Help with bad performance

[Deanerwiththemagicalweener]

Hey guys having some issues with my 2002... When I bought her it was really zippy could spin the tires anytime no problem. Shortly after buying my exaust starting having problems with rot so I decided to do a muffler and resonator delete... I just put a glasspack and called her a day... Well When I did this I lost a whole lot of performance... Takes me 3000 rpm to get the same torque and power as 2000 rpm before .... So I thought it may have been something to do with back pressure or maybe the cats... Anyways in the last week I decided to remove this and put a proper muffler.... So ended up installing a super 44... I installed it and also cut out the second set of cats or resonators what ever is right after o2 sensors... When I finished took her for a ride... It sounded really good , and was amazed that I had my performance back.... I had all the power in the world maybe even more than when I bought her... Well my next order or business was I wanted to hallow out my primary cats to get rid of that Nasty burnt hair smell when driving...  So I did this and bam again lost all performance... So now I'm scratching my head as to what this could be... I originally thought maybe I wasn't getting enough back pressure but I keep reading that back pressure is all a myth so my next idea was maybe the o2 sensors were making the engine run rich due to no cats so I installed the o2 spark plug non flowler to see if maybe that fixes it... Cell went out but still no performance... So I don't really know what else this could be and why punching out my cats would do this... Anyone got any ideas on what I can check next??

 

Any info is greatly appreciated...

 

Thanks in advance...

[Guest]

Hey guys having some issues with my 2002... When I bought her it was really zippy could spin the tires anytime no problem. Shortly after buying my exaust starting having problems with rot so I decided to do a muffler and resonator delete... I just put a glasspack and called her a day... Well When I did this I lost a whole lot of performance... Takes me 3000 rpm to get the same torque and power as 2000 rpm before .... So I thought it may have been something to do with back pressure or maybe the cats... Anyways in the last week I decided to remove this and put a proper muffler.... So ended up installing a super 44... I installed it and also cut out the second set of cats or resonators what ever is right after o2 sensors... When I finished took her for a ride... It sounded really good , and was amazed that I had my performance back.... I had all the power in the world maybe even more than when I bought her... Well my next order or business was I wanted to hallow out my primary cats to get rid of that Nasty burnt hair smell when driving...  So I did this and bam again lost all performance... So now I'm scratching my head as to what this could be... I originally thought maybe I wasn't getting enough back pressure but I keep reading that back pressure is all a myth so my next idea was maybe the o2 sensors were making the engine run rich due to no cats so I installed the o2 spark plug non flowler to see if maybe that fixes it... Cell went out but still no performance... So I don't really know what else this could be and why punching out my cats would do this... Anyone got any ideas on what I can check next??
 
Any info is greatly appreciated...
 
Thanks in advance...

Back pressure is not a myth.


Sent from my Pathfinder

[Slartibartfast]

Four-stroke engines don't need backpressure, they need scavenging. Each exhaust pulse helps to draw out the last of the pulse before it. When you've got two banks of cylinders joined up, each bank can scavenge the other, improving the engine's performance. (Even hot rods with dual exhaust tend to have an H pipe or X pipe crossover between the two banks for this purpose.) Looking at how the VQ exhaust is set up, it looks like it's got two mufflers, and the first one doubles as the Y-pipe between the two sides. If that's the muffler you messed with, the loss of scavenging could explain your power loss (and why it came back once you revised the exhaust). If the muffler you messed with was the one behind the axle, then I've got nothing.

A gutted cat leaves a big empty chamber in your exhaust system, and those empty chambers are probably screwing up your exhaust flow. (If this doesn't make sense, look up a video explaining the expansion chamber exhaust system used on two-stroke engines.)

 

[Deanerwiththemagicalweener]

Ok well I kinda messed with everything at this point lol... First I took at the big muffler and small looking muffler right before the axel and right after the axel ... There is usually 2 mufflers one big one small.... I took both those out and put glasspack and lost huge performance...  When I decided to go back to regular muffler that's were I gained my performance but I did 2 things when I got rid of glasspack... Those 2 things we're adding the new muffler than I cut out the 2 resonators or secondary cats what ever there called, it's the ones right after o2 sensors.... That's when I had huge performance... I just cut them out and put a straight pipe in place... It's only when I hallowed the cats out that I went back to no performance again... I did add the o2 spacers to stop cel and wacky fuel ratios.. still no power so I dont know if maybe it's the chamber is messing with the flow or something...