Scan Gauge II XGauge - EGT & Boost

rotarykid

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Apr 27, 2003
Location
Piedmont of N.C. & the plains of Colorado
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1997 Passat TDI White,99.5 Blue Jetta TDI
My Scangauge II came today. I programmed the boost x-gauge and first EGT per the initial post in this thread. EGT works fine and responds very quickly when you get into the throttle.

The boost gauge seems to work but gives slightly odd readings. When the engine is off it actually reads around -15psi, at idle it is about .6psi and then when you get into it it will jump up to 23.4psi which should be about right.

Two odd things I've noticed...

1) When cruising it reads about 1psi and when "engine braking" the PSI actually goes up to around 3psi. Not sure what that is, EGR maybe?

2) I think this is actually displaying commanded boost, not measured boost. When you floor it the boost jumps immediately to max even before you feel the turbo kick in.

UPDATE: This was showing commanded boost. Changing RXD to 4810 gave me actual boost and you can clearly see the turbo lag now. After it was showing actual boost I tweaked the MTH number to give me 0.0 with the engine off. I think I changed the last two digits to 75. Basically count in hex for each 0.1 PSI change you want.

Shawn

I have a scan gauge I & II, up in the metro Denver area my pressure readings at idle read around 11.5-12.5 psig......while closer to sea level back home it runs around 14.2-14.5......under normal conditions in an alh engine you can add ~12 psig to that reading at maximum boost......
 

VeeDubTDI

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My Scangauge II came today. I programmed the boost x-gauge and first EGT per the initial post in this thread. EGT works fine and responds very quickly when you get into the throttle.

The boost gauge seems to work but gives slightly odd readings. When the engine is off it actually reads around -15psi, at idle it is about .6psi and then when you get into it it will jump up to 23.4psi which should be about right.

Two odd things I've noticed...

1) When cruising it reads about 1psi and when "engine braking" the PSI actually goes up to around 3psi. Not sure what that is, EGR maybe?

2) I think this is actually displaying commanded boost, not measured boost. When you floor it the boost jumps immediately to max even before you feel the turbo kick in.

UPDATE: This was showing commanded boost. Changing RXD to 4810 gave me actual boost and you can clearly see the turbo lag now. After it was showing actual boost I tweaked the MTH number to give me 0.0 with the engine off. I think I changed the last two digits to 75. Basically count in hex for each 0.1 PSI change you want.

Shawn
Great! Thanks for the update for a 2015. I updated the first post.
 

Locoelectrician

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Can anyone confirm that the DPF temp sensor on the 15 is the same as the 12-14? Not the actual part number, but where in the stream it is. My DPF sensor does some really strange things compared to my 13. Sometimes on a downhill coast, the DPF temp will slowly rise, and then when I accelerate, it quickly drops the temp a few hundred degrees in a matter of seconds, like a rush of cool air hit it. Numerous times now i've seen EGT climb to 1000 and DPF drop from 600 to 400 while accelerating. My 13 DPF temp used to slowly follow EGT, although at a retarded rate. I wonder if the new system is using the exhaust valve much more to keep DPF temp up? In the 13, I never waited over 30 or so seconds for DPF to drop under 450. In this car, it sometimes takes up to 2 minutes AFTER egt hits 450 for DPF to drop that low. Boost is also strange (set to 4810). Shows -.2 at idle which is close enough for me, but sometimes when decelerating will show as low as -5, which would basically be vacuum. Other times it shows -.2 on deceleration. Would love to learn more as some strange new things seem to be going on in the exhaust. Engine braking also seems to be nearly completely gone compared to the 13.
 

VeeDubTDI

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Sounds like you aren't reading the first sensor, but one farther downstream that has a much more delayed reaction. I can't confirm what the coding for the #1 sensor should be on a 2015.

I also think you're correct that they're using the exhaust throttle a lot more, which would explain the DPF temp staying higher for longer and perhaps the (sometimes) vacuum that you're seeing on deceleration.
 
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Locoelectrician

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Sounds like we're agreeing in theory about the DPF. All I really care to watch temp wise is pre and post turbo so I can monitor regens and not cook things upon shutdown. I guess the way it is now I have start to finish of exhaust monitored, but I could care less about the non moving parts. If anyone comes up with a coding list for the 2015, please share. I remember a long time ago seeing a nice drawing of the 2013 engine that showed exactly where every component and sensor is. Then there was a list that said "bank 1 bla bla bla" for the scangauge. To wrap up, I'm pretty darn sure I'm not reading the sensor I want to be reading.

Any theory why this engine has no engine braking compared to the previous one? Maybe this isn't the right thread to discuss though.
 

Shawn67

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Ma
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2015 Passat SE TDI
On my 2015
07DF0178 05410678 3810 00090032FFD8 is pre-turbo (in F)
07DF0178 05410678 4810 00090032FFD8 is post turbo (in F)

First temp jumps very quickly and the second moves fairly quickly too but it obviously somewhat buffered by the thermal mass of the turbo.

I didn't have the scan gauge before Phase 1 but it is interesting to see all that the car does on occasion. About 90 seconds after startup the computer spikes the temps to around 1000 degrees for about a minute or so. I assume that is all about warming up the cat.

"Any theory why this engine has no engine braking compared to the previous one?"

Diesels should have almost no engine braking. Engine braking has nothing to do with compression (the compressed air just pushes the cylinder back down after compression) and has to do with a the downward moving piston fighting against the vacuum created by a closed throttle body. Since diesels don't have a throttle body they have very little engine braking. What there is if from friction and engine driven accessories such as AC, alternator, water pump, steering pump and so on. I think the 2015s have more electric driven accessories which is probably why you are noticing a different between it and earlier engine.

Shawn
 

Locoelectrician

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On my 2015
07DF0178 05410678 3810 00090032FFD8 is pre-turbo (in F)
07DF0178 05410678 4810 00090032FFD8 is post turbo (in F)

First temp jumps very quickly and the second moves fairly quickly too but it obviously somewhat buffered by the thermal mass of the turbo.

I didn't have the scan gauge before Phase 1 but it is interesting to see all that the car does on occasion. About 90 seconds after startup the computer spikes the temps to around 1000 degrees for about a minute or so. I assume that is all about warming up the cat.

"Any theory why this engine has no engine braking compared to the previous one?"

Diesels should have almost no engine braking. Engine braking has nothing to do with compression (the compressed air just pushes the cylinder back down after compression) and has to do with a the downward moving piston fighting against the vacuum created by a closed throttle body. Since diesels don't have a throttle body they have very little engine braking. What there is if from friction and engine driven accessories such as AC, alternator, water pump, steering pump and so on. I think the 2015s have more electric driven accessories which is probably why you are noticing a different between it and earlier engine.

Shawn
I would buy this if engine braking wasn't such a nice feature in my 2013. I drove it for 90k miles and every single day would downshift when exiting the freeway and it would slow the car considerably.

Edit. Where did you get your scangauge numbers from?
 
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Locoelectrician

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Post turbo does not seem to work on mine. Can you double check your numbers please?
 

Shawn67

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Ma
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2015 Passat SE TDI
I would buy this if engine braking wasn't such a nice feature in my 2013. I drove it for 90k miles and every single day would downshift when exiting the freeway and it would slow the car considerably.

Edit. Where did you get your scangauge numbers from?
After driving gas sticks forever I love the lack of engine braking. That is a large part of why diesels get better fuel economy. While cruising a small throttle positions they aren't burning extra fuel to overcome the partial vacuum created during the intake stroke.

If you want more engine braking turn on the AC. :)

Shawn
 
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Locoelectrician

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After driving gas sticks forever I love the lack of engine braking. That is a large part of why diesels get better fuel economy. While cruising a small throttle positions they aren't burning extra fuel to overcome the partial vacuum created during the intake stroke.

If you want more engine braking turn on the AC. :)

Shawn
Can you double check your post turbo number please? It doesn't work on mine. I found the version in C, that works, but yours in F does not. Thanks.
 

Locoelectrician

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After driving gas sticks forever I love the lack of engine braking. That is a large part of why diesels get better fuel economy. While cruising a small throttle positions they aren't burning extra fuel to overcome the partial vacuum created during the intake stroke.

If you want more engine braking turn on the AC. :)

Shawn
Not the right thread for this, but I think you're missing my point. My 13 diesel Passat had excellent engine braking, as does my diesel truck. This new car has none.

Back to the temp topic, the way my DPF temp acts is like there is some sort of bypass when decelerating. When going downhill, egt and pre cat both drop rather quickly, but DPF climbs. When you get back on the throttle, it's like a bypass valve or whatever closes and the DPF very quickly drops while EGT climbs. I'm no newbie to diesels, and this is quite bizarre. Would love to see a detailed diagram of the exhaust system of the 15 engine and sensor placement.
 

Locoelectrician

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2015 Passat TDI SEL, 2015 Golf SEL Sportwagen, 2005 Jetta TDI, John Deere 355D
Is the individual sensor refresh rate determined by the ECU? I ask because I have my scangauge set to "fast", and while egt and DPF update nearly instantly, the pre cat sensor is very slow, and updates in roughly 5 second intervals. If I'm not explaining well enough, egt and DPF will update about once every second or half second and the numbers climb or drop quite smoothly, while pre cat sits at a number for about 5 seconds and then jumps to the next. So instead of 520, 525, 528, bla bla bla, it will be more like 520,............. 580.

Not a huge deal, but wondered if one of the programmed digits sets sensor refresh rate. My guess is no, based on how close the numerology is for egt vs pre cat but thought it was worth asking.
 

VeeDubTDI

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The programmed digits do not set the refresh rate.
 

Jetta_Pilot

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2015 Passat Highline TDI Candy White (SEL Premium) long gone 2002 Jetta TDI
With all the knowledge here about the Scangauge II can anyone here tell me how I can completely reset the SC II to factory? I have a continuing false reading as to how much fuel is required at the next fill up. It had been out by as much as 1000 gallons.
I have had it disconnected from the OBD II port for as long as 4 weeks and the error still comes back.

Also my way of mounting it is very simple. I had a piece of metal bent twice sort of a squared off "U" shape. Part of it slides in between the left air outlet and the dash and the flat part on top is where the SC II is mounted with "Gorilla Tape".

I have a picture how it was on my Jetta and its the same on the Passat. Hope the picture will attach. It does not but the link will take you.

http://pics.tdiclub.com/showphoto.php?photo=38631&title=dscf0004r&cat=all
 
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VeeDubTDI

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Springfield, VA
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With all the knowledge here about the Scangauge II can anyone here tell me how I can completely reset the SC II to factory? I have a continuing false reading as to how much fuel is required at the next fill up. It had been out by as much as 1000 gallons.
I have had it disconnected from the OBD II port for as long as 4 weeks and the error still comes back.

Also my way of mounting it is very simple. I had a piece of metal bent twice sort of a squared off "U" shape. Part of it slides in between the left air outlet and the dash and the flat part on top is where the SC II is mounted with "Gorilla Tape".

I have a picture how it was on my Jetta and its the same on the Passat. Hope the picture will attach. It does not but the link will take you.

http://pics.tdiclub.com/showphoto.php?photo=38631&title=dscf0004r&cat=all
There is a setting to restore it to factory defaults, but I don't know where it is in the menu.

For what it's worth, I've found that the fuel economy portions of the ScanGauge are never very reliable and can vary significantly depending on driving style, even when it is properly calibrated with numerous fill-ups.
 

Shawn67

Active member
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Sep 19, 2015
Location
Ma
TDI
2015 Passat SE TDI
My 13 diesel Passat had excellent engine braking, as does my diesel truck. This new car has none.
How is the MPG of the new car vs old.

New engine has more electrically driven (not engine driven) accessories vs the old. That is the difference in engine braking. Less parasitic losses to the accessories which translates to less engine braking.

Shawn
 

Shawn67

Active member
Joined
Sep 19, 2015
Location
Ma
TDI
2015 Passat SE TDI
Is the individual sensor refresh rate determined by the ECU? I ask because I have my scangauge set to "fast", and while egt and DPF update nearly instantly, the pre cat sensor is very slow, and updates in roughly 5 second intervals. If I'm not explaining well enough, egt and DPF will update about once every second or half second and the numbers climb or drop quite smoothly, while pre cat sits at a number for about 5 seconds and then jumps to the next. So instead of 520, 525, 528, bla bla bla, it will be more like 520,............. 580.

Not a huge deal, but wondered if one of the programmed digits sets sensor refresh rate. My guess is no, based on how close the numerology is for egt vs pre cat but thought it was worth asking.
Yup, I see the same thing. It is likely just the sampling rate of the sensor/computer itself.

Shawn
 

Locoelectrician

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2015 Passat TDI SEL, 2015 Golf SEL Sportwagen, 2005 Jetta TDI, John Deere 355D
How is the MPG of the new car vs old.
New engine has more electrically driven (not engine driven) accessories vs the old. That is the difference in engine braking. Less parasitic losses to the accessories which translates to less engine braking.
Shawn
That may be part of it but I believe there is more to it than that and I suspect (after talking to Malone) that most of the difference is in the adjustable vanes of the turbo. They claim they can give the engine braking back with a tune.
 

VeeDubTDI

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That may be part of it but I believe there is more to it than that and I suspect (after talking to Malone) that most of the difference is in the adjustable vanes of the turbo. They claim they can give the engine braking back with a tune.
A tune can certainly add significantly more engine braking, if desired.
 

JELLOWSUBMARINE

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Can this be done with the X gauge instead of the Scangauge?
XGauge is a function of the ScanGauge - it's the way you add a non-standard gauge by entering the PID codes and correction values.
BTW Ive been trying to determine this for many pages so Im hoping for real good clearity..

Is the x gauge a "non std gauge reading", requiring coding on the SG II?
 

Diesl

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Not really writing code, just entering a few parameters. I think the manuals etc. are all online, on the scangauge website.
 

06bluebeetletdi

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Just installed a scangauge ii on my ‘13 beetle tdi, i have a polar fis on my 14 passat. The difference in regen temps (1500* on the beetle!) and coolant temps (190* beetle vs 215* passat) is quite fascinating. I wish the scangauge calculated soot level and miles since regen like the polar does, but they make a female car nerd quite happy :)
 

JELLOWSUBMARINE

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Just installed a scangauge ii on my ‘13 beetle tdi, i have a polar fis on my 14 passat. The difference in regen temps (1500* on the beetle!) and coolant temps (190* beetle vs 215* passat) is quite fascinating. I wish the scangauge calculated soot level and miles since regen like the polar does, but they make a female car nerd quite happy :)
Why not the polar FIS on the beetle? Does the Polar signal regen other than temps?
 

06bluebeetletdi

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The polar fis only works on large mfi like the passat, golf and jetta sportswagen. It doesn’t work on the small mfi of the jetta and beetle, i wish it did i would have bought another one because the info is shown 4 deep right in the mfi in place of the Bluetooth menu, which the beetle does not have.
 

Astrand1

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2013 Passat TDI SEL premium
We've gotten a couple questions about how we put EGT on our ScanGauge II, so I'll make a quick post.

I got this information from here: http://www.scangauge.com/support/xgauges-for-cansf-vehicles/

Here is the best information to monitor on your Passat...

EGT1 (pre-turbo): This is useful for monitoring warm-up mode and temps going into the turbo. This will change very rapidly as you change the accelerator position.
TXD: 07DF0178
RXF: 054106780000
RXD: 3810
MTH: 00090032FFD8
NAM: EGT

CAT B1S1: This is useful for monitoring regeneration activity. Anything over 900F is a regen.
TXD: 07DF013C
RXF: 0441053C0000
RXD: 2810
MTH: 00090032FFD8
NAM: DPF

Boost pressure: This is useful for monitoring boost pressure. You should see 0 PSI with the ignition on and the engine off. You should see a max of 23.0 PSI on a stock tune.
TXD: 07DF0170
RXF: 054186700000
RXD: 3810 (4810 for a model year 2015)
MTH: 00910BB8FF64 (for sea level - you'll need to adjust the last 4 digits if you live at altitude in order to get to 0 PSI with the ignition on and the engine off. Also note that the baseline will change with atmospheric pressure as you change altitude.)
NAM: BST


Water Temperature: This is useful for monitoring actual water temperature
This is a normal gauge - no XGAUGE required, just cycle through the presets.

Personal note: I watch both exhaust temp sensors listed above and wait for both to be below 450F before shutting off the engine.

For information on how to program an X-Gauge, read page 38 on the Owner's Manual here:

http://www.scangauge.com/wp-content/plugins/download-monitor/download.php?id=1


Thanks,

-Jason
For the boost pressure how You said that you have to adjust the last 4 digits for sea level. What numbers does one use for sea level or close to it?
 

Diesl

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Regarding boost pressure and altitude adjustment: AFAIK the TDI does this for you (adjust boost pressure for altitude, until it runs into the turbo rpm limit), so why would you want to take the altitude adjustment out again in your display? Power is related to the absolute manifold pressure, so that is what you should display. Preferably in bar, because that will give you directly the power multiplier. 1 bar absolute pressure = same power as naturally aspirated engine at sea level; 2 bar = double the power, 2.4 bar = limit (I think). All independent of what altitude you are at, or whether a low pressure system is moving through. Converting to psi and 'correcting' for your ambient pressure is putting effort into getting a less meaningful display.

Just my two cents.
 
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