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Afm Volts Reading

RB SANDY

By RB SANDY,
in Engines & Forced Induction

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paulr33 Grand Master

paulr33

Posted
Posted

it is not fuel cut, it is excess airflow protection. it retards the timing and richens itself up to protect itself. it is not a fixed value, i believe it is a ramp table based around rpm.

that is you may not hit it at 3.8 volts at 5500rpm but you may hit it at 3.8volts at 2100rpm. its scales based on RPM.

you are best off getting a piggyback to work around it or a remap or standalone ecu

  • 11 months later...
Hotwire Veteran

Hotwire

Posted
Posted

Sorry to dig up an old thread.

I just got consult onto my car today, and in monitoring the values, at full throttle I noticed my AFM was reading about 4.7V!! I know the car is running stock boost, and therefore am amazed at the volts seeing the posts above. During this run the O2 sensor also showed a steady 0.9V (fluctuates from 0.3-0.7 during normal running) indicating it was very rich during this run. Cany anyone help as to why this might be?

See the attached image for the Revs, Timing and AFM for a full throttle run.

Cheers

post-13651-1182603276_thumb.jpg

Tangles Grand Master

Tangles

Posted
Posted

old worn out afm perhaps, on its last legs? maybe it could do with a good clean out with brake cleaner, even a quick re-solder of the internals ? I had "issues" (according to my previous tuner") at 140awkw...... had to get a z32 afm, well was advised to as they said the afm was maxxing out at 11psi on stnd turbo. car was in a low state of tune (mod wise) back then too.

weird, but Im glad I have the z32afm anyhow.

Hotwire Veteran

Hotwire

Posted
Posted

What about the timing on the curves? At full revs, it seems to pull timing back to about 30 deg, is that normal too?

I would have thought for a stock boosted car, 4.7 AFM Volts and the reduction in timing may be what is indicating its rich. I could understand these sorts of figures if I was running 10-12 psi, but its only stock 7psi?!

Any other ideas what to look for as for reasons for running rich?

Cheers

NewKleer Mentor

NewKleer

Posted
Posted

0.9v means nothing more than "richer than 14.7:1". dont assume 0.9v must be "xx AFR". ie, dont use that value to assume you must be running "too rich"

use the fact uve got a stock ecu without a piggyback to infer your running rich, cause thats what the stock ecu does!

nothing really out of the ordinary there i dont think

Hotwire Veteran

Hotwire

Posted
Posted (edited)

So is it correct in saying that the stock ECU will almost always go into Rich And Retardation (as mentioned above by RB Sandy) as the AFM volts go high? I presumed this is what is happening as it drops the timin back to 30 deg. BTDC?

Oh yeh, temp is 70-75 deg whole time during this testing.

Edited by Hotwire
Cubes Grand Master

Cubes

Posted
Posted

I'm unsure about the stock ecu but within the pfc engine temps less than 80degree's see fuel correction. That meaning richer.

I would assume the stock ecu is the same as the pfc's internal values closely represent the values within the stock ecu rom dumps *from what I've seen of the r32 anyway*

BUT regardless.... If your o2 sensor is in good nick it should start pulling the afr up on cruise to stoich within a km or two of driving even with the coolant temps being low.

I think your reading the logs incorrectly. At full throttle; ignition timing is around 30 degree's. It only shows a spike of 50 odd degree's because your going from no throttle to full throttle as you change gear.

According to your log there's no retard occuring. Injection ms will show if the ecu is dumping in more fuel.

But yer.. from what I can see there's definitely no retard occuring.

70-75degree's is quite cool. How long does it take to come up to temp when you first start the car and instantly drive it? i.e no warm up.

Using a genuine thermostat it should come up to 80degree's+ operating temp within 2-3km's, or within a 5 minutes absolute max.

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