more mpg out of a 2.5?

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Well, for what it is worth, I drive around 900km a week, on two big 450km runs, and most of it are freeway routes, that I travel at 130km/h with the Cruise Control locked.
Both with and without the PSI powerbox I'm constantly getting 12.5lt/100km (around 19mpg).
I've checked everything ever suggested in this forum and that has now been repeated in this thread but there's no way to improve mileage. I'm now waiting for my Hawkeye to arrive to see if there's some sensor that's giving wrong values to the ECU.
 
mcapinha said:
Well, for what it is worth, I drive around 900km a week, on two big 450km runs, and most of it are freeway routes, that I travel at 130km/h with the Cruise Control locked.
Both with and without the PSI powerbox I'm constantly getting 12.5lt/100km (around 19mpg).
I've checked everything ever suggested in this forum and that has now been repeated in this thread but there's no way to improve mileage. I'm now waiting for my Hawkeye to arrive to see if there's some sensor that's giving wrong values to the ECU.
Click to expand...


Try running at 70 mph instead of 80 that may improve things. Mine is chipped and at motorway speed i get consistant figures well above 25 mpg. Depending on load.
 
Sounds correct to me: when cruising you`re just burning the fuel to overcome air resistance (& a little mechanical friction). The power box is having no effect on this.
Remember tho that air resistance is a function of the square of the speed. (double speed = 4 times air resistance).
The best way to get better mpg (m-way cruising) is drive slower. Simple.... but boring.
(Here`s some approx figures: theoretical, and approximate, but worth looking at, I`d say. If mcapinha does say 400km at 130 kph this takes about 3.07hrs= 3hr05.
If he travels at 115km (about 10% less) it takes 3.47hrs=3hr28.
This should use APPROX 0.9 squared fuel = 0.81 X prev fuel use.
Or 19% saving. Or of the 50-ish litres burnt on the m-way 10 are used to save about 20/25 minutes time. Only you the driver can say whether or not it`s worth it.)
NOTE these are all approx and purely on paper, BUT they are well worth looking at.
So if mcapinha has 50mins spare on his round trip, maybe he`d like to save 20?? or probably a little less litres? You can get better mpg, but do you want to enough??
(Sits back and waits for screams of protest...)
 
gtland said:
Sorry wammers you got that out quicker than me... had to have a coffee and rest my typing finger.
Click to expand...

Anything reasonable above 50 mph should be best. 65-70 is best for mine, returns good figures and makes decent progress. At 80 figures go down. All this is of course contrary to the governments slow down and save fuel crap. All vehicles have max efficiency speed/progress versus fuel used. 30 mph just ain't it unfortunatly. More so with automatics. As you say drag is the square of speed and power required. If you have a vehicle with 100 bhp that does 100 mph. To do 200 mph with the same vehicle you would need 400 bhp.
 
Exactly so: dropping speed from 130 to 110 kph should make significant fuel savings. Dropping speed down to 50kph or 30 emms ain`t gonna do much better. Air drag at these speeds becomes increasingly less important. Just the same old "boring" "non-sexy" stuff like actually putting air in tyres, taking off roof-racks, leaving that big bag of cement out of the boot, etc. Not much fun to talk about tho` is it?
 
Just out of curiosity, and going totally off-topic, what is the max speed limit in the UK ? 60mph is roughly 100km/h, which feels like driving while standing still at the same time :)

Still, I'll do one run at 60mph on the freeway, just to see what mileage it will give me.
 
Currently 70mph on motorways, but lots of traffic seems to go 75-80. There is some talk of upping the limit to 80, so a pan-european limit of 130kph seems on the cards.
If you do try running a little slower, please keep us posted. Having a regular run like that you seem to be in an ideal situation to do a meaningful test.
 
wammers said:
Anything reasonable above 50 mph should be best. 65-70 is best for mine, returns good figures and makes decent progress. At 80 figures go down. All this is of course contrary to the governments slow down and save fuel crap. All vehicles have max efficiency speed/progress versus fuel used. 30 mph just ain't it unfortunatly. More so with automatics. As you say drag is the square of speed and power required. If you have a vehicle with 100 bhp that does 100 mph. To do 200 mph with the same vehicle you would need 400 bhp.
Click to expand...


Yea ha a 400hp fender far out:rolleyes::rolleyes::rolleyes::rolleyes::D:D
 
HMMMMMMM
I fitted a psi powerbox on my old manual DSE p38 and i was getting 31mpg around town

I drove it from sheffield to Orkney, and back vis Thurso ( 1000 ) miles and AVERAGED 44 mpg .

"FACT"

And it was not what the fuel computer was telling me, it was what it was doing!

My current 3 ton 3 ltr is doing 25 miles around town and 30 on a run
 
Thats Bollocks said:
HMMMMMMM
I fitted a psi powerbox on my old manual DSE p38 and i was getting 31mpg around town

I drove it from sheffield to Orkney, and back vis Thurso ( 1000 ) miles and AVERAGED 44 mpg .

"FACT"

And it was not what the fuel computer was telling me, it was what it was doing!

My current 3 ton 3 ltr is doing 25 miles around town and 30 on a run
Click to expand...


Think the return trip must have been on the back of an AA recovery truck.:D:D:D
 
Thats Bollocks said:
HMMMMMMM
I fitted a psi powerbox on my old manual DSE p38 and i was getting 31mpg around town

I drove it from sheffield to Orkney, and back vis Thurso ( 1000 ) miles and AVERAGED 44 mpg .

"FACT"

And it was not what the fuel computer was telling me, it was what it was doing!

My current 3 ton 3 ltr is doing 25 miles around town and 30 on a run
Click to expand...


I think your name tag says it all:rolleyes:
 
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