Best To Downshift, or Ride Brakes Downhill?

inthered

Veteran Member
Joined
Nov 7, 2004
TDI
2013 Passat
I wouldn't kick it in neutral and coast/brake. Others will tell you to do it to replace brakes not engines however do you do the same thing in an automatic? Seriously who throws their automatic into neutral down a hill? Maybe just a few and some of those few are probably hyper milers.

Leave the car in gear maybe drop 1 gear and use the brakes appropriately. I wouldn't downshift gears to the point where you are at 3,000 rpm or anything.

It's also a safety decision to do this as well.

Before I get flamed I'm also a professional driver and driving instructor for a Fortune 50 company.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
I hope you're not the one training OTR truck drivers to camp in the middle lane of three all day. :eek:
 

wrenchman30

Veteran Member
Joined
Oct 1, 2007
Location
arkansas
TDI
2005.5 gray 2006 dark blue
almost three pages of people who do not know how engine brakes work,

so I will try to explain it so you understand

a diesel engine is high compression gas is not so more force is required to compress the air

at exactly 2 degrees before top dead center the exhaust valve is held open to get maximum compression but yet dump the air into the exhaust (think large air compressor at this time)

the compressed air in the exhaust speeds up the turbo making more boost thus making more engine braking (more air in cylinder to compress)

exhaust brakes (flap that plugs the exhaust) does the same thing just a lot more ineffective since the boost dump is absent
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
almost three pages of people who do not know how engine brakes work,

so I will try to explain it so you understand

a diesel engine is high compression gas is not so more force is required to compress the air

at exactly 2 degrees before top dead center the exhaust valve is held open to get maximum compression but yet dump the air into the exhaust (think large air compressor at this time)

the compressed air in the exhaust speeds up the turbo making more boost thus making more engine braking (more air in cylinder to compress)

exhaust brakes (flap that plugs the exhaust) does the same thing just a lot more ineffective since the boost dump is absent

TDIs do neither of these things.
 

fxk

Veteran Member
Joined
Mar 12, 2015
Location
Vast wilderness between DC and Baltimore
TDI
2014 Sportwagen TDI
(sigh)
Not going to hurt an engine using engine braking unless it's already broke.
Don't redline the engine trying to get enough braking. Redlining is a no-no whether it is under power or unfueled.
Manual gearboxes will give one better access in general to whatever engine braking is available than auto/slush/dual-clutch.
All IC engines will have some degree of engine braking. Gas engines typically have more engine braking capability than diesels.
Thems is the facts. Plain and simple.
Over and out.
frank
 
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VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
Joined
Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
I'm not sure how a manual gives you better access to engine braking than a DSG. :confused:
 

fxk

Veteran Member
Joined
Mar 12, 2015
Location
Vast wilderness between DC and Baltimore
TDI
2014 Sportwagen TDI
If nothing else, manual control of the clutch engagement.
Also possible to skip gears, rather than rolling through the box sequentially.

I know some autos have one-way clutches that allow the tranny to freewheel rather than leave the "gears" engaged for engine braking.

I do not know if / how much is programmed into the dual clutch tranny.
 

Grahamexl

New member
Joined
Sep 14, 2019
Location
Cincinnati
TDI
2002 jetta Wagon
I wouldn't kick it in neutral and coast/brake. Others will tell you to do it to replace brakes not engines however do you do the same thing in an automatic? Seriously who throws their automatic into neutral down a hill? Maybe just a few and some of those few are probably hyper milers.

Leave the car in gear maybe drop 1 gear and use the brakes appropriately. I wouldn't downshift gears to the point where you are at 3,000 rpm or anything.

It's also a safety decision to do this as well.

Before I get flamed I'm also a professional driver and driving instructor for a Fortune 50 company.



Hi, my dad was a driving instructor and he taught me the things he knew well and thought right. But when I went to a driving school, they just ignored those aspects. It seems to me that not all professional drivers can know everything about the car.
And specific situations and cars/trucks require additional knowledge.


The problem is that drivers are lacking important skills. And it's often a psychological/age gap between an instructor and a trainee. And here's what makes a good driver: https://transfersmagazine.org/what-makes-a-good-driver/

I noticed that the modern youth is often overestimating their knowledge and skills and even during driving lessons they think they know everything. So a driving school and practical training courses are crucial - for anyone who is looking for a driving school, don't be afraid of your instructor, choose locally https://drivingschoolnear.me/ - and just pay attention to the details.
 
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740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
I'm not sure how a manual gives you better access to engine braking than a DSG. :confused:

well there was that elusive over run feature that hasn't been confirmed on the 2012 Passats.

Either way our '15 will down shift and hold the car back pretty good around 3000rpms. It only downshifts when you hold the brake pedal consistent for 5+ seconds or so.
 

BroncoAZ

Veteran Member
Joined
Apr 25, 2009
Location
Flagstaff, AZ
TDI
2015 Touareg Lux, 2015 Passat 6MT, 2009 Jetta (long gone), 2011 Touareg (bought back 02/18)
My 2015 6MT will gain some serious speed going down mountain grades. At the top of the hill on I-17 about 30 miles south of Flagstaff if I start the hill at 80 the car will be doing 100+ at the bottom without input from me. Downshifting to 5th or 4th doesn’t make much difference, so I use the brakes. I just replaced my rotors last month, they were badly warped. Rather than riding the brakes down the hill I give them a firm application to get down to 75 prior to each place where the patrol cars like to sit and then let it coast back up to 83 or so before braking again. We’ll see how long these brakes last, the Zimmerman rotors and ceramic pads are great so far.

In my former Touareg TDI I would manual shift back to 7th gear and it would hold 80 down the hill nicely.
 

Ramosian

Member
Joined
Jun 9, 2012
Location
Hollister, MO
TDI
2000 Jetta GLS TDI, 2013 Passat TDI SEL
Being a person who drives both a 15 liter diesel and a 2 liter TDI, most of you don't understand engine braking of diesels. At 40 tons, you learn a lot about slowing on downgrades. Dropping one gear makes a lot of difference to the point of not needing the jake. In terms of the TDI, my Passat will slow dramatically more, with it's 2 liter and weighing only 400 pounds less than my Mazda CX-7 that has a 2.3 liter gas engine. Both of these vehicles are turbocharged, and both have some form of select-able automatic transmission. In the gasser, I will gear down to a gear that puts the rpms up roughly 1000 more than in the TDI.
 

TDI321

Active member
Joined
Aug 19, 2018
Location
Space Coast FL (321 area code)
TDI
2015 Passat TDI SEL, phase 2a
Chinese rotors and pads are way cheap. High compression engines have more engine braking ability than low compression gas engines - TDI is high compression. I’d downshift one gear, leave it there and cycle brakes on and off.

Never go crazy with car brakes taking all the stopping. Once had a truck overheat brakes on a mountain road, rotors got white hot, piston blew out and the brakes caught on fire, dumping flammable brake fluid onto white hot rotors. Wife was behind me on the GMS screaming there is fire under the truck and oils is raining on her windshield. A Ryder rental truck with forged brake inspection records from a mechanic not properly trained. $700 rental cost them $5000. Everything I owned was in the truck, got the fire out in time. Thank God for air park brakes and a flat section before the big drop and sand run-away.
 

Jaden

Member
Joined
Apr 11, 2020
Location
Gresham, Oregon
TDI
1998 Jetta
Diesel engines generate little to no engine braking, due to the engines being fuel throttled and not air throttled. Downshifting to slow the car is near useless and will only increase wear and tear especially when done cold. This is the reason that large trucks use jake brakes and/or an exhaust brake to help slow the vehicle down.
I tried the exhaust brake on my stick shift Jetta but it sets off the check engine light. The code is for mass air flow circuit range/performance.
 

Tom in PT

Veteran Member
Joined
Jun 7, 2017
Location
Twilight Zone, WA State
TDI
2005 Passat sedan - SOLD; 2013 Passat DSG; both purchased new
That hill reminds me of sections of I-70 descending into Denver (around 7,000 feet of elevation lost). But only 6 % grade.

I drive one route towing a trailer with a 14 % grade for 3 miles with hairpin turns. A bit more challenging than I-17.:D
 

740GLE

Top Post Dawg
Joined
Aug 19, 2009
Location
NH
TDI
2015 Passat SEL, 2017 Alltrack SE; BB 2010 Sedan Man; 2012 Passat,
AZ is great for elevation gain/loss.

How are the new rotors and pads holding up?

So far we've put about 25K on just new rotors, original pads and no pulsing yet.
 
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