OK... I've got 2,600 miles on my 07 HCH. I'm on my 6th tank of gas, and should hit 600 miles on this tank (hooray!). I'm learning to drive it better and better (first 2 tanks with my wife driving were in the low 400's, and the last 3 tanks with me driving were in the low 500's).

So, I have a (stupid?) question... what is the IMA 20hp motor actually supposed to be doing? I can easily get the HCH into EV-Assist mode (iFE pegged at 100 and 1-4 assist bars). However, when I'm in the EV-Assist mode, I notice no difference with 0 to 4 bars of IMA as far as maintaining speed. When I'm in the EV-Assist mode, the speed always drops. What I mean is, from a stoplight I get up to speed (say for this example 45 mph). I then kick in the EV-Assist to glide, but almost immediatly speed starts dropping - 44, 43, 42... whether I have 0 or 4 bars of assist. So when I get to 5mph below the speed limit, I have to get out of EV-Assist giving it gas to accelerate back up to 45 again. Can't the 20hp electric motor do enough to at least maintain your speed? Granted I live in an area in Sacramento, CA with slight gradients up and down in the roads (haven't found any truly flat road stretches). But unless I'm coming down from the hills from Auburn or Placerville with 2% - 7% downgrades, I always have to do P&G. So I just try to keep the EV-Assist at 0 bars (no assist, no regen) - why should I use assist when all it is doing is draining the battery! Or am I doing something wrong (or something wrong with the car) that the IMA is not doing what it is supposed to do?

Also, when accelerating from a stoplight/sign, the assist bars jump to 5 or more, and the iFE is down in the teens. I don't gun it from a light... I try to keep it under 1,500 RPM. And a few seconds after starting from a light, I let off the accelerator to get rid of the assist lights so the SoC doesn't get hit. Again, if the IMA is supposed to be helping, why does it not seem like it's helping?!?

Any feedback is appreciated... Thanks!

 

The electric motor actually IS assisting, as indicated by the 1-4 bars on the meter. However, 20 HP can't maintain speed on a 2,900 lb. car, even at low speeds. The assist is only slowing your rate of deceleration. This has value in extending your ability to coast with the mpg meter pegged at 100, but it won't let you cruise around town for free.

As for acceleration, I "gun it" from a stop to get the maximum electric assist. The electric motor is all torque, and torque (not horsepower) is what counts on acceleration. I find the assist meter maxes out with the tachometer at about 2,500 rpm.

Others prefer grandmotherly acceleration to maximize mpg, and they have a point. But I prefer not to p-o drivers behind me. We all have to make compromises in the real world. The bit of mpg I lose via rapid acceleration seems a fair price to pay. Anyway, I'm averaging 47.1 mpg on my 4th tank of gas, and 2,200 miles on the odometer. Can't wait until the engine breaks in completely!

 

The IMA can also help you (briefly) in high-output situations such as climbing hills. This can be demonstrated if you set the cruise control and climb a hill: the engine will rev very high to maintain the set speed but you'll see little (max 2-3 bars) or no assist; now do the same hill without the cruise set, holding the same speed, and your revs will be ~1000 rpm lower while your assist will be 4-5+ bars, supplying the torque that lets the CVT run a "higher" ratio (leading to lower engine revs). The torque really does make a difference in either how low the CVT can set engine revs, or how fast you accelerate. Of course, at max output climbing a hill, you have approximately two minutes of assist before the SOC drops to two bars. (Whereupon the computer more or less stops using it.)

And to put a finer point on 1stpik's explanation, it's possible the 20 horse motor could maintain low speeds if the engineers had decided to let it. But most people can't get more than 4 bars of assist in EV mode, or about half power, because the system isn't programmed to make more power available. Honda engineers are serious about the "A" in IMA -- it's assistive power, not primary power. The batteries won't stand up to the kind of beating they would take from sustained true EV operation. You'd have to double the number (and weight) of them and the warranty would suck.

Regarding acceleration: For awhile I was in the school of "use the electric torque for all it's worth." Lately I've been doing the grandma (1500 rpm) acceleration when it won't confound traffic, and the instant mpg don't drop below 40, and sometimes hover around 50. My sense is increasingly that the best way to improve my mileage is to worry less about the super-high instant mpg readings you can get by racing up to speed and then feathering, and worry more about keeping that gauge at or above 50 as often as possible.

Still, I'm skeptical of the school of thought that tries to stay out of the electric just to avoid regen losses. The electric is there for a reason, dudes, and tapping it often makes sense if you're in situations where you can avoid forced regen (hills, lots of start/stop, not much other electrical load from climate control, lights, etc.)

cheers --
Doug

 

The IMA is an assist power source. The engine itself if pretty anemic... as can be proven when you climb a huge grade and your power bars go down to one... and you lose all the electric assist.

The thought process is that a smaller engine (with better mileage and lower emissions) can be used and with the assist, it performs as well as a car with a larger (more wasteful) engine.

Since the motor assist is basically providing "free" power (that would normally be wasted in heat from braking), it's a great deal!

 

Well IMA definitely does help my coasts and glides go longer. Based on the speed and if I manage to be on an absolutely flat road ... i can even accelerate a little bit using assist.

 

I think you also need to be aware that 4 bars of assist is less than 5 hp. You only get full 20 hp assist during acceleration or hill climb, at full throttle.

Around 10 hp would be enough to maintain speed at 45 mph.

 

Ahh! the nightmares are coming back!! Yeah, I don't how times its happened when I climb a very long grade, bring my SOC to the bottom, then when it's time to go down the other side there is a slow poke (yes, there is actaully a bad time to go slow). At first its ok, I just charge up my battery, but then my SOC is full and it won't accept any more charge, and then I have to waste all that lovely momentum, I can just feel it all going down the toilet..Finally, we're at the bottom and, what do you know, another steep hill/mountain!! And I have no speed because the person in front of me just wasted all of it. So much for DWL. Repeat process.

Sorry for the rant!

 

I think its kind of like a weekly allowance - you can blow it all on stuff you like on monday or just spend a little each day for something you may need. If you dont spend it all, its still in the bank.