02-03-2018, 01:05 PM | #29 |
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Thanks for that confirmation. FYI: It looks like Faurecia makes the stock exhaust - at least that’s what’s stamped into the muffler. Whoever was in charge of the exhaust did a great job!
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02-03-2018, 01:09 PM | #30 | |||
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Quote:
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02-03-2018, 02:27 PM | #31 |
I used to be Dragoneye...
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Geese, that's what I meant to post!!! Did I copy the wrong link?!?!
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02-03-2018, 08:07 PM | #32 | |
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Quote:
I think it still applies, it's all back pressure.
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02-05-2018, 10:28 AM | #33 | |
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Quote:
we also make the GMT900, K2XX and the upcoming T1's. just a tipoff the iceberg on what we do.
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2000 status 02/01/16 3000 status 02/29/16 3400 status 03/07/16 TPW of 03/14/16 4200 status 03/17/16 in transit! Delivered 03/23/16 2SS Hyper Blue | 6M | NPP | Mag ride | ceramic white Int. | Black out bow ties | P3 Gauge| Front splitter. | 6 pot upgraded brembo brakes. | Magnuson Supercharger/95MM pulley | Rotofab Intake | ZL1 side skirts | HRE FF04 wheels - Michelin PSS4 | ZL1 add ons rock guards and lift points. | AWE touring - resinated catback with link pipes. |
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02-05-2018, 03:29 PM | #34 |
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2018 ZL1 1LE sw/PDR
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02-06-2018, 07:49 AM | #35 | |
corner barstool sitter
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Quote:
Flow restriction (and the attendant power/torque loss) is not just about the length of a reduced cross section area any more than it's only about what the cross section area was reduced to. And this only addresses the steady flow portion of the problem. The amount of "backpressure" an undimpled pipe has is probably only a fraction of one psi over the entire length, maybe something like 0.2 psi (I did look at some low pressure gas flow charts for this). Suppose that length from converter to muffler is 5 feet, so that becomes 0.04 psi per foot. Now let's make the crimp such that its resistance becomes 0.2 psi per foot (a good bit more severe than the case here), making the total pipe backpressure about 0.04*4.5 + 0.2*0.5, or 0.28 psi. So you've added less than 0.1 psi of backpressure . . . and to give that some context, each whole psi of backpressure costs about 7% power but you're gaining less than a tenth of that (around half a percent). Any change in cross section shape (even if the inside area remained the same) has the potential for affecting system resonances and their effect on tuning. This might even be a larger effect than the steady state part, at least within some rpm range or ranges. Norm
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02-06-2018, 11:16 AM | #36 | |
Drives: Crush ZLE M6 | 2000 Corvette FRC Join Date: Jun 2010
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Quote:
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02-06-2018, 05:06 PM | #37 |
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Crimping provides about an 1" of clearance from 'vert cross brace on my ZL1.
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02-06-2018, 05:10 PM | #38 | |
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Quote:
Thanks for the pictures!
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02-06-2018, 06:10 PM | #39 |
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Excellent info!! Thanks!
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02-06-2018, 06:37 PM | #40 |
corner barstool sitter
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No, not entirely.
But DG's theory, which you specifically called 100% patently false, is absolutely on the right track, as it did consider both cross sectional areas and lengths. I know that it's possible to construct outlandish examples that appear to prove something to be generally true when that is absolutely not the case, and that's when the sanity check requires actually running a few realistic numbers and letting the answer fall wherever it may instead of trying to hand-wave the whole thing away by implying that a simple comparison to the absurd is sufficient. I'm not trying to say that 1" of 1mm tubing wouldn't restrict flow severely (it'd probably choke the flow off to some smallish fixed value no matter how much pressure you put behind it, and how much power that would cost). But I will state that 1" of 1mm doesn't represent what's going on in the pinched sections of Camaro exhaust tubing well enough to have any meaning at all. Norm
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02-06-2018, 09:49 PM | #41 | |
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Quote:
My take-away from the original post we are hashing our was that the flow is not effected if the “restriction” doesn’t reach a certain length. It does. Regardless of length, there will be an effect. |
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02-07-2018, 07:29 AM | #42 | |
corner barstool sitter
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Quote:
What's left once we see that crimped region (and what actually matters) is whether or not the effects from it are significant. Seems a lot of people think it does simply because it looks like it should, and these people generally lack the analytical tools to either justify or debunk it on their own. Not that others being ready and willing to take advantage of that belief by pitching it in their advertising is helping. ** I used to review technical documents prior to issue as part of my day job, so maybe I still basically see things differently from most even though I'm over 5 years retired. Norm
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