Luke,
The main problem with the NA (naturally aspirated) FJ20 is the lack of
abilty to get a high CR (compression rato). The NA FJ20E cannot get a CR
over 9.8 approx, due to the head design. Valve angles in the head are wrong
and pistons get in the way of valves etc. So if you shave the head you must
put reliefs in the pistons, that further lowers the CR. The best you can
expect from a NA FJ 2.0 is approximarely 185 - 190 hp, and that is a good
one. In NA form the engines are good for an easy 160 - 170 hp, but over
this it will cost you a large amount to get those last few hp. In stock
form the NA head flows sufficiently to acheive approximately 240hp so head
mods will not improve the HP capacity much if at all. It may even cause you
to lose some driveability at mid range speeds. Rather than looking for more
power from the engine, maybe look at ways to lose less of the available
energy to things like cooling fans, alternators, flywheels, body weight,
overall gear ratios etc. You can still get really good performance from
the NA engine at 170 hp as it is a high torque engine design.
The FJ engine was originally designed as the FJ24 NA. In this form the
swept volume of the cylinder is sufficient to achieve CR's of 11:1 and then
you can get some real power (260hp is realistic). To the best of my
limited knowledge the Z24 crank is not compatible with the FJ24 block.
(cylinder spacing is different I am told?). To make an FJ 24, you need the
FJ24 crank, rods and pistons.
The FJ's weight is a real downer in NA form in terms of hp/lb or Kw/Kg
engine mass. In spite of this I think the FJ is still Nissans best Turbo
engine in terms of reliability for power output. SR's do have a habit of
breaking exhaust rocker arms when used at reasonably high engine speeds.
Check the comments on the SSS automotive site on their engine designs etc
for more info on Datsun/Nissan engine designs and especially the FJ series.
Cheers
Feral Errol
----------
From: Leadex <[EMAIL PROTECTED]>
To: ozdat <[EMAIL PROTECTED]>
Subject: FJ mods
Date: Friday, April 21, 2000 6:54
I am desperate for some cheap ways to get some power from my FJ running on
webbers. The engine is in good nick as it is, so will a bit of simple head
work and bigger valves get much more power? Also, will Z24 parts fit to
build a 2.4L engine?
What is a cheap four cylinder place that can supply the parts and do some
of the work?
Thanks
Luke
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