Engine Braking

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gupta_p

Senior Member
Well, I was randomily sitting around, when I noticed my civic manual was glistening on my dining table. I grabbed it, and launched into an .. information mining .. trance. THEN!!

I noticed it said that you could downshift, and use the engine+transmission to brake (or mebbe break ;) ) you're car...

Here's my question .. I've always known that you can let go of the clutch at a low gear, and not accelerate .. and u'll slow.. but is that a safe thing to do? Does it mess up the transmission, engine, etc?
 
yes, if you do not lower your speed before downshifting it will definately send a jolt through your driveline...and to answer your question it will hurt your transmission. besides theres no need really unless you're in a FR car and trying to drift.
 
as long as you try to adjust your rpm so that when the clutch is relased your tranny is spinning the speed that it would be when going 50 mph in fiths then you throw it in 2nd, that is not the way to do it. If you just slowy down shift from 4th-3rd-2nd, it will not do that much harm and it will also help save your brakes. Also if you ever go down step hills, Engine braking should be the only kind of braking. If your ever going down a hill (mountian) and you just ride your brakes, they can heat up to the point of brake fad and you will no longer be able to stop.
 
That's what I thought ... it seems like a good idea... but why would I need to save my brakes? lol. (besides the whole mountain thing .. that makes sense)

So, what DB level should my ears be picking up when I should shift? (lol, I don't have a tach ;))


Thanks.
 
the engine is for accelerating the car
brakes are for slowing the car
under some circumstances (ie: the mountain thing) it can be a useful tool but even then your not slowing the car you are maintaining the speed you are traveling at using the gearing
and for anyone who says "it saves your brakes".... compare the price of brakes to the price of a clutch.... (fuck that)
 
Yep, engine braking should only be used in 2 circumstances

1. going down a really really long hill

2. slowing down when you see a cop (brake lights are a dead give away)



Brake pads are cheap...engines/transmissions are not. You wont specifically hurt your engine by engine braking, but it does cause more wear and tear, just like taking it to the redline does.
 
actually redlining your car doesn't hurt your motor as much as starting it up ;) starting it is the worst thing you can do to your motor...go figure :unsure:
 
Originally posted by B16RacerN2NR@Mar 1 2003, 02:48 AM
actually redlining your car doesn't hurt your motor as much as starting it up ;) starting it is the worst thing you can do to your motor...go figure :unsure:
Click to expand...

Alright, you just keep on redlining your car, and I will keep on starting mine, and lets see who's lasts longer.
 
I believe in most cases they mean to use it as... lets say your coming up to a light thats green you are a good few hundred feet away and you know its a long ass light then you see yellow.... I myself don't hit the brakes I let my car slow down on its own to about 1800-2000RPM them I push the cluch in blip the throttle then let it out in the gear lower then the last and repeat only time I use my brakes is at that last few feet

something I want to point out is has any one everheard a big 18wheeler/dump truck do a fast stop? you can hear the engine RPM getting lower then you hear Vroom! BUUPUPUBUPBUBPBUP "rpms raise back up" then they do it again... yup you got it they keep the motors in gear since it helps to slow down with the extra drag on the engine

Starting up a car is worse then redlining it unless you're holding it there for a few mins.... keep in mind all your oil is in the pan very little is left on the rings so when you first turn that car over it pulls/pushes the pistons in a dry cly I believe its a well known fact that start ups are the leading cause of engine wear
read a Slick 50 bottle or info about full synth oil "it coats and sticks to the parts better" there for when you have cold start ups its has more oil on it then an normal oil would have left

all I can say is come to my place and hear my car start up it will make you want to turn it off to save the engines life it just knocks smacks idles like shit and sounds like its gonna blow up gotta love JE pistons =) can opener is a good word to use for how it sounds
 
Originally posted by jeffie7@Mar 1 2003, 05:29 PM
something I want to point out is has any one everheard a big 18wheeler/dump truck do a fast stop? you can hear the engine RPM getting lower then you hear Vroom! BUUPUPUBUPBUBPBUP "rpms raise back up" then they do it again... yup you got it they keep the motors in gear since it helps to slow down with the extra drag on the engine
Click to expand...

trucks like that are equiped with a "jake brake" and designed to use the engine to assist the brake system
http://auto.howstuffworks.com/question134.htm
 
i used to do that alot (engine braking). it doesnt hurt the clutch or tranny if you do it WHILE you are braking and if your feather the clutch as you do it (dont just dump the clutch). my clutches have lasted over 120,000 miles so i know it didnt hurt it. my synchros are fine too.
 
Engine braking doesn't hurt your engine, or your clutch.

It will damage, over time, your input shaft and countershaft bearings inside the transmission.

When you press the clutch pedal down, the engine and the transmission are no longer rotating at the same speed. Depending on the weight of your flywheel, your engine speed can dramatically decrease comapred to the shafts inside the transmission, considering they are rotating at whatever given ratio the gear is multiplied by vehicle speed. Going from 5th to 4th in a B16 is an aproximately 3k RPM difference in engine speed, but at the gear ratio in the trans, it's multiplied by many more. Without matching revs by blipping the throttle, the transmission can take a HELL of a jolt from going down in gears. The previous owner of my current del Sol downshifted, as my transmission has whining input shaft and counter-shaft bearings no matter what gear I'm in. The sound is worse at lower RPMs, and turns into a whine as they climb. The synchronizers in my transmission are fine. Every once in a while when the R's are high my 1-2-3 shifts will crunch, but mostly because of the worn bearings, and the slop in the shafts because of it.

I would suggest NOT downshifting, but If you're going to do it anyways, please blip the thottle when you press the clutch in the bring the RPMs up to where that lower gear would normally put you for the speed you are travelling. It will save you a $700 transmission rebuild in the end.
 
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