mark kibort

Is there a WOT switch on the LHjetrronic that is similar to the Ljet that makes the system go open loop. i had a particular situation at the track, and noticed briefly last race, where the air fuel meter is still hunting at WOT, where normally, its pegged to the "blue " full rich area, when WOT. i remember, if the WOT switch on the Ljetc was not working, it would run lean and would still be hunting. (going lean to rich about 5 times a second)
on the race video i noticed all the WOT section of the track were the AFR lights were to be pegged at WOT, there was some "hunting"
normally if you have a mixture problem, it might slowly show the leaner lights, but not random hunting lean to rich and back)
otherwise, i am indeed running lean and i have to find that issue in the fuel system (pump or injector issues). or possibly the o2 sensor is bad and not producing the proper voltages. it is fairly old and that seems like it would be a symptom of it going bad.
going to the dyno asap to check out as well.
thanks!
Mk

Ducman82

yes it does. internal idle and WOT switches.

dr bob

Mark --

Test at the LH connector with a meter (Ohms). It should be true/closed from about 3/4 throttle opening.

mark kibort

thanks! I was watching the video on all the straights... seems there is some voltage noise in the 02 system or its leaking out , sometimes. hard to tell. it might be ok,but its nothing to mess around with . seems to be running great.
Ill see if there is a connection closure at the LH. do you have the pin handy?

John Speake

The LH goes open loop well before the WOT switch is triggered. If you snap open the throttle at about 1/3 open and higher, the LH software detects the rate of change of MAF volts. It then provides the enrichment necessary to allow the engine to pick up, rather than falter due to the stoic 14.7 mixture.

This is a transient enrichment and the length of time it is effective varies depending on how large a throttle opening, and the rate of change. After the transient events, the loop may well stay open loop, depending on throttle opening and rpm.

mark kibort

Thanks John.. I was comparing video where you can see my ARF meter reading at the same event last year, and clearly you can see the meter in the "safe range " blue light, for anytime I was near or at WOT. was it only at WOT, for it to be open loop or does it go open loop like the early Ljet cars at 75% or something, before WOT?.

If you watch the video down the straight at thunderhill, you can see that it is "hunting" a little up and down full rich, full lean, while the throttle is pegged WOT. I'm hoping its an error in the voltage getting to the AFR meter because the 02 sensor is weak or failing? I noticed this same inconsistency at Laguna last month too via the video. never have I seen this before. but the car runs great and the plugs look good too and power seems fine. could it just be the O2 sensor playing tricks on me?

thanks,

Here is the video . FF to the second or 3rd lap when things are all warmed up. any ideas of what might be causing the change in the AFR readings?


Here is the race last year.

dr bob

Mark --

LH connector pin 3 gets pulled to ground when the WOT switch is active. The switch also connects to pin 26 in the EZK connector. White-with-red-tracer.

mark kibort

Ill check it . thanks! did you see the AFR hunting? it doesnt seem like it could be an actual reading..... maybe a bad connection?

dr bob

Trust but verify. If you don't have full faith in your mixture meter, remove it now and put it in the trash. It's only a distraction from your mission in the moment: winning races. Plus it's just extra weight.

Diagnosis:
Combining John's description of airflow measurement with target switch operation with your symptom, I'll speculate that the switch isn't working. You see the open-loop operation as airflow suddenly increases, but once stable again even at the high-load throttle position the switch isn't telling the controller to stay in open-loop. Instead it reverts to leaner closed-loop operation. You probably got slightly better gas mileage...

The switches fail when they fill with oil and crud. The connectors an wiring fail due to flexing and contamination. If you find that the test meter readings aren't showing it reliable, --replace the switch with new--. Once you go through the trouble of extracting the throttle and switch even if just for a connector inspection, the cost of the switch is relatively minimal. Plus it's not realistic to pull over and tinker with it during a high-speed drive.

mark kibort

thanks Bob... that certainly is what it looks like. that blue light would be stuck blue, sometimes fading to one light leaner bt it would blend..... subtly.... not that random hunting, LIKE the switch not doing its job to go open loop. better gas mileage? heck, maybe burned valves! (or worse, knocking). maybe the knock sensors are working or maybe its not staying at stoich long enough. scary in any event, if that is what is happening. it also caught my attention at laguna too, as that has NEVER happened in running this device in 20 years.

so, where is the idle switch sensor anyway? is it on the S4 throttle body? i dont recall.

i have another thought. if there is no fuel enrichment, like the Ljet,, what if i just connection the o2 sensor. doesnt this make the system go open loop too? ive done dynoruns with the 02 sensor disconnected and connected and shows the same exact HP run, and same mixture levels using a wide band at the 02 sensor hole, vs using the stock 02 sensor in the system and using a tail pipe reading.

interesting point about the mixture going rich upon full throttle but not stayning there based on a possible switch input. is that the switches only job? no other enrichment or features?

thanks for the help! MUCHO appreciated!

dr bob

Switch is on the side of the throttle body. Do the diagnosis and find what's up with it. Fix it. Don't half-fast kluge a workaround. Just fix it. Running full-rich all the time isn't good for the engine. Less power, washes the Amsoil off the cylinder walls.

The non-cat non-oxy-sensor engines have a different jumper code plug and have an airflow sensor with a mixture adjustment screw so you can at least get a loose approximation of mixture control. It's really a lot easier to do it correctly.

mark kibort

Ok, so I just checked the LH box harness for function check of the WOT switch. it seems to be functioning perfectly.

idle switch is pin 2 and WOT switch is pin 3 and both test out to be working without any clitches or inconsistencies.

I agree with you on the " Kludge , disconnect o2 sensor" . anderson ran it this way, but i still street it, and think that during off throttle or part throttle, its best not to have all that fuel in there running rich when it doesnt need to . build up of carbon, washing my amsoil off the cylnder walls , all not good.

So, the switch seems to be working fine. what else could cause a lean out ,that is so inconsistent? failing fuel pump?
water temp was actually lower than usual.. could a temp sensor do this? Even during this "lean out" reading situation, there is no loss of power or misfires, or surging. usually when there is a problem, you should be able to feel it. i remember my very subtle cam timing issue, was a 20hp loss on the dyno that felt weird down the main straights. (verified on the dyno) fixed by adjusting the timing and re-dynoing.

im puzzled.... could it be the 02 sensor? maybe its been cooked for so long, its going bad? After all, it is about 15 years of racing old now.

when i take it out next, ill do a full throttle run and see if i can simulate the issue.

dr bob

How much abuse has the sensor seen? Used any avgas or race fuel with lead in it? Lead in fuel is a sensor killer.

mark kibort

only 91 octane. never leaded or avgas.
only the red hot exhaust temps of racing. ill have to check out the videos to when this started. i think i saw a hint of it in the last laguna race last month. dont think the laguna before that was showing it, nor was sears point.

PorKen

I can patch whatever LH chip you are using to make the LH output a full throttle light* so you know it's working.




*via LH plug #26, unused shift light 12V- output