8Mud
NAXJA Forum User
- Location
- Central Germany
jeepman121 said:So, from what I'm getting is that it probably helps to remove the cat...but not the muffler. Right? When I put that I straight piped I meant that I removed the cat, and put a turbo muffler generic flowmaster 40. Identical baffling inside. Last night I raced a Durango V8 and was ahead 2 cars at 50 mph. So I don't think I lost torque.
You may loose a little torque, but what you do is move the peak torque higher into the RPM band, with a more open exhaust.
I spent a thousands hours tuning exhausts for specific tracks (before the dyno), plug it up a little and lengthen the collector you accelerate out of the corners faster. Shorten the collector and open the exhaust and you get higher RPM's at the end of the straightaway. I've still got my collection of header baffles, to adjust exit diameter.
Look at a few horsepower and torque graphs.
To get an idea of what is going on, think about cam grinds and which are for torque and which are for horsepower, in the 2000-3000 RPM band.
Even Dodge in the muscle car days, used a smaller exhaust valve in large body applications. I guess they were just dumb.
Somebody mentioned exhaust scavenging, this is actually the low pressure between the pulses. Opening the exhaust slows the flow, the exhaust looses velocity and the pulses become more undefined.
But one thing I learned, that theory is fine, but what actually works works despite the theory. One guy made a square collector that everybody tried to copy, kept the major manufacturers test bench guys busy for a year trying to figure out what and how he made it work so well.
I use my butt dyno and rarely make a large mistake, some motors you just know they need to breath better. I've never felt the need to open a 4.0 exhaust up much, but do install a slightly lower restriction muffler on occasion, in the Renix. I've never felt the need to open an HO up any.
Last edited: