Exhuast questions.

[TCM05GT]

First I want to thank everyone for their help so far. Everyone is very patient. Especially since some of these questioned are answered over and over.

First question. What exactly is a "downpipe" used for? Is it to replace the cat and u-bend?

Next question. I saw, in a post, where someone said that you could just replace the mufflers to get better sound. So.....which mufflers are the best to get the sound I want? which is.....a deep low rumble. As close to a v-8 as possible. I would like for it to be heard at idle. Then louder at acceleration. Thanks.


Tony

[99prixgt]

First I want to thank everyone for their help so far. Everyone is very patient. Especially since some of these questioned are answered over and over.

First question. What exactly is a "downpipe" used for? Is it to replace the cat and u-bend?

Next question. I saw, in a post, where someone said that you could just replace the mufflers to get better sound. So.....which mufflers are the best to get the sound I want? which is.....a deep low rumble. As close to a v-8 as possible. I would like for it to be heard at idle. Then louder at acceleration. Thanks.


Tony

A downpipe is a pipe that comes off of your exaust manifolds and goes down into the rest of your exhaust system. I got a zzp downpipe to get rid of the ugly u-bend in my stock downpipe. Since you have a newer gen GP your stock one dosen't have a u-bend in it.

Not sure what year you have but this is off an 05'





To get a sound of a v-8 with these cars, is just about impossible. I have the SLP exhaust on my car and yes it is raspy at WOT, and i get all the exhaust drone in the world, but i like it. Below is a sound clip of mine so you can get an idea. IMO SLP is one of the better sounding mufflers, everyone likes a different sound, but slp's catback was also alot easier on my wallet. Typically your stock catback isn't restrictive till around 300whp. So if you want better sound just mufflers would do the trick.

My Grand Prix GT- Video

[ROTTMAN]

I would lose the resonator. Exhaust shop can do this for you fairly cheap by replacing it with a straight pipe. As far as the mufflers that is a personal preference but go on you-tube theres lots of sound clips you can listen to but its hard to judge even by watching those. I have no u-bend and no resonator and magnaflow mufflers. It sounds great at idle but cruising at normal hiway speeds sucks. The car sounds like its bogging when its in over drive and the drone gets very irratating. Maybe this wont bother you, everyones different. In retrospect I would have left the stock mufflers on...you will never make it sound like a V-8.

[99prixgt]

keeping your resonator or adding one will only help you with exhaust drone.

[TDCRacing]

I would advise to keep the resignator. I don't like the sound of v6's that have exhaust but the dynomax turbo mufflers are what a lot of people use.

[UR LOSN]

When you add a 3" DP.... getting one Cat less improves exhaust sound!!! the stock mufflers have a DEEP rumble.....you would never know until you take off the cat.

the minute you take the resonator off, you will have nothing but Rasp. I hate Rasp.

[TCM05GT]

Thanks. And the sound was fine. I do like that.


Tony

[TCM05GT]

When you add a 3" DP.... getting one Cat less improves exhaust sound!!! the stock mufflers have a DEEP rumble.....you would never know until you take off the cat.

the minute you take the resonator off, you will have nothing but Rasp. I hate Rasp.

Ok. Three questions.
1) The new downpipe has a resonator in it. correct?
2) When you put on a new downpipe....the factory cat comes off?
3) I can take it all off and install the downpipe myself?


Tony

[TDCRacing]

Ok. Three questions.
1) The new downpipe has a resonator in it. correct?
2) When you put on a new downpipe....the factory cat comes off?
3) I can take it all off and install the downpipe myself?


Tony

1) No. Downpipes do not come with resignators.The resignator is located AFTER the downpipe going tward the back of the car.

2) Yes. Since the factory cat is located in the downpipe it does come off. You have the option of purchasing a down pipe with or without a CAT. The Downpipes WITHOUT a CAT are called ''off road down pipes''.


3) Yes. You will need a ratchet with an extension and a socket. A jack. Jack stands. And some PB blaster to loosen the rusted on bolts.

[TCM05GT]

1) No. Downpipes do not come with resignators.The resignator is located AFTER the downpipe going tward the back of the car.

2) Yes. Since the factory cat is located in the downpipe it does come off. You have the option of purchasing a down pipe with or without a CAT. The Downpipes WITHOUT a CAT are called ''off road down pipes''.


3) Yes. You will need a ratchet with an extension and a socket. A jack. Jack stands. And some PB blaster to loosen the rusted on bolts.

Oh ok. Got it. Thanks a lot.


Tony

[TDCRacing]

No problem!

[06GPNA3800]

An off road pipe for power gains is pretty much pointless. Many tests have been done that prove that not running a cat has very few gains and allot of losses on a stock ECM'd car. You will piss the PCM off and throw CEL light all day. If your trying to make power, make it with cat in place.

[TDCRacing]

I agree with you...To a point. Please explain the losses in performance that it will cause. And it does not do ANYTHING to the PCM. The SES light will set and that's all that will happen.

[06GPNA3800]

It does have to do with the PCM. I've had several FWD GM cars pull timing because of un know flow across the cat. I'll take a video of my launch computer or better yet i'll just hook up my data logger tomorrow and then run it with another secondary o2 sensor just zip tied up out of the way. I gurantee it will pull timing and make it run richer with a stock ECM. Not to mention the fact that theres no reason to remove the cat in the first place. To me if i'm going to make mods and make more power, its going to be the right way. Hacking the cataystic converter out surely isn't the right way just my 2 cents.

[Reptile]

The rear O2 sensor has nothing to do with the tune of the car. The primary one located in the manifold is what the PCM uses for data. Removing the code in the PCM for the post converter sensor eliminates a SES.

While the converter may seem restrictive, some people opt to go without it, and others run great times with it in place. Tranyman's car will run the same times with or without the catalytic converter...so it's just a matter of preference in most cases. Offroad pipes are cheaper, so most people go with those if they can get around emissions.

[TDCRacing]

Sir. Stop. Please. I can promise you that all that o2 sensor's purpose in the cat is to monitor the cat to ensure it is working properly.

I have been inside every table inside of the PCM and the only one that has anything to do with the CAT is the CAT over temp protection tables and that has to do with the ECT sensor. And that is it. When the ECT get's over 282*F it enables the over temp protection and comands a richer AFR to cool the CAT down.


Your launch with that scanner will show me nothing. You're likley pulling timing because of TM not being disabled.

[06GPNA3800]

"You're likley pulling timing because of TM not being disabled" The argument was with a stock ECU correct? I'm completely aware of the function and purpose of a converter and the associated sensors. All i was stating that on a stock ECM the car will pull timing if there is something wrong with either o2 sensors, among many other sensors. My 2006 under the same conditons and very close ambient tempature and load pulls quite a bit of timing the last few days because of a P0411 code coming up for an air injection issue. Any time the code is set it pulls timing. There is no change in fuel trim. I can send you the data from my logger, maybe you can tell me why and how it does it. I'm not trying to be a jerk or a know-it-all. I don't need a forum to justify or satisfy the ownership of any of my vehicles. But it seems the over all outside involment in this website is limited and i can see why.

[TDCRacing]

Correct. Stock PCM has TM ENABLED. I will agree that some of the sensors going bad will cause timing to be pulled. IAT for instance. But there is no certain amount of timing that will be pulled if the o2 sensor goes bad. It's not like if the o2 sensor goes bad it pulls 4* of timing off the bat...Or even at all.


That is incorrect. Any time you have an ses light on it does not pull timing. If you have an air ''injection issue'' or if you have a code set for a vacume leak then you're STFT and LTFT WILL be WAAAAY off. Pegged out to be exact.

Sure I would not mind looking at it for you.

I'm not tring to sound like an ass either. So sorry if if was.


But either way, The o2 sensor in the cat is simply there to make sure the CAT is working properly. It does not control fuel or timing or anything except a light.