Replace 60lb with 80lb?

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cbrown9064
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Replace 60lb with 80lb?

Post by cbrown9064 » Sat May 12, 2018 10:01 am

When I built my setup, I had purchased a used set of S-D 60lb EV1 injectors. Initially I would get a "lean misfire" Check Engine light on a particular cylinder (forget which one...it was a couple years ago). Moved the injector for that cylinder and the problem moved with it, so I just bought one new 60lb injector. Problem went away.

Fast forward a couple years to now and I have a weird high RPM miss (above 6300). It seems to be one of three things, fuel, spark or valve float. I kind of dont think it is valve float, as it does not do this except at WOT. In other words if you run it up part throttle to 7k it is smooth. Boost is about 11-12 pounds at 7k.

I replaced the wires with Ford Racing (I know, I know...) Plugs are gapped at .020, but thinking about taking them back to .030. Coils are new Screamin' Demon. I am not opposed to replacing the wires with an OEM set from Ford.

But to the original question, I am wondering if my injectors are "wierd" since I bought them used. Thinking about just getting a whole new set of 60lbers. But then I was reading some of Decipha's stuff and the recommendation for 80lbers. I dont see myself ever needing that much fuel with this set up, but if they have all around better characteristics than the 60s, I would get them. What say you?

Also, is it just as simple as changing my injector pulsewidth and all other settings stay the same? Or is switch from 60s to 80s going to cause me to rejigger everything in my tune. Like MAF curve. Would like some input there.
1996 Cobra, Novi 2k, S-D 60 lb/hr, SCT BA5k, Paxton IC, QH, BE, Innovate AFR,

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cgrey8
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Re: Replace 60lb with 80lb?

Post by cgrey8 » Mon May 14, 2018 6:21 am

I have no experience with the Deka 60s or 80s, so I cannot speak from experience here. So I'll try to caveat where I think appropriate.

Theoretically, you are right, you should be able to swap the injectors and then swap the values in the tune associated with your injectors (hi/lo slopes, breakpoint, and offset curve). At that point, the rest of the tune should stay exactly the same. The only exception that I can think of that is more academic to talk about than practical is injector timing. 80s will give a shorter PW for the same fuel delivery. So theoretically they will behave slightly differently because "when" they have giving the fuel will be different for all RPM/Load conditions. But the difference between 60 and 80 is so small AND injector timing is such a minor part of EEC tuning anyway, I highly doubt this has EVER been an actual factor that "required" revisiting for anybody changing injector sizes.

Where practice breaks away from theory is if there are aspects of your tune that you modified, possibly unknowingly, to work with injector values that weren't quite perfect to start with. Thus when you put in the 80s and replace those parameters mentioned above to match the 80s, you may find there is touch-up needed elsewhere. In the Closed Loop fueling RPM/Loads, KAMRFs should auto-correct and cover for any error (assuming you haven't disabled Adaptive Learning). But at RPM/Loads where you run Open Loop AND you don't have those areas using learned KAMRF adjustments from Closed Loop RPM/Loads, then you might find places where you were hitting your LAMBSE targets relatively perfect before, but now are off. The amount it is off will depend on how much adjustment had to be made elsewhere in your tune to compensate for less-than-perfect values for your existing injectors.

Note every bit of this is still true even if you replaced your existing 60s for new 60s...particularly if you suspect that some of your existing injectors have worn out of spec or have been out of spec. So you may not be buying your way out of work getting new 60s although I'd say the chances are much better that you would. That's my thoughts on the injectors.

As for your misfire at WOT-only, I'm betting on this being an ignition problem. Anything's possible but the odds of this being an ignition related issue are much better than it being an injector issue. Injectors tend to work or they don't. It's not "harder" for them to work at WOT as compared to non-WOT conditions. Generally speaking, it's lower flow rates that give injectors more trouble than higher flow rates and thus cause drive-ability issues. Contrast this to ignition...ignition gets much more difficult under load than it is at non-WOT conditions. Then when you add boost to it, the difficulty of ignition gets even greater. So any weakness in any part of the system (plug, wire, or coil) is going to be exposed at WOT conditions where it could easily be masked at lower Loads. You mentioned regapping your plugs wider...I'd say do that before you bought anything, not because that'd fix something, but it would make an ignition problem worse and thus confirm you have an ignition weakness somewhere.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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cbrown9064
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Re: Replace 60lb with 80lb?

Post by cbrown9064 » Mon May 14, 2018 1:03 pm

Thanks for taking the time to reply...excellent write up!

I found the cause of my misfire. Me....

In my strategy there are multiple rev limters. I was fiddling with the ones for an auto trans, hence the lack of impact on how the car ran. Figured that out and it was the rev limter(s) causing my issues.

Chris
1996 Cobra, Novi 2k, S-D 60 lb/hr, SCT BA5k, Paxton IC, QH, BE, Innovate AFR,

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Re: Replace 60lb with 80lb?

Post by cgrey8 » Mon May 14, 2018 1:07 pm

So I 1/2 right. It wasn't the injectors at fault...but it wasn't ignition either as I was betting it would be.

Glad you found the issue...and that you didn't spend money throwing parts at it that it didn't need.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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