Issues and thoughts after a long night on the dyno

[doc350]

So I just spent the last 6 hours on the dyno with a Procharged Z51 Automatic w/ a flex fuel kit. I ran into some issues, and I wanted to get some thoughts and questions down on "paper" so to speak before I crash for the night.

-First off, the 91oct tune went pretty smoothly. There is still more for me to learn as far as SOI and Driver Demand goes (more on that in a bit), but in the end, the car made ~570whp @ 7psi. with what I feel is a conservative tune up.

-When we filled the tank with the e85, things got funky. I have some several Gen IV flex fuel setups, so I know my way around those particular settings. This is the first Gen V car I have done it on, and apparently it's not quite the same.

-With e85 at roughly 4200rpms, there would be a large dip in the power curve. Like almost 80whp, and the car would never really recover. You could feel it during the pull. It was almost instantaneous, like a hiccup. The only place it showed up was the dyno though. Nothing in the logs had any sort of dip in them. I started logging everything I could think of to try and track it down, but no joy.

-So I start looking though the file for things that are related to Alcohol % that could be causing the dip. I find a few things here and there, but nothing that jumps out at me, and sure enough, none of them made a difference.

-My first thought was Driver Demand. I was not seeing any reduction of TPS % or Delivered Engine Torque, but I thought I was worth a try. I raised the DD tables (that worked perfectly well on 91oct keep in mind) quite a bit with no change. Question: Do the DD tables take fuel flow into account? By that I mean, does the extra volume of fuel that e85 requires cause those tables grief?

-In the same section of the tune, there are other tables under the heading Torque Coefficients. I have never heard those discussed. What do they do and how do they effect the DD tables? I noticed that there are some with e85 labels, and that got my mind turning.

-Next thought was SOI. To be honest, there has not really been any science behind what I have done to these tables. I need to get a real version of Excel and look at Dave's spreadsheet, and really start tuning this table rather than the shotgun approach. Another question: With the added volume of fuel when using e85, would you need to start the injection a lot earlier to allow time for the fuel to get into the cylinder? My lambda reading never fluctuated during any of this by the way.

-When logging SOI, what are you logging? What does "Primary SOI" actually tell me? Is it what the engine is doing, or what it wants to do? If those numbers are larger than what is in my SOI Base table, is that an indicator that I need to raise those values?

-Another logging question, this time about DD. Delivered Torque, Engine Torque, Trans Engine Torque. What do these mean? Kind of the same question as above. What exactly are these telling me? How do they pertain to the DD tables? Or do they at all?

-Calculated Load and Absolute Load. I think this is where my issue lies, I'm just not sure how to go about fixing it. If my Absolute Load value during a pull is above 100%, does that mean I am not getting all the torque available to me? I did notice that after raising the DD tables by quite a bit, this value didn't really change.

I think that's it. Maybe. For now. Sorry if I rambled, but I needed to get some things out of my brain before I tried to sleep. If any of you have thoughts or experiences similar, please share. Also, feel free to add questions of your own. The more discussion the better in my opinion.

I don't have the tune or logs on this computer. I will try to remember to post them up in the morning after my laptop recharges.

[Higgs Boson]

I'll post some configs I made for E92 when I get home this evening.

Might be good if you post your tune.

[2xLS1]

Curious what you charge for 6 hours of your time on a dyno. What are customers willing to pay for a tuners time these days, plus the dyno time charge plus licensing the vehicle. And it sounds like you still need to spend more time on it.

[yonson]

Curious what you charge for 6 hours of your time on a dyno. What are customers willing to pay for a tuners time these days, plus the dyno time charge plus licensing the vehicle. And it sounds like you still need to spend more time on it.

I know when I was working in a shop and if something new/interesting like this came in I would just charge for a normal dyno tune and write off the rest as "on the job training" I of course would tell the customer this up front so they understood that it wouldn't be a normal calibration and would take some extra time at no charge to them, this way both you and your customer end up with the best possible result and you know how to do it correctly on the next vehicle you do. If you don't know how to do something 100% you shouldn't be charging your customer to learn how unless you have told them that up from and they are ok with it (I would never do this unless the customer insisted and absolutely understood how long/much it could be).