Quote:
Originally Posted by Sasquachulator
So was the FA20 not equal length? I know its not UEL cuz the characteristic boxer rumble is not really prominent (but there are hints of it at certain driving situations, namely going backwards or going slow)
Or what makes this "true" EL vs the FA20 I guess "not so" EL?
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Quote:
Originally Posted by Dzmitry
I have read several times in the past that the stock headers on gen1 are not EXACTLY equal length, and instead have a little variance.
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Correct. Technically if it’s not EL, it’s UEL. The first Gen was meant to be EL, but slightly compromised to make the manifold easier to make. The facelift made it closer to EL but not quite. The reason they don’t sound like UEL headers is because in order to get the subie rumble, the runners from the one bank must be waaaay shorter than the other. Perfect EL and slightly imperfect EL will sound quite similar, a very smooth tone. It will get harsher and harsher the more you make the runner lengths unequal, until the exhaust pulses start overlapping completely and you get the BWABWABWA sound.
See how the bottom graph the pulses are all evenly spaced and the same size? That’s true EL. The top graph shows the larger pulses grouped together, separated by multiple small pulses. This causes the Subaru rumble.