Thread: Fuel consumption

well tell whoever wrote that up that he should have his ability to do math scaled back to simple bimdas type work

for starters as each car covers the same distance with the same gearing by his modling that the only thing influencing fuel consupmtion is total Revs done by the engine is wrong. as the distance would change and thats not one of the factors of the question.

Then he goes on to state that the difference in RPM and speed is not linier... urmmm yes it is unless youve got a really badly slipping clutch, a shot auto (once TC lockup has happened) or a constantly variable Belt drive (which I havent seen in a rover yet)

Take that load of gumpf and throw it away...

Well said Blknight.aus

AND

I have to agree with Blknight (except Bimdas should be Bomdas)

Perhaps you should have asked a mechanical engineer rather than a mathematician. Dr R.M seems to lack the required understanding of a mechanical drive line.

I do like the method he used in his solution though .

It's ok, he'll just alter the question to suit the answer

Dear Chris

Please find attached the way I see the problem - make sure you believe it yourself before putting it out there for discussion. My experience is that these sorts of answers only move the debate to the next question ...

All the best, thanks for asking me to be involved,
Rob

Oh, it comes with a disclaimer, how cute

Originally Posted by awabbit6

I have to agree with Blknight (except Bimdas should be Bomdas)

Perhaps you should have asked a mechanical engineer rather than a mathematician. Dr R.M seems to lack the required understanding of a mechanical drive line.

I do like the method he used in his solution though .

Brackets Indicies Multiplication Devision Additions and subtractions...


I dont like his model one bit its self contradicting within itself...

(edit with paraphrase to follow)

the only factor affecting the total amount of fuel used is the total number of revolutions made by the engine

Ok so we are only considering one variable, not distance, not speed, not the gearing nothing else but how many turns the engine does.

Say car A makes the journy in Ta and Car B makes the same journey in Tb

Ok so they are covering the same distance cool I get that. he then goes into some mathmatical logic and ends up with

This depends on the make of the vehicle

just before his graph

Urmmm hang on didnt we say earlier that

the only factor affecting the total amount of fuel used is the total number of revolutions made by the engine

which would mean that for our mathmatical model the make of the vehicle is irrelivent as the only factor is the number of revolutions the engine makes... We should be using the same theoretical model of car in the same theoretical model.

So theres the first biggie.

and heres my favorite bit.....

you take a drive over the same journey at 1759 RPM and again at 2000RPM

hey hey hey...... Wasnt that the question in the first place... I know It can be worked out by real life testing I wanted a mathmatical model of it.......