Adrenaline_Z

Just a thought, not really a question.

Ever think about what we're actually hearing through the pipes? Is it primarily
several explosions per second resonating down an exhaust system through
closed valves?

Sounds of valves smacking valve seats? Pulses of air escaping the chamber
at high speeds? A little bit of everything combined?

What ever the mix, the "big guy" upstairs knows the way to my heart.

gun5l1ng3r

I don't know what the answer is, but I do agree with the last part!!!

Ric

I think that pretty much sums up what makes the noise. Now, how it gets bent, shaped, and molded into the mean American variety of V8 sounds depends on things like exhaust pipe size/length/# of bends, mufflers, firing order, heads, cam, valve size, exhaust port parameters, header specs, yadda-yadda-yadda....

2002_Z28_Six_Speed

iTrader: (19)

Exhaust sounds interesting but it is so different from the true nature of the engine: a continous and violent explosion.

MadBill

Actually, except when detonation ocurrs, a combustion event is a very rapid burn, not an explosion. The high pressure pulse (50-100 psi at WOT) of escaping exhaust when the valve opens causes the noise. You can verify this by screwing an air fitting into the plug hole, applying 100 psi and then tapping the exhaust valve open with a hammer and soft punch. (with the manifold removed)

2002_Z28_Six_Speed

iTrader: (19)

So you are saying the sound comes from the rapid escape of heated/compressed exhaust gas? The actual burn doesn't make a lot of noise?

MadBill

That's correct. The combustion is complete before the exhaust valve opens, so if there was any noise to speak of, it would have stopped by then. The pinging/knocking sound you hear when an engine detonates from bad fuel or too much spark advance is caused by a very small portion (usually <10%) of the mixture exploding. If the whole combustion event was an explosion, it would be 10X as loud, and wouldn't change much with an unmuffled exhaust.

Adrenaline_Z

MadBill,

I've used compressed air (100 PSI) to change valve springs. Some of the
retainers were stubborn and I had to use a soft faced mallet to tap the
retainer loose.

Those pops are pretty loud through the manifold.

I'd also like to edit my definition of "combustion sound". It's not an explosion
(instant spike of pressure), but rather an expansion of gas in a somewhat
controlled manner as you stated.

I can also hear sounds of valves, or lifters. There is a distinct sound between
mechanical and hydraulic cams that sticks out (especially at idle).

As far as tailoring the sound it could be anything from engine load, to atmospheric
conditions.

We could turn this into quite a novel!

Patrick G

iTrader: (14)

If you've ever heard a Spin-Tron machine spin up a motor to test valve-train stability, it sounds just like an engine at WOT. All it is, is an electric motor spinning a gutted motor assembly. Lots of the noise we hear is valve-train, air-pumping noises.

Ari G

iTrader: (25)

I thought the main diffrence between LS1 and LT1 sound with open system is the exhaust port shape D on Lt1 vs O on LS1?

300bhp/ton

Doesn't the LS1 have a different firing order to the LT1??

98Z28MASS

iTrader: (6)

Yea dont know the order but I am almost certain it is different. Plus I think the aluminum ls1 block adds to the difference in sound too.

ArKay99

iTrader: (1)

There is one point that has been debated here and it's the difference between a controlled burn and an explosion. An explosion is not an instantaneous event. It is the 'explosive' burning at a very high rate. For instance C4 'burns' at 20,000 feet per second. I'm not sure of an air gas mixture's rate of burn, but it must be much less given that optimum timing is based on some number of degrees of ignition before TDC and the time it takes for the crank angle to reach it's optimum torque angle. Also, I recently had a fouled plug that manifested itself as a 'shotgun blast' due to misfire out of my exhaust because the a/f charge exited the cylinder and wasn't burned there but somewhere in the header. It was a MUCH different sound than the exhaust leaving the cylinder when burned at the proper time. Also we should keep in mind that the exhaust gases escape at a slow rate at first, as the valve starts to open, then faster until the valve opens fully. So the wavefront attack is logarithmic in nature and not instantaneous.

Velocity

Yes, it does.

LS1 is 1-8-7-2-6-5-4-3

as opposed to the LT1 and traditional SBC, which is 1-8-4-3-6-5-7-2.

The Alchemist

iTrader: (19)

Yeah, to continue the discussion of 'explosion' vs. 'burn' listen to a top fuel (80:20 Nitromethan : Methanol) compared to a gasser. The nitromethane burns at a much higher rate and sounds more like an explosion than a burn.

The greatest thing I've ever heard is the first time I was standing in the pits and a top fuel funny car started up doing his morning tuning session. The sound is intoxicating much less the vapors that burn your eyes and lungs.

hammertime

iTrader: (1)

If you think about it, once you close the throttle at high speed you're not getting any fuel anyway. The sound does change a bit because of the relative low volume of air flowing through the closed throttle, but the sound is mainly the pumping of air into and out of the engine.

Years ago, I ran out of gas in my old car with full lengths and dual exhaust. I was suprised how similar it sounded, even with no combustion at all.

blackz93

iTrader: (2)

True.

On a stock car, you hear "boom boom boom boom boom boom" as it's idling. Is that everytime the motor makes a revolution? It definitely doesn't seem to be the cylinders firing, as it's too slow.

ArKay99

iTrader: (1)

I believe that is the 2 cylinders on bank 2 that fire one after the other, every OTHER revolution.
As stated above:
LS1 is 1-8-7-2-6-5-4-3

as opposed to the LT1 and traditional SBC, which is 1-8-4-3-6-5-7-2.

Captainofiron

iTrader: (1)

Yep sounds like a gun going off. There is no sound like a cammed SBC. Not to jack the thread but I saw a Viper GTS the other day, and I always heard how crappy they sound, but man I was really surprized. It sounded horrible. It sounded as meanacing as a Toyota tundra. It was loud but that is it. I heard the reason the exhaust sounds so crappy is because the Dodge engineers cant figure out a way to tune the exhaust of the V-10. Interesting

hammertime

iTrader: (1)

You are half way there. A V8 has two cylinders that fire consecutively on both banks. On an LS1, it is split at the end-beginning of the firing order.

1-8-7-2-6-5-4-3

It is easier to see on a Gen I/II SBC, as it is buried in the firing order, not at the end.

1-8-4-3-6-5-7-2