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Yep, it ran better when the engine ran rich on throttle. The fact that you are capable of breaking out of your bracket means the engine still has plenty of potential. I am not sure if the ECU in the 4G64 works this way but some OBD-II's can be forced into 'closed loop' mode by grounding the O2 wire. If it can go into closed loop you can then retune your ignition and make use of the extra fuel. It shouldn't be running that lean AFAIK so there's a chance that something is up:shrug:
Get a code reader onto it and see if there's a fault somewhere (will be hard to detect if it's intermittent) Check your plugs for visual signs of leaning out. An exhaust leak upstream from the O2 sensor? Could also be a tired fuel pump not providing full fuel pressure or a clogged fuel filter or pick up in the tank. Maybe an injector clean is in order too...
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Don't forget.. this is OBD-I so I only get codes in the form of electrical pulses read on a oscilloscope or old style sweeping dial volt meter.
I'm running a fuel cell with an external electric fuel pump running at 58 psi. New lines front to back and newer filter.
I will need WAY more fuel when i go turbo.
The exhaust manifold was milled flat before installation.
BUT... I agree that I possibly forced the ECM into Open Loop for that last pass. It also pulled cleaner through the gears.
I think I'm running lean and the ECM is certainly not compensating for that.
Next year it gets a sniper system... then i will have lots of fuel..LOL
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And I goofed on 2 counts - trucks are OBD-I (which you've correctly pointed out) and indeed it is open loop. There are ways to nerf the closed loop - maybe disconnect the temp sensor or grounding the O2 sensor wire:shrug:. A friend of mine was helping his former boss with his Excel Sprint Cup track car. They are forced to run stock ECU's and engine internals, but he fudged the ECU into open loop and retuned the timing. It was definitely faster on track than the other cars it was up against... I'll have to ask 'the man' ;)
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huh? :scratchheadyellow: ...and here's a thought. Is ethanol in the fuel screwing with the ECU trying to maintain AFR stoic value of 14.7? It might actually be lower than that - like 14.2? And there's the mystery lean run factor. Looked at a few forums and disconnecting the temp sender seems to force the ECU into open loop (can't confirm that as fact for the Mitsubishi OBD-I ECU) This could turn into a separate tuning thread :think:
As for ethanol - I can't give this any credibility but here is something to read:
https://e360.yale.edu/features/the_c...or_environment
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That is a good point about the Ethanol. When I go to a wide band 02 when I switch to the Sniper System in the spring I will certainly be able to check more.
I only have 1 more day of racing on October 16. I might try a few things to see if I can get some more.
I'm contemplating replacement pistons or just a hone and re-ring. It will smoke a bit N/A as I will have to open the ring gaps until I can get the rest of the turbo (or blower) combo figured out.
I'm just unsure if the Eaton blower I have can be used with a suck through as it doesn't have seals on the ends of the rotors ...
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Only way to know with the block and bores is lifting the head off. If they're not carved up and there's no visible lip on the top of them, I'd be tempted to deglaze the bores and throw in some new standard size rings and call it. I don't know if the Eaton will like being set up like that. Wonder how ITB injection would go? Bike throttle bodies are hell cheap to buy...
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I looked at last years dial for Mopar day. I dialed 19.86.. I ran a second quicker this year with only removing the cat, change of timing.
I did fix the ground issue and my Air Fuel is fine. It cycles between 15.5 and 14.0 which is normal
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Gaining a second isn't a bad effort. Column shifting is no easy feat either! Next year you'll be on sub 18 passes no problemo :thumbup:
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I ran 12's in my big block aspen back in the day with a column shift... have to be precise or you go right to drive.
I think after the rebuild I should be able to run in the 17's N/A
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Looked at my first pass years ago and it was a 20.33 LOL.. 1.38 sec increase in performance since then :D
