could actually be running WORSE or MAKING LESS POWER than if it was running 91/93 pump gas. So during 90% of this customer's driving the engine is basically running on the wrong ignition timing. Again, WTF? Am I missing something here? Or is this yet another example of just because a "tuner" knows how to change values in a tune and load it in a car, it doesn't mean he knows what the h#ll he's doing?

There's some smart guys on here, can you jump in and let's discuss this? Thanks!

Here's the first screen shot showing the flex timing changes... (The flat part of the white trace is at zero degrees added. The cursor is at max added during PE. So for 90% of this 11 minute drive the ignition timing was basically at 91/93 pump gas timing. Oh yeah btw, this engine was showing an alcohol content of 75%. If he was everyday driving normally or cruising down the freeway for hours and never got into PE, he'd have been running on pump gas timing the whole time.)





Here's the table that I believe should/needs to have values in it. I've never done an E85 tune and left this table zeroed out. This screenshot is from a very well know tuner's E85 with a flex sensor tune...





This is the table I've seen most tuners modifying. Even still, do they think E85 doesn't need/want different ignition timing below 2k rpm? So it's ONLY modifying timing in PE and NEVER below 2k rpm. Weird...




Even the Max Torque modifier table is left zeroed out. Really?...

[schpenxel]

I've always used and seen others use the flex fuel timing adder table that you're saying no one uses, so I'm a bit confused.

And obviously the mult vs comp table is one you want to work with too

[dreksnot]

Last tuner just added timing to the PE spark adder table for alcohol, while the other tuners had not even looked at it - claiming GM does stuff the difficult way. I have the FF sensor. Running 91 was the same-same. Running E85 was okay, I guess; still used the "regular" spark tables. Thought I'd be cute and copy over a Flex Fuel Spark table from a stock GM 6.2L FF vehicle tune. I did make some minor tweaks here and there to smooth it out. It had negative timing, and of course, positive timing depending on AF and RPM throughout the table. I swear the car ran smoother and my MPG appeared to have jumped with my first attempt with 55% alcohol in the tank. I zeroed out the PE spark adder for alcohol for now until I feel the FF spark table is dialed in. I still need time to try different alcohol contents and see how the Multi vs Comp table plays its proper role. Not slamming any tuners as that job is way above my paygrade and knowledge - but my results played out well and I'm anxious to play with it more when the weather warms up here in sub-freezing CO.

[gmtech16450yz]

Thanks guys!

Schpenxel- I think you'd be surprised at the names behind some of the tunes I'm talking about. Maybe even shocked. I think it's way more common than you think. Obviously the way I've made this thread I doubt seriously any big name tuner is going to come on here and say they don't use the Flex Fuel Spark table.

I think what might be interesting is to have some of the people on here look at their tunes and see. Not everyone on here is driving on their own tunes, some have tunes they've paid for and are here trying to learn more about it. It looks like dreksnot did exactly that. BTW any tuner that would say "GM does stuff the difficult way" or implies that they know how to tune better than the guys at GM is an idiot, plain and simple. They are certainly not stupid at GM, their hands are obviously tied by a hundred different factors that the average guy tweaking his tune isn't. Duh. The truth is that you can learn a lot from looking at stock tunes and how GM does things, I do it all the time. Oh btw, dreksnot mentioned negative timing values in the flex fuel tables of some stock tunes. Yes, GM does that. You have to remember a big reason they do the things they do is because of emissions. Advanced ignition timing can put their tailpipe emissions through the roof really quickly. For instance, they really don't want too much timing advance on decel. That doesn't mean the engine runs better that way, it doesn't.

And dreksnot, good job! Don't ever sell yourself short compared to "tuners". (btw if anyone wondered why a lot of the time I put tuners in quotes, it's because I believe that title is given out FAR too easily. Anyone can claim they're a "tuner". It doesn't mean they are.) There's absolutely nothing wrong with second guessing and experimenting yourself on a tune from any professional tuner. That's what's so awesome about this forum, somebody will look at a tune they've gotten and question something, ask on here about it and they'll quickly learn if the tuner did the right thing or not. And yeah, going from pump gas to even E55 should be a noticeable difference IF it's tuned correctly. There's so much midrange/mid load area that can benefit from more ignition timing when on Ethanol. That's a big part of why these tuners only change the PE adder table, because doing it the right way takes more time. If you only add timing when it's in PE, the customer will notice the WOT power increase and not even realize they aren't getting any advantage anywhere else in the throttle/load range. What they don't notice, they usually won't complain about. Brainless, poor tuning if you ask me.

So guys, take a look at your tunes, specifically at those tables. If you're running on any blend of Ethanol and that Flex Fuel Spark table is zeroed out, you're leaving a bunch of power, better gas mileage and better driveability on the table.

[schpenxel]

Interesting. I'll have to do some looking around and see then. I was just copying the way GM does it and figured that was the easiest way. I thought everyone else did it that way too.. guess not

[tommytuner]

I've seen a handful of "Reputable" tuners do it like you're saying as well. Initially I was setting mine up by copying all of the modifiers from a GM flex tune and dialing in from there. I've since come up with a base to start from that's a lot closer to where I typically end up, but again-I'm populating *all* of the same tables GM did. As noted, I tend to hear that my way of doing things just drives better than the other guy.

It's been my opinion that it's just easier for them to shortcut it. Most guys in socal are "tuning" a car in 4 pulls or less....

[GHuggins]

This isn't done as the engine had other problems, but this is one I just did attached... Tear it apart - I don't really care It's got some minor problems - it's setup to run full timing for ethanol at 60% - put down 940 to the tire... Drives pretty decently...

If you really pay attention to those "pro tuning" jobs your going to notice how detuned the 93 octane tune is and how much timing they're adding for the E85 - I believe they're doing this to push more E85 tunes by saying E85 gains 70 to 100hp on these minor modded motors - not to mention how little they've actually done for their customers in the tune - typically from what I see it shouldn't be adding much over 6 to 8 degrees for the E85... So they partially get away with just adding in the higher rpms as much as they are in the base adder cot/pe table because of that... I've found that E85 likes timing down low, so I know not having that added timing there is robbing "their" customers...

I also don't believe all of the ecm's out there will properly reference the multiplier table if your just using the cot/pe table - the E67 does, but I don't think they all do - wouldn't be the first time I was wrong though...

Heck I've even seen some of these "PRO" tuners tunes adding timing for regular gas in the COT/PE tables - talk about lazy and cheating the customer!

[dreksnot]

This isn't done as the engine had other problems, but this is one I just did attached... Tear it apart - I don't really care It's got some minor problems - it's setup to run full timing for ethanol at 60% - put down 940 to the tire... Drives pretty decently...

If you really pay attention to those "pro tuning" jobs your going to notice how detuned the 93 octane tune is and how much timing they're adding for the E85 - I believe they're doing this to push more E85 tunes by saying E85 gains 70 to 100hp on these minor modded motors - not to mention how little they've actually done for their customers in the tune - typically from what I see it shouldn't be adding much over 6 to 8 degrees for the E85... So they partially get away with just adding in the higher rpms as much as they are in the base adder cot/pe table because of that... I've found that E85 likes timing down low, so I know not having that added timing there is robbing "their" customers...

I also don't believe all of the ecm's out there will properly reference the multiplier table if your just using the cot/pe table - the E67 does, but I don't think they all do - wouldn't be the first time I was wrong though...

Heck I've even seen some of these "PRO" tuners tunes adding timing for regular gas in the COT/PE tables - talk about lazy and cheating the customer!

Do gots some questions for you GHuggins - you mentioned E85 likes timing (added) down low (presume all over). GM actually pulls timing in the low AF, mostly mid-RPM range. But you don't (or aren't) in your attached tune. Also, you don't mind any attention to Alcohol Adder (for Max Torque Timing). Any particular reasons for heading that direction? And, you're targeting 60% and up as the max timing benefit. So, can I presume that any Exx% above 60% runs about the same, and hit max benefit - because that's what I've heard, anything above E60 runs about the same comparatively to E70, E80, etc.

[GHuggins]

This particular car is only ever going to see 60 or 70 percent which is why it's setup as such. I am pulling timing out at peak torque. Timing tables are completely tuned on the dyno. I do stomps from idle to 3000 rpms to dial in the lower areas.

I typically don't put any values into the max torque timing adder table simply because the ethanol table is dialed in about as good as I can possibly get it for cruising, idling and wot pulls from idle and the torque timing adder will both limit and add timing based off of the torque model which as of now we haven't fully gotten down on how to correctly tune... This is why I try to rely solely on the flex spark table...

[schpenxel]

I did the same thing regarding "full" timing before E85+. I didn't want it to add more if customer got a hold of some E85 or E90 vs. the E70 it was tuned on. It was already almost 800 on stock long block, I figured that was about enough.

I'll check out your tune later

[LSxpwrdZ]

I see this all the time. What most people think is you want more timing advance everywhere with ethanol based fuels and that is far from the truth. Take notes from a factory flex fuel calibration. You'll notice that at light load (lower g/cyl) areas the flex adder table actually pulls timing advance away and as load increases you reach a point where timing doesn't change at all and under heavy load timing advance is added.

The tools are in the editor to make a silky smooth timing table for both when its on gasoline and ethanol blended fuels.

Here is a recent CTS-V Flex Fuel setup that we did... Notice the table isn't just blocked etc. This being an adder table to the other main spark table you have to factor that in when making this table.

[GHuggins]

I always get better fuel economy out of the cars adding a small amount of timing around cruise and lighter load areas... Plus the engine usually runs much smoother...

[Higgs Boson]

Ethanol is not race gas, it's not gasoline. Combustion properties are different and like Dr. Short illustrates, you need less spark at light loads than gasoline but it can handle more at higher loads.

However, it is correct to properly utilize the Flex adder table if you have a proper flex tune, not just add to main spark unless it's a straight ethanol tune without a sensor and you reflash every time you change fuels.

[GHuggins]

I'll have to try the negative timing in the adder table again next then - I haven't seen any benefits to negative timing in this table before or negative timing benefits to the flex spark table either - I've been getting about as good a fuel economy from E85 as I do from 93 minus 1 to 1.5 mpg of course with the minor positive timing...

As far as keeping the timing tables smooth - I always paste special add to the main timing table and adjust timing according to this - no weird feelings at all when switching between the tables... Would be curious to see how this would turn out with James's table above...

I'll re-evaluate for any benefits once again for doing the negative timing...

[mJolnir]

This is some interesting thread, pumps around here only sell 89 octane fuels, so doing flex fuel tune seemed like a better option to tuning on race gas and have to reflash.
my car is a bolt-ons + vvt stage 1 cam 2010 camaro SS, at the beginning i only activated the sensor but didn't populate any ignition timing adder for alcohol and the car would stumble and die on decel, then i copied a 5.3 flex fuel timing table and was surprised to see that the low load areas where actually taking timing away and the car wouldn't stumble and die anymore, i tough that on decel it would need more timing so it wouldnt stumble, but it actually stopped stumbling when taking timing away.

Now, comparing my NA tune to GHuggins' boosted tune im surprised to see that he has more timing than i do almost in all the map(high octane timing map), including hard to get parts like really low rpm very high load, this is something i have seen in a couple other tunes also, how do you guys go around tuning parts like 0.76g@600RPM or the low load high rpm like when the throttle is closed and you are on decel?

camaro 2010 E85-4 track NA.hpt
for reference, this is my tune, its for 89 octane and E40 since its on the stock injectors

[GHuggins]

Eddy brake, stock knock sensor settings to begin with, low compression, inefficient blower - dial in low rpm timing while tuning the VVE... I actually hit boost when I can at idle to tune all of this in... I also do stomps from idle to dial in the lower ignition timing - you can leave 70 to 80 hp on the table down low if you don't bother to do this... Not to mention the fuel economy you leave on the table...

I also don't have any issues with deceleration - maybe my high octane table is just still too detuned for the setup? But I haven't had any of these issues on any E85 tune I've done? Is everyone else tuning the E85 torque model? I had issues before touching that...

[GHuggins]

This is some interesting thread, pumps around here only sell 89 octane fuels, so doing flex fuel tune seemed like a better option to tuning on race gas and have to reflash.
my car is a bolt-ons + vvt stage 1 cam 2010 camaro SS, at the beginning i only activated the sensor but didn't populate any ignition timing adder for alcohol and the car would stumble and die on decel, then i copied a 5.3 flex fuel timing table and was surprised to see that the low load areas where actually taking timing away and the car wouldn't stumble and die anymore, i tough that on decel it would need more timing so it wouldnt stumble, but it actually stopped stumbling when taking timing away.

Now, comparing my NA tune to GHuggins' boosted tune im surprised to see that he has more timing than i do almost in all the map(high octane timing map), including hard to get parts like really low rpm very high load, this is something i have seen in a couple other tunes also, how do you guys go around tuning parts like 0.76g@600RPM or the low load high rpm like when the throttle is closed and you are on decel?

camaro 2010 E85-4 track NA.hpt
for reference, this is my tune, its for 89 octane and E40 since its on the stock injectors

I just looked at your tune - you need to take all of your adders into account - your running WAY more timing than I am - look at your gas adder... Then your running WAY more timing than I am on E85 - attaching some pics with your full timing being taken into account plus you said you have the adder populated to aid with decelerations - it's zeroed out?

[GHuggins]

I also didn't take into account your gas adder - SO add another 3 to 4 degrees for 6000 rpms up on that

[mJolnir]

I just looked at your tune - you need to take all of your adders into account - your running WAY more timing than I am - look at your gas adder... Then your running WAY more timing than I am on E85 - attaching some pics with your full timing being taken into account plus you said you have the adder populated to aid with decelerations - it's zeroed out?

no, when i populated the flex fuel spark table it stopped stumbling

[GHuggins]

Ok that makes sense - e85 loves timing in the mid airmass areas where your adding a lot - not sure you needed that much, but that will fix take off stumbles - negative timing for deceleration stumbles - don't know - haven't had that problem before?