Lots more power found with some new SR tuning ideas!

[mike kojima]

(from my post on sr20 forums, i'll post here because I
know that many of you hate forums and this is
interesting news)

Ok, just spent the day at JWT's dyno experimenting
with a bunch of things on the old DE.

For those of you too new to the SR20 scene, its my my
teal green 200SX, SCC's Project 200SX SE-R.  For many
years it was one of the most powerful NA SR's until
Andri Miko's latests big bore developments.  As a
recap, this is a fairly mild by todays standards
motor, one easily and cheaply reproduceable by anyone.
 It has 300ZX pistons, mildly ported low port DPR head
with modifed quench (which I now think is
superflurous), C3 cams, JWT ECU, Place Racing cold air
intake, Maxima MAF, extrude hone intake manifold and a
64mm thottle body.  Nothing exceedingly trick here.

What we did was to add a SR20VE 20V exhaust manifold
and a 3" exhaust with a magnaflow 3" cat, submuffler
and race muffler.  We also expermented with ECU
programing and cam timing.  We found the right way to
go with the programing and cam timing but had to call
it quits because of fears of pissing off the
neighboors.

First off, the cork in the DE's output is not the
intake manifold as I have speculated for years (and
what my software and book calculations tells me) but
the exhaust!  It seems like a well modded SR with cams
of a lot of overlap likes a BIG exhaust.  2.5" lost 6
hp over uncorked!  3" lost nothing though the cat!
The exhaust manifold is a major restriction as well.
We tried the 20V manifold because it has a 3"
collector and although a collector this big is against
conventional wisdom, we figured that the engineers at
Nissan are no dummys. This is going to hugely impact
future header design!

Next SR's like a lot of overlap and tight lobe
centers.  Going off my experince at TRD where we found
that simular motors like a lobe center as tight as 100
degrees, we found much power and torque here, in fact
you run out of piston to valve clearance before you
run out of power increse. Most people set their lobe
centers at 117-114 degrees, mainly baised on my
experementing a long time ago on S3's. Note that this
only works if you have low backpressure, big induction
and big cams like C3's, S4's etc.

Finaly with a lot of overlap, things that I found
previously that made no difference like big TB's, and
big MAF's start to make a difference.  Its all about
overlap scavanging and since the delta P's are low,
you need free flow.  Its sort of all against the
conventional wisdom accumlated so far.

The results are pretty amazing. The previous non
cherry picked power was a decent 172 hp.  Today we got
an amazing 188whp.  When comparing the power to Chris
Allen AKA Shaggy's VE, perhaps the current VE power
record holder, the DE is making more power from 4300
rpm, as much as 17 more hp to 6700 where shaggys power
passes to peak at about 11 more hp in a tiny sharp
peak.  Amazingly the DE has way more useable power
under the curve!  The powerband is broad and flat
accross the top from 6000-8000 where Shaggy's VE is a
sharp point, like a B series Honda.  This meaty
useable power.

This is with conservative 91 octane friendly tuning.
We set the mixture at about 12:7-12:8:1 when SR's
usualy make the most power at a crackly 13.2-13.3:1.
We got a couple more hp when leaning it out but backed
out because we wanted a margin of safety with 11:1 and
91 octane.

Shaggys VE makes better power below 4300 rpm, as much
as 11 more at around 3300 rpm due to the low RPM lobe
and 9 more at 2000 rpm, but you don't RACE at this low
of an RPM!

We proably have enough piston to valve clearance to
advance the intake cam 2-3 degrees more which should
yield over 190 whp and an even broader powerband.  We
can also screw around with exhaust cam timing (SR's
are pretty insensitive to exhaust timing but I think
we can reduce overlap here and improve idle) We also
have yet to do timing and mixture sweeps to see if the
program needs to be changed with the changes in cam
timing.  I'll report significant progress here.

We will also test a new JWT cam, a mechancial cam with
more duration and lift than any SR cam on the market
so far.  In some intial testing on a Grand Am Sentra,
these cams were worth 20 MORE hp than C3's on a milder
than mine (rules mandate) motor!  The only issue is we
won't have enough piston to valve clearance to
optimize the cam timing with this combo.

I will also test a short runner big plenum, manifold
with a 70mm TB which will be avalible for sale if it
works on this motor. I am pretty enthusiastic.  I
think it might be posible to get well over 200 whp out
of a plain old DE without spending extreme amounts of
money and with exotica like stroker cranks, sleeved
blocks, crazy cylinder heads, suicide tuned dyno queen
timing and fuel curves, etc.

Next I will attempt to extract more than 180 whp on a
full bolt on DE with a stock head and bottom end.  It
will be cams, springs, pulleys, CAI, intake manifold,
70mm throttle, Hotshot header, ECU, 3' exhaust.  This
will be as easy and cheap alternative to a VE.

I'll keep everyone posted.

Mike