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Discussion Starter · #1 ·
I started doing a little WOT tuning tonight while going through bluegoats sticky and it calls for a commanded 12.5 AFR across the board under WOT. I know every car is different, but I'm wondering if this is just for safety? Everywhere else I'm reading 12.8-13.1 for an ideal ratio in an NA car.

I set lambda to 1.176 across the entire WOT range (12.5 AFR) and after a log I'm seeing right about 12.5 at the low end up to right around 13 at redline. Should I adjust the MAF frequencies to correct it or should I just leave it?

I've attached a log (and config) if anyone wants to take a look. This was a street pull with IATs around 72. I'm seeing small fractions of knock up top, but its less than 1 degree. I'm also wondering if I should richen it up so I can add more timing or where the tradeoff is between fueling and timing. The timing is stock right now.
 

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That's probably a bit conservative. I tuned my last car to 13.0 and it was fine. Will probably tune this one 12.8 - 13.0 as soon as I get my WB hooked up. Depending on how my dyno time works out I might try playing with it a little bit, or at the track....
 

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You will make a lot more torque and hp by running more fuel and more timing. The car should take 24 degrees all day long at WOT if you set the PE table to 1.20 (12.25:1) AFTER you have tuned the trims perfect via the MAF table. I assume that you have completely disabled dynamic airflow already and set the PE Delay to 0 and enrichment rate to 1.0
 

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Discussion Starter · #4 ·
I'm not in front of it, but I think it's 20 degrees right now; whatever stock is. Dynamic airflow is disabled, but I'm not sure about the other two. I just followed blue goats sticky for part throttle and WOT trimming. According to his post, he has the PE enrichment set first and then trimming.. Which worked fine for me tuning on premium, but on E85 I can't get the trims to line up, so maybe that's why.

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If you did everything right, your fuel trims in close loop, and your WOT fueling with WB, all you need to do is change the afr cell in the cal to run E85. problem with E85 is that stoich for this gas is not exactly 9.76, in theory that's the stoich, in reality, alchohol content varies a lot from gas stations/seasons, so you'll have to find what the real stoich is.

Some people use an alcohol content tester, others including me do use fuel trim error to find the theoretical alcohol content. (first option is more accurate, 2nd option you have to make sure your tune is right on the spot). For the gas stations i've used here in Southern Cali, E85 stoich is 10.6499, shoot for .82 lambda WOT. There is no need to touch your MAF once it has been tuned (spot on) for e10 or e0.

And yes, 12.8-13.0afr is an old number that came up long time ago, back in the LT1 era more likely, when most of the tuning was done from devices measuring fuel as far back as possible from where measurement should be taken on. Lol, all i'm going to say, test, test and keep testing until the car doesn't respond any better. L76's respond a lot better to .82-.84 lambda compared to the 13.0afr internet story. :eek:ldfogey:

Have fun.
 

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Discussion Starter · #6 ·
If you did everything right, your fuel trims in close loop, and your WOT fueling with WB, all you need to do is change the afr cell in the cal to run E85. problem with E85 is that stoich for this gas is not exactly 9.76, in theory that's the stoich, in reality, alchohol content varies a lot from gas stations/seasons, so you'll have to find what the real stoich is.

Some people use an alcohol content tester, others including me do use fuel trim error to find the theoretical alcohol content. (first option is more accurate, 2nd option you have to make sure your tune is right on the spot). For the gas stations i've used here in Southern Cali, E85 stoich is 10.6499, shoot for .82 lambda WOT. There is no need to touch your MAF once it has been tuned (spot on) for e10 or e0.

And yes, 12.8-13.0afr is an old number that came up long time ago, back in the LT1 era more likely, when most of the tuning was done from devices measuring fuel as far back as possible from where measurement should be taken on. Lol, all i'm going to say, test, test and keep testing until the car doesn't respond any better. L76's respond a lot better to .82-.84 lambda compared to the 13.0afr internet story. :eek:ldfogey:

Have fun.
Thanks for chiming in :)

The closed loop trimming is almost spot on with E10. I see 14.6-14.8 all day at part throttle. There's little more variation at idle, 14.4-15.0 but I'm not concerned with it since the car has a full exhaust.

I actually downloaded one of your base tunes with an 8.9 E85 stoich. I noticed you only entered that in the 0% tps cell and left the rest stock; is it supposed to be left that way? I used that value in mine at 0% only and was seeing -7 on my stft's at idle, so I rescaled the MAF. It sounds like i should just lean out that 8.9 AFR value and revert back to my known good MAF scaling.

My WOT trims haven't been corrected since the original log. That's the factory scaling above 7200hz. I didn't think 13.0:1 was bad, so I just left it.

If I do decide to re-trim idle and part throttle with E85, should I use the stft's or the WB? It's a little unclear whether the narrowband o2s can detect e85 properly. I wasn't sure if they read AFR or lambda.

And as far as content... We have E85 all over the place here in southeast Michigan. I went to two gas stations and both employees were clueless to the content. I may just use the error% as well instead of popping the hood and hitting the Schrader at every tank.

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NB's read lambda, you don't need to retrim using MAF
(again, assuming your tune is spot on), only change the first cell in the afr, and adjust afr as needed. Start at 10.64 afr in the first cell (no need to do anything with the other cells) and adjust from there, or get a tester to confirm alcohol content. if you have to retrim is because the MAF wasn't tuned properly, think about it, there is no airflow changing that would modify volumetric efficiency, the change is due to gas stoich ratio.

You can read more about our E85 tests here. Changes needed, afr cell and cranking fuel. you would find by how much, although i was never able to test in temps below 40F, but should work as advertised :)
http://www.g8board.com/forums/showthread.php?t=42626&highlight=e85

Have fun.
 

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Discussion Starter · #8 ·
I figured the NBs had to read lambda since I was still seeing STFT changes with the stoich adjustments. I did about 5 scans and tweaked each one; looks just about right now. I'm seeing -1 to 1 across the MAF ranges @ 10.25 stoich and LTFTs disabled. This was with HPT measuring 0.75 gallons of E10 left in the tank and then adding 10 gallons of E85. I'll run this tank near empty again and top it off with E85 again and recheck. I've also added your timing tables and no KR at this point :)

Thanks for the help!

Oh and PE delay was zero and enrichment was set at 1.
 

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:thumbsup:
 

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Discussion Starter · #10 ·
I went to the track last night and ran a new PB on E85: 12.9 @ 109mph! I actually would've gone a hair faster, but I hit the limiter in 3rd gear. My log shows me hitting 109, backing down to 106, then back up again. I adjusted it, but the track was closing :(

My last PB was 13.3 @ 106, but that was also before I had LTs, axlebacks, HPTuners, drag radials and was running E10 at the time lol. It was extremely muggy though; my friends supercharged Silverado SS ran one full second slower than he did in the fall last year. I'm confident she'll be even faster on a cool night with things as is.

I have a question for you BlueGoat.. I made 6 passes and after each pass I had zero KR; not a speck on the radar. So, I kept adding more timing after each run. In the end, my log shows me at 30 degrees at 6000 RPM and peaking at the 6400 rpm cell with 32 degrees (2 cell counts). I'll have to look back and check, but I think that's either 9 or 10 degrees total added. I was trying to get as many runs in as I could, so I just added timing via the IAT table. I've attached a log of that run if you don't mind taking a look at it if you get a chance. My AFR gets a little lean up top and I forgot to log my IDC to see if I was maxing out. It just seems like a whole lot of timing without any knock, but the car kept getting a little bit faster on each pass.
 

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My guess is that you're using the factory timing and adjusting timing via PE/COT Spark?. You can use 2-3* more from 4400-5600rpm from .76g/cyl and above, don't go higher than 30* up top, she won't accelerate more, and i think you were testing, but don't add timing with the IAT adjustment, she'll lean out, plus you want to take timing out when IAT is climbing, not to add more timing here , E85 would make her more KR resistant, but once the engine has reached max peak pressure in the chambers, more timing won't have any more effect in power. 30* is a lot for 6000rpm when you make the same power at 22-25* depending on gas (91-93 octane). where it would make most of the difference is in the middle of the powerband, 4200-5600rpm, with 91 octane, we're really pressed with KR in this area and more than 20-21* timing.

Have fun.
 

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Discussion Starter · #12 ·
Now that I've looked at the PE/COT table, it does make more sense to add/subtract that way; a little easier too. I was just following the cells that had hits in my log, so I added via the IAT table based on what the current IATs were at the time then added to those cells. I was seeing a little KR from .52-.60 g/cyl, so I removed some there and just kept adding from .64 and above. I see 30* at 6000 rpm and 22-25* at 4200-5600. Maybe I'll back off the timing a hair on the top end and add a little more in the midrange. I know it's not ideal without having a dyno and actually seeing the power rise or fall. If we were to assume there would still be zero KR, would you say that 30* would be a max for midrange rpm as well? Thanks for your input!
 

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I agree with bluegoat06. 30* is a thing of the past. No need to get very aggressive with the new gen 4 motors. I run 21-22* in my gxp with a gas afr of 12.5, and runs great that way.
 

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Discussion Starter · #14 ·
I agree with bluegoat06. 30* is a thing of the past. No need to get very aggressive with the new gen 4 motors. I run 21-22* in my gxp with a gas afr of 12.5, and runs great that way.
Are you making max power at that timing though, or is that the limit before you start to see knock?
 

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I see a blip of knock at 24-25*. Our 91 octane in AZ is really bad. Especially with our temps
 

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Now that I've looked at the PE/COT table, it does make more sense to add/subtract that way; a little easier too. I was just following the cells that had hits in my log, so I added via the IAT table based on what the current IATs were at the time then added to those cells. I was seeing a little KR from .52-.60 g/cyl, so I removed some there and just kept adding from .64 and above. I see 30* at 6000 rpm and 22-25* at 4200-5600. Maybe I'll back off the timing a hair on the top end and add a little more in the midrange. I know it's not ideal without having a dyno and actually seeing the power rise or fall. If we were to assume there would still be zero KR, would you say that 30* would be a max for midrange rpm as well? Thanks for your input!
No, don't run 30* in those areas at WOT loads, it'll be too much timing, even with e85, all is needed is 3-4* more than optimal timing for 93 octane for example. If your engine was FI'd where timing has to drop a lot, the same 2-3* would make a huge difference, in N/A form, not so much as once the engine has reached max pressure in the combustion chamber, there would be no point on adding more spark, she would simply make no more power, even if you don't see KR in the logs. 2-3* in those areas would put you around 25-28*, (assuming the engine is not heatsoaked).
 
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