Bolt On Up-Grades for your 300ZXTT (90+),

by Donn Vickrey

Here are some ideas on performance options for the 300ZXTTs.

The 300ZXTT is certainly very quick in stock form. However, there
is a tremendous amount of untapped potential waiting under its hood.
Performance upgrades range from mild, bolt on applications to custom
engine packages producing as much power as an IMSA GTS-1 race car.

The simplest upgrades are intake and exhaust systems.

Exhaust Systems:

According to dyno tests, an exhaust system upgrade will yield 18 additional horsepower and cut 1/4 mile times by approximately .2 seconds. Quality systems can be purchased for $800-$1,200 from Borla, HKS, Stillen, Trust, and Jim Wolf Technologies.

Most of these systems are pretty similar. However, the Borla exhaust system
is constructed entirely of stainless steel and should last longer than the
other brands. Of course it costs approximately 50% more.

After market exhaust systems will also give your car a more substantial
exhaust note without being loud and obnoxious. For the record, the Borla
exhaust is the loudest while the HKS system is the quietest. Don't worry,
performance exhaust systems don't produce the obnoxious, high pitched note
of the megaphone style exhaust systems used by high school kids these days.

You can also customize the appearance of your ZXTT with an extra large
single tip exhaust (one on each side) similar to that 93-95 Supras. Or you
can stay with the "stock look" for the stealth approach. Whichever look you
choose, all after market exhaust systems have larger tips giving the car a
more aggressive look.

Intake Systems:

An after market intake will also add 18 horsepower and cut 1/4 mile times by
.1-.2 seconds. The after market intake system is the easiest upgrade
to install - requiring only 30 minutes. Quality systems cost approximately
$100-$200. The best systems, marketed by Stillen and Wolf, consist of a
steel intake mounting bracket and large K&N cone shaped filter. There are
no modifications required; you can reinstall your stock intake system (if
needed) in only 30 minutes. The filters should last the life of your car.
Rather than replace them, you simply clean and re-oil them every 3,000-
6,000 miles.

Increased Boost:

Once you've upgraded your car's intake and exhaust system, the next logical
step is to increase boost pressure. The ZXTT can handle up to 14 psi. with
the stock intercoolers left in place. In stock form, the ZXTT runs 9.5
psi. Dyno tests show that 396 HP can be obtained from an exhaust, intake,
and a boost increase of 4.5 psi.

There are two approaches to adding the increased boost. One option is to
use an electronic or mechanical boost controller. HKS markets an Electronic
Valve Controller (EVC) which can be used to adjust the car's boost from
inside the cockpit. HKS and Trust also sell mechanical boost controllers
that reside under the hood. Manual boost controllers cost $50-$100 while
electronic boost controllers cost $700-$800.

There is two major problems associated with adjustable boost controllers.
Boost control devices do not adjust the ignition and fuel curve for the
additional boost. If your engine runs too lean, severe detonation can
result and you may damage your engine. Running too much boost can also
cause severe detonation. The scenario is common. The driver decides to
crank the boost up "just a little more" and kaboom! Believe me, you don't
want to blow your ZXTT engine. A broken piston will scratch cylinder walls
and can damage the block beyond repair. A ZXTT short block costs $7,500.
Installation runs about $2,500.

One way to avoid the temptation resulting from adjustable boost controllers
is to purchase an after market ECU. The ECUs sold by Stillen and Wolf are
adapted from stock ECUs. The stock "chip" is simply unsoldered and a
performance chip is inserted. The performance chips also come with boost
calibration jets that raise boost to 14 psi. The ECU upgrades also provide
several other benefits. Ignition timing, cam timing, and fuel curves are
optimized. Also, the rev limit is increased to 7,200 RPM and the top speed
limiter is removed. Yes, you can exceed the 155 MPH limit built into the
stock chip. But, before you rush out to try a top speed run, buy a set of
cooler plugs from Stillen or Wolf. The stock plugs are not up to the task
of extended full acceleration runs or, for that matter, the rigors of road
racing. Extended, heavy acceleration is one of the leading causes of blown
ZXTT engines. Check your owner's manual. Even the owner's manual contains
a warning of the dangers of racing (i.e., on a road course) with the stock
plugs. I've run this setup for 44,000 miles without any problem. I drive it
as intended every day; I love to spin the tires every few lights, run the
car hard in 15-20 second stoplight races, and scream up winding mountain
roads. But I do not run my car at the track and I have never attempted a
top speed run. Performance ECUs cost approximately $700 and can be updated
for another $100 if you decide to go with more upgrades in the future.

The next round of upgrades gets expensive. You can increase your ZXTT's
horsepower to 460-500 horsepower by running additional boost. However, to
safely run additional boost, you must install larger turbos, larger intercoolers,
and larger injectors. This will set you back $5,000-$6,000. To be honest,
I'm not convinced it's worth the investment. In one of my stop light races,
I ran across a 500 horsepower ZXTT. We raced two times for about 15 seconds each time. We were dead even each time. How could that be? A 500 HP ZXTT is no quicker than a 400 HP ZXTT? Well it doesn't seem to be.

Published times from enthusiast magazines and drag strip time slips support this observation. A 400 HP ZXTT covers the 1/4 mile in 13.1-13.2 seconds at 108-110 MPH. A 460-500 HP ZXTT runs the 1/4 mile in 13.0-12.9 seconds at 110-112 MPH. Not much difference - especially for $5,000-$6,000.

The problem lies in the torque curve produced by the larger turbos. Larger turbos are very peaky, producing peak torque at approximately 5,600 RPM. On the other hand, stock turbos have a long flat torque curve, with peak torque occurring at only 3,600 RPM.

Jim Wolf Technologies has two potential solutions to the problem mentioned
above. One proven solution is running nitrous oxide at low RPMs until the
turbos spool up. The staged nitrous setup is controlled by the upgraded ECU
to avoid detonation. Stillen also sells the staged nitrous package. Jim Wolf
also recently introduced a set of hybrid turbos (derived from the stock
turbos) that develop peak torque at a lower RPM. However, to my knowledge
there are no magazine tests or drag strip times available at this time to
document the performance of these turbos.

If 500 HP is simply not enough, Jim Wolf has produced one car that produces
625 horsepower on the dyno. The car has heat treated forged pistons, runs
22 psi., and also has the staged nitrous injection system. About six months
ago, I unwittingly raced this car from about 80-120 MPH. He blew my doors
off. It was absolutely no contest. Several months later, I was fortunate
enough to get a ride in this car. It was incredible. I've never experienced
acceleration like that before. But, when I asked the driver how long the
engine will last, his reply was "we don't know yet." If you have $20,000
and are not worried about engine life, maybe this is the setup for you! As
for me, I'll stick to the "conservative" 400 HP setup.

Donn Vickrey....