My blown 385 is running to fat at idle to pass smog and to a lesser extent at 2400 rpm's. Anybody have any ideas to lean it out at idle and cruising speed. I was thinking of changing the injector constant to 75lb. I use tunercat for tuning. Would taking it to a wideband O2 dyno be a god idea to tune to pass smog?

 

holly crap 72# injectors

your web site only says your running 5 lbs of boost? thats way over kill.

have you done any datalogging? is your blms getting maxed out?

 

I have no FMU and I went with 72# ers for the idle quality and they are a much more responsive injector, Also My 50# ers were 100% duty cycle at 5400 rpm,s. I might only be at 5lbs boost but I'm putting down around 550 rwhp and plan on upping the boost to 10lbs after smogging. My main problem is I want to get this thing lean enough to pass smog at idle. I just looked at my programing and noticed the EGR settings at idle and off idle were set at 6750 rpm,s so I set those back to stock setting which should me at cruising speed but not idle.

 

Changing the injector constant is definatley an option but that will lean out the whole curve. Are you using an FMU? Is it functioning properly? Another way to lean it out (controversial) is with the VE tables, some say the engine doesn't use these unless it is in speed density mode. Or you can change the MAF calibration by decreasing the g/sec at the desired rpms. the idle problem could also be fixed using the cylinder balance at idle table. Just my .02.

 

Do a search for idle PE mode or PE mode at idle. That is your solution.

 

72#/hr injectors running at 80% DC should be good for 840Hp, even using .55 for the BSFC value. So, I figure that something must be wrong with your setup, because it really does not make any sense that the 50s were not big enough for you.

On my 395 cu.in stroker motor, I have determined that 42#/hr (40psi fuel pressure) FMS injectors will be good for 550Hp on a twin turbo setup, and good for 627Hp at 52psi. This is all at 90% DC.

I dont want to seem arguementative, but as asked above, what are the BLMs in the various fuel cells, especially the idle cell 0? I would expect them to be very low.

One other point, it could be that your O2 sensor is FUBRRED.

 

I haven't been able to log another Datamaster run lately because when I was uploading a few changes to the program Tunercat seized and I had to send the computer to Ion Solton. While he's got it i'm having the chip socketed so I won't have this problem again. I've upload programs about 40 times and never had it seize before.
Back to the subject at hand, The last run I logged short term blms were 124 to 134, Long term 131-140 cruising and 128 at idle with a mail order tune and the motor not broke in. Injector duty cycle with the 72#er's was 62.4% at 6300 rpm. My motor will pull to 7000 rpm now that it's broke in so I think I will be needing the 72's as I plan on also upping the boost at some point. The motor has always run good just fat at idle and a little fat cruising in the 2200 rpm range. The running rich at 2200 rpm I think I can solve when I get the computer back because in the program the tuner had the EGR turned off. The 50#er's were enough before I built the 385 on my old 355 with 8PSI boost, I never saw over 80% duty cycle. On this motor I have had extensive head work and different cam and I can only tell you what I have been reading on datamaster. When I get the PCM back I plan on logging some more runs and checking the O2's which are fairly new. I'll post when I find out what's going on although I feel it's the injectors at idle.

 

The typical problem with a large injector is not being able to "turn it down" to the very tiny pulse width you need at idle. End result - runs rich. What type of injectors are you using (pintle, disc, etc)? What are you driving them with (FAST, DFI, MoTeC, etc)?

 

I am running Siemans Deka injectors with the pencil beam spray pattern. I'm using stock PCM with Acceleronics converter box. I was thinking of lessening the pulse width at idle or tuning open loop to pass smog. If anyone has had the same problem at idle and has a specific fix it would help.

 

The only way to cut down on idle fueling is by enabling PE mode at your idle RPM whatever that is. Then you have to experiment with different values till your idle no longer smells rich. Also helps to look at the O2 mVs and when they hang around .05x-.15x then that in my experience is as good as you will get w/o potential harm to the motor. You have to overshoot or aim for a lean O2 reading b/c of the valve overlap feeding fresh unburnt air the O2 sensors in effect teasing them into see a lean mixture.