what causes a different engine note?

[Asa]

crossing out obvious things such as the exhaust system from the header back, and a lumpy cam, what makes engines sound so differently?

it should be a good number of different things, but i would think that the most important ones would be:
material of block and head(s) (this being the most important due to how the sound vibrations travel through it)
firing order
displacement

others would be stuff such as the head design, OHC Vs OHV

anyone got any info?

 

[80broncoman]

I have never figured it out , but have thought about this subject much over the years.
My 7.3 diesel used to have a 2 1/2 dynomax muffer on it and it was quiet, as in silent. Well the muffler got to be about 7 yrs old ans rusty so I cut it off. So I started it and let it idle. not loud at all. so for a temp solution I grabbed some flex pipe and installed the exh system sans muffler. Idle quiet, 60 MPH cruise quiet, but it would rattle your teeth if you have the pedal down. Loudest damn thing I ever heard. The only big difference between is the compression. I am still not sure why even the smallest non straight thru muffler makes the loudest engine very quiet.

 

[Inline6Merc]

A diffrent carb or carbs can make a differance in sound. Porting helps alot too.


Later,

Curtis

 

[63stl_comet]

Engine layout has a affect on the sound. I have a Subaru with a horizontaly apposed 4 popper that sounds mean. And some of the older V12's that where like 16 degree banks have a sound of there own.

Brian.

 

[addo]

Squareness ratio. Along with cam profile, this shapes the sound. Also, some resonance in the engine bay oughta be figured in.

 

[aussie7mains]

Its all down to our old friend HEAT.
When hot air hits cold air it makes a lot of noise so QED
The diesel at no and low loads quiet, NO HEAT.
Same with jet aircraft, the way they got them quiet was by using turbo fans so only cool air used to move aircraft.
A7M

 

[Anonymous]

I think it has a lot to do with how much cylinder pressure is present when the valve is opened...

Why does a 2.3 liter 4 valve motor sound so different from a 2.3 liter 2 valve one?

 

[Anonymous]

I'm around alot of SAE formula cars normally. One of the biggest things that makes them sound different is the headers, different length tubes determine when all of the gases from each cylinder meet up into one pipe and that can make them poppy or smooth. Most teams run the same exact engine and if not, they are all very similar and same size and restraints...besides for those that use the single cyclinder poppers... on ours, our guy had alot of experience and ran some numbers and made some really sweet sounding headers. Just my two cents.

Brandon

 

[aussie7mains]

Linc 200, What causes the cylinder pressure?
Heat!
A7M

 

[Anonymous]

Yes, heat of course.....but also valve event timing.

Rod/stroke ratio plays a part

 

[Anonymous]

dont forget compression ratios...

 

[Anonymous]

Porting makes a BIG difference in sound. That was one of the biggest things I noticed when I put big valves in and ported my 2.3 turbo.

 

[Stubby]

I think it has alot to do with pressure waves, and how we handle them. Low rpm, low pressure high rpm, high pressure, high velocity.
Compression and mixture seem to make it more crisp. On engines that are too rich or low comp are more mellow or lazy sounding reguardless of volume.

The tone seems to be affected by dia and length. Kinda like a musical instrument. Trumpet vs tuba. I have seen exh tips totaly change the sound of an exh sys.

The loudness is greatly due to the volume and velocity of air. Also effected by the crispness. (popping)

The way we handle these pressure waves also effects the tuning of your engine, and also the powerband. Long tube headers more bottom end short zoomies, more top end.

I think the best sounding engine I have ever built was a 302 for an SCCA AS mustang. It had an X pipe back when they were a new thing, no mufflers, when I first saw and heard it screaming down the front straight at Texas World Speedway I was awestruck. It sounded like an Indy car. It had a high pitch and it was beautiful throaty tone when driving thru the pits. That was a big bore short stroke engine or oversquare bore and stroke.

 

[Stubby]

I will also mention that the lower the tone the quieter it sounds, The higher the pitch the louder it sounds.