Tuesday, May 17, 2005 at 23:09
Hi Chris
Glad to see your back and online. Now, everyone talks about the loss of backpressure in a bigger exhaust and its effect on bottom end, but to my way of thinking, the way a turbo operates is the bigger the difference in pressure between the inlet and outlet of the turbo, the greater the performance of the turbo. While I agree there is probably virtually no pratical gain between a 2-1/2" and a 3", I cannot see it being worse. You know from your experience that replacing the dump pipe gave arguably the biggest gain as it was the biggest restriction.
It reminds me of when I got extractors and 2-1/2" for my 80 diesel. Everyone reckoned while I would gain top end performance, I would lose bottom end.
Well, by the
seat of the pants that was true, but I had it dynoed before and after and what really happend was the top end gain was much better than the bottom end gain, so it "seemed" like bottom was worse but fact was bottom end improved marginally while top end gained around 15%.
Anyway, i don't know the answer for sure for turbos, but I don't think the myth of needing back pressure is true for turbo diesels. Especially in light of my 80's extrctors experience.
Cheers
Captain
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