Fuel injection gas mileage vehicle?

[custom442]

I've been toying with this idea for a while... I think 85 cutlass brougham said something like this a while back and I can't remember what exactly it was.

Let's say I have a mpfi engine, any engine, and I take out the old injectors and put new ones in that flow half the amount. Then I use an adjustable fuel pressure regulator to dial in the correct pressures and/or have an ecm tune so that I'm not running rich or lean while driving with half the fuel.

Then to compensate, lets say I were to buy an SDS controller or equivalent remote injector setup (either in the intake or intake tube). I add the correct injectors and have it tuned/etc so that only at WOT it's flowing the full amount of fuel that it would otherwise be flowing on a stock application.

Is it possible to tune for injectors that are half the size as stock without killing air fuel ratios? Then have my full power when I need it only at WOT with the extra injectors?

I'm actually thinking about doing this on my little 1.5L honda after fixing up the cutlass and truck to try and suck another 10 or so mpg's out of it. Any thoughts?

edit: for example let's say a stock engine has 20# injectors and I downgrade to 10#. Would I need to be running those 10# injectors at max power all the time? Or would it be similar to using 20# injectors and I can use half the fuel of the 10# injectors all the time just not at WOT?

 

[kingcolbert83]

if you were to do this why couldnt you just use the original injectors or bigger and control the fuel on those. I say this because regardless if your swapping or not you are still trying to control the a/f so if you have a performance engine and the injectors are already too small to begin with then your wot will suffer right? Nevermind disregard that. I just remembered you said a stock honda engine. I got too far ahead of myself.

 

[custom442]

Ya, it doesn't need much power to get these engines down the road. I would be hesitant to do this on a v8 for sure.

What I'm trying to find is... if the injector sprays 'X' amount, lets say for 2,000 rpm under a certain load designated by the computer, does that ratio stay the same after an ecm tune no matter what injector size is in the car? Or would I need to spray the same amount of fuel at that 2,000 rpms ... so if I were using 'X' amount of fuel I would then need two times 'X' if I halved the primary injectors size...? I'd make up for whatever power loss at WOT with extra injectors and SDS controller

I was also just thinking of how this setup would work on somethin like an old crx hf that already gets 50mpg... that would be motorcycle mileage territory if you could suck 5-10 mpg more! And the crx has so much room in the back I'm sure there is a way to hook up an electric aux. generator or hybrid motor... :idea: just ideas. but that would be a sweeet daily driver lol, 60-70 mpg so much for the prius and I wouldn't look like a dick driving it :lol:

 

[kingcolbert83]

I think it could work with a standalone system that you can tune each and every parameter and Im sure there is a way to have the injectors flow more fuel after a certain rpm. Heck is basically the same concept like with nitrous. Nitrous kicks in at certain rpm and timing and fuel are adjusting accordingly. I think the main problem would be finding a program that can allow you to adjust all the parameters. plus with running half the fuel you will need to tune the spark advance too which falls into the programming.

I really think it can be done with the hardest part being the standalone program that ties everything together and the tuning. I got another idea for twin turbo I been thinking about. check the post when you see it and let me know what you think.

 

[jrm81bu]

I don't see how reducing the injector size would make it use less fuel if you are using the same a/f ratio. If your gonna do a custom tune just have the part throttle tune set to be pushing the limits of running lean. That is the smallest amount of fuel you can use without it going boom. An injector doesn't just squirt x amount of fuel everytime it squirts(well it does if its held open the same amount of time, every time), the computer will change the how long it holds the injector open to adjust for rpm, load, throttle position, etc.
So if you use a half size injector the computer will just hold it open longer to get the same a/f that's programed on the tables. And that smaller injector may not be able to deliver a safe amount of fuel no matter how long its held open. You would be over 100% duty cycle all the time, which means you would be replacing them injectors often.

 

[kingcolbert83]

yea thats what i was thinking but you put it in better words. He could just use the same injectors but with the proper tune. I would also use a knock control system if going to run that lean. Here is a good one I was looking at when doing research on turbo and supercharging. Would also be good on a high compression motor or any motor for that fact.

http://www.jandssafeguard.com/

 

[custom442]

jrm81bu - that's what I was thinking at first, then I looked into the extra injector thing. These little engines only need a few hp to run them, they can be programmed to use smaller injectors without problems at all and without running them at maximum capacity, it'll just go slooow. I guess my question was - is it possible to get a tune to fit smaller injectors when doing 95% of around town driving...they don't have to be 50% capacity of the original, maybe 75% or something. Surely it would force the engine to suck less gas if programmed correctly... no? Then when you need to get on the onramp or somethin, just punch it to WOT and you've got all 90hp on demand :lol:

kingcolbert - It isn't a question of running lean, just giving less gas all around and less air. Can I run the engine in my cutlass with a 350cfm carb instead of a 770 and get better mileage? Answer is yes if I tune correctly, same goes for injectors

It's just an idea that might gain a few mpg's. Is it worth all the extra money? Probably not unless I could find a cheap SDS controller (those two don't belong in the same sentence). I have free programming plus cost of shipping to wait4meperformance, so the tune would be the cheapest part but it might take a few tries to get right

 

[kingcolbert83]

now only if I could hit the lottery I could just try all this stuff. Who knows I may come across something that can be incorporated into todays cars or retrofitted onto older cars. For some reason I love the idea of a electronic carburetor. I guess thats why I like the powerjection 3 so much.

 

[custom442]

now only if I could hit the lottery I could just try all this stuff. Who knows I may come across something that can be incorporated into todays cars or retrofitted onto older cars. For some reason I love the idea of a electronic carburetor. I guess thats why I like the powerjection 3 so much.

Ya, but once you start working with mpfi the t.b. (retro carb) injection idea is thrown out the window :wink:

 

[kingcolbert83]

you seen the powerjection 3 carb? its like a tbi but better. The computer and everything is built inside the unit. Plus it only controls the fuel so you can add your own ignition system. Some people wish that it could control both fuel and spark.