Engine Braking?

SPDMarine

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Richland, WA
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2001 New Beetle TDI-GLS
I checked the FAQ and couldn't find an answer to this question, so here goes: I'm wondering if it's okay to use engine braking with a 1.9L VW diesel. The engine is in a 2001 New Beetle TDI-GLS... just got it last night. Very fun to drive! I have a coworker who owns a 2002 Jetta with the same engine, and he cringes every time his RPMs go over 2000. He also advised me to never use engine braking. I'm wondering if that's good advice.

Thanks in advance,
Sean in Richland WA
 

whitedog

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SPDMarine said:
I checked the FAQ and couldn't find an answer to this question, so here goes: I'm wondering if it's okay to use engine braking with a 1.9L VW diesel. The engine is in a 2001 New Beetle TDI-GLS... just got it last night. Very fun to drive! I have a coworker who owns a 2002 Jetta with the same engine, and he cringes every time his RPMs go over 2000. He also advised me to never use engine braking. I'm wondering if that's good advice.

Thanks in advance,
Sean in Richland WA
Fortunatley for your cow-orker, Oldpoopie will soon be on the correct side of this continent and he will be able to clean the intake manifold and help him with the turbo that is getting sooted up from those driving habits.

As to the engine braking, why does he say not to do it? What is he basing it on? What will be the consequences of engine braking? Ask him these questions and if the answer to all of them is something along the line of, "I dunno, it's just what *** told me", then don't get any more car advice from him.
 

TornadoRed

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SPDMarine said:
I have a coworker who owns a 2002 Jetta with the same engine, and he cringes every time his RPMs go over 2000.
Congratulations on your new-to-you TDI.

I let my sister drive my Golf a year or two ago, and I cringed when she ran it up to 4500 rpm before shifting.

But I don't cringe when I do it myself. (4000-4200 is really my normal top rpm.)

Your co-worker is not doing his engine any favors by babying it. TDI engines are pretty tough, but they need regular exercise.

Engine braking is not particularly effective with TDI engines, but I do it all the time. It's one of the many reasons I prefer a manual transmission. I suppose if I had an automatic, I'd downshift manually.
 

DMJWilliams

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TornadoRed said:
Engine braking is not particularly effective with TDI engines
Indeed - you get a lot less than with a petrol engine. It wasn't what I was expecting at all - I expected the higher compression ratio would give good engine braking, but it seems that the lack of a throttle more than offsets that.

SPDMarine said:
he cringes every time his RPMs go over 2000
That's the advice of somebody who really doesn't understand his engine, and thinks he's driving an old fashioned tractor. Please ignore him, for the sake of your engine! Follow his advice, and your engine will give you no end of problems and ultimately have a short and unhappy life. Modern diesel engines are designed to be high revving - once the engine is warmed up you should have no qualms about taking it all the way to the red line, although the useful power drops off rapidly after 4000 rpm.

Seriously, these engines really do like to be exercised. I notice that mine drives much better after it's been driven hard with a heavy load in the car.

On the subject of whether you should use engine braking - the answer is "sometimes", although the answer has got nothing to do with what's good/bad for the engine. When slowing down, you shouldn't go down through the gears because it's not necessary. The brakes are more than capable of slowing the car by themselves, so let them do their job. Leave the car in gear, with the clutch engaged, and only declutch when the revs get too low. Going through the gears forces you to keep taking your hand off the wheel, which compromises your control of the car (albeit only slightly).

However, when going down a hill it's very good driving practice to be in a low enough gear so that the car isn't constantly trying to run away from you - it's simply about keeping the car under control with minimal intervention from the driver. A good rule of thumb is that you should go down a hill in the same gear that you would go up the hill - I'm not talking about revving the hell out of it! Having said that, the TDI often doesn't quite give enough engine braking to keep the speed fully under control down a hill, so small dabs of the brakes will often be necessary.
 
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RichDiesel

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Do your co-worker a favour, and send him here to this site. There is an overwhelming amount of information here that should be more then convincing to him. It sounds like he really needs to do some reading before his repair bills start to pile up.
 

BleachedBora

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Actually, I wouldn't do engine braking over 3k RPM or so--if you have/had a boost gauge you will notice that it will start "showing boost" as you get over 3k, and even get up to 5 lbs+ at 4k. This I have come to find out causes havoc with the turbo oil seals, which need positive pressure. In any case, I think all my engine braking contributed to some of BlackenedBora's problems. Anything under 3k RPM is fine, but I would consider that the redline of engine braking.
Hope this makes a tiny bit of sense at 2AM--goodnight! :)
-BB

PS Sounds like your friend needs an Italian tune-up! :p
 

devonutopia

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haha! I cringe if I DON'T get my revs over 2000. :D

I do use engine braking a lot, and with a degree of foresight, you can pretty much bring a TDI to a halt just using the gears (including using 1st ;)) Can confuse people seeing you slow down with no brake lights though - then they see them come on at the last second.

TDIs are very good at slowing down with engine braking and it eases brake pad wear - Also feels a more natural way to slow down, just sort of coasting in gear, and down the gears.
 

Joe_Meehan

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Have fun with your new TDI.

Don't worry use engine braking as needed. It is safer than always relying on the brakes if you are driving in the mountains.

The only thing with the TDI is you will find you have less engine braking than you would in a gasser.
 

tailpipe

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The responses were right on the money. Diesels for the most part are designed to be used hard. If you are an oil sampler you will quickly find out that if you pull a sample after a long hard trip, that is heavy engine loading either with mountains, weight or speed or a combination of all three your oil sample will be very good. As far as engine braking, not to engine brake is a waste of RPM's .

BB this may be true on the oil seals... think about this for a minute.. a big truck will show the same boost under heavy engine braking, If you read the operators manual you will be told to reach maximum engine braking keep your RPM's close to the red line . Of course this is with a true Jake brake . There are no limitations as far as time or boost. Matter of fact you need to be close to red line and in a gear that will hold you on the grade without using the footbrake. If you don't do this ...giddy up here we go.
 

TDI_SC

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devonutopia said:
TDIs are very good at slowing down with engine braking and it eases brake pad wear - Also feels a more natural way to slow down, just sort of coasting in gear, and down the gears.
With all due respect, that's retarded. It changes the wear from the brakes to the clutch. A brake job is a HELL of a lot cheaper than a clutch job!!

I only compression brake when going down big-long-hills.

JP
 

tditom

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Using "retarded" to show your degree of opposition to something is offensive to some people.

Engine braking, if done correctly, should not reduce the life of the clutch. Quickly releasing the clutch (at an appropriate speed for the gear selected) prevents slipping.

I downshift/engine brake all the time when coming to a stop from >40 mph.
 

whitedog

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Using "retarded" to show your degree of opposition to something is offensive to some people.
Yep. The sentence would read just as well if the word "stupid" or "whitedog" were inserted.
 

SPDMarine

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Thanks a lot y'all. I've told my wife to try and keep the RPM's down between 1500 and 2000, but it seems that's not necessary. I also drove the car a few days myself (she was intimidated) and started using the -admittedly limited- engine to brake. It seems a waste to brake with 2nd or 1st gear, but 4th and 3rd do a great job. Based on the years of experience this forum's members are willing to share (thanks a bunch, by the way), I'll let her know it's okay to shift when the RPMs go over 2500, which was the limit my coworker advised. She'll love that since she's got some lead in her foot :)

In defense of my coworker, he's a very intelligent guy, just conservative. I'm not sure where he learned his diesel driving habits, but I'll definitely point this forum out and see if he chooses to cut loose.

Once again, thanks a bunch!
 

Joe_Meehan

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I am going to add to my comments. There is engine braking and engine braking. Using engine braking when going down long hills or allowing the engine to slow down the vehicle while in the same gear your were already in, is good.

Down shifting at every light or every time you stop is likely to be far more costly in terms of clutches and or transmissions than just using the brakes.

I suspect some of the responses may have been thinking in terms of one or the other use.
 

cp

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if you have/had a boost gauge you will notice that it will start "showing boost" as you get over 3k, and even get up to 5 lbs+ at 4k. This I have come to find out causes havoc with the turbo oil seals, which need positive pressure.
I don't see how this is thermodynamically possible. There has to be energy in the exhaust gas to cause the turbo to create boost, and when coasting, there is no fuel being injected to give the exhaust any energy to do this. This would be analagous to using a water wheel (with no external energy source) to speed up the flow of a stream--show me how to do this and we will have the prototype for a perpetual motion machine.
 

Bob_Fout

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cp said:
I don't see how this is thermodynamically possible. There has to be energy in the exhaust gas to cause the turbo to create boost, and when coasting, there is no fuel being injected to give the exhaust any energy to do this. This would be analagous to using a water wheel (with no external energy source) to speed up the flow of a stream--show me how to do this and we will have the prototype for a perpetual motion machine.
Gravity.

The engine is still sucking in air, compressing it, moving pistons up and down, and expelling that same air. The energy used to turn the engine that previously came from fuel is now coming from the tranny/tires, powered by gravity.
 

cp

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Nope. The energy supplied in that fashion went to compressing air--then the compressed air gave back the energy it had by pushing on the piston.
 

Bob_Fout

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cp said:
Nope. The energy supplied in that fashion went to compressing air--then the compressed air gave back the energy it had by pushing on the piston.
Maybe so.

Buuuut....do you deny.... that air is exiting the engine? That exiting air is going through the turbo? That the turbo is spinning? That a spinning turbo creates boost? :)
 

Bob_Fout

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cp said:
Nope. The energy supplied in that fashion went to compressing air--then the compressed air gave back the energy it had by pushing on the piston.
Ahhhh...I don't buy it :)

This is really simple and it doesn't involve compressed air getting or giving energy. Replace fuel with the tranny as THE source of energy that turns the motor. The engine is turning w/o combustion and is still taking in and exhausting air.
 

cp

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At any given rpm, a non-combusting (coasting) engine can only move displacement*rpm/2 cubic units of air through it. When coasting, it is nothing but a pump--air out HAS to equal air in. If the turbo is creating boost, then the above equation is violated--the engine would be moving more air through it than a naturally aspirated version of the same engine at the same rpm. It would take energy to do this, and the turbo can't supply it--it's nothing but a couple of wheels on a common axle.
 

jwlionking

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tditom said:
TDI SC-

Using "retarded" to show your degree of opposition to something is offensive to some people.

Engine braking, if done correctly, should not reduce the life of the clutch. Quickly releasing the clutch (at an appropriate speed for the gear selected) prevents slipping.

I downshift/engine brake all the time when coming to a stop from >40 mph.

This can be accomplished by a technique I learned while driving larger trucks - I blip the go pedal, as the clutch is disengaged, to bring the RPM up to where the engine will see when the lower gear is engaged. This virtually creates very little friction between the clutch and pressure plate and seems to drop into gear much easier...
 

Audiofyl

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properly downshifting doesn't cause any more or less wear on the clutch than does normal upshifting. proper downshifting includes rev matching the engine to the appropriate engine speed so that you do not ride the clutch as you let it out to bring the rpms up to the proper level. downshifting also allows for you to be able to accelerate out of a potential problem situation instead of coasting at 30mph or less in 4th or 5th gear and not having any power available should you need it.

next time you're slowing down next to a fence or wall to your passenger side, roll down the window as you downshift. You can hear the turbo spooling slightly. I don't have a boost gauge in my tdi to be able to verify dowshift boost pressure, but i heard prior to this thread 1-3psi.
 

Long_Range

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SPDMarine said:
Thanks a lot y'all. I've told my wife to try and keep the RPM's down between 1500 and 2000, but it seems that's not necessary. I also drove the car a few days myself (she was intimidated) and started using the -admittedly limited- engine to brake. It seems a waste to brake with 2nd or 1st gear, but 4th and 3rd do a great job. Based on the years of experience this forum's members are willing to share (thanks a bunch, by the way), I'll let her know it's okay to shift when the RPMs go over 2500, which was the limit my coworker advised. She'll love that since she's got some lead in her foot :)

In defense of my coworker, he's a very intelligent guy, just conservative. I'm not sure where he learned his diesel driving habits, but I'll definitely point this forum out and see if he chooses to cut loose.

Once again, thanks a bunch!
Thing to keep in mind is. These are 1900cc engines with a piston stroke of about the width of a hand. Just because they burn diesel fuel does not make them truck engines. Piston speed is the measurement you want to look at.

3,000 rpm is the standard shift point. You want to keep the rpms above 2,000 after the shift. If you are planing to accelerate.

The only reason not to rev these engines to the red line, shown on the tachometer, is there is no power to be gained past 3,800 with an unmodified engine.

I have good news:) You can tell your wife she can run the TDI as hard as her heart desires or the Police will allow. Whichever comes first :eek: Simple fact is. If you are running any modern VW hard enough to cause damage. Your drivers license will wear out way before the engine will!

Engine Braking: AJ Foit wrote. " Brakes are cheaper than engines." Or was that Richard Petty?
 

cp

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usa
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This can be accomplished by a technique I learned while driving larger trucks - I blip the go pedal, as the clutch is disengaged, to bring the RPM up to where the engine will see when the lower gear is engaged. This virtually creates very little friction between the clutch and pressure plate and seems to drop into gear much easier...
Most big trucks are shifted without using the clutch at all.
 

Borborygmi

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Some big diesel rigs employ a true engine brake. This is done by opening the exhaust valves near the end of the compression stroke. Makes a hell of a noise, but prevents the recovery of the energy used to compress the air.

I use the engine for braking on downgrades, even if I have to shift into as low as third. As far as downshifting and using the clutch for routine stops, I prefer to use the brakes. That is what they are there for.
 

TornadoRed

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SPDMarine said:
I'll let her know it's okay to shift when the RPMs go over 2500, which was the limit my coworker advised. She'll love that since she's got some lead in her foot :)
Tell her that not only is it okay to go over 2500, but she should always rev to at least 3000 before shifting when the engine is warm. (2500 when cold)

3500 or even 4000 is fine.
 

kwong7

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I engine break all the time...in all my cars (all 5 are manuals). I never downshift drastically, usually revs around 2,000 after the downshift. When in doubt, consult the message board here, there's a ton of knowledged individuals that dwell and lurk here. Next, consult the VW owner's manual, they also recommend engine braking.
 

Long_Range

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cp said:
Most big trucks are shifted without using the clutch at all.
Well he said “larger trucks”. I'll read that as meaning larger than a pickup truck. Big trucks do not have synchronized gears. Leaving no synchronizers to strip. Sifting gears in a “big truck” will be a slow process any way you go about it.

Can't imagine working one of those big heavy clutch pedals on a semi through every gear. Never meet anyone that Herculean. Suppose if I did they would have a Popeye left leg and an Olive Oil right leg. Constantly walking in circles and such.
 

whitedog

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I worked with a guy that not only clutched at every gear, but double clutched and he hit every gear regardless of the load. Most of our service truck drivers don't use the clutch for shifting though.
 
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