V8 Rumble

[Dyno247365]

Originally Posted by UncleBob

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.

[534BC]

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

[2.2 Straight six]

Originally Posted by Dyno247365

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.

[drunken monkey]

bikes?

[bluevp00]

Some boat motors are V4, it saves space

[UncleBob]

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

[Dyno247365]

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.

[534BC]

Originally Posted by UncleBob

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?

[drunken monkey]

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

[UncleBob]

Originally Posted by 534BC

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

[Dyno247365]

Originally Posted by UncleBob

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

a coil pack?

[UncleBob]

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.