MHD switching not restarting uphill

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Permalink Reply by Ian Pellant on June 14, 2011 at 8:20pm

Hi,

I can see how the problem can easily occur... in fact by my understanding, it would be hard to avoid. (I don't have MHD on my 2008 pulse; have only test driven MHD stopping on level roads).

The inherent problem is in timing the engine restart with the hill assist locking the transmission and only having a second or two to start before the hill assist lets off... and back you go.

I have driven manual shift transmissions for decades. I have the Auto option in my 4-2 but rarely use it... prefering manual control. In a traditional stick shift, best practice is to put the transmission into Neutral and apply the handbrake when stopped at traffic lights, o hills, etc. Reason - it avoids wear on the clutch and if something "bad" happens (such as being rear-ended when stopped), you are unlikely to move until you release the handbrake. I use this driving technique in the smart... ok... I'm getting long in the tooth.

Try to test drive a new MHD at a dealership and do the hill stop... if it's ok; then your car is out of tune.

Meanwhiles: if you have to stop on an uphill and the MHD stops the engine... apply the handbrake and take your foot off the brake pedal. Engine should restart (?). Options would now be: turn off the ECO / MHD then put your foot on the brake pedal; (engine should stay on); then release the handbrake (with foot still on the brake) and hill assist should work ok. Other option is to flip the transmision into N and then restart the engine with foot still down on the brake pedal.

My sneaking suspicion is that if I had MHD, I would only ever turn it on when driving in stop-start traffic on flat roads.

I bought the turbo engine, it didn't have the MHD as an option (turbos do not like to be turned off and on a lot due to heat and lubrication drying out and casusing turbo wear). As a result, my fuel consumption in stopped traffic is certainly 30% higher than when highway cruising, so MHD sure does save fuel (in traffic)... it's an option... turn it off if it causes problems. (On the Aussie smart pulse I test drove, it had a big button to switch MHD on and off.. I assume that button is standard on all MHD equipped smarts.)

Cheers,

Ian

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Permalink Reply by Fathi Antaki on June 15, 2011 at 1:06pm

Thanks Ian for all the tips; the problem seems to be on all MHDs uphill...

I will follow your advise and switch mhd off when uphill...

And yes stick shift driving is a completely different world, i agree ;)

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