Down Shifting In An Auto
#21
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I'll try this one more time
look at it this way.... if your foot is off the accel and you are engine braking and if what you say is true that more fuel is being introduced then answer this....
what is happening to that fuel? is it being burned? if it is then where's the extra power that you would expect? remember... more fuel and more air equals power. Last time I engine braked it slowed the car down not sped it up due to increased power.
So... then we have to assume if what you are saying is true, that more fuel is introduced during engine braking, and the engine is not producing power (of course it's not... that's why engine braking works) then that fuel is not being burned.... you did say earlier that the spark plugs don't fire during engine braking..... another ridiculous claim.
That's crazy because that would mean the engine would be running extremely rich with raw fuel passing though.... can you say fouled plugs??
The ECU WILL NOT LET THIS HAPPEN!
are you seriously saying that fuel delivery is proportional to engine RPM???
the whole point of engine braking is to let the compression and drag of the engine slow the car down..... if more fuel was being used during this process the engine would be producing power negating the engine braking effect.
do some research guys..... educate yourselves before acting like you know it all.
install an A/F meter and try some engine braking. you'll soon find out that your A/F ratio stays the same.... if anything it may get a little leaner.... this is why the O2 sensor exists..... if too much fuel is being put through and not being burned it is detected and the mixture adjusted accordingly.... if it didn't our cars would never pass our strict emissions laws.
look at it this way.... if your foot is off the accel and you are engine braking and if what you say is true that more fuel is being introduced then answer this....
what is happening to that fuel? is it being burned? if it is then where's the extra power that you would expect? remember... more fuel and more air equals power. Last time I engine braked it slowed the car down not sped it up due to increased power.
So... then we have to assume if what you are saying is true, that more fuel is introduced during engine braking, and the engine is not producing power (of course it's not... that's why engine braking works) then that fuel is not being burned.... you did say earlier that the spark plugs don't fire during engine braking..... another ridiculous claim.
That's crazy because that would mean the engine would be running extremely rich with raw fuel passing though.... can you say fouled plugs??
The ECU WILL NOT LET THIS HAPPEN!
are you seriously saying that fuel delivery is proportional to engine RPM???
the whole point of engine braking is to let the compression and drag of the engine slow the car down..... if more fuel was being used during this process the engine would be producing power negating the engine braking effect.
do some research guys..... educate yourselves before acting like you know it all.
install an A/F meter and try some engine braking. you'll soon find out that your A/F ratio stays the same.... if anything it may get a little leaner.... this is why the O2 sensor exists..... if too much fuel is being put through and not being burned it is detected and the mixture adjusted accordingly.... if it didn't our cars would never pass our strict emissions laws.
Last edited by N74DV; 10-21-2003 at 10:38 PM.
#22
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Originally posted by N74DV
I'll try this one more time
look at it this way.... if your foot is off the accel and you are engine braking and if what you say is true that more fuel is being introduced then answer this.... blah blah blah
I'll try this one more time
look at it this way.... if your foot is off the accel and you are engine braking and if what you say is true that more fuel is being introduced then answer this.... blah blah blah
You are trying to argue based on knowledge you have without knowing the truth. This is a quote from GMs website under how to improve fuel economy:
Accelerate evenly: Start evenly from a standstill. Avoid rapid acceleration, over-revving your engine and transmission downshifting. Rapid acceleration can cost up to 12 mpg.
During engine braking fuel is used at a lesser rate but more than at idle. If the fuel is not kept at a reasonable rate then the engine will lean out too much and cause preignition damage and a very hot cylinder.
During any engine operation the lean/rich condition is trimmed by the O2 sensor and will prevent the lean condition from occurring.
So, is fuel used: yes. Is more used than at idle: yes. Will this hurt your fuel economy: yes.
During any engine operation the lean/rich condition is trimmed by the O2 sensor and will prevent the lean condition from occurring.
So, is fuel used: yes. Is more used than at idle: yes. Will this hurt your fuel economy: yes.
do some research guys..... educate yourselves before acting like you know it all.
You are wrong!!!!!
#23
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Originally posted by N74DV
I'll try this one more time
look at it this way.... if your foot is off the accel and you are engine braking and if what you say is true that more fuel is being introduced then answer this....
what is happening to that fuel? is it being burned? if it is then where's the extra power that you would expect? remember... more fuel and more air equals power. Last time I engine braked it slowed the car down not sped it up due to increased power.
I'll try this one more time
look at it this way.... if your foot is off the accel and you are engine braking and if what you say is true that more fuel is being introduced then answer this....
what is happening to that fuel? is it being burned? if it is then where's the extra power that you would expect? remember... more fuel and more air equals power. Last time I engine braked it slowed the car down not sped it up due to increased power.
So... then we have to assume if what you are saying is true, that more fuel is introduced during engine braking, and the engine is not producing power (of course it's not... that's why engine braking works)
then that fuel is not being burned.... you did say earlier that the spark plugs don't fire during engine braking..... another ridiculous claim.
That's crazy because that would mean the engine would be running extremely rich with raw fuel passing though.... can you say fouled plugs??
The ECU WILL NOT LET THIS HAPPEN!
are you seriously saying that fuel delivery is proportional to engine RPM???
The ECU WILL NOT LET THIS HAPPEN!
are you seriously saying that fuel delivery is proportional to engine RPM???
the whole point of engine braking is to let the compression and drag of the engine slow the car down
..... if more fuel was being used during this process the engine would be producing power negating the engine braking effect.
The reason I like to engine break, is that it takes work away from the break pads. When you break, the work (friction, MxA) needed to slow the car down has to come from somewhere. I prefer the work load be balanced between my engine and my break pads.
do some research guys..... educate yourselves before acting like you know it all.
install an A/F meter and try some engine braking. you'll soon find out that your A/F ratio stays the same.... if anything it may get a little leaner.... this is why the O2 sensor exists..... if too much fuel is being put through and not being burned it is detected and the mixture adjusted accordingly.... if it didn't our cars would never pass our strict emissions laws.
Lets say that at 3000 RPMs, the car sucks down 1.5 cubic feet of air per second, and simultaneously it sucks down .1 gallons of fuel per second. Your A/F ratio would be 15.
NOW ... lets say the car is still engine breaking, but it is now at 1000 RPMs. Because it is at a lower RPM, it sucks in less air per second ... say .8 cubic feet per second. At this RPM, the engine needs less fuel, so it is only sucking in .053 gallons per second. The ratio is still 15, and yet the car is consuming less fuel at a lower RPM then it would at a higher RPM.
You get it?
#24
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yada yada yada......... ask your nissan service tech the next time you see him. then come back and post how I was right.
or for a lesson on EFI read this
http://www.edmunds.com/ownership/tec...3/article.html
no $hit sherlock.... but it also would show a rich condition as if excessive fuel were entering the cylinders during engine braking. If the fuel were not burned with the proper amount of air the mixture would be rich..... a lower A/F reading like this would be sensed by the ECU and fuel delivery would be reduced.
maybe we are arguing at two ends of a stick.... I'm saying a noticeable reduction in fuel economy will not be realized..... I think you think I'm saying zero fuel is burned during engine braking..... which I am not.
or for a lesson on EFI read this
http://www.edmunds.com/ownership/tec...3/article.html
A/F is a RATIO ... not a linear representation of how much fuel is going into the engine
maybe we are arguing at two ends of a stick.... I'm saying a noticeable reduction in fuel economy will not be realized..... I think you think I'm saying zero fuel is burned during engine braking..... which I am not.
Last edited by N74DV; 10-22-2003 at 07:24 AM.
#25
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Originally posted by N74DV
no $hit sherlock.... but it also would show a rich condition as if excessive fuel were entering the cylinders during engine braking. If the fuel were not burned with the proper amount of air the mixture would be rich..... a lower A/F reading like this would be sensed by the ECU and fuel delivery would be reduced. How can you not see this??
no $hit sherlock.... but it also would show a rich condition as if excessive fuel were entering the cylinders during engine braking. If the fuel were not burned with the proper amount of air the mixture would be rich..... a lower A/F reading like this would be sensed by the ECU and fuel delivery would be reduced. How can you not see this??
If you could pull your head out of your a$$ for two seconds and realize that you are dead wrong, this argument would end. Swallow your pride for once, and admit that you either mis-read the argument, or that you are simply too damn stupid to understand english.
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if you would read what the dude first posted that staretd this..... he said engine braking wastes gas.. to me wasting gas means a lower fuel economy is realized.
I still say it's not.
I'm done this time...... I promise.
I still say it's not.
I'm done this time...... I promise.
Last edited by N74DV; 10-22-2003 at 07:46 AM.
#28
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Originally posted by N74DV
if you would read what the dude first posted that staretd this..... he said engine braking wastes gas.. to me wasting gas means a lower fuel economy is realized.
I still say it's not.
I'm done this time...... I promise.
if you would read what the dude first posted that staretd this..... he said engine braking wastes gas.. to me wasting gas means a lower fuel economy is realized.
I still say it's not.
I'm done this time...... I promise.
I too am done with this.
#29
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when you downshift, engine revs higer due to momentum and shorter gear.
Is this a Civic forum? Are we girls? I can't believe we are even discussing this.
Ask your local mechanic.
Is this a Civic forum? Are we girls? I can't believe we are even discussing this.
Ask your local mechanic.
#30
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Getting back to the original question
I have an 04 Touring Roaster with the 5AT. I'm not worried that manual downshifting is really hurting anything, keeping in mind that I'm not banging downshifts to go from 2k to 6k rpms either. Most of my around town driving is in "D". I go to the manual mode whenever I'm on the twisties, so the tranny doesn't hunt through the gears right in the middle of a corner. If you have ever tried to run your Z in "D" on a twisty road, you'll know it's pretty awful. Gotta use the manual here. Also, sometimes I will switch to the manual mode in city driving for a burst of acceleration. I don't like the way the "D" mode does it's downshifts when you are hard on the gas, and it shifts into too high a gear to soon. I'd rather downshift manual then hit the gas and shift manually through the gears. It is smoother that way. Once I get up to speed and on my way, I go back to "D" mode. I really like the way it works, even though an auto on a sportscar is kinda "gey" (jk). I also, like the way when you flip to manual mode from "D", it automatically shifts down one gear(the engineers must have figured if you are going to manual, you are needing some accel), then you bang a 2nd quick downshift manually. You can get down two gears quicker than just letting the auto do it in "D". As for hard accel off the line, just leave it in "D" (TCS off) and hit it. Perfect shifts at redline everytime.
I have to agree that if you are using the auto in manual mode almost all the time, then yes, it probably wasn't designed to be used this way, and the 6MT would have been your best choice. I like to think of the manual mode in the 5AT, as something to keep in reserve. Use it when you need it, and then go back to the "normal" driving mode.
I have to agree that if you are using the auto in manual mode almost all the time, then yes, it probably wasn't designed to be used this way, and the 6MT would have been your best choice. I like to think of the manual mode in the 5AT, as something to keep in reserve. Use it when you need it, and then go back to the "normal" driving mode.
#31
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Re: Getting back to the original question
Originally posted by ShaftEd
I have to agree that if you are using the auto in manual mode almost all the time, then yes, it probably wasn't designed to be used this way, and the 6MT would have been your best choice. I like to think of the manual mode in the 5AT, as something to keep in reserve. Use it when you need it, and then go back to the "normal" driving mode.
I have to agree that if you are using the auto in manual mode almost all the time, then yes, it probably wasn't designed to be used this way, and the 6MT would have been your best choice. I like to think of the manual mode in the 5AT, as something to keep in reserve. Use it when you need it, and then go back to the "normal" driving mode.
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