MPH vs MPG

[Ceri]

Hi All
 
This may have been asked before but I could not find it.  If you need to get from A to B on the motorway is there an optimum speed in relation to fuel use.  So, in my 99 standard RS should I cruise a 60, 70 or 80+ mph?  I know this should be a no brainer and that the slower you go the less fuel you use but is that the case when cruising in a rotory?
 
Ceri

[gsb876]

I think its about 65mph in the rotary :cheers

[m1tch]

Why are you worrying about MPG? At any speed it will use quite a bit of fuel lol

[dthebuk]

Why are you worrying about MPG? At any speed it will use quite a bit of fuel lol

if you save money on going from A to B, when you get to B you can have more fun?


I guess it would be down to your Turbo, ports and map tbh really. Ideally you want to be sitting at max torque as long as this isn\'t too high in the rev range as air resistance becomes more of a problem the faster you go!

[Ricco_04]

I think you should cruise at 100mph!  If you did the same journey at 50mph then you would be running for 2x longer :Giggle

Loss is mostly when accelerating, so once you reach crusing speed you wont be in +ve pressure.

I have done santapod and back at 60 and 70 and didnt really find any difference tbh, It just took longer going slower!

Of course you are going to reach a point when air resistance plays so much of a factor - I think 70 is the sweet spot personally

[probedb]

Having recently done a lot of motorway driving, I get better MPG at 60-70 than 80ish. Then again I think my map is rather rich.

[shaunwil]

Depends on who tuned the car too. I have a sweet spot between 65-75 cruising. Get around 15 on my wideband around this speed cruising.

Shaun

[Grant Monkhouse]

As you said your engine is standard I would find the point at which your engine is not boosting off ofthe turbos, note the mph and stay at that.

If the the turbos are in sequential set up still then search for what rpm the first turbo kicks in and stay below that point.

No boost means no extra fuel.

[CharlieP]

There are many factors, rolling resistance, wind resistance, fuel usage, journey time...etc

The point where they would converge on a graph was 56mph....I think even with technological advances, this remains, but cars might be more efficient

[shaunwil]

As you said your engine is standard I would find the point at which your engine is not boosting off ofthe turbos, note the mph and stay at that.

If the the turbos are in sequential set up still then search for what rpm the first turbo kicks in and stay below that point.

No boost means no extra fuel.

A lot can depend on the map too. Looking at the wideband my map gets richer at lower speeds on the motorway, in the 12\'s on the wideband.

Shaun

[turbotoaster]

A lot can depend on the map too. Looking at the wideband my map gets richer at lower speeds on the motorway, in the 12\'s on the wideband.

Shaun

thats mapped well to rich then!

anytime your in vacuum it shouldnt be richer than stoic, anymore and your wasting fuel.

i know people are bored about me bleeting on that i can 28mpg average but with fuel prices still rising and people getting put off buying rotarys because they get told they use alot of fuel then its worth looking at.

from 40mph upwards my afrs are between 15-16, only time ill add more fuel is if the engine stumbles(normally does when you go to 16.5-17) this way im only using the fuel required to complete my journey and as some believe help against carbon deposits

though i think running at 14 or 16 wont make much of a difference there.

[12at]

who cares you own a rotary!! if you want it to perform well you wont care what your fuel bill is like and if you want it to go well you would be happy with paying the extra in fuel!!
 
thats one thing i dont get with you english guys - you get all excited with 30mpg out of a rotary!! :2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes

[Will66]

At 135 pence a litre you need to get excited about fuel consumption or have a different daily driver.

[Aubec]

who cares you own a rotary!! if you want it to perform well you wont care what your fuel bill is like and if you want it to go well you would be happy with paying the extra in fuel!!
 
thats one thing i dont get with you english guys - you get all excited with 30mpg out of a rotary!! :2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes:2Rolleyes

Curious as to how much you pay for fuel in your neck of the woods?  A wee bit less than us I bet!

[shaunwil]

thats mapped well to rich then
anytime your in vacuum it shouldnt be richer than stoic, anymore and your wasting fuel.

i know people are bored about me bleeting on that i can 28mpg average but with fuel prices still rising and people getting put off buying rotarys because they get told they use alot of fuel then its worth looking at.

from 40mph upwards my afrs are between 15-16, only time ill add more fuel is if the engine stumbles(normally does when you go to 16.5-17) this way im only using the fuel required to complete my journey and as some believe help against carbon deposits

though i think running at 14 or 16 wont make much of a difference there.

Just what I see on my wideband. Its high 12\'s going into 13\'s. It has done good mpg on motorway miles for a streetported engine !

I have got another daily so don\'t really worry about it too much, although that only does 18mpg on LPG ! Good before it cost the same as petrol 3yrs ago.

Shaun