jiinxy

Let me preface this by saying I've been debating tossing a standalone in my farm truck. It's an old f150 with a 302 and I've been thinking about trying to fix it up a little bit and make it nice. For EFI, my two options are microsquirt, which is 100% PNP, or MS gold box, which is also PNP but requires me to swap the truck engine and ecu harnesses out for an 86-94 mustang harness set. The microsquirt is only around $500, while the gold box is around $900, plus another $300 or so for the harnesses. Microsquirt is batch fuel injection while the gold box and mustang harness would let me run full sequential. The gold box also could let me ditch the distributor fired ignition and go to CNP sequential ignition as well. Since the cost difference for the fix up isn't that much, the main decider on whether it's worth is comes down to fuel economy. Thustly, I've been searching around the web for and answer to this question:

How much actual difference in fuel economy does batch vs sequential fuel injection make?

The obvious answer, and the only one you'll find doing a google search is "sequential only makes a difference in idle and cruise". Duh. That's where fuel economy gains really come from. Seeing as the miata/megasquirt platforms have basically been the very first to adopt the technology, has anyone actually tested the mpg difference between batch and sequential efi?

rabid

With sequential it is possible to manage each cylinder. With some intake manifolds there can be a pretty big difference in air flow each cylinder. Also injection timing is a thing. Do you want to put EGTs or O2 sensors on each exhaust port? Is your answer hell yess, then sequential is for you.

jiinxy

While I understand individual cylinder tuning is possible with sequential, individual egt and wbO2s aren't required for sequential multiport fuel injection.

Power I'm not concerned about. The motor makes roughly 200 chp and 300cfp. The tranny is a non electronically controlled 4spd with overdrive. My main concern is getting it to run more smoothly than the factory batch fire ecu and bumping the fuel everyone from about 14 average mpg up to 20-24 mpg (with the help of other supporting mods of course)
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rabid

If your engine has rich cylinders and lean cylinders and some have the sub optimal spark advance, you need to individually tune them for power and efficiency. Doing that without sensors is just kidding yourself. Spark plug reading can only tell you an average temperature during a pull and won't help you tune economy. A rich cylinder during WOT can be lean during cruise. You won't know without sensors on each cylinder.

jiinxy

I understand how engines work. I don't think you understand the question or my reason for asking.

The real world doesn't revolve around min-maxing. Oems have not once or ever installed individual cylinder egts or O2sb on production road cars.

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hector

Have I tested the actual diff from batch to seq as far as mileage goes? No.

Do I think it will make a world of diff in mileage? No.

IMO and from what I understand about it, you may not get any improvement at all, not even in idle quality, on certain applications. The injection on-time is going to be the same whether it be two pulses (or more) or just one pulse as you still need the same amount of fuel.

The diff may be substantial though, on an engine with big injectors, that you can't really control them with extremely short pulses when in batch so a longer pulse from seq is a major benefit and will translate to a better running engine especially at low engine speeds, overrun, etc.

Same goes for seq vs batch ignition. Very high revving engines don't have the dwell time before ignition events to charge the coils. Back in the day this was solved with capacitive discharge ignitions that had very short but very high bursts of energy. Today with electronics, you don't need CD ignitions to rev to 10k with seq control of the coils.

So IMO, seq will not help you get better mileage in this application without any other supporting mods. It might be possible that with improved intake manifold and exhaust, newer style injectors, some torque converter mods, and very good tuning, you may get that older engine to get a couple more mpg but to go from 14 to 24 mpg, I can't see that jump even with seq. Of course, IMO, which ain't worth jack.

jiinxy

Hector, that's a good point about requiring the same overall amount of fuel for idle and cruise between batch and sequential.

Regarding supporting mods, if I ended up throwing money into the truck/motor, it'll get a set of aftermarket aluminum heads. I think TC is out the window, but fabbing a new intake manifold isn't. The poor old AOD shifts at a max of 4500rpm, so high RPM conditions simply do not exist One nice thing is the converter does lock up, and the tranny has a 4th gear direct drive OD, so the tranny essentially becomes a passsthrough. I think 14->24 is entire possible with supporting mods if the engine VE can be increased. Lowering the truck 5" should help with aero as well, and with some extra HP, the rear gear can be a little taller as well.

hector

Well if you decide to do it, then please get back to us with the results. This seems more of a project for you than a necessity so have fun with it.

IMO, the best way to increase mileage is to change driving style. By keeping the engine out of high load situations you will undoubtedly get the best mpg. And IMO, the best way to do this mechanically is through gearing. So getting a 10 speed transmission would likely be the best way to go about increasing mileage. Every engine is going to have a sweet spot range where it will be the most efficient and having lots of gears almost guarantees that you will be in that sweet spot.

As far as engine mods go, I would say that heads would be the best change to make. Do they need to be aluminum? IMO, no. But replacing the design of the 1950's Windsor engine would go a long way regardless of material. Piston dome design and obviously raising compression plus longer connecting rods will help too. Hell if you can manage it, I'd go to a 351W as there really is no replacement for displacement. I am of the opinion that a bigger engine will be more fuel efficient than a smaller engine when it comes to moving weight, especially in highly transient conditions. It also cuts down on engine wear even though this doesn't seem to be a concern to your project. And of course valvetrain mods to help maximize the sweet spot range given the comp ratio, cam, intake, exhaust combination.

Aerodynamic improvements are sure to help but a brick is a brick. Only so much you can do with it without making it look like a salts flat racer.

Again, this is all IMO which isn't worth much. Some people might say the best way to go about it is with a turbo v6 and I can't say if that wouldn't be a better idea or not.