Restrictor kit removal advice

Sounds about right. Above about 30mph or so, on a flat road,
aerodynamic drag has way more effect on how much fuel is needed to go
a certain distance than anything else, and it increases with the cube
of velocity. It would take very little fuel to keep a car moving if
there was no air resistance - rolling resistance and transmission
losses are pretty much all you'd be pushing against, and they're not
huge. Whether or not the _engine_ is operating at it's peak efficiency
doesn't have much effect (assuming it's not is a very extreme
operating mode). Incidentally, wide-open-throttle is where a petrol
_engine_ is likely to be most efficient (i.e. kicking out the most
power for a given amount of fuel - not giving the best MPG), if it's
not accelerating.

I'm sure a quick Google would tell you that most efficient operating
speeds are almost always sub-30mph. About the only exceptions I can
think of are aircraft and planing-hulled boats, which change their
operating modes above a certain speed.

 

This is a common misconception - working out average mpg on a long run
and comparing that with other 'averages', like urban cycle etc. leads
the user to beleive that higher speeds are more economical. What's
actually the case is that more constant speed driving is better than
stop-start, so a long cruise will give this impression.

Officially quoted fugures for the 4.0 'Limited' cherokee show 19.6mpg
at a constant 75mph and 27.4 at a constant 56 (and 15.7 Urban cycle).

This may not be for exactly the same model, but it certainly doesn't
support your assertion above.

 

Monkey wrote:

Yep , the lowest maintainable speed in top gear is the most efficient.
At 35mph on a perfectly flat road in 5th gear I can get over 200mpg
according to the (surprisingly accurate) trip computer in my car.

 

You know, about taking out the restrictor...oh never mind.
Still, it encouraged some lively debate, which is always nice.
(I will get the hang of top posting and snipping and stuff, honest!)

 

I will get the hang of this newsgroup thingy yet, I will!! (Just might not
not ask any silly questions anymore)

 

that's what it is.

what "supports my assertion", is that the Jeep has a real-time fuel
economy meter, and when doing just over 80mph, it's reading 27mpg or
so.

 

bad form yadda yadda

I should also say the reason I think it's the most economic speed is
it's the speed that the auto box has just kicked down a gear at i.e.
if you're sitting at 70-75 it "hunts" and keeps changing gear.

 

Furry muff, and the dropping into overdrive you describe below might
help explain it, but I'd be interested to know the readout if you were
to stay at a steady 50, 40, 30 etc. Trouble is, of course, that the
auto box may screw this up if it decides it wants to be in a lower
gear. Why they never have the facility to hold in a high gear I don't
know, as it would often be useful to avoid the 'hunting' you describe.

Pfah! Autos are all shite anyway. I hates them, I does.

 

Andrewr At Work wrote

Trust in your feelings young dirt crawler.

 

Excuse moi? I wasn't referring to general consumption only reinforcing the
motorway figures quoted by Pete. Anywhere from 70 to 85 it seems to be about
the same but one or two better at 84.
I don't have to invent anything, it has a lovely on board computer that
records all this stuff for me in several flavours and due to the way my
milage claims had to be done there was a nice 40,000 mile/3 year daily
record.

Best big saloon car *ever*. Flawless, unsurpassable. Shame they ruined the
plot this year.

 

5spd tiptronic auto's are the only option for a road car IMHO. Good ones
that is. As SteveH will testify the gearchange on mine is almost
undetectable and it's never caught out.
Merc have just launched a 7spd though. Should be a peach.

I drive with my left foot on the brake pedal, it makes a *huge* difference
to reaction times and to getting onto the power at an apex.

 

HAts are funny things...

When I wore my beret around HMS Warrior, I was invariably addressed as
"Airman!" or "Oi!"

When I wore my cap, it was "Sir".[1]

Which, as it had a shiny peak, was a bit silly, really.

[1] Only by non-UK personnel, it must be said.
--
| ___ Salad Dodger
|/ \
_/_____\_ GL1500SEV/CBR1100XXX/KH500A8/TS250C
|_\_____/_| ..61132../..14035.../..3157./.19406
(>|_|_|<) TPPFATUICG#7 DIAABTCOD#9 YTC#4 PM#5
|__|_|__| BOTAFOT #70 BOTAFOF #09 two#11 WG*
\ |^| / IbW#0 & KotIbW# BotTOS#6 GP#4
\|^|/ ANORAK#17
'^'

 

"Monsieur"

--
Platypus - Faster Than Champ
VN800 Drifter, R80RT
DIAABTCOD#2 GPOTHUF#19
BOTAFOS#6 BOTAFOT#89 FTB#11
BOB#1 SBS#35 ANORAK#18 TWA#15

 

Hog made the world a better place for us by saying..

just out of interest I did a little test tonight on the East Lancs Rd.
(between Billinge turning and Kirkby, heading towards Liverpool)
drove the same 4 mile section twice, in the same direction, on cruise.

at 80mph on an uphill section of rd (about 1/2 mile) the instant mpg gauge
dropped to 20mpg the avg over the 4 miles was 25.4 mpg
at 50mph on the same stretch , the instant gauge dropped to 12 mpg and rose
slooowly to about 15mpg. Avg over 4 miles 20.8 mpg.

I didn't have the patience to try it at 30 mph.

'98 BMW 540i V8 Auto.


--
Pete M.

Golf Gti (For Sale)
Alfa Romeo 164 TS.
Wahey, I'm a proper petrolhead again!"
Liverpool, Great Britain.

"you can lead a horse to water, but a pencil must be lead"

 

"Pieboy!"

 

If you valued your time/stress levels highly, surely it'd be a pretty
expensive bike? Cue 'Another f'ing CD question' thread etc.

 

what stress levels? I ask a question on here, read it at my leisure,
and put any words of wisdom into practice - easy peasy.

 

"Garcon!"

--

Dave

GS 850 x2 / SE 6a
SbS#6? DIAABTCOD#16 APOSTLE#16? FUB#3
FUB KotL OSOS#12? UKRMMA#19

 

It is?

 

Yes, it is. For single carriageways, in France, Germany, Spain,
Belgium, Luxembourg...