[idahofox]

For some time now, I have watched the paranoia build about the accuracy of the OEM gauges on our DMax's.

The " Cluster " has a set of analog gauges, that are digitally Controlled by a computer. The gauges displays what the computer commands and they do it very well.

Any one that expects a, 120° of arc on a two and one quarter inch gauge to yield laboratory quality information does not live in my Real World. These gauges were not designed to be used for diagnostics, they do provide information on, general state of operation.

The computer collects Data from various sensors to control the gauges. The " Fuel Level ", " Oil Pressure ", " Transmission Fluid Temperature " and " Engine Coolant Temperature " Data, is sensed from variable resistance bridges ( variable resistors ); the " Tachometer " and " Speedometer " sensors are Pulse Generators, the Data is/are, pulses/sec as counted by the computer. The " Battery " Data, is from fixed bridge sensor.

The gauge presentation ( value ) is intentionally Dampened. Without dampening, the gauge would be useless because it would appear to be vibrating ( moving ) all over the place.

Example: If the instantaneous Data from the fuel sensor was presented to the gauge, you could read ( see ), a quarter of a tank of fuel and three quarter of a tank of fuel displayed within seconds; the gauge would follow the fuel movement in the tank, useless.

The " Engine Coolant Temperature " gauge has received a great deal of attention and, IMO, is grossly misunderstood. The real world reality is that it works identically as the Fuel Gauge example above.

My observations are that Confidence in the ECT gauge has, over time, been damaged by misinformation, misunderstanding and broad statements made from ignorance.

The most misunderstood factor of ECT gauge operation is it’s dampening; this I believe promotes the Broad Statements previously noted.

The ECT dampening is mathematically derived by an algorithm using the Data collected from the sensor. The gauge displays the " Mean Value " of the Data collected. It is Not an instantaneous nor even an average value of coolant temperature.

This post is intentionally simplistic, we can get much more detailed.

My point is: Use the gauge for it’s intended purpose. The Gauge Does Not Lie.

If you push your equipment to a Failed OH Point, you have ignored Two warnings.

We can, improve performance ( do more work ), by modifying various equipment parameters; a personal choice.

This is my take. FWIW.

 

[DMAXITOL]

This is what I've found also. A 15* or so temporary lag is not the end of the world.

 

[Diesel Tech]

To take this one step further all the temperature gauge on the Duramax truck move in steps. Each size of the step is not the same but the movment is very simple. Take a look at the gauge and watch it's movement closely and you will alway see it move the same distance each time. It will step about one set of markers each time. On my personal truck the needle will sit right in the middle of to hash markers and stay there until it jumps to the middle of the next two hash marks. If one was to scale out the gauge it would leed ou to believe it's moving in 10*steps but it's not. Use the factory gauges as intended and not for any test purposes. If you want real before and after data log the ECM data buss as it will give sensor reading down to 1* on the coolant and tranmission temps but if you want EOT you need to add lab quality gauges.

 

[killerbee]

Nice post Fox.

I really don't know why the attention has mushroomed over ECT value and rumored effects of re-flash to disguise heat up trends.

As a certainty, I have seen that some of GM's ECT "tell tale" gauge reflash's have done one thing: changed the ECT temp at which the DIC warnings appear, an overt obvious attempt to reduce the visibility of the overheat issue with the least cost to corporate GM. I have not seen any attempts to make the gauge intentionally lie, beyond the normal time-averaged lag that is characteristic of a coolant temp gauge.

Ours is hardly atypical of other ECT gauges in the cooling system world, IMO. Lazy by design as you point out. Oil pressure, conversely, needs to be real time, and it is. Not atypical either.

I basically use it for one thing: warmup, knowing when it's time to put the hammer down.

 

[idahofox]

To take this one step further all the temperature gauge on the Duramax truck move in steps. Each size of the step is not the same but the movment is very simple. Take a look at the gauge and watch it's movement closely and you will alway see it move the same distance each time....

...It will step about one set of markers each time...

...On my personal truck the needle will sit right in the middle of to hash markers and stay there until it jumps to the middle of the next two hash marks. If one was to scale out the gauge it would leed ou to believe it's moving in 10*steps but it's not. Use the factory gauges as intended and not for any test purposes. If you want real before and after data log the ECM data buss as it will give sensor reading down to 1* on the coolant and tranmission temps but if you want EOT you need to add lab quality gauges.

This maybe what we ( I ) have interrupted as " TStat " cycleing.

Not bad, maybe not accurate.

Simply, larger/quicker than expected temperature change in time.

 

[bmoeller]

Dodge gauges work about the same way. Just a general guide.

 

[TheBac]

I would think if you were running tests on your truck, you'd have more accurate guages installed that read better than the stock ones anyway.

Just for comparison, look at the fuel guage. Its not accurate by a long shot.

 

[idahofox]

I would think if you were running tests on your truck, you'd have more accurate guages installed that read better than the stock ones anyway.

Just for comparison, look at the fuel guage. Its not accurate by a long shot.

I agree, were I testing a product in developement.

The end user, evaluating a purchase and reporting the changes observed, would see little benifit from new instrumentation. IMO.

" Did I improve my equipment performance " ?
" Did I add margin to my operational envelope " ?
" Can I run WOT without being at risk " ?

I personally choose more accurate gauges, that is why I have a predator.

:sly:

 

[Diesel Tech]

The testing needs to be done with other gauges as trying to say the factory gauge says it's better leaves to much room to know if there was a real improvement or just the gauge variations. Data logging is the only real way to see before and after with any degree of certainty.

 

[D Lafleur]

FWIW I dont agree when I currently have 4 GM vehicles in my driveway and only one of them has an ECT gauge that "parks the needle" over a temp range 35*.

I agree that averaging and smoothing are required, however when a gauge doesnt move from Tstat cycle to fan engagement. GIVE ME A BREAK!

FWIW this smells of stuff I have seen in other places.

 

[idahofox]

FWIW I dont agree when I currently have 4 GM vehicles in my driveway and only one of them has an ECT gauge that "parks the needle" over a temp range 35*.

I agree that averaging and smoothing are required, however when a gauge doesnt move from Tstat cycle to fan engagement. GIVE ME A BREAK!

FWIW this smells of stuff I have seen in other places.

Is that " I don't agree ", that they do not work this way or that you do not like the way they work ?

Yes this information can be found " in other places ", didn't know its smelled though. :shrug:

 

[D Lafleur]

Is that " I don't agree ", that they do not work this way or that you do not like the way they work ?

Yes this information can be found " in other places ", didn't know its smelled though. :shrug:

I agree the Dmax equipped trucks works this way. I dont agree that every automotive factory gauge works this way. FWIW Every other vehicle I have owned hasnt worked this way.


OK You ask so here you have it. BS

That is the smell. Like you I frequent several of these forums and this thread is ripe.

FWIW I have enjoyed the effective conversation in other threads here.

 

[Diesel Tech]

FWIW I dont agree when I currently have 4 GM vehicles in my driveway and only one of them has an ECT gauge that "parks the needle" over a temp range 35*.

I agree that averaging and smoothing are required, however when a gauge doesnt move from Tstat cycle to fan engagement. GIVE ME A BREAK!

This is just what I was saying in my earlier post. The gauge moves in steps and until you reach the next step it will not move then it will move all at one time to the next step. It's an indicator of the temperature but not the real number.

 

[killerbee]

Steve, have you been able to find evidence of stepwise ECM programing, something that would point to intentional factory programming, that makes for stepwise movement?

 

[RacinJason73]

This is just what I was saying in my earlier post. The gauge moves in steps and until you reach the next step it will not move then it will move all at one time to the next step. It's an indicator of the temperature but not the real number.

O.K. Right! But ALL the steps should be exactly the same increment! GM's ECT gauge for our trucks is not consistant with an equal increment step approach. The "210*" mark is a HUGE step with respect to all the other steps. You're right, it's an indicator, not a data acquistion piece. But this "large step" characteristic makes it lousey even as an indicator alone and that's why people feel it's unreliable. So the gauge reads 210* ... does that really mean I'm at 195* or 220*? That's a pretty big temperature range (or "step" or whatever).

 

[Diesel Tech]

Agreed, the steps suck! I do not know why they did it the way they did but that's what we got to live with. Look at a fuel gauge............. stays full for a long time then drops slowly to 1/2 tank then once below 1/2 tank hauls *** to empty. Take and get a fill up at 1/2 tank on the gauge and it takes more than 1/2 the capacity for the tank but fill it at 3/4 and it takes less than the proper capacity.

 

[RacinJason73]

Agreed, the steps suck! I do not know why they did it the way they did but that's what we got to live with. Look at a fuel gauge............. stays full for a long time then drops slowly to 1/2 tank then once below 1/2 tank hauls *** to empty. Take and get a fill up at 1/2 tank on the gauge and it takes more than 1/2 the capacity for the tank but fill it at 3/4 and it takes less than the proper capacity.

In your example, the fuel gauge inaccuracy phenomena could be due to using a linear gauge in a conical tank. However, the inaccuracy of the gauge is likely GM's known attempt of calibration to dupe us into thinking we're getting GREAT fuel milage ("it stays on FULL FOREVER") for those that don't drive until the tank is empty. They've been using this tactic for years and not just on their trucks. We used to joke around that as soon as a GM fuel gauge starts to come off full, you better start lookin' for a station and 1/2 full is nearly on WALK. My thought is, if GM is going to "dumb down" our gauges so much that the value being displayed is inaccurate to the point of not trusting it, why not just save a BUNCH of $$$ and reinstitute the idiot lights of the 80s and omit the gauge?

The fuel gauge, IMO, is much more of an "indicator" than our ECT gauge should ever be - there are temp. increments/marks every 5*. An incremented ECT gauge should display the coolant temp. +/-3* of the actual temp. If it's not capable of doing so, why have a gauge with increments? GM could've just used a range type gauge with COLD on one end and HOT on the other and have it be just as useful at this point. But GM chose an incremented gauge, so wouldn't you think that should mean it's more accurate or at least what is displayed as being more meaningful?

 

[idahofox]

Here we go again, paranoia, misunderstanding, misinformation.

THE FUEL GAUGE IS ACCURATE ! ! ! ! !

The fuel sensor is not calibrated, geometrically, to provide the correct data to the computer.

Should we, as owner/operators, Need to calibrated the sensor, in order to have usable information, NO !

If you require an accurate fuel gauge, You will have to calibrate the sensor.

GM doesn’t do it, Ford, Dodge, International, Kenworth, Peterbuilt, Nissan.......... infinity.

Yes, I can do it.

FWIW.

 

[SCCOtech]

Wow exciteable!

Here we go again, paranoia, misunderstanding, misinformation.

THE FUEL GAUGE IS ACCURATE ! ! ! ! !

The fuel sensor is not calibrated, geometrically, to provide the correct data to the computer.

Should we, as owner/operators, Need to calibrated the sensor, in order to have usable information, NO !

If you require an accurate fuel gauge, You will have to calibrate the sensor.

GM doesn’t do it, Ford, Dodge, International, Kenworth, Peterbuilt, Nissan.......... infinity.

Yes, I can do it.

FWIW.

opcorn:

Wow you are awefully exciteable guy, chill out eh? This temp gauge thing isn't a mystery. Easy to run it down and see what the score is with it! :Thumbup:

So which of you have actually checked to see what each degree of the motor represents on the temp gauge?

 

[idahofox]

opcorn:

Wow you are awefully exciteable guy, chill out eh? This temp gauge thing isn't a mystery. Easy to run it down and see what the score is with it! :Thumbup:

So which of you have actually checked to see what each degree of the motor represents on the temp gauge?

You quote information on the " Fuel Gauge ", then address my physique, then address Your core issue.

If it is OK with you, let's at least get on the Same Page @ the Same Time.