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Old 02-26-2017, 02:20 AM   #1 (permalink)
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Anybody have actual technical knowledge about E85 "kit" pulse extneders?

To get this out of the way: I didn't post this to be told not to run E85 or to discuss whether or not anybody should run E85, please if you're going to reply with anything like that just save us both some time and hit the back button on your browser. Thank you.

I understand that the premise of operation on any of the normal E85 kits is to intercept the pulses already going to the fuel injectors, lengthen them (or add an echo/reverb to them) and in doing so effectively shift the LTFT window on your car's existing fuel strategy when it's running closed loop. Since modern EFI remembers LTFT offset when running open loop (WOT) the problem of ethanol's oxygen content difference vs. petroleum resolves itself in an elegantly simple way; you simply have less maximum lean trim available no big deal don't drive to the Himalayas.

But here's my question: Do they do anything else?

Because if they don't do anything else I don't see why literally the same results couldn't be achieved by installing bigger injectors. 27lb in a 24lb application, for example.

Any constructive conversation to offer?

(Also yes, I made a typo in the title.. sorry about that)

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Last edited by shovel; 02-26-2017 at 02:31 AM..
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Old 02-26-2017, 04:26 AM   #2 (permalink)
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It would be better to just up injector size anyway. Let's say your injectors flow 100cc on normal gas. Then let's say it takes exactly 65% more E85 to make the same whatever. You just put in 165cc injectors to compensate and the computer is none the wiser.
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Old 02-26-2017, 05:20 AM   #3 (permalink)
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I think the simplest solution is the best.
Bigger injectors.
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Old 02-26-2017, 10:30 AM   #4 (permalink)
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I agree with the above posters. Same pulse width with a larger injector, ecu doesn't have to modify anything.
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Old 02-26-2017, 11:11 AM   #5 (permalink)
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Always a fan of the simplest solution; plus at $10-12 per injector often enough for used "refurbs" on many cars that makes a 4 cylinder under 50 bucks to convert and no extra boxes or wires under the hood.

But what if the E85 kits do something more than just add reverb?

If there is a logic function that scales the reverb with engine RPM or if it has some cold enrichment routine or something, those wouldn't be addressed by changing injectors.

For what it's worth I've had two cars on E85 kits from FuelFlex and they worked awesome with no drawbacks, but now I have a new little daily driver and figured I would start researching other approaches.
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Old 02-26-2017, 06:42 PM   #6 (permalink)
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I don't believe in the existence of things that shouldn't be messed with.
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Old 02-26-2017, 07:12 PM   #7 (permalink)
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It would be instructive to know what all is hooked up, and where is it hooked up with, with regard to an E85 kit. Does the E85 kit require a setup procedure?

I suspect the only things that really get hooked up are power, ground, and the injector connections themselves. I also suspect that there's a lack of any meaningful setup procedure. If this is the case, then I suspect that the E85 kit only lengthens fuel injector pulses by some set amount. And if that's the case, then there's no reason why you could not just use larger flowing fuel injectors, instead.
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Old 02-26-2017, 07:25 PM   #8 (permalink)
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Quote:
Originally Posted by t vago View Post
It would be instructive to know what all is hooked up, and where is it hooked up with, with regard to an E85 kit. Does the E85 kit require a setup procedure?

I suspect the only things that really get hooked up are power, ground, and the injector connections themselves. I also suspect that there's a lack of any meaningful setup procedure. If this is the case, then I suspect that the E85 kit only lengthens fuel injector pulses by some set amount. And if that's the case, then there's no reason why you could not just use larger flowing fuel injectors, instead.
You are correct about the connections; it's just injectors (female on one side, male on the other) and a ground. The overhead in the units appears to be taken care of by using the DC offset of the injector channels.

The two kits I've had did have trim adjustment, and said they had a "Cold start assist" feature which I have to assume is just a fat enrichment bias when cold or when first started. Unfortunately both cars are long gone so I can't take another look at them for temperature sensors or timing IC's or other clues to their possible nonlinear behavior.

Obviously the benefit of having a magic box kit is that there's something to sell ("Buy our box!" is a lot more marketable than "Buy new injectors for your car, we've figured out which ones you need!") and it's a lot easier to install, literally just clip the wires in place. No mess, no cutting and completely reversible. If they sold larger injectors in a kit that actually requires a bit of aptitude, bleeding off fuel pressure and removing the fuel rail(s), and for example on my wife's car that would also involve removing the upper intake manifold which itself requires disassembly of a few throttle and emissions related bits.

Still, if the box isn't necessary it's not necessary.

For Science I've bought a set of 27lb injectors for my Escape, it ships with 24lb injectors. I've also been keeping an eye on LTFT and fuel pressure histograms in FORSCAN to see if the factory bits are in a good place to be shifted. So far it looks like fuel delivery (from the pump)is adequate at WOT on-ramp pulls and there's generous room for de-enrichment in the fuel trim maps
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Old 02-26-2017, 07:58 PM   #9 (permalink)
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Old 03-04-2017, 07:10 PM   #10 (permalink)
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Quote:
Originally Posted by shovel View Post

For Science I've bought a set of 27lb injectors for my Escape, it ships with 24lb injectors. I've also been keeping an eye on LTFT and fuel pressure histograms in FORSCAN to see if the factory bits are in a good place to be shifted. So far it looks like fuel delivery (from the pump)is adequate at WOT on-ramp pulls and there's generous room for de-enrichment in the fuel trim maps
Phase 1 of Science has been completed; I have received and installed the 27lb injectors.

Install was trouble free. No CEL . I want to go drive around with logging enabled to see what it's doing, but also I don't want to drive around for no reason (not very eco, that) - tank presently is about 50% full of ordinary E10 pump gas in the 87 octane flavor.

I did drive to the store earlier today, just a 3 mile sprint each way, went WOT up to the speed limit and all seemed well.

Will update later once I've had proper logging of the fuel trim as reported by the ECU, and after I've burned E85 if the LTFT looks good. Getting to E85 will of course require me to run the tank mostly empty first and that's still at least a week, maybe 2 weeks from now.

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