Club 80-90 Forums

HarryMann wrote:matt,
within reason, as long as you brim on a level surface until nozzle auto-cut-off from time to time (& call that a 'brim') If you're not 'gushing it' flat out, should click-off pretty well consistently.
The you can call that brim to brim and work mpg off that.

That is.. squeezing that extra 6 litres in maybe not a brill idea as far as both overflow/leakage or mpg calcs. Tank just needs to be at same level, not full as such, which might be possible if problem no-varying.

True, though i'm not sure how consistant the fill point is... perhaps varies with exactly how much you ease back on the pump flow to stop it shutting off all the time?

Of course the other factor is that, after blatting from the Midlands to Pembrokeshire and back fully laden and abusing the loud pedal the mpg is going to be so bad that I probably don't want to know!!!!

I'll have a nose at a your suggestions over the weekend though whilst investigating the runnign problems which are starting to get worse see https://club8090.co.uk/forum/viewtopic.php?f=2&t=50660

Couldn't make it to SP6, but I did a fuel consumption check last weekend on a run to Oxfordshire and back if it's any interest to anyone.
Did 290 miles on 48.1 litres, which comes out at an amazing 27 and a bit to the gallon. Never been that good before, but I did think it seemed to running really nicely. I'm assuming this is down to the upgearing of the bigger wheels/tyres - now running on 195R15 and this was our first longish run on these (and since the clutch replacement and subsequent service and setting up)

Did 290 miles on 48.1 litres

Sure you are aware a 'single' fill-to-fill is not going to be too accurate without a longer history either side of it to smooth out the errors... but 27.4 mpg, v.good!

Now you have a start, maybe keep the figures going, rather than doing occasional fill-to-fills (which are usually very misleading)...

6,000 mile history



Pink = Consumption to date from start (if that isn't very smooth (& usually gradually descending, something wrong )
Yellow = Running-mean, last 3 fills (mainly for smoothing fillup level errors)
Blue = Fill-to-fill (reflects usage, load, weather, fill-errors, and +/- extremes are exacerbated by smaller fillup intervals e.g. see 127~128k miles)

So lately, she's been dong about 23- 24 mpg (average the yellow curve by eye)

But then, I could claim 30 mpg or less than 15 mpg, depending on frame of mind (but will definitely know when the air-filter gets blocked or the brakes are bindig or when the wind is in my favour on a hot day over a long run

HarryMann wrote: Sure you are aware a 'single' fill-to-fill is not going to be too accurate without a longer history either side of it to smooth out the errors... but 27.4 mpg, v.good!

Now you have a start, maybe keep the figures going, rather than doing occasional fill-to-fills (which are usually very misleading)...

Fair point, I intend to keep my figures up to date again from now, I did have them for the 6 months we spent in Europe, but they got rather damp and unreadable in a small flooding incident in El Rocio
From memory though I was averaging around 24 on the long hauls and about 18 "running around" locally.
I like the way you've put your figures together and I'll have a go at keeping a "proper" log

Hmmmm.....All this MPG would relly on accurate data, the only downside I can see is if the speedo is inacurrate,it will give spurious data? My speedo reads 50 MPH, sat nav says 46 MPH. I read somewhere Satnav is accurate? Every 100 miles would mean only 92 actual miles covered?

Does that make MPG worse? Even after a 1000 miles to smooth out figures it would put an 80 mile discrepency on the figures, but you vehicle has not done as many miles as the speedo records.

Mathematicians please, to clarify!

Steve

No, this is not a serious problem, for several reasons..

1) Firstly, just having the figures against any mileage standard, calibrated or not is important (e.g.

against my mileometer, its doing x mpg

)

2) Mileometer can be calibrated (fast milo gives high mpgs, slow gives low), so adjustement is reverse of those

Just use a GPS over say 5 or 10 miles, starting when the milo trips over to a fresh mile, and ending when it trips over to 10 miles further on (for instance) and snap-read the GPS reading (a passenger is best for this!)

Or, calibrate against motorway posts (at least 5, better over 10) Don't use 1 mile

3) If you read the Caption on top of that chart, you'll send I currently allow +2% on milo, that is, the milo is low-reading 2% (my pre-plot figures are all factored UP by 2%), Slobbos in the Wiki by 10% (though suspect maybe that's a bit high in retrospect)

4) Yes, tyre wear will affect things, so if you know you have new or old tyres, you know where you are going with this (calibrate again when slightly cut-in new tyres) and be aware as tyres wear will give high[/b ]mpg readings, so calculate an approx adjustment or re-calibrate.

Spreadsheets (partic Excel) makes all this so easy, once you have done the initial work (PM and I'll send an empty sheet with calcs and chart)... you need to have a bit of experience in managing data properly in XL, but instructions should help. It's mainly the updating of the chart, fairly easy to follow step-by-step, takes about 3 minutes to enter a new fillup & see it on chart. Chart can be exported as jpeg image.

PS. If you've Pm'd before and haven't received then PM again and thou shalt!

Odometers usally have slightly different calabration to speedometers, the latter usally reads 5...10% higher than actual speed (legal requirement). Therefore if your satnav reads 46mph when your dash is indicating 50mph, the satnav is probubly nearer the truth but at the end of the jeurny your trip counter probubly won't be so far out, unless you've got non standard tyre size or missmatched speedo drive. T3 speedo neadles tend to over read more through age (the neadle might need realigning on its spindle) but as the odo is fixed gearing, it won't change unless tyres/gearing is altered, or its drive starts sliping or fails completely (the former usally becomes the latter quite quickly).

A long motorway jeurnery is good for checking the odo. GPS devices are handy but if like me you don't have one, driver location signs are now apearing evey 0.5km along all major routes (to make it easyer for broken down cars being phoned in on mobiles easyer to find, handy to know when your syncro expires on the motorway) and the number on the 3rd line is the distance down the road in km - by recoding this number as you join a motorway and zeroing your trip its easy to read the marker at the last roll of your trip meter before leaving. The stakes at the side of the road are at 100m increments so you can count them on if the mileometer doesn't roll right when theres a sign ajacent. A good strech of the M1 (other motorways/A roads avalable) should be quite accurate even with big gradients and tree cover, which GPS isn't so good with. Just remember to divide the roadside distance by 1.61 if you have an impereal speedo.