GM's eAssist...

[Ecky]

This hybrid system could work, but not just as a bolt-on for people on this site.

Most hybrids' main benefit is from downsizing the engine close to the minimum required for cruising (or running Atkinson cycle) while maintaining reasonable power on reserve for passing. Simply bolting on an electric motor will not do this. However, electric assist could, for the average driver, prevent some degree of downshifting, or allow for lower gearing with the same drivability. Although I imagine most on this site would give up a bit of rate of acceleration for more economy, everyone has their limits, and that extra bit of torque could make "excessively" tall gearing more bearable.

On my Insight, electric assist makes available around 30% more torque in the rev-range I typically run. Because of this, I can keep up with traffic with the little 1L engine without ever revving over 2000rpm. It produces as much or more torque than Honda's 1.6-1.8L engines at these low RPMs.






The next biggest benefit is auto-stop, which many of us here do already with kill switches or key-off, but a hybrid system makes it a lot less trouble to use. In my Insight, I shift into neutral and tap a button, and the engine dies. When I'm ready for the engine to come back on, I tap that button again or throw it into gear and it springs to life silently, without putting any wear on a starter motor or clutch. I can't stress how luxurious it is for the engine to auto-stop at a redlight or when rolling down a hill and start itself back up without the need of reaching for the key or bump-starting it. More than any other feature, I'd miss this one the most if I ever went back to a non-hybrid gasoline vehicle.

Regenerative braking probably doesn't account for all that much in terms of economy for most of us here, but would for a more typical driver. For me, the biggest benefit is that I can go longer on a set of brake pads - I swapped out my factory pads just past 200k and they still had plenty of life in them.

Some smaller benefits: Most hybrid systems can more efficiently produce 12v than an alternator, even with a DC-DC converter, and for non-belt hybrids, get rid of some parasitic losses from belts, so you have close to the same benefits as an alternator delete without actually giving up your ability to charge the 12v battery.

[Stubby79]

This sounds familiar...
SpeedStart

[cRiPpLe_rOoStEr]

Even though eAssist doesn't provide full-hybrid capability, it's still a reasonable improvement that could have been more widespread nowadays.

[yesthatsteve]

I bought a '13 LaCrosse eAssist a week ago, and had my first fillup this morning. 30.88 overall, slightly above the EPA combined rating of 29. I'm noticing that this car is a real gem on the highway - I could probably beat the 36 EPA highway rating on a long trip. However, the weight makes acceleration a FE killer. With me and some gas, it's over 4100 pounds. When accelerating from a stop or at low speeds, the onboard instant FE readout can easily slip to the single digits unless I'm mindful of what I'm doing.

[sameb]

What if the system was plug-in? seems like an electric motor that came on out of corners on a twisty road or high speed freeway driving would save some gas.

[cRiPpLe_rOoStEr]

Originally Posted by sameb

What if the system was plug-in? seems like an electric motor that came on out of corners on a twisty road or high speed freeway driving would save some gas.

Since it's not exactly meant to be a full-hybrid, actually more related to a KERS, I'm not so sure if a plug-in setup would provide so much of an improvement on mileage.

[sameb]

I'm actually doing some analysis to answer this question. I'm in the middle of it, but the results so far suggest an increase of 22->31 mpg E85 or 26->37 depending on route. I thought I had the mpg calculation calibrated well enough, but the second dataset did not correlate with my measured average as well as the first one did, so I'll have to figure that out.

The two main parameters I'm looking at are the decrease in map when the electric motor is engaged, and the decrease in gas motor rpms that is possible due to deceased power demand.

I'm more interested in plug-in because I do about half corners and hills and half flat and fast in my commute. I hardly use the brakes, but there is a fair amount of compression braking. I haven't yet figured anything to model the potential for regen, but I think it's pretty minimal in this application.

[yesthatsteve]

With limited regen, a plug-in could be the solution. My LaCrosse seems to go into regen mode every time my foot leaves the accelerator, unless I coast in neutral. The touch screen and DIC both have an optional display that shows current flow - toward the wheels when the generator's engaged, and toward the batteries in regen. My DIC looks like this one; touchscreen is larger:



I see the biggest benefit of the eAssist system on the highway, where it keeps me in TC lockup. I can both hear and feel (slightly) the generator kick in at speed.

I'm sure it helps at lower speed, as well, but that car is so heavy and takes quite a bit of effort to motivate it from a dead stop. The DIC instant mpg readout is dismal in those circumstances, but it would probably be a fair bit worse without the eAssist.

[sameb]

Thanks for the pic. I figured it would go into regen when you take the foot off the gas, but it seems like the energy you can recover is very hampered by the compression braking. I'm thinking of my civic, it probably helps more in the heavier buick. I think the variable valve timing could be used to help with your car as well to relieve some of the compression. Does your display say what the regen power is?

[yesthatsteve]

No specific indication of power amounts - the battery icon on the right has six segments showing how much of the total battery capacity is available, and that's it.

I suspect you're right that the weight of the Buick helps overcome some of the forces of compression braking. Much of my commute has enough traffic to minimize the benefits of coasting in neutral, so I get a fair amount of regen.