Okay, I'll fully admit to being biased toward Hondas, but it seems to me that the Honda IMA system is *far* less prone to failures than an HSD system. Way fewer parts, sensors, connections, etc, etc, etc. I may pay for it in MPG now and then, but overall, I suspect the IMA will have a substantially lower life cycle cost than anything with an HSD system. Just common sense that with fewer things to go wrong, fewer things will go wrong.

Or am I wrong?



Butch

I certainly agree with you Butch. The Honda system seems more fault tolerant because it will start, run and reverse even with the main pack completely dead or off.

OTOH Belt and Pulley CVTs are not all that durable in the long run either. I'm not sure of the exact numbers but there have been reports of Honda CVT failures.

If I were buying a "non-manual" tranny I might favor HSD over Honda's CVT.

I've always preferred 5MT to 4AT or CVT, but my domestic partner can't crive a manual transmission and has no desire to learn how. ::sigh:: I don't think people should be given a driving license without knowing how to drive a stick shift.

Well, "fewer things" depends on where you're counting parts.

Yes, our (IMA) hybrid system itself is simpler, but we still have a conventional CVT transmission with a belt (which will have to be replaced during the life of the car), two variable pulleys, the stepping system, and assorted linkages.

HSD just has the ring gear, planetary gears, and their carrier. No variable ratios, nothing.

Also, the HSD's ICE is fairly normal (at least, for the TCH--those are Otto-cycle, right? Just the Prius is Atkinson?). The HCH2 has 5 valve rocker-arms per cylinder, with the ability to hydraulically switch between them or disconnect them entirely. Plus, our two spark plugs per cylinder, which normally fire separately, but sometimes together. Then there's the whole issue of the ICE turning our motor, so there's the sensor to coordinate the rotor position so you can apply power at the optimal point.

My point is that when you start adding up all the pieces, the new IMA systems are just as complex as the HSD systems. I don't think you can make a statement about which one would be more prone to failures by just looking at the systems. Only real-world numbers are gonna tell that story.

Would-be hypermiler

I can sympathize. I think I still have internal bleeding from last time mine tried.

Would-be hypermiler

While looking for the second planetary gear, I found a Toyota reference for the Camry that it is Atkinson but at a slightly higher charge compression ratio, 9.8 to 1 vs. 8 to 1. The expansion ratio is still high, which makes it Atkinson cycle.

As for complexity and trying to predict failure modes and rates, as a general rule, fewer parts are better. But in aviation, dual magnetos and sparkplugs gives us both a performance improvement and better in-flight reliability. When we do a magneto test, we see a 50 rpm drop in single magneto operation. Dual sparkplugs appears to improve engine performance.

Bob Wilson

Operation Iraqi Oil Freedom:

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There is another type, called a hydrolic hybrid, that UPS uses with their diesel delivery vans. I'm not sure how it works, but what I've read seems promising -- a 60% gain in fuel economy with no loss in drive power.

In Japan, the Yaris is available with a lightweight hybrid drive called IISS (intelligent idle stop start). So for a nominal fee, you can give your Japanese Yaris the ability to shut down and restart automatically at traffic lights.

This is probably part of the GM dual-mode transmission whose announcements make reference to having an automatic transmission mode . . . suggesting gear changes. Apparently the Toyota transaxles for the Camry, Highlander and Lexus have a second planetary gear configured for a fixed gear reduction on MG2, no shfting.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

The indications thus far are that both systems are essentially maintenance-free ( normal ICE maintenance ) and both systems are designed to last the 'life of the vehicle' ( about 250,000 ) without any significant costs.

This is Toyota's position in any event and I believe from the reliability reports on the HCH and Honda's reputation I'd say the same for Honda.

From reading this particular thread, I guess it seems like HSD has the more complicated electrical system (2 motors, more batteries), while the IMA has the more complicated ICE. I'm still amazed that both systems can do what they do as long and as reliably as they do it.

I can't wait to see what HSD-3 and IMA-3 will be like!