while me, boobies, feersty, and mike were riding back from VIR, mike kept telling me i didnt need to downshift going uphill, even if the engine was bogging. his reasoning was that downshifting only uses more fuel. i said no way, but mike insisted that fuel was added relative to rpm (mike, correct me if i quoted you wrong on that). needless to say i didnt downshift much to avoid getting yelled at :lol:
my understanding has always been that fuel is added based on throttle position, not rpm. as an example, if fuel were added based on rpm, an engine couldnt function, because as soon as you were to open the throttle, the fuel mixture would instantly go lean and the engine would die. also, by that logic, a civic SI, for example, would get horrendously bad highway gas milage because it sits at about 4500 rpm at a decent cruise.
please correct me if i'm wrong but im almost positive fuel is added to the engine based on increasing throttle position, not rpm. if this is the case, than if im going up a hill, and i have to use alot of throttle to keep the engine from bogging, than that is less efficient than downshifting to a higher rpm (which is better placed in the powerband) which would use less fuel since my engine makes more power at higher rpm, necessitating less throttle to achieve the same speed. everyone with me?
2010 Civic Si
2019 4Runner TRD Off-Road
--------------------------
Past: 03 Xterra SE 4x4 | 05 Impreza 2.5RS | 99.5 A4 Quattro 1.8T | 01 Accord EX | 90 Maxima GXE | 96 Explorer XLT
Low RPM + high load = less fuel use
High RPM + low load = more fuel use
(09-25-2019, 03:18 PM)V1GiLaNtE Wrote: I think you need to see a mental health professional.
cool, good to know that.
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hmmmm....i'm still kind of confused.
so at low rpm/low load, like on the highway, i would be using up more fuel than if i was at low rpm/ high load?
2010 Civic Si
2019 4Runner TRD Off-Road
--------------------------
Past: 03 Xterra SE 4x4 | 05 Impreza 2.5RS | 99.5 A4 Quattro 1.8T | 01 Accord EX | 90 Maxima GXE | 96 Explorer XLT
i've never owned a carbeurated engine so i dont know shit about them, but on fuel injection, you're both kinda right. with modern computers, it will pump fuel based on throttle position in order to mix fuel and air and go boom. engine speed (rpm) also affects it, as if it goes "boom" more times per minute, then more fuel is used.
1994 Ford Ranger
2004 Honda S2000
2007 BMW X3
Maengelito Wrote:i've never owned a carbeurated engine so i dont know shit about them, but on fuel injection, you're both kinda right. with modern computers, it will pump fuel based on throttle position in order to mix fuel and air and go boom. engine speed (rpm) also affects it, as if it goes "boom" more times per minute, then more fuel is used.
yeah, i've always kinda understood it like that too. its just that i figured low rpm/high load and high rpm/low load would be about the same in fuel use (the latter choice being a little better), the difference being that the latter choice would allow easier acceleration because it would be in a more favorable powerband.
2010 Civic Si
2019 4Runner TRD Off-Road
--------------------------
Past: 03 Xterra SE 4x4 | 05 Impreza 2.5RS | 99.5 A4 Quattro 1.8T | 01 Accord EX | 90 Maxima GXE | 96 Explorer XLT
who would dare question me? :evil: 
I Am Mike
4 wheels: '01 RAV4 (Formerly '93 Civic CX, '01 S2000, '10 GTI, '09 A4 Avant)
2 wheels: '12 Surly Cross-Check Custom | '14 Trek Madone 2.1 105 | '17 Norco Threshold SL Force 1 | '17 Norco Revolver 9.2 FS | '18 BMC Roadmachine 02 Two | '19 Norco Search XR Steel (Formerly '97 Honda VFR750F, '05 Giant TCR 2, '15 WeThePeople Atlas 24, '10 Scott Scale 29er XT, '11 Cervelo R3 Rival, '12 Ridley X-Fire Red)
No longer onyachin.
MichaelJComputer Wrote:who would dare question me? :evil:
dems fightin werds
2010 Civic Si
2019 4Runner TRD Off-Road
--------------------------
Past: 03 Xterra SE 4x4 | 05 Impreza 2.5RS | 99.5 A4 Quattro 1.8T | 01 Accord EX | 90 Maxima GXE | 96 Explorer XLT
Quote:it will pump fuel based on throttle position in order to mix fuel and air
What the hell? Not one of you guys came close to what a fuel injected car does for calculating fuel...and when it comes to talking about what a carbuerated car does...uh, that stuff is old anyway.
Fuel injected cars have an ECU (engine control unit) which aside from a million other functions stores fuel maps that determine how long the fuel injectors will be open based on (I'm simplifying it) the air coming into the engine.
Throttle position has nothing to do with this, except that when you push down on the 'gas pedal' (which only regulates air) the throttle body opens up allowing more air to enter the engine. The ECU will take into account throttle position which can help it anticipate airflow, and will look at the o2 sensor(s) to see what corrections over time need to be made.
Air is measured by something like a MAF/MAS (Mass Airflow Sensor) or a MAP (Manifold Absolute Pressure Sensor) and it is not measured based on time, but on airflow per rpm.
Now, if I made some kind of glaring error slap me and correct it but reading it over I think I gave a good simplified version of how a fuel injected car determines fuel consumption.
So basically...it is more complex than simply high load/low rpm or low load/low rpm and without some kind of logging ability you'll never be certain.
-T
MIHS - hot cause we fly you ain't so you not
2004 Subaru WRX STi
1999 Mitsubishi Eclipse GSX
1998 Oldsmobile Cutlass
KPWSerpiente Wrote:So basically...it is more complex than simply high load/low rpm or low load/low rpm
Yes its more complex, but my statement about fuel use is correct. Sorry to simplify too much 
(09-25-2019, 03:18 PM)V1GiLaNtE Wrote: I think you need to see a mental health professional.
did he really just spell out what ECU means?
Evan Wrote:did he really just spell out what ECU means?
Some call it PCM.
Or EEC.
Or...
(09-25-2019, 03:18 PM)V1GiLaNtE Wrote: I think you need to see a mental health professional.
.RJ Wrote:Evan Wrote:did he really just spell out what ECU means?
Some call it PCM.
Or EEC.
Or... point being, even my damn girlfriend knows what ECU stands for. not breaking new ground here
Quote:did he really just spell out what ECU means?
Yes, I did. When I originally wrote it up I didn't but I decided if I was going to explain all the other ones, why expect people to know that.
Quote:High RPM + low load = more fuel use
Quote:Yes its more complex, but my statement about fuel use is correct. Sorry to simplify too much
I disagree. If you want I will go out and log a million places where high rpm with a lower load will produce less airflow and lower injector duty cycle. But because I have not done this, and I doubt you you have to blankly state it one way or the other is not going to to be correct.
-T
MIHS - hot cause we fly you ain't so you not
2004 Subaru WRX STi
1999 Mitsubishi Eclipse GSX
1998 Oldsmobile Cutlass
Do it, I'd like some real numbers so we can put this to rest one way or the other.
I Am Mike
4 wheels: '01 RAV4 (Formerly '93 Civic CX, '01 S2000, '10 GTI, '09 A4 Avant)
2 wheels: '12 Surly Cross-Check Custom | '14 Trek Madone 2.1 105 | '17 Norco Threshold SL Force 1 | '17 Norco Revolver 9.2 FS | '18 BMC Roadmachine 02 Two | '19 Norco Search XR Steel (Formerly '97 Honda VFR750F, '05 Giant TCR 2, '15 WeThePeople Atlas 24, '10 Scott Scale 29er XT, '11 Cervelo R3 Rival, '12 Ridley X-Fire Red)
No longer onyachin.
remember though, not downshifting up a hill... under a load and you start bogging down... your clutch wont like it much... course i am the king of clutch riding..
more load = more strain on seals...
jack is willing to spend money on gas
i mostly started this thread just to get some good conversation going, but thanks for all the replys everyone. my driving style pretty much won't change, but i have definitely learned some things.
2010 Civic Si
2019 4Runner TRD Off-Road
--------------------------
Past: 03 Xterra SE 4x4 | 05 Impreza 2.5RS | 99.5 A4 Quattro 1.8T | 01 Accord EX | 90 Maxima GXE | 96 Explorer XLT
Kaan Wrote:remember though, not downshifting up a hill... under a load and you start bogging down... your clutch wont like it much... course i am the king of clutch riding..
I'm referring to times at which being in the hire (bahahah i said "hire")gear won't bog the motor down at all, scott was downshifting at like 2500rpm to go up a hill.
I Am Mike
4 wheels: '01 RAV4 (Formerly '93 Civic CX, '01 S2000, '10 GTI, '09 A4 Avant)
2 wheels: '12 Surly Cross-Check Custom | '14 Trek Madone 2.1 105 | '17 Norco Threshold SL Force 1 | '17 Norco Revolver 9.2 FS | '18 BMC Roadmachine 02 Two | '19 Norco Search XR Steel (Formerly '97 Honda VFR750F, '05 Giant TCR 2, '15 WeThePeople Atlas 24, '10 Scott Scale 29er XT, '11 Cervelo R3 Rival, '12 Ridley X-Fire Red)
No longer onyachin.
what he said. i definitely didnt absolutely have to downshift
2010 Civic Si
2019 4Runner TRD Off-Road
--------------------------
Past: 03 Xterra SE 4x4 | 05 Impreza 2.5RS | 99.5 A4 Quattro 1.8T | 01 Accord EX | 90 Maxima GXE | 96 Explorer XLT
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