Is there one number in every cell of the IFR or are they different? In other words, does your truck have a boost referenced regulator on the driver's side fuel rail?

You also need to find out what those injectors are rated at initially -- if the multec II stubbys, they are 43lb/hr at 43.5psi. The next step is to find out the rating for your truck -- I'm just not sure about the 02's, but it's probably a 4bar (58psi) setup.

 

Ok, my truck does have the vacuum referenced regulator on the driver's side fuel rail. Right now, i have different numbers in each ifr cell. I used a spreadsheet I got from a guy on ls1tech named darkblueTA. My ltrims look great using those numbers. My injectors are 8.1L 42lb marine injectors that I got from Arizona speed i think.

All I know is, my Nelson tune had them set at 5.15 accross the board, and someone from HPtuners said to set them at 5.25 across the board. I have no problem doing this, but, when i do my ltrims are totally whacked and adjusting the VE doesn't work as far as I can tell.

 

If you have a vac ref'd regulator, you should have the same value in every cell and it should be the actual flow rate of your injectors at 58psi. If you populate that table with multiple values, you are using GMs work around for *not* having a vac ref'd regulator (e.g. providing different flow rates at different vacuum readings -- which is what the VRR does).

If you are running a tune with non-vac ref'd IFR values, and then switch, your VE will be waaay off. To adjust your VE, you need to do SD tuning -- otherwise, you are fighting the MAF the whole time.


An easy way to tell for sure is to look at your stock tune. If it has a single value, your performance tune should have a single value.

 

i haven't done so yet, but, it was suggested to me that i should cap off the vacuum reference. bad idea?


i think i'm gonna put a stock tune back in and start all over again.

 

the reason for not being able to adjust the whacky trims with the ve is because your still using a maf, if you adjust the maf table once the ifr is set you will be able to line the trims up

 

if you want to tune trims with the ve you need to be in SD

 

i tuned a complety diferent way. didn't touch the ve table till the very end.

put in the ifr number you think it correct and go for a spin. check your ltrims at idle and part throttle. if they are positive in most places adjust the ifr till they are slightly negative.

once your ltrims are slighlty negative then use your wideband to adjust for WOT fueling. adjust with the PE vs RPM table.

i dont see the point in messing with the ve table unless you are having some kind of driveabily problems. just let the maf do it's job. with the whipple i never had any problems tuning this way. once i got the turbo on there and started turning it up things got kind of wierd and i then had to play with the ve table to get the throttle transitions smooth.

i am not saying the SD way is wrong, just not how i did it and i dont really understand it. if you unhook the maf be careful with boost, infact i would keep it out of boost all together, the 1 bar map can not see boost and will not add fuel for it.

 

so how much boost can the maf see before it maxes out?

 

Ok, this is what I was told to do by darkblueta. I was feeling pretty good about tuning this way until i started reading that it was a horrible idea to mess with the ifr table. I think i'm gonna try both ways and see which works best for me. Trying to stay out of boost is not easy, wow.

I noticed tonight that my advance is totally whacked too. Looking at my max and min in the histogram, they are not even close in some cells. Like 0 min and 35 max. What could be pulling that much timing? No KR.

Also, after doing a WOT run, my truck runs like ****. Almost always. Is there some sort of abuse mode or something that it could be falling into? My wideband works great until after I go WOT. Then it reads 11.25 in every cell. WHY? I was told it's the CAT over temp. NOPE, i have it disabled.

 

chances are your wideband is bottomed out. running to rich that it is reading as rich as it can. dont worry about that yet. get your ltrims slightly negative at idle and part throttle, then make sure they goto 0 at wot. then start pulling fuel till you get it up to 11.8 or so.

the stock maf isn't limited by boost but rather by airflow. can't remember when i maxed mine out but with a 4.8 i would guess 15+psi before you start bumping the limit. just bumping the limit isn't a big deal either, it is when you max it out at 4000rpm you have tuning problems.