10% EFFICIENCY GAIN WITH SFI MEGA$QUIRT?

[gaz]

Hello,

The crossroads are in my sights; if it is conceivable to realize a 5% efficientcy gain from using the SFI with my 94 4.0l ohv build, I will take the leap. I would like 10% but for the amount of $ it looks like the system will cost, I will be happy with 5%.

Friendly shout 2 @PetroleumJunkie412 ..)

 

[franklin2]

Hmmm. If your truck got 20mpg, a 5% increase would be 1 more mpg. You could probably get that by inflating the tires to the sidewall pressure and being easy on the throttle. 10% on a truck that got 20mpg would be 2 more mpg. What gear ratio are you running? What transmission? Synthetic fluids throughout?

What type of driving do you do? All highway? Do a search on "Hypermiler". Your goals seem very achievable without changing the fuel injection system.

 

[alwaysFlOoReD]

I've recently seen a comparison between the microsquirt/megasquirt and the speeduino. Speeduino being cheaper but more DIY. That might interest you?

 

[RonD]

1994 Ranger 4.0l uses Batch Fire injection, 3 injectors open at the same time, and are alternated with the other 3 every 1 RPM, usually odd/even, so injectors 1 3 5 open then 2 4 6 open on the next rotation of crank shaft

This is very close to how a carburetor works, lol, so not very efficient
The intake is just kept full of air/fuel mix and when an intake valve opens if sucks in what it needs, same as a carb setup
What happens is the the fuel coats the inside of the intake so is wasted

Sequential injection opens each injector as its cylinder's intake valve opens, so less wasted fuel coating the intake
While this can be done with just a Crank sensor, the addition of a Cam sensor makes it more precise

1994 Calif sold Rangers or Explorer 4.0ls had Cam sensors and used sequential injection
So you could get wiring harness and computer from one of those
Also need to add the EGR system
EGR system is actually better for MPG because the computer can run a more aggressive spark curve because cylinders are not getting too hot under load

But yes, a switch to any sequential EFI will improve MPG

One of the biggest advantages of EFI is that the injectors can be TURNED OFF
Think about how an engine works
The pistons and valves create a low pressure/vacuum in the intake
A carb has Jets that this vacuum SUCKED fuel out of, EFI opens injectors to add fuel that is sucked into the cylinders
When you are driving and take your foot of the gas pedal the throttle plate closes and Vacuum goes way up, 20+"
In a carb that caused more fuel to be sucked out of idler Jets, and it wasn't needed
With EFI the injectors are SHUT OFF, no wasted fuel

With a carb many would shift to Neutral when coasting down a hill/grade, to save fuel
With EFI you want to leave it in gear with foot off the gas pedal so RPMs stay above 1,500, and injectors are OFF
Under 1,500rpms computer will restart injectors at idle levels, so you are using fuel
TPS(throttle sensor) is used for this
On a long downhill grade computer will inject fuel now and then to keep Cats hot

If you think about how anyone drives, speed up and then slow down, lol
With EFI you are not using any fuel when slowing down
So don't shift to Neutral and coast, leave engine in gear, and save some fuel, also save wear and tear on the brakes when using engine as the brakes on a downhill road

 

[alwaysFlOoReD]

The speeduino can do sequential on four cylinder but not six or 8. I'm not sure what the micro/mega can do.

 

[franklin2]

With a carb many would shift to Neutral when coasting down a hill/grade, to save fuel
With EFI you want to leave it in gear with foot off the gas pedal so RPMs stay above 1,500, and injectors are OFF
Under 1,500rpms computer will restart injectors at idle levels, so you are using fuel
TPS(throttle sensor) is used for this
On a long downhill grade computer will inject fuel now and then to keep Cats hot

If you think about how anyone drives, speed up and then slow down, lol
With EFI you are not using any fuel when slowing down
So don't shift to Neutral and coast, leave engine in gear, and save some fuel, also save wear and tear on the brakes when using engine as the brakes on a downhill road

I am not sure I agree with the above. True, the injectors are off, many fuel injected cars do this, once you get really slow there is a "lurch" in the motion of the vehicle as the computer turns the injectors back on. It will turn them back on by itself eventually.

But even though the injectors are off, you still have engine braking. Throwing it in neutral would get rid of that friction. You would have to experiment to see what gave you better fuel mileage; Coasting in neutral with the engine idling with fuel, or normal driving with a very light foot.

 

[franklin2]

As fuel gets more and more expensive, spending money on a vehicle for better fuel mileage makes sense. But you do need to figure the payback.

I drive 40 miles each day to work. Right now I get 18mpg when the weather is warm. So I use 40 divided by 18 equals 2.22 gallons per day. At 4.50 per gallon, that costs me 9.99 or just say 10 dollars per day. I am trying to get at least 2 more mpg myself in my BII. If I got 20mpg, I would be using 2 gallons per day, which would be $9.00 per day. Savings of 1 dollar per day. Right now I have spent $39 on a distributor that I am going to use for parts to rebuild my original distributor. If I am successful, it will take approx 39 days of going to work to break even.

If I am in the same scenario and want to change my engine to fuel injection, it would be easy to see the payback. If I spent $500.00 on a you build it fuel injection system, it would take 500 days for payback if it gave me 2 more mpg. I would rather have one of the holley fuel injection systems that is about $1,250 or more. If that only gave me 2 more mpg, that would take 3years for payback. If it gave me 4 more mpg, 40 divided by 22 is 1.81 gallons times 4.50 equals $8.18 per day. Savings of 10 minus 8.18 equals $1.82 per day. $1,250 divided by $1.82 equals 686.81 days or a little less than 2 years payback.

 

[RonD]

I am not sure I agree with the above. True, the injectors are off, many fuel injected cars do this, once you get really slow there is a "lurch" in the motion of the vehicle as the computer turns the injectors back on. It will turn them back on by itself eventually.

But even though the injectors are off, you still have engine braking. Throwing it in neutral would get rid of that friction. You would have to experiment to see what gave you better fuel mileage; Coasting in neutral with the engine idling with fuel, or normal driving with a very light foot.

Not sure what you are disagreeing with?

Injectors off = 0 fuel used
Injectors on = fuel being used

When the engine is below a certain RPM(say 1,500) and foot is off the gas pedal, computer sets idle level fuel use
So 0 fuel used above 1,500rpm when coasting in gear, friction doesn't matter
Unless you are talking about Coasting downhill to see how fast or far you can go in Neutral, now that would be one to try
But if you left it in OD with RPMs at say 1,600(or higher), so minimal engine braking then I bet the No Injectors would win out, on the long Coast test

 

[gaz]

1994 Calif sold Rangers or Explorer 4.0ls had Cam sensors and used sequential injection

@RonD,

As it turns out, the doner Explorer I am using is a 1994 California 4.0l with EGR. Are you saying that it is SFI not batch fire?

 

[gaz]

@franklin2,

While I'm no hyper-miler, I do have very moderate, conservative driving habits. I expect to see 30mpg on dedicated highway drives; I am hoping for 25+mpg while highway towing a small camper.

The rig is set up so that I am running at max or near max engine torque at legal highway speeds. The built 4.0L is going in an 87 BII; this Bronco managed over 24 mpg while highway towing a 2,400 lb trailer with a built 2.9l/A4LD. With all the extra torque that a stock 4.0l makes this build should be working pretty easy at 60 mph.

With the SFI info from @RonD, I feel it may pleasantly exceed my expectations. The best fuel economy I've ever managed to obtain was from an SFI 60°v6, just didn't happen to be a Ford

 

[franklin2]

Not sure what you are disagreeing with?

Injectors off = 0 fuel used
Injectors on = fuel being used

When the engine is below a certain RPM(say 1,500) and foot is off the gas pedal, computer sets idle level fuel use
So 0 fuel used above 1,500rpm when coasting in gear, friction doesn't matter
Unless you are talking about Coasting downhill to see how fast or far you can go in Neutral, now that would be one to try
But if you left it in OD with RPMs at say 1,600(or higher), so minimal engine braking then I bet the No Injectors would win out, on the long Coast test

I am disagreeing with the "friction doesn't matter". I think you could coast farther with the transmission in neutral. The debate is whether that would give you better mpg, or your method of leaving it in gear with 0 fuel.

 

[konrad911]

I’d never think about switching to EFI/SFI/Standalone because of MPG.
This can be done though, quite effectively.
Not sure if Sequential matters that much, but:

1. Overrun fuel cut - works and saves fuel (confirmed by myself in my car)
2. Wideband o2 sensor - allows to monitor / adjust fuel delivery when needed and where needed. everyone drives a bit different, why not tune VE Map according to individual preferences?
3. Switchable fuel maps - one for daily, one for terrain/towing i.e.

Probably few more areas where you can improve as well.

I just don’t believe the fuel savings alone would finance the controller and all the works needed to make it run. Dyno tuning? I think it’s a must.

I’ve been using MegaSquirt (ms2/extra) for 10 years in one of my cars. I’m switching to Ecumaster though - much better price for what you get (I.e. included WB o2 controller, knock sensor controller (2 banks), etc.).

 

[lil_Blue_Ford]

I’m definitely curious to see where this all gets to. My first Ranger I was seeing 18-20 mpg around town with a cap and 20-22 with a tonneau with 26-31 highway up until the ethanol gas, then it was about 17 around town (tonneau) and 20-22 highway up until it got wrecked. That was ext cab, 5-spd, 3.73 gears, 2wd, 3.0. Both of my ext cab 4.0 autos (92 with 3.73 and 00 with 4.10) were both around 14-16 mpg. My Choptop on 33’s with 4.10s was getting 18-20 with the 2.9 and when I went to 35’s and 4.0 dropped to 14-16. My 88 Bronco II was getting 18 with 3.73s until it blew up.

I have been trying to plan mods into my builds to see if I can bump up economy some and the thought crossed my mind wondering if there was some way to add in control of performance to some of these older vehicles like the newer ones have (normal, economy, sport, towing/hauling) where you just have a selector and away you go. Either way I’m following this stuff as close as I can because if I can boost performance AND fuel economy, it’s a win/win.

 

[RonD]

To see if its SFI just look at 3 of the injector's wire colors
All will have the 1 red wire(12v)
If you see each injector has a different ground wire color then its SFI, 6 wires back to the computer

If 2 of the injectors have the same color ground wire then its Batch Fire
Batch fire only has 2 ground wires for computer, one for 3 injectors



It's like the old sock riddle
If there are 6 dark blue socks and 6 black socks mixed together in a drawer, and there is no light on the drawer to see clearly
Whats the minimum number of socks you need to pull out of the drawer to have 1 matched color pair of socks
3, for one dark blue pair or one black pair

So if you look at 3 injectors and don't see same ground wire color on any then its SFI

 

[gaz]

@RonD,
I had to blow the dust off Charles Probst's "Ford Fuel Injected Electric Engine Control" manual; sure enough, the 1993 (and newer) California emissions EGR 4.0l's have SFI???

This has REALLY made me so happy to learn! Thanks Ron.