FastZinTennessee

The cheapest and easiest way would be to get one, and weld it in just after the Y-pipe.

LT1 POWR

would it flow good enough with just one cat.

FastZinTennessee

I didn't notice a drop in power when I added the cat on my HOTcam/ported heads setup, so in my opinion it will flow well enough for what you are doing.

LT1 POWR

Should i put one cutout just before the cat or go another route.

Eff

Wrong.

Not to be arguementive. but a good highflow cat goes for around $250.
There woulnd't be a market if there was HP loss. If you loose ANY power your you bought a bad cat. even with high hp engines it doesn't matter. The volumetric displacement is a calculated match.
In fact, a well made high flow cat can actually improve HP as opposed to a gutted cat, with exhaust. Using a gutted cat causes the exhaust gasses to expand, only to be forced to compress in to the exhaust, this creates more back pressure.

If you go with a straight pipe, it will probably be the same, but then you have to worry about emissions.

96vortechSS

I agree with you about gutted cats but disagree with you 100% about highflow cats producing the same power as a straight pipe. No way possible. With a high flow cat there is sill honeycomb in the airstream. If your going to run a striaght pipe and have to deal with emissions just have flanges welded on so the cat can be installed and removed easily. If you must run a highflow cat buy a carsound cat. They're made by magnaflow and are cheaper than the random tech cat. Any good highflow cat will produce the same power so you might as well save some money.

stereomandan

Sorry Eff, but do you have ANY data to prove what you are saying? No offense, but you will have a very hard finding any because your argument is wrong. Sorry if that sounds harsh.

1) Price doesn't matter. Performance does.
2) It makes a HUGE difference what HP you are making, and how a high flow cat will affect that HP.
3) A straight pipe flows more than any high flow cat, given the same inlet/outlet tube diameter

Did you get a chance to read the post that I linked to?

Dan

DiabloGT

ok, so how much of a diff will i notice in hp with a magnaflow carsound cat and a straight pipe on a 400rwhp+ car with lts and lm exhaust?
thanks

stereomandan

I wish I knew the answer because I haven't seen any dyno graphs that show what you are referring to. All I know is that you need 2.2 cfm of flow at 20.4" of H20 to support 1 HP without loss.

Just for reference, the two stock converters on an LS1 flow 567.8 cfm together. This means that they will support 258 HP without HP loss. We all know that the LS1 makes more HP than 258, and probably more like 330 flywheel HP. The stock cats on an LS1 rob 8 rwhp according to that link. So that gives you some idea of the HP loss from cats.

Dan

96vortechSS

There is no way to know for sure. There are too many factors: elevation differances, every dyno reads a little different. Anyone would be guessing to give you an exact number. I can tell you 400+rwhp would be easier to to attain with a straight pipe.

bdc95ta

The cats need heat to work right so placeing them right after the headers would be your best bet for emissions. Remember the exhaust slows down a lot once it leaves the headers.
-b

Eff

Well, having access to a Chasis dyno in school, for three weeks I played with a 94 z28. changing the exhaust system or nitrous jets. up to 465hp I didn't see any loss in power There is my credibility. wheres yours?

1) Agreed. but quite often you get what you pay for.
2) The amount of HP lost to a standard cat... your are correct.
3) now here is where I ask for your credibility. prove it! If you meant chamber size. I agree with you.

stereomandan

What was the exact exhaust setup for the chassis dyno?

2) Why do you think a high flow cat is THAT much better then a standard cat. They are better, but they don't flow like a straight pipe. Did you see the flow results on the link I posted? Show me flow results from a cat that has the same airflow as a straight pipe with the same inlet and outlet diameter.
3) The ONLY affects you are going to see in a straight pipe are the edge effects. On a high flow cat, you have the transistion from small to large volume, then back to a small volume and then you have the catalyst elements directly in the air stream and then the edge effects on top of that.

Dan

Eff

You're exactly right, but the larger diameter does make up for it.
Anyway. http://www.cardomain.com/ride/764567 (red car)after doing all the testing on all the shop cars I took off my straight pipe and went with a MAC high flow cat. HP numbers were basicly identical.'
My headers are MAC shorty's 1 5/8 primary's 3" at the collector, B&B triflow Catback.

We can argue all day about which flow's better. but one way or another it's not enough to make a difference on the dyno.

stereomandan

I agree with you there. Depending on the HP you are making, the difference between a straight pipe and high flow cats may be too small to even care about, especially if you are using dual high flow cats.

MAC's I also have the MAC mids ('94-'95) style with a bullet muffler in place of the cat, and a Hooker catback. I also have a carsound highflow cat sitting on my shelf if I ever want to use it. I can swap it for the bullet muffler in a couple of minutes.

Dan