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PFC datalogit

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Hello everyone, just starting to learn how pfc datalogit works. Currently i am tuning a B18C with bolts on. My problem is that there is an INJ MAP and 2 Base VT0 -VT1

In my understanding INJ MAP is the target of AF?

VT0 is the base map when VTEC is OFF

VT1 is the base map when VTEC is ON

So how do i tune the fuel ? Will i set my targets on the INJ MAP and tune from there and on the 2 base maps. Or is there a better way to do it?

Also setting the correct injector dead times lead to poor idle with afr at 20:1 . Using the stock injector dead times works just fine. What's wrong here? Should i aim 14.7 with the new injector times to correct my idle? ( Aftermarket injectors are RC engineering 550 cc).

Regards, Fotis

Does anybody knows the formula to calculate Injector lag (ms) vs Bat(V) ?

G'day Fotis.

There isn't a forumla to calculate the injector lag, or deadtime vs battery voltage, it needs to be measured, or determined by testing. Can you post up a screenshot of the settings you've got in there?

My understanding of tuning the PFC's with a Datalogit is that you want to enter your desired lambda values into the InjMap, and then adjust the BaseMap till the measured lambda matches the desired lambda in the InjMap. Once that is done, you should be able to adjust the desired lambda in the InjMap and the measured lambda should track it nicely. This does require that the rest of the settings (deadtimes, etc) are correct though.

Hi Fotis,

The base VT0 and VT1 maps are supposed to be the injector pulsewidth required for lambda=1.0 (in theory). Then the INJ map is a target equivalence ratio (inverse of lambda, where higher number is more enriched) applied on top of that. The INJ map can also be put into Air fuel ratio display mode, but it's basically the same thing. In the case of a Honda (as far as I remember, as most of my experience is with Rx-7's and S14 Syliva SR20DET), the same target equivalence ratio is applied to both VTEC ON and OFF.

You can try to adjust the base VT0 and VT1 maps to achieve the target AFR specified in the INJ map. However there is an alternative method, and it's up to you to decide what you want to do. That method is to "zero out" the INJ map by using the "recalc base" function in FC Edit. Then the VT0 and VT1 maps are basically injection pulsewidth lookup tables (before correction is applied). This is my recommended method but again you can try Zac's method too. This method allows control over non VTEC and VTEC separately, and because you don't have to deal with limits in the INJ map. Just recalc base and adjust each table individually.

You will want to turn off O2 feedback for this to work, or you will have to do some manipulations to the table which I can get into later. The O2 feedback in the power FC really isn't very good. If you want closed loop narrowband feedback, use a modified stock ECU like a Hondata S300.

As for the injector settings, I recommend you put in the injector data and just manipulate the VT0 settings to get your AFR ok, and also be mindful of the air temperature compensation affecting it.

Thanks guys, but my injector settings aren't working for me...

I entered the times that were given from Rc engineering and the car won't idle ( AFR at 20:1) i try increase the values in VT0 and nothing changes to the Air fuel.

Using the Stock dead times that are given from PFC works fine? Can't understand why tho.

The Power FC is a really old ECU. It originally came out about 20 years ago and Apex'i hasn't updated it much. It comes from an era where bigger/higher flowing injectors always had longer deadtimes than smaller injectors. The injectors you are adding are several generations more advanced, but it may not work out if you actually enter the correct times.

If you open up the Power FC manual that comes from Apex'i, they don't mention changing the stock deadtime table (which you can't change on the Commander anyway) and just have you offset the injector pulse based on the difference between 14V dead times between the old and new injector. See attached screenshot; note that it is for the Rx-7, which has staged injection.

Therefore I recommend you keep the deadtime table the same as you have done and just go from there. It's a workaround for an old ECU.

Attached Files

Thanks mate finally i understand how PFC inj time works hehehe

Changing from small to larger injectors i so that many people will multiply the base maps with % the will find after dividing the old inj/new inj is that correct and should i do it?

You can try it, but typically it's not that easy.

Thanks man.

Having a small problem. Went from 240 cc stock injectors to 550 cc. The problem is that with the stock dead time the map would need a trim but in my case the map needs fuel

Maybe a fuel pressure problem?

Per Apex'i 's basic instructions I posted, Set the injectors to 550CC and ~44% because 240/550 is .436 . Then bump up the pulsewidth adder (dead time correction, not the table itself) a bit . Try adding until it idles, so maybe -.02 to 0.05 .

Post screenshots of your stock settings and your changed settings.

I did put it 43.6 but the map needs enrichment using 62.5% runs exactly at 14.7 at idle . Using the 62.5% means my injector flow 380 cc that means i lose 170cc .Could be the fuel pressure?

Attached Files

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