Nick.Mixer

Does anyone know how to remove this? Mine seems to be a bitch to remove.

hexjunkie

I removed mine, but I moved to a state that required emissions inspections so I had to buy a new 50 state smog legal cat.

I removed it by jacking the car up removing from the header back to the muffler pipe in front of the axle

put the whole assembly in clamps on a work bench

sprayed the whole thing down with a combination of acetone and WD-40 let it sit (spraying it every 2-3 hours) for about 24 hours then the bolts wrenched off easy

On a side note:
I will say that removing/gutting my cat didn't give me much in the way of power gains, actually quite the opposite on a N/A car it seemed to decrease back pressure thereby creating a slight loss in power.

Nick.Mixer

I'm replacing it with a test pipe do you think it's still going to decrease power?

hexjunkie

test pipe has the same effect as my "fake" cat where I welded a pipe inside to pass visual inspections..

I lost back pressure which reduced my motors ability to push air though it slightly...

Del Sols have fairly decent cats on them stock.. so removing it may have the same effect as mine plus your breaking a whole bunch of enviro fed laws

Nick.Mixer

Oklahoma doesn't have those laws or inspections... Thanks for your help though.

thumper64

First, removing your cat is a $10K fine (if you're caught and don't fix it).
Back pressure isn't necessarily the issue. Don't get me wrong, excessive back pressure is a bad thing, I won't disagree with that. A vehicle with a clogged catalytic converter for example will not perform well. Back pressure is more of an unwanted side effect of trying to achieve proper exhaust velocity to achieve scavenging. By making the exhaust system flow better, such as switching to larger diameter pipe, you raise the RPM range where the scavenging effect will work best.
To understand, you need to know how scavenging works. Basicly the pulses of exhaust gases flow out of the cylinders and while it's flowing, it will somewhat suck the gases out of the next cylinder who's exhaust port(s) opens. If the exhaust just dumps into a huge tube, it won't have enough velocity to create this sucking effect until a high RPM. On an NA car, this is why having a gigantic exhaust pipe is a bad car. Note, this only applies to NA. If you make the tube too small, you get the scavenging at a low RPM range, but choke on the high end.

Maybe I'm not completely thurough in my explanation since I'm still learning, but I've been reading a lot on exhaust systems and so far, this is what I have put together. If someone else is more of an expert on this, please chime in.

hexjunkie

you are correct (i just tend to stick with easy explinations)

with larger diameter pipes or reduced back pressure you loose the ability to create a sucking motion from each of the valves as they open for the next one.

in an NA car you acutally need this pressure to pull from the next cylinder because it can leave old exhaust gas in each of the cylinders and thereby create less space for the new air to enter it. This provides for a less clean and smaller combustion. That is why it reduces power.

Too much back pressure can cause the same problem by leaving exhaust gas in the motor but for a different reason, it has no where to go.

Removing a cat from a car has the same effect as putting dual exhaust on a 4 cylinder motor or increasing from a 1 inch exhaust to a 3 inch exhaust pipe.

my vote would be to leave on the cat until you are ready to go forced induction. Once you go forced induction you will be pushing air though the motor (the same reason why a NA motor will work better at higher RMS because it is sucking air harder)

thumper64

The thing about scavenging is that it not only helps suck the exhaust gases out, but if it's timed right, the incoming mixture will come in, the exhaust valve will shut and then the intake valve will shut behind the incoming charge and trap it in, creating a slightly higher than atmospheric pressure from the beginning, which helps create power. This is where adjustable cam gears can come into play on a DOHC engine to get the correct amount of valve overlap. Too much overlap and you just waste fuel, too little and you won't be able to totally get rid of the exhaust gases. However, with VTEC cams and their longer duration and higher lift, I'm not sure exactly how much adjusting the valve timing will help. I believe it is Toyota's version of variable valve timing, VVTI, that primarily works on this valve overlap principle to make power.

hexjunkie

it just dawned on me but I don't know if this guys del sol is the Vtec, SI, or S model?

I know mine is SOHC Vtec SI so I don't have pleasure of valve overlap

not to mention this would be major time invested for minimal gains (and wouldn't exactly have a major impact on a stock motor)

this is more for the high end all motor builds that just have nothing else left to do

what are you working on thumper?

thumper64

That's a good point. Dealing with like 3 different possible engines makes it a bit tricky.

I have a 1993 Civic CX with a 1995 B18C1. I'm nowhere near the point to be thinking about playing with my valve timing since I have a lot of other stuff to take care of first. After replacing the stock muffler on my old V8 Bronco with a glasspack and noticing a reduction in low and mid range power and looking into building a tuned pipe for a minibike I was building, I just started researching exhaust system designs and found it interesting, so off and on I've been researching stuff like header design, mufflers, stuff like that. I was curious if more expensive headers or large diameter exhausts made any differences and really, header design is just an amazing science. I'd recommend anyone here interested in modifying their exhaust to do some reading on the subject.

hexjunkie

as always, I had to do the same with my street-track tuned Trans-Am... larger pipes/dual exhaust isn't always a good thing... that is why I laugh every time i see a ricer roll around with dual exhaust (and in this area there are a lot of them)

thumper64

Exactly. I didn't really care about power on my truck, I just did it as a cheap fix for the rusted out muffler after a friend talked me into it.
The first time I saw a Civic with dual exhaust I had to do a double take. I noticed the driver's side muffler wasn't even functional, haha. Luckily I don't see many ricers around. The extent I've seen is the fart can mufflers and only a couple Hondas with stupid louvered fenders and wings. The only thing I have on my car that could be considered ricey is the eBay black housing headlights the prior owner put on, but it's not too noticable and with halogen bulbs, they illuminate the road pretty well. I'm putting some spoon style mirrors on because I think the normal 5th gen mirrors are ugly as sin.