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DOG
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626 Posts
Discussion Starter #1
http://www.tiggerfan.net/gto/gtopulls.jpg

That is my run (Second run #'s are 303/320 - sorry they are hard to read)

Only difference between red and blue is 4000 miles, tuning and spark plugs.

I forgot to print it with the blue torque curve, but its flatter then a 10 year old school girl. They are shown in speed because when I printed them out today I forgot to change it back from dbluegoat's settings (see below). Not only are the peak #'s better, but across the board the gain is dramatic.

You can see the torque curve here - http://www.tiggerfan.net/gto/gtorun3.jpg

Its absolutely amazing.

And now for the fun stuff.

http://www.tiggerfan.net/gto/jason.jpg

They are done in MPH because his plug wires didn't like the dyno very much.

Red line is predator, and you can see down low it was better. Blue line is stock, which had better high end performance and peak performance.

The green line is after a custom tune. Ignore the 364 torque # caused by a torque spike, and yeah the green torque curve is hard to read.
 

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Knight Errant
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1,800 Posts
tiggerfan said:
http://www.tiggerfan.net/gto/gtopulls.jpg

That is my run (Second run #'s are 303/320 - sorry they are hard to read)

Only difference between red and blue is 4000 miles, tuning and spark plugs.

I forgot to print it with the blue torque curve, but its flatter then a 10 year old school girl. They are shown in speed because when I printed them out today I forgot to change it back from dbluegoat's settings (see below). Not only are the peak #'s better, but across the board the gain is dramatic.

You can see the torque curve here - http://www.tiggerfan.net/gto/gtorun3.jpg

Its absolutely amazing.

And now for the fun stuff.

http://www.tiggerfan.net/gto/jason.jpg

They are done in MPH because his plug wires didn't like the dyno very much.

Red line is predator, and you can see down low it was better. Blue line is stock, which had better high end performance and peak performance.

The green line is after a custom tune. Ignore the 364 torque # caused by a torque spike, and yeah the green torque curve is hard to read.
Is the green trace (hard to follow for me) A/F ratio always under 13, and actually closer to 12.0 to 1 at the upper end of the scale above 98 or so MPH on Jason's run? It looks lower than your #3 pull, but about even with your #2 pull.
 

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DOG
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626 Posts
Discussion Starter #3
Yes, the car was getting better power on the rich side of things. Mine however is getting better power around 13:1.
 

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Knight Errant
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1,800 Posts
tiggerfan said:
Yes, the car was getting better power on the rich side of things. Mine however is getting better power around 13:1.
Thanks for the answer. These are definitely not engines to run lean for power (or at least, not for long) unless they have a lean cruise feature like some of the later F-bodies. This confirms it IMHO. So, where do you feel the Predator is weak, AFR or timing for top end?
 

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Knight Errant
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1,800 Posts
tiggerfan said:
Yes, the car was getting better power on the rich side of things. Mine however is getting better power around 13:1.
Shame the printout overan the numbers. The final tune (green) shows 15 more HP, but the Predator (red) 59 ftlbs. more torque? Can that be right? I wish I could read the stock peak numbers up top (blue). Wow, these traces are hard to read..for me anyway.
 

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DOG
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626 Posts
Discussion Starter #6
I don't know why the predator is weak. Its obvious that they made no changes to the stock PE table, which is broken, and I think was exacerbated at the higher end by the SLP MAF on the car. Without seeing the actual tables, my best guess is that the top end timing is either pushed too far and its getting knock retard, or its not pushed hard enough. I didn't poke around at all in the predator software. At the same point, I know ALL the predator A4 people are very happy with the tranny changes. I don't want to really guess, because I don't know what changes the predator makes to timing and what not, and dbluegoat didn't have the stock maf or intake, and that could affect things as well.
 

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DOG
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626 Posts
Discussion Starter #7
Old Goat said:
Shame the printout overan the numbers. The final tune (green) shows 15 more HP, but the Predator (red) 59 ftlbs. more torque? Can that be right? I wish I could read the stock peak numbers up top (blue). Wow, these traces are hard to read..for me anyway.
Its a torque spike down low. It isn't that there is that much torque, its that the dyno hiccuped (probably when the convertor locked up)

Sorry the traces are hard to read, not much I can do. but the numbers are entirely my fault. Sorry on that. I'll try and stop by tomorrow and get better printouts.
 

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Knight Errant
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1,800 Posts
tiggerfan said:
Its a torque spike down low. It isn't that there is that much torque, its that the dyno hiccuped (probably when the convertor locked up)

Sorry the traces are hard to read, not much I can do. but the numbers are entirely my fault. Sorry on that. I'll try and stop by tomorrow and get better printouts.
Please don't kill yourself on my account. I was hoping to see why an otherwise hard running generic tuned car literally fell on it's face and lost nearly .6 seconds in the last half, 660 feet, of the quarter mile compared to a stock tune. I can squint and guesstimate some difference, but not the glaring one I was hoping for. Thanks for posting. The darkness of the tracings are certainly nothing you control. We're good. :cool:
 

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DOG
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626 Posts
Discussion Starter #9
The stock air to fuel ratio on this car is a mess. In PE mode, I haven't seen one that is close to consistent across the entire spectrum. It would be one thing if the car was 14:1 or 11:1 all the way across, but if you look at both my dyno and jason's you can see the differences in the fuel ratios, and it just isn't good. The timing tables are right on the edge at peak torque, which is good, but there is a LOT of play above and below it to get even more power (which is why my curve is nearly flat, which is ideal, at least with a normally aspirated engine - it means it is performing as good at 2000 rpm as it is at 4000 rpm).
 

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Knight Errant
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1,800 Posts
tiggerfan said:
The stock air to fuel ratio on this car is a mess. In PE mode, I haven't seen one that is close to consistent across the entire spectrum. It would be one thing if the car was 14:1 or 11:1 all the way across, but if you look at both my dyno and jason's you can see the differences in the fuel ratios, and it just isn't good. The timing tables are right on the edge at peak torque, which is good, but there is a LOT of play above and below it to get even more power (which is why my curve is nearly flat, which is ideal, at least with a normally aspirated engine - it means it is performing as good at 2000 rpm as it is at 4000 rpm).
Agreed. Stoichiometric (spelling?) AFR for current gasoline is around 14.7 or so to 1. All of these cars seem, from all the dyno sheets seen so far, to run below this, richer. Conventional wisdom states that to err on this side results in wasted gasoline and off-peak performance. To err on the other side overheats engine components directly related to compression and the combustion process and burns things. This can happen when you give the car an uncompensated dry shot in seconds, To have a really jagged map below 13:1 may be simply be compromise for all conditions or a safety margin, but certainly doesn't help the car meet EPA standards or make full power. Not to suggest a product, just the companion explanation, see:

http://www.racetep.com/halmeter.html
 

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So 15 hp is what I got with a tune. It seems to be the norm if you haven't changed the MAF. The air/fuel mix for my car wasn't nearly as flat as yours. see here I wonder if there is a component that could be replaced that might change this.
 

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DOG
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626 Posts
Discussion Starter #12
Its tweaking in the PE table. The guy who did your tune should be able to take care of that. There really isn't a component per se that would change that.
 

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Knight Errant
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Just my humble thoughts on precision tuning

What I have been able to find to read (was up WAY late last night) indicates that the best power is made at about 13.7 to 1 AFR and best economy at about 15.3 AFR. It is the opposite of what you would logically expect. It might even dip a tad lower on AFR for this engine given aluminum's 'quench' tendencies over cast iron. Accepting and speculating, that also explains somewhat how we get back to a 10.9 to 1 CR on the LS2 with 93 octane MON/RON gasoline. I know there are Pro Stockers out there using aftermarket or Motorsports computers that could turn off the key after they launch and still finish the quarter on pre-detonation. The power is right on the edge for us, as always, standard doctrine, but not something I'd be comfortable with as a constant state. We all know what happened to the Chrysler 'Lean Burn' engines of the 70's, burnt pistons and toasted valves. The 05 Powertrian module is reputed to have doubled the onboard memory capacity. Let's hope they incorporated two more higher refined and tweaked fuel and spark maps, part throttle and WOT. Time will tell, and if so, I wonder about backwards compatibility.... :sneaky:
 

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DOG
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626 Posts
Discussion Starter #14
Best power I've found fluctuates between 12 and 13.5 or so. It REALLY depends on the car and I haven't figured out exactly why. I've tried my power all over the place, and best power is right at 13:1. I've seen other NA cars that like it as rich as 11:1. 15.3:1 might give best economy, but the fuel ALSO plays a critical part in cooling the internals of the engine (Its actually quite amazing the difference some fuel can make in temperatures). Best power theoretically will be made at the point where Exhaust Gas temperature is maximum, and best economy is the point at which the engine will run satisfactorily on the least amount of fuel, but neither is ideal. Erring on the rich side of things will keep your internals cooler, which keeps detonation down and improves engine life, at the cost of MPGs and a tad of power.

Remember too that the only place we have this control is in PE mode, since the O2 sensors will keep everything at 14.7 that the cats like in closed loop mode.
 

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Knight Errant
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tiggerfan said:
Best power I've found fluctuates between 12 and 13.5 or so. It REALLY depends on the car and I haven't figured out exactly why. I've tried my power all over the place, and best power is right at 13:1. I've seen other NA cars that like it as rich as 11:1. 15.3:1 might give best economy, but the fuel ALSO plays a critical part in cooling the internals of the engine (Its actually quite amazing the difference some fuel can make in temperatures). Best power theoretically will be made at the point where Exhaust Gas temperature is maximum, and best economy is the point at which the engine will run satisfactorily on the least amount of fuel, but neither is ideal. Erring on the rich side of things will keep your internals cooler, which keeps detonation down and improves engine life, at the cost of MPGs and a tad of power.

Remember too that the only place we have this control is in PE mode, since the O2 sensors will keep everything at 14.7 that the cats like in closed loop mode.
I can see how that could be, aluminum heads and block should allow a deeper dip below 13.7. Most of the stuff I found was a bit dated and I think analyzed and results arrived at based on cast iron, and the math for doing a recomputation for specific materials was a tad steep, so I let that slide. Agreed on the cooling, a 15.3 AFR would be better for economy and cooling, but the emissions dictates a backup to 14.7. The aluminum helps here too in one respect, shedding heat faster, so the lean 'tilt' heat of non-stoichiometric cruise has less of an impact on wear and tear. Shame we can't play with the 'other' mapping.... :sneaky: All in all, an impressive job designing and implementing this engine by GM, but not so perfect it can't be tweaked... :D
 

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tiggerfan said:
...fuel ALSO plays a critical part in cooling the internals of the engine (Its actually quite amazing the difference some fuel can make in temperatures).....
Am I dreaming or did I once see a drag car that had the small fuel tank and/or coiled fuel line packed in ice? Do they still do that??
 
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