It’s often hard to evaluate something brand new until we compare it to something we already know, … or think we know. Last week, you saw the video of the new KMV4 engine running on a dynamometer and some specs were listed on the Motus website. Is it light, compact, powerful and versatile, or heavy, huge, under powered and limited in potential applications? Is it well engineered or primitive? While many of you have opinions, I think you could use a little more information and maybe a reference for comparison.
What better way to get more information than to go to the source, so we did, and I can tell you a little inside info you haven’t heard yet, and to help you put that into perspective, I’ll do a little comparison with something else you may have heard about last week.
A few days ago, BMW released the details of their all new BMW K1600. It certainly seems to be an impressive motorcycle and quite a few websites were quick to present the new touring bike as one more example of Bavarian engineering with a smooth, powerful, light and compact 6 cylinder engine. How does everyone know it’s all of those things? BMW said so. Hmm … well, let’s compare.
The BMW 6 and the KMV4 are so totally different, one the product of refined German engineering and the other an upstart hot rod V4 from the USA, it’s obviously foolish to compare the two engines, how could we? Well, … I have a better question, why don’t we? And now that we have more detailed information, you might see the KMV4 in a new light.
Using BMW’s own specs as detailed on their website, I began to notice quite a few interesting similarities and, even more interesting, when there is a difference, it usually, tilts in favor of the little upstart V4.
Let’s start out with some obvious points, displacement is virtually the same, 1649cc for the BMW, 1645cc for the KMV4.
The KMV4, obviously, has 2 fewer cylinders, a single cam in the valley versus dual overhead cams and 2 versus 4 valves per cylinder so there are fewer moving parts. Advantage KMV4.
Weight of the BMW engine as provided by BMW is 102.6 kilograms or 226.19 pounds. I expect you’ll hear praise for how light the BMW engine is. The weight of the entire KMV4 powertrain, including gearbox, is designed to be under 200 pounds, it’s not yet final but it looks to be easily on target. Advantage KMV4.
Engine width: BMW: 560mm or 22.047 inches, KMV4: 492mm or 19.37 inches. Remember, the BMW engine is described on their website as compact. Yes, that’s in comparison to other 6 cylinder engines but you will also likely hear comments praising BMW for their achievement in building a relatively narrow engine. Advantage KMV4.
Torque: BMW 175 Nm or 129 foot pounds, KMV4 162 Nm or 119 foot pounds. Advantage BMW.
Now, this is interesting. All of the horsepower figures you’ve seen so far on the KMV4 have been target figures and listed on the website as 140 minimum, however, as the video clearly shows, the KMV4 has been on the dynamometer. So what did The Kneeslider find out for you?
BMW 160 horsepower, KMV4 161 horsepower. The BMW 6 makes a little less horsepower than the KMV4 and it has 6 cylinders, dual overhead cams and 4 valves per cylinder. The pushrod, 2 valve V4 does more. Advantage KMV4.
So, just to recap, compared to the BMW, for the same displacement, the KMV4 has fewer cylinders, fewer moving parts, it’s narrower, lighter and makes more power. Cool!
Gearheads, being what they are, look at any engine and wonder what they might do to increase performance. The BMW, in order to achieve its compact size, is built with a very small distance between cylinders so no one is going to be over boring the 6 to increase displacement. The KMV4, on the other hand, was specifically designed with extra material around the cylinder bores. This is a hot rod small block, after all. (Hey, Vern, why don’t we just bore this sucker out a little bit?) Why not, indeed? Instead of a 1650, how about an 1850?
There have been some comments about the 75 degree crank. Motus brought in Geoff Goddard on the crank design and balancing. Goddard designed the Ford-Cosworth DFV, an extremely successful Formula 1 engine. Motus wanted a big bang, odd firing order, for that cool American small block sound to give it a little character (Yes, I like it!). So the crank is 75 degrees, mainly because he said so. And since he’s also worked with Ducati (the Desmosedici V4 crank throws are 72 degrees) they felt he knew what he was talking about. The sound would not have been much different with 90 degree throws, but the 75 also allowed Motus to cancel out another secondary vibration.
The BMW 6 is referred to as very smooth, the KMV4 with a 90 degree V has full primary balance and 2 counter-rotating balance shafts cancel most all secondary imbalances. In other words, the street version of this engine will also be very smooth. For competition, remove those balance shafts and immediately increase power.
Speaking of competition, as already noted, if you need more power, besides boring the cylinders and removing balance shafts, you can increase stroke, replace stainless valves with larger titanium units, increase compression, replace hydraulic lifters with solids, which bumps the redline and all of this basic hot rodding is before any forced induction. Another point, those roller hydraulic lifters are a production GM part, keeps costs down and parts available while maintaining a respectable redline of 8000 rpm. There are several other GM parts in there, too, cam bearings, ignition coil, injectors and more. In other words, parts are everywhere.
The KMV4 was engineered by the same guys who worked for decades at GM Racing, it shouldn’t be any surprise that removing the bevel drive gearbox and installing an automotive type transmission would make this a sweet little engine for some 4 wheel racer. Depending on configurations, 230 horsepower is pretty straightforward, perhaps as much as 300 with a bit more work. Coming standard in a mild state of tune it’s still quite healthy and yet there’s plenty of room to hot rod this little small block.
You don’t need some exotic engine configuration for modern, reliable, high performance. It reminds me of an old comparison of top speed in a car mag some years back, Car and Driver I think. They wanted to find out what race cars were actually the fastest and had a 3 way test with an open wheel racer, an F1 car I think, a LeMans racer, Porsche, if I remember correctly, and a NASCAR stocker. The various teams showed up, the F1 car did OK. The Porsche was accompanied by a team of technicians who hovered over it and tweaked and tuned everything and set down a respectable speed. Then the NASCAR boys showed up, rolled the car out of the trailer, fired it up and blew them all away. So much for all of that finely tuned European technology, welcome to America.
Are you beginning to see what this engine is? Anyone comfortable with hot rodding a small block Chevy will be right at home here. For those making comments about how Motus needs an engine for multiple purposes, what exactly do you think this is? This is a small block with loads of hot rod potential capable of being fitted into all manner of vehicles and garage projects that you ride, drive, float or fly. It’s a clean engine with the modern GDI fueling necessary to meet current and future regulations, too. If Motus does this right, this could be one amazing little beast, and by the way, it’s made in the USA.
Related: KMV4 engine video