Axle-back exhaust removal?

[eyeballs]

sounds great! Hard to tell from video, but that actually sounds quieter than my new muffler with the silencer removed.

 

[Mazdamatic]

Just be aware by removing the muffler at the flange, you're directing exhaust pulses straight up towards the rear of the car. Personally, I wasn't too excited about that idea which is why I never tried it (though for short duration/testing purposes I can't imagine it would hurt anything).

After some more driving I'm pretty happy with my temporary solution, though I feel I'm loosing a little bit of power up top for street driving since I'm leaving the silencer in.

just have a fab shop or exhaust shop weld a pipe out the back. shouldnt cost more than 15bux but i like that its over the axle cuz if the pipe falls you can hear it hit the axle and not the ground scraping. so u know if it falls. (learned this awhile back.....)

 

[Mazdamatic]

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

nice. its all about gas velocity it seems. which is why i lost some low end power =[

 

[Erv]

fwiw, it's not back pressure it's resistance, back pressure means something is pushing against the flow, resistance is ease of flow...

I put a muffler delete pipe on and feel like I gained hp and low end torque, and it was verified, especially in the low end torque by my dyno. The stock muffler is rediculously restrictive.

 

[Racebrewer]

Or does the gain in upper end power make it seem like a loss in low end power?

Last weekend I swapped race motors in a kart replacing a motor with a wide power band with one that had more peak power. By seat-of-the-pants, the driver preferred the second, but the first had better lap times.

The brain is not always the best test.

John

 

[Erv]

Max hp is irrelevant its the performance under the peak tbattles is important.

The kart reference is reaching unless both engines were driven the exact same way there is no way to garuntee it was the motor

 

[chumlet]

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

Great link! Still running with no muffler and enjoying it I used metal zipties to keep the pipe up just in case haha!

 

[Mazdamatic]

fwiw, it's not back pressure it's resistance, back pressure means something is pushing against the flow, resistance is ease of flow...

I put a muffler delete pipe on and feel like I gained hp and low end torque, and it was verified, especially in the low end torque by my dyno. The stock muffler is rediculously restrictive.

gas velocity/resistance.

2.5 was good for no backpressure but thers not much velocity. which is why i believe 2-2.25 in straight is best. almost no backpressure but still good gas velocity. but i really wont know until i dyno the 2.5in

 

[chumlet]

Sorry to hop off topic just wondering if anyone knows where Mr. Font is? Trying to buy this seat bracket ASAP!

 

[Jasonjames]

Some engines with carbies can run lean down low if the exhaust is replaced with a much free-er system. Its tied up with normal cam-overlap between the inlet and exhaust. Imagining the beginning of the intake cycle at TDC,...the exhaust valve is still finishing its closing, and as the piston is now commencing its downward stroke, it not only pulls AF in from the intake manifold, but also can pull gas in from the exhaust system. The lower the resistance to flow back from the exhaust [or lower the "back-pressure"], the more the effect is.

One factor which is also in play these days,..is the closed-loop mixture control. Perhaps this aleviates the effect?