Engine Braking

ABS · Oct 29, 2003

Good Morning TDI'ers!

I have been catching myself using the engine to brake my Jetta. Of course this is easy to do with the 5-speed. But I am curious, as to your thoughts and opinions on this technique. I grew up on a farm driving grain trucks, tractor trailers, etc., so engine braking is almost second nature to me. Down side is the Jetta doesn't have a Jake Brake

. I anticipate traffic, so rather than waiting until I am 25 feet from somebody and standing on the brakes, I will leave a large cushion, downshift and let the engine slow me down.

Have a great day.

jasonTDI · Oct 29, 2003

On these it is pretty pointless. Save your motor and use the cheaper brakes. I would do it while trying to brake the engine in, but other than than I don't downshift to slow.

compu_85 · Oct 29, 2003

Is engine breaking really hard on the drivetrain? It might be kinda hard for me to stop using EB, its kinda 2nd nature :$

dropFROG · Oct 29, 2003

If proper care is taken to match revs when down shifting, I don't see the problem. /images/graemlins/confused.gif

GeWilli · Oct 29, 2003

As Drop frog said... match revs

But, I want to add, when "engine braking" there is no fuel going to the motor, so any time you take your foot off the accelorator with the car in gear and the engine is above idle speed zero fuel will be consumed...

it could have the effect of raising your mileage depending on your driving habits and conditions....

DallasTDi · Oct 29, 2003

I always coast in-gear until it's time to get out of it. At that point, I do not downshift - I use my brakes. The TDi uses no fuel when coasting in gear. And I believe it's cheaper to replace brake pads than clutches, so I do not use the engine to brake except for coasting as described above.

dropFROG · Oct 29, 2003

/images/graemlins/grin.gif Heel-Toe BABY..!!

Lift the right foot from the gas pedal and press the brake pedal

Just before the braking is done, the left foot depresses the clutch pedal

The right hand downshifts (the left is still on the steering wheel)

The right foot is still applying, but easing up on the brake pressure, then rotates so the heel is above the corner of the gas pedal

The right heel gives a quick push of the gas pedal to rev the engine quickly (the ball of the foot is still on the brake easing up even more)

The left foot releases the clutch, the right foot rotate off the gas

The right foot completes the braking

The right foot slides over to the gas pedal to assume the normal position only to maintain some pressure to sustain the vehicle speed through the first part of the corner.

Then accelerating out of the turn.

GeWilli · Oct 29, 2003

thats all fine and dandy Mr Frog, BUT ya can't do dat so effectively on our cars with teh cutout switch...

anyone can demonstrate it... hold the engine revs around 2500 and then hit the brake pedal... notice anything /images/graemlins/wink.gif

snoopis · Oct 29, 2003

[ QUOTE ]
GeWilli said:
thats all fine and dandy Mr Frog, BUT ya can't do dat so effectively on our cars with teh cutout switch...

anyone can demonstrate it... hold the engine revs around 2500 and then hit the brake pedal... notice anything /images/graemlins/wink.gif

[/ QUOTE ]

If you hit the brake, then the accelerator, it works just fine. Get it bass-ackwards and you'll slow down in a hurry.

Although, rotating your foot like that just doesn't work for me. I just slid my foot over, so the left side is on the brake, and the right side of my foot is on the accelerator. Just sort of roll from brake to "gas."

-Nick

skywalker · Oct 29, 2003

Ok all performance chip manufacturers out there, Variable Geometry Turbos (which is just what TDIs are using) can be made into an effective exhaust brake (ie: Jacobs) /images/graemlins/eek.gif

Cummins is already doing this on their ISB w/ VG turbos, the turbo variable vanes can produce the necessary obstruction in the exhaust path to create an effective engine brake, it just need to be coordinated with the ECU.

jpcherry · Oct 29, 2003

[ QUOTE ]
snoopis said:
[ QUOTE ]
GeWilli said:
thats all fine and dandy Mr Frog, BUT ya can't do dat so effectively on our cars with teh cutout switch...

anyone can demonstrate it... hold the engine revs around 2500 and then hit the brake pedal... notice anything /images/graemlins/wink.gif

[/ QUOTE ]

If you hit the brake, then the accelerator, it works just fine. Get it bass-ackwards and you'll slow down in a hurry.

[/ QUOTE ]

It works if you double tap the accelerator. The first tap is for the fuel cut off, the second overrides it.

I've used this for autocross since I've had my TDI /images/graemlins/wink.gif

Sort of feels like dancing with the car...

tadc · Oct 29, 2003

[ QUOTE ]
compu_85 said:
Is engine breaking really hard on the drivetrain?

[/ QUOTE ]
No. Even if you dont rev-match, the wear on the clutch when accellerating the engine from 2000 rpm to 4000 rpm is negligible.

People say brakes are cheaper than clutches (true), but you're not trading brake lining for clutch lining directly and proportionally. You're trading (potentially) lots of brake lining(and warped rotors and whatever) for almost zero clutch lining(only enough to accellerate the engine 1 or 2k rpm).

This subject has been covered several times before. It's basically personal preference. Downshifting, even without revmatching, probably isn't going to make a noticable difference in your clutch life. It probably WILL make a noticable difference in your brake life, in my experience anyway.

compu_85 · Oct 30, 2003

I guess that's why i'm still on my original set of pads with about 1/2-1/3 left /images/graemlins/grin.gif
-Jason

major-poser · Jun 28, 2004

also it's not a fuel cut off, if you watch it settles at 1200 rpm. what about an exhaust brake? a flap in the exhaust stream? would that hurt anything? has anyone done it?

master cylinder · Jun 28, 2004

Uses NO fuel? What is the engine using for combustion to stay running at idle? If you can get an engine to run without a fuel source you will be a very wealthy person

.

mannytranny · Jun 28, 2004

I do this in every diesel I drive, and think its great. Far less wear on brakes. I also think its good for the engine. I dont know why, but it seems that my diesels seem to run better when compression braking has been done.....

It aint going to hurt a thing. Diesel trucks do it all the time.

I also do it when coming off the freeway. In the truck, the pyro gauge will fall to 150* after about 5 seconds of braking at 3200 rpm. Cools the turbo down fast.

I have no qualms about winding the TDI up to 4000 rpm every time I come off the freeway.

tadc · Jun 28, 2004

also it's not a fuel cut off, if you watch it settles at 1200 rpm.

it IS a fuel cut-off. When the ECU sees that RPM drop near idle, it starts supplying fuel again.

Rustynuts · Jun 28, 2004

When the car is idling, fuel is being used to keep the engine ticking over. However, when coasting, say downhill, the motor is being turned over by the motion of the car turning the wheels, transmission and finally the engine. The car's management and fuel system knows this and doesn't need to supply fuel to keep the engine turning until you either hit the go pedal or put your foot on the clutch. It only uses fuel when there is a demand for it.

MITBeta · Jun 29, 2004

When coasting IN GEAR that is...

TDILOVE · Jun 29, 2004

And I believe it's cheaper to replace brake pads than clutches

amen brotha!!!

i wouldent care if i went through a set of pads every 6 months if it meant extending my clutch life by one week. brakes are WAY less exspensive than a clutch is.
not to mention that a brake job is finished in about an hour.

spinfire · Jun 29, 2004

One should /always/ downshift on a long grade however. There the issue isn't brake wear, but overheating. By the time you figure out your brakes are overheating its too late..

GotDiesel? · Jun 29, 2004

Agreed, but even with the engine up around 3300 rpm and the foot off the pedal, there is not a whole lot of engine braking to be had in these cars.

When/if you do downshift, I think it is a bit easier on gear synchros as well as the clutch itself if you at least try to get the revs close to matching before you try to engage the lower gear.

SwimmerDave · Jun 29, 2004

Uses NO fuel? What is the engine using for combustion to stay running at idle? If you can get an engine to run without a fuel source you will be a very wealthy person

.

The engine is not idling. The kinetic energy (forward motion) of the vehicle is transfered through the differential, transmission, and back to the engine to turn it over. Thus, no fuel is required. Note that this is not a steady-state operation. There is internal friction in drivetrain, creating drag, which "absorbs" the kinetic energy (forward motion) of the vehicle, thus slowing it down, which is the whole point of this thread - engine braking.

However, our TDIs are not equipped with engine brakes like the big rigs are, so the drag created by coasting "in gear" is minimal. However, it is greater than the drag from coasting in neutral, so a little brake lining is saved.

In general, if one can plan well ahead when to brake, one can save a lot of wear and tear on one's braking system.

SwimmerDave · Jun 29, 2004

And I believe it's cheaper to replace brake pads than clutches

Click to expand...

amen brotha!!!

i wouldent care if i went through a set of pads every 6 months if it meant extending my clutch life by one week. brakes are WAY less exspensive than a clutch is.
not to mention that a brake job is finished in about an hour.

If a "brake job" only involved pads, I'd agree with you. However, more often than I would like, it usually involves replacing rotors as well - not cheap. So, I prefer to coast in gear and sometimes downshift - matching revs - when reducing speed on a long, downhill slope. Dang, I sure wish our TDIs had engine brakes. The sound would scare the piss out of anyone not expecting it

Cincy_Mike · Jun 29, 2004

A here's a pretty good explanation of engine braking and jake brakes

TDILOVE · Jun 29, 2004

sound like your allways replacing the rotors. maybe you should consider going to a different type of pad than the ones you have been using. rotors should last at least 3 sets of pads.

tadc · Jun 29, 2004

rotors should last at least 3 sets of pads.

Not on a VW.

major-poser · Jun 29, 2004

umm, does anyone know of side effects of the exhaust brake being used on our engines? increased wear because of stress? obliviously because of our soot producing engines regular maintenance of the valve is need, BUT about our engines? we really need somone with experience with an exhaust brake on a TDI. because i'm gonna do it if it doesn't kill my vavletrain, or hurt the turbo

JJ · Jun 29, 2004

I have always been a engine braker. I have never replaced a clutch and my brakes last what seems like forever. I have never worn out a engine or could attribute any negative side effect to engine braking. I think it is hard on the motor and transmission mounts but so far I have never had a problem there. Engine braking is not as fruitfull with the TDI vs. other vehicles I have owned, but I like the way it quickly cools off the turbo. Cool turbo = very good.

Also, I never match revs. Downshift and dump the clutch. If you match revs whats the point?

For me, engine braking rules. Now if I could just get my wife onboard.

GotDiesel? · Jun 30, 2004

Also, I never match revs. Downshift and dump the clutch. If you match revs whats the point?

The point is you don't have to worry about added wear on gear synchros, clutch lining or engine mounts if you match the revs.

Having to work on any one of those items will probably be more expensive than the savings on brake parts and labor.

Engine Braking

Veteran Member

TDI GURU Vendor , w/Business number

Gadget Guy

Veteran Member

Top Post Dawg

Veteran Member

Veteran Member

Top Post Dawg

Veteran Member

Veteran Member

Veteran Member

Top Post Dawg

Gadget Guy

Veteran Member

RIP, Gone But Not Forgotten

Top Post Dawg

Top Post Dawg

Veteran Member

Top Post Dawg

Veteran Member

Veteran Member

Top Post Dawg

Veteran Member

Veteran Member

Veteran Member

Veteran Member

Top Post Dawg

Veteran Member

Veteran Member

Top Post Dawg