Hi All,

I went over the various documents / website info about honda's i-vtec + ima engine (i.e. the engine in the 2006 civic hybrid). The specific page is here: http://world.honda.com/news/2005/4050705_b.html

Some things to note:

- it is designed to assist the engine with the electric motor when starting from a still position. This explains why we are having a hard time starting with no assist.
- In the low to mid engine speed, the gas engine runs in LO-VT (low speed valve timing) which is said to improve fuel efficiency. This is what we want.

So, several interseting things. In low to mid engine speed it runs in LO-VT. Can we say from 0-3000 RPM would be considered low to mid (if 6000 is considered very close to red and therefore, max)?

Again, from the same site, to maximize the output of the electric engine, we would need to run at around 2000 RPM.

Which leads to the following scenarios:

1- To try and be fuel efficient (LO-VT) without assist, one would need to accelerate without assist AND have less than 3000 RPM (assuming 3000RPM is considered 'mid').
2- To try and maximize the use of the assist when accelerating, one would need to accelerate at 2000RPM.

Therefore, we can try the following:

To try scenario 1, we could use the 'S' position on the transmission. This (from my very limited usage) seems to reduce the use of assist AND allow you to stay below 3000 for acceleration (stay in LO-VT).

To try scenario 2, we simply drive as we normally do but try to hit exactly (or come very close to) 2000RPM when accelerating from a stop.

I myself will be trying these and would love to hear from others.

Thanks,
Stephane.

 

Good thinking, Stephane, though I seem to recall 3500 being the limit for the fuel-economy mode... but I think it was dependent on something else as well. Load maybe? That was for the regular '06 Civics but I assume the hybrid's engine works the same way.

 

Hi CG,

so, 3000-3500RPM seems like a good upper limit for our test. BTW, how did your tests with the 'S' position go?

BTW, I should have specified that these test should be geared towards city driving first and then, highway driving. Although, from my understanding, the 'S' position is not suitable for highways, but I could be wrong.

Thanks,
Stephane.

 

This article has some more detailed info, and the operation range diagram shows that the high-speed cams engage at 3500 RPM.

It's a 4-page article that covers all of the Civic powertrains, but the links at the bottom of page 2 are missing, so keep that in mind when you are reading it

 

Hi NASA,

thanks for the link! Very interesting info in there. The operating range is for the 1.8l VTEC engine (the hybrid has the 1.3l version), I guess for our purposes, it is safe to assume that the operating ranges are the same. So, let's make that a 3500 RPM upper limit.

Thanks,
Stephane.