|The Truth About Weak Ignitions
Also known as, "Do I really need to spend $145 on spark plug wires?"
Those of you who have been following along as we try to figure out what works
and what doesn't in the arena of Saturn aftermarket performance may remember
a problem that we encountered in the summer of 1996. The problem was an unusual
loss of power that occurred when the Borla exhaust was combined with the
Powerstack intake. Hotshot reported similar problems when combining the Hotshot
header with the Powerstack intake. (See below for actual test results.)
The tests in question were conducted in the summer of 1996. They are not
related to the November tests that you will find at the Dyno Results section,
however, as one would expect, the results are very similar. For the sake
of simplicity, we will be referring to peak outputs only, rather than multiple
||Max. Horsepower (HP)*
||Max. Torque (ft-lbs)*
|Borla/Powerstack/Nology Hotwires/ Beru Silverstone plugs
*All values are SAE Corrected as measured at the wheels on a Dynojet 248E
As the table indicates, the stock baseline at that time produced a maximum
corrected output of 111.6 HP and 107.1 ft-lbs. at the drive-wheels.
The addition of the Powerstack intake while still using the stock exhaust
raised the maximum output to 115.2 HP and 109.6 ft-lbs.
Next, we tested the Borla cat-back exhaust with the stock airbox and filter.
This yielded a maximum output of 118.3 HP and 115.3 ft-lbs.
Now, this is where it gets weird. We expected to see a maximum output slightly
better than 118.3 HP and 115.3 ft-lbs. if we combined the Borla with the
Powerstack. Instead, our maximum output was only 113.7 HP and 109.5 ft-lbs.
- not even as good as either of the individual tests produced!
For some time, we wrongly assumed that the power loss was due to a lean fuel
mixture. However, when we finally started thinking, we decided to test our
conclusion. Using a common PDT scanner (courtesy of our local retail facility)
we ran a fuel trim analysis while using both the Borla exhaust and Powerstack
intake. Short-term fuel trim hovered around "128" which indicates a
stoichiometric fuel mixture (14.7:1-the correct value). Hence, the problem
was not fuel ratios!
Our next thought was ignition, so we went back to the dyno. Only this time,
we replaced the stock plugs and wires with Nology Hotwires and Beru Silverstone
plugs. Sure enough, that combination produced the results that we had been
expecting: 119.5 HP and 114.6 ft-lbs. See the graph above.
Our conclusion is that the stock plugs and wires are incapable of igniting
the larger mixtures that result from the addition of "breathing enhancers"
such as the Powerstack intake and Borla exhaust. Our data indicates that
an ignition upgrade such as that provided by the Nology Hotwires and Beru
Silverstone plugs corrects such a deficiency, allowing other modifications
to work effectively.