Ok, I got the LM-1 A/F ratio meter installed in my vehicle. It runs on a JTEC computer. Its stroked, bored, adjustable fuel pressure regulator, oversize throttle body and the right size injectors. I drove it home from the shop tonight and it is idling at 12.5 and down the road it is dead on at 14.5-14.6 from off idle to 3500 rpm cruise. What do my fellow moparts members think I should do? I can put in an adjustable map sensor. I want to lean out the idle and richen the acceleration and lean out the cruise. Tim

I like to see 14.8 or leaner at idle, I have been able to cause detonation at 14.8 at part throttle cruise on a heavy pull I have also not seen damages at 15.3 at WOT above 4500 RPM Shoot for 12.2 to 12.8 on acceleration and 14.8 to 15.3 at part throotle cruise under light loads. I live at 3500+ elevation, 91 octane with no Ethanol, tune for your conditions and fuels

Ok, that is what I have been reading on the net, so How do I get the idle closer to 14 and the acceleration closer to 12? They seem to be backwards. I am thinking of installing an adjustable map sensor. Tim

If the JTEC is running off of a stock narrowband oxygen sensor, you can't do anything to the cruise a/f ratio. The computer is in closed loop operation at that time.

I was thinking of backing off the fuel pressure some for better a/f at idle and then installing one of these:
http://www.jeep-xj.info/HowtoMAPsensor.htm
It only works at 80% throttle and higher but it might help control the ratio better under load.

Well I backed down the fuel pressure until I got 14.5 A/F ratio. I drove it around and the cruise stayed 14.5-14.6. I would like it to be a little richer under acceleration. When I let off the throttle, it must cut off the fuel because the ratio goes above the meter limit. Tim

I do not know waht a JTEC computer is, sorry I guess I was assuming you where able to change the fuel map with a laptop We all know what ASS U ME means

Jeep Truck Engine Controller stock mopar ECM....Tim

What are you getting for a/f under full throttle acceleration? Cruise and light acceleration will stay near stoic with a stock ecm, just the way they work with the narrowband o2 sensor.

I could only do full throttle for a few seconds, but it went from 15.1 for a blip to 13.8 then back to 14.5. When I let off the gas, it jumps to 89to1 until the engine reaches idle. I used to get ping real bad with the last stroker pistons and regular gas. I had the pistons dished 7 cc's to get my dynamica/static compressions down. Tim

Is your fuel pressure regulator vacuum referenced?

You need more fuel pressure or bigger injectors for WOT, but then your idle will be overly rich. A vacuum referenced pressure regulator will cut the fuel flow at idle down a bit if you don't already have one, but I don't think it will be enough. You will likely need your ecu reprogrammed.

Also, isn't a warm idle supposed to be closed loop with that ecu? If so, it's already running richer at idle than the ecu can compensate for without recalibration.

have you looked into using SCT to reprogram the computer?

you can tweak a lot of stuff in it, but I'm not sure if you can tweak the closed loop modes. my Dakota has a 5.9L 222/228 @ .050, .544 lift, and 107 LSA. it will idle at 14.7, part throttle cruise at 14.7, and at WOT it goes to 12.8

it took several tweaks using a data logger to record what was going on, and sending that to my "program writer" For a little over $300, he sends you the hand held programmer, CD with the programs to put programs onto the handheld, and unlimited tunes for the life of the vehicle, so he'll help you get the tune dialed in, then if you change anything later, he'll help you re-tune it for free.


contact Sean Powell, aka "Hemifever" www.hemifevertuning.com or hemifever@aol.com

By the way, there are a lot of Dakota's running 408 strokers, boost, spray, etc. all using the stock EFI system/sensors and computer reprogrammed with SCT

Also, the computer has a "coast down fuel cutoff" under closed throttle, high vacuum, deceleration, the computer will stop grounding the injectors and fuel delivery stops. This is a fuel economy trick and you can see it happen with a wideband O2.
Note factory programming has a 5 second delay before this "kicks in". But with SCTi have mine programmed for a 2-second delay