CR140 Exhaust flap used as compression brake?

bloc

Veteran Member
Joined
Apr 25, 2006
Location
Austin, Tx
TDI
2013 Touareg TDI
I just bought a 20k mile 2010 Jetta TDI 6MT and am loving it, aside from one quirk when driving at freeway speeds. Sometimes when lifting off the throttle (usually downhill), OR USUALLY when hitting a dip (even pretty gradual, like between two hills), the car has a tendency to noticeably slow down as if I were hitting the brakes.. without me hitting the brakes. It is far more pronounced than normally lifting off the throttle, and reminiscent of an exhaust brake on a truck.

Does anyone know if the engine management in these cars is programmed to close the exhaust flap under certain conditions to increase engine braking? Or maybe the anti-shutter valve?

Does anyone know how I'd log exhaust flap operation? I dug around in VCDS a bit and couldn't find anything obvious, though I'm far from well-versed with this particular car.

Thanks for any info
 

DieselRacer

banned
Joined
Oct 4, 2013
Location
AZ-NV
TDI
BMW Advanced Diesel...2011 BMW 335d
I just bought a 20k mile 2010 Jetta TDI 6MT and am loving it, aside from one quirk when driving at freeway speeds. Sometimes when lifting off the throttle (usually downhill), OR USUALLY when hitting a dip (even pretty gradual, like between two hills), the car has a tendency to noticeably slow down as if I were hitting the brakes.. without me hitting the brakes. It is far more pronounced than normally lifting off the throttle, and reminiscent of an exhaust brake on a truck.

Does anyone know if the engine management in these cars is programmed to close the exhaust flap under certain conditions to increase engine braking? Or maybe the anti-shutter valve?

Does anyone know how I'd log exhaust flap operation? I dug around in VCDS a bit and couldn't find anything obvious, though I'm far from well-versed with this particular car.

Thanks for any info
exhaust flap is for your REGENS...it slows down the exhaust during... nothing to do with a brake for the car, its not an 18 wheeler...
 
Last edited:

bloc

Veteran Member
Joined
Apr 25, 2006
Location
Austin, Tx
TDI
2013 Touareg TDI
..except that it also is used for low pressure EGR function even when not doing regen. It is clearly there for more than just Regens. Since it is there, if VW felt the need to add some engine braking it would be easy to program the flap to do so. I'm looking for someone that knows definitively whether or not they did.

Is there a way to log exhaust flap function in VCDS?
 
Last edited:

TurboABA

Veteran Member
Joined
Jul 24, 2010
Location
Kitchener, ON
TDI
RIP-2010 Jetta 6spd 2014 Touareg Execline
.... OR USUALLY when hitting a dip (even pretty gradual, like between two hills), the car has a tendency to noticeably slow down as if I were hitting the brakes.. without me hitting the brakes.
I have experienced this, although I would say it's more like a releasing the accelerator pedal feeling, not like hitting the brakes......

Not sure what's causing it, but it sounds normal as my car has been doing it ever since it was new and it's been scanned for codes, etc lots of times.... no apparent issues.

It's actually still doing it even after having the flap replaced under the TSB

I wouldn't stress over it.
 

JM Popaleetus

Veteran Member
Joined
Mar 15, 2010
Location
Connecticut
TDI
Signature.
My 2010 has always "engine braked". I rarely ever gain speed going downhill, and IF I do, it's nothing that a simple downshift doesn't correct.
 

Dirtracr95

Veteran Member
Joined
Jun 24, 2013
Location
Des Plaines, IL
TDI
'13 Jetta Sedan DSG
Listen and see if you hear the turbo spool up off throttle. That was one of the features I could turn on or off with my programmer on my 07 powerstroke. When you would lift throttle it would move the vanes to spool the turbo and increase "engine braking". It was nice when going around corners because I could just mash the throttle again and not have to wait for it to spool.
 

bloc

Veteran Member
Joined
Apr 25, 2006
Location
Austin, Tx
TDI
2013 Touareg TDI
I think the turbo is generally too quiet to tell anything, but it would be pretty easy to log boost control solenoid duty cycle and see what happens. Thanks for that idea.. I hadn't even considered that it may be creating the back pressure in the turbine housing.
 

bloc

Veteran Member
Joined
Apr 25, 2006
Location
Austin, Tx
TDI
2013 Touareg TDI
I say braking because this isn't constant. Other times when I lift off the throttle the transition to no power is smooth.. when this happens it is very sudden and actually feels like something is acting to slow the car down for an instant. It even sounds like it is taking the slack out of the motor mounts.

I contacted Ross-tech and they didn't know of a way to log exhaust flap function. There is an output test for it, and that seems to go as expected. I'll try the diagnostic cable section to see if they have any input. There are a WHOLE lot of "unlabeled" outputs in the measuring blocks in VCDS.

I have experienced this, although I would say it's more like a releasing the accelerator pedal feeling, not like hitting the brakes......

Not sure what's causing it, but it sounds normal as my car has been doing it ever since it was new and it's been scanned for codes, etc lots of times.... no apparent issues.

It's actually still doing it even after having the flap replaced under the TSB

I wouldn't stress over it.
 

mose

Active member
Joined
Oct 15, 2011
Location
Baltimore, Md
TDI
15 Jetta SE TDI Auto
I have an 09 auto, and one thing I noticed is that the handbrake will overtighten the rear brakes. I've all but stopped using it past one click to turn off my drl's at times. But what I would recommend is clean your wheels then take a long drive. See if the rears are dusting faster than the fronts.
 

bassman5066

Veteran Member
Joined
Apr 8, 2011
Location
Honey Brook PA
TDI
2011 Golf 2 Door TDI (sold back for Dieselgate), 91 Golf 4 Door with 1Z swap
Listen and see if you hear the turbo spool up off throttle. That was one of the features I could turn on or off with my programmer on my 07 powerstroke. When you would lift throttle it would move the vanes to spool the turbo and increase "engine braking". It was nice when going around corners because I could just mash the throttle again and not have to wait for it to spool.
You just gave me an idea ;)

Thanks.

Sent from my VS920 4G using Tapatalk
 
Top