phill 147

hi all i have purchased a cable and using ecu explorer for my00 subaru i am looking at live data what should the air flow sensor voltage be at whilst driving and what should timing degrees be cheers i will update with results for further help

Splitpin

Depends entirely how much air is being pulled into the engine, which in turn depends on how hard you're treading on the throttle, and how much boost you're running.

To give you a general idea, you should see 1.02 volts with the engine off, around 1.2-1.34 volts at normal hot idle.

As I said on-load readings vary hugely according to engine speed and boost, and whether or not you're running the standard turbo and induction tract.

If you are concerned about your airflow sensor's health, the most important thing to look for is downward "spikes" in the voltage under boost. If you save the monitor output to a log file and do a WOT run from low to high engine speed, you should be looking for a smooth increase in sensor voltage up until the point you lift off.

For example

2.00 2.04 2.1 2.12 2.1 2.14 2.18 2.2 2.24 2.26 2.28 ...is the sort of climb you should be seeing - a smooth upward trend with no more than a handful of hundredths of a volt either side of the trend

What you don't want to see is something like this:

2.00 2.04 1.2 1.2 1.34 2.14 2.18 2.2 2.24 1.80 2.28

If the voltage suddenly drops away fron the trend by a large margin, and the comes back like that (without you lifting off the throttle, of course) it points to a vibration damaged sensor.

It should be whatever the ECU thinks is the right number. The figure you'll see on your log varies all the time. Timing is looked up from a 3D map which uses engine speed and load as inputs, and is then further modified according to the ignition advance multiplier and amount of knock sensor activity among other factors.

dynamix

iTrader: (3)

Could also be compressor surge or overboost being reigned back and then re-added.

Smooth progression is the key as Splitpin says.

Splitpin

That's true, but if it was you'd see the complimentary changes in the air pressure and wastegate duty parameters, and I was trying to introduce Phill to the subject of logging without blinding him with too much science up front. If he comes back asking questions about his log, that's the point to add further info.

On a standard-ish MY99-00 - especially an MY00 UK car (with the AE802 ECU), the sawtooth MAF input I described is more likely to be sensorfook than anything else.

dynamix

iTrader: (3)

phill 147

here is my logger data does any of this look wrong cheers

front o2 sensor min 0v max 0.92v
fuel injector 1 pulse width min 0.51 max 15.36 ms
ignition timing current 12 max 43 degrees
injector duty cycle max 39.02%
manifold relative pressure min -11.32 max 11.17 psi
mass air flow voltage min 0.98 max 3.62 v
primary wastegate duty cycle max 90.98%
throttle sensor voltage min 0.36 max 2.04v

Splitpin

We can tell you a few things, but we can't tell you whether it looks "right" or "wrong" without being sat in the car with you at the time these figures were made and seeing what happens as the car is being driven. You can only learn a limited amount from minima and maxima.

I would guess from looking at these numbers that you've just been for a gentle toot around the block that includes a couple of part-throttle squirts onto boost.

Nothing unexpected there, typical expected maximum for a healthy narrowband sensor and a rich UK car fuel map.

Again nothing out of the ordinary there, although it suggests that you didn't go very high up the rev range with any flat out running. IDC on a UK map on a flat out run should be much higher than that - probably in excess of 70% higher up the rev range.

Again nothing much to see here, although you presumably weren't driving absolutely flat out at any point. -.77bar vacuum is in the ballpark on liftoff, 0.77bar peak boost suggests you weren't genuinely flat out at any point (or if you were, it's not hitting boost target).

Point of semi-interest with the 0.98 minimum. If you've logged this run it would be worth you looking through and seeing exactly when and how often this 0.98v value occurred. If it's when the engine is off I would be paying a little more attention to the MAF output to ensure consistency. If it's on lift-off it suggests you have a small amount of reverse flow coming back through the inlet tract. If it's at a point where you're just driving along normally, and it suddenly drops down to 0.98 and back to where it was, without you seeing a throttle lift in the same row of your log, then that's a drop-out, and not good.

The 3.62 max voltage again suggests you weren't trying very hard, although as mentioned earlier the key indicator to look for is the consistency of the airflow sensor's voltage output. You will only see this by logging and either manually scrolling through the numbers, or graphing them and looking for "spikes" that don't correspond with throttle lifts, air pressure changes or other corroborating factors.

Again to be expected on a standard two port UK map.

This again suggests you weren't at WOT at any point - so if you did put your foot to the floor at any point, it's worth looking at. You should see around 0.50 of a volt from the TPS at idle and around 4.3 volts at WOT (and if you look at the sensor itself, the screw holes are slotted to allow a little adjustment).

You can check the sensor with the engine off - slowly press the throttle down from idle all the way to WOT and you should see the TPS voltage continually climbing. If it suddenly drops down, and then comes back, as with the MAF this suggests a damaged sensor.

phill 147

cheers splitpin for advice