Scan Gauge II XGauge - EGT & Boost

VeeDubTDI

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Interesting. So I guess the takeaway from all of this is that each individual should program his/her ScanGauge MTH (math) in order to get it to 0.0 with the engine off.

This will, of course, change as you change altitude, but that's a given.
 
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BPofMD

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2012 Passat SE
1.1 is close enough for me..... it changes at will anyway..... I'll take the 1.1 safety factor.
 

tcp_ip_dude

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Interesting. So I guess the takeaway from all of this is that each individual should program his/her ScanGauge MTH (math) in order to get it to 0.0 with the engine off.

This will, of course, change as you change altitude, but that's a given.
And/or,

as the barometric pressures changes with passing weather fronts
.. If the SG's indicated boost PSI being off in the single digits bothers you guys, let alone tenths of a PSI, then you guys are going to be re-zeroing it almost hourly during even the mildest of frontal boundary passages.

My point is that you guys are chasing an almost constantly moving target (except when a High or low pressure parks itself over your location).

Been a long time since I took my flight exam, but as I recall, a barometric pressure change of 1" of mercury (common US unit of measure) = ~0.5 PSI, check your local weather almanac to see the hi/lo baro range in your area over the last 24hrs, week, month, year, etc, convert the units to PSI and you will get a notion of how volatile your indicated boost PSI variance can be even if your car is parked and stationary. (www.wunderground.com is a good source historical baro data).


I really haven't studied the X-Gauge coding syntax closely, but I'm sure you can control the numerical precision with a bit mask of some sort (i.e. remove the precision to the right of the decimal. Tenths of PSI ) so you only report PSI to single digit precision, that would make the PSI wander, due to altitude and baro changes, much less apparent.

Another example of why I think boost is really best represented by an analog visual indicator vs numerical.
 
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Diesl

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And/or,

as the barometric pressures changes with passing weather fronts
..
[...]
Another example of why boost is really best represented by an analog visual indicator vs numerical.
And another reason why I like bar as unit. I just display the total manifold pressure, as delivered by OBD. It takes minimal or no 'mental gymnastics' to subtract atmospheric pressure on the fly, in your head (1.0 bar is close enough for all practical purposes). In bar the display ranges from roughly 1.0 to 2.6 (2.64 is the highest I have seen), corresponding to the range going from no boost to 1.6 atmospheres boost. On a gas engine you would never have to deal with negative numbers, perfect vacuum is 0.0 bar - something that of course doesn't concern us with the superior Diesel engine.:D

The best is, the number displayed -manifold pressure in bar- is exactly the engine volume multiplication factor that you want (or should want) to know. It tells you by what factor the turbo multiplies your power.

Ok, end of my little advertisement for bar. :)
 

Nebelwerfer

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Canuckistan
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2012 Passat TDI
Well, was going into town on the highway and noticed the EGTs climbing a bit rapidly to 657C with a corresponding engine temp climb.

Caught it doing a regen with the SGII and I was going to be at my destination in about 10 minutes.

Took the next off ramp and let it complete it on it's own.

This is a must have item IMHO.

Regards
 

Diesl

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'78 Golf Diesel (long gone); 2012 Jetta Sportwagen TDI w/ DSG
This is a must have item IMHO.
Absolutely. For OCD people like us. The rest of the world drives along happily without ever even knowing about all those things they could be worrying about.

Perfectly on topic: My TDI just had a regen after only 300 miles. Usually it is 400-500 miles between regens. It happened just after a fuel up, after the diesel price fell below regular. Should I worry?
Edit: uhh-oh. 'Veteran member'. It's bad if a forum tells you you are getting old.
 
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MaddogTDI

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-manifold pressure in bar- is exactly the engine volume multiplication factor that you want (or should want) to know. It tells you by what factor the turbo multiplies your power.
This is great! I had never put it into that context before, but by using Bar as your unit of measure it becomes intuitive! ...moment of enlightenment. ... Chorus of angles... Thanks!

.
 

Knarrly Viking

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I really haven't studied the X-Gauge coding syntax closely, but I'm sure you can control the numerical precision with a bit mask of some sort (i.e. remove the precision to the right of the decimal. Tenths of PSI ) so you only report PSI to single digit precision, that would make the PSI wander, due to altitude and baro changes, much less apparent.
Can anyone modify the code to make the decimal go away?
 

VeeDubTDI

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And/or,

as the barometric pressures changes with passing weather fronts
.. If the SG's indicated boost PSI being off in the single digits bothers you guys, let alone tenths of a PSI, then you guys are going to be re-zeroing it almost hourly during even the mildest of frontal boundary passages.

My point is that you guys are chasing an almost constantly moving target (except when a High or low pressure parks itself over your location).

Been a long time since I took my flight exam, but as I recall, a barometric pressure change of 1" of mercury (common US unit of measure) = ~0.5 PSI, check your local weather almanac to see the hi/lo baro range in your area over the last 24hrs, week, month, year, etc, convert the units to PSI and you will get a notion of how volatile your indicated boost PSI variance can be even if your car is parked and stationary. (www.wunderground.com is a good source historical baro data).


I really haven't studied the X-Gauge coding syntax closely, but I'm sure you can control the numerical precision with a bit mask of some sort (i.e. remove the precision to the right of the decimal. Tenths of PSI ) so you only report PSI to single digit precision, that would make the PSI wander, due to altitude and baro changes, much less apparent.

Another example of why I think boost is really best represented by an analog visual indicator vs numerical.
Easy does it. I'm certainly not suggesting that you change your SCII every time you start the car. :rolleyes:

Set it to display 0.0 at your average home barometric pressure and have a happy day. It will go up and down based on weather conditions, but at least you're starting at the center point and moving up/down from there. This data can easily be found on Google.

Or set it for whatever makes you happy and move on. ;)
 

tcp_ip_dude

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2010 Jetta TDI Sedan
Easy does it. I'm certainly not suggesting that you change your SCII every time you start the car. :rolleyes:

[...snip] ;)

I'm just razzing you guys out of jealously. :D


To the best of my knowledge I can't get boost on my 2010 sedan, at least not the with SG v3.1x firmware.. I have EGT working.. If I'm wrong about this, someone please let me know; I'd love to get boost working..
 
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JdC Machine

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'13 Passat TDI SEL
Got mine all hooked up. Reading water temp (upper left), engine load (upper right), boost (named "PSI" in lower left) and EGT (lower right).

I used the manifold sensor (B1S1, IIRC) and am seeing 280-300degs. at idle. For boost, I used the coding per vw_norm and tried VeeDub's MTH coding and found it to be reading a negative (don't recall the exact number). Anyhow, I played with the math coding and ended up with MTH = 00910BB8FF64 to get a 0psi reading with the engine off where I'm at here in Orange County, CA.
 

VeeDubTDI

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I just checked the ScanGauge and the MTH is set to FF64! I'm a scatter brain sometimes. :eek:

I'll edit my other post.
 

VeeDubTDI

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While I was at it, I changed EGT to the pre-turbo sensor. It changes temperature much more quickly.

Edit: I added the cat (?) temperature (3C) back in because it gives me a good idea when the exhaust components cool down, which the pre-turbo sensor alone doesn't do.
 

JdC Machine

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I also changed the update rate from "normal" to "fast."

I assume the "load" units is %. Seems strange to me that at idle, it shows 40-50%. :confused:
 

JdC Machine

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'13 Passat TDI SEL
Which coolant/water temperature gauge do we believe? The factory gauge was showing 190 when the ScanGauge was showing between 130-140.

 
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VeeDubTDI

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Which coolant/water temperature gauge do we believe? The factory gauge was showing 190 when the ScanGauge was showing between 130-140.

The factory gauge has been a dummy gauge with a massive buffer for over 15 years. It will display "190" from actual temps of 165 to 225. It's a way of keeping hypochondriacs out of the service department. My Ford F-350 is the same way.
 

VeeDubTDI

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I also changed the update rate from "normal" to "fast."

I assume the "load" units is %. Seems strange to me that at idle, it shows 40-50%. :confused:
Load is a calculation of power generation within the available map. It probably is producing 40% of its available power (torque) at 800 RPM.
 

NickBeek

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The factory gauge has been a dummy gauge with a massive buffer for over 15 years. It will display "190" from actual temps of 165 to 225. It's a way of keeping hypochondriacs out of the service department. My Ford F-350 is the same way.
Yup, both my previous ford trucks the oil pressure coolant temp and trans temp gauges were glorified idiot lights. The same is true of the oil pressure gauge on my '06 Dodge truck. Now the coolant temp on the Dodge is an actual gauge.
 

Diesl

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Load is a calculation of power generation within the available map. It probably is producing 40% of its available power (torque) at 800 RPM.
The car (or at least my car) provides torque. It's in percent of maximum torque, and on a really odd scale (-125 to +125 percent; why would we need negative torque?? Or is this for Priusses going downhill, charging the battery?), but it works. I'll post the link and code after I look it up.
Looked it up: Link to my list in the OBD forum:http://forums.tdiclub.com/showpost.php?p=4123931&postcount=33
The code for torque:
Code:
TXD is 07DF01+PID
name PID RXF     RXD  MTH          units   comment
 TRQ  62 04410562 2808 00010001FF83 %       percent of actual torque
The car also gives out 'reference torque', so if there was a way to multiply torque, reference torque, rpm (and divide by 60 and multiply by 2 * pi) one could have real horse power.
 
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Diesl

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Load is a calculation of power generation within the available map. It probably is producing 40% of its available power (torque) at 800 RPM.
On my car, load % is usually way higher than torque %, except when coasting (both near zero), and at full throttle (both at 99). When idling torque is at a few percent (say, 4-7), whereas load can be several ten percent. Similar at moderate acceleration: torque between 10 and 20%, load two to three times that.

My guess is that the scangauge calculations of load and horse power are not so good for our diesels, and probably more tailored towards gasoline engines.

I asked linear logic about the horse power discrepancy, and they told me that they can't tell me their formula (which I hadn't asked for), and that it depends on the mpg reading, which can be adjusted. I tried that (up to +99%), and it didn't help. At low power it was too much of a correction, and at high power still not enough.
 

BPofMD

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Page 15 of the manual --- MORE-SETUP - UPPER left OR right buttons & goto ADV SETTINGS - lower right button to EDIT. Go to UPDATE RATE and select FAST.
 

VWJayhawk

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In the setup, IIRC. I'll find it and let you know for certain.
Page 15 of the manual --- MORE-SETUP - UPPER left OR right buttons & goto ADV SETTINGS - lower right button to EDIT. Go to UPDATE RATE and select FAST.
Awesome! Thank you both...out of town this weekend and didn't have it handy. Didn't see it with a quick glance of the PDF manual. Thanks again
 

Blue_Hen_TDI

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I just did some experimenting and realized that at our altitude here in Northern VA, FF6F resulted in 1.1 PSI with the engine off (turn ignition on and press any button on the SCII to wake it up).

I adjusted it to FF54 and now it displays 0.0 PSI with the engine off (and at idle, unless it's doing fast idle or a regen).
Dialing from FF6F to FF54 took me down from +1.1 to -1.6 PSI at idle. After experimenting, I found that FF64 was the magic number to get me to 0.0.
 

VeeDubTDI

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Dialing from FF6F to FF54 took me down from +1.1 to -1.6 PSI at idle. After experimenting, I found that FF64 was the magic number to get me to 0.0.
Yeah I made an error in that post. FF64 is what mine is actually set at - not the FF54 that I had posted previously.
 

Diesl

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'78 Golf Diesel (long gone); 2012 Jetta Sportwagen TDI w/ DSG
Dialing from FF6F to FF54 took me down from +1.1 to -1.6 PSI at idle. After experimenting, I found that FF64 was the magic number to get me to 0.0.
Are you adjusting for zero with engine off, or for zero at idle? I'm getting the impression (from the wisdoms of the interwebs) that by design our TDIs actually might make a little bit of boost at idle, to keep that little fan spinning and reduce turbo lag.
 

VeeDubTDI

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I've found that it makes very little boost (zero) at idle unless it is under a significant load (warm-up with the heat on) or during a regeneration.
 
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