Maximus

I have been driving manual transmissions for a long time and I frequently use what I call 'engine break' i.e. shifting down to slow down the speed...like I am going in 4th gear and I shift down to 3rd and then to 2nd to slow down in conjuction with using the regular breaks. Its not like I am punishing the engine all the time ... just gradual down shifts ... making sure the RPM doesn't go high while down shifting. I hope you guys understand what I am trying to say here. It has become kind of a driving habit for me. My question right now: Is this driving style harmful for an engine?

And MORE SPECIFICALLY how does this driving style affect a ROTORY engine viz. the apex seals etc..

Please enlighten me! as I haven't owned a rotory before.

tribal azn2

what ur doing is called transmission braking, not engine braking. ur using the gears to slow u down.

ur putting more wear and tear on the more expensive part(the transmission) then on ur brakes. brake pads/brakes are much cheaper and easier to replace then ur transmission.

Maximus

Hi tribal,

I understand that its not creating any problems for the brakes, actually the transmission braking would create lesser wear and tear on the brakes.

What parts of transmission get damaged?

Is it harmful for the cylinder/pistor or in rotory case the housing/apex seals etc???

Rexor

Maximus

I don't think there's anything unique in your style of driving a stick - this is what 99% of stick drivers do, and I can't believe it creates any excessive engine wear. It will certainly lengthen the life of your brakes, and leave you in the correct gear to take off swiftly once you stop deccelerating.

Go with your instincts, and have fun

tribal azn2

it doesnt hurt ur engine. the transmission doesnt get "damaged", ur just putting more wear on it. u rather wear out the less expensive parts(brake pads) then ur transmission

Maximus

Rexor,

Thanks for your input. When u are down shifting and using it to slow down the car what would be happening inside the rotory with respect to the intake/exhaust ports?

m477

This same question came up on Car Talk a while ago. They recommended using the brakes.

Maximus

Hi m477,

Any details that you remember?

nk_Rx8

This is one of those topics that have been debated forever, and on every forum I have ever visited. And there is never any agreement between the two camps. Some people say they never do it because of wear and some people (myself included) have always done it. I have never had any issues due to doing this and as long as you are rev matching, clutch wear is minimal. I would prefer to always be in the proper gear (even if there is 'alleged' extra wear) than to be in the wrong gear if I need to get moving quick.

moogle

I never had any problem downshifting to slow me down. I use it everytime and no problem. Gradually downshifting wont hurt, but going 4th to 2nd gear.

Superfan

I rarely do it. When I do, I rev match. I'd rather replace brake pads than synchro's.

Doctorr

Brake pads $50
Engine $5000
.
A gearbox never slowed anybody down. Engines sucking vacuum slow you down.
Throttles shut, engine turning 7000rpm, no fuel, no air, big vacuum to suck whatever lubrication you have into the combustion zone, to be burned 'blue' when you get back on the gas........
No, it's probably not the best situation to put your engine in. (This is when 'two-stokes' sieze, after a hard acceleration, you cut off the flow of cool air and freshly evaporated fuel, at the same time doubling the revs.) Remember, the wankel is actually a 'two-stroke/four-stroke' it has no idle time like a four stoke.
Even if you wear out your rotors as well as your pads, it is 5% of the engine rebuild cost.
.
Drive any way you like, but be aware of the wear & tear.

Ray.

DTECH-RX

I think where the confusion comes in to play with this topic is some people are referring to "slowing down" and manuevering through traffic vs. coming to a stop. As for downshifting to slow down in the process of driving and manuevering, Rexor is correct in that 99% of us probably do it, while when coming to a stop, some people may take the previous action to an extreme (IMO) and do it every time they are coming to a stop. As mentioned before, brakes are much cheaper than mechanical wear and tear regardless if it's the engine or the tranny.

As for me, I do downshift on occasion say if I'm in traffic and I know going down just one gear will slow me down enough while still being at a decent RPM, but at the same time, I almost never down shift while coming to a stop. I just put it in neutral and coast to a stop. If the situation changes while slowing down, the correct gear is only a snick away.

jimbobjoe

One of the negative aspects of using engine braking is that in a standard 2 wheel drive you will be applying this braking force to only 2 wheels, not all four. This can upset the balance of a car. On a front wheel drive car this could cause the car to oversteer and spin iif you are cornering.

I've done that once and it wasn't much fun. Missed everyone else though, so just completed the 360 and continued on my way.

Like everyone else I still use engine breaking, but not quite so aggressively as I used to

BillK

It most certainly is NOT what most stick drivers do; for one thing most stick owners have figured out brakes are a LOT cheaper to replace than a clutch, and that's essentially what you are doing by downshifting - saving your brakes at the cost of vastly increased clutch wear...

eccles

As a wise instructor once told me:

MikeW

This is called 'throttle braking' try this on a diesel and you get nothing, no braking [got jake brake]

Anyway the throttle by wire system has a program for 'drag torque regulation' that controls how much (or little) the throttle should remain open when you lift off completely

using throttle braking on a front wheel drive car will cause understeer, using throttle braking on a rear wheel drive will cause oversteer, but since the Rx-8 will have a torque sensitive differential that oversteer will be partially mitigated.

nk_Rx8

I have always downshifted when slowing. Is there any extra wear and tear? Who knows? I've never had to replace an engine or tranny. None of my car friends have had any extra tranny/engine service that could be related to engine braking. And we're not talking about gentle driving with just a bit or engine braking drivers here, they all are hard driving/engine braking/heel-toeing/road racing/autcrossing people.
In fact, they just checked my tranny fluid at my last oil change and they said it was clean as can be. People gotta remember we're not talking about slamming into 2nd from 5th at highway speeds and getting that nose dive affect here. It's actually very smooth and done along with using the brakes. I wouldn't be worried about engine or tranny wear, but just be sure you are rev matching or the clutch will get extra wear.

Maybe my car will not get to 300,000 miles, but only make it to 250,000...or maybe it will. Who cares... I doubt anyone will still have the car then. To me this is a non-issue realistically. It's sort of the same thinking that some of my parents friends still have about how you can't have a 4cylinder car vs a 6 or 8 because higher revving cars can never last as long - too much wear and stress. Well I would bet on a Honda lasting longer than a Buick anyday.

Again, this is one of those issues that have been going on forever, but will never be resolved. Just drive safely and enjoy yourself!

Y&Y

I myself used to engine\throttle\tranny break all the time, now I only do it when I need to stop very quickly especially on the freeway. I find it faster to engine break then trying to break hard during sudden stops\slow downs. I hate anitlock brakes. It always gives me that jerky feeling. If I have to speed again then I wouldn't have a problem since I'm at a lower gear. But as for wear and tear I really don't think engine breaking would wear down the tranny all that much faster. If anything it'll probably just wear down the clutch a little sooner.


But engine breaking all the time will just consume more fuel.

Smoker

Maximus,
The first thing you should do is to fully understand how the manual transmission works. If you have doubts, go to www.howstuffworks.com, they have animations and pictures to show you exactly how it works.

Let me just briefly illustrate what happens when you just down shift to a lower gear. For example, you are happily cruising along at 60MPH, you engine turns the clutch, the clutch drives the layshaft, the layshaft drives the gear in the transmission ....etc etc.... all the way to the wheels. Everything is happy. Now you decided to down shift, all of a sudden you are making all the machinery in the drive train works a little bit backwards (in terms of power transfer), the gear is now forcing the layshaft to spin faster and therefore the clutch, needs to spin faster and therefore the engine got start turning faster. This is why the engine goes "rooooam" and the rpm goes up even with the foot off the pedal. Since you are not putting any extra fuel in engine, the engine is trying to slow down but the rest of the drive train is forcing it to move faster than it is suppose to. Anyhow, you are basically created friction and resisitants in your drivetrain to slow down the wheels.

Now old school drivers will tell you that the mechanics of drive train are built to transfer the force from the engine to the wheels and NOT the other way around. Nowadays, many people thinks the engine and the parts are now a lot more durable and what drives what, it really doesn't matter since you are still putting force on them anyway.

Bottom line is if you want to downshift to slow the car, make sure you are rev matching. That way, at least you are saving your clutch. If you can, double clutch and rev match, this will further reduce the wear and tear on your drivetrain (layshaft gearing, sychronos, etc ).

The best advise I can give you is that if you know how it works, you will know how to maintain it.

-Smoker

Maximus

Thanks everyone for posting ur experiences with engine/transmission/throttle braking.

Doctorr's response was the closest w.r.t. to rotory engine.

To recapitulate dont worry too much about it generally and specifically with the rotory. At the same time dont punish the engine too much, match the revs, of course avoid down shifting from 5th to 2nd etc. in trying to come to a complete top. Just use the this kind of braking, if that is your driving style, in conjuction with the regular brakes. Go with your instincts.

Does that summarize it all?
(more discussion is welcome however!)

Sputnik

Gimme a break... You don't wear out the clutch when engine braking, unless you are slipping it excessively (as in having it half-way in/half-way out).

---jps

BillK

Any time you use the clutch, it wears.

Go through the gears both up and down and you will be making 2x the shifts, and wearing the clutch more by definition.

Add the fact that most people cannot rev-match precisely on a downshift and most downshifts tend to wear the clutch a bit more than upshifts do.

Bottom line is that engine braking per se does not wear the clutch, downshifting back through the gears on your way to a stop does.

TheSaCK

I sell Trannie parts and Do repairs. I have a pretty good grip of how a trannie works. Down shifting and actually using the break peddle to slow down seems to come up once in awhile.

And as Tribal Azn has stated ... all down shifting does is wear your trannie down. Such as the synchro gears, and the clutch assembly. After all everytime you change gears the synch gear have to adjust to the engine rpm, and everytime u clutch, the throw out bearings have to release and the re apply and the clutch surface gets worn.


Break pads, are easier to use no? even to replace them is less work and less costly. Break components such as the Master cylinder and junk rarely go out. only things that ever need replacing is the pad ad the rotor. pads cost 40-80 bucks OEM (20 bucks after market) rotor can be re-surfaced and if you use it right. last forever.. cause the i havent change rotor on my any of my cars yet.

Trannie parts cost as follow. typical import car synch/bearing kit runs you 120-200 bucks (OEM, not dealer but LUK) and the clutch also runs you typcially 100-150 (LUK, OEM) not only are the parts more expensive, the labor to drop the sucker is a lot more. typicall labor on standard trannie is 200-400.

Conclusion. Use the break, more work for your feet, but saves in the long run. But then again its less engaging of a driving experience.

tribal azn2

thats what i was trying tell everyone but no one seems to listen.

im taking auto shop class at my high school and my teacher told us all about it.

we also learned all about brakes. we did brake pad replacements and brake jobs and they r unbelievably easy to do. i can only imagine how hard(and expensive) it is to repair or replace a damaged tranny.