dizwiz24

I want to do an open loop idle to improve idle efficiency (speed density is not good with big cams).

I will use an msd rpm window switch to put the car into open loop mode below say....1100 rpm

does anyone know of what sensor i can disconnect to do this?

Someone told me once that coolant temp will do this if disconnected.

However, coolant temp seems to be needed, even in open loop mode for some %fuel adder tables (cold start)

So i cant do that one....

What other ones can i disconnect?

Can i disconnect just one of the o2 sensors and it will put it into open loop mode? Or would you have to disconnect both?

Kevova

Just disconnect O2 sensors. O2 sensors(s) provides feedback causing closed loop operation.

dizwiz24

The only problem with that is i have 1 window switch and 2 oxygen sensors....

Are you saying put some kind of double pole relay in there to do it?

if so, then the relay becomes another point of complexity/failure point in the system...

So if i tie my window switch into just one o2 sensor and disconnect that below a certain rpm will that be enoguh to knock the whole thing out of closed loop?

8a8mfh

I guess you want to do this cheap?
Good luck.
I tune my 93 with moates apu1 and tunerpro. With that it can be made to idle in ol. Or better yet tune it properly.

cormorant71

I did this with my '94. You can disconnect the O2 sensors. But a better way is to put a 1800 OHMS resistor on the temp sensor (this will read about 100 F). This will trick the ECM into thinking the car is still warming up and run in open loop. cheap, easy and better than the O2 path.

C

scotth48

I tune my 93 with moates apu1 and tunerpro. With that it can be made to idle in ol. Or better yet tune it properly.[/QUOTE]

I have a '93 and have the moated stuff and need some help getting the software to load and use the files needed to do it. I am not a computer guru by any means, any suggestions?

dizwiz24

i tune, just as you do, with a moates and tunerpro.

Trust me, you cant tune this out.

There is overlap in my cam causing intake oxygen to be seen as false air during that period when both intake and exhaust valves are open. The issue is most prevalent at idle.

Nothing you do to the tune will fix it entirely (ie. You subtract fuel, and the o2's see the false air from the overlap - interpret that as a lean condition and add fuel).

The only way the idle afr is steadily controllable (ie. Without jumping around all over the place) is thru open loop.

i still want closed loop to function at non-idle (highway cruise and other transients) situations.

8a8mfh

I found this https://www.corvetteforum.com/forums...op-93-lt1.html

Thats a long time to be fighting the same problem.

It can be made to idle properly through tuning, good luck.

dizwiz24

Gawd. This is embarassing.

I think that was the time I switched over to the 2 bar MAP tune (and was so focused on that), that I forgot the great advice given to me in that thread.

I remembered the thread, but forgot the great advice from bjanuski.