m21sniper

My Borla system does that too Big Dave.

Popping is a sure fire sign of a very free-flowing exhaust. I kinda like it too.

PorKen

I've found that there is a psycological difference between muffled and NASCAR.

When I've switch from my big bore exhaust, back to full stock for emissions tests, she always 'feels' faster initially. The 'improvement' came from being able to use more pedal at lower speeds, without the negative feedback of resonance, and noise from an open system.
...

As far as I understand it, backpressure is always bad. It's the speed of the gas flow that is comprimised at low engine speeds with a larger pipe. The larger pipe actually slows the exhaust when there is not enough volume to keep the core gas temperature high.

RDS928S

Big Dave,

that sounds sweet. Very authoritative.
It's amazing how much affect the cats have on overalll sound.

it is a little loud for my taste though. Was your microphone right next to the tail pipes?

Thanks Rich

jyoon

my car pops alot during decel also. does this mean you're running rich at wot also? or is it unrelated?

Ketchmi

I don't have any way to capture or post any sound clips. If I did, I would. Big's X-over w/cats is as quiet as stock but with more hp.

Ours sounds a little less raspy at 4k+ rpm.

RDS928S

Dave L,

Thanks for the input. Quite is good -especially for a daily driver. I can't wait to hear your x-pipe installed. I like a nice low key rumble. Slightly louder than stock would be ideal.

Rich

the flyin' scotsman

The backfire heard when decellerating is caused by the air/fuel mixture being too lean. When you lift your foot off of the go pedal the only gas supplied to the engine is through the idle mapping although the LH may have a little more sophisticated.

This problem is very prevalent in big bore V twin m/cycle engines and the cure all was to richen the pilot circuits. Before the richening the carbs would sometimes be blown off of their intake mounts by the strength of the backfire.

Ketchmi

Richard, yours is due back from HPC tomorrow or the next day.

Malcolm, yours is shipping within the hour...

the flyin' scotsman

YIPEE!!!!!!!!!

Big Dave

Yes, I had the microphone right next to the tailpipe, and my car was in the garage. Under normal driving conditions, the sound is pretty tame and doesn't draw attention. But when I stomp on the gas, it roars. I can set off car alarms in parking garages, but only if I want to.

Darien

Well, I got a few feedbacks on the affects of less back pressure. Not sure how we got on sounds

the flyin' scotsman

Darien.........as soon as the X pipe arrives I'll advise on sound level and quality. My system will then consist of stock headers, the Motorsports X, stock mid pipes and resonators into a RMB.

toofast928

On my 16v I tried straight pipe, cat installed. Too loud but lost all bottom end TQ
Next tried Borla exh with the cat installed. Nice sound, little too quiet but has bottom end tq. Mid to top end hp drops off. In fact engine feels like it's starving for air.

What I ended up with is Borla exh and no cat. Just loud enough and the engine wants rev.
Adding the SC bumped up the exhaust note. Anyone around me on the hi way knows when I go full throttle.
Popping sound on deaccel is fuel burning in the exhaust. Nice sound, wastes fuel, very bad for the cat converter.

Weissach

Did you add two Borla mufflers or just one? Wich one did you use?

figgen

I run the same set up on the '85 ( Custom x pipe / instead of cats, no air pump, center resonator in tact and original rear muffler. Sounds is a bit louder not not obtrusive.

It works well for me !