i want to do a straight pipe exhaust on my r53. all i want is my stock muffler. i want to delete everything els including the cat. does any one know how will it sound? besides being loud? anything i should look out for? power gains? power loss?

 

Not a good idea to delete the cat....it's there for a reason. Why not just do the popular "one-ball" mod? Basically the same thing but with the cat.

If you want noise, just go for a nice header and exhaust system.

edit:I just read your signature and saw you already have done the one-ball.

 

im asking becuase with the one ball it sounds kind of like a tin can. im looking to get a bit more of a deep sound.

 

Header and 2 1/4 pipe. you should be able to chop your cat and tune the CEL off. I would also put a cherry bomb in place of your cat. I don't know with these little engines if there's any gain or loss but it sounds great. More of a chainsaw than a weed eater sound lol.

 

I would read a bit more if I was you before you jump in head first. I don't want to derail your plans by any means, but you don't want to end up wasting money. You have 19% pulley listed, then FMIC, then turbo-swap. Obviously the pulley will be a complete waste if you end up turbo-swapping. Also, not many people run a 19%, but that doesn't mean you can't. There are consequences to that however, so make sure you know what you're getting into. I have read a lot about the FMIC not being worth the cost and complication. As far as TMIC, the stock is not bad, GP is better, and it seems like the new one from Defenders of Speed is better than the GP, but the numbers for that are not yet verified by the masses. Same goes for the big valve cylinder head, make sure you know what you're getting into. I have read that the stock sized valves on a larger head are the way to go, BUT have not done it myself. Like I said, not trying to derail, just throwing some stuff out there to think about.

As for de-cat and straight pipe, is your plan to relocate the battery box and go straight out the back, or are you saying you will replace the cat with a straight pipe? I know a lot of people have done this and you just have to trick the O2 sensor so you don't get a code, but you would have to read more on how to do that as I don't know.

 

well, im not doin a turbo swap anytime soon. my question for the exhaust was that if i do a de-cat will it result in more or less power? im routing the exhaust thru the muffler. i just want to delete everything that comes before the stock muffler.

 

In the TURBO world less back pressure is key to creating power. I'm not sure if this applies to s/c stuff but I would imagine its about the same. And as long as you leave the pre cat. O2 in and "trick" the ecu to believe that your post cat is monitioring correctly you should notice a significant difference in sound and a bit of performance too. I would still recommend a glass pack in place of the cat just because it sounds meaner, course I would drop the factory pipe and muffler too. Just my .02 tho

 

In years past, Randy Webb said that deleting the cat didn't really gain any power. More or less depends on what you do before and after it.

The real question is why do you want to delete everything before the muffler? Sound? Exhaust restriction? Weight?
Conventional wisdom says that you can lose torque with less back pressure, but there are LOTS of variables.

 

im doing it for sound, exhaust restriction and also i might swap out the stock muffler for an aftermarket. any ideas on how the out come would be?

 

PICK ME PICK ME! lol. I just got finished with revision three of my custom exhaust.
If you want deep tone with lots of burble use 2.5" pipe, obx header, (i put a vband on it) a magnaflow same side in/out muffler (put it where the stock resonator was) http://www.jegs.com/i/Magnaflow/642/...oductId=751040

and two vibrant ultraquiet resonators. One post cat at an angle in the exhaust tunnel, and the other in the location of the stock muffler.
The vibrants work really well to smooth the exhaust out, but do not reduce noise volume much at all (even though technically if you saw one you would call it a muffler, not a resonator by its design) , while the magnaflow will take a good bit of noise volume out of the equation.

My setup has a cutout in it, so I either run 3 vibrants and a magnaflow (mine is a http://www.jegs.com/i/Magnaflow/642/...rentProductId=)
or just one vibrant and the magnaflow.
Almost 0 difference in noise level, but if you use all three vibrants, its 100% smooth (cannot distinguish between bangs), very little burble, while with one vibrant, it does not sound ricy, more like a race mini, just quiet enough for daily use, and it burbles like crazy.
Both ways are very quiet under 2.5k rpm's and above 4.7k they become fairly quiet, but you can actually hear the air rushing out of them (mine are all 100% straight through)

Im dynomatting at least my trunk area to make long drives on the interstate have no drone, but I love it so far.

Here is a video of the setup (I had a ripped flexpipe two days ago when I filmed this, ordered a new one, came in next day and welded it in yesterday. If you want an updated video I can snag one for you tomorrow)
http://www.youtube.com/user/soccerbu...4?blend=9&ob=5

Oh, and great place to get cheap 304 stainless bends:
(tightest radius, trusted company, 304, not 409 (mine is 409, a friend found this during his m5 rear mount turbo build after I started my project 6 months ago) http://www.mandrel-bends.com/catalog...-bend-546.html

any other info needed, just PM me!

 

W/O Reading all of that ^^

To answer your question though, one muffler w/o cat will sound like complete ****. I have a cat-less header, and a full Milltek. It sounds good most of the times, but there are points where it is pure rasp and sounds like a cheap Honda.

IMO do NOT just cut out the whole exhaust, and expect it to sound good. VERY VERY few MINIs actually sound good w/ free breathing exhaust, and one close to stock otherwise will not be one of them.

 

what i think im going to end up doing is just leaving the cat and replacing the stock muffler for a magnaflow. and deleting everything else.

 

I think mine sounds decent http://www.youtube.com/user/soccerbu.../0/pCyavW7qDHY

 

For what its worth.....I did run my car straight for a while. And its not loud.....its obnoxious. Lol....this coming from someone that likes a loud car.
These engines just don't sound deep straight piped at all. The changes that I made was adding magnaflow straight through mufflers and it runs better, sounds deeper, and still has a great tone.
These engines dont like to run with no back pressure either so just because its loud doesnt mean that its the most HP......something I wish honda drivers would grasp! Lol
Also you can tune out the cels if you take the cat out, but it isn't going to make a difference performance wise if you have an after market header bolted up to the back of the engine. If you want to be able to take the header off do a test pipe for track days....but you honestly won't see a jump in your performance without a cat. These aren't chevy v8's that were tuning here lol

 

Check theese out first: My setup exhaust wise is, gutted cat on an RMW "shorty" (I would find a better quality header, if you dont like small leaks) 2.5 inch piping straight back (removed the battery box), all piping was heat wraped, into a Borla straight through turbo muffler, and out a Chevy Durramax tip. It has great sound at 6000 feet of altitude, but is way too loud! I can only imagine this setup at sea level, you would need earplugs!

The first vid's of the Sprintex, the new tune has fixed the idle in vid #1. https://picasaweb.google.com/don.sui...age_May22_2011#


Me blowing by another club member on a club run. http://www.youtube.com/watch?v=DE1cV6bBXSY

 

That doesn't sound too loud. But I guess I'm used to my setup which is plenty loud lol.
I've got the megan racine header on mine with 1 cat, a 12" smitty, and the magnaflow straight through.
It just rumbles at idle a lil and comes to life with the throttle open! Hahaha

 

i still dont know what to do becuase im getting that rotten egg smell wich means its the cats going bad.

 

If you think the cat is going south, and you really want to, go ahead and cut it out. It will trigger CEL's and make the car quite a bit louder and there is no improvement or degridation in power. Just be prepared to swap back to a catted header if you don't like it.

 

Cats can fail in a number of ways....
they can fail chemicaly, where the platinum/pladidum is contaminated with excess sulfer or lead, and then work at reduced effecency, or not at all...this will result in a light, just like when it is removed. No increase in back pressure from failure.
The more troublesome faiure is mechanically....where they fail internaly (mostly) from overheating (running too rich) or crack....and then partially block the flow of gas, leading to power loss or causing full stoppage of the motor....
just a smell without a light might not be the end....try a different brand of fuel....and remember, you have 2 cats....the header precat, and the bigger 2nd one...
the milteck/stratosphere clone sounds nice....and makes power....
the one ball is cheap, but mostly for weight...a slight sound change.
Others are around...some single sided cheap ones drone pretty bad...bad are cheaper...get an exaust you can live with....you will be hearing it all day....

 

While everyone is talking about straight pipes I figure I would run this idea around the thread. I have an 03 MCS. I was wanting to keep the stock header for now because of money. But after the cat I was wanting to put 2 SLP Loud Mouth Series 1 resonators on it would go cat 4in piping SLP 4in piping SLP and then i was going to divert the piping around the battery box and out the stock location. I was just wondering what to expect from thing I imagine it would be louder than stock but would I lose bottom end and possible some boost. What is everyone's thoughts on this.

 

4" Is WAY too BIG! You will actually loose power with it. Stay with a 2.5" or at verry most a 3", and it sounds alright.

 

I meant I was going to put 4" of piping between the cat and the first resonator then 4" of piping between the first resonator and the second resonator. Then have piping all the way back to the exit in the bumper. The resonators are 2.5" so I was going to do all 2.5" piping. I was just wondering if I went with this set up if I would lose HP or bottom end power. The resonators don't have any baffling. I want somthing that sounds good thats cheap.

 

It should work out for you then. Its going to be LOUD but since you are having bends in the pipe it should smooth things out a bit. You might loose a little low end grunt but not a whole lot.

 

If it where you what would you do to your exhaust if you had limited money or would you get somthing else for your mini

 

For a cheap mod I would go ahead and do it. I normaly like loud car's though. Ive ran a straight through (Cut battery box) into a Borla muffler on my "S" the entire time I have had the car.

Now I am going to try my best to quiet it down when I get the new engine. Guess I really am growing up some.

Exhaust ststems on R53's dont offer much power gain at all, but it is nice to be heard sometimes. For cheap, check out the 15-17% S/C pullies if you dont have one. They are less than $150 new and can be found used cheap, instalation can be a bit pricy though if you cant do it yourself. That is the biggest single performance gainer for R53's.
You can get an intake to bring out the S/C whine (Or mod your stock box), but again performance is debatable.
Or save up for a good tune... There is still some good tuners out there, and a custom remote tune will cost @ $350-$450 plus dyno time. Nothing can beat a pullied car with minor bolt ons with a good tune in regards to drivability.