Manual or Automatic transmission..which do you prefer?

[DJ's left nut]

Originally Posted by CoMoChief

manual ....saves on gas and doesn't wear on your brakes as much (if you downshift).

it's more fun to drive too. sucks though if you're trying to eat and drive around town like on the way to work or something.

This is wrong.

Manual transmissions don't actually do much (if anything) to save on gas anymore. In fact, very few people are good enough with their shift points to keep them from getting worse MPG. Either they shift too late and run the RPMs up or they shift too early and dog the motor. Either way, they're not as precise as the manual that's been computer engineered to shift at the exact right time depending on your acceleration and power needs.

Manual transmissions tend to be on shitty econoboxes that get good gas mileage, but an automatic tranmission with overdrive will easily get just as good MPG unless the motor is so underpowered that it has to downshift to stay at speed.

With engine technology allowing people to get decent power even from fuel sippers, and with computer adjustable shift points on modern automatics, there is next to no distinction between automatic and manual transmissions in terms of MPG.

That argument for manuals is dead and has been for a decade+.

As to the brakes arguments - brake pads cost $60 and over the life of your car, if you were to downshift at every single point coming up to every single stop light you might save yourself the cost of one set of brake pads. However, by using engine compression to slow your car as you downshift, you're adding wear to the seals, etc... in your motor and thus making your motor less efficient over time.

Is a manual more fun? Yeah, when you want it to be. The easy compromise situation is an auto-stick transmission paired to a flappy paddle gear shift on your steering wheel. When I want to do nothing but go home, it stays in auto. When I want to run the shit out of it, I knock the knob to the left and shift on the steering wheel.

Done and done.

[Radar Chief]

Originally Posted by DJ's left nut

This is wrong.

Manual transmissions don't actually do much (if anything) to save on gas anymore. In fact, very few people are good enough with their shift points to keep them from getting worse MPG. Either they shift too late and run the RPMs up or they shift too early and dog the motor. Either way, they're not as precise as the manual that's been computer engineered to shift at the exact right time depending on your acceleration and power needs.

Manual transmissions tend to be on shitty econoboxes that get good gas mileage, but an automatic tranmission with overdrive will easily get just as good MPG unless the motor is so underpowered that it has to downshift to stay at speed.

With engine technology allowing people to get decent power even from fuel sippers, and with computer adjustable shift points on modern automatics, there is next to no distinction between automatic and manual transmissions in terms of MPG.

That argument for manuals is dead and has been for a decade+.

Sorry but this is just incorrect.
Parasitic Horse Power Loss, everything run by the engine is taking horsepower to make it work.
Plainly put, it takes more horsepower to run an automatic transmission than a manual one.
Take two cars with equal weight, engine, gearing and aerodynamics, the only difference being that one has an automatic and the other has a manual and the manual transmission with get better gas mileage because it’s not spending horsepower to spin fluid pumps or to power shift servos.
This is why “shitty little econo boxes” are still running manuals.

Originally Posted by DJ's left nut

As to the brakes arguments - brake pads cost $60 and over the life of your car, if you were to downshift at every single point coming up to every single stop light you might save yourself the cost of one set of brake pads. However, by using engine compression to slow your car as you downshift, you're adding wear to the seals, etc... in your motor and thus making your motor less efficient over time.

Is a manual more fun? Yeah, when you want it to be. The easy compromise situation is an auto-stick transmission paired to a flappy paddle gear shift on your steering wheel. When I want to do nothing but go home, it stays in auto. When I want to run the shit out of it, I knock the knob to the left and shift on the steering wheel.

Done and done.

The brake wear argument is that when you push in the clutch you’re mechanically disconnecting the engine from the rest of the drive line so the engine isn’t still trying to push the vehicle forward while brakes are applied.
I’m sure the extra engine RPM’s could accelerate engine wear but mostly using engine compression for braking just wasteful of gas as you’re spending money in the form of gas to decelerate when the brakes are perfectly capable of doing the same job.

[MIAdragon]

Originally Posted by Radar Chief

Sorry but this is just incorrect.
Parasitic Horse Power Loss, everything run by the engine is taking horsepower to make it work.
Plainly put, it takes more horsepower to run an automatic transmission than a manual one.
Take two cars with equal weight, engine, gearing and aerodynamics, the only difference being that one has an automatic and the other has a manual and the manual transmission with get better gas mileage because it’s not spending horsepower to spin fluid pumps or to power shift servos.
This is why “shitty little econo boxes” are still running manuals.

I think DJ is right here. The difference in parasitic loss is what 18% for an auto and 15% for manual, that measly 3% is easily made up by a computer controlled trans. This argument was true 25 years ago when the auto's were power glides and TH400's. Today's autos are VERY efficient, If manuals truly were more efficient you would see them in cars like the Prius that ONLY come in an auto.

[Radar Chief]

Originally Posted by MIAdragon

I think DJ is right here. The difference in parasitic loss is what 18% for an auto and 15% for manual, that measly 3% is easily made up by a computer controlled trans. This argument was true 25 years ago when the auto's were power glides and TH400's. Today's autos are VERY efficient, If manuals truly were more efficient you would see them in cars like the Prius that ONLY come in an auto.

I don’t necessarily disagree with that. If an engine is making enough power the difference in parasitic loss is negligible, and modern transmissions have become much more efficient than they used to be.
With the Prius you’ve got a lot of things going on other than just delivering power to the wheels. Like when you first hit the brakes in a Prius you’re not actually putting brake pad to disk, it’s actually connecting the electric motor in reverse as it spins it is charging the batteries. This is how they get their fantastic mileage in stop and go traffic. That’s also something I don’t think would be easy to accomplish with a manual transmission.

[HemiEd]

Originally Posted by MIAdragon

I think DJ is right here. The difference in parasitic loss is what 18% for an auto and 15% for manual, that measly 3% is easily made up by a computer controlled trans. This argument was true 25 years ago when the auto's were power glides and TH400's. Today's autos are VERY efficient, If manuals truly were more efficient you would see them in cars like the Prius that ONLY come in an auto.

That is interesting, things must have changed, I hadn't thought of that.

I know back in my drag racing days, one of the advantages of putting a 'glide in my Mopar (other than the tranny brake ) was that it only took about 48 hp to run it, and the 727 took about a 100.

I am sure torque converter technology has helped a lot with the gas mileage and the efficiency situation as well. The early "lock up" converters were a real problem source, but I haven't heard anything about them in years now.

[Radar Chief]

Originally Posted by HemiEd

That is interesting, things must have changed, I hadn't thought of that.

I know back in my drag racing days, one of the advantages of putting a 'glide in my Mopar (other than the tranny brake ) was that it only took about 48 hp to run it, and the 727 took about a 100.

I am sure torque converter technology has helped a lot with the gas mileage and the efficiency situation as well. The early "lock up" converters were a real problem source, but I haven't heard anything about them in years now.

I think a big part of the efficiency with modern auto transmissions comes from having electric servos do the shifting instead of fluid pressure. At least that’s the main difference between something like a TH700R4 and a 4L60E. They’re both GM 4 speeds but one is electronic controlled and the other still requires fluid pressure to sense when to shift and provide the power to shift.

[HemiEd]

Originally Posted by Radar Chief

I think a big part of the efficiency with modern auto transmissions comes from having electric servos do the shifting instead of fluid pressure. At least that’s the main difference between something like a TH700R4 and a 4L60E. They’re both GM 4 speeds but one is electronic controlled and the other still requires fluid pressure to sense when to shift and provide the power to shift.

That makes sense, thanks.

I have a "Diablo Sport" programmer that will actually change the shift points and firmness on the Challenger, and that would have to be electronic like you say.

When you go into "Auto Stick" mode the MDS system is turned off.

[COchief]

Originally Posted by HemiEd

That makes sense, thanks.

I have a "Diablo Sport" programmer that will actually change the shift points and firmness on the Challenger, and that would have to be electronic like you say.

When you go into "Auto Stick" mode the MDS system is turned off.

Doesn't mopar drive you nuts with the constant slushboxes? I like so many of the SRT8 models (particularly the 300) and it makes me insane that every single god damn one is an auto (challenger excepted I guess). One thing I like about GM is they only made the CTS-V in manual, I wish Chrysler/Dodge would get on board. I would hope anyone buying a SRT vehicle would only want stick. My old man had a SRT Grand Cherokee, while it was definitely fast as shit, it got old so fast just smashing the gas pedal and feeling the front end "hover".

[DJ's left nut]

Originally Posted by MIAdragon

I think DJ is right here. The difference in parasitic loss is what 18% for an auto and 15% for manual, that measly 3% is easily made up by a computer controlled trans. This argument was true 25 years ago when the auto's were power glides and TH400's. Today's autos are VERY efficient, If manuals truly were more efficient you would see them in cars like the Prius that ONLY come in an auto.

Right.

At best, it's a completely negligible difference that's almost entirely offset by the fact that people aren't machines and if they aren't timing their shifts perfectly, they give back whatever mechanical gains they may make up.

In the real world, automatic transmissions have become so advanced that they have overcome the mechanical simplicity of the manuals.

[stevieray]

Originally Posted by DJ's left nut

In the real world, automatic transmissions have become so advanced

including cost and repairs

[COchief]

Originally Posted by DJ's left nut

This is wrong.

Manual transmissions don't actually do much (if anything) to save on gas anymore.

You got one point correct, including "this is wrong" in your bullshit post.

People never consider the EPA's mandatory driving style when getting MPG figures. Does the EPA hit neutral on a huge hill? When they see a red light a block ahead do they drop it into neutral? When driving a car with a lot of torque do they alter their shift points? Do they alter which gear they're in at certain speeds? The answer is no, they have to follow a strict set of guidelines. I drove a 2001 Maxima 5-speed that had a city MPG rating of 19, I was always near 30 just by dropping neutral when appropriate (live in CO, tons of huge hills, places I coast for miles) and by going to 5th at around 35mph since the engine had 217 of torque in a fairly small package. This is all I did, I actually am a pretty spirited driver, not a hyper-miling douche that takes an hour to get up to 50mph.

I currently have an auto Xterra, while I don't think I'd want it in a stick, there are so many situations where I would just pop it in neutral where the RPMs are 3k or more.

Also to the dumbasses that engine brake: You are burning a shitload of gas by keeping your RPMs up that high instead of idle and last time I checked brakes were about a hundred bucks. Why the hell would you wear out your engine/tranny over a part that costs a hundred bucks and if we are talking years of ownership, hundreds in gas. Simply stupid.

[DJ's left nut]

Originally Posted by COchief

You got one point correct, including "this is wrong" in your bullshit post.

People never consider the EPA's mandatory driving style when getting MPG figures. Does the EPA hit neutral on a huge hill? When they see a red light a block ahead do they drop it into neutral? When driving a car with a lot of torque do they alter their shift points? Do they alter which gear they're in at certain speeds? The answer is no, they have to follow a strict set of guidelines. I drove a 2001 Maxima 5-speed that had a city MPG rating of 19, I was always near 30 just by dropping neutral when appropriate (live in CO, tons of huge hills, places I coast for miles) and by going to 5th at around 35mph since the engine had 217 of torque in a fairly small package. This is all I did, I actually am a pretty spirited driver, not a hyper-miling douche that takes an hour to get up to 50mph.

I currently have an auto Xterra, while I don't think I'd want it in a stick, there are so many situations where I would just pop it in neutral where the RPMs are 3k or more.

Also to the dumbasses that engine brake: You are burning a shitload of gas by keeping your RPMs up that high instead of idle and last time I checked brakes were about a hundred bucks. Why the hell would you wear out your engine/tranny over a part that costs a hundred bucks and if we are talking years of ownership, hundreds in gas. Simply stupid.

Then your transmission is ****ed up.

My goddamn camaro doesn't idle above 800 and its 45 yrs old. If you're just rolling down a hill an automatic, the engine is going to be either idling or if you're on cruise it may downshift to keep you from accelerating past your target speed. It's not going to sit at 3k if you're not on the gas at all; it's going to coast down to idle speeds.

Oh, and you're wrong on the engine breaking thing - you don't use more gas when the RPMs come up during engine breaking. The RPMs are only rising due to the compression in the motor and the motor spinning down. It's not actually using any more fuel; it's the transmission turning the motor in the absence of fuel, rather than the motor turning the transmission. The RPMs come up because there's no place for the energy that the transmission is imparting on the motor to go (i.e. the engine compression) so the RPMs spin up and the compression finally peters the acceleration out. If you were actually feeding the motor fuel to create those RPMs, it wouldn't decelerate.

And while Radar and Hemi can speak to this more than I can, the last automatic I was fortunate enough to look at the guts of had some kind of slipping interlock in it where at lower RPMs it was barely engaged, so it's not like your breaks are having to work very hard to keep the car in place. At higher RPM the 'disks' in the transmission synch together and pull harder, so it's actually able to apply the power better. However, at low RPMs, the transmission isn't doing much work at all and as a consequence your brakes aren't doing much work.

And if you're spending a couple hundred dollars on brake pads - you're an idiot. If you had to replace the brake assembly altogether, it's because you were an idiot for a prolonged period of time, burned through your pads and ****ed up your rotors. That's when you start spending a couple hundred dollars. Brake Pads for your daily commuter are dirt cheap.

I reiterate, at it's very best, sitting in neutral at a stop light is going to do nothing more than save you a set of brake pads over the life of your car. Brake pads are cheap and easy to replace on your own. But hey, maybe you're right on those XTerras that idle at 3K.

To start out by calling my post bullshit and then excoriate people for burning fuel while engine breaking and then chirping about $200 brake pads is...interesting.

[alnorth]

Originally Posted by DJ's left nut

Oh, and you're wrong on the engine breaking thing - you don't use more gas when the RPMs come up during engine breaking. The RPMs are only rising due to the compression in the motor and the motor spinning down. It's not actually using any more fuel; it's the transmission turning the motor in the absence of fuel, rather than the motor turning the transmission. The RPMs come up because there's no place for the energy that the transmission is imparting on the motor to go (i.e. the engine compression) so the RPMs spin up and the compression finally peters the acceleration out. If you were actually feeding the motor fuel to create those RPMs, it wouldn't decelerate.

Yeah, this whole "coasting down hills in neutral saves gas" thing is apparently a myth. I used to believe it but I've read too many articles by car guys who knew what they were doing saying that the RPM difference in that situation was deceptive. Most of the insane hypermiler techniques that work don't depend on a manual. There might be a small benefit with idling in neutral at a stop.

I still prefer manuals, they are cheaper and more fun to drive, but most of the gas savings come from efficient shifting, not throwing it in neutral.

[Frosty]

Originally Posted by alnorth

I still prefer manuals, they are cheaper and more fun to drive, but most of the gas savings come from efficient shifting, not throwing it in neutral.

I have a Scan Gauge II, which is a diagnostic device that plugs into the OBDII port of the car and can give you real time feedback as you drive. One of the things you can get is instantaneous gas mileage.

I have found with several different cars that going from driving in gear to coasting in neutral at speed can make the mileage more than double (it would go up to around 60 - 70 mpg in the car I was testing). If you coast in gear, the mileage readout would say "9999", which basically meant I wasn't using any gas at all.

[alnorth]

Originally Posted by Frosty

I have a Scan Gauge II, which is a diagnostic device that plugs into the OBDII port of the car and can give you real time feedback as you drive. One of the things you can get is instantaneous gas mileage.

I have found with several different cars that going from driving in gear to coasting in neutral at speed can make the mileage more than double (it would go up to around 60 - 70 mpg in the car I was testing). If you coast in gear, the mileage readout would say "9999", which basically meant I wasn't using any gas at all.

It may be lying to you when coasting downhill in neutral.

http://www.popularmechanics.com/cars...l-fuel-economy