More daft questions...2.4 Engine

[PhilTimo]

I don't seem to be able to find much info on the 2.4 Engine?

Why did they change?
What are the differences? More torque at lower revs?
Your thoughts on the 2.4?

(Go easy as I've just bought one!)

[GraemeW]

Phil

I got the same engine. I did a bit of digging at the time because I had an option of the last K20 or the "new" K24. There is much debate earlier on the forum about this matter. In summary this is what I found/decided at the time:

• Ariel ran out of K20 engines in UK when Honda brought out a new Civic Type R in 2016, and imported K24 engines, which were used in the US version of the Civic Type R. It was a short run because they later started sourcing the K20 again from the US I think.

• Ariel did not publish any data in the UK for that engine in the Atom. I did some digging and found some data on the US Ariel site where they were using the K24 engine. I wrote it down somewhere and need to find it again.

• Essentially as you say the K24 has more torque lower down, and doesn't rev as high. Ariel told me there is a different map in the K24 for the atom compared with the Nomad. Atom bias for power and Nomad for torque

• I drove cars with each engine, charged and not charged. The purists will say the K20 engine is the best, and they would be correct. Marginally, IMHO, because whilst the high revving K20 really suits the character of the Atom, which is great on track it lacks the torque of the K24 which (again IMHO) makes the Atom a better drive on the road. The torque figures of the NA K24 are close to the Charged K20. I just love my charged K24, (like yours). There are some at Ariel ( I won't mention names) who imply the Charged K24 is the best choice, I suppose before the latest Atom 4. If I quoted them they would deny it, for impartiality, and all engines in all Atoms are great.

• IMHO, The K20 sounds better than the K24 both NA and charged, on both normal and sports exhaust. I can live with that though.

• So I went with the K24, and combined with the light weight flywheel, its a great, for me. 99% of my Atom ownership has been road driving. If I was doing more track driving I think the K20 and its addictive high end would have been more enjoyable.

Thats my view anyway. No doubt there will be others

[John Scherrer]

I think the K24 gets its larger capacity from a longer piston stroke and as a result, the revs limits have to be lowered.
The higher low down torque actually suits a turbo/charger configuration.

The pistons in a longer stroke engine would need to travel much faster in the cylinders at the same revolution speed.

The revs are also limited as the K24 engine is challenged in the breathing area as there's a much poorer exhaust port design (2 exhaust ports compared with 4) which strangles the engine somewhat.

See the K24 engine below with its 2 port exhaust manifold.

K24 Exhaust Port.jpg (93.78 KiB) Viewed 259 times

[PhilTimo]

Thanks for your very informative replies.
90% of my driving will be on the road, so I think I can live with the slight negative aspects.
From my test ride I have no issues with the noise, I thought it sounded awesome, and was certainly quick enough!
Thanks Again
Phil