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Discussion Starter · #1 ·
I realised that when I am on 1st on 2nd gears (let's say when starting the car or when in slow traffic in the city) the mpg drops a lot. In other words, it goes from an average of 38 US mpg (6.1 l/km) to 15 US mpg (15 l/km) and I see little assistance from the IMA motor.

Actually, IMA motor seems to assist only when you exceed 3K rpm.

When in town, I've been driving like an old lady, with mild accelarations and brakings and I'm quite disappointed with this mpg.

Are there any tricks that I could use in order to improve this? Is there any way to force the IMA motor to assist more often?
 

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If you only get assist above 3k then there's something wrong. I wonder why you'd be using that many revs in 1st or 2nd in the city anyway (if that's what you meant). I almost never go over 2k in normal town driving and use the torque of the IMA.
The thing is, assist is more to do with load than revs - it could be that you're actually too light on the throttle and not demanding enough power to get assist.
Try using sport mode and using a little more pedal and see what you get then - should be lots of assist.
 

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I get IMA assist as I'm taking my foot off the clutch from a stop, so probably 1krpm-ish. Pretty much if I'm accelerating at all, I have 3 or 4 bars of assist.. Unless I'm in sport, then it's FULL assist :).

I occasionally play a game if no one else is on the road where I try to drive w/out ever getting assist. It's almost impossible for me. To make the car move, I have to pretty much push the pedal in enough to get about 3 bars assist. Otherwise it takes about 3 city blocks to get up to about 20mph if I push the pedal in so lightly I don't get assist.
 

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Discussion Starter · #4 ·
If you only get assist above 3k then there's something wrong. I wonder why you'd be using that many revs in 1st or 2nd in the city anyway (if that's what you meant). I almost never go over 2k in normal town driving and use the torque of the IMA.
The thing is, assist is more to do with load than revs - it could be that you're actually too light on the throttle and not demanding enough power to get assist.
Try using sport mode and using a little more pedal and see what you get then - should be lots of assist.
Going up to 3K is an old habit I have from my previous car. Sometimes, I need to go up a hill and only feel comfortable to shift up after 3K rpm. I always have the impression the car will choke if I try to shift up before, on a hill. Otherwise, it seldom goes above 2.5K.

In respect of the IMA assist, I do get some assist before 3k, but only one or two bars. I was under the impression the more assist you get, the less fuel you would spend. And you are right, I'm being too light on the throttle.

This weekend, I'll drive on the motorway and on sport mode with more pedal and see what happens. I still don't feel comfortable using sport mode in town. The car just gets too loose!
 

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It will pull pretty well from low revs in almost any gear let alone 1st & 2nd. The IMA gives a slug of torque low down so you need to adjust your driving style to benefit from it - it's almost like driving a diesel.
The shift indicators do a reasonable job of guiding your gear selection, it will tell you to shift down if the engine is labouring.
Not sure about more assist=less fuel - the two work in tandem. You want to accelerate reasonably quickly up to speed, get the benefit of the assist and then back off the throttle.
I know what you mean about Sport mode - it's almost too sensitive, especially if you've been in Econ.
 

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When you drive with the intentions of no assist or regen, that is when you are driving the most efficient.

The IMA assist isn't for fuel economy, it is there to provide a 'boost' to acceleration when needed. This was something that seems counterintuitive at first until you really think about it. If you are getting on the gas hard enough to induce assist, you are accelerating hard and therefore burning excess fuel. Problem is for 'average' people, they are so used to jackrabbit starts that driving like a turtle is mentally painful at first, their impatience gets the best of them.

If you were to browse through the king of fuel efficiency's posts (Wayne Gerdes) on his site CleanMPG, you will find this out.

Basically, the more you use assist, the more you have to give up efficiency to recharge that energy you spent. Since there is no system that there is no waste, a lot of energy is wasted in resistance in the transfer of that energy, both ways. So in essence, minimalizing assist means you are using less fuel to accelerate up to speed (lower rpm) and less energy needed to be replaced from regen.

A good target for acceleration is around 2k rpms or LESS. Not always practical; merging on highways, climbing hills/mountains, flow of traffic.
 

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The IMA motor and SI (spark-ignition) engine compliment each other in a hybrid car. Honda and Ferrari engines have a common characteristic: high rpm horsepower and low bottom end torque per engine displacement. You can't have it both ways, so with the IMA helping the bottom end, Honda can optimized the CR-Z valve timing for mid and high rpm performance even more than before, and the IMA eliminates the legendary Honda no bottom end torque, or 'gotta downshift' for acceleration notariety.
 

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Discussion Starter · #8 ·
When you drive with the intentions of no assist or regen, that is when you are driving the most efficient.

The IMA assist isn't for fuel economy, it is there to provide a 'boost' to acceleration when needed. This was something that seems counterintuitive at first until you really think about it. If you are getting on the gas hard enough to induce assist, you are accelerating hard and therefore burning excess fuel. Problem is for 'average' people, they are so used to jackrabbit starts that driving like a turtle is mentally painful at first, their impatience gets the best of them.

If you were to browse through the king of fuel efficiency's posts (Wayne Gerdes) on his site CleanMPG, you will find this out.

Basically, the more you use assist, the more you have to give up efficiency to recharge that energy you spent. Since there is no system that there is no waste, a lot of energy is wasted in resistance in the transfer of that energy, both ways. So in essence, minimalizing assist means you are using less fuel to accelerate up to speed (lower rpm) and less energy needed to be replaced from regen.

A good target for acceleration is around 2k rpms or LESS. Not always practical; merging on highways, climbing hills/mountains, flow of traffic.
Thank you for your elucidative post! I had the wrong idea about IMA assist. I thought it would assist you whenever you were accelerating, even in mild accelerations.

I drove the other day on the motorway with a considerable hill, and I could see the IMA assist working almost at its full capacity.

It's amazing how this car has changed my driving style. I have the eco guide on, almost all the time, and try to have only mild accelerations/decelerations according to the guide. Also, always try to shift up whenever indicated, so around 2k rpms. Therefore, I don't see the IMA assist that often.

But it's showing in my mpg!
 
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