In reply to wbjones:
Indeed. It can't be true zero without a stop start system.
In reply to wbjones:
Indeed. It can't be true zero without a stop start system.
No, it wouldnt stall, the torque converter is locked, thus the engine is being driven by the trans, that is being driven by momentum of the car. The RPM's dont drop of because its a mechanical connection. That's why its down shifting as well, to keep the rpm high enough to prevent vibration, and to allow fuel cut for as long as possible. Once you run out of enough speed, the torque converter will unlock, injectors will begin to cycle, and as the engine decelerates near 1500 rpm or so, it resumes normal idle.
In reply to TGMF:
He said it was a 6 spd manual in neutral.
They don't have torque converters, and there is no mechanical connection to the road.
wbjones wrote: now for the rest of the question … if I've just filled up (this assumption so that the instant milage read out will change more quickly) in my new Sonic the milage will go up more quickly if I shift to neutral (6sp manual) than if I lift throttle and just roll up to the stop sign … in the latter, the tach stays up (which is where y'all are saying there's no fuel flow) .. if I shift to neutral the tach shows ~ 600 rpm all the way to stop …engine obviously running …
Sure its running. If you left it in gear, the injectors would go to a zero duty cycle until the engine rpm dropped enough. In neutral, its burning fuel to keep running. Your fuel economy dashboard doodad is just a plaything to entertain bored drivers.
Really. Honest to God. Seriously. For well over 40 years now. On every EFI car I have ever encountered. Its true. No fuel delivery coasting in gear with closed throttle. As God is my witness. On my mothers grave, I swear. May I be struck by lightning if I am attempting to deceive. If I'm lyin, I'm dyin.
G_Body_Man wrote: In reply to wbjones: Indeed. It can't be true zero without a stop start system.
that was my thinking … I realize that some vehicles out there do this … I don't thing a base model Fit or a LT model (manual) Sonic is in this category
In reply to Streetwiseguy:
but I am willing to be convinced … well sorta .. I've had some pretty darn good mechanics that say nope …
nor do I have much faith in GM being this good with something like the Sonic … we ain't talking about one of their top of the line vehicles with the stop start system … shrug
by that I mean, I have trouble believing they would put that much work into making it as seamless as it seems to be … I can't feel/hear it regardless whether I roll to the light still in 6th, or in neutral …
and for that matter I can't feel/hear it in Mom's automatic Fit … again shrug
even if the ECU would show zero duty cycle, can there still be a "trickle" of fuel passing ?
wbjones wrote:bigev007 wrote: In reply to wbjones: Yup, actually zero. If you have an 'instant mileage' gauge, you can see it go to zero...or max. Depending on how or what it reads. Sometimes you can feel it kick back on.if no fuel flow, wouldn't the engine stop turning over ? I'm in neutral, so no pull from the drive train to make the engine turn over … wouldn't being stopped, with no movement at all bring on the same effect ?
I think we are mixing the situations.
You are asking if you can coast to a stop in neutral. The answer to that is- yes, you can. When you do, the engine will return to a neutral idle speed. And while you slow down, the only fuel used is to keep the engine and the ancillaries spinning.
One of the replies is "why" because if you leave the engine in gear, while you lift off the throttle, the fuel shuts off. The engine keeps spinning because the inertia of the car spins the transmission, and it being still connected to the engine, the engine spins. The ancillaries are driven by the car still moving, and no fuel is used. Eventually, the fuel turns back on so that it does not stall as you come to a stop. (then my suggestion is to manually shift the trans, as you can downshift and keep the engine speed above the point where the fuel turns back on, thus using less fuel).
No fuel is less than idle fuel.
wbjones wrote: In reply to Streetwiseguy: but I am willing to be convinced … well sorta .. I've had some pretty darn good mechanics that say nope … nor do I have much faith in GM being this good with something like the Sonic … we ain't talking about one of their top of the line vehicles with the stop start system … *shrug* by that I mean, I have trouble believing they would put that much work into making it as seamless as it seems to be … I can't feel/hear it regardless whether I roll to the light still in 6th, or in neutral … and for that matter I can't feel/hear it in Mom's automatic Fit … again *shrug* even if the ECU would show zero duty cycle, can there still be a "trickle" of fuel passing ?
Non-linear actions in cars piss people off- so yes, the off and on is calibrated that well. And no, if there zero duty cycle, there is not trickle fuel- if there is, it won't burn, and that will completely burn up the catalyst in very short order.
I sorta understand … and I sorta understand when folk say the mpg read out on the dash is bogus … (not really, that's usually the comment when someone really doesn't know the answer … LOL )
like I said earlier, the milage will go up faster in neutral coasting up to the stop (this is in my manual Sonic … we've sorta gotten off topic about the "damage, if any" to Mom's auto Fit in neutral) than if left in 6th until I have to push in the clutch
alfadriver wrote:wbjones wrote: In reply to Streetwiseguy: but I am willing to be convinced … well sorta .. I've had some pretty darn good mechanics that say nope … nor do I have much faith in GM being this good with something like the Sonic … we ain't talking about one of their top of the line vehicles with the stop start system … *shrug* by that I mean, I have trouble believing they would put that much work into making it as seamless as it seems to be … I can't feel/hear it regardless whether I roll to the light still in 6th, or in neutral … and for that matter I can't feel/hear it in Mom's automatic Fit … again *shrug* even if the ECU would show zero duty cycle, can there still be a "trickle" of fuel passing ?Non-linear actions in cars piss people off- so yes, the off and on is calibrated that well. And no, if there zero duty cycle, there is not trickle fuel- if there is, it won't burn, and that will completely burn up the catalyst in very short order.
I can "maybe" accept that for the more recent vehicles .. but for those of 10 - 15 - 20 yrs ago .. and the BS computers they had then … that's harder to swallow 
In reply to wbjones:
Unlike all of street's cars- not all cars had instant fuel shut off 15-20 years ago. But eventually they all did- so going down hill, the fuel would shut off. Two reasons- one is to save fuel, the other is to save the catalyst. At very low throttles and high speeds, the engines don't run very well- at some point, the engine just misfires badly- which ends up burning up the cats. So it's better to just turn the fuel off to slow down. Some did turn if off immediately, others 5-6 seconds after a tip out.
Manuals have even other things they can do- some do shift fuel shut off. I wish more of them did- my Fiesta does not, and the speed that the engine slows down during shifts is way too slow.
Still, it's not that hard to turn the fuel on pretty seamlessly. Get to an engine speed that the combustion is good, turn it on with very retarded spark- and it still makes almost no torque.
The ECU's 25 years ago were just about as good as the best MS3 right now. 20 years ago- much better than anything you can get in the most of the aftermarket today. 15 years ago, way, way better as they could do funky VCT, electronic throttles, and some fancy trans controls. 10 years ago- we were doing very fast direct injection- I started working on that in 2004.
cwh wrote: I really don't know, but the owners manual for my 2010 Hyundai very clearly says do not do it. Very dangerous. Huh?
Well, if you coast in Neutral, you're that much closer to accidentally finding Reverse, which is not so much a good thing to do when at speed.
this is one of those conversations I hate having with people. You can literally watch people's brains melt trying to comprehend the difference between an engine driving a car and one being driven by the car's momentum. For many, it does not compute
failboat wrote: ^^^ what he said. sometimes it may engage smoothly enough. sometimes.....not. slightly off topic....while visiting my rather mechanically adept gearhead uncle I noticed he put his auto transmission cars in neutral at every stoplight, and would put it back into gear when it was time to move. No idea if that is supposed to ease strain on the transmission or what.
I do this too, but it has nothing to do with the transmission.
The brakes, for 99% of their life in a typical car, are at their hottest after bringing the car to a stop. That is also when, with an automatic car in gear, you're sitting there with your foot firmly clamping the hot pads to the hot rotors to keep the car from moving.
I've noticed over nearly 20 years of working on cars professionally that brake pulsation is pretty rare for manual trans cars. One of the causes of brake pulsation is uneven pad transfer to the rotors, which is caused by... what now?
So I throw my automatic cars into Neutral at lights, and enjoy brake rotors turned funny shades of blue and purple from other shenanigans but not any brake pulsations. I use the handbrake to hold the car if necessary.
alfadriver wrote:bigev007 wrote: In reply to SVreX: My understanding is that the injectors are fully shut off. I'm trying to find a source. It's definitely noticeable on my e36 (It runs rough, so when they kick back on you can notice it more than most cars) It's also obvious on my Civic, but that's a hybrid, so it operates a little different from most (it can actually cut 3 cyls or all 4).Theoretically, I can be a source. Staring at a test I ran this morning, injector pulse width is zero. And O2 in the exhaust goes from .8% to 20%. Very off. (but I can't post the data, so don't ask)
Mazda engineers actually wrote a SAE paper, IIRC, that involved this subject. When they incorporated the fuel cut on the FC RX-7, they couldn't just do a hard cut-out and cut-in, for drivability reasons they had to cut one rotor out before the other, and cut one rotor back in before the other. It's kind of like what they did in the 81-up carbureted models with the shutter valve cutting fuel-laden airflow to one rotor on deceleration.
Heck, the Bosch "Motronic" K-Jet (CIS-Lambda) on Audi 5000/200 models incorporated a valve that shut off fuel flow entirely when in deceleration.
Knurled wrote:cwh wrote: I really don't know, but the owners manual for my 2010 Hyundai very clearly says do not do it. Very dangerous. Huh?Well, if you coast in Neutral, you're that much closer to accidentally finding Reverse, which is not so much a good thing to do when at speed.
Honestly, if you can shift a 2010 Hyundai into reverse while going forward, and it actually tries to do that, Hyundai/Kia is doing it wrong. By 2010, the shifter is totally electronic in an auto car.
I know a trick calibrators liked to do is to shift into reverse on the highway- which did two things- freaked out the driver behind them (the reverse lights turn on) and turned on the rear camera- so you could see the car at your bumper at speed. The computer was smart enough not to actually shift anything.
really, I see no harm in a neutral coast down- we do that all the time.
Knurled wrote:alfadriver wrote:Mazda engineers actually wrote a SAE paper, IIRC, that involved this subject. When they incorporated the fuel cut on the FC RX-7, they couldn't just do a hard cut-out and cut-in, for drivability reasons they had to cut one rotor out before the other, and cut one rotor back in before the other. It's kind of like what they did in the 81-up carbureted models with the shutter valve cutting fuel-laden airflow to one rotor on deceleration. Heck, the Bosch "Motronic" K-Jet (CIS-Lambda) on Audi 5000/200 models incorporated a valve that shut off fuel flow entirely when in deceleration.bigev007 wrote: In reply to SVreX: My understanding is that the injectors are fully shut off. I'm trying to find a source. It's definitely noticeable on my e36 (It runs rough, so when they kick back on you can notice it more than most cars) It's also obvious on my Civic, but that's a hybrid, so it operates a little different from most (it can actually cut 3 cyls or all 4).Theoretically, I can be a source. Staring at a test I ran this morning, injector pulse width is zero. And O2 in the exhaust goes from .8% to 20%. Very off. (but I can't post the data, so don't ask)
My 1973 Alfa with SPICA had decel fuel shut off. It's a mechanical thing, but it did it.
Desmond wrote: How do you rev-match an auto? How do you know which gear it will choose?
It will/should choose the gear closest to the engine load, however the trans controller sees load. The GM trans algorithms that I'm familiar with go by TPS/MPH - if MPH is here and TPS is there, it goes into this gear.
My Volvo automatic rev-matches a manual shift. Or rather, if you shift manually, it takes forever for it to shift. If you shift manually and blip the throttle, it shifts right away. If you forget yourself and just treat it as a pedal-less non H gated manual, it actually serves very well.
Back in the 90's, VW had a golf sold in Europe that had an automatic clutch, but still had the H pattern shifter. It was a start/stop car that we had to do research- it was freaky to drive, as the car would declutch and shut down above 45mph when you tipped out. Really odd.
TGMF wrote: No, it wouldnt stall, the torque converter is locked, thus the engine is being driven by the trans, that is being driven by momentum of the car. The RPM's dont drop of because its a mechanical connection. That's why its down shifting as well, to keep the rpm high enough to prevent vibration, and to allow fuel cut for as long as possible. Once you run out of enough speed, the torque converter will unlock, injectors will begin to cycle, and as the engine decelerates near 1500 rpm or so, it resumes normal idle.
Has nothing to do with locking converters. The fluid in the converter is enough to backdrive the engine. Pre-lockup transmissions don't just drop to idle when you let off the throttle, after all.
It's an interesting bootstrap situation. You can coast in gear from speed just fine. But that is only because the converter is already spinning fast enough to provide torque transfer from the input shaft to the converter shell (bolted to crankshaft) which is also what is turning the front pump that is driving the clutches or bands together so the input shaft can turn in the first place. If the engine isn't turning to begin with, an automatic is just a box of neutrals since there's no hydraulic pressure (this offer not valid for Very Old automatics with a driveshaft-driven pump)
wbjones wrote:alfadriver wrote:I can "maybe" accept that for the more recent vehicles .. but for those of 10 - 15 - 20 yrs ago .. and the BS computers they had then … that's harder to swallowwbjones wrote: In reply to Streetwiseguy: but I am willing to be convinced … well sorta .. I've had some pretty darn good mechanics that say nope … nor do I have much faith in GM being this good with something like the Sonic … we ain't talking about one of their top of the line vehicles with the stop start system … *shrug* by that I mean, I have trouble believing they would put that much work into making it as seamless as it seems to be … I can't feel/hear it regardless whether I roll to the light still in 6th, or in neutral … and for that matter I can't feel/hear it in Mom's automatic Fit … again *shrug* even if the ECU would show zero duty cycle, can there still be a "trickle" of fuel passing ?Non-linear actions in cars piss people off- so yes, the off and on is calibrated that well. And no, if there zero duty cycle, there is not trickle fuel- if there is, it won't burn, and that will completely burn up the catalyst in very short order.
If I ever buy the 72 142E I want, I will come and take you for a ride, with a scope hooked up to the injectors.
alfadriver wrote: In reply to wbjones: Manuals have even other things they *can* do- some do shift fuel shut off. I wish more of them did- my Fiesta does not, and the speed that the engine slows down during shifts is way too slow.
That's another story. The idle hangup that is programmed into almost all manual trans cars is a pollution control deal. Rapid close of the throttle sends an little shot of unburnt hydrocarbons down the pipe, and the EP"A doesn't like that at all.
Its better than the units they added onto carbs to do the same thing, but its harder to unscrew and throw away.
alfadriver wrote: Non-linear actions in cars piss people off- so yes, the off and on is calibrated that well. And no, if there zero duty cycle, there is not trickle fuel- if there is, it won't burn, and that will completely burn up the catalyst in very short order.
In the injectors trickle fuel when not being given ground by the computer, we call those faulty injectors that belong in the trash bin 
The first hybrid I ever got to sample was a 1st-gen Escape. I could NOT tell the cut-in point between regen-only braking and "normal" braking. I was very impressed at the seamlessness.
alfadriver wrote:Knurled wrote:Honestly, if you can shift a 2010 Hyundai into reverse while going forward, and it actually tries to do that, Hyundai/Kia is doing it wrong. By 2010, the shifter is totally electronic in an auto car.cwh wrote: I really don't know, but the owners manual for my 2010 Hyundai very clearly says do not do it. Very dangerous. Huh?Well, if you coast in Neutral, you're that much closer to accidentally finding Reverse, which is not so much a good thing to do when at speed.
We're talking about Hyundai, here. Their error correction is less than robust. It's not uncommon for a failing TPS or TPS wiring (broken ground usually) on some of their models to cause the transmission to slam shift to first gear at any speed. (The transmission slamming into 1st gear at 40mph with the engine at near 0% throttle actual is an... interesting experience. Wear your seat belt)
See, MOST manufacturers who use 5v referenced sensors will have an upper sensor reading of about 4.5v, and throw out/ignore any data over 4.5v as faulty. But Hyundai is not most manufacturers...
Streetwiseguy wrote:alfadriver wrote: In reply to wbjones: Manuals have even other things they *can* do- some do shift fuel shut off. I wish more of them did- my Fiesta does not, and the speed that the engine slows down during shifts is way too slow.That's another story. The idle hangup that is programmed into almost all manual trans cars is a pollution control deal. Rapid close of the throttle sends an little shot of unburnt hydrocarbons down the pipe, and the EP"A doesn't like that at all.
Funny thing is, shift fuel shut off is not that hard to calibrate. BTDT.
Realistically, the first events of partial/slow burns isn't that hard to deal with- the catalyst deals with it well. It's the constant misfire that's the problem.
IMHO, what stops shift fuel shut off is just not wanting to do it.
(BTW, I'm quite familiar with the emissions rules. It's what I do- so you know)
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