Transit 3.2L Good exhaust backpressure numbers

Nathaniel Diagnostician Ashton, Ontario Posted   Latest  
Discussion
Driveability
Emissions
2016 Ford Transit-350 3.2L (V 99V) 6-spd (6R80)—1FTBW3XV9GKA51196
P2002 - Particulate Filter Efficiency Below Threshold Bank 1

Looking to see if anyone more familiar with these engines has known good backpressure numbers? At idle this one is running 10kPa (1.45psi). WOT acceleration, the scanner had a maximum reading of 431kPA (62.5psi). Highest reading I actually saw during WOT was 376 kPa (55psi).

No power concerns, just trying to decide if DPF needs cleaning or if I have a faulty particulate sensor.

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

You are working with a constip[ated exhaust system. At 55 PSI exhaust, the intake must be gurgling something terrible

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Nathaniel Diagnostician
Ashton, Ontario
Nathaniel Default
   

Right? You would think, but nothing. No driveability issues whatsoever. With no symptoms and no DTCs for backpressure, this is where I found myself questioning how much I don't know about these diesels. Now, those readings were taken using the backpressure sensor. It's possible that the accuracy of the factory sensor is unreliable at the far ends of the scale, or I have a separate issue with…

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

then you are not testing the actual back pressure. You are testing the exhaust pressure ahead of t he turbocharger. What led you to testing this? If you have no driveability problems, then what is the problem.

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Nathaniel Diagnostician
Ashton, Ontario
Nathaniel Default
   

No, the back pressure port is after the turbo, before the DPF. See attached (callout #4). The trouble code is the reason it's in for service. The fix for the code isn't going to be much of a mystery, that's why I posted this as a discussion instead of a question. My apologies, I should have been more clear in the original post. I've never seen readings like that, never mind on a vehicle that…

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Steven Mechanic
Spokane, Washington
Steven Default
   

Now you have me wondering what amount of backpressure is acceptable ahead of the turbo. I had a 2012 Mercedes 3.0L Diesel a couple days ago that had 15psi backpressure at idle and 60psi at around 2,000rpms, based on the sensor which is ahead of the turbo. I verified it with a gauge at the sensor hole. I didn't think about the fact that it was ahead of the turbo, but I'm sure 15psi is way too…

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Philip Educator
Hemet, California
Philip Default
 

Steve, are you sure you are not reading absolute pressure rather than gauge pressure? Atmospheric pressure at sea level is 14.7 psi so I would expect to see that at idle if the pressure reads in absolute. The turbo works by pressure differential across the exhaust side of the turbo so we need pressure upstream of the turbo so it will work.

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Steven Mechanic
Spokane, Washington
Steven Default
   

Yes, I took that into account when checking. KOEO was 950hPa, idle was about 2000hPa, and raising the engine speed, I don't remember the hPa number, but I remember it calculated out to about 60psi (after subtracting and converting). Also, checked it with a regular vacuum/pressure gauge at idle at the sensor hole. Not that I necassarily needed to use a gauge because 15psi coming out the sensor…

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Steve, thanks for taking the time to put this information up.

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Philip Educator
Hemet, California
Philip Default
 

There's not a chance that 55psi is a good number with no performance issues. Back-pressure at idle should be very close to zero. But is this the pressure sensor upstream of the turbo or the pressure sensor in the DPF?

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Nathaniel Diagnostician
Ashton, Ontario
Nathaniel Default
 

This sensor reads pressure from a ~1/2" port mounted in the front pipe, between the turbo and the DPF/converter assembly.

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Tanner Instructor
Wellford, South Carolina
Tanner Default
 

So now you have me wondering, any chance you would be willing to put a normal pressure gauge on that line and do a wot pull? Then we would know if the sensor is correct or not.

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Nathaniel Diagnostician
Ashton, Ontario
Nathaniel Default
 

Absolutely. I was hoping to have had a chance by this point today, but I'll do it first thing AM and post results.

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Nathaniel Diagnostician
Ashton, Ontario
Nathaniel Default
 

I apologize for the delay, but since the answer is pretty boring, I wanted to add some value to the discussion by including before and after data for the particulate filter replacement. The Ford DPF was 5+ business days to get in, plus time to get back to it, and run monitors afterwards to verify the repair. But here we are. The incredible backpressure numbers I saw on the Autel were, in fact…

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Thanks for the update. After working on many 7.3, 6.0, 6.4 & 6.7 diesels, I have found that using the EBP pid to analyze an exhaust restriction, such as plugged cat or plugged DPF is a waste of time. Since boost is caused by fuel being burned, the engine will not make boost if the exhaust will not flow, which caused high back pressure, which causes low turbocharger output, which causes low…

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Nathaniel Diagnostician
Ashton, Ontario
Nathaniel Default
 

I haven't spent all that much time looking at EBP on diesels, but from what you're saying, maybe that's just fine. What bothers me is not being able to pinpoint something outside of operating range before making a call. In this case, I knew that the particulate matter sensor was the main trigger for this trouble code, but determining if the sensor or the DPF was at fault came down to deductive…

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