Bike engines

[DMZ]

Any thoughts on why Ariel hasn't gone for bike engines instead of hot hatch engines seeing as it's a motorbike brand at heart? It would create an even more unique driving experience and would also be more interesting aurally. People have obviously fitted such things to Caterhams with some success.

[John Scherrer]

If you want the engine to be limited to 210 bhp at a screaming 14,500 rpm then you could ... or ...

[Anon]

The problem with using bike engines in these types of cars is to get the sort of power we need i.e. 300bhp+ they have to be highly tuned and normally require more than one bike engine. Bike engines normally max out at 1500cc and around 200bhp or so. Cars are a lot heavier so to get the power needed normally requires a V8. This requires a complete manufacture of everything from the crankcase and up, which will increase costs dramatically. Also, the problem with this is you will need frequent engine rebuilds and these cost a lot.

The best thing Ariel did was use a commodity engine like a Honda in my view it's the same with the Ultima in that they picked Cheverolet engines due to low cost and high tune ability. Radical sports cars did this with the RXC and used the Ford EcoBoost v6 3.5 engine instead of their RPE V8 as found in the SR8. Their new road legal Rapture also uses a road spec Ford EcoBoost 2ltr that has been tuned. Radical tried their bike engine in the RXC but found it lacked the torque needed and it kept braking the drivetrain.

If you have ever driven a car with a single Hayabusa engine in it, the first thing you notice is the lack of drive on corner exit. I want poooowwwwer from my cars on corner exit...

[DMZ]

Great post, thanks. I wouldn't mind some screaming revs on the other hand. I guess in the earlier Atoms, the VTEC engines filled this brief. I've never really been a fan of turbo-charged engines. Which is naturally why I put a deposit on an Atom 4...

The naturally aspired engine in the Nomad, what is that like by comparison? Presumably more VTEC and high-end in nature vs the typical flat torque curve of a turbo-charged engine?

[phil4]

No, the Nomad has a 2.4 Honda engine which doesn't rev as high (7400), and doesn't sound the same as an Atom either. Mines SC so can't comment on torque curve though.

[thomas_fr]

Had a MK indy with a 1000cc and like 180bhp and an Atom with the K20A N/A with 220bhp,

they were totally different,

the MK needed to be used between 9k and 12k rpm on track, with the reliability of a bike engine on a heavier chassis used always at high RPM / high load,

where the atom was used between 5k and 8k for the same power output (not exactly, but you have the idea), in a lighter chassis than it was designed for,


At the end you **could** do same lap times, but you will not rebuild your K20, and you will broke/rebuild your bike engine every year

[cvjoint]

The V8 Atom did use two bike engines in a vee.

The K20 engines from Honda are in my view the best for the Atom concept. Nothing else comes close. You want reliability, power, compact footprint, availability of the best manual gearbox + bolt on sequential, and low cost? The Honda K has it all. If you like revs, it's got that too. A K20a can do 8,500rpm for thousands of miles fully stock, or bike levels of revs fully built without giving up torque.

You may see the appeal of a bike engine for something that is even lighter and has very restrictive aerodynamic needs, e.g. Radical. But then think of high performing time attack Normas, even those run Honda K and are likely faster than the Radicals in top trim.

There is actually one drawback though, and that is the wet sump in a high G application. I'm not sure other 4 cylinder engines have OEM dry sumps available.