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 data points.
Modifications Max. Horsepower (HP)* Max. Torque (ft-lbs)*
stock 111.6 HP 107.1 ft-lbs
Powerstack intake 115.2 HP 109.6 ft-lbs
Borla exhaust 118.3 HP 115.3 ft-lbs
Borla/Powerstack 113.7 HP 109.5 ft-lbs
Borla/Powerstack/Nology Hotwires/ Beru Silverstone plugs 119.5 HP 114.6 ft-lbs

*All values are SAE Corrected as measured at the wheels on a Dynojet 248E Dynamometer.

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.

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