Author Topic: MPG for those interested.  (Read 172711 times)

Jocko

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Re: MPG for those interested.
« Reply #315 on: March 02, 2019, 06:55:10 PM »
You could have got 97 RON in Morrisons. Nowhere near as expensive as the V-Power.

peteo48

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Re: MPG for those interested.
« Reply #316 on: March 03, 2019, 11:20:09 AM »
Yes - the supermarket high octane fuels only have a 5p mark up over the 95 unleaded. The brands charge at least 10 p a litre more for high octane stuff.

peteo48

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Re: MPG for those interested.
« Reply #317 on: April 15, 2019, 11:57:30 AM »
Just recorded my record mpg so far in the Mk 3 - 52.6 actual (showed as 54.9 on the computer). Quite happy with this as it included a recent round trip of 220 miles with 3 adults and luggage in the car and also cruising a lot of the time at 70 mph.

Jocko

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Re: MPG for those interested.
« Reply #318 on: April 15, 2019, 12:39:26 PM »
Those are good numbers. Particularly at this time of year. The same journey, in the summer, would have been even better.

andruec

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Re: MPG for those interested.
« Reply #319 on: April 16, 2019, 09:33:37 PM »
Just thought I'd drop by to give you the figures for my first two tanks with my Corolla hybrid. 56 and 58 at the pump (reported as 58 and 59 by the car). My Jazz was turning in around 50 mpg at the pump for comparison when I sold it.

I'm pretty sure I could do better because at the moment I'm being lazy and using the adaptive cruise control virtually all the time. Although it uses EV mode some of the time I know a few places where I could get it into EV mode a bit earlier. Got my first long motorway drive next week so will be interesting to see how it does. My Jazz would get me over 60mpg on my trips to North Wales and that's going to be tough to beat - basically a fight between a 1.3 litre engine in Atkinson mode and a 1.8 litre in Atkinson mode. It does use the battery power occasionally at 60 mph and cruises at less than 1,500 rpm but I don't know if it will be enough to return a better figure.

I'll be very interested to see the figures for the new Jazz Hybrid when it finally arrives.
« Last Edit: April 16, 2019, 09:35:10 PM by andruec »

John Ratsey

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Re: MPG for those interested.
« Reply #320 on: April 17, 2019, 06:32:07 PM »
I'm pretty sure I could do better because at the moment I'm being lazy and using the adaptive cruise control virtually all the time. Although it uses EV mode some of the time I know a few places where I could get it into EV mode a bit earlier. Got my first long motorway drive next week so will be interesting to see how it does. My Jazz would get me over 60mpg on my trips to North Wales and that's going to be tough to beat - basically a fight between a 1.3 litre engine in Atkinson mode and a 1.8 litre in Atkinson mode. It does use the battery power occasionally at 60 mph and cruises at less than 1,500 rpm but I don't know if it will be enough to return a better figure.
My guess is that for sustained cruising at 60 mph or above your Corolla will pull ahead on mpg as it sits lower on the road and should be aerodynamically better than the Jazz by a big enough margin to offset any deadweight due to the hybrid system. Cruising at 50 or below probably sees the Jazz pull ahead. Don't forget the Land's End to John O'Groats run by the Mk 3 Jazz - very impressive mpg at a sustained 40 mph. Hybrids best deliver their benefit in variable speed motoring.
2022 HR-V Elegance, previously 2020 Jazz Crosstar

andruec

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Re: MPG for those interested.
« Reply #321 on: April 17, 2019, 07:09:44 PM »
I'm pretty sure I could do better because at the moment I'm being lazy and using the adaptive cruise control virtually all the time. Although it uses EV mode some of the time I know a few places where I could get it into EV mode a bit earlier. Got my first long motorway drive next week so will be interesting to see how it does. My Jazz would get me over 60mpg on my trips to North Wales and that's going to be tough to beat - basically a fight between a 1.3 litre engine in Atkinson mode and a 1.8 litre in Atkinson mode. It does use the battery power occasionally at 60 mph and cruises at less than 1,500 rpm but I don't know if it will be enough to return a better figure.
My guess is that for sustained cruising at 60 mph or above your Corolla will pull ahead on mpg as it sits lower on the road and should be aerodynamically better than the Jazz by a big enough margin to offset any deadweight due to the hybrid system. Cruising at 50 or below probably sees the Jazz pull ahead. Don't forget the Land's End to John O'Groats run by the Mk 3 Jazz - very impressive mpg at a sustained 40 mph. Hybrids best deliver their benefit in variable speed motoring.
Yeah, I have driven a few relatively short sections of MWay/DC at 60mph and it was interesting to see how 'active' the system was in mixing the two power sources. A lot of people think that the hybrid stuff is all or nothing but actually it's forever swapping between sources and often combines them.

I can just about see that if it can cruise at 60mph at <1,500 rpm and it comes to a slight incline it might make sense to utilise the battery rather than increase the RPMs. Of course the battery energy is not free(*) so eventually it has to increase the engine RPMs above what's needed for cruising in order to recharge. But perhaps (and these are made up numbers) it goes something like:

Climbing an incline with battery+engine@1500 followed by engine@2000 temporarily to recharge saves more fuel than climbing the incline at 2500rpm.

And of course most inclines are followed by a decline which will help improve the advantage further.

One thing I've noticed is the performance difference. From stationary and at low speed the Corolla would leave a Jazz in the dust. It's actually quite 'scary' just how much get up and go you get when it's an electric motor doing the work. At higher speeds there's little to nothing in it and in fact I think that in 'normal' mode at least the Jazz might have the edge. In 'power' mode possibly not but it seems that a 1.3 l engine operating on the Otto cycle outguns a 1,8 l engine operating on the Atkinson cycle and the battery can only help overcome that for a while.

(*)In fact several experts say that trying to run in EV mode as much as possible is actually not the best strategy. The system is around 80% efficient so they say that the car should be left to mix/match as it sees fit rather than trying to play the 'I'm an electric car' game.
« Last Edit: April 17, 2019, 07:12:33 PM by andruec »

Downsizer

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Re: MPG for those interested.
« Reply #322 on: April 18, 2019, 05:05:56 PM »
My guess is that for sustained cruising at 60 mph or above your Corolla will pull ahead on mpg as it sits lower on the road and should be aerodynamically better than the Jazz by a big enough margin to offset any deadweight due to the hybrid system. Cruising at 50 or below probably sees the Jazz pull ahead. Don't forget the Land's End to John O'Groats run by the Mk 3 Jazz - very impressive mpg at a sustained 40 mph. Hybrids best deliver their benefit in variable speed motoring.
The only drag figures I've been able to find suggest coefficients of 0.30 for the new Corolla, and 0.33 for the Mk 3 Jazz/Fit.  Drag increases as the square of speed, so as you suggest, the Corolla should be more fuel efficient at higher speeds.  It's an interesting comparison in anticipation of a Jazz hybrid.  I'm not yet convinced that non plug-in hybrids achieve much in overall economy, but they should be cleaner in urban areas in electric mode.

andruec

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Re: MPG for those interested.
« Reply #323 on: April 18, 2019, 07:40:51 PM »
I'm not yet convinced that non plug-in hybrids achieve much in overall economy, but they should be cleaner in urban areas in electric mode.
They definitely achieve a lot better economy in urban/extra urban use. My daily commute is 9 miles free running A road and 2 miles busy town. I was getting ~50mpg in my Jazz when I sold it a month ago and am getting ~58mpg in the Corolla. And that figure for the Corolla is a new, tight engine.

peteo48

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Re: MPG for those interested.
« Reply #324 on: August 01, 2019, 12:41:03 PM »
I'm always cautious about the debate over high octane or super fuels and I'm not sure what to read into my latest refill which is the third consecutive refill after using 97 or 98 Octane.

But here's the thing. I filled up today on Sainsburys 97 RON after 189 miles on Apple Green 97 RON and that followed on from a tank of 97 RON from Sainsburys. The average speed was 16 mph and, for a large chunk of that 189 miles I've been travelling, in rush hour traffic to feed my daughters pets whilst she was on holiday. I also had some real crawling motoring when attending and leaving the RHS Tatton Flower Show a fortnight ago.

Yes it's been warm but I have also driven through heavy rain - a lot of standing water. This last refill shows an mpg of 45.5 - I've never had this sort of mpg after driving in heavy traffic. I would have expected around 42 tops.

Early days but I am starting to be convinced that there are gains to be had from using the higher octane fuel in the Mk3 Jazz which does, of course, have a very high CR. I am also sensing a slight improvement in responsiveness.

I'll report further on this. Given fuel costs are a minor consideration for me due to the low annual mileage I do (less than 3000 in 2018) I tempted to stay on the higher octane stuff for a few more tanks at least.

Kenneve

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Re: MPG for those interested.
« Reply #325 on: August 01, 2019, 04:17:20 PM »
The figures you quote represent an increase in MPG of 8.3% I guess an average the cost difference of Super-unleaded fuel is in the order of 12%, so that gives a real increase of probably less than 4%, which is easily accountable with traffic conditions, style of driving and/or performance, Stick with the Super fuel!!

Downsizer

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Re: MPG for those interested.
« Reply #326 on: August 02, 2019, 10:49:25 AM »
Re super fuel, I seem to remember someone suggesting previously that the variable valve timing would in some way detect the higher octane fuel and in effect adjust the compression ratio accordingly.  I have some doubts about this, but it's an interesting idea - does anyone knows more about it?

Jocko

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Re: MPG for those interested.
« Reply #327 on: August 02, 2019, 11:48:49 AM »
It is not the variable valve timing but the knock sensor that allows the ignition to be advanced some, with "super" fuels.

mikebore

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Re: MPG for those interested.
« Reply #328 on: August 02, 2019, 12:01:16 PM »
It is not the variable valve timing but the knock sensor that allows the ignition to be advanced some, with "super" fuels.

For many years I was firmly in the camp that believe if the octane is high enough to prevent knocking there is no benefit for higher octane. But the advent of knock detection and automatic ignition advance to the point where it is just not knocking, gives a technical basis why higher octane might be more efficient, or more powerful.

However I have never seen any convincing data supporting this. There are lots of reports by people who know which fuel they are using and therefore tend believe they notice a difference. I have used Shell 99 sometimes and don't believe I could tell which fuel was in the tank by power or economy.

culzean

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Re: MPG for those interested.
« Reply #329 on: August 02, 2019, 12:02:21 PM »
Re super fuel, I seem to remember someone suggesting previously that the variable valve timing would in some way detect the higher octane fuel and in effect adjust the compression ratio accordingly.  I have some doubts about this, but it's an interesting idea - does anyone knows more about it?

From what I have read about modern direct injection engines, particularly Honda and Mazda they avoid knocking at lower revs by injecting the fuel when compression stroke nearly at top dead centre ( if you are only compressing air it does not matter if it heats up ). I read that Honda DI nozzle is centrally located in cylinder head, and at lower revs actually injects fuel at over 40:1 ratio into a bowl in the piston crown - at higher revs the fuel map changes and he fuel is injected on intake stroke at 14.5:1 ratio.  So on direct injection engines even though some over 13:1 compression ratio knocking is dealt with by the way fuel is injected.

The Civic 1.8 ivtec engine has had variable compression ratio controlled by late closing of inlet valves at lower revs since 2006 ( thus mimicking the mechanical stroke variation in a 'proper' Atkinson cycle engine without all the complication ) but not direct injection at that time, could not comment on whether the detection of knocking by the normal sensors affects the closing point of inlet valves but I doubt it.
« Last Edit: August 02, 2019, 01:04:32 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

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