Quote:
Originally Posted by Dimman
Engine predictions:
FB20 standard bore and stroke:
84mm bore X 90mm stroke: 200 bhp @ 7000 rpm, redline 7500 rpm (also redline of the Mk1 concept's interior, so...)
But not too mod-friendly.
FB25/20 de-stroked fantasy:
94mm bore X 72mm stroke: 205 bhp @ 7500 rpm, redline 8500 rpm
Very mod-friendly.
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I found something interesting when calculating the FB25 de-stroked engine.
We de-stroke it by 18mm which means the piston is sitting 9mm lower in the cylinder at TDC (,9mm higher at BDC) with a 129.3mm rod. A 129.3mm rod to 72mm stroke is 1.796 (higher than K20, 2ZZ: 1.62).
Stock CR was 10.5:1 leaving 9.4737mm between piston and head with a 90mm stroke. With a 72mm stroke it would need 7.5790mm between piston and head to maintain 10.5:1 CR.
This is of course without lowering the FB25 deck height, would mean that it would need a 10.89mm longer rod then the 129.3mm to maintain 10.5CR on a 72mm stroke resulting in a 1.947 rod-stroke. Might be a good custom race engine (it would be better with a semi/closed deck and) with the appropriate work on the heads and timing.
So it could be a FB20. Unless they decreased the deck height... Any thoughts?