if i want to concentrate on 0-30 mph Low end power,
should i totally remove the CAT for better accuration or

change to High flow CAT?
Some ppl said this or that is better.

L15A with turbo 0.5bar only
Auto gear.

 

Dont remove your CAT as you will lose low end power.

You need back pressure so better go for high flow cat and twin loop exhaust.

my 2c

 

Backpressure will kill HP/Torque!! What you need is the BIGGEST pipe that will let the exhaust FLOW enough at HIGH RPM's without being a RESTRICTION, yet, being SMALL enough so that it still have GOOD exhaust gases VELOCITY!! 60mm will be too much for a 1.5l Fit that revs at 7K RPM!

-Too BIG = Flow at High RPM's but low Exhaust gases Velocity at low RPM's = Less scavenging effect = Loss of Low End Torque!
-Too Small = High exhaust velocity at Low RPM's = Good Low End Torque but Little flow at Upper Revs = Loss of Top End power!!

Personately, 50mm pipe with 1 or 2 good quality perforated core Resonators (Maybe 3 if you delete the Cat!), a good straight thru Muffler and a Header with a Merged collector! Forget about the Louvered cores resonators and mufflers that adds turbulence and restriction to the exhaust stream...

Marko!

 

Thank you.

I think i have to put back my CAT. I felt no power during 800 RPM to 2500 RPM. at high speed, I feel nothing change.

Normally i don't race and mostly travel to work only.
So , conclusion, remove CAT is not the way for city drive.
it will slow u down ALOT ALOT ALOT.......

 

Anyway a modern cat is only a restriction to a small degree!! Depending on the size and length, it should only add about 1 to 3Psi of back pressure!!

Marko!!

 

hi-flow megan downpipe all the way! I love mine.

 

Problem again.
After installed back stock CAT, i improve back my Low torque and lost alot of my torque and higher RPM.

1) should I change to high flow Cat? what will happen? lost abit torque at low RPM and gain abit at high? ( half half gain)

2) install Control value before CAT, when higher RPM, the control v/v will auto open

3) install Control value after CAT, so that still have abit of back pressure.

 

do it install dumb valve after cat

 

Ehm, pardon, what is a dumb valve?