Running lean

shaunditty

Shaunditty
My truck seems to be going lean on longer pulls. It runs great overall. No issues.
I have a Autometer wideband, fuel pressure and boost gauges in the truck that I watch. It all seemed to start last year. So I put a new FMU and Walbro 255 in-line in it. It does it on either tank. When I first put a supercharger on it a few years ago I put a Powerdyne on it and the AFR gauge would read 10.5-10.9 during a entire run and I even attempted to put a 10:1 FMU disk to lean that out and it didn’t change much. I put a Vortech in it with a 3.15 pullley and it seemed good at first. I wanted to turn it up so I put a 2.85” on it and was seeing 10-11lbs boost. I noticed it being slightly lean then. What it does is from a dig the AFR starts off at 10.9 and fuel pressure is 100+.. boost is the highest at lower gears and as i go deeper into the run my AFR gauge will start creeping up to 12.5-12.9 so I let out. The fuel pressure is still 100Psi+ though.. that’s the highest my gauge will read. So I put a 3.125” on it which is around 8psi boost and it’s still going lean at the top of the pull. I’ve thrown a lot at my truck lately too. I deleted all the smog and EGR stuff. I put 1-5/8” long tubes and I hacked together my own 2.5” dual exhaust. I drove it today and man it runs good and everything seems good. I can feel a difference in the power increase from the recent changes I made. I just wonder why it’s leaning out up top like it is and what I need to do to fix it. I know it sounds crazy but every since I put the Tial BOV in it and removed the Bosch valve is when this seemed to start happening. Unfortunately I sold that setup and can’t switch back for testing purposes.
 
My truck seems to be going lean on longer pulls. It runs great overall. No issues.
I have a Autometer wideband, fuel pressure and boost gauges in the truck that I watch. It all seemed to start last year. So I put a new FMU and Walbro 255 in-line in it. It does it on either tank. When I first put a supercharger on it a few years ago I put a Powerdyne on it and the AFR gauge would read 10.5-10.9 during a entire run and I even attempted to put a 10:1 FMU disk to lean that out and it didn’t change much. I put a Vortech in it with a 3.15 pullley and it seemed good at first. I wanted to turn it up so I put a 2.85” on it and was seeing 10-11lbs boost. I noticed it being slightly lean then. What it does is from a dig the AFR starts off at 10.9 and fuel pressure is 100+.. boost is the highest at lower gears and as i go deeper into the run my AFR gauge will start creeping up to 12.5-12.9 so I let out. The fuel pressure is still 100Psi+ though.. that’s the highest my gauge will read. So I put a 3.125” on it which is around 8psi boost and it’s still going lean at the top of the pull. I’ve thrown a lot at my truck lately too. I deleted all the smog and EGR stuff. I put 1-5/8” long tubes and I hacked together my own 2.5” dual exhaust. I drove it today and man it runs good and everything seems good. I can feel a difference in the power increase from the recent changes I made. I just wonder why it’s leaning out up top like it is and what I need to do to fix it. I know it sounds crazy but every since I put the Tial BOV in it and removed the Bosch valve is when this seemed to start happening. Unfortunately I sold that setup and can’t switch back for testing purposes.

Sounds like you are running out of injector.
 
Bare minimum you could try a tweecer or quarterhorse to increase injector pulsewidth. Or add meth injection although it is a band aid.. it would work. Otherwise you will need bigger injectors and a tune.

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Yeah.. I kinda figured that. I figured at 8psi that the FMU/19’s/Walbro255 in-line could still handle it no problem.
I bought some 42lb injectors recently and have been looking at getting the Pimp stuff
 
At some point your injectors start to open slower against that kind of pressure. Combine that with the fact that the batch fire arrangement means the injectors have to cycle twice as often, which doubles the amount of opening time/closing time/etc., and you end up in a situation that more pressure just isn't going to fix.
 
I just ordered the pimpxshift and it seem pretty easy to get the hang of. I also got their spartan 2 wideband controller & sensor kit. Have to wait to get it was on back order. I havent started installing because the truck is going for paint soon but I think it's going to be pretty simple to get it going. I'm currently tune with a tweecer rt and 42 lbs injectors with Steve Stock tune.
 
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At some point your injectors start to open slower against that kind of pressure. Combine that with the fact that the batch fire arrangement means the injectors have to cycle twice as often, which doubles the amount of opening time/closing time/etc., and you end up in a situation that more pressure just isn't going to fix.

I’m pondering my next move! Lol

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Bare minimum you could try a tweecer or quarterhorse to increase injector pulsewidth. Or add meth injection although it is a band aid.. it would work. Otherwise you will need bigger injectors and a tune.

Sent from my moto z3 using Tapatalk

If anything I’m getting the pimp stuff

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I just ordered the pimpxshift and it seem pretty easy to get the hang of. I also got their spartan 2 wideband controller & sensor kit. Have to wait to get it was on back order. I havent started installing because the truck is going for paint soon but I think it's going to be pretty simple to get it going. I'm currently tune with a tweecer rt and 42 lbs injectors with Steve Stock tune.
Dude I just bought 42’s last week! Lol

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Sounds like you are running out of injector.

That sounds kinda sucky, maybe a 2 pump trick for now?
 
This truck is running great. It doesn’t miss a beat. It feels faster than it ever has. Is a AFR of 12.5-13 risking it? I usually have race gas in it, as I live right next to a gas station that has it, and I don’t drive this truck much. MSD retard box always set on 1.
 
This truck is running great. It doesn’t miss a beat. It feels faster than it ever has. Is a AFR of 12.5-13 risking it? I usually have race gas in it, as I live right next to a gas station that has it, and I don’t drive this truck much. MSD retard box always set on 1.

I wouldn’t run that lean, also don’t think adding more pump will help if it’s lean on 100 psi fuel pressure
 
I honestly think pimpxshift is worth the money for what you get and I having good luck with 42 lbs injectors. Never really cared for the fmu setup, felt it wasn't stable or consistent. I feel with the the 42s and a tune you'll be able to get the afr right where it needs to be and have a stable and consistent fuel system. With the fmu setup stock injectors and no tune my truck basically what you have now roughly my truck made 10 psi with 8" crank 3.33" upper. After 42s and tune same crank and same upper truck made 14 psi .
 
For you yes your running a smaller crank than me. I run the 8" 8 rib renegade crank pulley
 
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I installed a 3.33” upper pulley. My FMU and Walbro should be able to handle that. If not then somethings not right. I’m questioning the accuracy of my wideband gauge. I bought it in 2015 and I’ve used race gas, leaded 110, mixed and not mixed for a long time. I wonder if it can be inaccurate now? My garage door broke and I can’t get my truck out at the moment so I won’t know for a few days or not how it does now. I want to upgrade to the pimpxshift but you know my truck is pretty much stock with a blower. I drove it normal most of the time and it runs perfect. So trying to hold off for a few on that $1600+purchase. Especially since I’m getting a new garage door now
 
Shaun, I installed the PiMPxshift in that stock white truck and it made the truck better then with the stock ECU. It’s well worth the money.
 
I really do want to get it and I eventually will. I’m looking forward to be able to raise shift points, delete the speed limiter and turn off my EGR/smog related codes I now have. I bought some 42# injectors recently too.
 
It’s one of those things where once you brake down and do it you’ll wish you did it years ago.
 
Plus you get a lot for your money compared to other systems that you have to have ecm management and trans management. Also you could have a bad wideband o2 sensor. I had some false reading and it ended up being that.

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Got the truck out some today and it’s running great. 10.5-11.5 AFR range. I’m really digging the sound of the headers and summit chambered mufflers.
 
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