smart MHD - welcomed in US or not?

[jonnysan]

Yeah, I would think that with so many of those cycles, as MDguy pointed out, one would reach a point of diminishing returns (more electrical losses due to so many restarts requiring higher amperages to kick engine over) and the losses would outweight the gains. In less severe driving situations where there was not so much stop and go, perhaps then the MHD would show positive gains....time will tell as they do more testing of the MHD smart.
I wish they'd quit fooling around with *inbetween* technologies and just get to the chase and make a PHEV.....

[mdfortwoguy]

Not only that, but how is this thing ever going to enter closed loop mode? With all of that starting and stopping, the catalytic converter has to lose temperature. Add to that that unless this is a lean burn engine, the ECM is most likely going to be giving it a burst of rich fuel on each start to aid in starting. I'd be very curious to see the emissions numbers for the MHD versus the standard fortwo.

Add to that that it does take it a second to get its thoughts together in automatic mode when you press the accelerator. Add the crank time on top of that, so you are up to a good 2 or 3 seconds response time. That my prevent you from getting t-boned by a red light runner, but around here that's going to result in a honk, and I wouldn't put it past some of these drivers to shove you off to a start.

I just think of all of the wear and tear, and the whole concept turns me cold, very cold. At least in a Prius or Civic or the like, the only time the engine is started by a starter motor is a cold start, and subsequent starts are performed by the power package.

[Old smart]

I see it more as a marketing tool than anything of great practicality. Somewhere it was said that it only gets 8%-10% better mileage under ideal conditions.

[spdickey]

The shut down restart cycle doesn't seem to hinder the millions of Toyota's Prius on the road today, including mine.

[Gortok]

BRING IT! PLEASE!


I hope it sells well. It could be the stepping stone to yet more "smarter" cars...

[mdfortwoguy]

Originally Posted by spdickey

The shut down restart cycle doesn't seem to hinder the millions of Toyota's Prius on the road today, including mine.

Which is what I was getting at by the starting via the power pack and not a traditional starter. With no power pack, the MHD is gong to be relying on the starter.

Also - isn't the Prius a lean burn engine?

[MarkB]

The MHD doesn't use a "standard starter" it uses an alternator/starter combo.

[JPaul]

A la place du démarreur habituel, la smart fortwo mhd utilise un générateur marche / arrêt qui exploite le plus efficacement possible les « phases de repos » du moteur. Dès que vous freinez jusqu’à atteindre une vitesse inférieure à 8 km/h, la technologie mhd coupe le moteur. Lorsque la circulation reprend, il vous suffit de relever le pied de la pédale de frein : le moteur redémarre immédiatement et vous pouvez poursuivre votre route. Avec le générateur marche / arrêt de la smart fortwo mhd, vous économisez jusqu’à 19 % de carburant [2], sans renoncer à la puissance moteur ou au confort. Ce système d’une grande simplicité ne nécessite aucune manipulation spécifique de la part du conducteur : vous profitez d’un confort sonore accru, d’économies de carburant et de réduisez vos émissions de CO2. Après tout, pourquoi consommer de l’essence quand vous ne roulez pas ?

Instead of a usual starter, the smart fortwo mhd uses a start/go generator that uses the "engine off" most efficiently. As soon as you brake below 5mph it cuts the engine. Once you lift your foot from the brake, the engine starts again immediately and you can drive on. With the stop/go generator, you can save up to 19% of fuel [2], without altering engine's power or confort. This very simple system doesn't require any specific driving technique from the driver: you're enjoying more noise confort, better mileage and less CO2. After all, why burn fuel when you're note moving?

[mdfortwoguy]

Hmm, my shoe tastes rather good right now.

At any rate, I still don't think it is anything that would interest me much.

[anthony94114]

I don't really know, but I think maybe the smart mhd utilizes the same scheme as BMWs, MINIs & Citroens- which have start/stop but no supplemental electric motors. So.. perhaps the technology isn't so challenging for the engine after all.