For the love of a tractor engine: The life and times of the 18R-G

[Omegaman]

question for you guys.
Since the rebuild of my 18rgu with EFI, i've fitted a air/fuel ratio guage. tried to tune the car using this gauge as a guide. while getting the timing right at 12 deg btdc, idle at 850rpm.
The gauge shows that the engine is running way rich and will not reduce. Would the be because of the oxygen sensor picking up loads of oxygen still in the gasses. Due to the lack of bedding in? what should the next step be for the fuel and air flow meter adjustment be?

[o_man_ra23]

A few questions, what ECU are you running, and what was done to the engine when rebuilt?? Also, how good is the AF meter, and why don't you use the oxy sensor as feedback to the ECU??

[Omegaman]

the ECU, is the standard 18rgeu comp.
rebuild included 9.7.1 comp pistons, 18rg 231 cams,balancing, nothing else over and above.
air flow meter geu std, oxygen sensor is conected to the ecu.

[o_man_ra23]

What are you adjusting to tune?? You can adjust the AFM that I know of... are there adjustments on the ECU?? If you do adjust the AFM, make baby steps, and mark where you started. Dont forget these motors were woefully tuned from factory, and the ECU's arent much chop, so I dont think you will get too good a tune, and if you do improve it, keep an eye on knock/pinging/detonation/whatever you want to call it.

[Omegaman]

well, I adjusted the timing. used the idle screw to adjust the idle to 850rpm.
seeing that the fuel/ratio was rich, I played with the air flow meter screw.
Would it show rich due to being idle, that is, not at driving speed for lack of air flow. Or am I reading it wrong, receiving to much air ,so the fuel increases to compensate?

A a further note, I am considering opening up the air flow meter to adjust the tentioner 2-3 lugs, for better response. what do you think? may or my not help with above problem???

After this tune and bedding in, if research is fine, with attempt bigger injectors and emange piggy back system.

[RAd28]

might be worth marking where the setting on the AFM is, then adjust it pretty dramatically until you can notice a significant change in the way the engine is running then check the AFR gauge, to see if there's any difference... you might find there's nothing wrong with the tune etc, it might be something to do with the gauge or how it's connected...

just something else to try.

[o_man_ra23]

Again, what quality is the guage??

[Omegaman]

the gauge is the auto meter type, retail $150, bought new $100. its a repco, auto barn type
digital lights yeh.... there's 3 wires on the gauge, oxy sensor, earth and power?
the gauge seems to work fine.
double checked the tune, all good, ratio still rich,

[o_man_ra23]

Ok, guage is good, how about the sensor?? if its pretty new, then I would still back that you need to play with the AFM more... or go and get a proper ECU

[Omegaman]

I will play with the AFM first, then the sensor, ECU well who knows.
if I manage to connect the emanage piggy back. maybe this will fix the rich fuel problem.
But I feel there something still to do and adjust prior to this.
No one mentioned if the lack of running in, can cause the rich setting?

[o_man_ra23]

Not really, rich goes on feedback from the AFM, TPS and oxy sensor, should be able to account for a motor that is tired or not run in.

[Omegaman]

yeah, but somewhere I read that the oxy sensor measures the unused oxygen in the exhaust. wandered how that comes about.
senario. more oxygen registered in the exhaust, more fuel added to compensate.
does that mean my afm is sending to much air? therefore , back to afm adjustment

could it be possible that theres to much fuel and not enough afm adjustment?
would this lead to fuel regulator req'd. which a fuel pressure gauge is my next purchase anyways.

[o_man_ra23]

The ECU has a lookup map where it decides the injector duty cycle based on rpm, AFM reading and TPS reading. It uses oxy sensor feedback to fine tune the duty cycle. If the AFM reading is too far out, the oxy sensor will only fine tune so far, and then it wont give you any more. So yeah, AFM adjustment.

And yes, more oxy sensed in the exhaust, more fuel added to compensate, but more open the AFM reading is, the more fuel added for the base map, the oxy sensor will be trying to lean it out, but obviously has not enough sway.

If you knew your automatic control theory (3rd year Electrical engineering, or 4th year mechanical) then you would see where I am coming from.

[Norbie]

I should add that the ECU only trims the fuel based on O2 sensor input during cruise conditions, ie low load and low to medium RPM. As soon as you stomp on it it goes back to internal fuel maps and ignores the O2 sensor.

[o_man_ra23]

Ahh, so it doesnt trim on Accel/Decel... that makes it even worse!! So yeah, AFM or TPS is your issue.