Skip to main content ↑ ↓
Topic: VMSPC Engine Correction - Cat 3126? (Read 451 times) previous topic - next topic

VMSPC Engine Correction - Cat 3126?

Are there any Cat 3126 owners that use an engine correction factor to re-calibrate your VMSPC MPG & remaining fuel numbers? 

I am using a factor of .8 and still consistently see under reported MPG and remaining fuel.  At my last fillup, the VMSPC said I should need 75 gallons and it only took 55, which has been pretty typical.  I'm lucky to get 6 MPG on the VMSPC but I'm actually getting closer to 8 MPG.  And these would have been bigger differences if generator usage was accounted for.  Speed & miles traveled seem to be pretty accurate.  SilverLeaf says the engine is probably under reporting fuel usage & to keep reducing the factor #, but how far off can it be?  I'm curious what correction factors are working for you, or if there's something else to adjust.  Thanks.

Re: VMSPC Engine Correction - Cat 3126?

Reply #1 –
I know of no correction factors.  I am amazed at how accurate mine is.  Every time I fill up its pretty much dead on.  That pretty paint job is throwing you off.

John
John and Stacey Smith
Motorcade NO: 11973
1997 U295 CSGI 40'..Build No. 5036     
920 Watts on the roof..CAT Power w/fuel Inj. Programmer
2021 GMC Sierra AT4 1500
EX..2015 Jeep Wrangler Sahara
Ex 1990 U280 RSAI 36'..Build No. 3638

Re: VMSPC Engine Correction - Cat 3126?

Reply #2 –
Quote from: bdale –
Are there any Cat 3126 owners that use an engine correction factor to re-calibrate your VMSPC MPG & remaining fuel numbers? 

I am using a factor of .8 and still consistently see under reported MPG and remaining fuel.  At my last fillup, the VMSPC said I should need 75 gallons and it only took 55, which has been pretty typical.  I'm lucky to get 6 MPG on the VMSPC but I'm actually getting closer to 8 MPG.  And these would have been bigger differences if generator usage was accounted for.  Speed & miles traveled seem to be pretty accurate.  SilverLeaf says the engine is probably under reporting fuel usage & to keep reducing the factor #, but how far off can it be?  I'm curious what correction factors are working for you, or if there's something else to adjust.  Thanks.

Make sure you are using the correct engine file.  VSMpc only displays the data that is available to it and what is reported.  Make sure your tank size is set correctly.

Where are you using a factor of 0.8?  If you think the fuel use that is reported is less than you think it should be then a correction should be greater than 1.    There are no specific corrections on the Tank Minder Gauge. 

Check your total fuel value next time you fill up and then again when you add a known amount. Does the change in total used correspond to the fuel,you added? (Assuming no generator or other use)
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: VMSPC Engine Correction - Cat 3126?

Reply #3 –
John....I was hoping for a mileage improvement but unfortunately the paint didn't seem to matter.  ;) The VMSPC had the same issue before and after painting.  There is a correction factor under the Advanced menu that is supposed to fix the issue but it hasn't seemed to help.  It's interesting that it's working better with your Cat.  What engine file are you using?


Roger...

I think I am using the correct engine file.  In fact, SilverLeaf sent me a new file because their standard file didn't include enough data for the low end of the engine curves.  My horsepower & torque numbers stopped calculating below 1400 rpm.  They now work down to 850 rpm with the new file.  They were very familiar with my engine because apparently someone there has or had the same engine.  I've had the same mileage issues with both versions of the file.

Tanks size is set to 150 but I think it could be set at 1500 and still show the same problem.  It's an issue with how it's counting down from full, not an issue with the volume of the tank.

I don't have access to the software today but if I recall correctly, the .8 factor is entered into the Engine correction options under the Advanced tab, about 2/3 down in that dialog box.  There are 3 numbers there and the 1st one is the correction factor.  Silverleaf instructed me to change that value down from 1 until the results are accurate.  My fuel usage is being reported as more than actual, not less, so .8 should tend to correct the problem.  And generator time would tend to mask the problem.  According to Silverleaf, once that factor is changed it will affect all new or reset gauges, not existing ones.  So, I change the factor, create a new tank or trip gauge and monitor the results over several tanks by comparing against my own calcs of actual MPG.  So far I'm not seeing better results at .8 so I'll go to .5 and try that.  It just doesn't seem like it should be necessary though, especially after confirmation by John that he's not having the same issue.


Thanks for both of your replies.

Re: VMSPC Engine Correction - Cat 3126?

Reply #4 –
Bob,
    Have moved my coach storage closer to you...lol...North of Spring Cypress on Huffsmith Kohrville (Safe Harbor). Finally put her in a fully enclosed 14 x 80 with plenty of room to work on her.  If you want to come by and see how mine is set-up you are more than welcome as always. 
John
John and Stacey Smith
Motorcade NO: 11973
1997 U295 CSGI 40'..Build No. 5036     
920 Watts on the roof..CAT Power w/fuel Inj. Programmer
2021 GMC Sierra AT4 1500
EX..2015 Jeep Wrangler Sahara
Ex 1990 U280 RSAI 36'..Build No. 3638

Re: VMSPC Engine Correction - Cat 3126?

Reply #5 –
I sent a note to Silverleaf about this.  I wll see what they say.  Usually corrections are a percent or two (0.98 or 1.02). 20% or more would lead me to wonder it your fuel use sender is malfunctioning. 

My tank minder and what I actually put in are pretty close as well.  Rarely more than a gallon or two different taking into consideration other uses.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN
 

Re: VMSPC Engine Correction - Cat 3126?

Reply #6 –
My engine file was the Cat 3126 (300 Hp).ENG file that was supplied with the software.  Then Silverleaf edited it for me to extend to lower RMPs, but it's still based on the Cat 300hp file.  Both versions had the same results. 

John, if your tach & horsepower meters aren't freezing up below 1400 rpm, maybe you do have a different file?  Maybe you could check that the next time it's convenient?  It will be under the Advanced:Engine Type menu.  14x80?  We could both almost fit in there!

Roger, thanks for any feedback you get from Silverleaf.  I'm thinking I'll call them back before my next trip to make sure I understand correctly but I might setup 3 or 4 different gauges, each with a different correction factor, and let them all run at the same time.  That will help me zero in on the right adjustment faster, if they will actually work that way.