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How's It Sound?
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Author:  nomad [ Mon Jan 09, 2012 10:53 pm ]
Post subject:  How's It Sound?

We've all got our pet peeves regarding questions from other rodders. Mine was always the "How's it sound question?" My reply was always to the effect, if it's got open headers it sounds great.

You all know I've come to this carb thing later in life than most. So, it's been a bit of a surprise that "How's it sound?" really does seem to matter. I began to notice this with all the dyno testing we've done lately. It really became apparent at the Carb Challenge. It was easy to tell which pull was was going to be better than some others.

Now I've noticed that I pay attention to the faster cars as they go by my pit area. Not all that many sound like the engines are happy. Some are downright ragged, cars I would think should be better. Cars that probably have boutique carbs on them.

You other newbie carb fiddlers noticing this, too?

Author:  shrinker [ Mon Jan 09, 2012 11:34 pm ]
Post subject:  Re: How's It Sound?

http://www.youtube.com/watch?v=x-jMsrl5EIw
This is a 417 cube Cleveland through the mufflers. The engine makes over 780hp with a 1042CFM SmartCarby on it. It is regular street driven, its not a race car. It makes 300hp at the wheels in top gear at 60kph( 37mph our speed limit). It runs at 40kph (25mph)in top gear (manual not auto) without snatching and pulls away with WOT. It passes noise laws and passes emissions. The engine was first built with a Dominator on it and it didn't have this sound, it was dull and bassy. It made similar power but had less response, used far more fuel and couldn't pass emissions.
Listen to the sound how it changes from the burnout and the RPM before the launch and compare it to the sound as it goes down track. You can hear the other car, its a dull bass sound (conventional). The sound in the burnout and pre launch is smooth and snappy, the sound during the run is sharp and supersonic. We have chassis dynoed it with pipes on pipes off etc it makes no difference it kills your ears.
During the run the sound is a sharp hard crack, Its got this crack at basically all revs when under serious load. That is the sound of supersonic flow when the valve opens. Engines that make that sound (you have to correctly identify it compared to an exhaust resonance) are usually really good efficient engines. They make high power from little fuel. engines that sound dull and more bassy are making high levels of CO with high levels of unburnt HC and some unused O2 in the exhaust. Basically they could be better.

Author:  shrinker [ Mon Jan 09, 2012 11:45 pm ]
Post subject:  Re: How's It Sound?

Nomad, think back about the sounds in the carby contest, the better carbys would have made that cracking sound or got close to it. Marks run sounded different to the others I heard.

Author:  hysteric [ Tue Jan 10, 2012 6:23 am ]
Post subject:  Re: How's It Sound?

Do you mean combustion efficiency, as in the more efficient the combustion the sharper the tone?

Hysteric

Author:  Scott Smith [ Tue Jan 10, 2012 8:28 am ]
Post subject:  Re: How's It Sound?

http://youtu.be/W9Yg-w5Qg3Y

Author:  Scott Smith [ Tue Jan 10, 2012 8:29 am ]
Post subject:  Re: How's It Sound?

http://youtu.be/N2dRoJX4wfg

Author:  nomad [ Tue Jan 10, 2012 10:51 am ]
Post subject:  Re: How's It Sound?

shrinker wrote:
http://www.youtube.com/watch?v=x-jMsrl5EIw
During the run the sound is a sharp hard crack, Its got this crack at basically all revs when under serious load. That is the sound of supersonic flow when the valve opens.


Mine is like that. When I have a helmet on it's different, of course. I generally wear ear protection when working on it but one day I stood on it coming down the return road with bare ears. Man, that hurt in a way my previous builds never did. Jmarks SB2 will do that to me also.

Author:  shrinker [ Tue Jan 10, 2012 12:22 pm ]
Post subject:  Re: How's It Sound?

hysteric wrote:
Do you mean combustion efficiency, as in the more efficient the combustion the sharper the tone?

Hysteric

Yes.

Author:  fourtenposi [ Thu Feb 09, 2012 1:03 pm ]
Post subject:  Re: How's It Sound?

So does mine have that sound?

I know its dirty, It will be cleaned today, it has been sitting in the shop for the last two months.

video

Author:  shrinker [ Thu Feb 09, 2012 6:00 pm ]
Post subject:  Re: How's It Sound?

No it doesnt. I see the amount you are opening the throttle and the engine isnt doing high rpm in that time.

Author:  hysteric [ Fri Feb 10, 2012 2:13 am ]
Post subject:  Re: How's It Sound?

Shrinker........Do you have another example for us?

Hysteric

Author:  shrinker [ Fri Feb 10, 2012 6:12 am ]
Post subject:  Re: How's It Sound?

hysteric wrote:
Shrinker........Do you have another example for us?
No.

Author:  shrinker [ Wed Feb 22, 2012 3:16 pm ]
Post subject:  Re: How's It Sound?

At the time of that video that boat was fitted with a low powered engine. World products sportsman 2 heads on 12.5:1 comp. The video was also taken on the first tune of the engine, eventually the team let me retune it (I leaned it a little) and it went a further 6 mile per hour faster than that video. Its record for the season was 19 wins, 2 seconds and 1 crash from 23 starts. You can hear the engine well in that video and it does have the distinctive Smartcarby sound. The sound volume per exhaust event is more even indicating more consistent AFR per event. The engines fuel consumption dropped from 63 liters per meeting to 47 by using the Smartcarby.
Since those days most of the other competitors have moved to the NASCAR motor deals you can get nowadays and so has this boat, its a Dale Earnhardt cup motor now. Its still got a Smartcarby on it, a 1340CFM one and its still winning, so far 10 wins in a row. It uses 8 liters of fuel per race the others use 14, so go figure that out everyone.

Author:  Ron Gusack [ Sat Feb 25, 2012 8:30 pm ]
Post subject:  Re: How's It Sound?

Shrinker, tell me about Jeff Taylor's (near lane) sound. It gives me goose bumps every time I watch it.
http://www.youtube.com/watch?v=tsXOdr48gZ4

Author:  Scott Smith [ Sat Feb 25, 2012 9:32 pm ]
Post subject:  Re: How's It Sound?

delete

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