Necessary Adjustments for proper operation of the Street/Strip
Thrasher
Due to the nature of this product, and to offer these special features, the
Thrasher is much more sensitive to misadjusted components/sensors/systems
than other chips. It is important that all systems be in spec and operational
for the Thrasher to perform properly. Of special importance is the fuel pressure.
Unlike other manufacturers, we calibrated the Thrasher specifically for 45
psi of fuel pressure measured with the vacuum off. 45 psi was chosen as this
is the upper range where most injectors optimally operate; additionally,
every Bosch 237 regulator we’ve measured has speced within 1/2 psi of
45. A stock Bosch 233 regulator does not have sufficient fuel pressure for
the Thrasher to idle properly as it will run too lean.
We understand very well that fuel pressure must be adjusted somewhat to dial
in a car at the track. Our suggestion - if 45 psi is too high, turn up the
boost! If more fuel is needed, it’s not advisable to go much higher
than 47 psi as the spray pattern will become erratic. Generally speaking
we do not run injectors at their maximum in the Street Thrasher as we do
not anticipate running max boost under normal driving conditions. Strip Thrashers
do take advantage of everything the injector can offer to accommodate increased
boost levels. If we’re already running your injectors static, we recommend
you make the move up to bigger injectors! (Or turn down the boost. But we
already know you won’t consider that right!?)
The regulator must also operate properly by increasing pressure as boost
increases and decreasing pressure when manifold vacuum is high (i.e. at idle).
A regulator that does not lower pressure with vacuum (as some stock appearing
adjustable ones do) will cause the idle to be too rich. Misadjusted fuel
pressure or an inoperative regulator will cause erratic idle and poor
driveability. For those who own a scan tool, with the engine fully warm,
your O2 volts at idle should be in the 650-800 mV range.
Another important adjustment is the minimum air setting (i.e. the throttle
blade gap at idle). A detailed procedure for setting the throttle blade gap
is outline in the service manual or available on the GN-Ttype web site. Opening
the gap too wide will cause the Idle Air Control (IAC) to completely close
and no longer be in control of the idle speed. Too small a gap will cause
the IAC to open too wide and be unable to react quickly enough to control
idle well. For those with a scan tool, IAC counts in P/N should be around
10-20, in Drive 20-40 at idle.
The first time you start the car after a chip change MAY result in a stumble
almost to the point of killing the engine, then a sudden flare in RPM and
an abnormally high idle after that. This is nothing to worry about - simply
let the engine run about 10 seconds and kill the engine. Let it sit for another
10 seconds and restart - everything should return to normal. What’s
happened is the IAC got lost. The IAC resets after every legitimate keydown
to ensure that the actual IAC position and ECM determined IAC position agree.
Sometimes, in the course of changing the chip, this relationship gets altered
and the two no longer agree, causing the troubles mentioned above. Doing
a legitimate keydown and restart resets this relationship.
For those of you without a scan tool who are serious about having an optimally
running car (this should be all of you or you wouldn’t have this chip,
right?) we have two words for you: GET ONE! We highly recommend Ken
Mosher’s TurboLink from TDS Technologies if you’ve access to a
laptop computer. He can be reached at 402-292-6707, email him at
Kenmosher@nfinity.com, or visit
his web page at
http://nfinity.com/~kenmosher/tlink. |
