I think Cameron was talking about using the FIA head on a 2.3 or 2.4L.
The additional 400cc would lower the powerband approximatly 1000rpm
compared to a 2.0L engine according to my calculations.
The only reasons a Z24 cranked L20B wouldn't rev out is because people
use rods that are too short and valves that are too small.
The way I see it you only have one option if you want to use all
standard Nissan parts for a large capacity L20B.
An L20B 2.3L 89mm bore x 92mm(Z22) 2289cc using 145.9mm L20B rods and
KA24 34mm pin height engine with a rod/stroke ratio of 1.59 might be OK.
Generally a rod to stroke ratio below 1.55 is considered to be bad for
engine wear and reliability.
If you wanted a 2.4L then 89mm x 96mm(Z24) 2389cc using 152.45mm
rods(Z20) and ~27mm piston pin height would give rod/stroke of 1.59 you
just need to find the pistons to suit.
I put this info into my engine simulator and I got the following:
Using 44mm valves, 41mm ID seat and 13.45mm(.530) lift both of these
engine give a mach index (average airspeed) of 0.5. Meaning that the
airspeed though the valve on average is at the valve/port maximum value,
maximizing volumetric efficiency.
The 2.3L would produce its max HP at ~6059RPM and max TORQUE at ~4767RPM
if I did my maths right. If the cylinder head port was 74% efficient
this would require ~43mm ports. This is why I think the FIA head could
be a good choice. I'd love the FIA actual specs please anyone.
On the same engine using 42mm valves, 38mm ID seat and 11mm(.434") lift
results in max HP at ~4663RPM and max torque at ~3099RPM. No wonder it
dont rev!
Whack a cam in this head to increase lift to 12.2mm(.480") and you get
max HP at 5171RPM and max torque at 3811RPM a little better. Any more
lift than this needs bigger valves and/or seats without sacrificing
volumetric efficiency.
A nice L18W out to 2.0L 88mm bore x 82mm stroke (1995cc) using 133mm L16
rods and 34mm piston pin height using 44mm valves, 41mm ID seat and
13.45mm(.530) lift.
Results in 1.62 rod/stroke and a .504 mach index, max HP at 7009RPM max
Torque at 5471RPM. I think this is what Brad was building but with the
FIA head? The only downside I see with this engine is the rod to stroke
ratio could be better with 135mm L20A rods? for 1.65 and the bore to
stroke improved aswell for less friction. To improve the bore to stroke
may then require the block be sleeved if possible.
Craig.
Brad HALLETT wrote:
>
> Hate to tell you this Cameron, but you will have trouble getting midrange
> out of an FIA head. They are designed to have maximum volumetric flow
> meaning a narrow high rev powerband. They really are for maximum rev
> applications only.
>
> Regards
> Brad HALLETT
>
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