Regarding this statement I read earler today in this form { I'd also loose that catalytic, when you take it's guts out it kills the flow. You will make more power with intact one. I know I tried.}
Has any one done a Dyno test on this or are you going by the seat of your panths?

 

Its a widely known fact that a gutted cat hurts power. The empty shell creates a disruption in the exhaust velocity.

 

Up

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Runnerdown &raquo;</TD></TR><TR><TD CLASS="quote">Its a widely known fact that a gutted cat hurts power. The empty shell creates a disruption in the exhaust velocity.</TD></TR></TABLE>

agreed

 

If that is a fact, then why do test pipes outflow cats? Or even open header dynos for that matter? There is a test that was done a while back comparing high flow cats with each other and a test pipe was flowed as a control, it is in a thread on here somewhere.......The results are worth taking a look at.........

 

I don't know what your trying to say, but the matter at hand is gutted cats. Test pipes and high flow cats are fine, but emptying out a convertor and running it hurts power.

 

No what he was saying is that the open chamber is larger than the pipe. This open space will slow down the velocity of the exhaust gases. A test pipe is the same diameter theirfore this will not happen. I would still like to hear if anyone did it on a Dyno. I'm old school and that is how we did it back in the day. I'm just interested to see which is worse the open chamber or the restriction in the cat.

 

I think the results of running either are relative. I gutted the cat in an old mazda 323 turbo I had and i'm pretty sure I did'nt lose any power. Being turbo, I assumed the added backpressure of the ancient cat would cause more lost power then a empty chamber. Now if I gutted the cat on my stock 91 si, I would be willing to bet that a small power/torque loss would be had and be noticable. That being said, my opinion is that in most everyday applications you would only lose power and pollute more. If anyone has actually done dyno tests I would be very interested to see.

 

How about it, anyone done this on the dyno, or are any mechanical engineers out there can explain what is the difference between the open cat and the open chamber that some cat back systems have as far as wheel HP goes?

 

if you gut a cat it is not straight through like a testpipe.

this will **** up the exhaust velocity on it's way out.

look in old threads, there's actually people who have hallowed out their cats and lost power many times.

 

i agree wholly with runner ... the open chamber disrupts the velocity ... you need that velocity to prevent reversion and help scavange the chamber

 

if you need to have a cat
then gut it
have a good muffler shop expand the ends and push a pipe thru it
viola test pipe cat
passes visual checks