Hi guys,

Got a weird one hoping someone has an idea about. I have a PFC with a bunch of mods but I've tuned them one-by-one and know all specs are correct. With the stock AFM on, the feedback is spot-on and electrical load has no big effect on AFR. I've now installed a Z32 AFM and I've got the correct settings and with no electrical load everything is spot on and AFR is exactly as it should be. But when I add some electrical load to the mix, the AFRs go rich eg if I'm stopped and idle is at 14.7, if I turn in the headlights, AFR will go to about 13.5 - add aircon and the radiator fans and it'll be about 10.5! As a direct test I've got the attached screenshots taken within 5 seconds of each other - both at idle - one with headlights off and other with headlights on - headlights off is at 14.7 afr - headlights on is at about 13.5 afr - all sensors report the same, the only thing that changes is the MAF voltage reading - I can understand if the voltage feedback went down when there was electrical load, but the voltage from the MAF actually goes up? I've attached the no electrical load image to this post

Any info or ideas u can give me would be awesome

Thanks heaps
Rich

Attached Thumbnails

 

Here's the image with the headlights on - all feedback is the same, just MAF voltage is higher

Rich

Attached Thumbnails

 

when you add any load at idle the idle air motor opens to maintain the idle speed - this increases the airflow at the MAF which = slightly higher MAF output voltage.

you only have a .02 of a volt change anyway.......

Have you scaled the MAF airflow curve correctly?
Have you done the 30 minute PFC idle learn with the new MAF in place?
Have you watched the map tracer in FC-edit to see what fuel cell it is dropping into when the electrical load is applied at idle?

I'd say you have an incorrectly mapped cell, check the cells around where the pfc is sitting at idle with no load - apply the load & see which cells it's floating between (it should step down a cell or 2 on the load axis) change the fuel correction for this cell and it's neighbors to maintain your idle AFR's - these cells won't effect anything else in your map.

P.S I run my idle in the 16-17:1 range and 15-16:1 at cruise (14:7 at transition to boost (0 psi) and 11.5 at peak torque/boost.

__________________
[CENTER][SIGPIC][/SIGPIC][/CENTER]
[CENTER][COLOR=#ff0000]Built Ej207: Semi-closed RA Cases - Wiseco Forgies - Manley rods - BC 272 cams - GDA Heads - billet f/whl - Vi-pec - WbO2 - 800cc Yellow tops - TD05-20G - 409Hp ath @ 1.75bar on E85[/COLOR][/CENTER]

Hi Rossco,

Thanks for the reply mate.

I was thinking along those lines also but i dont think thats the issue for two reasons :

1) with no electrical load, the entire map is pretty close to perfect including idle - if i set the entire map to 11.5 and go for a squirt, i log 11.4-6 AFRs everywhere.
2) The issue is happening over the entrie map, not just at idle eg if i set the map to 14.7 below boost and 11.5 above, turn on aircon and my lights, ill be getting about 13AFR below boost and pegging about 10 on boost.

Basically because i made sure everything was perfect before installing the MAF, and then confirmed that everything was perfect after installing the MAF (with no accessories - using the default PFC VG30 settings) then im pretty confident the settings are correct.

I definatly agree that the MAF is at fault, but i dont think its the scaling because i rescale for accessories on, ill throw the non-accessory map off. At this point im wondering if it an issue with the wiring? Ive wired it up according to this

Fitting A Z32 Afm To 99/00wrx - Rexnet Subaru Forums

....but maybe the issue is with the wiring like the ground needs to go somewhere else instead of the chassis, or maybe the +12v needs to go straight to the bettery or through a relay or something?

Ive got a genuine Bosch Nissan Z32 AFM and also using the Tomei MAF plug. Also my car is a MY98 but has a phase 2.

PS. i thought you sold your beast? Can you please post your INJ map so i can have a look at the cruise areas?

Thanks again
Rich

hi guys,

Just a quick update in case someone is looking at this issue in the future. Managed to get it sorted - turned out to be a ground loop. According to the link above, one ground goes to the chassis and the other goes to to ECU ground. I found this link :

DIY Z32 AFM wiring Diagram - Rexnet Subaru Forums

...and according to this, the two grounds are connected inside the AFM and therefore it is creating a ground loop between the 2 grounds. Anyways i just cut the chassis ground and connected both the grounds to the ECU Ground and its now working perfectly.

hope it helps someone

Rich