Clubjazz - Honda Jazz & HR-V Forums
Honda Jazz Forums => Honda Jazz Mk4 2020 - => Topic started by: Downsizer on September 11, 2025, 02:38:32 PM
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During journeys up and down the A1 from Peterborough to Tyneside this week I generally had the cruise control set at 65-68 mph. I was surprised how often the car reverted to EV mode on flat sections, as I had assumed that at those speeds direct drive was almost permanent, apart from travelling downhill. Average fuel consumption was shown as 62-64 mpg, so the true figure was no doubt a bit lower. The external temperature was around 20C so no heating or cooling was needed.
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I've had that happen when the car needed to accelerate in order to close the rather large gap which had opened up due to a car in front going off left or me pulling out into a faster lane. It accelerated more rapidly than I would have done myself and presumably needed more power than was available in the rather high cruising gear. It can always use the motor to provide extra power in engine drive mode but perhaps not enough or not enough battery charge available.
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This chart may help.
It shows on aveage how often the hybrid is active.
It's a great system.
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Ignore my typo on 50mph as I put 50mpg - Doh !
It's a great system though. If your light on the throttle it's suprising how fast you can go on electric only before engine kicks in to recharge the battery .
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This chart may help.
It shows on aveage how often the hybrid is active.
It's a great system.
That's an interesting chart... I have the best consumption on a longer trip at 80km/h - that is, when supposedly in "Engine drive"...
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... I was surprised how often the car reverted to EV mode on flat sections, as I had assumed that at those speeds direct drive was almost permanent ...
The Honda drive train is quite cleverly thought out! Its main design goal is fuel efficency.
This is accomplished by keeping the ICE in one of several preconfigured load levels.
During direct (or engine) drive a clutch gets engaged that connects the ICE "directly" to the wheels and thus eliminating the losses of going through the generator - electric motor cycle.
The surplus energy at any speed is fed into the battery until it reaches a charge level of about seven bars on the HV-battery gauge. Upon reaching this charge level the drive train switches to pure electric until the charge level falls to three or less bars.
Then the ICE gets started again and the cycle begins anew.
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I find that Honda graphic rather strange. It shows that at speeds of over 120 km/h the car is back in hybrid mode presumably because the engine can't produce enough power in engine drive and hybrid mode will enable it to run faster and produce more power. It is strange because there is a video on youtube of a 2022 Crosstar running at 130 km/h. in direct drive mode and doing about 42 mpg - not bad for 81 mph.
If you look closely at the graphic you can see the engine drive mode symbol and see energy being fed to and taken from the battery as the gradient changes. The constant noise level seems to confirm that the engine is indeed running at constant speed
The more I study this car the more interesting it becomes!
By the way, if you see poor petrol consumption figures on the motorway remember headwinds. Since mpg goes down at roughly the square of the speed, hitting a 10 mph head wind at 70 mph will take the consumption from (say) 60 mpg to about 46 mpg if you maintain the 70 mph. [(80/70)^2 = 1.3].
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BTW the power flow graphic appears at about 1' 37" into the video.
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In addition to wind speed and direction, the system responds to almost imperceptible changes in road inclination. All very logical!
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I once towed a trailer at 100 km/h (62 mph). The engine was constantly revving higher than usual, being so loud that I could hear it over the road noise. Usually, without a trailer, I wouldn't hear the engine at that speed.
The car was using the hybrid mode the whole time and did not engage the direct drive. Apparently the added air drag + rolling resistance from the trailer required so much extra power that the engine needed to rev higher than what would have been possible when in direct drive mode. I think the fuel consumption was roughly 7 l/100km (40 mpg).
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I once averaged about 65 mpg heading east but only about 52 mpg on the same stretch of motorway when heading west. :o I began to think there was a problem with the car. ???
I then noticed that all the power generating windmills were orientated in a way that showed I had been assisted by a tailwind when driving east but against a constant headwind driving west. Windspeed was enough to turn the windmill sails but not noticeably strong .
I think this wind drag affect is enough to explain why the Yaris has a slightly better mpg figure than the more boxy styling of the (much roomier) Jazz. Not IMO due to any superiority in the Yaris drive mode. system.
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I once averaged about 65 mpg heading east but only about 52 mpg on the same stretch of motorway when heading west. :o I began to think there was a problem with the car. ???
I then noticed that all the power generating windmills were orientated in a way that showed I had been assisted by a tailwind when driving east but against a constant headwind driving west. Windspeed was enough to turn the windmill sails but not noticeably strong .
I think this wind drag affect is enough to explain why the Yaris has a slightly better mpg figure than the more boxy styling of the (much roomier) Jazz. Not IMO due to any superiority in the Yaris drive mode. system.
Just back from a short holiday 250 miles each way involving mostly M5, M6 and M54. We were unlucky and had a slight headwind both ways. With the ACC set to 70 mph but often slowed down we averaged about 56 mpg both ways which is much what we would have got in our old 2016 Polo with 4 cylinder 1.2 litre turbo petrol and GDI engine. Not a bad result for the Honda with probably similar gearing and NA engine with port injection. The Honda recuperation will have helped and of course overall the Honda mpg is about 10-15 mpg better.
The Yaris is bound to be better on the motorway. The clever planetary gearbox enables the engine to be run at the most efficient engine speed for any particular road speed whereas the Honda direct drive will be optimised for one specific road speed. The Yaris has a 3 cylinder engine - more efficiency and less refinement. I think it is port injection too so no GDI gain there. The Jazz is narrower but taller and we don't know about the Cd of either car so who knows which is the better car aero-wise.
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The Yaris is bound to be better on the motorway. The clever planetary gearbox enables the engine to be run at the most efficient engine speed for any particular road speed whereas the Honda direct drive will be optimised for one specific road speed.
I think the Jazz's engine is optimised for best efficiency between about 1,500 and 3,000rpm. Over that range the engine power increases in proportion to the rpm. The power needed to move the vehicle increases disproportionally with speed so the system has to switch out of direct drive to enable the engine to provide enough power.
Back in 2020 I used a smartphone app + bluetooth OBDII reader to see the engine rpm at different vehicle speeds. IIRC, direct drive was used between about 40 and 60mph on level road and constant speed. I assume that above about 3k rpm the second set of inlet valves opens to help increase the power output but at lower efficiency (this was the behaviour of older Jazz engines) which contributes to the big drop in fuel economy at motorway speeds. The appears to be one of the issues that Honda is addressing in the next generation e:HEV drivetrain https://global.honda/en/tech/Honda_eHEV_next_generation/.
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John,
Do you recall the mph/1000rpm in direct drive? I estimated that at about 25 mph/1000 rpm since that is pretty common for cars of about that weight, engine size and available torque. I guessed too that there must be a shift from a high efficiency regime to a high power one, perhaps from Atkinson cycle to Otto cycle since that can be done by the i-VTEC system changing cams, though not necessarily by switching from 8 valves to 16.
I have an OBD->bluetooth plug-in and the 'torque-pro' app but haven't got around to trying it on the Jazz.
My 2015 car is definitely in direct drive at 70 mph and the video above shows a pre facelift car in direct drive at 130 km/h, about 81 mph., presumably without a tailwind!
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Nice topic, wanted to post something similar about this for a while.
In my 2014 CT/Prius I can do up to 30mph EV only if I press the "EV" button. After 30mph it will disengage EV but I could still use the EV if I feather the gas to about half of the "ECO" range in my dash. It never goes in only EV over 45mph.
How's on the 2020+ Jazz? I'm planning to get one soon.
(https://freeimage.host/i/Kwnmdhv)
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The Honda system is quite different from Toyota's. In direct drive mode the engine is driving the wheels directly and also the generator, which may be merely rotating. The motor is available too, both for extra torque and also for recuperation. On the motorway, if one has done a long descent, the battery may be fully charged and the car will then use the battery with the engine off at speeds of 70 mph or more in order to get the charge state down to 30% or so, presumably to provide capacity for more recuperation There is no way to enable or disable EV mode - it just happens when the car's programming decides.
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Great, glad to hear its so efficient at highway speeds. I mostly drive at 60mph so its going to be a joy to see the engine cutting while descending.
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So does that mean Honda system is better than Toyota or is it a
matter of personal choice? or is one more reliable than the other?
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Nice topic, wanted to post something similar about this for a while.
In my 2014 CT/Prius I can do up to 30mph EV only if I press the "EV" button. After 30mph it will disengage EV but I could still use the EV if I feather the gas to about half of the "ECO" range in my dash. It never goes in only EV over 45mph.
How's on the 2020+ Jazz? I'm planning to get one soon.
(https://freeimage.host/i/Kwnmdhv)
It is slightly different for the Jazz. It does not have an EV button, you just start it up and the engine will remain off if you do not require heat. For as long as the battery remains charged enough. But you can drive on EV even at 80 mph under certain circumstances.
It will determine all by itself what is most efficient. Usually it switches between EV mode and direct drive intermittently.
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So does that mean Honda system is better than Toyota or is it a
matter of personal choice? or is one more reliable than the other?
I wouldn't go that far even on a Honda forum ;D
After a test-drive. Toyota's system (3rd gen hybrid) feels more refined than Jazz 2020+. Toyota is at the 5th generation of hybrids now and they sold tens of millions worldwide.
Honda did sell quite a bit but barely 5% of what Toyota did.
In terms of reliability - both japanese brands are on top of the lists anywhere you look.
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Toyota has slightly lower consumption, Honda is quieter (except for HR-V).
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Toyota has slightly lower consumption, Honda is quieter (except for HR-V).
Yes, the German AA (www.adac.de) measure the noise level at 130 km/h inside the cars they test. IIRC the Jazz is quieter than both the Yarris and Corolla hybrids and the same as the Prius. In the case of the Yarris the car has both a three cylinder engine (Jazz has four) and more gears engaged in the transmission, including the famous planetary gear system. On the motorway some people find the change in engine in engine note of the Toyota annoying whereas the Honda is constant with its fixed gear.
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The Honda e:HEV cars are "self-loading" electric cars and have (almost) the same driver's characteristics as a true EV.
"Almost" because the "immediate" throttle response is highly dependant on the charge level of the HV-battery (which is deplorably very limited in our current Jazzes).
The Toyota "Synergy Drive" system is very cleverly thought out (and time-tested!). Thanks to its variable transmission it allows for slightly better fuel economy (especially at elevated speeds) while at the same time forgiving Honda's transition-free drive experience.
I have to admit, as a Jazz-owner I'm biased on this one!
However, the very smooth ride the Jazz e:HEV system provides had me hooked on the first test drive :D
(still can't wipe that wide smile off my face...)
imho, next to a true EV nothing comes close to this (and even I am willing to forgive a few a MPG for this comfort of ride and I'm not complaining - see my signature: now "scratching" the 70-barrier) :)
Addendum: I'm living in eastern Switzerland. We do have "hills" (hundreds to two thousands+ of metres high) and are subject to weather conditions involving snow (occasionally up to 40cm in my region) - so: 69+ MPG is quite an achievement! (I couldn't get my previous car (VW Polo) any higher than 52.8 MPG)
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I'm getting back on topic. Don't you think that the chart from jasonevans contradicts the table in the manual?...
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Both are true, but both are a simplistic version of reality.
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I've occasionally had the EV light come on and the constant fuel consumption bar drop to zero at speeds as high as 137 kph (85 mph) :o . . Presumably these occurred under optimum conditions, downhill with a tail wind.
I have assumed this meant I was in EV mode with the engine off. I'm not going to risk confirming this by concentrating on power flow monitors whilst driving at speed. :P I'm content to let the car do its own stuff.
This situation seems to be contrary to both charts.
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I think there is a discrepancy between the two charts.
And it would be best if the current driving mode was displayed on the display - see point no. 12 (https://clubjazz.org/forum/index.php?topic=17635.msg150677#msg150677).
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I think there is a discrepancy between the two charts.
And it would be best if the current driving mode was displayed on the display - see point no. 12 (https://clubjazz.org/forum/index.php?topic=17635.msg150677#msg150677).
Hybrid just means mixed. It is direct drive and EV drive intermittently or (depending on speed) generator powered driving and EV intermittently. More icons would be overcomplicating things.
The energy flow diagram (center screen) is however very clear!
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But who watches the screen with energy flow diagram...
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But who watches the screen with energy flow diagram...
Not me.. and never have. I have it set at the 'standard' speedo/mileometer and general info display. Anything else is a gimmick.
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But who watches the screen with energy flow diagram...
If you want to know exactly what your car is doing! It is my standard screen :D
To me this makes more sense than to have lights for EV on/off, engine on/off, generator on/off and whether it is serial or parallel etc. That would be a mess.
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IMHO, it would be enough for the driver's display, on each screen, to have three simple symbols of the driving mode that the car is currently using: pure electric motor, hybrid (the drive is provided by the electric motor, the combustion engine recharges the battery) and direct drive by the combustion engine.
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IMHO, it would be enough for the driver's display, on each screen, to have three simple symbols of the driving mode that the car is currently using: pure electric motor, hybrid (the drive is provided by the electric motor, the combustion engine recharges the battery) and direct drive by the combustion engine.
True, but in direct drive also the EV can help if additional power is required or generation can occur when engine power is still available.
I can imagine that the current EV light (just on or off) will at least explain (absence of) engine noise to the driver.
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IMHO, it would be enough for the driver's display, on each screen, to have three simple symbols of the driving mode that the car is currently using: pure electric motor, hybrid (the drive is provided by the electric motor, the combustion engine recharges the battery) and direct drive by the combustion engine.
Perhaps it would be best if no attempt were made to display what’s going on, which changes constantly, and just rely on the car doing what it’s designed to do!
But life would be duller I suppose. What would we discuss?
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Well, I'd be quite interested to see what driving mode I'm currently in.
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To be honest, I don't give a d@mn what driving mode our Jazz is in, as long as it gets us where we want to be in the comfortable, economical and safe mode. All three modes at the same time, please. ;)