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Discussion Starter #1
Continued from here

I was looking at the voltage compensations values for the various injectors and they don't seem to make any sense.

For example a 36 pound injector in the Focus is basicly uncompensated at 14 volts, as you would expect since that is about normal operating voltage - at least for mine. However a 24 pounder in the same car is uncompensated at 11 volts, and a 21 pounder is at its uncompensated value at 15 volts ... is it me or does this seem out in left field?

I don't get how this works if the slope values are correcting for injector size.

In my case I am running 60s with the comp values for 42s. The car runs at about 14.0 volts at the battery sitting idle or when I rev it. At 14 volts there is already a 9% correction taking place.

That in itself is not a big deal, I guess, but the items above to make me wonder about all the other voltage correction data... and how if any of it is not completely accurate, how it may affect driveability at cranking, immediately after, and so forth, perhaps even at WOT or other times when there may be voltage fluctuations.

Am I out in left field here? Or am I on to something?

Is each different size injector manufactured to operate at its rating at a different voltage level (!)?
 

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Discussion Starter #4
OK


I did another start test and at cold crank it showed about 10.0v, then at start up hit about 12.2, then took 7-8 seconds to work back up to ~14.0. This is the time that things go full lean off wideband and it sometimes stalls, so I am pretty sure voltage comp is the problem.

It would be interesting to see what batt voltage does once warm and cruising, then suddenly going WOT... but my POS scanner doesn't show voltage.

Anyhow I also asked for help on MD, and I see I just got a reply from there, Ken was going to check on the values they use so we'll see.... interesting problem though.
 

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Discussion Starter #5
Shoot I see what I did wrong... I had previously clicked "scalars", "fuel injector", and loaded the 60 Lb values file to get the slopes and pulse width, then stopped.

I didn't realize there was also values for non-scalar "fuel injector" within the same file to get the voltage comp values and slope corrections.... damn!

So hopefully the problem will be solved. However, I still don't get why the "normal" operating voltage for the injectors is not the same, with corrections then adding or subtracting from whatever the normal voltage value is supposed to be.
 

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Injector "slope" is a way of expressing the size when graphed. Because the injector takes some period of time to open and close at low pulsewidths it's flow is different.

All of the injector values are determined by real world testing, and there is no "formula" to follow.

Now this is just a guess, but I suspect that say a 24# injector may have flowed a bit more than 24#'s, so the voltage was changed to correct it to 24#'s at any given voltage.
 

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Discussion Starter #8
OK, I am trying the voltage comp values for 60s from MD, but currently can't get the engine to start... but I will.

In the meantime is David Posea still the one to get keys from? I only have like 8 burns left and will probably have them used up in a couple hours.
 

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Discussion Starter #10
Bah, I got a car dead in the water and no more burns left.... half of them go wasted as there is usually an error during verification of the first burn attempt, so I have to do it twice
. I wish the software would give a heads up when you have say 30 burns left instead of 10.

Oh well I'll call SCT direct tomorrow and get a new key.

Good news is I got the car to start again after about 6 reburns overhauling the TF
... it took like 80% in corrections at low air flows from what had previously been right on the money.
 

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So Rod, how are those 60lb injectors working out for ya? I'm almost done with my new turbo setup and will need to go higher than the 42s i have right now. Curious if 60 is the way i should go or if it's too much of a headache.
 

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Discussion Starter #12
The 60s seemed to work fine after getting the voltage comp values squared away. However I never resolved the fuel pressure issue so it is still parked... only drove the Focus one time (to charge the battery) since I got the new Miata about a month ago.
 

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hmm, that's worries me a little, i'm shooting for around 300hp at the wheels. have you upgraded your fuel pump yet? i was thinking about going to the svt pump.
 

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Discussion Starter #14
I am on my 3rd pump. The first two were both replaced under warranty. The third one was the "revised" warranty / recall replacement pump for the '01s.... but as I have detailed in other threads, I don't think it is a pump issue at all, but rather a transient response shortcoming inherent in the design of the returnless fuel system components.
 

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I'm gonna pick on this a little more, so please bare with me...could this, as you said, transient response issue also be caused by a limiting fuel filter? I know our fuel filters can flow a decent amount, however once you start looking at transient response, I can very easily see a pressure drop on the fuel rail side taking a while to catch up over the fuel filter. This may not be the best forum for the discussion, but I wonder what would happen if we went with a better flowing fuel filter...
 
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