oh but it could, when the car is in gear the wheels are connected directly to the engine. 1 engine revolution -> transmission multiplication -> X number of wheel turns, It can also go the other way. One wheel turn -> transmission -> x number of engine turns.

This same princable causes stalls, if the wheels are directly connected to the engine (car in gear) and the wheels are not turning, then the engine is not able to turn and so the engine stalls.

You also should be able to use engine breaking with the car off and no gas going to the engine. If you roll down a hill with the car off, and put it in gear the engine will turn and that resistance will slow down the car.

 

Agree with JSVH on this, however I think that it will use slightly more fuel (negligible perhaps) because when you downshift the engine will obviously suck more air, and shouldn't it then require bit more fuel just to keep the mixture from becoming to lein?

 

also, im not sure how many of you know this, but in terms of AFR the motor runs richer at idle [also at WOT] in order to keep the car from stalling. Also, like people have already said, fuel consumption is NOT proportional to engine speed. Further complicating the matter, at high RPM, closed throttle [when decelerating] the engine uses vacuum-type spark advance timing. Regardless, it is NOT smart to put the car in nuetral and use the foot-brakes at speed to slow down. Downshift through the gears [not needed from 2nd to 1st at slow speed] to slow the vehicle down, engine braking is a smarter and safer way to decelerate. Remember, your car was designed to do this. Properly downshifting in combination with foot braking to match revs will not cause much wear on your clutch. The brakes, would however have alot more wear, braking down to a stop from a higher speed which might even warp your rotors from all the heat. Replacing all four rotors versus a bit more wear on your clutch, which one do you think is worse?

 

Good post, JSVH.
the engine will not suck in more air when you downshift if the throttle is closed, this is what causes the vacuum, the engine sucking, but no air coming, lack of air causing the vacuum.

 

this will never end, and I know what the answer is. :o hahahahahahaha

 

JSVH is correct. I was trying to think of a good example that proved this point, and he beat me to it. You can use engine braking with the vehicle *off*. That is, there is no gas going to the engine. And as he says, if the wheels are turning and the car is in gear, then the engine is going to turn as well, That's just what gears do. No getting around that.

I also take issue with llltc's comment that "when you downshift the engine will obviously suck more air". Maybe this is obvious to him, but I... don't see it. Tell me why the engine will "obviously suck more air" (this is a fuel-injected engine, not carbureted, remember) when you downshift.

The *only* reason I can think of that you would consume more gas downshifting would be if you were double-clutching each downshift. That is, if you were to clutch, go into neutral, release clutch, rev to match rpms of new gear, clutch, enter gear, release clutch. This is done while downshifting to reduce clutch wear and reduce the shock the chassis receives from downshifting. In other words, whoever wrote Vin Diesel's line in Fast and Furious had no idea wtf he was talking about, because that was a straight race w/ no downshifts. Morons.

 

Yeah I don't know what I was thinking here....

 

So then answer it!!!!

 

would you mind sharing it with us?

 

The Injectors are "off" On deceleration or 0% throttle. If you were to match revs it would only supply the fuel the injectors were told to supply during certain values from certain sensors. Keep in mind that each instance is different; therefore the 'stability' of fuel consumption depends on acceleration, not deceleration. How hard you "drive" the car, what components you modify, the way your ECU sets fuel trims, how your car is tuned out side of the OEM program (if applicable) and a myriad of atmospheric conditions play their own part in MPG/Fuel Consumption. I just think this point is mute, that is all. Drive the way you NEED to drive for each situation, and give the gas man the finger.

 

BTW, it's moot, not mute.

 

So you are positive that the injectors are completly off on decelration? What about when sitting at a red light or just coasting in neutral, the injectors are not "off" then are they?b Something has to be keeping the engine idling.

 

Thank you! (not being sarcastic) What's worse is when people say "for all intensive purposes." wtf?!

 

This is the single most amazing kernel of automotive knowledge I think I have ever read. "The injectors inject fuel when told to do so." I, for one, would have never guessed this. I know I'm being rude, I apologize. Delete this if you like, mods. I couldn't help it. It's just that.... for someone who just proudly proclaimed to have all the answers, his post is surprisingly lacking in technical detail, and instead just tosses out some lingo. Hate to be the one to insult a "titanium sponsor," but that's what I read in that post: a bunch of mumbo jumbo.

 

Good point. Yes, the injectors are off in deceleration under engine braking conditions, until you push in the clutch, push the gas, or the car goes into an idle condition.

 

im going to drive to / from work each way and see which way gets better mpg.

I will do each for 5 days.

I stop frequently from 4th/5th gear, so if there is a difference, then I will see it.

Which one you guys wanna see first? Downshifting or neutral coasting

 

So if this is true you actually use LESS gas by downshifting becasue if you were to brake to a stop in neutral then your injectors would never really be "OFF".

Now not to dispute your credibility but what references can you provide. I have other people telling me otherwise.

 

http://turboxs.com/dealers.htm#sectTuner
Go to this site if you wish and call anyone in their dealer list and ask about us.
http://www.hondata.com/contact.html
Call Hondata as well, we are one of their most respected tuners/dealers.
http://www.honda-challenge.com
Or this racing series we sponsor along with some of its top drivers.
http://www.spoonsports.co.jp
Or call Spoon Sports Of Japan as for Yuki Imamura the Chief Operating Officer.
http://opakracing.com/home.htm
Or you can call Opak Racing

Any of these and many others can vouch.
And I will not comment about the rest of the companies we have trained with 'on site', or the countless cars we have built/tuned, or the fact that we have our very own IN HOUSE AWD Dynapack 5000 chassis dyno and MODIS W/ full scopes. I hope this quells your BS Meter.

I really hate these kinds of topics. They never solve anything.

If not here are some Pics...















No disrespect.
:D

 

Man give me a break...I can get my grandma to stand next to my car that doesn't make me an expert. I don't need to call Spoon supervisor in Japan either, all I was asking is if you were sure since the 35 posts before you obviously nobody had a sure answer. No need to take the ego hit because we didn't all bow at your feet, if your right your right, I never claimed I knew the correct answer that's why I ASKED THE QUESTION.

No disrespect either just calm down your ego meter.

 

No ego, you asked for the references. Just highlighting. I like to be proud of what our team has accomplished, if you took it a me trying to flame you I am truly sorry. I was merely trying to convey our zeal toward what you were you were trying find out about us. We don’t tolerate internet trolls who like to start ____, so we may come off brash at times but please don't misunderstand our true meaning.


*edit*
The pics are just some fun shots from the last couple of weeks, not ment to prove more than the fact that KPI is not full of shi*.