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Discussion Starter · #1 ·
I will be moving to a PFC soon to support 600 bhp approx.

To do this I need to upgrade the AFM's rather than go the classic route of using 2nd hand tired Z32 AFMs.

If I use current DENSO current MAFs (which I can buy new cheaply) and I have the airflow to voltage conversion data for and will support 450 bhp each, can I enter my own voltage to airflow table?
 

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Not directly, no. If you do a search on here for `emry` (I think) he posted a graph of Z32, Nismo and std AFM voltage to airflow (kg/hr).

Take the Z32 airflow curve and compare it to the Denso curve you have (point-by-point % offset will do). Now take the PFC MAF calibration for the Z32 and factor it based on the % calculated above. This should get you close. ALternatively just play with the MAF calibration until the fuelling on the base map (or you mapped version?) looks sensible.
 

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Get a % flow difference at each voltage between Z32 (based on graph above) and your denso part.

The select the Z32 MAF in the PFC.

Then apply your %flow correction to the 32point Z32 MAF calibration in the PFC. This does assume you have access to Datalogit, hand controller can`t adjust the 32-point cal.

If you don`t have datalogit, you could do as above and enter the % correction in the 8-box table, but I don`t think this will give the required change accross the operating range.......
 

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David,

As long as you are re-mapping your car, it doesn't matter what voltage profile you have on your air flow meters.

When you are mapping the car, the ECU will see a voltage coming from the AFM and you will adjust the map point to provide a fuel level that matches the voltage coming from your AFM.

The AFM selection system in the power FC is there to help you keep a similar map when changing AFM's but should not be relied upon to be accurate, especially on a big HP engine.
 

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Discussion Starter · #7 ·
David,

As long as you are re-mapping your car, it doesn't matter what voltage profile you have on your air flow meters.

When you are mapping the car, the ECU will see a voltage coming from the AFM and you will adjust the map point to provide a fuel level that matches the voltage coming from your AFM.

The AFM selection system in the power FC is there to help you keep a similar map when changing AFM's but should not be relied upon to be accurate, especially on a big HP engine.
I understand it doesnt matter, but I would prefer it to measure an actual unit of flow if possible.

Can you shift breakpoints used for main fuel and ignition using the PFC?
 

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Yes brake points scaleable, again only with the datalogit (or apexi software).

Hugh - thats true, but the charateristic of the curve has to be failry close to the sensor your using otherwise the load calculation can run into problems with resolution.
 

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My feeling is that when you have a sophisticated tool in datalogit, from which you can accurately calibrate your airflow curves for your particular setup, why would you not use it?

When I change my commanded AFR from 11.5 to 12 for example, I want this to be mirrored in my measure AFR. I've found that I can usually get to within 0.1-0.2 AFR using the 8 point scale, unless there are problems with AFM offsets caused usually by cold air feeds directly onto the filters.
 

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so... you can use stock AFMs when pushing 450++ hp with an Apexi PFC if you rescale them?
 

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Yes brake points scaleable, again only with the datalogit (or apexi software).

Hugh - thats true, but the charateristic of the curve has to be failry close to the sensor your using otherwise the load calculation can run into problems with resolution.
All the airflow meters have a 0 to 5 volt output and will saturate slowly, so if you are using the full output of your AFM, you should make certain that the response before saturation is reasonable.

Having said the above, all the standard AFM maps will have a similar profile.

When you select a different AFM with the hand controller or software, you are not changing the voltage input, but extending the load site range on the fuel and ignition maps.

The above maps on the Power FC are 20 by 20 which means that all you have achieved is a shift in scale. so whatever AFM you select will make no difference if you are re-mapping the car.

I do agree that the system of selecting a known AFM that still keeps your car in relative tune when changing spec is a great idea.

In this instance David is swapping to an unknown AFM and is therefore starting his mapping from scratch.

My suggestion is to plug in your ECU select any AFM and start playing about with an injector % that will make your car idle properly.

After that you can start mapping. This then opens another can of worms that has been covered a 100 times on here before.

Cheers

Hugh
 
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