Author Topic: Atkinson engine and CVT  (Read 15265 times)

Roddy0000

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Atkinson engine and CVT
« on: August 16, 2018, 10:21:10 PM »
Hi
I have read several threads about the Atkinson engine being sluggish, I have the CVT version and have not found this to be the case as I think the revs are higher in normal driving than the manual maybe, I do find that I have to make the engine work harder compared with my mk2, I have not actually driven a manual but would value other peoples thoughts on this. Thanks.

andruec

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Re: Atkinson engine and CVT
« Reply #1 on: August 16, 2018, 10:33:19 PM »
You do have to kick it out of Atkinson mode when you want to move, at last the original version. The facelifted version might have better programming in this respect - the courtesy car I drove earlier this year seemed better.

It's the downside of an automatic - the car can choose what ratio it wants and unless you signal your intentions the older Mk3 prefers to keep the rpm low.

Ralph

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Re: Atkinson engine and CVT
« Reply #2 on: August 17, 2018, 07:10:23 AM »
I had a mk3 manual which I replaced with a facelift cvt the Atkinson cycle was more noticeable in the manual especially when moving off from standstill below 2k revs there was no power resulting in the occasional stall the hair trigger accelerator peddle didn’t help. The cvt has none of these problems I never notice the Atkinson cycle if you want to get a move on it just goes, its eager to rev above 2000 rpm until it gets up to speed then the revs drop to lower than the manual I don’t notice having to kick it out of Atkinson mode if I put my foot down it goes faster!

Skyrider

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Re: Atkinson engine and CVT
« Reply #3 on: August 17, 2018, 08:03:14 AM »
That is interesting, I switched from a manual 1.3 to a CVT 1.5. You mention stalling, coming from decades of diesel driving we both found this an occaisional problem when moving off. Particular care was required when turning into our street, an uphill right turn on a busy road. I think the torque converter must help when moving off in a CVT 1.3 possibly disguising it's gutless low rev power output. As I have said before I consider my purchase of a manual 1.3 a mistake as you have to work at driving it, making allowances for its lack of low speed performance. A good car spoiled by poor engine programming. The 1.5 engine totally transforms the car, making for relaxed progress, certainly with the CVT, but I would expect the same with a DIY gearbox.

Roddy0000

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Re: Atkinson engine and CVT
« Reply #4 on: August 17, 2018, 08:24:22 AM »
You do have to kick it out of Atkinson mode when you want to move, at last the original version. The facelifted version might have better programming in this respect - the courtesy car I drove earlier this year seemed better.

It's the downside of an automatic - the car can choose what ratio it wants and unless you signal your intentions the older Mk3 prefers to keep the rpm low.

On a cvt how do you kick it out of Atkinson mode, can someone please explain Atkinson mode. Thank you. 

andruec

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Re: Atkinson engine and CVT
« Reply #5 on: August 17, 2018, 08:27:30 AM »
That's interesting that you had problems with the manual. The previous courtesy cars I had were manual and I didn't notice any problems. I've always thought that manual gearboxes have one advantage in this respect (about the only one they have in my opinion :) ) in that if you want to move rapidly you select a lower gear. By doing that you're automatically selecting a higher RPM and moving the engine out of Atkinson mode.

But I generally follow IAM guidelines which means in built-up areas I'm rarely higher than third anyway so perhaps I was actually preventing Atkinson mode.

andruec

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Re: Atkinson engine and CVT
« Reply #6 on: August 17, 2018, 08:34:43 AM »
You do have to kick it out of Atkinson mode when you want to move, at last the original version. The facelifted version might have better programming in this respect - the courtesy car I drove earlier this year seemed better.

It's the downside of an automatic - the car can choose what ratio it wants and unless you signal your intentions the older Mk3 prefers to keep the rpm low.

On a cvt how do you kick it out of Atkinson mode, can someone please explain Atkinson mode. Thank you.
Basically it's all about RPM. The engine switches between the two modes at around 2,500rpm. With the CVT model what I've found works is to jab the accelerator pedal down when you want to move. Not all the way to the floor as that's surprisingly/pleasingly dangerous in traffic but there is a kind of 'notch' part way down. If you rapidly push the pedal down to that point it acts like a kick down and the CVT will select a much lower ratio. As a result the engine RPM will jump up (typically to 3,000 rpm) and you'll find you move quite nicely. You also get a rather nice growl from the engine/exhaust. Not exactly sporty (the 1.3 doesn't really do sporty) but certainly a 'right, let's get down to business' note :)

As for the two modes: Atkinson mode modifies the way the valves operate so that it's similar to what an 'Atkinson Cycle' engine does. This makes the engine more efficient but gutless. The normal operational mode is called 'Otto Cycle'.
« Last Edit: August 17, 2018, 08:37:59 AM by andruec »

Skyrider

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Re: Atkinson engine and CVT
« Reply #7 on: August 17, 2018, 08:42:39 AM »
You do have to kick it out of Atkinson mode when you want to move, at last the original version. The facelifted version might have better programming in this respect - the courtesy car I drove earlier this year seemed better.

It's the downside of an automatic - the car can choose what ratio it wants and unless you signal your intentions the older Mk3 prefers to keep the rpm low.

On a cvt how do you kick it out of Atkinson mode, can someone please explain Atkinson mode. Thank you.

To get out of Atkinson mode you need to get the engine revs above about 3,000.

Here is an explanation of Atkinson, A Toyota video but the principal is the same. Atkinson engines usually have a hybrid system with a battery and motor to back up the engine at low revs, Honda forgot this with the 1.3 Jazz.

« Last Edit: August 17, 2018, 08:45:52 AM by Skyrider »

John Ratsey

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Re: Atkinson engine and CVT
« Reply #8 on: August 17, 2018, 08:49:18 AM »
On a cvt how do you kick it out of Atkinson mode, can someone please explain Atkinson mode. Thank you.
Your profile shows you have a 2011 Jazz (ie Mk 2) which doesn't have the Atkinson cycle mode. The Mk 3 1.3 Jazz has the Atkinson cycle mode at the lower end (<2,500 rpm?) of the rev range. This mode increases fuel efficiency by delaying closure of the inlet valves which allows some of the mixture to blow back into the manifold but there is the side-effect of reduced power. It works well in a hybrid system where the electric motor helps the low end power but doesn't work so well by itself. Hence the 1.3 Mk 3 Jazz engine needs revs to provide much power. With a manual gearbox the driver can effectively choose the revs and rate of acceleration but the CVT was programmed to increase the revs to around 3,000 rpm whenever it thinks more power is needed (the sales literature when it was released in 2015 claimed this "sporty" behaviour as an intended feature).  I personally found this behaviour a bit tiring and traded in the Jazz for an HR-V which lacks the Atkinson cycle mode and has a much more progressive delivery of power (the same powertrain is in the 1.5 Jazz).
2022 HR-V Elegance, previously 2020 Jazz Crosstar

Downsizer

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Re: Atkinson engine and CVT eg
« Reply #9 on: August 17, 2018, 08:52:29 AM »
After driving the 1.3 cvt for 25000 miles, I find there is ample power for my needs.  As an alternative to pushing the accelerator to the floor for immediate extra power in "D" mode, I find a couple of clicks on the left hand paddle change works well.  It reverts to lower revs as soon as you ease off, eg after overtaking.  I think the engine/transmission system is excellent, and overall is giving me about 52 mpg measured by fuel bought.

Skyrider

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Re: Atkinson engine and CVT
« Reply #10 on: August 17, 2018, 08:55:11 AM »
Well spotted John, I hadn't noticed that Roddy has a 2011 non Atkinson Jazz. Not that it matters, he may be a potential MK3 buyer or just be seeking information.
« Last Edit: August 17, 2018, 12:52:32 PM by Skyrider »

Skyrider

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Re: Atkinson engine and CVT eg
« Reply #11 on: August 17, 2018, 12:55:14 PM »
After driving the 1.3 cvt for 25000 miles, I find there is ample power for my needs.  As an alternative to pushing the accelerator to the floor for immediate extra power in "D" mode, I find a couple of clicks on the left hand paddle change works well.  It reverts to lower revs as soon as you ease off, eg after overtaking.  I think the engine/transmission system is excellent, and overall is giving me about 52 mpg measured by fuel bought.

If you find the 1.3 suits you that's fine, others have different priorities. Your fuel consumption indicates the type of driver you are.
« Last Edit: August 17, 2018, 01:19:04 PM by Skyrider »

Ralph

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Re: Atkinson engine and CVT
« Reply #12 on: August 17, 2018, 01:52:47 PM »
I test drove both the 1.5 & 1.3 cvt’s. I liked the extra power of the bigger engine, the 1.3 has to rev more to get past the low power stage. But not having all the goodies that the EX has swung it for me. The gearbox solves all the issues I had with the 1.3 manual and I quite like a revy engine I’m happy with my Choice.

mikebore

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Re: Atkinson engine and CVT
« Reply #13 on: August 17, 2018, 03:24:52 PM »
You do have to kick it out of Atkinson mode when you want to move, at last the original version. The facelifted version might have better programming in this respect - the courtesy car I drove earlier this year seemed better.

It's the downside of an automatic - the car can choose what ratio it wants and unless you signal your intentions the older Mk3 prefers to keep the rpm low.

On a cvt how do you kick it out of Atkinson mode, can someone please explain Atkinson mode. Thank you.

As someone else said, I find a quick pull or two on the left paddle much more responsive than the accelerator pedal when wanting to kick it it out of Atkinson. I find flooring the accelerator slower and awkward, and have never noticed a notch.

andruec

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Re: Atkinson engine and CVT eg
« Reply #14 on: August 17, 2018, 03:48:08 PM »
After driving the 1.3 cvt for 25000 miles, I find there is ample power for my needs.  As an alternative to pushing the accelerator to the floor for immediate extra power in "D" mode, I find a couple of clicks on the left hand paddle change works well.  It reverts to lower revs as soon as you ease off, eg after overtaking.  I think the engine/transmission system is excellent, and overall is giving me about 52 mpg measured by fuel bought.

If you find the 1.3 suits you that's fine, others have different priorities. Your fuel consumption indicates the type of driver you are.
A sensible one ;)

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