JoeDirt

I have a set of 42.5's installed on my cam and bolt on ls1. Since the install the car wants to surge / stumble when I go really light - no throttle on decel. It also stalled a few times on start up.

Its a 6spd. Air fuel looked pretty good on the dyno wot was 12.6 - 12.9 na and 11.5 - 12.1 on a 75 shot.

With these injectors is it possible its running pig rich down low because there so blooy big the pcm cant pulse them short enough ?? Is there any way to tune for light throttle use without effecting WOT ??

Thanks

383838

iTrader: (1)

There is a decel fuel cutoff table that can be used to get of the decelleration burble. The 42's can be tuned fine. If it's stalling on startup then chances are your IFR table is not scaled correctly and/or you have an 02 issue. I'm guessing your a stock cam with just nitrous?

JoeDirt

which way should I go with the decel fuel cutoff table ??

It has an MTI stealth II cam and bolt ons but runs very well , no stalling etc until the injector swap. It stalled twice . . . . I only drive it on weekends so it sits for a while and when I fire it up its pretty ruff. It smooths out after a bit each time.

Cam specs are 224 220 581 581 116 lsa

I think its rich as hell on decel maybe ?

HurricaneZ

iTrader: (1)

I'm still fighting the same thing, I've tried everything I can think of:
ve table - nothing
richening IFR table in affected areas - just makes my LTrims more negative
disabling dfc - nothing

I have a in car wideband and the surge is created from the car leaning out. It always happens @ 25-30 MAP so usually between 1500 and 2000 RPM on light throttle or on Decel when the map is in the 25-30 range. I'd love to figure this out myself. By coincidence are your injectors the Dephi injectors?

JoeDirt

Nope I have the Bosch injectors.

Lean thats interesting I would have tought the opposite ?? Anyone know why they would go lean ??

I need a wideband

JoeDirt

From HP Tuners heres my table

Stock
3.62-3.64-3.66-3.69-3.71-3.73-3.75-3.77-3.80-3.81-3.84-3.86-3.88-3.90-3.92-3.95-3.96

42.5 @ 39.15 psi

6.12-6.15-6.19-6.24-6.27-6.30-6.34-6.37-6.42-6.44-6.49-6.52-6.56-6.59-6.62-6.68-6.71

JoeDirt

Out of curiosity . . .Is there anything else that should have been modified with the fuel injector swap besides this table ??

slyws6

This is what I did and it seems to work fine so far....

Subtract your stock injector size (depending on year) 26lb's (for mine) from your new injector size of 42.5 to get 16.5 Now multiply 16.5 by 100 to get 1650, divide that by the stock injector size of 26 to get your increased percentage of 63.46 Now multiply your IFR table by 1.6346 to get your new settings and you should be good to go. Now keep in mind this is assuming that your 42.5lb injectors are rated at 43.5psi, typically most injectors are rated at that fuel rail pressure. Good luck.

((42.5 - 26) x 100) / 26

-Sly

Bill's 02 Z-28 SS

Hi Dirtjoe,
Just for my curiosity, how can you get the RWHP & RWTQ from a stock LS1????
Bill

JoeDirt

you meen my sig . . . da sneeky juice

JoeDirt

Interesting . . . I was told without a doubt they were rated at 39.15 psi so they would be 51# on my fp.

Thanks for the help Ill go over the math . .

JoeDirt

wow thats very different . . .

Stock
3.62-3.64-3.66-3.69-3.71-3.73-3.75-3.77-3.80-3.81-3.84-3.86-3.88-3.90-3.92-3.95-3.96

42.5 @ 39.15 psi ( In my pcm )
6.12-6.15-6.19-6.24-6.27-6.30-6.34-6.37-6.42-6.44-6.49-6.52-6.56-6.59-6.62-6.68-6.71

Your Math equation
6.14-6.45-6.48-5.53-6.57-6.61-6.64-6.68-6.73-6.75-6.80-6.84-6.87-6.91-6.94-6.99-7.01

Air fuel was 12.6 - 12.9 wot NA with my current tune so if I used the new numbers wouldnt I go pig rich ??