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View Full Version : 3 bar MAP - Wont work...


Dave
10-14-2009, 02:46 PM
I seem to have an issue with our MAP sensor circuit...

1990 Caravan 2.5 Turbo
Factory electronics

Here's the story.

Last year, bought a FWD Performance Stage 5 cal, installed a GM 3 bar MAP... as soon as I got into the throttle it had some real bad lean tip-in (about 17.5+:1) it continued to stay at ~13.5:1 in boost at around 14psi with 55psi fuel pressure (with vac line off). Okay fine, fast forward to this year... Bubba burnt us the exact same cal he used at first with his vehicle. Same symptoms occurr. I even tried a MSD 3 bar MAP with the same results.

It runs great with the factory ECU and factory 2 bar MAP. The head connector is soldered to the factory harness and the pin terminal head is modifed to accept the 3 bar MAP plug in.

Perhaps the injector driver in the ECU is bogus? This is the one and only SBEC we have that is socketed. I'm thinking something is wrong inside of it.

Any other ideas? I would like to take it to the track this weekend if it doesn't snow. Any help would be great.

Thanks
Xtrempickup
10-14-2009, 07:54 PM
wouldnt surprise me if that cal is set up for a 2 bar not a 3bar like it was supposed to be
Dave
10-15-2009, 01:39 AM
wouldnt surprise me if that cal is set up for a 2 bar not a 3bar like it was supposed to be

2 FWD Performance computers were, and 2 from Bubba were supposed to be with the same issues. I think the problem is elsewhere. I even remember opening the file and seeing the 3 bar MAP toggle was selected.
turbovanmanČ
10-15-2009, 02:30 AM
If it works with the factory SBEC, and you have known good 3 bar cals, sounds like your SBEC is fubar.

I have a chipped one for sale, :evil:
Dave
10-15-2009, 10:00 AM
How much?
glhs727
10-15-2009, 10:52 AM
2 FWD Performance computers were, and 2 from Bubba were supposed to be with the same issues. I think the problem is elsewhere. I even remember opening the file and seeing the 3 bar MAP toggle was selected.

If you tried 4 different computers and 4 different cals, sounds like it is not an ecu issue. what kind of voltage readings come from the 3 bar map when you are driving?
turbovanmanČ
10-15-2009, 08:56 PM
If you tried 4 different computers and 4 different cals, sounds like it is not an ecu issue. what kind of voltage readings come from the 3 bar map when you are driving?

Good catch, I thought he said 1 computer and numerous chips.

I agree, sounds like he wired up the MAP wrong.
Dave
10-17-2009, 01:11 AM
My mistake, same scenario though, 2 FWD Perf. computers and 1 additional chip, 2 chips from Bubba. ;)

Either way, while driving it I remember seeing .6V at idle, and 1-1.5V roughly at 0psi.
bakes
10-17-2009, 02:55 AM
check for baro sensor sh1tting the bed ,that problem threw simon for a loop and nearly cost him a motors
turbovanmanČ
10-17-2009, 11:16 AM
My mistake, same scenario though, 2 FWD Perf. computers and 1 additional chip, 2 chips from Bubba. ;)

Either way, while driving it I remember seeing .6V at idle, and 1-1.5V roughly at 0psi.

That's not right, I should check mine but IIRC, it should be 1.5 volts idle and 3 volts at 0.
Dave
10-17-2009, 11:32 AM
That's not right, I should check mine but IIRC, it should be 1.5 volts idle and 3 volts at 0.

Ok, that's going off memory. I'll hook up the DRB II and go for a ride today. I'll report back.
sexygomer
10-17-2009, 02:13 PM
If you tried 4 different computers and 4 different cals, sounds like it is not an ecu issue. what kind of voltage readings come from the 3 bar map when you are driving?


i had that happen too, plugged in standard 2bar ran fine, plugged in 3bar ran like butt....never could find out why, blew the car up b4 i found out. if you figure it out i wanna know :thumb:
Dave
03-27-2010, 01:31 PM
Still haven't quite figured it out... We got tired of fussing with it and bled the MAP sensor. Could only achieve 20psi because I need to tighten the WG arm. However it still appeared to be detonating a tad because of this technique. After every pass there would be more and more coolant on the front of cylinder #1.

I need to figure this out.
Aries_Turbo
03-28-2010, 11:14 PM
just to correct some potential misinfo....

2-bar map sensor will be around 2.5V with the key on and the engine off.

3 bar map will be around 1.6v with the key on and the engine off.

i dont give idle values cause they can be all over the place with cam selection and other stuff.

as for the other problem. dunno... all the sbec pins are tight and making good connection? they have a habit of getting loose and the connector needs to be taken apart and the pin sockets tightened up a bit so they make good connection.

Brian
Dave
03-30-2010, 09:35 PM
just to correct some potential misinfo....

2-bar map sensor will be around 2.5V with the key on and the engine off.

3 bar map will be around 1.6v with the key on and the engine off.

i dont give idle values cause they can be all over the place with cam selection and other stuff.

as for the other problem. dunno... all the sbec pins are tight and making good connection? they have a habit of getting loose and the connector needs to be taken apart and the pin sockets tightened up a bit so they make good connection.

Brian

I'll check 'em out and make sure. Thanks buddy.