Lost Performance

airmon · **Joined:** Mon May 23, 2011 2:25 pm **Posts:** 19

We're experiencing some issues with lack of performance with Lana, our '06 CRD.

It starts and sounds fine, but just doesn't have the 'punch' it used to have. We're east of the Sierras ( just outside of Lee Vining ) and long inclines at highway speeds are more of a struggle than we're used to.

We have: Cleaned MAP sensor, replaced the air filter and there don't seem to be any CAC hose leaks, checked the boost controller filter.

My suspicion is a lack of boost. When you floor it, boost ( measured by OBDII and Torque ) jumps to 16 inches for a second, then drops and hovers at about 8-12 inches.

Here's a graph from Torque. I have no idea what the numbers along the side represent ( I can find no definition for them when creating this graph ) but this is me stomping on the go pedal.

Point 1 is where the pedal goes to the floor.
Point 2 is a big spike of boost ( you can feel it in the seat of your pants ), then quickly falls off to 8 inches or so.
Point 3 is where the 1-2 shift happens and boost recovers somewhat.
Point 4 is the boost maxing out at about 12 inches, then falling back off.
Point 5 is the 2-3 shift, boost climbs a little, but not much.
Point 6 is me lifting off the 'throttle'.

FYI, I did this with traction control off, at about 6k altitude, on pavement and I've got a powertrax locker, so there was zero wheelspin.
I'm looking for where to go from here for diagnostics.

flash7210 · **Posted:** Wed Jul 05, 2017 8:51 pm

Are you on a stock ECM tune, GDE, or other?

My best guess would be a boost leak.
I noticed a slight loss of power and boost not being quite what it should be but no underboost code.
Found a small split on the underside of a cac hose.
Replaced the hose and all was better.

If you havent already, I recommend deleting or blocking your EGR valve.

airmon · **Joined:** Mon May 23, 2011 2:25 pm **Posts:** 19

GDE eco. (it's in my signature....)

I will pull the CAC hoses.

I just checked and I have vacuum on the line to the turbo solenoid and when I pull the vacuum line to the turbo, the lever moves about a half inch.

So I don't think a vacuum line or actuator issue is my problem.

WWDiesel · **Posted:** Wed Jul 05, 2017 9:31 pm

Have you blanked off the EGR feed tube or completely removed the EGR system all together?
If not, you need to blank it off or install a Week's elbow which allows the total removal of all the EGR crap!

There is NO tune that will prevent EGR valve boost leakage! Only mechanical blank or Weeks elbow kit can totally eliminate possible boost leakage through the EGR valve...

See this thread for EGR Block-off Plate dimensions:> viewtopic.php?f=5&t=76576&p=804565#p804565

Week's elbow kit:> https://shop.sasquatchparts.com/product ... berty-crd/

:SOMBRERO:

airmon · **Joined:** Mon May 23, 2011 2:25 pm **Posts:** 19

flash7210 wrote:

Are you on a stock ECM tune, GDE, or other?

My best guess would be a boost leak.
I noticed a slight loss of power and boost not being quite what it should be but no underboost code.
Found a small split on the underside of a cac hose.
Replaced the hose and all was better.

If you havent already, I recommend deleting or blocking your EGR valve.

CAC hoses are fine.

airmon · **Joined:** Mon May 23, 2011 2:25 pm **Posts:** 19

A couple. Of other data points.
I have vacuum at the turbo control solenoid and when I pull. The line to the turbo, the control lever moves a half inch or so, and moves back when I reconnect it.

Here's an odd thing. When the engine is not running, but the ignition on so the obd is getting power, manifold pressure reads - 3.

flash7210 · **Posted:** Wed Jul 05, 2017 10:24 pm

airmon wrote:

Here's an odd thing. When the engine is not running, but the ignition on so the obd is getting power, manifold pressure reads - 3.

Most likely because of your high altitude.

Ive noticed the same thing. I dont remember exactly what the numbers were, but they were negative when at high altitude.

It might be worth a try to replace your MAP sensor.
And definitely try blocking off the egr.

GordnadoCRD · **Posted:** Wed Jul 05, 2017 11:35 pm

If you haven't already, cut your exhaust from in front of the CAT, to behind the muffler, and replace with your choice of free flowing muffler or just a straight pipe.
What you describe sounds precisely like your boost system works great until the exhaust develops high backpressure due to a plugged CAT or something that's built up in the exhaust, most likely from the asphalt-producing EGR
The pinch point of the exhaust is in the range of pipe described above. The actual inner pipe diameter there is 1 7/8", at 4 points. Front and back of the CAT, and Front and back of the stock muffler.
Before and aft of those points, it's a true 2 1/2" pipe.
It's a very good mod to make, whether or not it's the cause of your grief, and WILL boost your performance, as well as likely bring down your exhaust temperature.

mass-hole · **Posted:** Thu Jul 06, 2017 11:07 am

Its simply reducing boost and power at altitude, its intentional. Its a misconception that a turbo can make up for all pressure losses due to elevation. A turbo has to spin faster to make the same boost at high altitude so there is a limitation to how much it can do and eventually boost must be reduced to keep the turbo from spinning too fast. Less boost means less fuel can be burn so fueling is reduced as well in an effort to prevent the engine from running too rich.

On your graph, the numbers on the left are likely absolute pressure in kPa. the natural output for the boost PID is 0-255 kPa and its actually doing a conversion to show it in PSI or in-hg or whatever units you view it in.

This is the map from the stock tune showing how much pressure it cuts based on ambient, the top numbers are the ambient pressure, the numbers in the bottom are the amount of reduction from the normal desired MAP. At 800 mbars(6500') you are looking at almost 10%. 700 mbar is around 11,000 feet i believe.

mass-hole · **Posted:** Thu Jul 06, 2017 11:09 am

airmon wrote:

A couple. Of other data points.
I have vacuum at the turbo control solenoid and when I pull. The line to the turbo, the control lever moves a half inch or so, and moves back when I reconnect it.

Here's an odd thing. When the engine is not running, but the ignition on so the obd is getting power, manifold pressure reads - 3.

Well yeah, you are at 6000'. Ambient pressure is only ~800 mbars there or 11.5 psi vs sea level where you are at 1000mbar or 14.7 psi. If you are reading the MAP in gauge pressure instead of absolute, that puts it at -3 psi.

I have totally stopped watching "boost." Any time I log in Torque it is absolute pressure because thats all that really matters. 20 psi of boost is different at sea level than it is at 6500' where I live.

Lost Performance

Who is online