[taurus8916]

hey I have two catco high flow cats AND i LIKED the perf diff, but would it be even better with no cats and just a straight pipe? or would I have like no backpressure then???

 

[sixfofalcon]

I think the general consensus among researchers is that backpressure does nothing for you. It is all about velocity. If the pipes are very small, it is helpful with low-end torque, b/c the velocity of the exhaust is very high. This helps to scavenge up all of the exhaust gases from the cylinders after the power stroke.

The problem is, people equate that with backpressure, which is wrong. If you have 4" straight pipes, and then they taper to 1" at the tails, you will have mad amounts of backpressure, but not much low-end torque, since the exhaust gases move very slowly through the pipes and this leaves a lot of exhaust in the combustion chambers.

So, ideally, on an n/a car with under ~200HP at the wheels, you want small pipes (2" or less for duals, 2.25" or less for single) with no cats or high-flow cats, and free-flowing muffs. This topic gets a lot of debate, but that is my understanding of it after reading a LOT of info from many different sources.

BTW, how are you going to pass emissions with no cats?

 

[mikehawk]

I've seen them use engine size as a reference, not hp to the wheels. Anyway, when I wrote to the magnaflow tech people they recommended either 2 1/4" duals or 2 1/2" single for my application.

But, IIRC taurus8916 is planning on putting nitrous on his car. Right? In which case, you'd want a slightly larger pipe diameter.

Anyway, not sure what this has to do with high-flow cats vs no cats. I think you'll be fine with the high flows you have.

 

[taurus8916]

yeah maybe even smaller, I might go 35-45 jet, still decideding, yeah I already have 2/1/4 front to back, so would I even see a diff at all with no cats ebing backpressure prolly isnt going to go a problem? L8er

 

[sixfofalcon]

Originally posted by mikehawk@Feb 8 2004, 09:10 PM
I've seen them use engine size as a reference, not hp to the wheels.

That's probably correct... I was just using a number off the top of my head.

 

[92sho]

Just remove the cats. What you will 'lose' in low end grunt you'' make up for with the nitrous and you will gain 'some' on your upper end without cats.

 

[taurus8916]

hell Im gonna do it, Ill see how I like the gains and loud a** sound lol

 

[Guest]

I wouldn't recommend it. I don't think you'll do any damage, however without cats you'll need to get something to fool the coumputer into thinking the car has cats. I forget what they're called, MIL eliminators or something? Basically, the after cat oxygen sensors will throw a SES indicating that the cats, which are not there, are performing below threshold value.

Did you have a custom y-pipe made also? The stock Vulcan is about 1 7/8-2", so if it's the stock y-pipe and you're just eliminating the cats, I don't think you'll see any gains at all. It's not a big-block Chevy, and the engine doesn't have the right type of mods to warrant a freer flowing exhaust.

 

[mikehawk]

Originally posted by DeltarMN@Feb 11 2004, 12:28 PM
You can do the same thing that mil eliminators do with some paper clips.

Edit: its just less fancy.

Please elaborate.




And taurus8916, if you decide to take the cats off, what are you going to do with them? How much did you spend on these high-flow cats that you're willing to throw away? Just seems like a waste of money to me.

 

[taurus8916]

hey I guess Im gonna listen to bob, why waste all teh extra time and money on something that might now even help in perf, Ill keep em on, I am soooooo hapy my udp is getting on in 2 hrs!!!!!!