Compression braking.

[skippy]

Shoud I or shouldn't I use Compression braking?

that is the question.

Basically I am fairly new to manual and was told I can use the gears to slow down, then told I should use the gears, and yesterday read a post telling me I shouldn't
http://www.astinagt.com/forum/viewto...c&start=30

So what is the score lads and ladettes?


Thanks in advance

[twilightprotege]

dont bother. save fuel.

anyway, your brakes will always stop you quicker than engine braking

[Astro Boy]

Originally Posted by skippy

Shoud I or shouldn't I use Compression braking?

Well..you know where i stand :P, unless your driving a 9 tonne truck.. don't do it... having said that, i tend to drive my car harder than most, so that's why i don't do it... gearboxes aren't designed to slow cars down... millions of ppl do it, and don't have problems, its up to you... but if you ever plan to partake in any sort of motorsport... its a REALLY BAD habit to get into :evil:

So what is the score lads and ladettes?

Make it a poll :P

[lamby1986]

i use the gearbox to slow down, but thats not using it instead of braking, thats as the car decides to slow down with momentum loss. ie as the revs go under 1500 down to the next gear, and just let it happily roll. in this situation any "extra" stresses on the gearbox are insignificant.

usually, i only do this when theres traffic lights up ahead that i know if i slowly roll to i wont have to stop cuz they will change to green. as apose to driving up there, breaking. waiting, then accelerating again. u use more fuel to accelerate then to coast along :wink:

however, what Bourne Boy said about gearboxes being made to take large forces in one direction is true. accelerating theres both the weight of the car force and the engine force to contend with. in slowing down (at idle in gear) there's only the cars weight and the gearbox will take that. what it wont take (too often) is cruising along in 5th then going 4th, 3rd, 2nd in rapid succesion instead of using the breaks.

as always, correct me if im wrong

[Astro Boy]

Well said :wink: i too do the traffic light thingy...

[skippy]

Yeah it was sold to me under the guise of saving brake pads, I asked wouldn't that be way overcompensated for by the fuel, told it wasn't.

Didn't really believe it then that weekend was watching a rally and one guys brakes totally failed so he completed the course using only compression braking that just seemed so cool I had to try and since then have been using compression braking as much as possible as I thought it was good to do.

I think I will just do it while decelerating to lights if I have plenty on time but if any sort of real stopping is needed just use brakes with clutch in and work it down the gears with out engaging any till I want some go.

A great big Thank You to yall,

OK now another one,

say I have a roughly 500M downhill is it a good idea to just put the clutch in and roll down thus saving fuel? no much but if I can do it on every steppish hill decent could be worth a bit over time. It just seems wasteful to hav my engine reving at say 2.5 while I am using the brake to slow me.

I used to do it until once I smelt a bit of burning clutch (memories of high school days) so I stopped doing it. might of been another car but dunno.

Should I do this at all?
If I do should I leave it in say 4th and just put the clutch in or should I put it into neutral?


Also

as the revs go under 1500 down to the next gear

I never let them get that low has nothing if I want to get moving again I do have the V6 which is supposed to rev quite high but I never go below 2000 unles in second on a round about and when coming out I wish I could chuck it down to 1st.

[platypus]

`coasting down hills - NOT GOOD

i shift down, so as to avoid brake fade i'm sure your all familia with this

and as to te compression braking, i do use it at lights, on the freeway (no lower than 4th) and i do use it in emergency braking, but thats just a second nature to me

jam on 2nd gear while jammiong on the brakes, sure its hard on the car, but so is the car in front of you!!!

[boostedbatman]

Originally Posted by ahb11m

`coasting down hills - NOT GOOD

i shift down, so as to avoid brake fade i'm sure your all familia with this

and as to te compression braking, i do use it at lights, on the freeway (no lower than 4th) and i do use it in emergency braking, but thats just a second nature to me

jam on 2nd gear while jammiong on the brakes, sure its hard on the car, but so is the car in front of you!!!

Thats my philosophy, use it where you need it
If you drop a gear or two when struggling to brake and save yourself some bingles then how can it be a bad thing :roll:
Try playing any playstatin or Xbox Driving game in manual and drive without using downshifts when braking and you will see the difference, Or the wall

[platypus]

or just get a nice long stretch -

automatic owners you can do this too!!!

[Laser the Amazer]

if I'm an down changing early under brakes I'll rev the engine while the clutch is in

by doing this I try to get as close to what the car is going to rev at when you let the clutch out, thefore everything is spinning roughly the same when disengaging the clutch therefore less stress for everything.

My neighbour demonstrated this to me by using changing gears smoothly with out using the clutch

sounds great with a loud exhaust as well

Rob

[Cosmo Dude]

I frequently use the O/D off to make minor speed corrections. It's not too different to lifting your right foot to decelerate those 2-3km/h on the freeway.
I always downshift when I brake in a manual that way you are in the correct gear should you need to accelerate. The degree I depend on the engine braking depends on road conditions and how much I want to affect the f/r brake bias. I tend to be more aggressive in a RWD than a FWD.

[platypus]

is most fun when some one is following right on yer ass - compression braking unfortunently doesn't turn on the brake lights, meaning you could have someone riding in the boot!!

[Rupewrecht]

Originally Posted by Cosmo Dude

I always downshift when I brake in a manual that way you are in the correct gear should you need to accelerate. The degree I depend on the engine braking depends on road conditions and how much I want to affect the f/r brake bias.

what he said

[skippy]

recalling an incident just after I first got my car, think it was one of my GFs first trips in it.

Driving along bit unsure about all this manual stuff anyway,
driving up to red light go down to second,
it goes green I Speed up and take the slight bend in the road and then put it into Third Nup First,

Fark me,

The horns and the skidding and the swearing

yes a very memorable experience. Maybe even more so for the person behind me.

[Asterix]

On a similar note, a mate reckons some engineers @ Holden reckoned you shouldn't coast a car down the road in neutral (not sure if they were referring to Auto or manual - auto I suspect) 'coz it's bad for the gearbox.

Anyone got a theory on this one?

[platypus]

hmm i wouldn't think that it would be bad for the box, but its bad for car control....

roo jumps out, you want to accelerate after turning the wheel, you floor it, ..... who remembered to select the appropriate gear??

clutch cable breaks (or hydraulics) - good luck picking up a gear and since your hydraulic clutch broke you can't change back into a gear, due to the road speed


you should save petrol on vacuum anyway - well in an EFI car anyway, as they usually cut the injectors on coasting (in gear) as the road turns the engine - when your coasting the engine is idling, and having to use petrol to keep going

(try driving a car that shows immediate fuel consumption down a hill)

[Nate]

yeah as james says ... you should always be in gear ... in an emergancy situation thats an extra second or two you have just lost because you needed to put the go stick in the right place

[Astro Boy]

It comes down to what we've been saying...

ANY road going gearbox is designed to take force in one direction only... from the input shaft, to the output shaft (funny how they're called that :wink: )... but when your coasting your car in neutral, your using the output gears to turn the input gears... they just wear prematuely and aren't designed to do it...

[Astro Boy]

hey nate, you remember the corolla days... where i even used to turn the engine off if i could save fuel coasting somewhere.... :P

.... back in the day...

[skippy]

Would that involve a high gear clutch start?