I have never bent an L14 rod in spite of some pretty harsh treatment.
I ran my L14 engine to 9000 rpm quite often to avoid a gear change without
any mishap. The thing that used to fail was lash pad popping out due to
reaching the control limit of the valve springs.
Cheers
Feral Errol
----------
From: Craig Overend <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Re: Factory 87.8mm pistons
Date: Monday, October 30, 2000 11:43
Brad,
I have looked into the factory engine and they are not 88.7mm but 87.8mm X
78mm for 1889cc. Here are some of my thoughts. I too was
planning on an 88mm bore and 82mm stroke until I did some calculations and
measured my L18W block. One problem is rod length. 133mm rods are a
bit too short for ideal and this moves the whole torque curve down and also
reduces volumetric efficiency(torque). Ideally ~135mm rods are the
go for the 82mm stroke when combined with 44mm inlets, 40mm port at seat
and a cam with about .510" of lift. For this reason I have been trying
to track down whether there was an L20 6 Cylinder model that used 135mm
rods. All my calculation says there is such a rod but so far I cant find
reliable info or rods to support that. Near ideal stroke/bore ratio for the
widest possible powerband comes from a ratio of about .88-.90
varying depending on friction, rpm operating range and other factors For
this and reliability reasons to do with bore diameter, I assume
these are the reasons they designed the factory L18W rally engines the way
they did. Also instead of stroking the engines for more capacity
they just ran more rpm to use the available flow through the heads. While
the engines might not have been as torquey as they could have they
would be good HP producers. Other factors may have included rulebook limits
though. I'm sure that if they could reliably bore the block out
further they would have and stroked them too and run bigger valves etc...
Guess what I'm looking at doing. :)
L14 rods being ~136.7 would be a better choice for an 88x82mm engine just
depends on valve/ports/cam. You'd need ~30mm pin height.
136.7/82=1.67 ratio same as L18 for similar reliability. L14 rods use the
same journal size as L16/L18. I'm sure Errol could tell you if he
has bent any.
The current factory VW Golf kit car that Simon Evan runs uses something
near 90mm bore x 78.5, can't remember exactly. This is excellent for a
2L and one reason why it screams and goes so well.
cheers,
Craig.
Brad HALLETT wrote:
>
> 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
>
> Proudly Endorsing:
> ...DATRATS...
> http://203.33.35.34
> Datsun Dedicated
> For Nissan Motorsport Components
> Professional Budget Priced competition equipment
> Contact Errol SMITH
> email: [EMAIL PROTECTED]
>
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