Do I need to use a highflow cat? or no cat?

[NCturbotalon]

I am not sure if i should buy the 3in megan down pipe.would it bolt right up?and would it be better on the stock motor with no catalytic converter or with a high flow catalytic converter?As far as horsepower and back pressure?I will have then twin lube muffler. only one i found in my price range that was for a fwd talon tsi?so any help would be helpful.

thanks
josh

 

[simple jake]

Unlike N/A cars, turbocharged cars do not need back pressure to create power. As far as making power, go with no cat. If you're worried about passing emissions, then stay with the high flow cat.

 

[NCturbotalon]

ok thanks but i ws told u can remove the cat. as long as u keep your o2 sensors you was ok and the check engine light wouldn't come on is this true?

 

[bo0st]

Your CEL may come on, but it'll be worth it. No cat = some power gains

 

[Laproject06]

you can keep your o2 sensors you won't passing emissions, once you remove the cat go with Str*8 pipe and high-flow cat w/ resonator so it won't be so loud

 

[NCturbotalon]

ok where would I get that from for a good price?and how would i run it with a good downpipe?is a stock turbo flange on 91 talon two bolt or four bolt?

 

[racerx4g64s]

Hi flow cat is the best! Not worth getting in trouble (inspections failure) for the small amount of HP/TQ loss. Or the annoying CEL light!

 

[needsy]

Run a cat and save yourself the trouble with emissions. It won't cost you that much power, and it will allow your engine to run more efficiently for daily driving.

 

[DSM_munky_man]

The cat has nothing to do with making the engine run efficiently in this case. It is just taking the innefficiencies of excess fuel and burned gasses and what not and converts them to not as lethal chemicals to the environment so we dont kill the pengiuns.

The only way it would help with efficency is if he was an obdII or happen to have a post cat o2 sensor, then it monitors whats happening after the cat to correct the issue in the engine, but him being a 91 that is not the case.

 

[gusu]

I'm not sure how your emissions work in California but I'd assume they do a tailpipe test to see if your cat has failed. If not just keep your emissions crap on and do whatever else. You can always cheat the system by bringing it in with 50/50 E85 and obviously typical premium gas. They do have a way to see if you are using ethanol to cheat in some areas but I've never heard of them doing that in California.

You probably should run a cat since you live there. I almost moved there to go to UTI but honestly... I don't want to put up with all the stupid laws that state has. Plus I don't feel like putting all new emissions crap in my car just to be able to drive it around.

 

[needsy]

The cat has nothing to do with making the engine run efficiently in this case. It is just taking the innefficiencies of excess fuel and burned gasses and what not and converts them to not as lethal chemicals to the environment so we dont kill the pengiuns.

The only way it would help with efficency is if he was an obdII or happen to have a post cat o2 sensor, then it monitors whats happening after the cat to correct the issue in the engine, but him being a 91 that is not the case.

Right, my bad. I got stuck in the 2g frame of mind.

 

[9!'clipseDOHC]

I am not sure if i should buy the 3in megan down pipe.would it bolt right up?and would it be better on the stock motor with no catalytic converter or with a high flow catalytic converter?As far as horsepower and back pressure?I will have then twin lube muffler. only one i found in my price range that was for a fwd talon tsi?so any help would be helpful.

thanks
josh

Josh, let me start with your first question/statement. You are not sure if you should buy a 3" downpipe. I just took at look at your mod list, it says all stock. The first thing you should do is come up with a reasonable goal for your car and budget for you to work with, otherwise this hobby gets really expensive, really fast. The second thing you should do is take a look at the upgrade paths, they have been tested and proven time and time again. Start with stage 0, maintenance. After that is done, then it is a good idea to start by opening up your intake and exhaust systems so yes, a downpipe is a good idea.

Second question, High-flow cat or test pipe? Ask yourself some questions: Does your state do tailpipe emissions testing? Do you mind breaking the law for a slight power increase? A high-flow cat is a great option for a street driven performance car and you can also swap it out for a test pipe when you go to the track. You can also run a test pipe all of the time, many people do, but the choice is up to you.

Third question, back pressure. Like mentioned above, back pressure isn't a concern on a turbocharged engine because the turbo creates all the backpressure that it needs. The rest of your exhaust should be as free flowing as possible. You definitely want a straight threw muffler, not baffles like an N/A performance car.

Here are some high flow cat options I just posted on another thread:

RRE sells a bolt in high flow cat for $190 Eclipse Exhaust System Upgrades

JNZ sells a 3" cat for $110 which can be welded in or you can weld the flanges onto it to make it bolt on. Vibrant Round Metal Core Catalytic Converter, 3" : JNZ Tuning

MAP sells a couple for $179, same thing though, either weld them in of weld your own flanges on. High-flow Cats & Test Pipes - Exhaust System - DSM - Mitsubishi - Modern Automotive Performance

Horsepower Freaks has a 3" Magnaflow hi-flow cat for $72 that you can weld in or weld flanges on. Magnaflow Universal Catalytic Converters from HorsepowerFreaks and the flanges for $25 each: Vibrant T304 Stainless Steel Exhaust Flanges from HorsepowerFreaks

Here is the 3" 2 bolt flange from STM for $23 each: STM: FLANGES | GASKETS | WELD-ON | EXHAUST COMPONENTS

I would either get the bolt on RRE cat or if you want to save a few bucks, the Magnaflow cat and 2 flanges to have welded on so that you can swap the cat and test pipe back and forth.

Hope this helps!

Hope this helps!

 

[PWR4HIM]

Well it says you have a '91 talon, so in NC it will be a visual inspection only, so as long as your straight pipe looks like a cat it will pass inspection. Seriously, that is how the book reads for non obd inspections for NC. It ONLY has to pass VISUALLY...thats it for all emission systems. No tail pipe sniffer. And on a '91 there will be no CEL either.

I went with a ebay Stainless 3" downpipe, and a Megan straight pipe, o2 housing and cat back on my '90. The ebay cat back looks like great quality once I got it in, no disappointment to me and it saved me about 60 bucks. And it will all bolt up.

But read up on 14B boost creep it you plan on running a full 3" exhaust with no cat. You need to pull the hot side of the turbo and port it.
Go to vfaq.com they have a good write up and there are a bunch in the turbo section on here as well.

By the way...Nice to see another N. Carolina guy...where is Wilson, NC at. I am south of Winston Salem.

 

[LiquidX]

The easiest thing to do is get the down pipe modified for a cat converter that is either bolt on or v-band flanged. Flange or v-band the cat and have the exhaust shop v-band or flange a test pipe as well for you. It's not illegal for them to make the pipe, they just cannot install it for you.

This way you will have both a hi flow cat and a test pipe for your "track days"

 

[9!'clipseDOHC]

Well it says you have a '91 talon, so in NC it will be a visual inspection only, so as long as your straight pipe looks like a cat it will pass inspection. Seriously, that is how the book reads for non obd inspections for NC. It ONLY has to pass VISUALLY...thats it for all emission systems. No tail pipe sniffer. And on a '91 there will be no CEL either.

I went with a ebay Stainless 3" downpipe, and a Megan straight pipe, o2 housing and cat back on my '90. The ebay cat back looks like great quality once I got it in, no disappointment to me and it saved me about 60 bucks. And it will all bolt up.

But read up on 14B boost creep it you plan on running a full 3" exhaust with no cat. You need to pull the hot side of the turbo and port it.
Go to vfaq.com they have a good write up and there are a bunch in the turbo section on here as well.

By the way...Nice to see another N. Carolina guy...where is Wilson, NC at. I am south of Winston Salem.

I have a full 3" exhaust on a 14b and it used to creep a LOT until i bought a megan racing recirculated o2 housing and now I have zero creep. A lot of people will say that the o2 housing won't really help with creep, you have to port the hotside and the flapper, but I can tell you from experience that the o2 housing makes a huge difference.

 

[NCturbotalon]

well thankyou all but i think i am going to run with no cat. just because like the guy said from n.c there is just a basic walk around here in n.c i don't know much about having a creep or what ever it is. but where can i buy that housing so i dont have to deal with it?

 

[9!'clipseDOHC]

well thankyou all but i think i am going to run with no cat. just because like the guy said from n.c there is just a basic walk around here in n.c i don't know much about having a creep or what ever it is. but where can i buy that housing so i dont have to deal with it?

Exhaust gases travel the path of least resistance. The way a wastegate works is when the set amount of boost is reached, the wastegate opens up and exhaust gases that aren't needed are set through the wastegate, bypassing the turbine wheel so as not to create more boost. When you upgrade to a high flowing exhaust system without upgrading the the wastegate passage, even when the wastegate opens up, the exhaust gas still flows past the turbine wheel because that is the path of least resistance. When that happens it i called boost creep because the boost continues to rise beyond the set limit.

The way to fix/significantly reduce this is to make the wastegate passage more free flowing. This can be done by porting the factory o2 housing, buying an aftermarket tubular o2 housing, or porting the wastegate flapper/hole itself. On my 1g DSM with a full 3" exhaust, 14b, and MBC set at 13-14psi. I was creeping to 20+ psi over 4,000 RPMs. After installing a Megan Racing recirculated o2 housing I stopped creeping almost completely. I can hold 14-15 psi all they way to the redline. You get a tubular o2 housing from any of the site venders, I bought mine used off the site classifieds.

Hope this helps!

 

[NCturbotalon]

well thankyou man that really help out! i guees i will but the 02 housing and if it still does it then i will have the turbo thing done. but thank you man

 

[9!'clipseDOHC]

well thankyou man that really help out! i guees i will but the 02 housing and if it still does it then i will have the turbo thing done. but thank you man

You are very welcome!