2009 Mhd - Page 2 - Smart Car of America Forums : Smart Car Forum

mdfortwoguy · 04-02-2008, 08:07 AM

Eh, it doesn't interest me in the least. More wear and tear to save 63 cents/hour of idling... no sale here.

Krodista · 04-02-2008, 08:54 AM

is 63 cents per hour of idiling something you made up for argument sake, or is it a sourced number by the manufacturer? Has wear and tear been established to compare a car sitting and idling compared to a car turning off and on at intersections? I assume there is wear and tear to be involved with the engine for sitting in stop go traffic and also for being started and stopped. My real concern is the function of things like the A/C and radio when the MHD comes into play.

Fredvon4 · 04-02-2008, 08:56 AM

MHD is a scheme to have a MOTOR generator as both the starter motor and the generator to recharge the battery. On a MHD there is no traditional starter motor. The car is designed to shut off the motor after xxx period of idle time. The MHD will apply reverse electrical load to rapidly stop the motor in fewer then XX revolutions. The system then detects brake release and instantly restarts the motor.

Those of us in some areas of the country where the commute has few stop lights will never see any benefit.

But folks in WDC (as an example) where a major intersection can have wait intervals of 3 to 7 minutes before a light change might eventually see some benefit.... but I doubt the benifit is in fuel economy...it is really all about making the car compete in a lower average CO2 scale....

I do not want this complicated system on what is already a econo box with too many computers.... my 0.02c YMMV

2mutch · 04-02-2008, 08:59 AM

Be sure to read through this earlier thread on the MHD for more discussion points and info:

smart MHD - welcomed in US or not?

- FRED "2 MUTCH"
Is it a car? Is it a mind set? It's BOTH!

knutliott · 04-02-2008, 09:09 AM

Also note that the early mileage reports for the MHD aren't a significant increase over the gas smart. As I recall, it's only 10-15% which really isn't that great for a hybrid system.

Krodista · 04-02-2008, 10:17 AM

its not a hybrid system, just pretend hybrid isnt even in the name because it might as well not be. Depending on the price to have MHD in a smart it may be worth it for the extra 10-15% improvement in mileage. Never idiling in heavy traffic does sound like an advantage, but having to engage the break the entire time to do so sounds like a bit of a pain. With so many computers and fuses already on every modern vehicle out there...what is one more gismo that we wont be able to fix on our own? Long ago were the days when cars could all be worked on with ease without needing a computer to figure out where the issue lied. I wouldnt be suprised if more car companies began to come out with gizmos like these to save a bit more fuel.

mdfortwoguy · 04-02-2008, 10:15 PM

Quote:

Originally Posted by Krodista

is 63 cents per hour of idiling something you made up for argument sake, or is it a sourced number by the manufacturer? Has wear and tear been established to compare a car sitting and idling compared to a car turning off and on at intersections? I assume there is wear and tear to be involved with the engine for sitting in stop go traffic and also for being started and stopped. My real concern is the function of things like the A/C and radio when the MHD comes into play.

Read post #7 in this thread. That is where the figures came from.

mdfortwoguy · 04-02-2008, 10:19 PM

Quote:

Originally Posted by Fredvon4

Those of us in some areas of the country where the commute has few stop lights will never see any benefit.

But folks in WDC (as an example) where a major intersection can have wait intervals of 3 to 7 minutes before a light change might eventually see some benefit.... but I doubt the benifit is in fuel economy...it is really all about making the car compete in a lower average CO2 scale....

Bingo.

My commute contains 4.3 miles of solid stop and go driving. Stop and go meaning rolling 3 or 4 car lengths and then stopping, over and over and over. It is murderous on a clutch... I can't imagine what a year's worth of this would be like for the engine.

Krodista · 04-03-2008, 06:25 AM

mdfortwoguy. Stop and go traffic is already bad for an engine. What I am saying is that without real figures and evaluations all of this make believe "63 cents" saved and assumptions that it would be worse for the engine to turn on and off as apposed to idling is pointless posting. For all we know it could just as likely be better for the engine to turn on and off. Until they have done some long term tests on it there will be no real data (which is more than imagining and assuming).

mdfortwoguy · 04-03-2008, 10:13 AM

Okay, I have some background in the automotive engineering field - so I do have a bit of a leg to stand on here.

Firstly, having an engine sit for an undetermined amount of time is going to allow the oil pressure to bleed off, hence a potentially dry first stroke or two of the pistons, top end, etc. Add to this, if this thing richens the fuel supply on a start, you are going to have a burst of unburned hydrocarbons come flying out the tailpipe... less CO2, more HCs...

I'd be curious to see the emissions numbers for this compared to a regular powertrain.

A normal engine in stop and go traffic gets a constant oil supply, keeps its coolant temperature and the catalytic converter warm, can maintain closed loop status - reading from all sensors instead of plugging in block values to attempt to run smoothly and cleanly. Granted, all of these are not going to fall off in quick stop and go traffic turn offs, but there are a lot of things that could be affected.