Inside a Dansk OE exhaust
- Thread starter Simon Davidson
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I wanted to bump this again and thought I would also add the following info re SSIs that I found elsewhere:
The SSI headers were designed for the 2.4 and, big at the time, 2.7 liter engines they are outstanding products for these engines because of the size and considerable valve overlap that they use. Modern smog motors have so little overlap that the exhaust flow volume is the primary advantage of one exhaust over another.
The SSI w/ 1 3/8" ID primary pipes flows 9180 l/min optimally. When they are put on a 3.0 they perform well but not as well as on the 2.7, in this app they are asked to flow 10200 l/min. To do so the exhaust gas speed must go up, this is good as it provides a boost in torque lower in the rev range than w/ the 2.7 but begins to back up a tiny bit at the top.
W/ a 3.2 and a bit lower rev limit they are asked to flow 10400 l/min, again at the bottom of the rev range gas flow speed is increased, increasing torque, but again as the revs build the gas speed increase is restricted and cannot keep up w/ the flow. This is a small effect only happening at the top of the rev range. There is a nice increase in torque lower down and since most folks drive 98% of the time in the lower part of the rev range, this is the increase that they feel.
The SSI can also be used on 3.6 where they are asked to flow 11700 l/min and the effect outlined above becomes even more apparant.
When compared w/ a stock exhaust system, where the cat is the biggest restriction to flow, the SSI have the edge throughout the rev range, doing better at the bottom but w/ the margin narrowing to only a few ftlbs at the top. If the cat is replaced by a properly shaped resonator/premuffler that does not disrupt the gas flow and can in fact enhance it, the gap is further decreased.
So while the SSI are better, are they a cost effective solution? It's your decision.
If happier cams are introduced then the additional advantage of a tuned equal length exhaust system can come into play, further enhancing the SSI torque advantage over stock.
The objective in the selection of primary pipe ID is to have the maximum gas speed at maximum revs w/o restriction. Too big will slow gas speed throughout the rev range, more so at the bottom, this is bad for torque.
RB
The SSI headers were designed for the 2.4 and, big at the time, 2.7 liter engines they are outstanding products for these engines because of the size and considerable valve overlap that they use. Modern smog motors have so little overlap that the exhaust flow volume is the primary advantage of one exhaust over another.
The SSI w/ 1 3/8" ID primary pipes flows 9180 l/min optimally. When they are put on a 3.0 they perform well but not as well as on the 2.7, in this app they are asked to flow 10200 l/min. To do so the exhaust gas speed must go up, this is good as it provides a boost in torque lower in the rev range than w/ the 2.7 but begins to back up a tiny bit at the top.
W/ a 3.2 and a bit lower rev limit they are asked to flow 10400 l/min, again at the bottom of the rev range gas flow speed is increased, increasing torque, but again as the revs build the gas speed increase is restricted and cannot keep up w/ the flow. This is a small effect only happening at the top of the rev range. There is a nice increase in torque lower down and since most folks drive 98% of the time in the lower part of the rev range, this is the increase that they feel.
The SSI can also be used on 3.6 where they are asked to flow 11700 l/min and the effect outlined above becomes even more apparant.
When compared w/ a stock exhaust system, where the cat is the biggest restriction to flow, the SSI have the edge throughout the rev range, doing better at the bottom but w/ the margin narrowing to only a few ftlbs at the top. If the cat is replaced by a properly shaped resonator/premuffler that does not disrupt the gas flow and can in fact enhance it, the gap is further decreased.
So while the SSI are better, are they a cost effective solution? It's your decision.
If happier cams are introduced then the additional advantage of a tuned equal length exhaust system can come into play, further enhancing the SSI torque advantage over stock.
The objective in the selection of primary pipe ID is to have the maximum gas speed at maximum revs w/o restriction. Too big will slow gas speed throughout the rev range, more so at the bottom, this is bad for torque.
RB
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