Fabspeed Bypass Pipe-Any Experiences Welcomed.

[Marburk]

Originally Posted by ProjectM96

There are youtube videos of the Fabspeed Exhaust sounds from inside the car and outside. You can access them from Fabspeed.com when looking at the products, or you can go to youtube.com and manually search them.

Thanks, M96!

[insite]

shot some video w/ OEM cat pipes vs. fabspeed bypass pipes. will post today.

[insite]

some clips comparing OEM vs. bypass.

engine is a 3.4L with a custom intake, headers & a stebro race muffler. the OEM cat pipes are from the 2.5L. the bypass pipes are 2" fabspeed.

[Johnny Danger]

After posting that video, I got a call from these guys .

[insite]

never exceeded 5 over.....

[jaykay]

Does current information suggest that installing secondary cat delete pipes and a Pedro style/pse style bypass exhaust muffler (modified stock s) will reduce back pressure (and therefore alter exhaust scavenging) to such a degree that there are losses in torque and power? Can one simply look at what the computer has done to ignition timing to see if it has detuned the engine via ignition retardation, to get an idea whether an exhaust system is working well? What are the stock ignition parameters and what variance would be bad as seen via the OBD port?

Yes I know dynos are the tool I am dancing around!

[insite]

you have to consider the whole system and the REASON backpressure is a concern (it's not).

most people talk about backpressure like it provides something to the equation. well, again, we have to consider the SYSTEM. scavenging depends upon VELOCITY in the exhaust gas. the velocity is what creates vacuum at the valve outlet. if the pipes get too big early in the system, velocity stalls and pressure increases. this means no scavenging. we also have to consider that as the exhaust gasses cool, they condense a bit, leading to further loss of velocity (this is why people try to keep the heat in headers).

ideally, you'll have a properly designed header. the length & diameter of the primaries will be tuned to the engine's parameters (valve timing, duration, diameter, angle) and to the desired performance charictaristics of the user (high-band power, low-band torque). they will join into a merge collector that is a venturi. it will neck down slightly & then open up a bit (like a megaphone). the header itself will accelerate the air past the venturi (secondary flange). once this happens, you want LARGE pipes; back pressure is not a concern.

if you're using non-venturi style headers or the OEM manifold, it's not the loss of cats & backpressure that causes the problem. it's velocity loss due to the DIAMETER of the tube. the bypass pipes are all 2", but the OEM pipes are SMALL. this means that you'll lose velocity & scavenging lower in the RPM range. there may be some improvement at the high end. all else equal, removing the cats will greatly improve velocity & in turn, scavenging.

with OEM exhaust manifolds, 2" bypass pipes and the pedro muffler, you will probably lose power overall w/ the 2.5L and 2.7L motors. there MAY be some high end power gains. the 3.2L and 3.4L would probably make power.

if you go w/ decent headers on the 2.5L / 2.7L, the bypass pipes & pedro muffler will make power up high, but lose some torque. i found the 2.5L to be gutless w/ torque anyway, so i always opted for high RPM power & revved the crap out of it. much more fun for me!

[Johnny Danger]

Originally Posted by insite

never exceeded 5 over.....

Don't worry .... I told them to give you a break away !

[insite]

i was SUPPOSED to be at the track today, but tropical storm Lee had other plans. date has been revised to 9/15.

i will take some video so you all can get an idea of exactly what a well tuned, stripped out boxster w/ a 3.4L can do when i REALLY get into the go pedal....