a/f doesn't register at WOT, why?

[kuvasz]

i'm trying to dial in the gems controller with an aem a/f gauge and i'm having a heck of a time. last week i had it so i could run 12.2-12.5 down the track at half throttle and playing with the gas and the gauge would read 12.2 the whole time. now, when i come off the line it would read until 11.8 WOT for 200ft and then the gauge would only read the 3 bars and the little light above the digitak read out would be over at the 17 on the dial. we could get the gauge to read once or twice this weekend at 11.8-11.9 down the whole track but when we tried to adjust .5 on the gems controller it did the same 3 bars thing again running WOT. what the heck is going on?

i run 10lbs of boost on 118 klotz race gas with stock fuel pump. mpi said the fuel pump can handle 10lbs of boost but what about the gas? if anyone has any ideas i'd appreciate it.

 

[Accentstripe1]

Gauge

I had the samething happen when I was dialing in my fuel pressure on my impulse turbo. I was told that the three lines across the gauge is most likely due to a miss fire. I changed the plugs and gapped them to impulse specs. Haven't seen those lines on my af gauge again. Might want to check also your vacuum lines and make sure your wiring is good. If you do a search on YouTube, there is a step by step process in checking your af probe is still good.

 

[Omega_5]

Three bars on an AEM means either out of range, or a problem with the sensor.

If the analog output is showing 17 on the datalogger, I'm going to lean more to it being a sensor problem.
How long have you been running that sensor on race gas? Many additives in race fuels poison wideband sensors very quick. It could be time for a replacement.

 

[kuvasz]

i got it used when i bought the used mpi. i've only had it two weeks but i don't know how long the other guy had it. thx, i'll try that first.

 

[kuvasz]

thx guys, the video that's shown on you tube is exactly what my gauge is doing to me. i'm going to pull it out and test it today to see if it does the same thing as the video.

 

[nate007]

Also be sure you have full power going to the sensor. Widebands all need full 12v to preheat themselves and operate properly. If you have it tied onto another circuit you could be getting a weaker current to the sensor when the motor is using more power at WOT. Just make sure the 12v sw power is a good source. I had an Innovate gauge doing the same thing and I put my gauges on a relay directly to the battery and havent had a problem since.
As far as the gas, you're better off running straight race fuel if you can find it and afford to feed it! Although MPI recommends a 50/50 mix, race/pump, pump fuel KILLS race gas. an even mix of 110 and 91 has been said to yeild approx a 95 octane, so in my opinion, it's not worth the money to mix. Either run straight race gas at the expense of your sensor, or use a good additive like Torco which will deliver about the same results.

 

[kinger]

Sounds like a sensor issue but once you get that working, watch your WOT, my stock fuel pump could not keep up even though everyone said it would. Threw on a walboro 255 and holds perfect AFR now.

 

[TurboTime]

X2 kinger. You will need an aftermarket fuel pump if your going to run 10lbs. The stock fuel pump will not keep up, 8lbs is about the limit..
You know the saying: TO LEAN TO BAD: Kabom

 

[machzrobbie]

Stock fuel pump will not suplly enough fuel for 10 pounds - been there done that

 

[kuvasz]

hey guys,

i changed the sensor to a ngk ntk 24320, i tt ernie and mauri(thx guys) and presto the machine is running. i'd say like a top but i have to dial in the gems controller again. now i have the new sensor it's running the machine at 10.9 at idle, lol.

i'd like to say thx for all the advice everyone has given me here too.

 

[kinger]

When you guys installed your in tank fuel pumps did you figure out a way to suck up all the gas? Right now I have about 1.5 gallons left when it runs out, I got some intake fuel hose and will probably make a pickup just looking for ideas. Thanks

 

[TurboTime]

hey guys,

i changed the sensor to a ngk ntk 24320, i tt ernie and mauri(thx guys) and presto the machine is running. i'd say like a top but i have to dial in the gems controller again. now i have the new sensor it's running the machine at 10.9 at idle, lol.

i'd like to say thx for all the advice everyone has given me here too.

A little rich at idle, you will want to reduce the fuel amount to reach high 12s or low 13s for idle.. good luck