Topic: Map Adjuster Voltage

[dwtaylorpdx]

The dealer drug a little black box with a Chrysler Logo on it and plugged it into teh 2" square connector that dangles near the driver hood hinge(94) and that little box displayed pretty much the same stuff I've seen on OBDII. Mechanic was cool and let me fiddle.

Dave

[sharpxmen]

Once you push the the fuel trim past where it cannot adjust it self, it's essentially in open loop. It can only adjust it self so much. We had a problem with CNG engines where the fuel map was not quite generous enough, forced us pretty much to change more injectors than sparkplugs on them things. They would just run to lean after a couple of weeks to a month. Finally found some injectors that let a bit more natural gas through and pretty much solved our problem. We had the regulators cranked up as high as was safe to do so to try and get a bit more fuel in them. Seems to me fiddling with the resistance of the Coolant and or Air intake temp sensors is easier to give the engine a little more fuel, Used to work wonders for Cadillac Sevilles.

not sure about coolant but wouldn't AIT be ruled by the same closed loop O2 feedback - it won't change the output of the oxygen sensor though, so wouldn't that only work for open loop?

as far as pushing a bunch of fuel i can't see how that would work at all ranges though, if your PCM can't adjust the duty cycle low enough i would guess that the engine would not run properly (might as well disconnect the o2 sensor, would run on a set fuel map which would be better i think) - once you're in open loop would be too rich in this case (too much fuel in closed loop)

[aw12345]

Basically all of it is mood when the engine runs right, now if it needs more fuel, then anything that tricks the ecm to supply a bit more fuel will work, Making the pcm think the engine is fairly cold will supply a bit more fuel. a lot of the aftermarket chips do something similar, they add a bit of advacce and add a bit of fuel. To me on a fairly stock engine buying an adjustable map sensor for 200 bucks is a waste of money, you can achieve the same with a couple of resistors in the CTS circuit. Now when it's supercharged or Turbo charged that is an entirely different thing

[sharpxmen]

Basically all of it is mood when the engine runs right, now if it needs more fuel, then anything that tricks the ecm to supply a bit more fuel will work, Making the pcm think the engine is fairly cold will supply a bit more fuel. a lot of the aftermarket chips do something similar, they add a bit of advacce and add a bit of fuel. To me on a fairly stock engine buying an adjustable map sensor for 200 bucks is a waste of money, you can achieve the same with a couple of resistors in the CTS circuit. Now when it's supercharged or Turbo charged that is an entirely different thing

x2
there's no reason to use a programmable map sensor for a stock engine.

not sure if that trick with the CTS would work in closed loop, if it does then it's a cheap way to get a bit more power although would hurt your mpg whereas if you only focus on making it a bit richer in open loop you can still get the same mpg when in closed loop.

[aw12345]

Well a 4 banger on the highway is pretty much in open loop all the time isn't it, lol pedal to the metal and going nowhere. Full throttle is open loop.

[dwtaylorpdx]

Individual engines have personalities as well, for instance my 94 ran super rich from day 1, once I built teh motor it started actually running in the right AFR range, and I've changed out all the sensors a couple times chasing the issue, finally decided its a goofy ECU.

Dave

[chrisfranklin]

Art, Sharp, in my case, I would have spent a bunch of time building the DIY MAP adjuster unit that I could have spent working or doing something else worth more than the dough I paid for the built adjuster unit.  

Is there a real need for a Map adjuster on a 4banger without forced-induction or other big air flow mods over and above a 62mm TB, after-market intake, and cat-back?  I'd guess you probably don't absolutely have to do a Map Adjuster, whether DIY or Turbo City or something else.  I might see if I can grind out the intake opening before too long and headers are always a possibility

But I wouldn't mind getting an AF read-out and then determining what voltage -- if any -- above oem is worth setting on the adjuster in my case as is  

[chrisfranklin]

With the 02 sensor apparently dialing back any change in a rich incoming mixture below WOT, it sounds like WOT (or a range pretty close to it -- 80% throttle to WOT) is the only place where a map adjuster is going to be worth anything on the 4banger (and 4.0).  

Or is it just WOT that gets you in the open loop where the O2 sensor can't interfere?  

[sharpxmen]

Art, Sharp, in my case, I would have spent a bunch of time building the DIY MAP adjuster unit that I could have spent working or doing something else worth more than the dough I paid for the built adjuster unit.  

i think both Art and I were talking about programmable MAP sensors (the kind Split Second makes) not the voltage adjuster (that's the one that cost you $200 but it is cheaper now).

what you installed would go both ways, getting you in open loop a bit sooner and giving a bit more fuel - i can't remember the exact behavior where the PCM is switching from closed loop to open loop but on the hwy would probably be when you go wot or close to that and during acceleration until the engine settles to a cruising rpm if you're below wot. Same goes for when you do city driving, it will go open loop when you start from a stop light and during first moments after a shift in gears, once it balances itself (the throttle opening matches the rpm and speed) would go in closed loop - you can easily monitor that with an LED based AFR gauge, it will cycle quickly back and forth in closed loop and will shift towards the rich side when in open loop - you can probably do that with a scanner as well but i never used one, Art might have so he can tell you more about that probably