full PDF here! - Progress Technology

story by per schroeder·
photos as credited
•
pJ:QJect
In
street and around town. It gets the job done without drama and
without
stock fotm,
fuss. the
Once
Classic
the activities
SE-R is a move
competent
to thepetformer
track, however,
on the
understeer is the dominant trait-and when push comes to shove,
the SE-R needs more than a little help to get around corners quickly.
The work so far on our 1991 Nissan Sentra SE-R has progressed well,
as our car now looks good and puts all of its 140 horsepower down to
the ground, that last part due to its recently added NISMO clutch-type
differential. The car also has minimal wheelspin thanks to the sticky
Falken Azenis tires that we mounted on Team Dynamics wheels, but the
Sentra just doesn't handle like a go-kart.
While the NISMO differential bumps us into the SCCA's Street
Touring X class, the suspension allowances in that class are identical to those in the popular Street
Touring S ranks. We can still lower
data sheet
I
and stiffen the suspension using
project: preparing a 1991 Nissan Sentra SE-R for autocross.
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part I: acquiring---.--.-and then painting~ the subject (October 2005).
part II:
limited-slip diff, (November
part III: improving the sus~~!:!~L?_!:!(this
issue).
different struts and bolt-on anti-roll bars. We can change alignment
settings using camber plates and alternate strut bolts. The rules also
allow for suspension strut bracing that connects left to right, but
without any triangulation.
There's work here to be done.
fixing the Econobox Origins
The MacPherson strut front and rear suspension on the Sentra is
let down by several major problems. For one, this design is not blessed
with copious amounts of suspension travel-it's only around 3 inches
in stock form. Lowering the car just an inch using traditional "sport"
springs will leave the car with less than 2 inches of total suspension
travel, and this can cause massive amounts of understeer if the car winds
up cornering on its bumpstops.
The stock suspension is also very limited in the amount of negative
camber that can be dialed in. Neither is there any provision for caster
adjustment, which can help cornering by providing more negative camber
as the wheel is turned.
The final problem is actually the easiest of all to solve: The car sits
too high and has very soft spring rates, a combination that yields lots of
body roll and an additional loss of traction.
Our goals for a competition suspension will be to lower the car
about an inch without compromising suspension travel, increase the
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107
To keep our Sentra moving along, it was
time to tackle the suspension. We chose
Progress Technology coil-overs (far left);
the setup includes springs, perches,
dampers and all required hardware.
Ground Control camber plates (middle)
allow us to dial in :zdegrees of negative
camber and :l degree of positive caster.
A small adapter sleeve (below) was
needed to mate the Progress coil-overs
to the Ground Control camber plates.
The Progress front anti-roll bar is a
full30mm thkk; Its hollow construction reduces weight. To further reduce
weight, this Braille lightweight battery
(left) helped us remove :z6 pounds from
the left front comer of the car.
negative camber and positive caster for better cornering grip, and
increase the wheel rates for better roll, squat and dive control. Finally,
we'll also need to increase the front grip relative to the rear to make
the car more neutral in cornering.
Making Progress
The easiest way to solve several of these problems at once is to
install a threaded-collar, coil-over strut with higher spring rates. The
traditional way to accomplish this is to get a high quality shock,
like a Koni, Tokico or Bilstein, cut off the stock perch and install
a threaded coil-over sleeve that can hold a smaller-diameter spring.
But this doesn't address the problem of suspension travel, since the
strut length hasn't changed and that is one of the real determinants
of suspension travel.
Thanks to the not-so-gentle prodding of enthusiasts, Progress
Technology has developed a complete coil-over shock and spring
package for the Classic SE-R that is now available at a reasonable
price. This design uses a shortened and threaded shock body that is
fitted with perches for standard 2.5-inch race springs.
The package comes with 350 Ibs.lin.
springs for the front and 250 lbs.lin.
springs for the rear. The shock bodies
are about 1 inch shorter than stock, both
from and rear, so that you can actually
lower the car an inch and still maintain
the stock amount of travel. With a street
price of about $1300, the Progresssystem
is a quite affordable choice when compared to other solutions.
The Progress shock valving was developed for a mix of track and street use,
and while it is not adjustable, we have
found ourselves continually impressed.
The car works well on the autocross
course and is still usable on a daily basis.
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Motorsports
108
While we might like a little mOte rebound damping in the from for quick
high-speed transitions, the adjustmems possible with the anti-roll bars
have helped us dial out some of the inevitable twitchiness.
To help with our camber and caster adjustment, or lack thereof,
we turned to Ground Control for a pair of their "world-famous"
camber plates. The camber plates are machined out of billet aluminum and allowed us to gain an additional 2 degrees of camber and
1 degree of positive caster.
The plates bolt onto the top of the strut towers and use the stock
mouming holes. Since they moum on top of the strut tower, these pieces
increase suspension travel by about three-quarters of an inch.
Even though our car now sits an inch and a halflower than stock, we
still have more suspension travel than a stock SE-R. Ground Comrol
camber plates retail for $399 for this application.
Lean Less With Anti-Roll Bars
While the Progress rates are stiffer than stock, they didn't supply all
of our desired wheel rate for our car. Most serious SE-R autocrossers are
running upward of500 lbs.lin. from springs along with the already beefY
stock from ami-roll bar matched with a
large aftermarket rear bar.
Since we're going to run the out-ofthe-box Progress spring rates, we needed
to increase our wheel rate with larger
front and rear ami-roll bars.
Progress Technology has developed
a pair of well-engineered adjustable
anti-roll bars with heim-jointed end
links for the Classic SE-R. The 30mm
front and 22mm rear bars are easy
to bolr on, and their adjustable end
links allow for tuning to our liking.
We could also preload the bars after
corner-weighting the car. The Progress
pieces retail for $380 for the set.
Strengthening
Our Chassis
A weak and flexible chassis is never a good place to srarr
a race car projecr. Unforrunately, the SE-R's economy car
roors are exposed by its lack of chassis rigidity.
Extra bracing is allowed under our STX-class rules,
but there are some limits. Bars may only be mounted
"transversely across the car from upper right ro upper
left suspension mounting point and from lower right
ro lower left suspension mounting point." In other
words, you can't triangulate things.
For rhe upper front, we purchased a strut tie bar from
a vendor on eBay for $36, including shipping. While it's
pretty obvious that this piece isn't as well-made as we'd
like, an upper Strut bar is a pretty simple device. This one
fit okay; ro gain another quarter-inch of shock travel, we
bolted the strut bar mounts below our camber plates.
For the lower front, we used Progress Technology's
$140 tie bar. Unfortunately, this piece as delivered
is actually roo well-designed ro be legal for Street
Touring; it has twO extra mounting eatS designed ro
triangulate the lowet control arm
mounts ro the subftame mounts.
We cut off these extra points ro
maintain our car's legality. While
it's now not as optimal, the bar
still ties rogether our two lowet
control atm mounts.
In the teat, we used a piece
tecommended
by the members
of SR20Forum.com:
an Active
Tuning rear strut rowet bar that
we purchased for $99. (That ptice
includes shipping.) This billet
aluminum bar weighs just four
pounds, and ir's so nice looking
it's almost too bad that it's hidden
behind the rear seat.
To stiffen our aging Sentra
chassis, we used bracing from
both Active Tuning and Progress Technology (above). The
Active Tuning rear strut tower
bar Is formed from anodized
lightweight aluminum. To
make the Progress Technology lower front tie bar legal
for SCCA's Street Touring
rules, we had to remove Its
triangulating
ears. A reciprocating saw easily handled
that task (left).
Shakedown, Corner-Weighting and Alignment
Once the suspension was bock together, we drove around the block to make sure there were no unusual noises. A slight
clunking in the front suspension was traced to a mismatched spacer that was used to adopt the Ground Control comber
plates to the Progress Technology coil-overs. We tried a few different spacers until we arrived at a solution that worked. This
problem has since been properly rectified with both companies supplying the correct adopters.
To get the cor to turn left and right equally, we needed to corner-weight it-thread
each spring perch up and down in on
effort to move weight between the four corners. Ideally, the two diagonals would be equal, meaning the sum of the left-front
and right-rear weights would equal the total of the right-front and left-rear weights.
To start the process, the cor was
pushed onto our Longacre scoles,
with each tire parked on its own
pod. We disconnected
the front
and rear anti-roll bars, jumped in
the driver's seat, and checked the
baseline numbers.
LF:
900
LR:500
RF:
824
RR:482
Total: 2706 pounds
It looked like we hod to raise the
right-front to get the RF/LR diagonal to
equal the LF/RR diagonal.
Before we
did, however, we installed a Braille Auto
battery from US Rolly Team. This 11.5pound battery removed 26 pounds from
the heaviest corner of the car.
LF:
874
LR:500
824
LF:
860
RF:829
RR:482
LR:
510
RR: 481
RF:
Total: 2680 pounds
We then aligned the car using a Smart Products SmartCamber
gouge
and SmartStrings
alignment
system. The camber was set at 2.9 degrees
negative in the front, which was the maximum that we could get. The
rear comber was set at zero degrees as a starting point. If we need more
grip, we can always add the camber in as necessary. The toe was set at
1 Is-inch
toe-out in the front and zero in the rear.
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Motorsports
110
After the battery was snugged
down, we started
adjusting
the
perch heights on the coil-overs. The
right-front was raised about half an
inch in the process to get our corner
weights correct. Here are the final
corner weights.
Total: 2680 Rounds
You can check out the
latest developments
with
this and other project cars
on our Web site, www.
g rassrootsmotorsports.
com. We post race results
and driving impressions on
a weekly basis, including
last-minute tweaks needed
to get the most out of our
project cars.
Out on Course
We fitted our
Sentra with
Carbotech Bobcat
brake pads. Their
brake torque and
modulation have
made us happy
with the decision.
We bolted up a set
of Goodridge stainless braided brake
lines to provide a
nice, firm pedal.
We were really excited ro starr attending aurocrosses
in our newly suspended SE-R. On the street, the car felr
truly awesome, with just the right amount of trailing
throttle oversteer ro make things lively-all without an
abundance of understeer.
Once we dialed in the correct tire pressures-we're running 39 psi from, 35 psi rear-we starred finishing in the
rop index positions on a regular basis. The car appears ro love
fast transitions where there are few slowdowns to highlight
its lack of real power. At one notable SCCA event, we were
the fastest car with fenders, beating Corvetres and Porsches
along with Subarus and Hondas. Fun, fun, fun.
Fresh Brakes
205/50R15 size. According ro the tire test we did for the
August 2005 issue of GRM, the new Falken is even faster
than its older brother. True ro our testing, the new Falken
felt great on our project car and we hoped ro continue
our wll1nll1g ways.
To see how we'd stand against some rougher competition, we drove ro Atlanta for the SCCA Tire Rack
National Tour. While we felt the coutses were a bit
horsepower-intensive,
we were hopeful that the SE-R
had the right stuff ro get the job done against the typical rulers of the class: the Subaru Impreza WRX, BMW
330Ci and Acura Integra Type R.
We learned a few things in the process of finishing fifth
in this I3-car class. First off, the new Falkens obviously need
ro be shaved and heat cycled to work their best, as we had
very little grip the first day. The tires have since become
more grippy as they've worn down. We'll be shaving our
next set to 4/32-inch.
After a few autocrosses, we noticed some funny sounds and
quite a bit of fade from the brakes. The pads that came with
the car were obviously less than stellar, and the ami-ratde clips
were dragging against the rorors as the brakes got hot.
Second, we need more power. The top-finishing car was last
After we baselined the srock brakes, we installed new
year's national champ, Tom Hoppe in his Subaru WRX. His
rorors, Goodridge stainless braided brake lines and Car2800-pound WRX is pushing some 240 horsepower at the
botech Bobcat pads. We bedded in the pads and allowed
wheels.That's both more powerthan we expectedand lessweight.
them ro cure for a few days before we retested the braking
distances. Subsequent testing indicated that the braking
power like
improvemems
for the SR20DE
engine.
Looks
our next installment
will cover
legalhorse- IJ ~
distances were decreased from
157 feet ro 148 feet, a 9-foot
sources
improvement. Our braking distances were a litrle longer than
Active Tuning: rear strut tower brace, www.activetuning.com
expected thanks ro the older tires
BSI Racing: differential installation, (386) 677-5778, www.bsiracing.com
and massive amounts of negative
camber that we were running.
Carbotech Engineering: brake pads and rotors, (877) 899-5024, www.
carbotecheng.com
III' .
Learning Some Things
With our aging Falkens
just about roast, we ordered
a set of the new-style Falken
Azenis RT-61 5 tires in the same
eBay: deals, www.ebay.com
Falken Tires: tires, www.falkentire.com
Ground Control: camber plates, (530) 677-8600, www.groundcontrolstore.com
Mossy Nissan: Nissan replacement parts, (800) ASK-MOSSY,
www.mossy.com
Nissan Motorsports: NISMOand Nissan Competition Parts, (310) 538-
2610, www.nissan-usa.com
Progress Technology: coil-overs and anti-roll bars, (714) 575-1193,
www.progressauto.com
Projekt 7 Tuning: dyno testing, (386) 673-9057, www.projekt7tuning.com
Red Line Oil: Heavy ShockProof Gear Oil, www.redlineoil.com
Smart Racing Products: camber gauge and string alignment system,
(800) 383-0808, www.smartracingproducts.com
SR20 Forum: Nissan SR20 message board, www.sr20forum.com
Team Dynamics: wheels, (909) 947-0114, www.teamdynamicsusa.com
The Tire Rack: Goodridge brake lines, (888) 981-3952, www.tirerack.com
Usually Sideways Rally Team: Braillelightweightbattery,www.usrallyteam.com
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