Fuel injection gas mileage vehicle?
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on acceleration you're completely correct, it'd be about the same. But what about those times on the highway when you only need to use the slightest bit of fuel... it seems it'd be much easier to tune a smaller injector to use less fuel, then at WOT send more fuel with extra injectors. It seems like it'd work perfectly I don't see how it couldn't be set up to use less fuel? I mean, it could be done sure. But from what I've seen the 'gas mileage' performance tunes on tiny engines = slower at WOT. With extra injectors you've still got some power to move around a little. But that's why I'm asking because I don't do ecm programming so this stuff is beyond me
I've just heard of people running extra injectors and extra ecm to control them on boosted engines to deliver more fuel at WOT. So why couldn't the same idea be applied but take away power to begin with..?
Ok, i think were on the same page about it being easiest to use less fuel with a "milage tune". Your main concern is you still want all the performance you can get at wot. Right?
If thats the case a cutom tune should be able to do just that. On the graph it could be set that at Crusing rpm and very little throttle input and load, it would lean it out all the way to the edge, same with tming. But then in the upper rpms and alot of throttle input and load it can richen it back up.
If thats the case a cutom tune should be able to do just that. On the graph it could be set that at Crusing rpm and very little throttle input and load, it would lean it out all the way to the edge, same with tming. But then in the upper rpms and alot of throttle input and load it can richen it back up.
The reason to run smaller injectors is simple: Large injectors are not very efficient when asked to run a shorter duty cycle. So, running 16 injectors instead of 8 would give you the best of both worlds. Just cut the flow rate needed at WOT in half and only run on 8 of them most of the time. Then, when they are needed, set up the ECU to run all 16 when the engine needs that much fuel. I originally came up with this concept when researching a fuel efficient but powerful turbo installation I was contemplating. I was thinking of using a Nissan GA16DE as my base engine, but the power output I wanted required a 370cc injector (stock size in a SR20DET). Well, the stock injector for the GA was half that size (185cc), so my solution was to add a secondary stock fuel rail under the intake manifold (it's an inline 4) that would only be used under boost. Thus, I could run the engine off the stock map when off boost and keep the fuel economy, but have the ability to run the extra fuel when boosted. In fact, I later found out that Edelbrock offered this exact configuration in a turbo kit for Civics with the D16Z6 (SOHC VTEC) engine. I was also planning a Garrett GT series turbine for added low RPM torque and efficiency, but that is another part of the equation.
Did I ever get beyond the concept stage on that one? Sadly, no. I am a broke *ss pizza delivery driver and don't get to build too many things due to a lack of income.
Did I ever get beyond the concept stage on that one? Sadly, no. I am a broke *ss pizza delivery driver and don't get to build too many things due to a lack of income.
What makes the large injector less effecient? And in the case of the civic what size injector does it use? Can't be all that big, halfing the size might be a problem if you can't find an injector that small. Now i did say this idea had merit giving that at its shortest duty cycle the injector was still delivering more fuel than needed. But wouldn't you be able to tell that was the case by seeing a rich a/f ratio at cruise speed, before you started to modify things.
Here's how I see it - the engine and drivetrain needs some amount of power to get down the road. Let's make up a number for a 90 hp old civic. Let's say that number is 20hp. So we only need that much, but we've got injectors that can spray way more fuel than that. Now we swap for injectors that spray half that amount of maximum fuel. So now our max hp is 45 without WOT. So I get a custom tune, etc etc and we're holding the injectors open longer to get more hp for the same time accelerating down the road. I'm sure I could get similar results if I barely tap the throttle and drive like a granny down the road, I could probably gain about 5 mpg's. But this would get me that in normal everyday driving without worrying about having a feather foot.
Pretend you've got a block under your foot when you're driving and you can only depress the pedal half way. That's how much power I'd be getting. But not only that, the smaller injectors would give me that power over a wider map than the full size injectors, so there should be a sweet spot where it accelerates smootly albeit much slower, and is real miserly on fuel. That's all I was trying to get at.
It's real simple if you think about the carb idea. swapping from 700cfm carb to 350 cfm carb & tuning correctly will gain you a few mpg's but it'll go slower.
Only difference here is I'd have extra injectors to give it fuel when it needs it and a separate fuel map run by a different controller for WOT.
I don't think I'll ever do this, and what the exact results are, but it could be done. I don't think it's going to double the mileage or anything, but I don't see how it wouldn't add about 5-10 mpg's as long as youre not in the throttle all the time.
jrm81bu- It's not about a/f ratios, it's about how much power you're getting. More hp = more fuel. Do I really need 23.1# injectors on my v6 truck when the v8's have the exact same 23.1#/hr? It's all in the computer tune. I could downgrade injectors on the truck and have it tuned for the same power (if those damn GM ls series spider injector setups would let me). But then again, a v8 or big v6 needs a lot of power, don't think you could get away with something like this on those engines. But we're talkin about a little 1.3-1.5 L
here's something to think about too - most newer stock engines can run a small s/c setup with stock fuel system at around 6psi. This means your injectors are usually bigger than needed. To me that's efficiency that's gone to waste.
Pretend you've got a block under your foot when you're driving and you can only depress the pedal half way. That's how much power I'd be getting. But not only that, the smaller injectors would give me that power over a wider map than the full size injectors, so there should be a sweet spot where it accelerates smootly albeit much slower, and is real miserly on fuel. That's all I was trying to get at.
It's real simple if you think about the carb idea. swapping from 700cfm carb to 350 cfm carb & tuning correctly will gain you a few mpg's but it'll go slower.
Only difference here is I'd have extra injectors to give it fuel when it needs it and a separate fuel map run by a different controller for WOT.
I don't think I'll ever do this, and what the exact results are, but it could be done. I don't think it's going to double the mileage or anything, but I don't see how it wouldn't add about 5-10 mpg's as long as youre not in the throttle all the time.
jrm81bu- It's not about a/f ratios, it's about how much power you're getting. More hp = more fuel. Do I really need 23.1# injectors on my v6 truck when the v8's have the exact same 23.1#/hr? It's all in the computer tune. I could downgrade injectors on the truck and have it tuned for the same power (if those damn GM ls series spider injector setups would let me). But then again, a v8 or big v6 needs a lot of power, don't think you could get away with something like this on those engines. But we're talkin about a little 1.3-1.5 L
here's something to think about too - most newer stock engines can run a small s/c setup with stock fuel system at around 6psi. This means your injectors are usually bigger than needed. To me that's efficiency that's gone to waste.
first thing to remember, injectors are pulse width modulated, their firing time is controlled to the microsecond. if the computer is tuned to deliver less fuel, the injectors fire for a shorter time (or not at all), smaller injectors won't do anything.
2nd; larger injectors are less efficient, only if majorly oversized, or run at the wrong pressure. or if it's a race car, with HUGE injectors, at low speed. then it's like running a garden hose through a fire hose. instead of an atomizing spray, you get dribbles.
3rd; atomization is very important, if you up the fuel pressure (within system constraints) then you improve efficiency (and emissions). this can actually be more important than fuel volume. look at some of the new cars coming out with direct injection. this keeps the fuel from spraying on the intake valve and condensing/dripping. and they're running multiple injection events to properly mix the fuel.
4th; ENGINE DAMAGE!!!!!!!!!!!! remember, too lean is too freakin lean. thiings burn out very quickly.
some new cars can go to 22:1 for short periods of time, but that's due to the precise control of everything. older systems will not be able to do that. and you have to have a good EGR system.
here's an ironic bit of "info". on my vw TDI (turbo direct injected diesel), when i went to larger injectors (actually they're nozzles, but the concept is the same) my MPG's and power increased.
2nd; larger injectors are less efficient, only if majorly oversized, or run at the wrong pressure. or if it's a race car, with HUGE injectors, at low speed. then it's like running a garden hose through a fire hose. instead of an atomizing spray, you get dribbles.
3rd; atomization is very important, if you up the fuel pressure (within system constraints) then you improve efficiency (and emissions). this can actually be more important than fuel volume. look at some of the new cars coming out with direct injection. this keeps the fuel from spraying on the intake valve and condensing/dripping. and they're running multiple injection events to properly mix the fuel.
4th; ENGINE DAMAGE!!!!!!!!!!!! remember, too lean is too freakin lean. thiings burn out very quickly.
some new cars can go to 22:1 for short periods of time, but that's due to the precise control of everything. older systems will not be able to do that. and you have to have a good EGR system.
here's an ironic bit of "info". on my vw TDI (turbo direct injected diesel), when i went to larger injectors (actually they're nozzles, but the concept is the same) my MPG's and power increased.
Custom 442- your anology of replacing a 700 cfm carb with a 350 cfm carb is not acurate. What you' re talking about doing with halfing the injector size is more accurately compared with taking that 700cfm carb a halfing the size of the jets. This is what makes it about a/f ratios. You want to cut the fuel in half without a provision for cutting the air in half. Its not likely that you will be able to cruise at the same rpm, with half as much gas and the same amount of air. What that will end up doing is increasing the the throttle input which will bring up your fuel usage to keep the motor happy(ie. safe a/f ratios) cruising at that same rpm.
And i'm not sure if you seen my responce to something you said to kingcolbert. My responce there should cover your idea of not wanting to have to always think about feathering the pedal.
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
If that's all you want to do, get a ac solenoid(the thing used to kick up the idle speed, I think thats what its called), and install it backwards so that it limits how throttle you have when its powered and then flip the switch to give yourself full throttle.
And i'm not sure if you seen my responce to something you said to kingcolbert. My responce there should cover your idea of not wanting to have to always think about feathering the pedal.
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
If that's all you want to do, get a ac solenoid(the thing used to kick up the idle speed, I think thats what its called), and install it backwards so that it limits how throttle you have when its powered and then flip the switch to give yourself full throttle.
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