Skip to main content ↑ ↓
Topic: Correlation of engine performance parameters  (Read 484 times) previous topic - next topic

Correlation of engine performance parameters

I have my VMSpc up and running, displaying engine load, intake manifold temp, turbo boost, and RIM.  I am trying to understand the relationships between these parameters, how they affect each other, as well as their importance to engine safety. Can someone please explain these? What other parameters should be monitored? Thanks, Royce.
Royce & Denise, MC #17410
'01 U320 4220 ISM450 Build #5895 SOLD
Toad: '10 Honda CR-V

Travel makes one modest. You see what a tiny place you occupy in the world. - Gustave Flaubert

Re: Correlation of engine performance parameters

Reply #1 –
Royce,

Engine load is mostly a function of your right foot.  And, as you would expect it is closely related to boost pressure (more throttle, higher boost pressure).

Intake manifold temperature is a function of both ambient temperature and efficiency of the CAC (Charge Air Cooler), also called Inter-cooler and After-cooler-- all the same beast.  Ideally, intake manifold temperature should be within a few degrees of ambient temperature.

I find instantaneous MPG another interesting parameter.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Correlation of engine performance parameters

Reply #2 –
Royce, you can monitor what ever you think is important.  It watch transmission temp, retarder temp, oil temp, coolant temp, manifold temp, oil pressure and battery volts with big red/yellow/green indicators.  A glance tells me things are OK. Gear, tach, turbo pressure all make a difference in economy and cooling. Immediate MPG gives you an idea of what is going on right now. Recent MPG is a rolling average over time.  It changes much more slowly.  Everyone drives differently.  I usually drive about 5 mph under the limit but not over 65 and not under 55.  The biggest impacts on economy is wind, hills and then speed.  A moderate drive gets you there soon enough with much less stress.

The gearheads can probably add to this. 

Art from VMSpc told me engine HP is calculated, not sure where load and torque comes from.

Roger
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Correlation of engine performance parameters

Reply #3 –
Quote from: Roger and Susan in Home2 –
Art from VMSpc told me engine HP is calculated, not sure where load and torque comes from.

Engine horsepower--even on a dynamometer--is a calculated value. Torque and RPM are measured, and then horsepower is calculated.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Correlation of engine performance parameters

Reply #4 –
I find my intake temp will go up as I increase load on the engine. If i am climbing a big hill it will go up about 10 degrees and matches the increase in temps for the coolant  as well.  I just had my intake sensor changed out as it was jumping around up and down 20 degrees in seconds. 
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon
 

Re: Correlation of engine performance parameters

Reply #5 –
I monitor every engine parameter. I just don't know how they all relate to each other.
Royce & Denise, MC #17410
'01 U320 4220 ISM450 Build #5895 SOLD
Toad: '10 Honda CR-V

Travel makes one modest. You see what a tiny place you occupy in the world. - Gustave Flaubert