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Afm Volts Reading

RB SANDY

By RB SANDY,
in Engines & Forced Induction

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Hotwire Veteran

Hotwire

Posted
Posted

Cubes,

Thanks for the excellent explanation. I wasn't too sure about the timing, but just noticed that it seemed less at full throttle. It makes sense what you are saying now.

With the injector ms, what would i look for? I have attached the plot of the injectors, and seems they aren't making a big jump either so I would say no R&R, I just didnt really understand what it was before :(

As for the temp, it gets to about 70 within about 3-4 mins of driving. In the warmer weather however it did go up the guage more (didnt have consult then) and would guess it was more about the 80-85 mark I think. This is leading me to think the thermostat is a rather cold one. It definately has a thermostat, as when cold you can feel no flow (pressure) in the top hose, but once warm there is definately flow (and can see it with the cap off).

For general running the O2 sensor fluctuates a lot, so I'm fairly certain that is operating as expected.

post-13651-1182733787_thumb.jpg

Hotwire Veteran

Hotwire

Posted
Posted (edited)

Have done some searching regarding Resistor in line with the AFM circuit.

Now the argument I have read is that you won't get any more "flow" out the the AFM if you are maxing it out, and Z32 is your best bet. I can sort of understand this, but I fail to see why this wouldn't help with the rich running of the stock ECU if it's not maxing out? IF it puts out lower volts accross the whole range, then should it not think "less airflow, less fuel"?? ie. in my case, the AFM is 4.7V at max load, and obviously fuelling accordingly. If the volts were dropped to around 4.0 or similar (with a check on a dyno) surely this would help?

If I am missing something, can someone please explain it to me?

Edited by Hotwire
MrStabby Grand Master

MrStabby

Posted
Posted

I agree that putting a resistor in will make it run leaner, but dont forget what Adriano said earlier - the AFM's response is not linear, so if you use a resistor (which is linear) you will stuff up the signal in the rest of the curve to "fix" it in the part you're looking at. That's why you use a piggy back instead. Its a clever resistor that tweaks the signal by different amounts for different inputs.

BTW - i'm guessing, hopefully someone that knows can confirm/deny!

NewKleer Mentor

NewKleer

Posted
Posted

pretty much what i would have said - resistor alters AFM voltage linearly, but the AIR->Voltage relationship is not linear. youd probably mess up your idle, amongst other things (ie making certain regions too lean and risking engine damage, detonation, etc).

btw, is there any form of adjustment screw on the AFM?

Hotwire Veteran

Hotwire

Posted
Posted

I know there used to be an adjustment screw on my R31 AFM (bosch unit) however Im not sure about the R33 AFM. Would be interesting to know if there is an adjustment pot, but I probably wouldn't mess with it myself. The car is going to Boostworx in a couple of weeks for a new water pump. I'll speak to Shaun and get him to do what he can (not that i'm expecting much)

  • 1 month later...
AdamsR33 Mentor

AdamsR33

Posted
Posted

Old thread but didn't want to start another one about damn AFM's.

My R33 stock AFM went to 5.06v on 8-9 psi stock turbo, PFC. Is this okay? does idle at 1.2v

Test was done in 1st and 2nd gear only to 6500rpm.

  • 2 months later...
bumble_bee Rising Star

bumble_bee

Posted
Posted

yeah, i got an apexi neo fitted, found out on my second tune that my o2 sensor died..

and my second tune was only two days after my first tune =(

coz a day after my first tune, i drove to my mates den after i went to leave, can i couldnt pass 2500rpms..so i had to reset my afc/apexi neo to drive...

after my first tune..my car felt so good!used no fuel..

second tune was screwed..coz they had to tune it witout the 02 sensor being connected..

so after that i just chug'd fuel!

got a new o2 sensor...

but still didnt improve dat much..

found out the second tune..done by a different place..

tune my air map settings from lik +8% to +12%..on some high throttle rpms..

so i adjusted these settings

runs so good now, i get lik 430k's outa my 50L tank..lol

could run a bit betta, but good other things to fix..

wats ur a/f read at idle?just curious...

RBwhatever Veteran

RBwhatever

Posted
Posted
Old thread but didn't want to start another one about damn AFM's.

My R33 stock AFM went to 5.06v on 8-9 psi stock turbo, PFC. Is this okay? does idle at 1.2v

Test was done in 1st and 2nd gear only to 6500rpm.

Nothing to worry about. RB25 AFM maxes out at 5.1V

I'm still on the stock turbo running 12psi and it only just hits over 5000mv.

Thats however 700m above sea level where the air is thinner. Take it down the hill to sea level and it'll hit 5110mv no worries.

At idle its about the same as yours..1100mv-1200mv.

RBwhatever Veteran

RBwhatever

Posted
Posted (edited)
ah..huh??

na, im going off wat the apexi neo says..its not in volts...

its air flow %..

The apexi neo is a AFM signal bender. It gets the air flow signal and warps it so the stock ecu says "oh that looks ok".

The Power FC reads air flow as it is, which is in mV. It doesn't bend the signal because it doesn't have to trick anything.

I haven't seen a neo before but maybe those %'s your seeing is air flow correction figures.

Edited by KeyMaker
bumble_bee Rising Star

bumble_bee

Posted
Posted (edited)
The apexi neo is a AFM signal bender. It gets the air flow signal and warps it so the stock ecu says "oh that looks ok".

The Power FC reads air flow as it is, which is in mV. It doesn't bend the signal because it doesn't have to trick anything.

I haven't seen a neo before but maybe those %'s your seeing is air flow correction figures.

no its a got a "correction %" view/display aswell...on idle thats at -12%..

and my idle is perfect! no jumps or hunts..lol

and i got a atmo bov too..

na, its def. A/F %, which is air flow %..so on idle thats reads 2.5-2.6%..

but it doesnt display A/F voltage...

it does display voltage thou, but i believe this only battery volts..coz its like always round 13.4-14volts

Edited by bumble_bee

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