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Here is what FIC sent me for my Blue Max 1350's:

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BTW - Those latency numbers at each voltage are exactly the same as the ones they sent for the Blue Max 1250's...so they have to be best guesses. I'd be curious to see those recommended numbers from a larger set.
 
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I apologize that its not a copy/paste from the sheet but these were the latency values that FIC provided with my 2150's.
8 volts - 1510μs
10 volts - 990μs
12 volts - 830μs
14 volts - 750μs
16 volts - 700μs​

:dsm:
 
14 volts - 750μs
Which is actually not that far off from what I measured on my own 2150s. If I were to "line them up" at idle flow (more on that below), the average I saw was about 765 usecs.

But that ranged from one injector at 730 to another at 810. So you have about a 70-80 usec spread there.

With the flow rate at 2150 cc/min, that's like a difference of 330-380 usecs on a set of stock injectors!

So that 70-80 usec difference is pretty significant in terms of getting a good, consistent idle.

You should also keep in mind that "deadtime" is a made up number. It's not the real zero-flow point of the injectors. It's just the X-axis intercept that happens to make the factory ECU's linear approximation work out "close". You can tweak fuel scale (slope) and deadtime (intercept) at will to get the "fit" that you want.

So when I said "line them up" above, I meant those deadtime numbers were only the numbers that happen to work best to get the injectors all matched at idle. But if my goal were some sort of "in between idle and cruise", then I'd line the approximations up differently and get different deadtime numbers as a result.

What we really need here is a change to the ECU code. We are constantly trying to make injectors fit a linear approximation even when it's very clear their flow is not linear. We need to change how the ECU models injector flow rate to take into account how injectors actually work... It's coming. :)

Thomas Dorris
 
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Thanks for the info Tom; a local bought a set of 2150s and had a buddy tune his car. After he tuned the car he called me and said I was going to love the 2150's once they were installed on my car, apparently by just inputing the FIC injector voltage offset table values they idled like stock.

Mine are finally installed I'm just trying to knock out a few other things with my car before I start it up and tune it again. We'll see...

It's coming. :)

Thomas Dorris
:sneaky:

:dsm:
 
Nice, that looks like some really good logger proven results right there. This should definitely have a big hand in the longevity of a motor at higher HP levels. Just think about what all that spikey junk would be doing at 9k rpms. ;)

The injector deadtime/latency has less of an effect as the duty cycle increases. It becomes less and less of the total time the injector is told to be open, so it's effect decreases.
 
The injector deadtime/latency has less of an effect as the duty cycle increases. It becomes less and less of the total time the injector is told to be open, so it's effect decreases.
'tis true. For general reference, we tend to tell people that you can expect a change in deadtime to have twice the effect on mixture at idle that it would have at cruise because effective pulsewidth at idle is half that of cruise. This effect certainly decreases as effective pulsewidth increases. More airflow results in higher effective pulsewidth and less relative effect from deadtime.

One (perhaps non obvious) way to use this in tuning is to check combined fuel trim at idle and compare to cruise. If idle fuel trim is more positive than cruise fuel trim, then increase deadtime. If idle is less positive than cruise, decrease deadtime. Because the effect of changing deadtime is greater at idle than cruise, this general rule tends to bring the two fuel trims together. Once they are matched (non-zero, but equal), you can then adjust global fuel to bring them both down to zero together.

This only works with well-matched injectors with linear flow rate curves between idle and cruise. With non-matched injectors and/or non-linear flow, you have a bigger problem of course.

Thomas Dorris
ECMTuning, Inc.
 
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Maybe i didn't read this entire thread but i want to know how one goes about tuning each injector properly? How do you know what ot add to what injector? Is there some sort of feedback logging you can look at to adjust them? what tells you to add time to Inj # 1 and leave Inj #3 at zero? I"m really curiouse on this one please some one fill me in
 
Maybe i didn't read this entire thread but i want to know how one goes about tuning each injector properly? How do you know what ot add to what injector? Is there some sort of feedback logging you can look at to adjust them? what tells you to add time to Inj # 1 and leave Inj #3 at zero? I"m really curiouse on this one please some one fill me in

See the last line of post #93. ;)
 
i want to know how one goes about tuning each injector properly?
More info here:

injdata-overview [ECMTuning - wiki]

It's a test stand we built specifically for doing high resolution measurements of injector flow rates with various configurations using various drivers. The default driver, of course, is our DSM ECU driver. :) But anything *could* be used. We have an adapter board already made for an EVO ECU driver, for example.

injdata-driver [ECMTuning - wiki]

Thomas Dorris
 
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