Honda’s gt-4 crx was America’s first real taste of what’s become a three-decade
long love affair with mugen, has resulted in a number of victories for Honda
The Head
The initial engine as prepared by Mugen was
based off of the Japanesespec cylinder head that'd been ported for increased
airflow. Inside, it featured its original valves, a reground factory camshaft,
and stiffer, dual valve springs, also from Mugen. Peterson says, the cam wasn't
anything particularly aggressive, which resulted in moderately increased lift
and duration.
A number of changes implemented within the
top end by Comptech once it began its development process resulted in a 33hp
gain. Here, intake valve diameter was increased, but doing so wasn't as easy as
you'd imagine. “The three-valve layout limited valve size since the intake and
exhaust valves would hit each other on overlap if their sizes were increased,”
Peterson explains. As such, only one of each chamber's intake valves were made
larger, which allowed valve lift to be increased, pushing peak power from 165
hp to 198 hp as measured on Comptech's in-house engine dyno.
The Induction System
Fuel injection wasn't permitted within the
SCCA's GT-4 class, which led to the CRX's 44mm Mikuni carburetor layout. Mugen
fabricated a one-off, billet aluminum manifold that allowed the carburetors to
bolt up seamlessly onto the cylinder head. A pair of low-pressure fuel pumps
fed by a fuel cell delivered 110-octane gas into the combustion chambers.
Nearly 30 years later, the air induction system remains virtually unchanged.
Fuel
injection wasn't permitted within the SCCA's GT-4 class, which led to the CRX's
44mm Mikuni carburetor layout.
The Oiling System
The CRX's original wet sump oiling system
was discarded in favor of a custom dry-sump system designed and built by Mugen.
The three-stage oil pump featured two sections dedicated to scavenging oil from
the pan and a third that supplied a high-pressure stream into the engine. The
system was also made up of a custom oil pan, an oil reservoir located within
the passenger-side foot well, a custom cast-aluminum oil filter housing, and
-12 steel-braided hoses that circulated fluid throughout.
The
system was also made up of a custom oil pan, an oil reservoir located within
the passenger-side foot well, a custom cast-aluminum oil filter housing, and
-12 steel-braided hoses that circulated fluid throughout.
The Exhaust Manifold
The CRX's exhaust system was based off of a
4-into-1 design that featured a relatively flat exhaust gas collector
underneath the oil pan. Peterson says, going off course was highly discouraged
and would undoubtedly result in all sorts of expensive exhaust system damage.
Mugen, who commissioned the header, had it fabricated out of equal-length
tubing that was formed and bent using a primitive albeit effective method.
Here, the series of tubes were packed with sand, heated, and bent into shape by
hand before being trimmed and welded to their corresponding flange and collector.
“A work of art,” they were, he says. The race-winning header, says Peterson who
visited its production facility, was hand-built in an 800-square-foot shop in
Japan by three workers who barely had room to function.
The Ignition System
Spark was delivered using the factory
distributor and ignition control module. Peterson says tuning was simple. Among
the only changes made was a crank-trigger ignition implemented by Comptech that
increased timing accuracy. “Tuning was pretty basic,” he says of its extent,
which didn't go far beyond jetting changes, “I loved it.”
Peterson also says that prior to Comptech's
involvement in 1986, the engine had yet to be dyno tested in the United States,
although it'd undoubtedly been initially tuned at Mugen's headquarters the
previous year. Baseline figures measured in at 165 hp at the end of 1985, after
Peterson had secured the Runoffs victory that he and Honda had been working
toward but before any changes had been implemented, which resulted in 198 hp by
1989.
Peterson, who along with Erb assumed care
of the CRX program following Uno's placement among the company's IMSA efforts,
says that, despite the Runoffs victory, the program later lost some of its
importance. “But it was a step [toward] the next project,” he says, “which was
the 1,600cc four-valve [engines] we ran in the [IMSA] Integras.”
Despite any perceived lack of interest,
though, Honda's GT-4 racing efforts did its part in accelerating the Honda
performance movement, not to mention the notoriety of Peterson, Erb, Comptech
and Parker Johnstone who'd later take over driving duties. Honda's GT-4 CRX was
America's first real taste of what's become a three-decade-long love affair
with Mugen, has resulted in a number of victories for Honda, and, most
importantly, what will always be the company's first automotive racing venture
in the United States.
Honda's
GT-4 CRX was America's first real taste of what's become a three-decade-long
love affair with Mugen, has resulted in a number of victories for Honda, and,
most importantly, what will always be the company's first automotive racing
venture in the United States.
