Supercharged NSU Straight 8 Trike Engine from Two Inline 4 Cylinder Auto Engines

Supercharged NSU Straight 8 from 2 inline 4s

Supercharged NSU Straight 8 from 2 inline 4s

Several builders have taken the route of joining engines into a V configuration but Chris Ireland, editor of Brit Chopper magazine, sent me this photo of his just completed straight 8. The 6 month build is the combination of 2 1200cc NSU air cooled auto engines, joined end to end with the cranks running 90 degrees apart for that V8 sound and power delivery. He also attached a GMC supercharger for good measure. The distributor is a Rover unit chain driven from the end of the overhead cam..

The engine is slated for installation into a trike, which is the next part of the build, but, this could be used in all sorts of interesting things, limited only by imagination. Yes it's long and heavy, but it's very cool, too. Properly cleaned, painted and polished, it would really catch a motorhead's eye, actually, it already does. I like it!

Link: Brit Chopper


  1. JR says

    Holy crap! Looks like its straight from a bomber or something :)

    I have actually been doing some research about straight 8’s lately. I wonder why they died out. I know they are long, but so are straight 6’s. And aren’t they naturally balanced? Wouldn’t they make a metric crap tonne of torque?

  2. David says

    when they were being built the bottom ends were no match for the torque. I dont know of anyone that has tried to do a modern one. One of the first cars I drug home was a buick straight 8 the transmission made sure you could do know harm to the motor.

  3. nortley says

    Vittorio Jano did this very thing for Alfa Romeo in the 1930s – ok, it was designed from the start to be a 2 piece straight 8 – and it put a lot of hardware in Alfa’s trophy case.

  4. anon says

    JR, The longer a crank (or camshaft) gets, the more problems you have with torsional vibration. this why twin crank (geared together) straight 8’s came about. But the packaging issues (as you note, the length – not to mention the height if you don’t tilt them [i.e. slant six]) are probably why you don’t see Straight-8’s anymore. Cars just don’t have long thin hoods like that anymore.

    (For the record, I’m a huge fan of BMW’s straight sixes)

  5. JR says

    Good points Anon. This looks as if the two engines are coupled together.

    I would love to see something like this in one of those Morgan Aero’s or a (possibly stretched a bit) Caterham.

    How about the sound? Do they combine the exhausts?

  6. ScotDuke says

    The Bugatti racing cars of the 1920s and 1930s also used straight eights and dominated up until the mid-late 1930s when the German Mercedes and Auto Union racers came to the fore.
    The NSU 1200 engine has been used to power a motorcycle, the Munch Mammut (Mammoth), which has been built in low numbers since the 70s and has been updated a few times in that period.
    This straight eight isn’t a bad idea, though to make it more compact surely it’d be better to have a single crank and have it as proper V8 surely? It’d take a little more engineering work but the engine would be more compact and more suitable for use in a motorcycle.

  7. ScotDuke says

    I forgot to mention – engines joined crank to crank have been built since the 1930s. An Italian floatplane racer is the earliest example I can think of. The German Heinkel HE177 bomber of WWII also used coupled engines. However, neither of these aircraft was known for reliability (the Heinkel had a bad reputation for sudden engine fires and the Italian floatplane missed out on the Schneider trophy air-race due to reliability issues and the British Supermarine SR6 won as a result). The history of coupled engines joined crank to crank hasn’t exactly been a model of success. perhaps the best example I can think of is the huge 24 cylinder Caterpillar 3524 diesel (two 3512s joined end to end), which was used to power the firm’s mighty 797 and 797B mining truck variants. But then Caterpillar put in a lot of electronics to ensure that the engine worked. The firm has now switched to the new C175 series, the biggest of which is a V20 incidentally. maybe I got a bit off track, but my point is that engines joined crank to crank have a troubled history.

  8. Ceolwulf says

    That is seriously cool. I’m a big fan of straight eights anyway so I suppose I would say so.

    The title seems to throw together a collection of words expressly designed to cause mass confusion. That is also cool.

    I have to wonder. Why go to all that effort to make something so extraordinary and then design it to sound like every other 8-cyl out there?

  9. FREEMAN says

    I sure hope they don’t cover this beauty up with some body panels when it goes in that trike of theirs. That would be sad.

  10. Odiekokee says

    @JR, No, I-8 engines are not fully dynamically balanced. I-6, V-12, F-6 (or 180° V, if you want to see it that way) , and properly configured Boxer-8 (also a 180° opposed) engines all carry primary and secondary dynamic balance without any secondary balance shafts or other non-productive mechanical means.

  11. Slothie says

    @FREEMAN – No, I know Chris Ireland, and this engine will be on display! Follow duncan Moore’s link to the build details – there’s links there to some video of it running.

  12. anon says

    This thread got me thinking… I wonder why you don’t see more hot-rods with straight 8’s? A stretched hood, with no side panels… would be pretty sweet if everything was polished/ plated/ properly presented. Maybe it’s just availability of the engines? After all, this guy’s building his own.

  13. Hawk says

    I well remember the Buick Straight 8s … and the two speed transmission behind it. Gave rise to the name “Slush Pump.” But yes, it did protect the crank from torsional problems. A few years later a local racer put a 4 cylinder Mercury Outboard (2 stroke) in a Cooper Formula Jr (I think). The noise (out of 4 megaphones) was incredible …. until the crank broke. It seemed that the thing just needed its “power end” in water.

    In this layout, I’d suspect much better success by taking the drive from a gear between the two engines thus reducing the torsional loads on the rear crank.

    Another issue is cooling. Air cooled engines are not known for variable high output and hanging a blower onto it will only increase the need for bigger fans. Sure like to see the dyno results though …..

  14. OMMAG says

    I think it’s pretty cool. How people find the time to take on projects like this is beyond me….

    BTW – Have a friend with a 39 Packard … The straight 8 went around North America two times …. welll almost two times …. the crank broke on both extended trips.

    Interestingly enough he had the crank repaired/ rebuillt two times…. the last one was fabricated by some machine shop genius.

    Absolutely amazing.

  15. todd says

    My dad has had success drag racing Chrysler Imperial straight eights in the old days (nine main bearings). If you used a Desoto eight, you’d need to fit the harmonic balancer from the Chrysler motor to keep the crank together. He’s still got a bunch of the cars and the engines laying around. They’re extremely too heavy for motorcycle use.


  16. Paulinator says

    I like what this guy’s doin. Great shed!!!

    Does anyone remember a pre-unit Bonnie straight 4??? A really clean splice of two 650s. I read an article on it in the late eighties.

  17. Phoenix827 says

    Just plain cool !!! As I remember from auto mechanics classes the best balanced engines actually had an odd number of cylinders. The main reason the straight engines have gone away is weight and size. Auto makers needed to get lighter and more compact to fit in smaller, lighter bodies. Straight engines make tons of torgue, but its a trade off for weight. Ford ran straight 6’s in their F600’s for ages. Weight wasn’t as much an issue as torgue and reliability. I personally love straight engines, especially fond of Ford 300’s. I look forward to updates on that trike.

  18. klootviool says

    The straight-8 engine died, because the V8 engine was better in alot of respects. It had higher outputs and its weight was alot less than the straight-8. They quit building straight-8 engines around the 1940s, although there were still manufactories that were building these engines.