Exhaust Poll

Sh0velMan

I think.... I think you guys don't really "get it" when it comes to my car.

Maybe if you saw and heard it in person? I think you have this impression that the car sounds like a small displacement Honda 4 cylinder with a straight pipe on it...

It doesn't.

Is there rasp? Yes, I can detect the sound of the rasp amid the other exhaust noises, but it definitely doesn't sound like yard equipment.

I mean, I've posted a video in my build thread of revving the damned thing, if all you hear in that sound clip is rasp, then I can't help you. My car is loud and in your face, and if people are laughing at the way it sounds, well, good for them. I'm glad I could give them something to laugh about.

And what's this about power? I'm losing power because I don't have extra pipes hanging off of my exhaust? Do you just make this stuff up as you go along? lmao. Do you even understand what causes the rasp? The mere act of acoustically cancelling out the pulses that generate the rasp can cause back pressure in the exhaust system. You're far more likely to see a power dip at specific RPMs WITH extra resonating chambers attached than you are with a straight pipe as 'canceling out the rasp' is breaking up an acoustic wavefront that helps with scavenging. I assume you know what that is, at least, and why you would not want to do so? This is exactly why you have to be careful with resonance alterations that close to the engine and why I will do no such thing.

THAT is fact, THAT is science. I don't want to make this an acoustics and fluid dynamics debate thread, it's already ridiculous enough.

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chii370

rasp isnt that weed whacker buzz noise. thats just ..... shitty sounding exhaust. you only hear rasp when you let off the gas JUST as the rpms are about to the 1k-500 level.

heres a raspy **** example. Nismo 370z with ARK high flow cats and ARK DTS exhaust with techno tips - YouTube

heres a non raspy **** example of the same exhaust

ARK Performance Nissan 370z DT-S Exhaust - YouTube

listen for when the engine RPM's drop from rev, to almost idle. its that noise thats like someone sticking there toung out and blowing.

and good for you, you get a bro high five. im not lecturing you about THIS car. Im lecturing you about ALL cars. physics just so happen to apply to all of them. just sayin. so stop acting like a know it all and do the research for yourself. Im sure for your super ultra 1337 "in your mind" build only useful on a track that about 2% of the community would ever care to do will be awesome. but im talking about the real world, where dyno numbers arent the only thing that matters about owning a vehicle that most of us drive daily. derp

Chuck33079

Are we discussing rasp, or the "VQ hiss"?

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Sh0velMan

rofl

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chii370

wow theres an aweful lot of other cars besides Z's and G's that must use the VQ then. I should go inform them that we have solved it. its gotta be the "VQ hiss" since its obviously the only engine ever made that does it. trademark that ****. I get whats being refered too as rasp here now, the annoying buzz fart can sound? never really put a word to it. just **** exhaust. my bad there.

and just sayin, I care about that. as well as any other annoying/bad noise an exhaust makes. regardless of your reasoning, point is gaining a little HP and making your car sound like **** is a giant fail imo.

Sh0velMan

.. are... are you serious?

This entire time, you think we're talking about the HR/VHR 'hiss'????

That's a phenomena that's been around since the HR and is caused by the VVT system on the exhaust side.... You can get rid of that by running a simple resonator (glass pack) in the exhaust stream.

The grown ups are talking about exhaust rasp during WOT use caused by supersonic wave fronts within the exhaust stream as the exhaust valves open.

At least, this grown up is. I respect Synolimit's grounding in the subject, so I am assuming he is referring to the same thing.

Not the stupid hiss. Who cares about that ****.

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synolimit

Well I have LTH also so I know what It sounds like. It was nothing but rasp as I'm sure yours is also. Reving a car doesn't count. I heard yours under load and my statement stands.

If you have rasp you're losing power, period. Read Chii post again. All that is from Tony at motordyne. Do you think tony makes more power with his ART pipes and CBE over straight pipes and other CBE because he lucky? No he's not lucky. He's smart and combated the rasp and drone with a proper setup using Helmholtz resonators which you don't have and I do. Guess what? I don't rasp or drone ever, and to boot because of the way a Helmholtz works with storing air pressure and acting as a vacuum when the flow has a gap in it, I bet I make more power than you too. The fact that you're talking about back pressure automatically makes you unqualified for this conversation. You need to read more and learn.

PS your science is wrong because your source you got it from don't have an understanding and years after years people are just passing BS along and down the line.

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13 370z-

chii370

well your right about one thing shov. a resonator too close is bad, but a resonator further down stream is not, where it helps create a negative pressure zone. You would also want it as far away from the originating source anyway to help dissipate the sound waves before they even GET to the resonators for frequency cancel. So I see no reason at all why it would rob power unless its improperly designed with too little flow, too little velocity, or improperly shaped entry and exit to the resonating chamber that causes turbulence. I would like to see something to back that claim up, as in my personal experience thats just not true. cats sure, resonators, no.

synolimit

But you do realize a Helmholtz isn't an inline resonator right? Two different things.

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13 370z-

chii370

no idea what Helmholtz is, was just speaking from a general standpoint. wasnt arguing with you, was arguing with shovelman. but it must be said that both parties are right on various points. Im saying this through a mostly lifetime of experience of being involved with building cars since i was old enough for my dad to force his mechanical way of life on me. not just from 100 dyno runs with a Z. these principles apply to every car, its science/physics as we have both stated. If you wanna make a useless million HP noisebox go right ahead, by all means its your right to do so. But passing on your dumbfuck logic to people who DONT understand the science behind it will cause people to follow in your tracks unknowingly and be disappointing in the results for their daily driving car. theres a difference between doing things the right way, and doing things the 1% way that also just so happens to work. dont know about you, but im humble enough to say i learned something today.

synolimit

Just google. It's also whats welded to the art motordyne test pipes, the guy you quoted...tony.

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13 370z-

forza370z

Wow... Absolutely some good readings here!! I tend to agree with synolimit's theory on Helmholtz resonators. I thought they are mainly used to cancel out the drone, but this "restore air pressure" thing totally makes sense to me. And that's why it makes the HKS Hi Power THE best exhaust out there because it has Helmholtz resonators! JK JK...

I also agree with Chii on the exhaust piping diameter theory. The bigger piping and less restrictive exhaust systems aren't always good for NA cars. It's not like the bigger the better. It has a limit. I learned this in a hard way. 2.5 inch piping is close to the optimal for the NA setup on our car.

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Sh0velMan

Wow.

Okay guy.

Having a "vacuum" chamber hanging off your exhaust will improve scavenging, but also cause a flow inversion, so it's great for low to middle RPM range but does nothing positive for high rpm operation, which is all i care about.

Of course a vendor is going to say that their expensive new product is great in every way.

I can tell you right now, you don't make more power, but it doesn't matter. Bring your money down here and we'll set up on a mustang dyno back to back if you really want to 'bet' otherwise lets leave size out of this.

Fact is, you've bought one of the least engineered and cheapest produced exhausts, then butchered it up with extra tubing, then paired it with the lowest-flowing longtube headers available, and now are preaching to someone who has spent far longer in the search for power in this platform. I'm done with the subject, do what you want, I'll keep doing what I'm doing.

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chii370

so you proved my point. this is beneficial for you. but most of the Z community doesnt have their car at 7500 rpm all day long every day. im sure you would be very interested in race cams too "if it wasnt for vvel" as they completely destroy every day usefulness of a car in benefit to one very specific scenario, racing. the whole point of the argument was showing the science behind it for what is better OVERALL, not just for you you you.

and just to toss this out there, price doesnt matter. my ark was 1700. is it 1000 better than some of the cheaper exhausts? no. is the amuse 3000 better than my ark? no. it doesnt work that way. its not a ******* scale. yes their are engineering differences, but aside from build material, quality, pipe diameter, shape, bends, welds and so on they are all functionally the same. and no ones to say a MORE expensive model couldnt in fact be out performed by a less expensive one. thats a rich douchbags way of looking at things. just move your slider from one side of the bar to the next. lemme just buy all the most expensive parts and that = im the fastest best mechanic in the world. durp. I can see you do EXACTLY that, as you bought the nismo R tune intakes "twice the price means better". guess what, the stillins gen 3s are cheaper and they perform much better. so shut up. according to your logic they are not engineered as well. due to price.

Sh0velMan

Actually I have those intakes because they were sponsored to me by Nissan Motorsports North America, I paid well under what G3's run. (Less than half, actually) If I were buying intakes today, I'd be getting G3's.

Try again?

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