Adjusting cam timing for best performance
(the "lost" web page........)
(under development)
When your cams are properly degreed, your bike will produce more power throughout the
entire powerband.
There is no serious professional team that doesn't individually set EACH
engine's cam timing for best power.
In 2005, Robert Jensen, using his own
EC997's dynos, was commonly the fastest
privateer in AMA 600 Supersport racing. He follows the below procedures and even
measures power changes resulting from valve clearance changes (yes, valve
clearance affects power).
WERA Nation #1 Endurance and and 4 #1 Sprint
champions, Mark Junge's Vesrah Racing also have their own
EC997's dynos.
Just like fuel injection and carburetion -
each and every engine individual engine requires it's own set of
"optimum" cam timing numbers for best performance.
If anybody says differently?
Well, either their test equipment isn't up to the level of the EC997 (that would
include ANY dyno that relies on Sweep
Tests for power), so the .5 hp increments that come and go are invisible to them
or they haven't spent the time to learn or had enough experience, yet.
But, I'd take a guy who says "I don't know, I haven't
tried that." over a guy who says "Just set it at blah de blah and that
will(?) be perfect.".
Slotted Sprocket Sets for the lucky owners of bikes
that have bolt-on cam sprockets. Replace the original sprockets with new sprockets
that have elongated mounting holes in the sprockets. The cams must then be adjusted, using
dial indicators and degree wheel to the desired cam timing settings on the intake and
exhaust.
Cam Sprocket Adapter Kits,
for the applications that have stock, pressed on cam sprockets.
OK........ Sooooo.....
What are the "best" cam timing settings? Hmmm.... Call 10 different tuners and
get 10 different answers or call 1 tuner and use those numbers or, look in our carb tuning
sheets and check for suggested starting settings.
Up to you!
....................................................................
The Factory Pro Tuning Method is to derive the absolute, optimum timing settings
for each engine.
Use an EC997 EGA
eddy current dyno WITH integrated EGA or similar (that wouldn't be a simple inertia
dyne or one with a huge eddy current brake hung on it)
in order to make the fueling or carburetion a constant, as you are looking for less than
.5 true hp changes
and, changing the exhaust cam timing will affect the correct main jet (or
equivalent by at least 1 size
and therefore at least 1hp, masking the benefit or detriment of the tested cam timing.
For current sportbikes, let's assume that
the intake cam timing is too retarded. Advance the intake cam until it just hurts the
top-end
power over the last 1000 rpm. Usually, set the intake so that the engine loses about 1%-2%
power at redline as compared with the maximum power. Check in 2 degree increments.
but.........Be
CAREFUL!
As you ADVANCE the intake cam, the
INTAKE VALVE GETS CLOSER TO HITTING THE PISTON!!! Check the clearance - before you
run the engine!!! SEVERE engine and personal damage (read: total destruction,
injury and persistent permanent vacation ) can be
caused by monkeying around with cam timing!! As if life wasn't already
fraught with peril!! :-)
Generally, advancing the intake cam increases the cranking compression - increasing power
below 8k (assuming a sportbike), which is below the effects of intake tract tuning which GENERALLY becomes in
phase at ~8k and above on current sportbikes.
Power improvements or non-improvements, 8k to redline, are due to optimally
or non-optimally setting the intake valve
closing point. That has to compliment the intake valve closing,
porting, valve seat angles and widths, intake port volume, velocity, length,
velocity stack ID, angle of divergence, the exhaust system.... and that's just
what cam to mind as I wrote this.... In fewer words, there are so many
variables, that it's an act of mental m..... to assume that you can use a
program to calculate best cam timing settings - I know all the above mentioned
factors affect he optimal cam timing settings, but I haven't seen a formula
that includes even more than 1-2 factors....
After you are satisfied that you have the intake
cam lobe center where you want it.... (having that little drop-off in power
at redline)
Retard the exhaust cam 2 degrees and check power and main jet/FI
selection. You'll find that, generally, moving the exhaust cam results
in power changes that are about 1/3 the magnitude in power changes resulting
from equal degree changes in the intake cam.
Example: if changing the intake cam 2 degrees, resulted in a 3% True hp change,
then, typically, moving the exhaust cam 2 degrees will result in a 1% true hp
change.
If you retard the exhaust 2 degrees and it loses power, then try advancing the
exhaust cam 2 degrees.
The power change with the exhaust cam will be a more "global" change - increasing
power, pretty much across the powerband - You aren't really looking for any
power drop-off at high rpm, though, if there is, it's up to you, the tuner, to make a choice
of what's important.
Generally, I try to improve power from 8000 rpm to a skosh below redline - as
that's what used on a racetrack. I use the same on most streetbikes.
Cruiser stuff works the same way - a 100 hp bike that redlines at 6000 rpm feels
better when the peak power is optimized for 5250 rpm, as compared to a bike that
make 101hp at the rev limiter (and less power below than the other bike). I
grimace when a guy comes in with a 1340 Harley and has a cam set that is too big
and now he wants to rev the engine till 8000 rpm. Sure, the lowend stinks, and
the bikes not as fun to ride...... It's not fun to tell the guy that that's a
bad idea and that he should use a smaller camset - and lowend would jump up and
peak would probably improve, too. There's no market so goofy as the metric
cruiser market - most stuff is dj dyno developed and some companies make these
utterly ludicrous power claims.....
In
30 years of doing this - I haven't been able to predict which way an exhaust cam
needs to go - advance or retard. I've asked others that have good dynos and good
test procedures and the only answer I've gotten from anybody that I trust is "I
don't know, either...." From some of the Sweep Test dyno guys, I get confident
answers, though.... but..... few specs developed under Sweep Test conditions
stand up to a Steady State or Loaded power test optimally.
If power had increased in the desired rpm band by retarding the exhaust cam, go another 2
degrees. As you RETARD the exhaust cam, the EXHAUST VALVE GETS CLOSER TO HITTING THE PISTON!!! Check the
clearance - before you run the engine!!! SEVERE engine and personal damage.....
After you have re-optimized the FI or main jet (if you are using an inertia dyne, you
will have to change main jets to see if power increases with different main jets -
with the EC997 EGA, you could check CO%, HC and CO2 readings to see if the optimum readings had
changed, perhaps negating the requirement of changing main jets again - saving an hour or
so of labor at each change.
If power decreased when you retarded the exhaust cam, try advancing the exhaust cam - in 2
degree increments. Basically, put the exhaust cam where it produces the best power.
Oddly, very often, testing on pre 2000 Suzuki 750's and Yamaha 750's done on inertia dynes seems to
indicate a 105 lobe center setting on the exhaust. I'm not sure why, but most commonly,
often, on the same applications, I end up with 101-102 lobe center, opening the exhaust
valve later (a longer power stroke) as compared to 105 lobe center, which opens the
exhaust valve earlier (shortening the power stroke). On the EC997, there is about a 1.5hp
to 2.5hp difference between the 2 settings (that can be felt on the street or track). With
a stock cylinder head on the GSX-R and YZF, 105 is not correct! (o - THAT'S
pretty old!)
Factory's Cam Sprocket Adapter Kit
- specially designed adapters replace the original, pressed on stock cam
sprocket assembly, allowing adjustments to cam timing.
Available through FACTORY or qualified local source.
application |
model |
year |
Slotted Sprocket
Kits contain: 1pr. replacement slotted cam sprockets |
Cam Sprocket
Adapter Kit
Kits contain:
1pr. slotted cam sprocket set
1pr. cam sprocket mounts
1 set cam sprocket bolt set |
Honda |
CBR600 |
91-99 |
x |
|
|
CBR900 |
92-99 |
x |
|
|
CBR11000 |
|
|
|
Kawasaki |
ZX-6R |
95-99 |
|
ra-camspkt-k59 |
|
ZX-7 |
93-99 |
|
ra-camspkt-k31 |
|
ZX-9 |
94-97 |
|
x |
Suzuki |
GSX600F Katana |
88-> |
x |
|
|
GSX-R600 |
92-93 |
x |
|
|
GSX-R600 |
97-99 |
|
x |
|
GSX-R750 |
86-87 |
x |
|
|
GSX-R750 |
88-89 |
x |
|
|
GSX-R750 |
90-92 |
x |
|
|
GSX-R750 |
93-95 |
x |
|
|
GSX-R750 |
96-99 |
|
ra-cmspkt-s37 |
|
GSX-R1100 |
87-89 |
|
|
|
GSX-R1100 |
90-92 |
x |
|
|
GSX-R1100 |
93-98 |
x |
|
Yamaha |
FZR400 |
88-90 |
x |
|
|
FZR600 |
88-98 |
x |
|
|
FZR600 |
|
x |
|
|
FZ750 |
|
x |
|
|
FZR1000 |
89-94 |
x |
|
|
YZF1000 |
96-97 |
x |
|
|
FJ1200 |
|
x |
|
|