Sorry if this has been circulated before, but very cool to see the justa has the same engine (albeit detuned) as the new BMW i8.

http://jalopnik.com/did-you-know-tha...are-1500536781


Just listen to that car roar! https://www.youtube.com/watch?v=zkgXnEQvLk8

 

The three cylinder is really cool motor. I just love the technology. That's why I got the three cylinder. I just love the way it sounds. I want to remove the the rear muffler and then see how it sounds. I bet it will sound fantastic. Also I think it's cool to have the same motor (detuned) that's in a 125k BMW i8

 

Oh I knew this little 3 cylinder 'justa' would be destined for aftermarket greatness in a couple of years.... This 3 cylinder engine is awesome and it will growl!!

 

For some reason in that YouTube sound clip link it sounds digital. Like a sound simulator. Maybe it's just that particular sound clip.

 

For me the most important point regarding the B38 triple is that it is an undersquare engine. The stroke is almost 20% greater than the bore, which is not what most of us are accustomed to in a small displacement high performance engines. Here are the dimensions for the triple... Bore: 82 mm / 3.23 in, and Stroke: 94.6 mm / 3.72 in


The Japanese motorcycles have for years been oversquare, as have F1 engines since the 50s. They make power through high RPM, and provide relatively little torque because the stroke is modest, and therefore the length of the lever which is actually twisting the crankshaft (the throw of the crank journal) is pretty small. For example the Honda CBR engine released in 2009 (with 1 litre of displacement) has a bore and stroke of 2.95 in × 2.22 in. This motor makes about 150 HP, but has to spin to 12,000 rpm to reach that output. It has very little torque, making only about 75 ft/lbs at around 8,000 RPM.

In contrast, if I look at the Harley Davidson engines, which are justly regarded as torque monsters, the opposite approach is taken. THe engine in the 2013 Wide Glide has a bore of 3.88" but a massive stroke of 4.38". This is an undersquare engine, rated at about 100 ft/lb of torque at only 3,000 rpm. Amusingly, HD does not even state what the HP number is for this engine (at least not on the source I am using).

The R53 engine which I loved in the past peaked at around 162 ft/lb, and was rated at about 170 HP (at high RPM). The B38 engine which I am about to love actually has MORE torque than the "S" model did, based on the area beneath the curve, by which I mean that from 1,800 to 5,800 RPM the B38 has higher average torque than the "S" model did. Yet the B38 is rated at about 138 HP!

The reason for this is hiding in the realities (and mathematics) of horsepower and torque.

The bottom line is that I do believe that the F56 is going to be one hell of an effective G Street autocross car, because the torque curve will be not only greater than the DS R53, but also more equitably distributed across the rev range actually used in competition.

Also, I can only conclude that the B38 Mini application is significantly under-stressed which gives me hope for the mechanical longevity of the design. I think this due to the rather eye-popping numbers cited in the article which the OP linked at the start of this thread.

Cheers,

Charlie

 

You can find other clips as well, but the video claims the noise generator is turned off. The noise is pretty much the same listening from outside the car as well.

 

I can't freaking wait to get a better exhaust and CAI on my Cooper. It's going to sound so damn good.

 

Spot on, even though I opted for the S. This engine will be THE benchmark for power and efficiency and seriously made the "justa" an amazing buy.

One of the let downs of the S is how useless the upper rev bands of the car are. Power comes in early and strong but peaks under 4000 rpm. Almost feels like they focused engineering efforts on the S around detuning the car as there is GOBS of potential there. I went with the S because it will be the engine they offer the factory warrantied bolt ons for and I will be upgrading just as soon as they become available.

 

Yep - HERE is a seriously tuned R53 (which was competitive in STX) - note that even after the tune the torque is not all that impressive.

I am still waiting for a credible dyno chart for the B38.

Cheers,

Charlie

 

Oh i love reading threads like this!