I was wondering whether throttle position or engine RMP has a greater influence on the amount of fuel the engine uses at a time. Would running low rmp but WOT use more fuel than high rpm but less on the gas pedal? I was just thinking about things and the question kindof came up in my mind

 

Just a guess: But since the fuel maps in our ECU's are really called Volumetric Efficiency maps, I would tend to believe that at the highest VE points [high means that a lot of air is coming in], then more fuel would be needed.

Anyone else?

 

It would also have to do with the current weather, at any given time... Depending on what the MAP, Atmosphric Pressure, and to some extent the O2 sensors. Were reading into the ECU, along with some others too.... Then the ECU would choose from the above mentioned tables. What the correct injetor pulse width (PW) would be, at the "any given time"....


[Modified by 88_SC_CRX_Si, 6:44 AM 8/21/2002]

 

low rpm wot would be my guess

edit: spelling


[Modified by innate, 12:35 PM 8/21/2002]

 

that would be my guess as well, but then I thought about it like this. *given that all conditions are equal*, if you rev from 2k to 4k (under no load) your fuel usage doubles because each piston is firing twice as many times and is using just the amount of fuel needed to keep the internals moving at that speed.

now say you're revving at 2k but under a load, so that you have to maintain WOT to keep at that point. in order for the fuel usage to surpas that of what would be used by reving up to 4k the engine would have to compress over twice as much air into the piston to match the volume of fuel injected. If you make the comparison even wider, like 2k to 8k is where I wonder, could an engine running only at 2k, even at WOT, take in 4 times as much air as when it was revving 2k in the previous gear with the throttle closed much more?

It's really late and I think my thoughs my be really confused. I'll see if I need to clarify any in the mornin

 

sorry that dosent make any sense to me

more rpm=more fuel consumption
its simple
every revoultion the injector opens and lets fuel in, if you increase the revs, you increase the fuel consumption.

running WOT will make you accelerate and burn fuel but you cant sit at 4000 rpm and WOT so that is impossible to use as an example.

 

but as you accelerate the engine first needs to use more fuel to push it faster. the heavier a load it has to work agains the more work, and so more fuel it has to use to push up the speed.

I can keep it floored in 5th gear up a slight incline and not accelerate at all, usually betweek 2.5 and 3k on my engine. My thought is, how would it compare trying to force the engine to higher RPM, or shifting to a lower gear and revving higher, but being able to let off the throttle.

I agree RPM now, but how much does throttle affect it?
hmm

 

The ecu attempts to maintain a good Air/Fuel ratio. What ever the MAS/MAP sees is in relation to how much fuel the ECU tells the injectors to send.

 

damn, you guys boogle my mind!! keep it up.

 

revving the engine at 4K no load and 8K no load the fuel comsumption would be roughly double (injector fires twice as often) . If the engine is running steady-state down the freeway at 4K and you floor it the injector pulsewidth doubles. The best fuel economy to me is a tradeoff. If you have to accelerate then the best method woudl allow the car to remain in the lower gears longer with a light throttle setting. "lugging" the engine upps the injector pulsewidth which results in more fuel burn, and also for a longer duration as the car accelerates more slowly when "lugged down". Think ogf the total load on the engine. allowing it to remain in 3rd gear until 4500 RPM with a light throttle setting, as it nears 4 grand the load on the engine is reduced. just some thoughts.