Thumpn

The issue i am having is on start up and dfco, so on start up i have to give it almost full throttle to fire but when it does it only runs if i hold the throttle for a about 2-3 min till the engine temp gets up to about 90deg and then I can take my foot off the throttle and it will idle at 800 like i have it set to, that is on a cold start. on a worm engine start i still have to give it throttle but as soon as it fires i can let the throttle go and it idles fine.

and as far as dfco when i let of the throttle to caost to a stop it tries to die i think cause it is getting really rich, it is showing that on the wide band. but the idle gets down to about 400rpm and the Wb is showing 10.2afr. so my problem is I cant figure out how to adjust for that with running a SD tune.

I know i have had issues with running in the past but now as far as my running I have that going really good im just having the above issues.

set as follows:
Setup as follows:
6.0 forged bottom end , dish pistons 7:1 comp
6.2 stock truck heads
78/75 turbo
160 lb bosch injectors
twin 320L in tank fuel pumps
2010 zr1 cam 211/230 @ .050 valve lift and .558/.552 lift
LS2 cam sensor in timing cover
Ict billet intake w/92 mm Tb
napa crb219481 3 bar map sensor ( gm 12223861 alt replacement)
wastegate w/14lb spring

log and tune below

Darth_V8r

iTrader: (4)

This may or may not affect your cold starts, BUT your transient minimum fuel needs to drop to 0.005 or possibly just zero it altogether, since your injectors are so big. I use 0.010 for 42# injectors, and you are at 0.019. Second, the transient RPM, I usually put to a number higher than idle speed. Like 1100. That will at least allow you to lean out at warm idle. Once you get your idle to lean out, and get it dialed in, that may also help your hard starts.

Having to give it pedal to start means you need more air, which means either you are very rich (which you are) or your tune is not commanding enough air. Your base airflow at lower temps could stand to increase, and you may want to add to your start up airflow initial table and your IAC park position airflow should be increased. Those are things I tend to do when a car wants pedal to start.

truckdoug

iTrader: (25)

Hey Darth,

I have a question if I could hijack this thread for sec. When I do a write calibrate the computer needs to fail the maf before it reverts to SD right?

It's a pita to start, usually I have to pedal the throttle for a sec and then they fail.

Is there a way around that? maybe set the fail hx to something other than zero and then put in my desired airflow in that maf cell?

Just curious. Not a huge deal, but it gets annoying after like 10 flashes in a row of pedaling it.

Darth_V8r

iTrader: (4)

I wish I could take credit for this one, but it was Subeone who taught me this trick. Set your lowest cell in your maf curve to something like 20 g/s. When you unplug the maf, it defaults to the lowest cell until the maf fails, but the maf won't fail until the car starts. And the car won't start until the maf fails. it's the circle off life. By setting the lowest cell to 20 g/s, the ECU sees 20 and gives it enough fuel to start and stay running. Then a few seconds in, the maf fails, and the car is in SD.

This is necessary even if you are using the SDOS. The maf still needs to fail. How I learned that? A while back, my car was perfectly stable with the maf plugged in on SDOS, and unplugging the maf sent it for a loop. Until I fixed my SD tune.

gofastwclass

iTrader: (2)

Brilliant! Thanks for that little tip on SD mode, Darth. I'll have to save that one.

Doug, how is it you always ask the questions that are on my mind?

G Atsma

Doug is telepathic OOPS now he knows I'm telling you this...

truckdoug

iTrader: (25)

I remember Darth talking about it in another thread about hard starts when cold.

But I am working on my ESP

Bry, yes you should do a truck for one of your next builds. Yes, a 60-66 preferably.

gofastwclass

iTrader: (2)

I see.

Not funny Doug! Hahaha!
If I build one I need to make it an extended cab, my legs are too long. The wife says she would happily drive while I sit sideways in the passenger seat though. Hahaha!

G Atsma

Maybe you need the operation where they saw about 3-4" out of your shin bones and re-connect them... THEN you'll fit in an old truck cab! Cool, right?

gofastwclass

iTrader: (2)

Now you sound like my friend short friend ls1nova71... He literally suggested the same exact thing a few years ago! I politely told him "no f-n way!" Haha.
My solution is to make an extended cab so an adult or anyone with an inseam longer than 30" can drive one of these trucks.

G Atsma

I'm right at 30" inseam... I know what you mean.... lol