V8 Rumble

*sigh* everytime I pop my head in here, you guys make my head spin with knowledge, try to tone it down this time, please? I'm still learning, and I haven't even taken physics yet. That's a good idea I should take physics...err, here's the question. Why does a V8 make a rumble and lower pitched rev then any other engine (even the Viper V10) ?

I'm not really sure, but it could be due to displacement. American V8's are very large engines compared to import V8's and are usually the same size or bigger than most V12 engines. The bigger explosion in the cylinder, the deeper the sound. It could also be due to exhaust design, people are used to hearing the V8 rumble, so manufacturers try to create as much rumble as possible.

But that's just my guess, it could be a combination of displacement, exhaust design, head design, and cylinder angle that makes the engine produce a certian sound.

it's to do with the pitch (angle) of the cylinders, bore, stroke, the engine design and things like the firing order.

different engines have different charecteristics.

simple enough?

it's to do with the pitch (angle) of the cylinders, bore, stroke, the engine design and things like the firing order.

different engines have different charecteristics.

simple enough?

Alright...now I want the info the hard way. I'm aspiring to be an engineer, or atleast I want to study it so I need some serious exposure to this stuff. V8s fascinate me. They're unmistakable when you hear them.

i think that the noises made by engines is from the valves opening, letting the sound of the explosion echo out, and slamming closed again. the design of the valves wold have an effect on the sound. also, lower idling engines tend to rumble more IMO.

its going to be more about the bigger explosions of the cylinder, thats a pretty good answer..also, the exhaust has alot to do with it. ive heard plenty of V8's that didnt have a bit of rumble. i had a 77 mustang with a 302 and it didnt rumble a bit. of course, it still had stock manifolds, stock cat and muffler. my 71 mustang, it has no cat and its true dual exhaust with what looks to be some stock glass packs. rumbles pretty good. since youre referring to a "rumble" its obvious its the effects on the exhaust youre hearing, plain and simple. of course how that sound gets to the exhaust has plenty of stipulations that determine that effect.

you want a plain and simple answer? cause and effect my friend! :lol:

If it were simply the displacement or layout, then a 4.3 GM V6 would sound the same as a 5.7 V8. They are the same engine with two cylinders lopped off. Same pistons, head design, everything.

It has to do with the number of times the exhaust receives pulses from the valves and their intervals. The exhaust gets 4 pulses for every revolution in a V8, but only 3 in a V6 and 2 in a 4 cylinder. It also has to do some with the layout. An inline six sounds different from a V6 because inlines typically share one exhaust manifold, while a V6 has to have two.

If it were simply the displacement or layout, then a 4.3 GM V6 would sound the same as a 5.7 V8. They are the same engine with two cylinders lopped off. Same pistons, head design, everything.

It has to do with the number of times the exhaust receives pulses from the valves and their intervals. The exhaust gets 4 pulses for every revolution in a V8, but only 3 in a V6 and 2 in a 4 cylinder. It also has to do some with the layout. An inline six sounds different from a V6 because inlines typically share one exhaust manifold, while a V6 has to have two.

very good point. i guess it depends on what Dyno247365 meant by rumble. because depending on what kind of exhaust setup you have, you can have a very mean sounding V6. so did he mean deep rumble in general? or the actual loping extremely distinctive sound of a V8?

I'll be specific as requested, not just the idling rumble, but think of the noise it makes getting to and at WOT. I don't know the term for the engine in motion...when you're running the V8, driving it.

It must have something to do with power pulses per (time) or rpm. A v-8 has a definate sound compared to a 12 or a 6, noting it is usually a dual exhaust and may have to do with the uneven firing out of each bank. I have lots of experience with 12's and have heard numerous different sizes of 12's and 8's.

There's something appealing about that sound and a larger v-8 seems to sound better to me. One of my favorite sounds is 5 or 6 blown v-8's on a tractor that run nice.

Now, my favorite smell, hmm.

Don't forget the very different and distinct sound of a V8 with a flat-plane crank. Sounds more like two high-strung 4 cyclinders in harmony. Or four Harleys in a row. No rumble....more of a scream. Odd, to make a V8 sound more like a Hayabusa...but it'll net you better crank balance, higher redlines, and lower reciprocating weight, due to not needing excessive counterweights. I want one.

i don't remember the name of the company, but a over here they've made a 2-litre V8 by efectively "splicing" two 1,000cc hayabusa engines together.

i don't remember the name of the company, but a over here they've made a 2-litre V8 by efectively "splicing" two 1,000cc hayabusa engines together.
you mean two 1300cc engines. I've seen the video of that. Very cool. over 350hp with stock busa internals.

another cool one is the drysdale bikes, splicing two FZR400 engines for a 750cc V8 that revs to 16K+ RPM's. there's a sound clip of it on their webpage.

If I had a lot of money to throw away, I'd buy one in a heartbeat!

i thought they used older 1,000cc engines, no?

i don't have the article to hand, but from memory it said the V8 block was a 2-litre.

google is your friend

http://www.radicalextremesportscars.com/range/sr8/sr8.php

2.6L engine.

damn you!

my stars are purple. i win.

yes, the lads at Powertec (http://www.powertecracing.com) are making V8s as though they were making biscuits....take (2) four-cylinder engines, (1) reverse mounted cylinder head, modified block, custom ground camshafts, custom crankshaft, custom engine management, add fuel, and you have Formula 1 performance at Daimler-Chrysler price! Damn them....I wanted to do it first.

A flat crank definately sounds different. I can't remember the last place I heard one. Do 2 cyclinders fire at same time?

it has to do with the order the cylinders fire in.
i'm not sure of the order, but it makes a different noise than an 'american' design V-8

A normal 90 degree v-8 has 2 cylinders up at same time, going to a flat crank ould have 4 cylinders up at the same time and 2 must be fired at once, sounding like a "pair of inline 4's"

isnt that rather inefficient tho?
wouldnt it be better to take two inline 4 cranks and connect them, but rotate one 90*
that way, the firing would be more uniform

Yes, I think so. That's probably why all v-8 are 4 different throws on the crank. I can't for the life of me remember what the idea was with going to a flat crank in a v-8, I haven't heard many, but if I remember correctly were in pulling tractors and had a very distinct sound that could not be mistaken, but they never seemed to catch on very well.

side to side balance would suck...

and yet is still there in a ferrari 360 and the V8 in a TVR.

yes, the lads at Powertec (http://www.powertecracing.com) are making V8s as though they were making biscuits....take (2) four-cylinder engines, (1) reverse mounted cylinder head, modified block, custom ground camshafts, custom crankshaft, custom engine management, add fuel, and you have Formula 1 performance at Daimler-Chrysler price! Damn them....I wanted to do it first.
OMG bro I don't know which one of your posts I want for my signature. They're so funny

and yet is still there in a ferrari 360 and the V8 in a TVR.
A flat crank V8?

yup.

Don't forget the very different and distinct sound of a V8 with a flat-plane crank. Sounds more like two high-strung 4 cyclinders in harmony. Or four Harleys in a row. No rumble....more of a scream. Odd, to make a V8 sound more like a Hayabusa...but it'll net you better crank balance, higher redlines, and lower reciprocating weight, due to not needing excessive counterweights. I want one.

That's right, I forgot. No big counterweights and no bob weights . The two end pins are lined up right? and the 2 center pins?

exact same crank geometry as an I4, just two con rods per journal instead of one

what would be really interesting would be a big bang V8 in such a config. 1 & 7 would fire at the same time, as would 3 & 5, 2 and 8, 4 & 6

Basically a really big V4 engine

That's right, I forgot. No big counterweights and no bob weights . The two end pins are lined up right? and the 2 center pins?

what pins? gotta picture?

exact same crank geometry as an I4, just two con rods per journal instead of one

what would be really interesting would be a big bang V8 in such a config. 1 & 7 would fire at the same time, as would 3 & 5, 2 and 8, 4 & 6

Basically a really big V4 engine

Give me an example of a car with a V4. i can't remember the last time I saw one.

Bob means an inline 4, where the two end rod pins are up at the same time, the two center pins should be down.

Give me an example of a car with a V4. i can't remember the last time I saw one.

i think Saab made them in the fifties.

bikes?

Some boat motors are V4, it saves space

no, I'm talking about "big bang" motors. Its something you only see in very serious race applications.

A I4, for example, 1 and 4 are at TDC at the same time. Normally you would have them fire 180 out of phase to spread out the power pulses and reduce vibration.

On a "big bang" engine, 1 and 4 are fired at the same time, as are 2 and 3, so instead of 4 power pulses per 720 degree's of crank rotation, there are only 2.

The reason they do this is to increase traction. The less power pulses, the more time the tire(s) have time to recover from power pulses causing traction loss.

Pretty much all the GP bikes use this method these days. Some are even playing with a combination of big bang and traditional firing order. For example firing 1 and 4 at the same time, but keeping 2 and 3 offset. The reason for that was to improve engine longevity....they were breaking stuff too often with the big bang engine and losing races.

It doesn't reduce your power in any way, just delivers it differently to the tires.

btw, it completely changes the sound of the engine. since its halving the number of power pulses, it makes it kinda sound like an engine with half the cylinders....but not quite. Very unique sound

Anyway, thats why a "big bang" V8 would sound kinda like a really big V4, and it would apply power like a V4

I need the lope like I need more cowbell. Big bang engines sound cool though. Thanks everyone for thoroughly explaining that it's the firing order, the number of cylinders and the displacement of an engine that attributes to the sound.

no, I'm talking about "big bang" motors. Its something you only see in very serious race applications.

A I4, for example, 1 and 4 are at TDC at the same time. Normally you would have them fire 180 out of phase to spread out the power pulses and reduce vibration.

On a "big bang" engine, 1 and 4 are fired at the same time, as are 2 and 3, so instead of 4 power pulses per 720 degree's of crank rotation, there are only 2.

The reason they do this is to increase traction. The less power pulses, the more time the tire(s) have time to recover from power pulses causing traction loss.

Pretty much all the GP bikes use this method these days. Some are even playing with a combination of big bang and traditional firing order. For example firing 1 and 4 at the same time, but keeping 2 and 3 offset. The reason for that was to improve engine longevity....they were breaking stuff too often with the big bang engine and losing races.

It doesn't reduce your power in any way, just delivers it differently to the tires.

btw, it completely changes the sound of the engine. since its halving the number of power pulses, it makes it kinda sound like an engine with half the cylinders....but not quite. Very unique sound

Anyway, thats why a "big bang" V8 would sound kinda like a really big V4, and it would apply power like a V4

I think I get it, same crank arrangement as a inline 4 , but different cam and firing arrangement.

The ignition is worked out how? twin tower coils?

wouldn't it just be differerent positioning of the contacts inside the distributor?

I think I get it, same crank arrangement as a inline 4 , but different cam and firing arrangement.

The ignition is worked out how? twin tower coils?

DIS would be the simplist answer. Pretty much all bikes are DIS, so you wouldn't even need to do anything for the ignition.

Attempting to make that work with a distributor, however, I think would be a lost cause. If you're going to spend all that money making such a unique motor, step up and buy a real ignition system :D

DIS would be the simplist answer. Pretty much all bikes are DIS, so you wouldn't even need to do anything for the ignition.

Attempting to make that work with a distributor, however, I think would be a lost cause. If you're going to spend all that money making such a unique motor, step up and buy a real ignition system :D

a coil pack?

correct, DIS stands for distributorless ignition system. Which is a very bad name for coil packs, one coil per 2 cylinders.

COP (coil over plug) is the reference name when its one coil per cylinder.