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What do you think?

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  #1 (permalink)  
Old 28 Feb 2012, 07:04 pm
Fresh Cruiser
Join Date: Mar 2011
Location: L.A. (Lower Arkansas)
Posts: 8
Question What do you think?

Hi guys and gals,
First off I just wanted to say that the wisdom on here is well appreciated and put to good use. I have a 2002 pt cruiser touring N/A. Currently it has a 2.5" magnaflow catalytic converter with 2.5" Borla cat back exhaust (free flow). When I first got the cruiser it was cool but now it's just way too loud and raspy for me and I can't stand the drone any longer. So what I had in mind was keeping the magnaflow cat then getting a 2.5" to 2.25" reducer and get the exhaust pipe from rock auto and then get the DynoMax muffler (#17732) like Crewzin' suggests. Does anyone see any problems with this? Will I get the little amount of back pressure I need back and kill the loud and raspy drone? I was just wondering because a stock catalytic converter is over $200.00. Any advice or opinions are well appreciated.
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Old 28 Feb 2012, 08:15 pm
Obsessed Cruiser
Join Date: Nov 2007
Location: Mooresville, NC
Posts: 5,324
Default Re: What do you think?

In my opinion, you are hitting the nail exactly on the head. I've seen many a PT Cruiser NA out there running a dual borla that's 2.5" and even a few 3"ers. NOT GOOD FOR AN NA! If you run a full 3" exhaust, you're basically giving it almost no backpressure and on a normally aspirated engine you're asking for a lot of trouble. Not only do you chance losing power and acceleration (99% chance of that), but you're asking for more trouble. The exhaust temps on the NA run fairly hot, not as hot as a turbo but still fairly hot, around 3000 degrees at full temp. A portion of the reduction in porting the output allows your engine to cool down over a specific period. I've had friend running open headers who shut off their engine in their driveway during the winter, and they never got to restart it again as they ended up with warped heads, bent valves, etc. Having no protection on the exhaust side of the engine from rapid cool down is asking for a lot of trouble.

Add to this, you're car is controlled by a PCM which uses all the measurements for fuel to air ratios, exhaust temps, etc., etc., etc., and unless you've got yourself a good diagnostic OBD tool that allows you to change settings, running an NA with a non-tuned exhaust throws of EVERYTHING. Oh sure, most guys don't notice any difference, but here's a statement of fact: Anyone driving an NA PT Cruiser who blows out their exhaust rather than leaving it with factory spec'd back pressure, and they tell you that "oh boy I've gained in horsepower", is a complete and total liar. Now, they may think they are not lying, they may actually believe what they tell you - but I've got at least a half dozen friends who went on the dyno with me during tuning week at Michael Waltrip's shop, two PT's and four Neons, and every single one of them had reductions in horsepower because like idiots they went with those stupid crapanese fart can exhaust systems.

I had been teasing them like crazy and every single guy shut the h3ll up when I pulled up on the dyno and let loose at WOT in 3rd gear. We had at least a dozen Honda and other ricer boys walk up and stare, mouth's agape, at me going from 225 to 268 hp in a one hour period. Hell, even the guy that was running the garage for MW came out to see what the heck all the hubbub was about on the dyno. They gave me a free second hour to continue tweaking my tune because no one else wanted to climb aboard while I was there. Were too many guys embarrased! hahahaha...

So, reading what you've posted I would agree with you 100%. I think you'll find that not only do you get a better resonance out of your exhaust system, but I believe you're going to find that it's running smoother at speed and that you've got just a bit more oomph when you try passing someone.
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Old 29 Feb 2012, 03:13 pm
Fresh Cruiser
Join Date: Mar 2011
Location: L.A. (Lower Arkansas)
Posts: 8
Smile Re: What do you think?

Thanks a lot chromenut. I just wanted to make sure I was headed in the right direction with keeping the free flow cat and bumping the the cat back down to 2.25" with a chambered muffler. Well I'm off to order some parts. Thanks again.
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Old 29 Feb 2012, 10:03 pm
PTpreacher's Avatar
Cool Cruiser
Join Date: Jul 2011
Location: Northern Ca. Arcata,
Posts: 377
Default Re: What do you think?

Hey Chrome,

You are right on! I used to race motorcycles and I put big exhaust on it and lost all my lower in power. I suppose it would be ok if you were running on the salt flats, but it didn't
help my flat-track racing nor my Moto-cross racing. Also, once I ported and polished a motorcycle and when I would come off the throttle it would go for several feet before it
would back off....just kept going like full throttle....some of the roughness inside there is meant to be in there....LOL Just my thoughts, PTpreacher
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