[hotlap]

Mechanical Engineer here too. I’m with Norm.

[s346k]

i'm not an engineer. i took the complete stock exhaust off and put it in the garage. i've moved it twice and i think i'm finally going to move it to the rafters.

[Idaho2018GTPremium]

Originally Posted by L78toLT1

I'll bet that of all of the mechanical engineers weighing in on this discussion, I'm the only one educated at a school that has played, and beat Saban and Bama! Gig 'em Aggies!!

You'd lose that bet. Fightin' Texas Aggie class of 2003 right here!

[Zr8000]

I bet if you ran no exhaust on a stock camaro it would make no difference

[BlaqWhole]

Originally Posted by Village Idiot

CSP did tests that it's not a restriction until 850-900whp it's not costing anyone a race lol

Originally Posted by UnknownJinX

If you lose a race and that's your excuse, I'd be shaking my head and thinking you are saltier than Dead Sea, even without knowing that the pinches don't affect the power unless your car is heavily modified.

What's next? Your engine air filter has a leaf on it? Tires have too many rocks on it? Didn't remove your back seats?

Where exactly did I say that the "pinch section" was affecting performance? I clearly wrote that ANYTHING affecting performance can make you lose a race. Which is true.

Now if you ask me, that unholy ungodly pinch section is loathsome and should be removed immediately. It sucks and I ditched mine. Oh, it's not a restriction until over 850 HP you say? Well guess what, my goal is over 851 HP so it needs to go. Oh, and excuses for losing a race you say? Guess what bud, there are REASONS dor losing races and ANYTHING that affects performance can and will impact the outcome of a race. So stop trying to get fresh like you don't know what I'm talking about.

[10mm]

Nothing new...

[Altered Carbon]

Totaled.

Noooo, it's normal on these cars. I don't have them anymore, but I have a custom built exhaust. However, if they were still there, I wouldn't care.

[gpskinzhut]

Originally Posted by BlaqWhole

Where exactly did I say that the "pinch section" was affecting performance?

Originally Posted by BlaqWhole

ANYTHING that affects performance is a HUGE effect since it could potentially cost you a race. That pinch section is an abomination and should be removed imediately before it costs you a race.

/FreshON

pretty much right there

/FreshOff

[Norm Peterson]

Originally Posted by BlaqWhole

Where exactly did I say that the "pinch section" was affecting performance? I clearly wrote that ANYTHING affecting performance can make you lose a race. Which is true.

Now if you ask me, that unholy ungodly pinch section is loathsome and should be removed immediately. It sucks and I ditched mine. Oh, it's not a restriction until over 850 HP you say? Well guess what, my goal is over 851 HP so it needs to go. Oh, and excuses for losing a race you say? Guess what bud, there are REASONS dor losing races and ANYTHING that affects performance can and will impact the outcome of a race. So stop trying to get fresh like you don't know what I'm talking about.

Unholy and ungodly are descriptions of aesthetic appearance more than they are about actual exhaust flow. A 5% area reduction may look ugly, but it only implies 10% more backpressure per foot over what's probably less than 10% of the exhaust system length. Overall, I think that works out to only about 1% more backpressure for the pipes' share of overall backpressure, and considerably less than that overall assuming the presence of mufflers, resonators, and catalytic converters. I'm thinking that any actual HP increase for that 5% area reduction would be lost in the noise.


Norm

[sandm]

funny all the arguing back and forth over this and a vendor actually did a test that for all intents and purposes can be called apples and apples showing no difference AT ALL.

guess people's opinions or thinks trump an actual dyno graph showing otherwise.

[JKSully]

Originally Posted by sandm

funny all the arguing back and forth over this and a vendor actually did a test that for all intents and purposes can be called apples and apples showing no difference AT ALL.

guess people's opinions or thinks trump an actual dyno graph showing otherwise.

That's the new normal in this country. "Think for yourself" is the new byword and means you can disregard science and facts to make whatever you want (or whatever you read on the internet) be the "truth".

[gpskinzhut]

Originally Posted by JKSully

That's the new normal in this country. "Think for yourself" is the new byword and means you can disregard science and facts to make whatever you want (or whatever you read on the internet) be the "truth".

In large part, thanks to the trash heap that is Facebook no doubt.

[L78toLT1]

Originally Posted by Norm Peterson

I think your 3.5" wide rectangle would only be 0.82" high; a 3" wide rectangle would be 3 x 1.32.

You should probably be thinking a bit deeper than simply outside cross-sectional area (you did consider that inside areas are not based directly on the OD measurement?). But even running with outside 2.75" OD and 8.64" circumference dimensions, a 3 x 1.32 rectangle provides (3 + 3 + 1.32 + 1.32) = 3.96 in^2, or about 85% of the 2.16 x 2.16 square.

I don't blame you for not wading through the round to flat oval math, but I think that the inside area reductions don't happen as rapidly (I think the area loss going from a 2.75" circle down to a 2.2.5" x 3.75" flat oval runs a lot closer to 5%). Feel free to check this.


Beyond that, flow restriction is also a function of how long the restriction is, relative to the unrestricted length. This is at least part of the reason you can get away with dimpling header primary tubes for clearance without losing power until you've really choked the inside area down.

Norm

Thanks, Norm for correcting my math! And yes, I understand that flow restriction is a function of several variables, including the geometry of the transition, constricted length, and undoubtedly several others that I don’t recall as it’s been forty years since I was in Je Han’s Fluids class. A few of the preceding posts, if I’m interpreting them correctly, indicate that some folks are under the impression that crimping, squashing, or otherwise deforming a tube has no effect on the X-section. My post was a poorly constructed attempt to show that deforming a tube does affect the area, and the more you crush it the worse it gets.

[arpad_m]

Originally Posted by JKSully

That's the new normal in this country. "Think for yourself" is the new byword and means you can disregard science and facts to make whatever you want (or whatever you read on the internet) be the "truth".

You have a point, but this isn't a trivial problem when the morals supposed to safeguard the exploration and presentation of facts and science are decaying. One obviously can't and shouldn't reinvent every wheel, but then there's the thorny problem of trust.

To the topic, those dyno tests were done on one (stock) configuration, so they only speak to the fact that stock power levels are not yet where the restriction would take effect, if it ever does. The Engine Masters header bashing test was also very specific, because the section they bashed in ("crimped") was very short.

These two facts leave room for individual guesswork and experimentation, and IMO there's nothing wrong with that.