Tuning help needed.

[12sws27]

I have a 4.3L v6 4l60e 1998 GMC Jimmy with a centrifugal S/C @6psi. I just did a Marine intake swap so I can use bigger injectors. Everything is basically stock with the exception of the blower and marine intake.

The injectors I am running right now are 24lb/[email protected]. With my fuel pressure they are 27.7lb/hr. I entered that number in the "Flow Rate" box. Other then that I don't know what else to do to make it run better. My AFRs are real rich. And the truck feels slugish and even boggs down often. I'm just having a hard time trying to figure out where to start. Seems like most the info I find pertains to the newer pcms. If I'm leaving out any needed/helpfull info please tell me what I need to add to this thread.

Here is a log and my present tune. Any help would be greatly appreciated.

[12sws27]

Ok. I think I might be getting the hang of the fuel. The tuning for just part throttle is a lot simpler then my brain was making it. I ended up putting in 27.9 in the fuel rate. That's what the 24lb/[email protected] injectors are at 59psi. Part throttle driving has gotten a lot better.

Now for power enrichment tuning. I leaned out PE just a tad and I'm still getting AFRs in the 10's.

I'm getting weird lean spike right when I floor it. It seems to always happen at around 2000 rpm and 103 kpa MAp. I can't figure it out... I drove around while logging and just tapping the throttle. Every time I did it I got a lean spike. I'll post the log tomorrow. I need to sleep....

[12sws27]

I messed with transient fuel and it seems to have helped but I now get real rich spikes. I'm reading up on the subject as much as I can. Seems so many of you all have the newer PCMs so it's hard for me to find info I can relate too.

I also just realized that I was missing a bunch of perimeter because my nooby ass had my editor view option set on "beginner. Opps....

I've gotten the PE pretty good I think. I tried to get my afr in the 12's after 4k rpms but I got a small amount of KR. Some a richened it back up passed 4k RPM. My IAT are real high so I'm sure that has something to do with that.

I raised the base timing by 2* across the board and it work pretty well. Trucks pulling harder, no KR.


Can some one just mention a few this that might cause the lean spikes when I tap the throttle. It only happens at 0% TPS but happen right after I tap the throttle. So I guess it has to do with MAP changes?

Anything else It could be? Any advice as to what to look into, read up on? I'm already reading up on transient fuel.

[12sws27]

Here is a couple of logs where I was recreating the lean spike.

[12sws27]

Ok, so I think I figured out that those lean spikes that are after I tap the throttle are normal. They're nothing to worry about since they are alway at 0% TPS right?

Now the lean spike I get right when I floor it and then the truck goes into PE are because of the transient fuel not being set up right? Our is there something else? Maf tuning? Can the Maf setting be in need of adjustments and that causing the spike?

[12sws27]

No, I don't mind talking to myself at all.

Since I can't seem to find any info on the injectors that came with the intake other then they are 24lb/hr@3bar EV6 Delphi or Bosch (Bosch type?). I figure I'll put in the 39lb/[email protected] Injectors I have. I found all the specs/calibrations on those on this forum. The 24s are really enough any how. I'm thinking some of my problem might be from not having the right info wrote into the tune. I still have question though....>>>http://www.hptuners.com/forum/showpo...02&postcount=8

[12sws27]

I know that my thread title sucks and I'm probably asking some real noob questions. But damn.....I'm on a lot of forums and I don't think I've ever bumped a thread this many time and at least got a, "Search!" or "STFU n00b!" or something.

I'm reading my ass of but I keep getting stuck and can't get passed setting up my fuel injector settings right. I've searched all over for more info on these Bosch 24lb/hr@3bar injector (part# 0280156081) All I can do is enter them in at my pressure (4bar) and move on I guess. I have ford cobra 39# but I'm reading that I would have a hard time tuning for those so i got to sell them and find an injector I can get all the info on. Until then I want to be able to at least get the tune acceptable so I can go to the track.

Any one have any tips on what to do when you don't have all the injector data? Should I just put in the flow rate and move on to the next step?

[04 Intimidator]

I would start with my flow rate and go from there. To determine it, take your current injector size (or how they flow) and and divide by the new size.

I went from 33's (which act like 36's) up to 42.5's. So I took 36/42.5 to get 0.847. So I highlighted my injector table and multiplied it by 0.847.

It ran like ass for a bit but I reset my fuel trims and had to remap my MAF to accommodate the new intake, intercooler, and supercharger pulley I had installed.

Runs like a champ right now with a max of 2*KR but that is due to my wideband going up from one of those 36's going bad and not closing - just dumping straight fuel into the cylinder and lets say the Botch sensors aren't good running in excess of 10.5:1 air fuel for over 40 miles. =<

[04 Intimidator]

Just noticed in your sig box that your MAF is descreened. That is going to make it a PITA to tune! The screen straightens the airflow so the maf can read the amount of air going past properly. Your trims are probably going to be all over the place now and a bear to lock in.

Don't take this post insulting as to each their own, but I have never seen the screen delete give more than 2 hp but give hours upon hours of extra work tuning. You may want to consider rescreening the MAF or pulling it out completely and going with a Speed Density tune.

[12sws27]

Thanks for the reply With my PCM I have "Flow rate" which has a box next to it with a set number, no chart. I don't have "flow rate vs kpa" (which has a chart) like most. Is "flow rate vs kpa" what you're referring to? Or "Flow rate Modifier Vs Volts"? My "offset is also a set number but I do have "offset multi" which has a chart. I have the "box box" PCM. I'm thinking this might be why not a lot of folks are posting up.

I've heard that about the descreened MAF before. I desceened it awhile ago not knowing any better and left it like that in the hopes what I heard would be wrong. I guess it's time to get a new one. I'll probably just take the one off my other truck until I get another one from the junkyard.

Since the only data I can find on the injectors is the flow rate, I entered that and went on with tuning my LTFT in SD. I'm following this, http://www.hollandms.com/newbie/tuning_new.htm

I wish I could find one specific to my black box PCM. I plan on upgrading the PCM with a 0411 in the future because I plan on more power. So converting to SD will probably be the way I go. Right now I can't tune for a 2 bar map with my PCM. 1 bar only.

[04 Intimidator]

Correct, the flow rate vs kpa is what I was reffering to. What you did was correct by dropping in the new injector size is the right way to do it as you don't have other options. I would try to get the Flow Rad Mod vs Volts and Offset as well. You can try the manufacturer directly but you might have better luck with google.

Don't get me wrong, I'm not a big SD fan myself because it takes quite a bit to really dial it in nice and if you make one figgin change to the engine airflow you have to do it all over again but there are alot of gains to be had there.

[12sws27]

Correct, the flow rate vs kpa is what I was reffering to. What you did was correct by dropping in the new injector size is the right way to do it as you don't have other options. I would try to get the Flow Rad Mod vs Volts and Offset as well. You can try the manufacturer directly but you might have better luck with google.

Don't get me wrong, I'm not a big SD fan myself because it takes quite a bit to really dial it in nice and if you make one figgin change to the engine airflow you have to do it all over again but there are alot of gains to be had there.

Cool. I'll be doing my 3rd drive log with maf disabled tonight. So I hope it works with out getting the injectors offsets. I have been searching for that info before I started this thread and have been all over the net. Looks like my only chance is to call the manufacturer unless someone around here as the info. I figure if they do they spent the money on Greg's CD to get it and probably don't wanna give it up. I guess I can't blame them. Of course that's if the info is even in there in the first place.

I don't think I'll end up running enough boost to need a 2 bar SD OS. Maybe one day. I doubt it though. If I max out my MAF I can all ways upgrade to a LS2 MAF or ever the Lingenfelter 100mm one. I'm sure the ls2 85mm with be plenty though for my plans. I might need to start looking into it now since I descreened mine. If I can find a stock one cheap enough I might cough up the $170 or try to find one at the yard.

[12sws27]

I have just a few questions I'm wondering about. While I've been tuning in SD mode when accelerate my AFR peg lean. The truck acts like it wants to stall. But then it's fine and the AF got to stoich. There are also real rich spikes too. It's not as bad when it warms up but doesn't go away. I'm assuming this is normal since the MAF is unhooked? Or will that be something else I'll need to fix later in the tune?

Another question, I've read that when tuning my VE tables that I shouldn't reset my LTFT every time I've wrote in my changes and start a new log. I've heard that I should rest them too........which is it?

Last question for right now is, I'm thinking that it would be better to get my LTFT to be with in 5% on the - instead of the + side. Does it matter?

[Dogsofjune]

If need be, I have a stock MAF. Actually, I have 3 to choose from.

[Russ K]

Return the VE table back to stock as it is only 1 Bar. Then make the changes as shown to eliminate the PE delay. Log your commanded AFR & Maf Hz, and tune the Maf so the actual & commanded AFR match.

I would lower the WOT timing to 14* to start from 2000 rpm & up.

Russ Kemp

[12sws27]

If need be, I have a stock MAF. Actually, I have 3 to choose from.

DOJ, I will gladly take one of those off your hands. I'll PM you over on the planet and we can work out a deal.

Return the VE table back to stock as it is only 1 Bar. Then make the changes as shown to eliminate the PE delay. Log your commanded AFR & Maf Hz, and tune the Maf so the actual & commanded AFR match.

I would lower the WOT timing to 14* to start from 2000 rpm & up.

Russ Kemp

Thank you very much Russ! I'm going to make those changes to my file right now and write them in in the morning!

I've been reading so many threads and posts I think I am just as confused as when I when I first opened up my file.

[12sws27]

I would lower the WOT timing to 14* to start from 2000 rpm & up.

Russ Kemp

I'm having a problem here. I don't see anything under spark control that is specific to WOT timing. Maybe this is another of the options I don't have with my black box PCM? You think since I had just a a few degrees of KR with the spark tables set the way they are (which is just a few degrees higher then stock) I'd be ok to log some WOT now that I have a little more fuel? BTW, IDK if I mentioned it but I have checked my fuel pressure at 0 vacuum and it's 59psi. So I have 27.95lb/hr under flow rate now.

[s106banger]

i think your timing is map based isnt it? 105 kpa should be WOT right?

[12sws27]

i think your timing is map based isnt it? 105 kpa should be WOT right?

I was thinking that but I'm to noobish to be sure of anything still...

[s106banger]

were in the same boat dont worry.. lol.