camshaft - AMS Performance

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CAMSHAFT
SHOOT-OUT
CAMSHAFT SHOOT-OUT
TEXT AND PHOTOS BY MARTIN MUSIAL
CHOOSING THE ULTIMATE
BUMPSTICKS FOR YOUR EVO,
PART 1
W
hen selecting the perfect cam to match your performance needs, prospective buyers face the daunting task of choosing from 260-, 270- and
300-degree duration camshafts. What does it all mean and is getting
the “big” cam the best for your car? I’ll shed some light on the subject by doing
some real-world tests to show how different camshafts behave. Just like you
wouldn’t want a gigantic GT45R turbo on your daily driver/autocross car you might
want to re-think your camshaft choice before taking the plunge. I’ll use a system
for testing that will hopefully give you a better understanding to choose the right
camshaft for your applications, be it drag racing or autocrossing in the parking lot.
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JUNE 08 TURBO & HIGH-TECH PERFORMANCE
For this onslaught of abuse I put my ’04
Mitsubishi Lancer Evolution VIII on the chopping block. The 4G63 platform is rugged and
we’ve spent so much time developing power
with it that it makes a perfect test rig. The car
is outfitted with a bunch of AMS Performance
parts to support over 600 whp. The parts
range from an AMS GT35R turbo kit to the VSR
intake manifold and AEM engine management
system. The car serves multiple duties as a
daily driver, track day and drag racing car. For
testing, we used a Dynojet model 424x-LC
all-wheel-drive dyno. This dyno is reliable
and repeatable, which makes it a benchmark
in the industry.
We tested each cam using 116-octane race
fuel at 22 and 30 psi of boost. Using an AEM
EMS with built-in boost control and dataloging, each test was conducted at the exact same
boost level. The runs where done in Third gear
and start at 2,000 rpm and end at 8,400 rpm.
The fuel curve was adjusted for each cam to
maintain around 11.5-11.8:1 air/fuel ratio under
full boost. Since I’m using an AEM EMS in
speed density mode I can tell the power curve
by how much I have to adjust the fuel curve. If
it runs rich at a high rpm and I need to remove
fuel then I know it’s making less power there.
AMS MULE ENGINE SPECS:
BLOCK
ENGINE: 4G63
BORE: 85MM
STROKE: 88MM
PISTONS: AMS SPEC ROSS
COMPRESSION RATIO: 8.5:1
RODS: OLIVER
CRANK: STOCK MITSUBISHI
CYLINDER HEAD
VALVES: SUPERTECH 1MM OVERSIZED
INTAKE MANIFOLD: AMS VSR
THROTTLE BODY: STOCK
TURBOCHARGER
TURBO: GT35R STEEL HEADER
HEADER: AMS STAINLESS
WASTEGATE: TIAL 38MM
INTERCOOLER: AMS EVO VIII STREET CORE
EXHAUST: 3-INCH TURBO BACK
ELECTRONICS
AEM EMS WITH 3 BAR MAP SENSOR
Degreeing the camshafts
Peak Power: Once ECU adjustments are
made to stabilize boost and the air/fuel
ratio, two back-to-back consistent runs are
recorded. The peak power that each cam
makes is recorded. If your primary goal is drag
racing, this test is the most important.
Powerband: How many rpm is the usable
power curve. If a cam makes peak torque
early and keeps making good power to redline
it will score higher than a cam making only
good power near redline. Most street racers
and autocrossers would be interested in this
test. A nice wide power curve makes for a fun
street car.
Idle/Driveability: A subjective rating of how
lumpy or smooth the idle is and the quality of
low rpm driveability. Luckily, with the AEM
EMS I can make almost any cam idle well but
some have to run at 1,200 rpm for stable idle
while others run at 800 rpm. With a factory
ECU the story is much different. Some more
aggressive cams can cause very poor idle or
even cause the engine to stall. Also, low speed
running can be an issue with some cams and
even cause bucking or misfires. I know we’re
modifying our cars in the interest of making
them faster but most of us also use them as a
daily driver. That makes this rating high on my
list—it’s not very fun driving in traffic while
your engine keeps stalling out.
Camshaft manufacturers make their cams
to a certain reference point so when installed
correctly they perform to their design specifications. When installing cams it might seem
that just setting your fancy adjustable cam
gears to zero means the cams are installed
correctly. What if the cam gears are a little
bit off in their manufacturing or the dowel
pinhole is off a few degrees? How about if
the head was shaved and now the cams sit
closer to the crank? Any of these variables will
affect cam timing and what you thought was
zero is now something different. Every proper
race engine should have the cams degreed.
This doesn’t mean retarding and advancing
the camshafts until you make more power.
It’s a process where measurements are taken
to ensure the camshaft is installed per the
manufacturer’s specifications—basically to
start from a zero point. Since I’ll be testing
so many camshafts I need to degree each
camshaft to make sure that I’m running them
like the manufacturer intended. This process
requires a few tools and some patience. You
need a degree wheel so you can see how
many degrees the crank is turning and a dial
indicator to measure the amount of valve lift. I
assembled a used “test” engine on a stand for
the measuring process. Stiff factory springs
can make testing difficult, as the spring force
AEM UEGO GAUGE
TURBO & HIGH-TECH PERFORMANCE
JUNE 08
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CAMSHAFT SHOOT-OUT
SPRINGS: SUPERTECH DUAL VALVESPRINGS
How each cam will be rated
GARAGE.TECH
VS.
CAMSHAFT SHOOT-OUT
will try to spin the cam around on the opening
and closing ramps. To make things easier, I
swapped in some light springs.
Every manufacturer will give you some
specification on how the cams should be installed. For this example we’ll use a cam card
provided by Crane Cams. Cam cards give valve
lift points in reference to top dead center and
bottom dead center. Before we begin we must
first find top dead center, where the piston is
at its top most position. Using a degree wheel,
we mount the device to the crank snout. In our
case we’re using a digital degree wheel from
Altronics. This new device replaces the traditional degree wheel and pointer system.
This method offers some major advantages
over the old technique. Screwing in a piston
stop into the spark plug hole on cylinder No. 1,
we rotate the engine one way until the piston
makes contact on its way to top dead center.
A push of a button and then spinning the
crank the other way until it hits the piston stop
and the Altronics Digicam computes top dead
center. This system is much more accurate and
quicker than the traditional degree wheel.
Next, we mount a dial indicator in a way that
we can accurately measure valve lift.
While this sounds easy, it requires some
thinking and possibly fabricating some
fixtures to hold the dial indicator correctly and
securely. As with most engine applications,
the 4G63 engine uses hydraulic lifters, mean50
JUNE 08 TURBO & HIGH-TECH PERFORMANCE
ing oil pressure is constantly adjusting valve
lash. Unfortunately, with no oil pressure these
lifters start to collapse if you push down on
them. In my test, where there was no oil pressure, the cam lobe would ride on the follower
and collapse the lifter instead of transferring
all of its motion to the valve. Solid lifters to
the rescue! Installing these and then adjusting
the lifter until there is a little preload ensures
that the cam lobe motion will be transmitted
to the valve motion.
relatively easy to determine in the engine bay.
On my test engine I rotate the crank until the
Digicam indicates top dead center and I record
the intake valve lift. Crane provides this specification on their cam card (0.068 of an inch
of lift at top dead center) but most camshaft
manufacturers don’t have this information
readily available. Installing the cams in the
real engine, we transfer over our solid lifter
and the dial indicator to measure valve lift. I
screw in the top dead center indicator into the
spark plug hole on the first cylinder. Using
another dial indicator, I rotate the crank by
hand until I find the peak of the piston travel;
this is top dead center. According to the dial
indicator my valve lift is the same as it was on
the test engine.
This may seem like a tedious and complicated process—that’s because it is! The time
you spend doing this, however, may save you
hours of dyno time playing with cam gears and
possibly spotting a problem in your setup that
would otherwise go unseen.
Measuring camshaft lobes and
computing valve motion
To correlate the performance of each of
these camshafts I recorded the valve motion,
which shows the differences in cams and can
offer some insight on why certain cams perform the way they do. One way of recording
valve motion is to use the equipment I degreed
the cams with and just record the valve lift
every degree and plot it out on a spreadsheet. While this sounds simple, it’s a tedious
manual process that’s prone to error and not
very accurate. The best and quickest way to
do this is with cam measuring equipment.
Performance Trends offers a cam measuring
solution that integrates a cam test stand with
software. The cam test stand includes a linear
transducer to measure cam lobe lift and a
rotary encoder to measure cam rotation. The
data is collected in the cam analyzer software
and valve lift profiles can be compared and
inspected. In the next installment of this
article, I’ll get more in depth on this procedure
and what useful information we can gather
from it.
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TURBO & HIGH-TECH PERFORMANCE
JUNE 08
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CAMSHAFT SHOOT-OUT
With our dial indicator installed, we’ve
found top dead center and the cam is ready
to be degreed. The Crane Cams card specifies
that the intake valve should open 0.050 of an
inch at 4.5 degrees before top dead center. We
spin the crank over until the Digicam reads 4.5
degrees before top dead center. We look at the
dial indicator and see that we’re at 0.060 of an
inch of lift, which is 0.010 of an inch more than
specified on the cam card. The valve is open
too far at this point so the solution is to loosen
the cam gears and retard the cam until lift
comes back down to 0.050 of an inch. Looking
at the cam gear, the timing marks indicate the
cam is now 2 degrees retarded.
Cam manufacturers can give you valve
opening and closing events along with centerline values. Cam centerline is the amount of
degrees at the point of peak valve lift. In this
case the Crane Cam card specifies that the intake is on a 110-degree (after top dead center)
centerline. We move our crank to that point
and see that indeed the valve is at its peak lift.
Some manufacturers might give valve events
while some might only give cam centerlines
for installation so it’s good to know how to
do each one. We repeat the process of the
exhaust cam and find that it also is 2 degrees
retarded.
Now you’re thinking, you degreed the cam
in your test engine but what if the engine in
my car is slightly different? To make sure I’m
installing the cams the same way in my engine
as on the test engine I use a little trick to make
things easier. It’s virtually impossible to put a
degree wheel on a 4G63 engine once it’s in the
engine bay. One way to verify cam timing is to
determine cam lift at top dead center, which is
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Test results HKS 272 intake, 272 exhaust camshafts
First off, the HKS 272 idled very well. With
the idle set at 900 rpm, my Evo purred and
driveability seemed great, especially at a low
rpm and part throttle. After a few pulls to dial
in the air/fuel ratio and AEM boost control,
horsepower peaked out at 453 whp at 22 psi.
Next, I retarded the intake cam 2 degrees
and ran the test again. This closes the intake
valve later and could make some power at a
higher rpm. The dyno pull shows a slight loss
in low-end power and spool up and a slight
shift in the powerband. The peak power is the
same but the power curve filled out up top. To
see how advancing the cam would affect the
power curve, I moved the intake cam 2
degrees advanced from the installed point.
The run shows a very slight increase in spool
and low-end power but the top end power
suffers, losing 6 hp. I moved the intake cam
back to the installed specification and turned
the boost up to 30 psi. The dyno belts out a
521whp pull.
CAMSHAFT SHOOT-OUT
Test results Crane 272 intake, 264 exhaust camshafts
Upon startup the idle is a little rough. I
have to raise the idle to 1,200 rpm to get a
smooth idle that won’t let the engine stall.
Low speed running is a little choppy and
requires some careful tuning to make driveability acceptable. On the first 22psi pull I
noticed the cam spools later than the HKS
cams but starts to run lean as rpm climb. A
few tweaks to the fuel curve let me run to
the 8,400rpm redline. I had to add quite a
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JUNE 08 TURBO & HIGH-TECH PERFORMANCE
bit of fuel at a higher rpm but remove some
fuel at low rpm. This tells me right away
that top end power should be greater. To my
surprise the 22psi pull resulted in 505 whp!
The power kept climbing toward redline with
no sign of leveling off. I retarded the intake
cam 2 degrees and made another pull. Peak
power stays the same but low-end power
drops off. The power curve takes a hit almost
everywhere. Advancing the intake cam 2
degrees from the installed setting shows low
and midrange power gain and loses only a
few horsepower up top. The power curve is
widened with only a slight sacrifice at redline.
Putting the cam back to where I started, I ran
it up to 30 psi of boost. Peak power climbs to
557 whp. Although a healthy power increase
over the HKS 272 cams, the idle, spool up and
driveability suffer.
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Test results Tomei 280 intake, 280 exhaust
The car has a very similar idle to the Crane
Cams and the first pull at 22 psi requires no
fueling changes. Power checks in at 514 whp
at 22 psi, very impressive. Retarding the intake
cam 2 degrees does nothing but lose spool up
and bottom end power. Advancing the intake
2 degrees from the installed position boosts
the bottom end of the power curve with only a
slight loss in power up top (5 hp). The power
gained throughout the curve easily outweighs
the slight loss at redline. At 30 psi, power hits
558 whp, about the same as the Crane Cams.
Overall, the power output is very similar to the
Crane Cams.
CAMSHAFT SHOOT-OUT
Test results Conclusion
The first batch of cam
testing is done and I’m
surprised with the differences in the cams. So
far we have a well-mannered cam that doesn’t
produce the best peak
power but makes good
low-end grunt. The
other two cams scream
up top but at the cost
of idle and spool up.
The next installment
will explain in detail
how camshafts work
and the importance of
valve timing events.
Clear some space in
your cranium. It’s going
to get a little difficult
but you’ll have the
knowledge to choose
the right camshaft for
your combination.
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JUNE 08 TURBO & HIGH-TECH PERFORMANCE
sources
HKS USA
www.hksusa.com
CRANE CAMS
www.cranecams.com
TOMEI POWERED USA
www.tomeiusa.com
AMS PERFORMANCE
www.amsperformance.com
TIAL SPORT
www.tialsport.com
ROSS PISTONS
www.rosspistons.com
AEM
www.aempower.com
OLIVER RODS
www.oliver-rods.com
SUPERTECH
www.supertechperformance.com