Subaru WRX Forum banner
1 - 20 of 30 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter · #1 ·
OK, my dad and i are at different ends on this one. I think engine braking is bad, and he swears by it. What he does is, when hes going like 50 mph in 5th gear, and is going towards a stop sign, he just gets off the gas, and puts it into neutral, then uses the brakes to slow him down completly.

Me on the other hand, i downshift to every gear, while TRYING to rev match. When i get to second gear, i just brake, cause i know downshifting to first is a big no no for me, at least for now.


So, please tell me, is it bad to engine brake when going to a complete stop? Or is it OK?




Sorry, i did a search, but i didnt feel like reading through all the posts on all 75 pages...
 

·
Registered
Joined
·
82 Posts
I'm so confused. You say you don't like engine braking, and your dad does. But then you say he puts it in neutral and uses the brakes to slow down while you use the engine to slow down?

Let's say you're going down a moderately steep hill and you're in 3rd gear, foot off the gas, off the break. Since you're going downhill, the acceleration brings your rpms up to a point where you might normally shift to 4th.

If you shift to 4th, you'll have to use the brake pedal to keep your speed down.

If you stay in 3rd and let the engine keep your speed down instead of the brakes, you're engine braking.

As far as I know, it's not bad for the car, and it's one of the advantages a manual has over an automatic.
 

·
Registered
Joined
·
21 Posts
Discussion Starter · #4 ·
Pug said:
I'm so confused. You say you don't like engine braking, and your dad does. But then you say he puts it in neutral and uses the brakes to slow down while you use the engine to slow down?

Let's say you're going down a moderately steep hill and you're in 3rd gear, foot off the gas, off the break. Since you're going downhill, the acceleration brings your rpms up to a point where you might normally shift to 4th.

If you shift to 4th, you'll have to use the brake pedal to keep your speed down.

If you stay in 3rd and let the engine keep your speed down instead of the brakes, you're engine braking.

As far as I know, it's not bad for the car, and it's one of the advantages a manual has over an automatic.



thanks for setting me straight. So what do you call what my dad does?
 

·
Premium Member
Joined
·
785 Posts
It's called being a fool and riding the brakes...... actually, I didn't mean that(just jokes you know). On a serious note, what your dad does will ride the brakes, is not as efficient slowing down and in some cases dangerous. For example, he's slowing for a red light and is about to turn at this intersection, but the light turns green before he gets to the original stop point.....he's riding in neutral, the engine is at idle and he's probably confused about what gear to slam it into. At some point, I'm sure he'd have rode part way through the turn in neutral and scrambled to shove the box into gear and probably(by not rev matching) bogged.
According to what you described, you are making effect of engine braking.
 

·
Registered
Joined
·
3,501 Posts
Engine braking is one the BEST things aboutt driving a manual transmission car. The only expense of engine braking is when you drive aggressively (like I do pretty much all the time) and can't rev match properly is your clutch.

As for visiting all the gears, that's not really necessary. OK, you pick 50mph. Maximum speed for second gear is ~60mph. If I'm hauling A$S and a 30mph corner is coming up I do this:

Clutch in, brake slightly while downshifting to second gear, heel and toe to bring up the revs while braking, release the clutch slowly, but not TOO slowly.

This is rev matching/engine braking/heel and toeing, it's not easy, but when I finish this 3 second process, I'm entering my 30mph with the tranny in gear, the engine in its powerband, my foot on the gas, and oh yeah all four wheels spinning :D [optional]

Your dad's method will preserve the tranny at the expense of your brakes and your corner speeds. When I first starting driving a stick I would hold the clutch in, downshift, brake, then declutch. This is known as "riding the clutch" but this term applies mainly to letting the clutch out much to slowly when launching or shifting. In the winter, when traction is king, your dad's method become downrigth DANGEROUS, because the tranny needs to be engaged as much as possible to maintain traction.

I don't think I can be any more clear about this point:
ENGINE BRAKING IS GOOD AND IMPORTANT FOR GOOD DRIVING.

Its sounds to me like you and your dad should do a NASA "High Performance Driving Experience" track day so he can see that he is very wrong.

-Jim
 

·
Moderator
Joined
·
895 Posts
aside from the safety aspects of engine braking ( w/ a manual trans car) how does it affect gas milage? i would think that it would go down b/c when you downshift the revs go up since you're in a lower gear. even though you arent on the gas, gas is still going into the cylinders, right?
 

·
Premium Member
Joined
·
3,539 Posts
I do tons of mountain driving and engine breaking is essential for hustling the car downhill. If you used your Pop's method - you wouldn't make it down in one piece - run out of brakes halfway and then be looking to hit the mountain on purpose to save your life. Jim's comment about winter driving goes double down a long twisty hill. Try to just use just your brakes to maintain control downhill and you'll hit the mountain again, but this time not on purpose!

C
 

·
Registered
Joined
·
17 Posts
Penguinking said:
aside from the safety aspects of engine braking ( w/ a manual trans car) how does it affect gas milage? i would think that it would go down b/c when you downshift the revs go up since you're in a lower gear. even though you arent on the gas, gas is still going into the cylinders, right?
As I understand it your gas mileage is much more a function of the mix your ECU is injecting (i.e. rich=bad gas mileage, lean=good mileage) than your straight-up RPM. And during engine braking your ECU is using full lean mix, which is almost completely air, no gas.

For a really extreme illustration, try turning your car off at 60mph and then engine-braking to a stop. Notice that the engine is still turning over, and engine braking still works even though the accellerator pedal doesn't do anything? The braking effect is coming from compressed air alone; no gas is involved.

I'd defer to someone who knows more about cars. Or if you have a friend with a BMW or Chrysler you can switch the trip computer over to instantaneous gas mileage to see what different things do to it.

EDIT: changed "key out of the ignition" to "turning your car off" to prevent people from locking their steering wheels and dying a firey death.
 

·
Moderator
Joined
·
895 Posts
ah ok

thats what i sorta thought - that when you're not on the gas then no fuel is being injected...but does that happen? that theres just air going in, and no ignition happening at all? my question was whether fuel is still being injected into the cylinders while youre engine braking - cause if it does, then *shouldn't* it lower your gas milage b/c the higher revs = using more fuel compared to idle (even if its still very little fuel)
 

·
Premium Member
Joined
·
3,539 Posts
That's just it - there isn't air going in - or at least very little. The throttle itself is a butterfly valve that closes almost completely - just letting in enough air for idle. That's a big part of engine braking - the motor is fighting against the vacuum to turn over. If you turned the ignition off and opened up the throttle, you'd get less braking effect. So sure, when you blip the motor on the downchanges you use a slight bit of gas, but when you're completly off the throttle you use VERY little.
 

·
Moderator
Joined
·
895 Posts
oh i see....


now it all makes sense :D


problem is now i don't have an excuse for why i'm getting such poor gas milage...i guess i'll hafta go easier on the car:(
 

·
Premium Member
Joined
·
3,539 Posts
Perhaps it has something to do with that lead foot of yours? I know that's my problem!
 

·
Registered
Joined
·
64 Posts
Have your Dad read the manual on your car. It says you should use engine braking as much as you can. (i.e. downshift to slow)

cheers.
 

·
Registered
Joined
·
2,039 Posts
engine braking is an essential part of good driving but what about the tranmission, im sure it wont help the life of it
 

·
Registered
Joined
·
64 Posts
PolarisSnT said:
engine braking is an essential part of good driving but what about the tranmission, im sure it wont help the life of it
If you drive reasonably, it won't hurt the tranny, but instead the clutch. It has been said by many here, and by many professionals: the clutch is a wear item, so the tranny and the drive-train isn't.
 
1 - 20 of 30 Posts
Top