[lahlooha]

HI,
sorry to ask a basic question but i just bought a used 2000 insight with 50k. its LMPG is 60. i drive 2 hours to work each way on 95 in virginia. the car is great doing 60 MPG on average. i am driving at speeds varrying from 65 to 75. my way to work is a little up hill ( barely) so the way back is a little easier.
it is a 5 speed manual

my questions are:

1- i thought that when we use the IMA it helps mileage, but the reality is that whenever the assist kicks in the MPG go down? why?

2- i read somewhere that if you get a full charge then the MPG will just rocket upwards, is this true? and why?

3- and will someone explain what is so special about lean burn and why sticks can do it but not cvt's.

thank you

 

[Foxpaw]

Simply enough, the mileage goes down when the assist kicks in because the assist kicks in to "relieve" the gas engine when it's under heavy load or acceleration - conditions which cause low mileage.

In theory, if your IMA battery pack was as full as the battery controller would allow, the engine wouldn't be using any of it's energy to charge the pack, which might give better mileage.

Lean burn uses a leaner air/fuel ratio, which is (considerably) more efficient but makes less power. However, because lean air/fuel ratios pollute a lot, (they make a lot of NOx) the extra pollutants are "stored" in the NOx canister and "purged" with a short period of "rich burn" after a period of lean burn. Although the rich burn is less efficient, there is still a net gain in fuel economy. I don't know why the standard can do it but not the automatic. The engines in the two cars are not identical - the difference is not only the type of transmission. The standard has higher compression and makes more horsepower. I believe that it probrably has higher compression because it has a different cylinder head. So, if I had to guess, I would guess that lean burn is related to the cylinder head in some way.

 

[Tim Maddux]

First, it is possible with proper pedal work to get ASST without a drastic drop in MPG. I have done exactly this in 3rd gear up a slight incline at 75mpg with about four bars of ASST. This requires a lot of subtle technique, and really only serves as an interesting side note.

Most of the time, ASST and high fuel consumption go together, because the driver is mashing the pedal to accelerate. This means low instantaneous MPG. It can decrease overall MPG if the driver is immediately decelerating again. I have found however that a fast acceleration followed by a long cruise results in stellar MPG. Plus, it's just more fun.

I have not seen significantly higher MPG when my battery pack is full compared to when it is not. Of course if the battery pack is empty then I see a lot more force-charging and that makes it harder to keep the car in lean burn mode.

I believe that Honda purposefully disabled lean burn mode on the CVT in order to get SULEV emissions rather than the ULEV emssions of the 5spd. I believe this because the greatest difference between the two categories is NOx.

Finally there is a lot of information (I'm too lazy to find the links right now) about the IMA and lean burn in the Encyclopedia on the main site.

 

[Insightful Trekker]

The other replies just about say it all. I can only reiterate and point by point reply.

1. IMA "helps" mileage from the auto stop standpoint which reduces or eliminates fuel at idle. Under most driving patterns the IMA "energy" is recovered from what would else be measured as a loss (charges on deceleration and braking). The IMA's primary function is to act like an electric "supercharger" giving extra "scoot" when needed for hard acceleration. This then allows a smaller ICE (internal combustion engine) to be used and tuned for maximum MPG (when driving "style" takes advantage of it).

According to this document:

http://www.osti.gov/bridge/product.bibl ... =3&start=0

pg. 2, Fig. 1 about 65% of _overall_ MPG performance is attributed to the IMA and its consequential benefits.

2. As the other posts indicate finding and holding on to the "lean burn" window _requires_ practice. And this window is narrow due to the physics of ICE and the chemistry of combustion. At speeds above 70 MPH (unless on a slight downhill) its basically unavailable.

3. Tim Maddux is correct, the CVT was designed for SULEV emissions. Lean burn conditions do not meet this stricter standard due to increased NOX (nitrogen oxides, a _major_ contributor to acid rain). Lean burn is so special in that when maintaining this condition ultimate MPG can be attained. See the Insight Central encyclopedia for further explanation.

Ultimate MPG driving requires driving by the MPG indicator and letting speed vary (within reason) by traffic and terrain.

HTH!

 

[ilusnforc]

1. The gas pedal still uses a throttle cable attached to a throttle body. The harder you press the pedal, the more gas it uses. I'm not sure how the IMA is regulated for acceleration, but it seems as if the pedal is like a potentiometer varying electric assist as you depress the pedal. (hope that explains it)

2. The only way I can see this to be true is that the electric motor puts a load on the gasoline engine to charge the battery (or else it uses regenerative braking) and when the battery is fully charged the engine doesn't have the extra load from the electric motor for charging. If you can drive on the highway with a fully charged IMA, you will get great gas mileage. If your battery is low, the IMA will force charge while you cruise to reach at least appx 3/4 charge (i think is about right) and your gas mileage will not be as good.

3. I think lean burn is partly because of the VTEC. From "How Stuff Works": VTEC (which stands for Variable Valve Timing and Lift Electronic Control) is an electronic and mechanical system in some Honda engines that allows the engine to effectively have multiple camshafts. As the engine moves into different rpm ranges, the engine's computer can activate alternate lobes on the camshaft and change the cam's timing. In this way, the engine gets the best features of low-speed and high-speed camshafts in the same engine.

You learn more every day you drive an Insight.

 

[Insightful Trekker]

<dusting off the cobwebs from this old post>

1. <snip> but it seems as if the pedal is like a potentiometer varying electric assist as you depress the pedal. (hope that explains it)

1. Nope. There have been several old "technical" posts (usually in the Mod & Tech forum) if your interested.

2. ... <snip> If your battery is low, the IMA will force charge while you cruise to reach at least appx 3/4 charge (i think is about right) and your gas mileage will not be as good.

2. True. When driving in the forced charge mode MPG is reduced. But lean burn _may_ still be "available". It's just that its "window" is smaller.

3. I think lean burn is partly because of the VTEC.

3. Sorry, no. VTEC and "lean-burn" are independent "systems". E.g. the Insight's predecessor the CRX Hf had "lean burn" (of sorts) without VTEC. But your explanation of VTEC is accurate :!:

 

[Dougie]

The VTEC kick in this car is quite noticeable, if you've been so into the hypermileage thing that you've never revved up your engine...

 

[ghillie]

lahlooa - the more technically accomplished posters might correct me but... I have noticed the same effect described in your first question. I think it is because the driving conditions that cause the assist to kick in usually also take the car out of lean burn (if you have been in it). You experience a surge of power from both the assist starting and the ICE coming out of lean burn. Petrol consumption increases because the car comes out of lean burn not because the assist comes on. Like you I was surprised to see the petrol usage increase just as assist came on - and I think this is the explanation

It is not necessary to have mashed the accelerator for this to happen. But if the conditions are right, extra load on the car will cause assist to start and lean burn to stop. Sometimes when assist starts there is no jump in petrol use and I think this is because the car was not in lean burn mode at the time. You can also tell the difference because there is no "surge" of power from just the assist.

I have not notice the effect referred to in your second question.

 

[Mike Dabrowski 2000]

On the standard Insight, the assist activation is controlled by the engine load. Assist will not turn on until the load is on the high side, usually at a MPG below 60MPG, and full assist is only available when this engine load is nearly the max that the engine can produce, then the assist will provide the extra torque to try to satisfy your request for power.
If the IMA were turned off, the small engine would not have the power to meed your needs, and you would probably have to downshift to get enough power to accelerate or hold your speed up a hill, yielding even lower MPG.
On the MIMA equipped Insights, you can control the assist and charging, independantly from the throttle control, and therefore do not need to step down so hard, and lower the MPG as much to accelerate or climb the hill, in fact you can accelerate and climb moderate hills without leaving lean burn if your batteries SOC is sufficient.
Balance the use of assist, and charge whenever the MPG effect for the charging will me minimized, and you can improve the MPG under many conditions.
:wink:

 

[eastender43]

So has anyone just disabled the ASSIST

and if so,were you able to get consistently better FC?

The clutch pedal switch should make this easy to do,right?

Just drive it in lean burn AMAP,and see what the average is ..

I'm SURE someone has done this......and I'll bet it didn't substantially improve overall FC.....

Otherwise,let's all yank/disable the IMA system(Not that simple,I know)

and get hyper mileage.....

 

[Mike Dabrowski 2000]

eastender43
MIMA works ask anyone that has it.
The increase comes from not using the brakes, instead charge to slow down.
Accelerating with more of the power coming from the electric, so the MPG hit from acceleration is minimized.
The batteries are charged at every oppertunity.

We will hopefully get to prove the MIMA electric priority system works to all skeptics at next years tour de sol. Nemystic won this past years contest with his MIMA equipped Insight.

 

[eastender43]

ok

Where did I say "MIMA doesn't work."?Maybe you missed my post title that ran into my first sentence of my last post....

I just was curious if anyone has done any reasonably extensive testing with the IMA disabled.....and what their results were.....

I am quite sure MIMA works.....no question there....I was trying to stick to the topic of how Assist affects overall FC....and therefore I thought the easiest way to determine that may be to just disable it,and see what happens.And it seems likely to me that one of our esteemed colleagues has probably already done just that....

Has anyone compared their mileage over a commute....with Assist/IMA functioning normally and then with Assist/Regen disabled?.....

The old KISS axiom,ya know.

 

[joecvt]

There have been several people that had the IMA light come on and
have to drive the car for awhile in this mode (just like disabling IMA)
and from what I remember, it seems most claim to lose about 10%
MPG (differs based on driving style).

JoeCVT - Just your average CVT owner