Author Topic: What MPG are you getting from your Mk1 Honda Jazz ?  (Read 201217 times)

smilertoo

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #300 on: January 19, 2019, 09:09:51 PM »
wait, you're saying faster acceleration is better than taking your time?

Jocko

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #301 on: January 19, 2019, 09:42:15 PM »
That is the Hypermilers way of doing it. With 80% throttle the engine works more efficiently. You want to accelerate with the  engine operating around the maximum torque changing gear to keep it there. But only accelerate to the speed you want to reach. If you have to brake you are only wasting energy you used to get to that speed.
Best way to save fuel is anticipation.

John Ratsey

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #302 on: January 20, 2019, 09:03:05 AM »
That is the Hypermilers way of doing it. With 80% throttle the engine works more efficiently.
However, I wonder if this applies to Honda's newer 16 valve engines where half the inlet valves stay closed below around 3,000 rpm in order to improve the fuel mixing and hence the efficiency in this lower rpm lower power range. Honda's recent vehicles with CVT transmission achieve better test mpg than the manual gearbox versions. Those CVT vehicles don't rev to anywhere near the maximum torque range without putting the whip to them as if they think it's less efficient. However, it may just be that Honda feel that customers don't normally want the extra noise which comes with the higher revs.

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Jocko

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #303 on: January 20, 2019, 11:10:47 AM »
The only way to find out is to try both approaches for a few tankfuls and see what returns the better mpg. If neither one wins out then it doesn't really matter.

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #304 on: January 20, 2019, 11:18:42 AM »
That is the Hypermilers way of doing it. With 80% throttle the engine works more efficiently.
However, I wonder if this applies to Honda's newer 16 valve engines where half the inlet valves stay closed below around 3,000 rpm in order to improve the fuel mixing and hence the efficiency in this lower rpm lower power range. Honda's recent vehicles with CVT transmission achieve better test mpg than the manual gearbox versions. Those CVT vehicles don't rev to anywhere near the maximum torque range without putting the whip to them as if they think it's less efficient. However, it may just be that Honda feel that customers don't normally want the extra noise which comes with the higher revs.

To achieve atkinson cycle on newer engines below 3000 they keep all inlet valves open until well into compression stroke and allow mixture ( or just compressed air with direct injection engines like mk3) to escape back into inlet manifold, this lowers compression ratio and makes engine more efficient but also lowers power. This was first introduced in civic 8th gen 1.8 VTEC ( 2006 to 2012 ) but mk2 jazz ( 2008 to 2015 ) did not get it. This reduces pumping losses which are big source of inefficiency on petrol engines, Honda also manage to keep throttle butterfly almost fully open during Atkinson cycle which further reduces pumping losses. Maybe the hypermilers are trying to keep throttle more open to reduce pumping losses during acceleration as pumping losses are due to engine having to suck against throttle butterfly and are highest at low revs when butterfly is normally almost closed on a normal petrol engine.  Direct injection petrol engines behave more like a diesel ( which don't get pumping loss as they don't have a butterfly, power is controlled by timing and amount of fuel injected ).

Original VTEC  12/16 valve engines used to only partially open one inlet valve and fully open the other to induce 'swirl' in the in-going mixture.  This may still be the case on mk2, but not mk1 which only has one inlet valve anyway and no VTEC cams .  The I-vtec mk2  engine has additional trick to move the camshaft timing in relation to crankshaft by means of a helix between the pulley and camshaft.

Looking at this comparison between I-dsi and 1.5 vtec it seems Honda stayed with  12/16 valve method for 1.5 vtec ( article is from Asia ) so maybe still used it for the European 1.2 and 1.4 of the same period.

http://asia.vtec.net/Series/FitJazz/lseries/

Also

https://en.m.wikipedia.org/wiki/Honda_L_engine
« Last Edit: January 20, 2019, 11:42:45 AM 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

Jocko

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #305 on: January 20, 2019, 11:48:18 AM »
As I have said elsewhere, reducing pumping losses are one of the goals of open throttle acceleration. The reason 80% throttle is recommended instead of 100% is that normally 80% keeps the ECU in closed loop mode where 100% takes it into open loop territory, which disregards the O2 sensor. It is a bit like the extra spurt of fuel that full throttle on a carburettor engine gives, derived from the accelerator pump.

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #306 on: January 20, 2019, 05:14:19 PM »
Honda's recent vehicles with CVT transmission achieve better test mpg than the manual gearbox versions.

But the Jazz that went from Lands end to john O'Groats on one tank of fuel was a manual gearbox,  just goes to show that in proper hands the manual box can outperform the CVT in the MPG area.

Maybe by using an economy electronic map for CVT the revs can be kept low as possible even though the accelerator is being pressed hard,  but in sport mode the car behaves more like a spirited driver with a manual box so MPG suffers.  So with a human in charge using experience and anticipation ( and all the other stuff humans can do that computers cannot ) the manual box still outperforms the CVT.

I bet the hypermilers prefer a manual box as well,  as it absorbs least power than other options.
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

peteo48

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #307 on: January 20, 2019, 05:23:50 PM »
Honda's recent vehicles with CVT transmission achieve better test mpg than the manual gearbox versions.

But the Jazz that went from Lands end to john O'Groats on one tank of fuel was a manual gearbox,  just goes to show that in proper hands the manual box can outperform the CVT in the MPG area.

Maybe by using an economy electronic map for CVT the revs can be kept low as possible even though the accelerator is being pressed hard,  but in sport mode the car behaves more like a spirited driver with a manual box so MPG suffers.  So with a human in charge using experience and anticipation ( and all the other stuff humans can do that computers cannot ) the manual box still outperforms the CVT.

I bet the hypermilers prefer a manual box as well,  as it absorbs least power than other options.

Without even beginning to understand the science - this actually makes sense. The CVT probably does edge it with a "normal" person behind the wheel but the manual affords more scope for the experienced hypermiler.

Jocko

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #308 on: January 20, 2019, 05:33:57 PM »
I bet the hypermilers prefer a manual box as well,  as it absorbs least power than other options.
A true hypermiler would always choose a manual, not just from the power absorption but the fact that they are in control of everything it does. Mind you, some of the things they do are so extreme for fractions of a mpg. Things like moulding body parts, taping off panel joints and door openings and flushing wheels, wheel apertures, and even complete under-bodies!

peteo48

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #309 on: January 20, 2019, 05:59:26 PM »
Wow!

Yes - I've seen some pretty bonkers stuff on hypermiling forums. That car above, especially the back end, looks like my Dad's old Standard Vanguard. A Jazz/Vanguard hybrid.

John Ratsey

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #310 on: January 20, 2019, 06:37:31 PM »
But the Jazz that went from Lands end to john O'Groats on one tank of fuel was a manual gearbox,  just goes to show that in proper hands the manual box can outperform the CVT in the MPG area.
With someone from the Honda factory on board who would have had access to the detailed performance data and thus knew the optimum engine / gearbox settings to get the best economy. They must have worked out beforehand that they stood a reasonable chance of succeeding. If we had access to thie same information then we wouldn't need to be discussing the optimum driving style for getting best mpg.
2022 HR-V Elegance, previously 2020 Jazz Crosstar

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #311 on: January 20, 2019, 07:01:12 PM »
But the Jazz that went from Lands end to john O'Groats on one tank of fuel was a manual gearbox,  just goes to show that in proper hands the manual box can outperform the CVT in the MPG area.
With someone from the Honda factory on board who would have had access to the detailed performance data and thus knew the optimum engine / gearbox settings to get the best economy. They must have worked out beforehand that they stood a reasonable chance of succeeding. If we had access to thie same information then we wouldn't need to be discussing the optimum driving style for getting best mpg.

The team stayed below 40mph, maybe some of the people I follow are hypermilers, trouble is they do 40 in 60, 50, 40, 30 and often 20 limits, so maybe 40 is the optimum speed....
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

Jocko

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #312 on: January 20, 2019, 09:13:30 PM »
I watched the video. Seemingly the car was bog standard with no special help from Honda. The dealer supplied the car and the AA drove the escort vehicle. Following behind the van would certainly help.
For those that ask how far you get after the display shows zero miles left, their car showed zero with 60 miles still to go!

Bigal

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #313 on: January 22, 2019, 09:04:12 PM »
Just bought a jazz 1.4 good condition only seem to be getting 38 mpg and that's not going fast any tips why so love guys I'm new to this forum any help muchly appreciated

Jocko

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #314 on: January 23, 2019, 08:33:08 AM »
Check your tyre pressures. I set mine to 35 psig. After a longish run check the wheel centres for heating. That way you can discount a dragging brake.
The rest comes down to driver tweeks. Do you accelerate up behind traffic then have to brake? Anticipation is what gives good mpg. Avoiding the need to brake by leaving a good gap and anticipating the traffic ahead. Use higher gears. I invariably drive round town in 5th, changing down to 3rd for roundabouts. I usually skip 4th, both changing up and down (though I will go into 4th on an uphill section or in flat 20 mph zones).
I never turn the heat on until blue light has gone out. No point in trying to heat the cabin at the expense of warming the engine up. On descents get your foot right off the accelerator. This allows DFCO to operate and engine burns no fuel at all. Foot lightly on throttle negates this.

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