Kevin Doe

iTrader: (1)

I am completely done with the VE table for the time being. I have every possible cell within 1% and now I'm moving onto really making some power from the tune.

I want to change my PE modifier based on RPM ( B3618 ), but I want to do so in an intelligent manner.

Theory tells me that you make max torque under the curve when you make the car richest at max torque, then lean it out afterwards.

I was thinking in the 12.75:1 range before max torque, then ramp to 12.5 at max torque, then ramp back to 13:1 after peak torque. Does anyone have any thoughts on this subject. I searched and didn't find much on the subject. Joecar had one post where he posted a screenshot of his curve, and it looked like a nice curve, maybe a bit on the rich side.

Anyone care to post your PE modifier based on RPM ( B3618 ) tables for comparison/ideas.

Thanks,
Kevin

Frost

iTrader: (45)

in many cases a near guess is 12.9-13.1 down low moving to about 12.8 around peak torque and anywhere from 12.8-13.1to2 up top. Time for the dyno.

Kevin Doe

iTrader: (1)

Could you post up a screen shot of the curve? I'm curious what works better. A linear ramp to peak torque then back down, or more of a hump that follows the torque curve? Yeah, dyno will be the deciding factor, but I'd like to get close before I get on the dyno and spend a ton of cash. On the street I'll be able to look at elapsed times. Say start a WOT pull in 3rd gear at 1500 rpms, and watch the elapsed time. I could look at elapsed times through each thousand rpms, and compare back to back runs to look for improvements.

brokenfly

here's a log of a motor pass showing commanded afr vs actual thru out the run...

olsd tune on 2004 gto ls1...

Kevin Doe

iTrader: (1)

That basically shows me that over 2000 rpms you're commanding 12.88 AFR. Not really the information I was looking for. Is this what you found to make max torque?

brokenfly

not sure where my peak torque really is since all i got is timeslips and no dyno time at all...

i found the closer i get the car to running like frost said(lean low then fatter in the middle and thin up top) yielded the best e.t.'s for me...

the flat commanded PE afr helps me see where the afr moves easier on it's own...
that run showed me i needed to thin it out a lot below 4600...

all this track and street tuning could be wrapped up in a hurry on a dyno...

radkon

iTrader: (2)

Here is a shot of my PE table:

Yellow is stock (04 GTO)

Blue is commanded and Red is actual

YellowToy/A

iTrader: (1)

I keep the A/F below 12.8 at peak Housepower. 13 may get best HP but not more than 5 or 10 at the most and more like 3 or 4. Lean is hot and detanation is not good. I like safe more that max HP.

Frost

iTrader: (45)

in most NA cases, 13 is fine, wouldn't call it lean or "dangerous"... some cars LIKE 13.2-13.3...

edcmat-l1

iTrader: (10)

Anything numerically below 14.7:1, when discussing gasoline, is considered rich. Anything numerically above, is lean.
Most engines will continue to make power up until the point of fuel deprivation. Its not uncommon for an engine to make more power at 14:1 than 13:1. The trade off being combustion temp. With stock, hypereutectic pistons, its pretty dangerous getting em that lean in search of power. With forged, its much more safe. As for tq, and being richer at peak torque, it doesnt make anymore power, rather, prevents detonation under the high load.
PS. As far as how to set it, and tune it, RADKON has it right. You want to set your PE table to whatever A/F you want vs RPM, and then tune to it.

Kevin Doe

iTrader: (1)

Here is my current PE vs RPM table. Tell me your thoughts. My actual AFR is within 1% of this command. No KR, seems to run very strong, and very good. I'm still tweaking, and will probalby lean it out more, but this is my current table.

For reference, MS4 Cam, 1 7/8" long tubes, 3" true duals w/ X-pipe, LS6 intake, dual 3.5" intake pipes, NO MAF, open-loop speed density tune.



POST UP SCREEN shots and comments regarding to how well it is working, and your observatoins please.

Steve Bryant

iTrader: (1)

Kevin,
This all looks pretty reasonable. I think that it is more valuable to monitor and tune for AFR versus MAP, regardless of RPM.

You probably are a bit rich for normally aspirated. I'd shoot foraround 13.0:1. But play around with the AFR at WOT to see what works best for your vehicle.

Steve

edcmat-l1

iTrader: (10)

I dont think you're commanding rich enough in the 2000 rpm and up region. And then I think you're commanding too rich at the richest point.
I usually just set em to about 12.7 up to around 4000, then step it up to 12.9.

YellowToy/A

iTrader: (1)

EDCMAT had the best info here

"The trade off being combustion temp. With stock, hypereutectic pistons, its pretty dangerous getting em that lean in search of power. " I think below 12.8 is good. If you want to take the risk for a few more HP have fun.

2002_Z28_Six_Speed

iTrader: (19)

Isn't it mainly due to it being cast and not hypereutectic?
Hypereutectic resists heat better but forged is stronger.
Just asking.

edcmat-l1

iTrader: (10)

Hypereutectics absolutely do not resist heat better.
PS, As far as I know, everything is hypereutectic now, as far as pistons. Has been for a while. Hypereutectic is nothing more than high silicon cast.

Frost

iTrader: (45)

Each car is different though... I have tuned quite a few that only pick up 3-4 going from a rich 12.4 all the way 13.0. If it isn't hurting the tq curve, the fuel stays in. Maybe not all the way down to 12.4 but it won't be staying at 13 for such a small gain. The reverse side is, lots of cars will pick up 10-15 HP moving from that rich to the high 12s.

2002_Z28_Six_Speed

iTrader: (19)

You are right. Due to emissions and tigher tolerances. Much cheaper than forged for sure.

I thought they might be more resistant to heat because silica is basically sand and therefore has a higher melting point than AL.

gametech

iTrader: (1)

To the OP. Once you have modified everything as close as you have reported, there is NO reason whatsoever to rely on anyone else's tune.