xssive

iTrader: (123)

This isn't on a stock pcm, but an aftermarket mefi4 based system. Its an MSD mefi4 system for an ls2. They use the UMI/Arizona Speed InGenius tuning software, but there isnt a table for changing injector flow rates. They are telling me it all handled through pulsewidth modification.


So, does that sound reasonable? Im guessing just decreasing the pulsewidth with increased injector sizing using a wideband to tune in the afr?

RZRSEDGE

iTrader: (21)

Sounds like a major PIA!

slow

iTrader: (7)

sounds like older jtec based dodge vehicles, the fuel table is pulsewidth based on map and rpm.

Ryan

xssive

iTrader: (123)

Yeah its totally pulsewidth based on map / rpm like you said. It's afr controlled closed loop tuning once you dial in the fuel tables to around 5% of your target. It idles around 4 cells in the table which you can inc/dec in real time with a single click. Pretty cool actually

gametech

iTrader: (1)

That is VERY common with aftermarket ECUs. Why should they bother incorporating VE and IFR into the calculations when that processing power could do something else? Basically everything that a stock computer does to calculate pulsewidth is unnecessary if you just start with PW. It can be a bit more challenging to build an initial table, however, unless the tuning software provides some base calculator functions to help.

2002_Z28_Six_Speed

iTrader: (19)

So true! Sounds like you could use a spreadsheet to get the inital PW table.

I was thinking about it and it almost seems like you could bypass alot of things like experimentally finding the true IFR, small pulse adjust, and all that jazz.

BUT. This setup would make it tons of work if you changed the injectors. You would have to do it all over again!

gametech

iTrader: (1)

Actually, when changing injectors you apply the appropriate percentage change to the entire PW table to get you pretty close. Then you are left with all of the usual minor tweaks to accomodate the REAL differences in IFR.

2002_Z28_Six_Speed

iTrader: (19)

That makes a lot of sense. Thank you!