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Discussion Starter · #1 ·
I just thought I'd share some tuning information with you folks. Hopefully, you'll find it useful. This could be long so grab some popcorn.

A few weeks ago I dynoed my car and when looking at the scans, I noticed that it would start out rich early in the pull, and slowly lean out as the RPMs climbed. In last year's setup, I would have assumed that the fuel pump and lines were straining to keep up with the demands of the motor, but this year it clearly is not the case. I have a huge Weldon fuel pump, all new wiring, and large SS braided fuel lines. That told me that I simply need to program my PCM for a little more fuel, and I wouldn't have to worry about volume, as the system can now keep up.

I decided to burn a new .bin file and have it ready, but not to load it. At least not until I had a baseline run at the track to make sure that my track readings would have agreed with my dyno findings. This is a subtle point here that many people are probably not aware of. Because of the way that our PCM does fueling during power enrichment (PE), there is a strong time component to the calculations of the commanded A/F ratio. This time component is likely to give you different results by the simple fact that a dyno pull (3rd gear) will last for about 5 seconds, while a track run will last 11-13 seconds depending on the car.

There are three PE tables in our PCMs that control the target AFR that the PCM shoots for. It is this target A/F ratio that determines just how much fuel the PCM will dole out while at WOT. (For this reason, it is very useful for people to include the commanded AFR in their log scans, as it lets you know what the PCM is "trying" to do.)

Anyway the tables are Base vs ECT, Additional vs TPS, and additional vs RPM vs time. The commanded AFR that the PCM will shoot for is the sum of the returned values from all three tables. The Base vs ECT represents a simple 2 dimensional curve that sets the AFR as a function of ECT. Basically it calls for a richer AFR when the ECT is cold, and a leaner AFT when the ECT is hot. For all practical purposes though, it is flat throughout the entire "normal" range of ECT, so in loose terms, it can be considered as a constant once the car is up to temp.

The second table, additional vs TPS also represents a 2 dimensional curve. The purpose of this table to lean out the mix slightly for low TPS positions, and leave the AFR unchanged for moderate to high TPS positions. In my stock table, this table goes to 0 for any TPS greater than 49%.

The third table and the most interesting one represents a three dimensional surface that sets the AFR depending on both RPM AND the amount of time that the vehicle has been in PE mode. In short it richens up the fuel gradually as the RPMs climb, but it also richens up the car gradually for prolonged WOT bursts as time goes on in an effort to cool things down a bit.

When I decided to make a new file, I also decided that the right fix would have been to work in the third table, additional vs RPM vs time. The base table would have been a straightforward enough fix for the leaning part, but also the wrong one. I only wanted to richen up the higher RPMs, not the entire range. The additional vs TPS table would have also been the wrong table as when racing, I have a binary throttle. It's either on or off. :D

My changes to the add vs RPM vs time table were in two dimensions. I decided that I wanted to increase the fuel a little more for RPMs past 4800, but also I wanted the additional fueling to come on sooner than the stock table called for. In essence I left the early part of the table alone, but pulled in the heavier part of the enriching by 3.2 seconds. I burned a new file and left it on my laptop's hard drive.

OK, now that we have the background out of the way, fast forward to last weekend when I took my car to th etrack. after my first full pass, I looked at the logs and saw the same trend. The fueling in the first two gears looked pretty good, but as soon as the shifted into third and the load increased, My O2's* dropped and stayed betwen 860 and 890 for the entire length of the run. I decided that the results were more or less what I expected and dropped in the new PCM file.

When I ran again, the results were right on the money. Everything looked pretty much the same in the first two gears, and once it shifted into third gear, my O2s ranged from 930 to 905. That's pretty much what I was shooting for. As a side note, the car picked up an additional .8 MPH in the back half of the 1/4 mile as opposed to the previous run.

* - I realize that using the narrowband O2 sensor for fuel tuning is questionable but until the wideband goes in (soon) with support from HP Tuners, it will have to do.

John
 

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interesting... anyway you can post some examples? :D

My problem is im going stupid rich... over 1.000 once i get to the end of 2nd gear... i gotta figure out what all to change and fix, using 42.5lb injectors...
 

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So what did you run? :D
 

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Discussion Starter · #4 ·
Steve,

You mean include the new table? Do you have HP Tuners? I'm a little apprehensive to do that as my table should not be used directly as is by somebody else. My fuel system is way different than what most people run, and the same table would give way different results in someone else's car. That's why I described what I did instead of quoting exact numbers. To get fueling dead-on it needs to be tuned to the specific car.

Do you have a log you can send me to see what's happening?

John
 

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Discussion Starter · #5 ·
Chris,

11.3/11.4, no juice. No PBs. It was a good learning day for me.

John
 

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Yeah Johns fueling system is very cool and very different than any of ours. Nice runs! Cant wait for the juice!
 

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Can we see some juice on the 23rd John? :D

I'm making the LONG ;) drive for it!! :p

Brad
 

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Just to add a little to what john stated. For guys running w/i or no i/c, the PE table add vs TPS is very handy for us. It's like adding a bigger squirter in the old carb days ;) I've had to mess with that a little on mine to help with burst KR on the street.

I'm starting to get a handle on the PE tables myself and with help from John i think we all can benefit from this. :D It doesn't matter whether you run 14.0 or 10.90, you have to tune your combo in your car. They are ALL different in some way.

Thanks John!
 

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Discussion Starter · #9 · (Edited)
Thanks Rob! That's what this site is about. Sharing tech info to help each other out.

Your comment about the add vs tps table is interesting. Did you shift your table over to the left by a few cells, or do something else?

John
 

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Hi John,
Here is a copy from my table,
1.3 1.3 1.3 1.56 1.794 1.794 1.794 1.794 1.794 1.338 0.974 0.906 0.725 0.725 0.725 0.725 0.526 0.199 0.035 0.05 0

You can see i've bumped her good and then trail it off as i reach WOT.
 

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Discussion Starter · #11 ·
Wow, you sure did bump it up. Just remember though that this table won't get looked at until you cross the threshold into PE, and I still can't see that threshold. At least with the version of sw that I'm running.

John
 

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Discussion Starter · #12 ·
Rob,

After thinking about it, I'm a little confused now. To add more fuel to eliminate burst KR, you would need to lower some of the cells, since they represent AFR. It looks like you increased the cells on the right, thereby running leaner.

John
 

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Thanks for the write up John. I was having a similer problem. O2's good in first two gears then in third the O2's drop into the .880 - .890 point. I will have to give this a try.

Greg
 

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I recently dailed in my '04 on the dyno (with WB) after installing some new injectors. I tried to dial with PE vs rpm vs time, but even minor tweaks to this table sent my A/F bouncing up and down. I ended up using the IFR to move the fuel curve around. It turned out pretty good, with a nice smooth line.

Just FYI for any 04 guys, the factory PE table is looking for mid 10's by the time you are hitting the traps. There is definitely some power in leaning it out (just don't melt your cats!).

-Geoff
 

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Guys,
I just want to thank you for sharing your experiences as I will have my DHP PowrTuner in hand this week and will start to tune and tweek. I hope to see low 13's and maybe even high 12's after a little tweek and get rid of my 077 18's:D

Thanks again!!
 

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seriesIIIChump said:
Thanks for the info WhiteHawk. Any chance you will get a track visit in with the 04? :rolleyes:
Cut it out with the eye rolling! My best time is [email protected] and best mph is 97 (on a freak tractionless pass at M9). I was playing with it yesterday, and I found out I turned off the abuse mode, but left the torque management on. Doh!

I am hoping to hit the MGM race it Mid-Michigan Dragway this Saturday. Hopefully get in the low 14's. I took 2nd place bracket racing it at the z28.com race a few weeks ago, and hope to be equally successful this weekend.

-Geoff
 

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OK no more. :rolleyes:


What was your 60'? 94.what? Is there a percentage setting you can adjust for the Torque management or is it more complicated than that?

Thanks, good luck on Saturday!
 

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seriesIIIChump said:
OK no more. :rolleyes:
What was your 60'? 94.what? Is there a percentage setting you can adjust for the Torque management or is it more complicated than that?
Thanks, good luck on Saturday!
The best was [email protected] w/2.18 60". The last pass of the day was a [email protected] w/2.22 60'. The track started getting cool. It was about 60 degrees when I ran the best time, but it dropped to about 45 when I made the last run. The last run had one degree more timing than the best. That timing makes a big difference.

Torque management reduces "calculated torque" by a given percentage during the shift. Unfortuantely, I don't know what the calculation is, so any changes to the table would just be guessing. I assume that the only thing it can reduce is timing, so that is what it lowers. It pulls 35% on the 1-2 and 40% on the 2-3 per the PCM tables.

-Geoff
 
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