Can an automatic vehicle have a manual transmission + clutch system installed?

[Zenmervolt]

Originally posted by: Comdrpopnfresh
I didn't realize cars shut off gas flow to the engine if the momentum of the drive train was enough to keep the engine going. Sure my car has this? Seems kinda advanced. And if it did, would there be some sort of lag if I pressed the throttle, due to restart of fuel flow, and having to get it in the combustion chamber?

It's not advanced, it has been in use by EFI systems since at least 1982 and possibly earlier. (BOSCH Motronic ML 1.2 and above for certain.)

I am absolutely certain that your Camry has this feature. There is no noticeable lag because the fuel pump is always on, the ECU simply does not fire the injectors. The injectors come back on instantaneously when the throttle position sensor comes off of its idle setting or when the RPM drops below a preset value.

Additionally, by not using engine-braking on long downhill sections you risk overheating your brakes and losing your ability to stop, not to mention losing the ability to quickly accelerate if the need arises. Be aware that coasting in neutral is illegal in almost ever state.

ZV

 

[LennyZ]

Once you convert to manual trans you can save even more $$$ buying bulk beef!

 

[nakedfrog]

Man, nobody told me it was time for the semi-annual "I'm saving gas by coasting in neutral" thread!

 

[BassBomb]

pretty sure is not a smart idea to be shifting into N randomly while moving and switching back

 

[Comdrpopnfresh]

Originally posted by: Zenmervolt

Originally posted by: Comdrpopnfresh
I didn't realize cars shut off gas flow to the engine if the momentum of the drive train was enough to keep the engine going. Sure my car has this? Seems kinda advanced. And if it did, would there be some sort of lag if I pressed the throttle, due to restart of fuel flow, and having to get it in the combustion chamber?

It's not advanced, it has been in use by EFI systems since at least 1982 and possibly earlier. (BOSCH Motronic ML 1.2 and above for certain.)

I am absolutely certain that your Camry has this feature. There is no noticeable lag because the fuel pump is always on, the ECU simply does not fire the injectors. The injectors come back on instantaneously when the throttle position sensor comes off of its idle setting or when the RPM drops below a preset value.

Additionally, by not using engine-braking on long downhill sections you risk overheating your brakes and losing your ability to stop, not to mention losing the ability to quickly accelerate if the need arises. Be aware that coasting in neutral is illegal in almost ever state.

ZV

Oh crap- I didn't know coasting in neutral was illegal- thanks for the fact! I know coasting with the car turned off is... That's why SWIM only does it on back-rural roads that are straight and no braking is needed so that an emergency brake maneuver can be made w/ the left-over compression on the hydraulic lines before there is no residual assisted braking left.

 

[jhu]

Originally posted by: Comdrpopnfresh
Oh crap- I didn't know coasting in neutral was illegal- thanks for the fact! I know coasting with the car turned off is... That's why SWIM only does it on back-rural roads that are straight and no braking is needed so that an emergency brake maneuver can be made w/ the left-over compression on the hydraulic lines before there is no residual assisted braking left.

going faster than the speed limit is also illegal, but no one really complains about that one. in most jurisdictions, it's illegal to go down a hill or mountain in neutral. but a lot of those laws don't say anything about going up hill or flat ground in neutral.

 

[jagec]

Originally posted by: jhu

Originally posted by: jagec

Now obviously there's a turnover point where you will be dissipating so much more energy through frictional losses at a high RPM (leaving it in gear and coasting) that it will outstrip the fuel you would otherwise burn at a low RPM (idling in neutral), but if you keep it in top gear the difference in frictional losses is minor at most reasonable speeds.

for very steep hills that's true. for gradual declines and flat roads, it's not.

The engine doesn't know or care how steep of a hill it's on. If you are at higher RPMs, you are losing more energy to friction than if you are at lower RPMs.

Let's pick a hill where if you put the car in top gear and coast down it, the engine speed will be around idle. Now go down the same hill, only this time take the car out of gear and let the engine idle on its own. Although you will be going slightly faster at the bottom of the hill when you put it in neutral, you will have burned MORE gasoline, since it takes exactly as much energy to keep the engine spinning in both cases, but in the second you are losing more energy to rolling resistance since you are traveling at a higher speed.

Steep hills (which usually mean a lower gear and a higher RPM) actually lower efficiency for coasting in gear, since there will be more frictional losses. However, since we don't want to end up going 120MPH at the bottom, we need to bleed off energy anyway. A neutral coaster would be applying the brakes a lot.

 

[Comdrpopnfresh]

Point taken. However, my car car can onyl reach ~83 mph in neutral and 70 mph in gear, so I apply the same amount of brakes in either case. I will from now on go down long hills in drive and maybe put it in neutral if there is a flat stretch to delay having to apply acceleration.

 

[Comdrpopnfresh]

so what about when stopped at a red light? would neutral be beneficial then, since there is no return force from movement to keep the engine moving? I'll still turn off the engine for stops >15s, but what about those short ones- is neutral after coming to a complete stop a beneficial action?

 

[jhu]

Originally posted by: Comdrpopnfresh
so what about when stopped at a red light? would neutral be beneficial then, since there is no return force from movement to keep the engine moving? I'll still turn off the engine for stops >15s, but what about those short ones- is neutral after coming to a complete stop a beneficial action?

barely. it's at most .1 gph more, and with stops < 15s that's still within the margin of error of detection. for stops >15s, turning the engine off helps quite a bit to decrease fuel consumption.