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Discussion Starter #1
After installing my 60 pound injectors I had a couple issues appear immediately.

BTW this is with stock TB and the new MAF TF is dialed in very well at every single airflow value all the way down to .10 pound of air per minute.

First, cold start up around 60-70 ECT sucks ass. I had it start and then stall 4 or 5 times this morning. As soon as the car starts running, my UEGO pegs the scale at lean and stays there. After enough running to get the narrow band O2 hot enough to do its job, then it runs fine with good trims.

That leads to number two.... after warming up a little and starting to drive, the trims show lean (fuel is being added), maybe 10% or more until the O2 gets up to temp, then at the same airflows the trims are right on. During this initial lean period the car is prone to stalling.

Third, when the throttle is opening, it feels a bit fat and the UEGO pegs at max rich - less than 11:1. Again, the TF is perfect, so this appears to be related to the injector values the accelerator pump uses.

These problems only surfaced with the big injectors... the 42s worked great under the same conditions.

Now I just made some corrections to "crank ISC duty cycle" and think that will help or even solve the first problem, but I won't know until the engine cools down and I try again.

But still, if the injector values (slopes, pulse width, and batter voltage compensation) are correct, I don't see why this should be necessary... same with the accelerator pump.

If the injector values aren't dead on, normal drivability shouldn't really be affected (its not) since compensation has already been made with the TF tuning... but anything else that is relying on good injector data could be.... at least that is my theory.

So.... Anyone using injectors bigger than 42s and seeing similar issues, or not? Are the big injectors just going to be glitchy under light use on 500cc cylinders, or should I expect to be able to get perfect drivability again with them?
 

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rod, if you get this worked out I'd love to hear what you've done. I had some issues at 42#'s and now at 71# injectors I have a different set of issues, but with the 42's I even had some driveability issues, but I have a feelign its my TF. I dont seem to be getting any reading below 113 counts, and I know it's less... I dunno.
 

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I have 50 and have had stalling issues, most of them seamed to be solved now. Tom has been doing all my tuning so I’m not really sure what all he has changed.
 

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Discussion Starter #4
I took some battery voltage readings.

Car off but recently run: 12.64 v
Cranking: 10.4 v
Immediately after cranking: 12.3 v
After idling for a few seconds: 13.95 to 14.10

I am seriously wondering if this, and the injector voltage compensation values are the issue.... to be continued in the private forums.
 

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I run 50's with no problems..... PM Tom over at FF maybe he can point you in the right direction
 

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I run 55's, and the only problem i get is sometimes (maybe 1/4 of the time) my car idles rough when cold for about a minute. And sometimes while sitting in the lanes during autoX it will do the same thing. (lose vacuum, idle bad, etc)
 

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Rod, could be a lot of reasons...

First off, I think most larger than 42's are NOT made by OEM suppliers right? In that case, all bets are off. You could have really wacky flow/Voltage characteristics, etc.

You could be having inconsistent low-flow deadbands (time to open), etc.

I'm also going to guess it's a vry common problem, but you're the first to mention it because you are one of the few large injector users who actually:

A)Expects the car to run right, with no excuses
B)Actually drives the car
 

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Rod, could be a lot of reasons...

First off, I think most larger than 42's are NOT made by OEM suppliers right? In that case, all bets are off. You could have really wacky flow/Voltage characteristics, etc.

You could be having inconsistent low-flow deadbands (time to open), etc.

I'm also going to guess it's a vry common problem, but you're the first to mention it because you are one of the few large injector users who actually:

A)Expects the car to run right, with no excuses
B)Actually drives the car
I believe that turbo rotaries can provide OE quality high flow injectors. Price, actual flow, availability etc are for you to determine, but back when I had access to certain data, I recall that they were amoing the highest flowing units available over-the-counter as an OE part.
 

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Discussion Starter #10
OK, I am sure the voltage compensation was an issue here.

BTW, I did another test and if you care, 10.0v at cranking, 12.2 at light up, and 7-8 seconds to work up to 14.0 were it stays. So obviously proper voltage compensation is necessary.

Now, I see what I did wrong... I had loaded a "values file" for the injectors into one location in my tune, and went on my merry way. I did not realize the same file also needs to be loaded a second time into a different location to get the voltage comp values... I did not know a value file could contain multiple sets of values..... so there you go... voltage comp was in fact a problem, I just unknowingly created the problem


I'll try out proper corrections today and see how it goes.
 

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Discussion Starter #11
OK, cold start, and hot start too, are fine now. The new set of voltage comp values made huge changes in AFR at low RPM and load.

Before redoing the transfer function again, I was up to about 80% lean after adding the new voltage values. I had to richen it up 20% at a time, several times, before it would even start.

All is pretty good now though. Starts fine, trims are on. Very low air flow, IE warm idle at 850, is still kind of flakey though even with trims on the money. I just turned adaptive learning back on and raised the idle to 950, so we'll see how that pans out.

P- The injectors are made by Siemens, I am sure they must be an OE supplier to someone(?). With control over the ECU, I don't see any good reason I shouldn't be able to get things completely right... yet.
 

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Rod, if they are fully OE, you should be able to get it working well. I was just suggesting, if these are modified OE injectors, like somebody modified the pintles and/or rewound them to increase the flow over the OE design, chances are it will end up like so many things in the aftermarket: Crappy stuff that looks nice but doesn't actually work.

 
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