Phil99vette

iTrader: (11)

Just a couple of things, did some tuning today and once I turned the factory O2s back on I saw that they wanted to correct to 14.4 instead of 14.7 on my LM1. Is there any way to way to make them correct to 14.7? I have a tendency to believe the LM1 vs the factory O2s.

I did the normal SD tune and when you turn the O2s back on you lose your smooth A/F transision that is programmed into the open loop EQ table(1.0 -> 1.13 ect). Is there a way to get the smooth transition back under closed loop like open loop?

SSpdDmon

iTrader: (10)

Try dropping your O2 switch points 50~100mV.

As for the transition, I would set all of open loop, operating temp AFR's to stoich and let PE come on as if it did in closed loop when I was tuning. To answer your question though...aside from going with a custom operating system running semi-closed loop, no. PE is either on or off.

1fstGM

iTrader: (13)

I know this is a newbie question, but can't you just leave them off? What are some advantages and disadvantages?

SSpdDmon

iTrader: (10)

Leaving the O2's off is what people are talking about when they say they run open loop (OL). Some run OLSD (open loop speed density) where the O2's and MAF sensor are turned off. Others just run OL or OLMAF (where the MAF stays on).

The O2's provide feedback around part throttle, where the PCM is commanding a 14.63:1 AFR. This feedback allows the PCM to "learn" optimal day-to-day fueling through the fuel trims. These learnings then become assumptions at WOT when positive fuel trims are added on top of know WOT fueling requirements. You turn the O2's off and your car behaves like a carburated setup - it is what it is and there's no self-adjustment. The upside? Well, if you want to think of it that way, one upside is you won't have any positive trims interfering with your WOT AFR. The downers...you're car won't learn, it could run pretty lean at times, inconsistent/worse gas mileage, etc.

Phil99vette

iTrader: (11)

Here is why I like OLSD:
You can start adding fuel @ 75kpa in a linear fashion to 105kpa
This allows you to add 2-6 degrees of more timing in that area making more power under the curve

When you run closed loop its either 14.7 or PE, no inbetween.
Phil

1fstGM

iTrader: (13)

Totally off topic, but when interfacing the MPVI Pro with the LM1 all you use is two wires from the Lm1 right (one ground and one analog input)? So from there where can you see the readings? I am a newbiew trying to learn how to tune this dame car!

Also do you guys think it is neccesary to put my IAC back on? I will be using a 105mm Accufab and I know there is some modifications that need to be done to run it. How will tunning be with and without it?

Will my MAP readings get thrown off if I T off my sensor from the brake boster line in the back of the intake (BECK) or is the pressure pretty constant through out the system?

Phil99vette

iTrader: (11)

I just use the one signal wire from the LM1. I log a startup file with the car not running and record the LM1 and the HPT. I download the software and compare. If the LM1 is higher than HPT or vice versa I correct until the HPT 100% matches the LM1. Usually there is a .3 difference or so.

eb02z06

iTrader: (18)

I'm with you Phil-I'm starting to like Open Loop more and more-it makes for IMHO a much nicer driving car with big cams or a big power adder!

RUTAN TA

I am running OLSD also with a big cam 347 and love the drivability.

BTW im @15.0 cruising and getting 28 hwy(6-spd)

Phil99vette

iTrader: (11)

What do you consider a big cam?

YellowToy/A

iTrader: (1)

I will bet that the LM1 is off. It may be a ground thing. You can check it out with an ohm meter. The factory O2 will switch at 14.6. Do you see the factory one swith up and down?

RUTAN TA

242/252 610/598 112 considering its a 347cu.in