Project Turbo Deathkart

[steveo]

Doesn't tricking the ECU into running in a different portion of all MAP values in speed density require halving the injector value as well? I know the tune I'm using as a reference as 15 lb injectors as a constant and he was running 30lb if I remember correctly.

no it doesn't. the only reason you might decrease the injector constant is if you run speed density and exceed 100% VE which i guess is unavoidable with a turbo, however halving it (so 100% VE is actually 200% VE) might be a bit extreme. it would require scaling the entire VE table by the same amount. if you were running a maf there should be no need to do that. every single other thing in your calibration will get screwed up too.

One other curiosity for now: Is the primary controlling factor for closed loop fueling on a MAF system the MAF frequency calibration? I see stoich inputs (which I presume it uses as a target?) and a lot of other inputs for open loop/PE/etc

maf calibration tables and ve tables have really nothing to do with open loop and closed loop fueling methods. in a maf system the maf table is how it estimates airflow. in a speed density system the VE table is how it estimates airflow. that's a primary factor in how much fuel it injects for sure, but it has the same effect whether you're in open loop, closed loop, power enrichment, or whatever.

[etravoda]

no it doesn't. the only reason you might decrease the injector constant is if you run speed density and exceed 100% VE which i guess is unavoidable with a turbo, however halving it (so 100% VE is actually 200% VE) might be a bit extreme. it would require scaling the entire VE table by the same amount. if you were running a maf there should be no need to do that. every single other thing in your calibration will get screwed up too.

maf calibration tables and ve tables have really nothing to do with open loop and closed loop fueling methods. in a maf system the maf table is how it estimates airflow. in a speed density system the VE table is how it estimates airflow. that's a primary factor in how much fuel it injects for sure, but it has the same effect whether you're in open loop, closed loop, power enrichment, or whatever.

I'm probably not articulating myself quite well enough but I think you understood (and now that I've made sense in my own mind). Yes by going to the 2-bar MAP I'll need to scale the VE values lower in order to not exceed 100% under the boost portion of the map.

Just trying to wrap my head around tuning (for both speed density and MAF-based tunes in general).

Also just realized you're THE EEHack guy! Thank you for all your work on the flashing/data software, its incredibly well put together! I'm sure it's a huge effort for you and amazing you've provided it all for free.

[steveo]

with all the work you're putting into this toy, have you considered just changing the damn pistons? you could lower your static compression and increase your ability to handle some minor detonation really easily at the same time. i don't understand why you would do all this work with the stock pistons and CR as changing pistons on a SBC is just as easy as swapping the cam, which you already did. you could just quickly ball hone it and skip the machine shop too if you really wanted to save some money and it would probably be fine. might only take an afternoon and a couple hundred bucks to reach your boost goals on pump gas. i don't think there is a way you're going to get 8psi or higher reliable on that thing with pump gas and the stock compression ratio, and if you do you're going to have to retard timing so much you'll be making negative gains

[etravoda]

I flashed my initial tune and have gone for a few light drives while data logging to see how far off the closed loop VE tables are. For some reason it's running VERY lean across the whole table. Trimalyzer has been a handy tool for this! I'm still on the factory fuel system (not going into boost) and want to make sure I can get it to run well before changing another variable (understanding I will need to again go back through closed loop tuning). I've lowered the injector flowrate down to 20 lb/hr because it was so lean all the way across the map.

Is the barometric pressure reading (now at 47 kpa with the 2-bar) causing a massive compensation in leaning out the map? I'm at altitude so it might be even a little worse?

[steveo]

so you've ditched the maf?

there's no such thing as a closed loop ve table, just a ve table. it's used all the time except cranking with no maf

what method did you use when you scaled your 1 bar table into a 2 bar one? did you just copy and paste the columns or did you do some smoothing?

you could post a log but if you're sure your fuel pressure is good and it's firing on all cylinders you probably just need more damn fuel, crank 'er up!

[PJG1173]

just my $.02. not sure how this relates to the LT1 computer but when tuning $0D for boost I had to cut my injector size by almost 70% to get to where the VE table wasn't trying to go over 100 while in boost. I also zeroed any table referencing baro compensation for fuel and spark as I could not find a way to keep it from reading baro while in boost. start out very rich and conservative timing boosted engines don't like to go lean. I found with mine I couldn't run as much timing as I did NA while not in boost since the turbo acts as a ram air and increases VE. I ended up pulling almost 10 degrees in some areas due to KR. I didn't see any mention of a wideband if you don't have one I would highly recommend it especially for tuning PE. if you want to run more boost (who doesn't) and you think your engine can handle it, you should start looking at different fuel (E85) or water methanol. right now I am running E85 (actually tested as E70), 8 psi, 12* timing on a 9.73:1 compression (aftermarket hypertunetic pistons) 4.3L v6.

[steveo]

even when not "in boost" your turbo is moving and creating turbulence and altering airflow and pressure, and also heating your intake charge. none of your n/a tables will be correct.