Originally Posted by Ondonti
The hp production has nothing to do with their bore/stroke. It is just their car is set up so that is maximizes power output above 6k rpm's.
I beg to differ. There are several 2.5 16v T-III motors and I know of one 16v 2.5 hybrid with a head that flows 280cfm. All of them make peak HP under 6k.
I had my stock T-III head flowed and it was 215cfm compared to the V-tec head they flowed on the same bench. The difference was 20cfm tops.
Convert the said engines to 2.2 stroke and HP increases along with the peak HP. This is nothing new.
This reminds me... if you were on the FMML R+D list a few years ago, you will remember a certain incredibly smart person with an *extensive* background, but who preferred his anonymity. Only a select few have had the opportunity to know him and that he is certainly a wealth of information. (same for 5digits) Here's a snipit that he wrote to me a couple years ago:
"> Hi Steve,
It's been a while. I think the motorcycle world is a really good way to show
the properties of the dynamics you refer to. The 2.5 is actually a good
engine to work with as long as it's limits are accounted for. I would not
put aluminum rods and a 4340 crank in it to turn 9500 rpm, when things are
going so fast that half that air can go in because of the piston speed! A
2.0 can make 900 hp and turn 9000+ like it is going out of style. Turbo's
can mask this pretty well though. But there is still 200 hp in going to a
smaller stroke. My uncle proved this in the '70's with the 2.3 ford. They
tried 4.25" stroke down to 2.75" and found that the bigger stroke hurt hp
but made allot of torque. But track times suffered allot due to traction and
a lot less top end power. Even though the cylinder head was ported to match
the combo. They ended up with 1.9 liters and 890 hp in 1976 .... "
Big bore is not really something that is good, especially on a 2 valve head. The bigger your bore, the more dead space you have in your cylinder to find detonation. A 4 valve head with a centralised spark plug is much better at holding down detonation at comparable charge densities.
I hadn't heard of that being an issue before... and I'm not saying it isn't true. Can you explain the "dead space" and how it contributes to detonation in more detail?
I do know a hot setup on a budget is to abandon the 440 and go with a 440 crank into a 400 block with proper rods and pistons. The 400 block has a larger bore and am told it comes out to 451 CI and will make much more peak HP and rev quicker compared to a 440.