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l28et using l24 crank and rods


trowa47

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Changing over to L24 rods and crank will change your rod to stroke ratio...this is true. Why?.... the theoretically optimum rod to stroke ratio is 1.75. The way this figure is calculated is to divide the length of the rod by the stroke of the crankshaft.

 

L24 specs: 133mm/73.7mm = 1.80 rod/stroke ratio

 

now, lets look at the L28

 

130mm/79mm = 1.65

 

These numbers reflect the inherent 'revability', the higher the number (like the L24) the higher the redline of the engine. On the other side of the coin, a lower number (like the L28), the more low speed torque is produced. It's a mechanical thing. Many papers have been written on the topic, so I will suggest you read some of them off the 'net. They will give you far more insight into what's happening inside your engine than I.

 

The advantage you have in building such an engine is that H/D rods are available off the shelf (from Carillo for example) in this size. You are custom building pistons, so that's cool.

 

There's heaps more in it, like the instantly lower compression for boosting using the same cylinder head, large valves compared to the swept volume of each cylinder and the H/d parts available. Cam timing shouldn't be an issue, and MSA has some bigger turbo cams if you need them. However, the stock turbo cam will work well if you so choose.Don't worry about capacity, wind in a little more boost, that'll cover it!!:-)

 

Interesting project, I considered something like this for my P230 Cedric, instead using an L20A crank I have sitting in my shed. BTW, that rod to stroke ratio works out to be 135mm/69.7 =1.94. Easy 8k rpm motor there, if it was built correctly, of course! (valve springs, rockers, port sizes, good quality valves, pistons, bottom end balance, flywheel material etc etc etc)

 

Good luck mate with your project...:mparty:

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