Discrepancy in fuel temp between TDI timing and measuring block group 007

[dieseljunkie]

Anyone notice the discrepancy between the fuel temp as reported in the lower left hand corner of the TDI timing graph and group 007?

In the graph, it says 130 with no units of measure so I assume that's in F. In group 007, it syas 40 C (104 F). That's a 26 degree difference! Which one is correct? Or do I have a problem with my car?

 

[wolfsburg_de]

The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps. In other words, it's not to be compared to what you see in group 007 which has units and a conversion factor from the raw data into a meaningful temp. FYI, nothing is in Fahrenheit, only Celsius.

 

[Curtis328]

^^^ True story...

 

[dieseljunkie]

The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps. In other words, it's not to be compared to what you see in group 007 which has units and a conversion factor from the raw data into a meaningful temp. FYI, nothing is in Fahrenheit, only Celsius.

Thanks wolfsburg_de! I am curious why a unitless fuel temp value is displayed in the TDI timing graph. I'd guess it's there for a reason otherwise it would just confuse people (like me)?

 

[wolfsburg_de]

Group 000 is unitless, that's just how VW designed it. The TDI Timing Checker is our handy function to make it less confusing by plotting the data on a graph and giving you a result:

 

[Curtis328]

On a somewhat related subject, is it normal for the point of intersection of the fuel temp and timing advance lines to jump up and down constantly by about 3 or 4 units?

 

[roy1]

The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps. In other words, it's not to be compared to what you see in group 007 which has units and a conversion factor from the raw data into a meaningful temp. FYI, nothing is in Fahrenheit, only Celsius.

Its not meaningless, This is the min- max value representable by an eight-digit binary number.

 

[wolfsburg_de]

Its not meaningless, This is the min- max value representable by an eight-digit binary number.

Right, like I said "The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps. "

 

[wolfsburg_de]

On a somewhat related subject, is it normal for the point of intersection of the fuel temp and timing advance lines to jump up and down constantly by about 3 or 4 units?

A little jumping around is normal, hence the "cloud" feature:

http://www.ross-tech.com/vag-scope/TDIGraph.html

 

[roy1]

Right, like I said "The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps. "

And you missed the point

 

[wolfsburg_de]

And you missed the point

What is your point? From a user perspective, knowing that a temperature is, say, 110 on a scale of 0-255 does not have any meaning unless the user knows what the min and max are. Please re-read everything I wrote in this thread to hopefully understand it better.

 

[dieseljunkie]

So the x axis is a unitless fuel temp and the y axis is timing. Is timing also unitless?

Why fuel temp for the x axis? Why not coolant temp instead? Does the ECU change the timing based on fuel temp only? If so, what is the formula?

 

[roy1]

What is your point? From a user perspective, knowing that a temperature is, say, 110 on a scale of 0-255 does not have any meaning unless the user knows what the min and max are. Please re-read everything I wrote in this thread to hopefully understand it better.

You should probably talk to your techies as you are evidently just a sales man. Nothing wrong with that but please stay in your lane.

 

[wolfsburg_de]

So the x axis is a unitless fuel temp and the y axis is timing. Is timing also unitless?

Why fuel temp for the x axis? Why not coolant temp instead? Does the ECU change the timing based on fuel temp only? If so, what is the formula?

Yes, everything in group 000 is unitless. Start of injection changes based on temperature of the fuel since diesels operate by compressing the A/F mixture to the point where it combusts. If you start with hotter fuel, it takes less pressure to get to the point where combustion occurs. Coolant temp only matters in that you need to ensure that the engine is up to temp before you'll get valid readings.

Why is fuel temp on the x-axis? Because that is the way all of the VW factory repair documents show it. Check in a repair manual under, for instance:

Volkswagen > New Beetle, New Beetle Convertible > 1998-2008
1.9 Liter 4-Cyl. 2V TDI Fuel Injection Glow Plug, Engine Code: ALH
23 - Diagnosis and Testing.Injection Start, Checking Dynamically and Adjusting

Ross-Tech did not design the engine or define what's in each group. We simply make software that passes that information along to users through a PC, and the handy TDI Timing Checker makes it easy to check so you don't need to make a note of the unitless fuel temp and start of injection, then go over to the chart in your repair manual to see where the two values meet up on the chart.

 

[wolfsburg_de]

You should probably talk to your techies as you are evidently just a sales man. Nothing wrong with that but please stay in your lane.

Actually I am the head of the tech support department and have a degree in Mechanical Engineering (not that one is needed to understand the pretty simple concepts I posted, IMHO). What may I ask are your credentials and what exactly did I write that you believe to be incorrect? As a side note, how exactly have you helped in this thread to answer the OP's questions?

 

[roy1]

Actually I am the head of the tech support department and have a degree in Mechanical Engineering (not that one is needed to understand the pretty simple concepts I posted, IMHO). What may I ask are your credentials and what exactly did I write that you believe to be incorrect? As a side note, how exactly have you helped in this thread to answer the OP's questions?

I have a PHD in Computer Science( not that is need to see that a correlation can be had between the two) . I need not to explain more.

 

[wolfsburg_de]

I have a PHD in Computer Science( not that is need to see that a correlation can be had between the two) . I need not to explain more.

I don't understand what you mean by "not that is need to see that a correlation can be had between the two".

 

[wolfsburg_de]

In re-reading this thread, I think there may be a language barrier. I wrote that "The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps." It looks like "roy1" must have thought that "unitless" has the same meaning in English as "meaningless". He correctly pointed out that the range of 0-255 (a total of 256) is obtained by an "an eight-digit binary number". This is true, 2^8 = 256.

I'm going to assume that's what "roy1" meant and will now thank him for his contribution to this thread.

 

[roy1]

Oh Shiat !! My friend just screwed me on this . My apologies to you . She was having fun on my other computer. She is all that she says she is. No hard feelings ok.
Once again my apologies.

 

[roy1]

In re-reading this thread, I think there may be a language barrier. I wrote that "The values in group 000 are truly unitless and have a range from 0-255 representing the entire scale of possible temps." It looks like "roy1" must have thought that "unitless" has the same meaning in English as "meaningless". He correctly pointed out that the range of 0-255 (a total of 256) is obtained by an "an eight-digit binary number". This is true, 2^8 = 256.

I'm going to assume that's what "roy1" meant and will now thank him for his contribution to this thread.

Please thank my friend , she can be very, how would you say it in english very persistant/agressive. I am just a Doctor.

 

[dieseljunkie]

Oh Shiat !! My friend just screwed me on this . My apologies to you . She was having fun on my other computer. She is all that she says she is. No hard feelings ok.
Once again my apologies.

How did your friend (from her computer) make "unitless" to become "meaningless" on your computer? That is quite a feat!