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post #1 of 10 (permalink) Old 06-06-2011, 10:01 PM Thread Starter
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Straight piping?

Hellooo.

Starting my summer project shortly, and its going to be a drag sled.

I just have a question about straight pipes because I realize that many many drag racers set up their sleds with nothing but a 2-3 inch diameter pipe directed to the side as the exhaust pipe, one for each cylinder.

what are the gains if any of doing this to a drag sled?
is it bad in any way?

might be a dumb question but Im not going to try and make some without a real reason, lol

thanks

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post #2 of 10 (permalink) Old 06-07-2011, 01:29 AM
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Straight pipes on a two stroke can be dangerous to the engine. Because of the design of the engine, the intake ports and the exhaust ports in the cylinder are both open when the piston is at bottom dead center. Some of the unburned fuel actually enters the cylinder and exits with the exhaust gas, but because of the length and shape of the pipe, at the exact moment the raw fuel/air is leaving the cylinder, a pressure wave rebounds from the restriction in the pipe and shoves the fuel back into the cylinder to be burned.

If you have a straight pipe, there will be no rebound and your air/fuel mix will be lean, which could cause excessive heat and melt holes in the pistons. If you make the fuel mix rich enough to be safe, your fuel mileage will go south, and your emissions will go up. You will also have really lousy performance at lower RPM. Carbs are designed around the tuned pipe, it will take you a long time (and probably a few rebuilds) before you find jetting requirements to keep the engine safe and still give power.

A tuned pipe eliminates all that and gives you more power to boot, as all the air/fuel mix is burned with no waste.

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post #3 of 10 (permalink) Old 06-07-2011, 03:45 PM Thread Starter
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Thanks Dan once again!

Yeah, I wasnt sure but it did feel like straight piping would feel sort of 'wrong',
I just wanted to check because it would have been nice to have at least one freebie component to the sled! haha.

Ive also seen people running twin/tripple pipes but without the stingers, is that just as bad? or sort of like a half way type of thing?

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post #4 of 10 (permalink) Old 06-07-2011, 11:56 PM
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There may be a bit of benefit from stingers, but would be easy to tune around (if there was.) The stinger mostly muffles the sound a a bit. Without stingers, a sled would be uncomfortably loud! Noise is not important when drag racing, wear hearing protection

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post #5 of 10 (permalink) Old 06-08-2011, 03:25 PM
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Dan, stingers are the small tips on the ends of the pipes, silencers are a packed attachment or open box attached to the end of the pipe outlet.

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post #6 of 10 (permalink) Old 06-08-2011, 05:22 PM
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Stingers are the same as the silencers.
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post #7 of 10 (permalink) Old 06-14-2011, 07:08 PM
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Originally Posted by BC_Dan View Post
Straight pipes on a two stroke can be dangerous to the engine. Because of the design of the engine, the intake ports and the exhaust ports in the cylinder are both open when the piston is at bottom dead center. Some of the unburned fuel actually enters the cylinder and exits with the exhaust gas, but because of the length and shape of the pipe, at the exact moment the raw fuel/air is leaving the cylinder, a pressure wave rebounds from the restriction in the pipe and shoves the fuel back into the cylinder to be burned.

If you have a straight pipe, there will be no rebound and your air/fuel mix will be lean, which could cause excessive heat and melt holes in the pistons. If you make the fuel mix rich enough to be safe, your fuel mileage will go south, and your emissions will go up. You will also have really lousy performance at lower RPM. Carbs are designed around the tuned pipe, it will take you a long time (and probably a few rebuilds) before you find jetting requirements to keep the engine safe and still give power.

A tuned pipe eliminates all that and gives you more power to boot, as all the air/fuel mix is burned with no waste.
krikey where do you learn all this?


Last edited by BC_Dan; 06-15-2011 at 12:06 AM. Reason: language
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post #8 of 10 (permalink) Old 06-15-2011, 12:06 AM
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I stayed at a Holiday Inn Express

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post #9 of 10 (permalink) Old 06-15-2011, 06:39 AM
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And Years and Years of failures! Personally I've been sledin since 69-70! Been wrenchin since 72!
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post #10 of 10 (permalink) Old 06-15-2011, 10:10 AM
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And Years and Years of failures! Personally I've been sledin since 69-70! Been wrenchin since 72!
Does that mean you didnt have to fix your sled for 2 years?!

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