The smart MHD was released in 2008 proving that you could squeeze more economy out of a petrol smart fortwo 451. MHD stands for Micro Hybrid Drive but doesn't include a large battery like other hybrid cars. Instead the MHD uses stop-start technology which smart claim reduce fuel consumption by around 8-20%. The particular model we reviewed was the 'Limited 3' and is characterised as follows:
All 'Limited 3' models are all MHDs with a 71bhp engine.
The fabric seats have a 1970's style which has been welcomed by some, but seen as old fashioned by others.
The gearknob has a brown leather trim which is common throughout all of the limited edition models. At the front, you can see the green ECO button for enabling/disabling the MHD function.
The speedo includes the new horizontal fuel gauge but for all intents and purposes, it looks the same.
Upon starting the car, a yellow "ECO" LED illuminates on the right hand side of the dash. This indicates that the function is activated. The green "ECO" LED illuminates once the "ECO" function is ready. This is explained later.
After starting the car, the above lights will all go out except the yellow "ECO" light. If the MHD function is not wanted, pressing the ECO-OFF button will switch it off and the light will go out. Pressing the ECO button with activate it again.
After first starting the car, the car will continue to idle. The stop-start function will not activate until the green "ECO" LED illuminates. This will only happen once the engine is up to temperature, the battery is sufficiently charged and a whole host of other parameters give the system the OK!
When driving, we noticed that there was a considerable delay between using the gear change paddles and the car actually changing gear. Using the gear stick was not much better. In fact, leaving the car in automatic mode offered the smoothest gear change. This is contrary to the fortwo 450 where automatic mode was always 'lurchy' compared to manual gear changes.
The drive was very comfortable and you could be forgiven for thinking that the MHD is a regular petrol fortwo. However, when slowing down to a stop, the revs fall to 1000 before the engine cuts out. As the car does this, the green "ECO" light stays on. This shows the driver that the car is still on, even though the engine has stopped. The engine will remain like this whilst the brake is applied.
As soon as the brake pedal is released, the engine starts and is ready to pull away in the time it takes to move your right foot from the brake pedal to the accelerator. The speed and smooth sensation was very impressive.
Although we would see why it was necessary to keep your foot on the brake, this isn't really good driving practice. If the brakes are warm, keeping your brake pedal applied may lead to warping of the discs. However, the counter-argument is that you wouldn't buy an MHD if you were keen on enthusiastic driving.
For city use, we were impressed with the MHD although the engine could be a bit beefier when pulling away. Due to the 'stop-start' nature of the engine, turbo models were neve released. Here is a brief video of the MHD in action: