ShadowsPapa
Well-Known Member
- First Name
- Bill
- Joined
- Oct 12, 2019
- Threads
- 180
- Messages
- 29,491
- Reaction score
- 35,083
- Location
- Runnells, Iowa
- Vehicle(s)
- '22 JTO, '23 JLU, '82 SX4, '73 P. Cardin Javelin
- Occupation
- Retired auto mechanic, frmr gov't ntwrk security admin
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- 3
Actually exhaust design can modify the curve greatly. Velocity, scavenging, all impact LOW END torque greatly. You can shift the curve higher or lower, you can increase torque, HP, shift it, or decrease it all with exhaust changes.
If a pipe is designed for only bottom end torque, it will give up top-end horsepower and vice versa.
Racers building large-displacement high-horsepower engines often design a pipe for top-end power to reduce low-end torque. You gear accordingly.
For example of how an exhaust change could indeed change the look of the dyno results - consider this -
A larger exhaust changes the shape of the power curve.
It makes it more peaky, but the area under the curve is reduced.
Average power is less but peak power is more. You sharpen it.
Too large is bad, you want velocity and not turbulence. Velocity helps pull the exhaust out as there's a slight vacuum behind each pulse of exhaust - and faster pulses means more pull - scavenging.
tuning exhaust can totally change the look of the dyno results.
I changed mine on my 73 just by putting an H in behind the headers. Some prefer the more expensive X design.
If a pipe is designed for only bottom end torque, it will give up top-end horsepower and vice versa.
Racers building large-displacement high-horsepower engines often design a pipe for top-end power to reduce low-end torque. You gear accordingly.
For example of how an exhaust change could indeed change the look of the dyno results - consider this -
A larger exhaust changes the shape of the power curve.
It makes it more peaky, but the area under the curve is reduced.
Average power is less but peak power is more. You sharpen it.
Too large is bad, you want velocity and not turbulence. Velocity helps pull the exhaust out as there's a slight vacuum behind each pulse of exhaust - and faster pulses means more pull - scavenging.
tuning exhaust can totally change the look of the dyno results.
I changed mine on my 73 just by putting an H in behind the headers. Some prefer the more expensive X design.
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