3" DP on stock exhaust?

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3" DP on stock exhaust?

Postby bluntninja » Sat Jul 28, 2012 2:27 pm

SO I have my motor out and would like to delete the cat while it is. I really don't have the money to do a full exhaust atm, but could afford a nice downpipe. My concern is most DPs I can find seem to be 3'', is there a way to mate this to my stock exhaust? Or a smaller diameter downpipe option? Or do I have to replace the whole system? Any help or insight would be greatly appreciated!
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Re: 3" DP on stock exhaust?

Postby underscore » Sat Jul 28, 2012 2:52 pm

I put in a 3" downpipe with everything else fully stock, it ran a lot better and had a bit more power with just the DP, once you go to a full 3" it'll be even better.
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Re: 3" DP on stock exhaust?

Postby bluntninja » Sat Jul 28, 2012 4:15 pm

Awesome! just for clarification, a 3'' downpipe will bolt directly to my stock pipe with no modification??
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Re: 3" DP on stock exhaust?

Postby underscore » Sat Jul 28, 2012 8:50 pm

It should, you might need to loosen the midpipe to wiggle things around.
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Re: 3" DP on stock exhaust?

Postby jaydog82 » Sat Jul 28, 2012 10:10 pm

You also may need to get a new gasket if the do does not come with one. I found that the aluminium reusable 3 inch 3 bolt hole ones that Oreilly auto parts sells them for $15-$20.
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Re: 3" DP on stock exhaust?

Postby DeeCee » Sat Jul 28, 2012 10:19 pm

Ko racing does a 2.5 decat: http://www.koracing.net/viewproduct.php ... roduct=105

Personally, I would save up your money and buy a complete setup all in one. That way you know that equipment will fit instead of being a bit at a time.
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Re: 3" DP on stock exhaust?

Postby tw2 » Sun Jul 29, 2012 12:55 am

Nearly all the downpipes are designed to work with the stock exhaust, whether they do or not depends on how well they are made. It should be fine to get a DP now and do exhaust later, I did. Most exhausts do not come with the downpipe anyway. I agree the 2.5" one is excellent. It wont hurt to use a 3" one but I doubt you will get a lot of extra gain from it with the stock exhaust. Most cheap ones are poorly made and don't have the clearance to allow the wastegate to open properly. Get one from ats, ko or berk tech.
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Re: 3" DP on stock exhaust?

Postby 4rsnduction » Sun Jul 29, 2012 1:02 am

A cheap $100 ebay downpipe in 3inch size will fit your stock 2.75inch system no worries, i did exactly the same thing in 2009.
Had the motor rebuilt and put on a 3inch dump pipe but couldn't afford the rest of the exhaust.
The engine builder broke out the digital micrometer and measured the inside diameter of the stock exhaust system and the downpipe.
The bolt holes all mated up perfectly to the stock exhaust system, with the use of liquid gasket there was a perfect seal so no exhaust leaks.
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Re: 3" DP on stock exhaust?

Postby tw2 » Sun Jul 29, 2012 1:08 am

4rsnduction wrote:A cheap $100 ebay downpipe in 3inch size will fit your stock 2.75inch system no worries, i did exactly the same thing in 2009.
Had the motor rebuilt and put on a 3inch dump pipe but couldn't afford the rest of the exhaust.
The engine builder broke out the digital micrometer and measured the inside diameter of the stock exhaust system and the downpipe.
The bolt holes all mated up perfectly to the stock exhaust system, with the use of liquid gasket there was a perfect seal so no exhaust leaks.

It seems they are not all created equal. Did you have wastegate troubles?

To the OP, it is a quick and easy job to grind the downpipe to get rid of the sticking wastegate trouble if you get an ebay pipe.
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Re: 3" DP on stock exhaust?

Postby bluntninja » Sun Jul 29, 2012 1:52 am

Thanks for all the awesome information!! This site is a life saver. I'm not familiar with the wastegate issue and I'm actually in the process of trying to pickin up a cheap ebay DP via http://www.alltrac.net/phpBB2/viewtopic.php?f=15&t=44766 After a little quick googling it looks like it catches on aftermarket gaskets as well as the bend of some brand downpipes.. does anyone have any more info or a good link on where/how to grind it down?
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Re: 3" DP on stock exhaust?

Postby jaydog82 » Sun Jul 29, 2012 2:20 am

BayareaAT has one for sale for 75 shipped.
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Re: 3" DP on stock exhaust?

Postby 4rsnduction » Sun Jul 29, 2012 2:48 am

tw2 wrote:
4rsnduction wrote:A cheap $100 ebay downpipe in 3inch size will fit your stock 2.75inch system no worries, i did exactly the same thing in 2009.
Had the motor rebuilt and put on a 3inch dump pipe but couldn't afford the rest of the exhaust.
The engine builder broke out the digital micrometer and measured the inside diameter of the stock exhaust system and the downpipe.
The bolt holes all mated up perfectly to the stock exhaust system, with the use of liquid gasket there was a perfect seal so no exhaust leaks.

It seems they are not all created equal. Did you have wastegate troubles?


I didn't have any problems with the wastegate BUT at the time of the rebuild i told the mechanic about the rumors on the internet and how the wastegate may not open fully, we both tested it at his workshop with compressed air feeding the wastegate actuator, it opened fully and did not stick.

I have been driving for 30,000km's now and never a single problem, i drive my car likes its stolen and i have never had a "cracking" problem like everyone with an opinion talks about but thats not to say that your experience will be as flawless as mine
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Re: 3" DP on stock exhaust?

Postby tw2 » Sun Jul 29, 2012 2:52 am

bluntninja wrote:Thanks for all the awesome information!! This site is a life saver. I'm not familiar with the wastegate issue and I'm actually in the process of trying to pickin up a cheap ebay DP via http://www.alltrac.net/phpBB2/viewtopic.php?f=15&t=44766 After a little quick googling it looks like it catches on aftermarket gaskets as well as the bend of some brand downpipes.. does anyone have any more info or a good link on where/how to grind it down?

Search on mr2oc.com and become a member if you are not already as there is heaps of useful info on the 3sgte. If you get a bracket for the bottom of the DP they are much less prone to cracking. I am pretty sure both koracing and ats sell them separately. $20 for a nice steel triangle bracket or you can make one yourself.
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Re: 3" DP on stock exhaust?

Postby DeeCee » Sun Jul 29, 2012 6:57 am

Actually the lesson is not just about something fitting. Pairing flanges isn't exactly rocket sience. The lesson is to ensure that the op understands working and modifying efficiently and achieving better advantages rather than something bitsy
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Re: 3" DP on stock exhaust?

Postby underscore » Sun Jul 29, 2012 5:58 pm

At the very least gut the stock downpipe because the backpressure from a clogged cat will be hard on the car.

As far as cracking and brackets, I think there are a lot of factors to that, such as flexpipes in the midpipe.
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It's for sale! http://www.alltrac.net/phpBB2/viewtopic.php?f=64&t=52181
Build thread http://www.alltrac.net/phpBB2/viewtopic.php?f=44&t=44216
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