OK, I am not arguing, I am looking for an explination and understanding. Years ago I had a bajabug with a built vw motor, pistons lightened, heads ported, mild cam and a weber carb. Ran a trimill Open tuned length exhaust.

Running the exhaust open about 2500 rpm it came alive and had really good top end. If I stuck a supertrap muffler on it, the charachter of the motor completely changed. It came to life right off the bottom, MUCH stronger but definitly gave up some top end. This was really nice because simply slipping on or off the supertrap I could 'tune' the motor for more techical terrain vs. more open faster terrain.

The resonant frequency of your exhaust system was altered. That gave you better scavenging at lower RPMs with the muffler added. Meaning it could draw in more intake charge when your cam with overlap had both the intake and exhaust valves open at the same time. A longer exhaust system will have a lower natural frequency and and a shorter one will have a higher natural frequency.

The exhaust scavenging effect is what allows some naturally aspirated engines to exceed 100% volumetric efficiency.

How about this: We here it here and everywhere.

"Put a bigger carburetor on it for more fuel."

So it was operating like a quasi 2stroke pipe?

Your exhaust probably had incorrect collector sizing and lengths. Hurt the low-mid range.

Your Supertrapps probably diffused the the timing of your reverse pulse. Helping low end but adding restriction.

Therefore you would think the SuperTrapps helped low end and the open pipes ass high end, when a correct dimensioned exhaust could do a lot of both.

Back in the day we all did it buy trial and error and came to conclusions for why/how/ and etc for why things worked or didn't.

When I was getting heavily involved in circle track and street racing, I was developing parts. Okay R+D'ing and developing parts.

I gained almost 60hp on the dyno with a mild mid 400hp small block just by changing the collector.

I thought I was king schit for a while, I was so exstatic. Sp?

Motors and exhausts later that same collector did schit. Why ?

The first one had the wrong lengths for the motor until I changed them to something better by mistake (I was after internal better flow).

Anyway - htere's programs and many years of research (and better carburetion / etc - remember exhaust directly impacts the carb) that can put us real close to what the ideal exhaust is for your app.

Okay, off that - let's carry on.

2 stroke pipes are a whole nother beast as they are built to hold and then put fresh air/fuel back into the cylinder, not just pull out exhaust to help the intake pull in air/fuel.

Nothing like your exhaust being an intake manifold too. LOL.

This .gif is great as a demonstration (2 stroke exhaust) of what I'm trying to say . LOL.

http://sports.racer.net/engines/suzu...o_stroke_c.gif

No

....

No. I seriously believe they mean backpressure. Restricted and unrestricted is relatively easy to think about in basic terms.

What a thread derail.

LOL.

,,,,,,