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Discussion Starter #1
So what brand is currently the best Downpipe for a gxp? I was going to get the solo but I have read a bunch of stories of it melting and failing so now I am nervous. I plan on getting an exhaust also and was thinking solo there too but do they also have issues? I want a quality unit that will last but flow better than stock.

Also I have read that the GXP performs better with keeping the cat rather than eliminating it (on every other car I have owned eliminating it was better) why is this?
 

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A new downpipe gets you nothing - it is the low restriction CAT that makes an improvement (but only if you have something other than the factory tune, otherwise you get nothing).

The Solo CAT is very good. Not sure I have ever heard of a staiinless steel or high alloy steel downpipe melting, so I don't know what you are talking about.
 

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Discussion Starter #3
Isn't the cat in the downpipe on this car like it is on most other turbo cars?

Do a search on the forum, I read about it here on this forum. that is why I am concerned.

Right now I just have the GM tune but down the road I will get a custom tune, this is why I am setting it up for that.
 

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Isn't the cat in the downpipe on this car like it is on most other turbo cars?
The CAT fits between the manifold and downpipe.
 

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Discussion Starter #5
Ok so the question stands but in a different form. What is the best replacement cat? or is it better going catless? looking for recommendations.
 

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I am interest in this as well so subscribing.

It was my understanding the car and downpipe are one integrated unit.


Sent from my iPhone using Autoguide
 

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I have Solo exhaust and high flow cat and have a SuperChips tune. I found performance improvement when I added the high flow cat. I have not a any problems with either one. Have had the exhaust since 2008 and the cat for about a year.
 

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The CAT fits between the manifold and downpipe.
I have no idea what you're talking about. The catalytic convertor is part of the downpipe, and goes between the turbo, and the cat-back. When you replace the downpipe, you can choose to get a high flow cat, or a catless downpipe.

Either will require a rear O2 sensor extender, or HPTuners to disable the 0420 DTC or you will get a check engine light for low catalytic convertor efficiency.
 

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Matter of terminology. The CAT bolts between the manifold and the rest of the system. If you want to call the CAT a downpipe, so be it. Certainly a replacement pipe without any CAT in it has been termed a downpipe.

What do you figure that melting thing was about - ever heard of a steel pipe melting in use? He must have been thinking of a CAT getting hot when clogged and possibly causing heat damage to something around it?
 

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Discussion Starter #11 (Edited)
Thank you, that is what I thought but I didn't want to argue about it because I wasn't sure. What wpjohn said made no sense and my last car (also a turbo) it was the same as you say (cat in downpipe). :yesnod:

I have no idea what you're talking about. The catalytic convertor is part of the downpipe, and goes between the turbo, and the cat-back. When you replace the downpipe, you can choose to get a high flow cat, or a catless downpipe.

Either will require a rear O2 sensor extender, or HPTuners to disable the 0420 DTC or you will get a check engine light for low catalytic convertor efficiency.
 

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Discussion Starter #12
What do you figure that melting thing was about - ever heard of a steel pipe melting in use? He must have been thinking of a CAT getting hot when clogged and possibly causing heat damage to something around it?
Search the forum and you will see solo downpipes failing by melting, that's what I was referring to. I am still leaning toward a solo DOWNPIPE but I am concerned and wanted to see if there is a better aftermarket unit.
 

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Search the forum and you will see solo downpipes failing by melting, that's what I was referring to.
Took a look and failed to see any - can you point me at any examples - I'd be interested.
 

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Search the forum and you will see solo downpipes failing by melting, that's what I was referring to. I am still leaning toward a solo DOWNPIPE but I am concerned and wanted to see if there is a better aftermarket unit.
Was the melting cats on a 2.4L or a 2.0L? We have seen them melt on a 2.4L as there was some issues with cracking manifolds that would allow air to enter right before the cat on the 2.4L cars, the extra air with the extra fuel basically would cause a secondary burn in the cat and melt it down.

We have been working with cars that have had the SOLO high flow cats installed on the 2.0L for years now and never seen a problem here with them on the 2.0L.

As for which is best, high flow cat or catless, that depends on a couple things. The catless will give you more power, better spool although only slightly compared to the high flow cat. The downside is that it may not be legal in the state you are in and also I personally do not like the sound of catless 2.0L cars, but that is a personal taste thing.

Hope that helps,
Dave
 

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Discussion Starter #15
Thanks for the feedback dave, I just went and looked again and your right it was on the 2.4l cars. I guess a solo DP is the way to go on the 2.0l. now I just need to decide catless or low flow. Probably will go lowflow otherwise I would have to change back to stock every 2 years for a smog check here in California. I really would love catless but living in an apartment makes working on your car next to impossible so changing it every couple years isn't totally practical. UGGG

Was the melting cats on a 2.4L or a 2.0L? We have seen them melt on a 2.4L as there was some issues with cracking manifolds that would allow air to enter right before the cat on the 2.4L cars, the extra air with the extra fuel basically would cause a secondary burn in the cat and melt it down.

We have been working with cars that have had the SOLO high flow cats installed on the 2.0L for years now and never seen a problem here with them on the 2.0L.

As for which is best, high flow cat or catless, that depends on a couple things. The catless will give you more power, better spool although only slightly compared to the high flow cat. The downside is that it may not be legal in the state you are in and also I personally do not like the sound of catless 2.0L cars, but that is a personal taste thing.

Hope that helps,
Dave
 

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DDM installed a Solo Hi Flow Cat on my Sky over the memorial Day weekend in 2011
16 Months later, and no issues.

Since you have the GMPP tune, you will see around a 25rwhp gain in power with Solo's
 

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Discussion Starter #17
DDM installed a Solo Hi Flow Cat on my Sky over the memorial Day weekend in 2011
16 Months later, and no issues.

Since you have the GMPP tune, you will see around a 25rwhp gain in power with Solo's
Wow that is actually more than I expected from I high flow, I would have expected that kind of gain on a catless though. What exhaust are you running, maybe that is part of your gain? I will most likely get the downpipe and get it installed within the next 2 weeks. Initially I will probably maintain stock exhaust and just do the downpipe.
 

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Someone other than me did the before and after dyno.
I have the magnaflow 3" catback
But i have no idea what they had

This is pretty accepted knowledge with the cat
 

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From what I've seen from limited dyno time while tuning, the catless downpipe doesn't really net me much more peak torque, but it comes in 100-200rpm earlier. But it does wonders for peak hp in the 4500-5500 range. I was seeing 20+whp gain in that region on a Mustang Dyno pre and post catless downpipe.
 

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Since you won't be taking it off and on every 2 years, make sure what ever you decide on is CARB (California Air Resource Board) approved. Part should come with sticker that has an assigned CARB # on it. BTW, rumor has it California is going to annual smog checks.
 
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