Tom400CFI

This stuff is AWESOME! It's like trying to have a discussion with Sara Huckabee or Kellyanne Conway.

You used the reliable "peel-o-meter" to measure your 1/2 open cut out gains? Or the good 'ol "butt-o-meter"? This stuff puts our friend Phoenix to shame.


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GREGGPENN

The use of the word power doesn't imply "peak" power. It's the amount of work under given conditions. What planet are you from? I guess what you really meant is you don't tune to maximize efficiency. You control throttle openings and exhaust openings. Got it. For you, the only way you could think to improve engine performance was by varying cut-out opening.


The implication being that you are capable of teaching. My Yelp review will indicate otherwise.

GREGGPENN

Got it! So you can build a big-azz, non-restrictive, high-hp turbo application, you WANT to be able to make that common mistake (from your link):

"A very common mistake made by some performance people is the selection of exhaust headers with primary tubes that are too large in diameter for their engine's state of tune. Bigger is not necessarily better and is often worse."

And...after doing so, offset it with a partially open cutout. Makes perfect sense! You, sir, are a genius!

MatthewMiller

Yeah, that thread is a clusterfuck too. Sam Lin in post #7 there actually got it right. What is written in the quote above (from a different post in that thread) is incorrect as well. If you lose torque after reducing backpressure because your engine is mistuned, then you lost it because the tuning is wrong - not because there is less backpressure. More importantly, that's bullshit. Show me data of an engine that lost "torque" (which is already a misnomer inthat discussion) from a decrease in backpressure after the collector. Please.

As for the rest of that quote of yours, you continue to conflate gas velocity in a primary tube with backpressure. The two are not only not the same, but they are (in this context) almost diametrically opposed! As I've already explained, increased gas velocity in a header primary will actually lower backpressure on the valve in a certain rpm range. In that range, it improves power output. At a higher rpm, where backpressure overwhelms the negative-pressure phase acting on the valve, it decreases power. Again, even in a primary tube, there is never a time when increased backpressure (i.e., reducing the pressure gradient across a system) will improve output (VE, torque, power...however you want to put it).

If you have access to any kind of brake dyno, and a potato or something else to partially plug the exhaust, you have all the equipment you need. Again, you're turning yourself into a blathering idiot by trying to make this stuff way more complicated than it is.

Quoted for more awesomeness. Really? Meaningless?

PSIG or PSIA? If you can't answer that (and obviously you can't), then you are talking straight out of your ***. I've told you twice to learn what those two terms mean and report back, but so far you haven't done so. Willful ignorance is not a virtue - it just means you're choosing to be dumb on purpose.

YOU CAN'T "PROVE TO YOURSELF THAT OCCASIONALLY A DECREASE IN BACKPRESSURE IS MET WITH A DECREASE IN ENGINE OUTPUT, because physics dictates that such a thing cannot happen!!! If backpressure decreases, then you have improved the pressure gradient across the exhaust system, and that will improve scavenging>VE>output. This is always the case, at any rpm, at any load, and at any throttle setting. ALWAYS!

You have been asked at least five times to show the data to support your claim that decreasing backpressure can decrease power. You haven't done so. Again, stop posting unsupported claims here. Post your data or STFU.

ddahlgren

In a desperate attempt to get this back on target lets look at this logically all SBC do not drone. Do any other cars that do not drone have 2 manifolds to Y-pipe to central cat then branch back out to dual exhaust drone? If no what is different with the body? Do cars with duals from engine to exhaust tips drone in any chassis and if only C4 then what is different with the body?

Kingtal0n please do not reply as you are where 90% of this went off track and a worthy thing to solve for all. You offered 0 useful information other than beer goggles full engineering.

Tom400CFI

Yes! F-bodies. More bends. Look how bendy an f-bod exhaust is, but it goes 2 manifolds>Y>cat>intermediate single>muff>two tail pipes and tips.

69427

Every car body type is different. They have different shapes, construction, and stiffness. This means that they all have a different resonant frequency that the bodywork material likes to vibrate at. If you avoid/muffle that particular frequency of the exhaust note, the chances of the bodywork droning is slim to none. If your particular exhaust system allows sufficient strength/magnitude of the offending frequency to emit/radiate out to the bodywork, chances are good that you'll get drone.

MatthewMiller

Not to be pedantic, but it's fairly important to this topic: In a stock C4 (at least a later one), it goes two manifolds > two cats > central resonator (not cat) with common chamber > dual exhaust/mufflers.





I've been a in a lot of different American V8 cars that droned, including F-bodies and lots of Mustangs (different firing order there, too) and one 2005 GTO with Kooks headers and I-don't-know-what exhaust. So it isn't unique to C4s. My guess is that any engine on any car could drone if the exhaust is the right length and diameter. By extension, probably every system out there can drone a bit at some rpm, but the general length of pony-car exhausts and the firing spacing and number on a cross-plane V8 makes it likely that the drone will be focused in the cruising range of rpms, and that it will be especially obnoxious in tone. Back in the 1960s, when muscle cars had top gears of 1:1 and gear ratios in the high 3s and 4s, nobody noticed because everyone cruised around at 3500rpm or more. The quarter-wave resonator is probably the best way to address it, and of course the quieter the exhaust is overall and/or the more the cabin is insulated from the exhaust sound, the less loud it will be.

Kingtal0n

aww guys you shouldnt have. thank you.

i love you too

Kingtal0n

Can I just say that this technology does exist, that cutout was $28 shipped from ebay and it changed the entire car around. I am sure other cutout owners would repeat similar experiences. The "exhaust drone" and exhaust modifications go hand in hand, because you want to fix the drone by altering frequencies of sound in the system right? So by cutting it up and adding parts and pieces to reflect exhaust gas, you will certainly be changing it in some way. Because the only thing we can do without actually measuring the sound in the exhaust system and designing a part to dampen that frequency is to blindly modify our systems until satisfied, and let me tell you from experience it doesn't take long once you get handy with a mig/tig welder to put something really satisfactory together on every car.

So conclusion: The best exhaust is one which would increase in flow while maintaining the same velocity as engine RPM increases. Pretty sure thats what I said in the first post.

Kingtal0n

my favorite part. I am not sure you realize this but the question is regarding measuring a pressure without any reference. It's like you yourself have forgotten that the pressure on our gauge is useless without having an atmosphere to sample.

MatthewMiller

Yes, and that is wrong. It was wrong in your first post and it's wrong now.

I have literally never typed this to anyone before, ever: you are one dumb ************. You are so dumb you don't even understand that you are dumb. And worse yet, you have a smug and self-righteous attitude about the dumb crap that you continue to spew into this thread.

It was okay when you said this the first time, because we all say wrong things sometimes. But those of us with more clue than attitude are happy to be corrected and learn the errors of our ways. I have tried to elicit your understanding of why this is wrong multiple times, with a question to lead you to the knowledge: what is PSIA vs PSIG? If you weren't so intent on being a smug, dumb, ******* to all of us, you'd have looked that up by now. You'd have found that one is "pounds per square inch absolute" and the other is "pounds per square inch gauge." And you'd now know that PSIG is, by definition, a pressure measurement referenced to atmospheric pressure (which is why the gauge always reads "zero" when it isn't measuring anything). And you would now understand that the gauge you use to measure exhaust pressure most certainly does reference atmospheric pressure.

Tom400CFI

Edit for this: I LOVE ^this post. LOVE IT. That is hitting the nail squarely on the head.



I never questioned the existence of exhaust cut outs...our 1910 Hupmobile has that..."technology". What I DID say was...ah, never mind. These Huckabee/Conway arguments are pointless.

But I can say this...when I close the exhaust cut out on the '10 Hup? OMG, the thing turns into a LOW RPM TOWAK MONSTAH!!! Have you let Phoenix know about this Tork Tuning Secret? Maybe his car could climb "inclines" on the highway if he installs a exhaust cut out so he can close it?


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Kingtal0n

Oh so lets all be clear. You are telling me that if I have an engine,
ANY engine,

and I install an exhaust system with an increasing diameter, set to increase as RPM rises, thus maintaining some superior velocity throughout the rev range.

That I wouldn't make more torque throughout the rev range?

Just making sure

Obviously: "Exhaust system" includes all part of the exhaust from head to tail.

MatthewMiller

Yep, that's what I'm telling you. You can take the whole damn exhaust system OFF after the collectors and you will have the most "torque" or power or VE at every speed and every load possible.

EDIT:
Holy ****, you're right! We have to get these two together in a bar. I'll buy the first round, just so I can hear their conversation. But I want video to document the awesomeness. The "perfect tool" and the "uber-tech exhaust cutout" meet the "invincible TPI intake" and the isobutanol! They might even fall in love...

Kingtal0n

SO what do you think this author means by,

compromise? What is it we are compromising and how is "acceptable across the powerband" based on our exhaust system?

Kingtal0n

And you are saying that if I have this




On an engine by itself, with no exhaust system, that it will produce more torque and horsepower throughout the rev range than with an exhaust to collect and gather the hot gas molecules to flow together for a distance?


You must see how this is ludicrous. Yet this is what you insist.

edit: I think I see the error. You are assuming that the collector and anything before a collector (header) is not part of the exhaust system. And then in your mind, the collector is actually after a long series of exhaust tubes, tuned to performance already. Well my friend this is part of the exhaust system, and if removing whatever comes after improves performance it is because the exhaust system is well designed leading up to the collector.

Kingtal0n

This is a stock 5.3L truck manifold



I have dozens of these.
So if I put them on a stock 5.3 and dyno the car open collector.
And then add an exhaust system between 2" and 2.5" diameter.

The engine will lose torque with the exhaust system installed?
Just to be clear again


Here is something Showing smaller diameter exhaust tube is increasing torque from idle to midrange. It was a random search, I am sure there are many many others like it. How many do you want me to find?

https://www.sandersonheaders.com/let...technical.html

GREGGPENN

Even more so, after this thread, I'm convinced the solution isn't bends. All systems have SOME bends anyway. I still think it's that you should avoid box mufflers. That the inside of a Corsa is more like a bullet muffler did it for me. Of course, I also recognize what's being said about 1/4 wave strategy too. It's just (if you leave that tech aside), complaints line up with ovals/box mufflers IMO.

I would also suggest "retuning" a drone problem by purposely changing to a different (probably smaller) bodied muffler....or move "back" to no muffler, a good "H"/"X" and cats before trying another type of muffler.

If that doesn't work, it seems "we" have already eliminated all box-style mufflers EXCEPT Corsa and the Magnaflow x-muffler series.

As for shape of the car, I doubt drone is unique to the C4...though if it varies somewhat, I'd look to a combination of the F40 shape AND that it's an open hatchback. ANY vehicle with an open cargo area transmits tons more "road/exhaust" noise IMO.

GREGGPENN

How did we get from stating: an engine -- with a properly designed header -- doesn't need downstream piping
-- to --
posting a picture of a poorly designed bum-fkd MANIFOLD (with non-existent primaries) that NEEDS some kind of pipe just to serve as a bastard secondary collector
.....
while concluding that a HEADER PRIMARY SIZING chart has ANYTHING to do with exhaust pipe selection?

Once again....BRILLIANT!