Brad,
The L14 rods are the same design as L16 (big end & gudgeon and beam size)
but they are 3.65mm longer than the L16, or 6.45mm longer than L18 rods.
I believe the 4.9% increase in rod length and subsequent decrease in rod
angularity at maximum crank throw to be worthwhile. These engines sound and
go sweet.
The loss of piston acceleration close to TDC makes very little difference
in cylinder filling or power output as valves are only open 0.180" or so on
a race cam!. To compensate for the loss of piston speed a cam can be
advanced 5 or so degrees. If anything the frictive losses into the wall of
the cylinder by the piston/rings are substantially reduced.
Something subjective is that the engines also sound smoother and seem to
rev cleaner at higher engine speeds (7000 rpm +). I assume this is because
of the change in piston acceleration rate when the inlet valve is opened
and the gas acceleration rate is a bit less savage than in the shorter rod
version.
Another advantage is that you can run shorter pistons compression heights
and correspondingly lighter pistons.
Thats my thoughts anyway, right or wrong.
Comments please you budding engineers! .
Feral Errol
----------
From: Brad HALLETT <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Subject: Factory 88.7mm pistons
Date: Friday, October 27, 2000 11:12
Gday everyone
There has a been a lot of talk about the factory rally cars using 88.7mm
pistons. Whilst I was planning to build a stroked L18W with 88mm bore, I
have become more and more interested in the factory engine.
I therefore have two questions:
1) The engine I am building is L18W block, 88mm bore, with the crank
stroked to 82mm, L18 conrods with forged flat tops at custom compression
heght to suit. This gives a swept volume of 1995cc to keep in the 1600-1800
class. Would it be more beneficial to not build this stroker but to copy
the factory engine spec?
2) Are 88.7mm flattops still available?
Whilst I personally can see no problems with the stroker in terms of
reliability I am interested to hear your opinions.
Another question I must ask, whilst I have done no calcs or schematics so
may be way off the mark, would L14 rods be worth looking at for the
stroker?
I have had nothing to do with them so I don't know there strength, weight,
or even journal size.
Regards
Brad HALLETT
http://www.powerup.com.au/~bhallett
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Contact Errol SMITH
email: [EMAIL PROTECTED]
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