Dyno Results, TSP Longtubes, E85
Race Director
Joined: Jul 2007
Posts: 10,961
Likes: 2,643
From: Texas Hill Country
Awesome, thanks for answering both of my questions! Interesting to see that stoich is set to 14.1084 across the board. What kicks the car over into 'alcohol' mode as per the AFR correction tables.. If the car is deemed to be running alcohol, in power enrich mode.. it pulls a bit of timing relative to gas mode.. but only because there is a separate table that adds timing in flex fuel mode at high cyl airmass. In HPT, this modifier table is under "misc" and has it's own multiplier table based on fuel comp; thus E50 WOT would actually run less timing than garden variety E10. It would add half of what the "Flex Fuel Spark" adds to the main spark table and then pull it back out based on the alcohol AFR correction table. In fact, in some places.. the Flex Fuel Spark adder table adds less than AFR alcohol correction takes out.. So there are some places in which E85 would run less timing than standard E10. There must be yet another mult/mod table I'm missing!
This tune exceeded my already high expectations for complexity and layers of multipliers and adders. Yikes.
This tune exceeded my already high expectations for complexity and layers of multipliers and adders. Yikes.
no one ever accused a factory tune of being good. in fact the typical gm engine and trans tune sucks.
Intermediate
Joined: May 2009
Posts: 48
Likes: 0
From: Katy TX
I believe I saw your car there last week. Looks nice. I have a white C7 also. You are in the right hands with PF. I have known them some time and never hear anything but good stuff. They tuned my car too and I am very happy so far.
Last edited by scoates; May 10, 2015 at 06:00 PM.
Thread Starter
Burning Brakes
Joined: Oct 2012
Posts: 873
Likes: 86
From: Katy Texas
Yes, that was my car, for those who wonder AFR is right at 13.0
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 0
Light Loads timing needs to be less than regular gasoline, only at higher loads do you need more timing.
Quote from Greg Banish
"All else being equal, the laminar flame speed of ethanol combustion is faster than that of gasoline. Faster flame = less spark advance required to deliver peak pressure at the right point of the engine cycle. Ethanol has a faster burn rate than gasoline. It just has a much higher AKI (knock index) so you are rarely limited by knock at WOT which allows you to run more timing at high load. At high load, we're typically limited by gasoline's relatively low knock threshold. Since the knock threshold of alcohols are higher, you can run closer to MBT timing without getting into knock at high load."
Quote from Greg Banish
"All else being equal, the laminar flame speed of ethanol combustion is faster than that of gasoline. Faster flame = less spark advance required to deliver peak pressure at the right point of the engine cycle. Ethanol has a faster burn rate than gasoline. It just has a much higher AKI (knock index) so you are rarely limited by knock at WOT which allows you to run more timing at high load. At high load, we're typically limited by gasoline's relatively low knock threshold. Since the knock threshold of alcohols are higher, you can run closer to MBT timing without getting into knock at high load."
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 0
And well, I just noticed that there is no such table on the Vette. What a blessing, as Evap/Impact factor is some serious theoretical voodoo. Evap "The fraction of fuel that will evaporate from the port walls"; impact is fraction that will impact the port walls - it has to do will injectors compensating for such events.. I had to deal with this when nailing down a _slight_ lift-off rich, lean-in lean condition.. Like I said, minutia.. tail-chasing minutia.
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 0
Ah, for me, that's like throwing out a puzzle piece because I can't find where it fits.. Clearly it must be of some use? I hear you though.. While we're on the topic of timing.. What are you guys doing with the IAT based modifiers, most GM tunes are so quick to pull timing and this tune is no exception.. Pretty funny how many damn multipliers this one has too.. 4 of them, one based on alco %. I digress, where do you start pulling timing.. 95+ 104+?
Race Director
Joined: Jul 2007
Posts: 10,961
Likes: 2,643
From: Texas Hill Country
Ah, for me, that's like throwing out a puzzle piece because I can't find where it fits.. Clearly it must be of some use? I hear you though.. While we're on the topic of timing.. What are you guys doing with the IAT based modifiers, most GM tunes are so quick to pull timing and this tune is no exception.. Pretty funny how many damn multipliers this one has too.. 4 of them, one based on alco %. I digress, where do you start pulling timing.. 95+ 104+?
mbt is the same, technically, which is what you want in your base table, but you can't hit mbt on pump gas anyways.
I pull iat at 122 on an na car but I make sure the base table is where it needs to be.
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Race Director
Joined: Jul 2007
Posts: 10,961
Likes: 2,643
From: Texas Hill Country
Yes, and often times there is no logic to any #s that may be a bit.. umm fudged.. It's hard to reverse-engineer something flawed.. I only call fudgery at the rather complex-for-the-sake-of-complexity stuff, the minutia like transient fueling - that is a damn mind bender and may come into play if anyone running e85 upgrades their injectors - though really, it should come into play when running different fuel to start with..
And well, I just noticed that there is no such table on the Vette. What a blessing, as Evap/Impact factor is some serious theoretical voodoo. Evap "The fraction of fuel that will evaporate from the port walls"; impact is fraction that will impact the port walls - it has to do will injectors compensating for such events.. I had to deal with this when nailing down a _slight_ lift-off rich, lean-in lean condition.. Like I said, minutia.. tail-chasing minutia.
And well, I just noticed that there is no such table on the Vette. What a blessing, as Evap/Impact factor is some serious theoretical voodoo. Evap "The fraction of fuel that will evaporate from the port walls"; impact is fraction that will impact the port walls - it has to do will injectors compensating for such events.. I had to deal with this when nailing down a _slight_ lift-off rich, lean-in lean condition.. Like I said, minutia.. tail-chasing minutia.
Heel & Toe
Joined: May 2007
Posts: 18
Likes: 0
Derp.. Sometimes I forget about this fancy Vette. Since it's untuned, I had my mind on my TBSS (418ci, Turbo, plenty of things to have mind on). Thanks for the tip on the IAT.. that is where I started with my TBSS when it was NA; ah memories.
