I put it on the other day and it is definately louder but it just doesn't seem to pull like it did with the cat on.

Any thoughs ?

btw : I checked for leaks and it is air tight.

 

Dont worry, you picked up some hp by ditching your cats. The car probably just feels slower b/c it is louder.

 

Someone correct me if I'm wrong:

Yeah, you probably picked a couple of HP, but you probably lost a couple or so of TQ. These engines like a certain degree of backpressure, and removing the cats took away a lot of that backpressure, especially down low, where the loss of a little torque could easily be noticed.

 

the ideal back pressure is EXTREMELY low...

the only way you could have TOO LITTLE back pressure is by not even running a manifold


but i guess cut-outs make you lose torque too....



could you please explain how something that gives you horsepower, makes you LOSE torque that you previously already had???

 

This is a pretty good read. Backpressure Read Sorry about the website, but the same theory holds true for us. He explains is better than I can.

 

i read it... and its mere speculation, and bad, at that...


he says running straight headers = ZERO backpressure.. which is VERY wrong... he also said that running straight headers will make the engine run like crap and lose a noticable amount of power... THIS IS KNOWN TO BE FALSE... ask any of the 3,000 people on this board who have cut-outs or run straight headers....


then convince them that they should be putting on 1.5 inch pipes all the way to the back of the car so that these "pulses" which "i believe travel at 1,500=2,000 feet per second" will have the correct amount of pressure pushing them BACK INTO THE ENGINE...



that guys either on some good crack... or very very bad...


i haven't decided which yet...

 

Discounting the pulses and that junk (ford guys j/k), I was more interested in the scavenging aspect of it.

I'm not an expert or anywhere near it, I'm just basing what I said off of what I've seen myself. When I was running an open y-pipe on my black 93, there was a noticable loss of torque on the low end. High end was awesome, but low end I lost some. I just put the off road pipe on my PP 93 T/A, and there was a small loss there too.

 

until i see dyno charts i call a double

 

I really wish I had dyno charts.

The reason I say that you lose a little is because of how I launch my car. I usually just roll it off of idle. Then when I had my y-pipe open (cat was taken off the car to be gutted), the car wouldn't roll of the line at idle as easy without coming dang close to stalling. I actually had to give it a little gas. Maybe when we dyno the PP T/A I'll make one run with the cat in place and see what happens.

 

i can GUARENTEE that has nothing to do with the cat not being there... unless you got a 96+ in which case are you getting a code?

 

Nope. Both of my T/A's are 93's.

 

any chance you damaged your o2(s)?


somethings not right... and it has nothing to do with the cat being gone

 

I wouldn't think so. I only ran the open y-pipe for about 3-4 days until I could find a shop that would weld on my old cat with just one brick in it. Got the cat back on and went back to idling off the line.

 

well... i don't know what to say...

doesn't make any sense to me

i've seen cars with true dual aftermarket performance exhausts run cut-outs on the dyno and there were gains across the board everytime... and those cut-outs were placed before the cat


hell i saw a stock lt1 have a $30 manual cutout placed before the cat and gained something like 24hp and 25 lb ft of torque at the rw's....

and that was with stock manifolds...

 

Me too. I wish someone had dyno charts, and could give a good explanation. I saw on here some time back a discussion, and what it amounted to was that when you were running an exhaust that was too big, the velocity of the gases moving through was slowed down, forcing the new gases being introduced into the exhaust to "push" the old ones along, whereas with the proper size exhaust, a vaccum is created at the manifold, thus "sucking" out the cylinder gases, hence scavenging. I would think the same holds true for cutouts.

Also, I may have not been too clear. Granted, you're going to gain with a more free flowing setup, such as ORP or cutouts. I was referring to the lowest end of the powerband as to where the loss would be.

Hopefully this will clear up a little confusion.