Cat bypass DIY Question

[Bob Kontak]

Originally Posted by kuehl

De-gutting the cat? hmmm wonder what that would do on the dyno.

Maybe the guts would buy a couple of six packs of Becks, the stainless hardware.....

What is your point? If you have one, make it.

Also, ask direct vs rhetorical questions.

[kuehl]

Originally Posted by Bob Kontak

What is your point? .

De-gutting the cat? wonder what that would do on the dyno.

[Bob Kontak]

My apologies, kuehl. Read it the wrong way as in "What's the point of doing that?"

[kuehl]

Originally Posted by Bob Kontak

My apologies, kuehl. Read it the wrong way as in "What's the point of doing that?"

Bob,

No problem. I'd like to convert the apology into a Mulligan and use it on the back nine if I can.

The original questions are good food for thought though, you gotta wonder how many have actually done a dyno before and after (just testing the by-pass pipe) and how much do the results vary, and if you gutted your cat would you gain anything worthwhile?

Stay well,

Griff

[hcoles]

You may want to reconsider if planning to destroy a very valuable cat. If sold to someone in CA you will need it to work.

[porsche0nut]

I'm in exact same boat, had local Porsche shop install OBX bypass today.

Was great quality for the $100 I paid, and fit without any problems.

After an hour with it, my butt dyno says a bit nicer (throatier) sound at certain revs under load and smoother power application.... Then again I didn't have an O2 sensor plugged in before (part of the reason for the switch, long story) so that may have affected things.

More power? Maybe slightly, nothing to write home about though.

Overall: satisfied and worth the minimal money. Will be upgrading to SSI's and a sport muffler in a year or 2 anyway.

LoOking forward to hearing your initial impressions!!

[Bob Kontak]

Here is a link that has some quotes from "The Bruce" regarding hp increase. Post #8.

Bypass Pipe HP Increase?

Nothing too exciting, unfortunately.

[Neel]

Originally Posted by ccm911

you do not have to remove the muffler. You don't even need to loosen it. Forget the pb blaster and just cut the hardware off with a dremel. It will be rusted.

Be sure to have the new gaskets handy. You will need them. Go to your local hardware store and get some stainless nuts and bolts. I think you need eight of each if i remember correctly.

You should be able to get this done in no time. Cutting off the old nuts and bolts will take the most time.

But when you are done, you will have a little more sound out the back, and in my case, a little better throttle response.

And most importantly, have fun.

+1..

[strikee]

I did this the other day, but in reverse. For compliance reasons I had to make the car quieter.

With the bypass the car was over 105db, with the cat (pre-muffler) the car was 90db. Measured by my compliance officers fancy meter.

All the bolts were ok, so no heating required. Before spending money on dremmels, torches and exhaust shops, have a go yourself. You never know. Not the end of the world if a bolt breaks.

I had to do a bit of pushing and shoving to make it all line up, but in the end it was relatively straight forward.

Also note that your car might start smoking a little more after the bypass. My dad just installed a cat bypass and now we see blue smoke...

I will soon be swapping it back.

Just an FYI.
Ed

[Onefastman]

So I'm curious how an officer would go about measuring this?

Surely it wouldn't be at idle and I know they don't have the authority to make you rev your car.

Always been curious so if you could shed some light on the matter I'd appreciate it.

I did this the other day, but in reverse. For compliance reasons I had to make the car quieter.



With the bypass the car was over 105db, with the cat (pre-muffler) the car was 90db. Measured by my compliance officers fancy meter.



All the bolts were ok, so no heating required. Before spending money on dremmels, torches and exhaust shops, have a go yourself. You never know. Not the end of the world if a bolt breaks.



I had to do a bit of pushing and shoving to make it all line up, but in the end it was relatively straight forward.



Also note that your car might start smoking a little more after the bypass. My dad just installed a cat bypass and now we see blue smoke...



I will soon be swapping it back.



Just an FYI.

Ed

[strikee]

Australian Complaince Design Rules or something like that.

Not the HWP.

I exported the car from UK to Australia. It has to pass noise tests. You are required to rev that car to 4500rpm and a reading is taken. With the bypass on it failed miserably. With the cat in place it was fine.

Cost me 250 bucks to buy the cat, which will now be taken off and sit in my shed for the next 20 years.
Ed

[Dublinoh]

I have a gutted cat I removed from my 87...with a m&k 1 in 2 out it was obnoxiously loud, and metallic...acted like an echo chamber. I have to wonder how well it would flow (small diameter to large then small again), and would the loss of back pressure effect performance. Cat by pass makes more sense to me

[Onefastman]

Makes sense.

Well, I bought bolts and ordered gaskets.

Also my Dansk sport 1in/1out stainless steel muffler will be here Friday!!!

[Neel]

Originally Posted by Onefastman

Makes sense.

Well, I bought bolts and ordered gaskets.

Also my Dansk sport 1in/1out stainless steel muffler will be here Friday!!!