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Downpipe questions


gk1

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I've gotten lots of general information from my searches, but a few questions remain. I'm not sure if I'm suffering from "preoccupation with inconsequential increments" or not, but I wouldn't be surprised...Anyway, here goes:

 

I've got a stock '08 GT/5mt, and will be going stage 1 soon. I'd like to go to stage 2 soon afterward, with the goals of improving spool and increasing torque.

 

I'm looking at the Harmann Motive, AVO, and Cobb catted DPs. I like the 3" all the way through idea, as I'm also considering AVO mid/y-pipes, but will be keeping stock axle-back. Here's where the (inconsequential?) differences show up.

 

The AVO has the cat close to the turbo end, whereas the others have the cat farther back; is there any performance difference, or anything else worth considering?

 

The AVO also has a divorced wastegate design, whereas the others are bellmouth; same question...

 

The Cobb would have to be modified to mate up with 3" mid/y-pipes; at this level, will there be any benefit to the mid/y-pipe change?

 

I'd like to end up with minimal extra volume, but a slightly throatier exhast tone, if there's any change. No turbo changes are planned, but if a new turbo enters the equation, it would likely be VF52 or similar, nothing huge.

 

Final question, I planned to have the DP coated (GrimmSpeed?); I assume that there are no issues with coating a catted pipe, and that cat placement doesn't factor into this?

 

Sorry for the long post, and TIA for any feedback.

 

George

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I like my invidia. Helps with the sound issues I had with my DWG downpipe. It made a lot of weird hollow whistling noises at low RPM (not a leak, just wastegate actuation). Plus the power is MUCH better. The invidia IS relatively thin walled and increased noise a bit over stock... so you know.
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I have an Invidia DP and Perrin Mid/Y with stock mufflers. It's a bit louder than stock, but not very much. The only issue with the Invidia DP is that you (or your installer) need to grind a notch in the divider in the middle of the downpipe bellmouth. It's easy and it only takes a few minutes. If you search the forum you'll find a picture or two of the notch you need to make.
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Does anyone have any experience with the AVO DP and/or mid- and y-pipes?

 

IIRC, the grinding of the divider is the only fitment issue with current Invidia pipes and 5MT; is that correct?

 

Thanks for the replies so far!

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Does anyone have any experience with the AVO DP and/or mid- and y-pipes?

 

IIRC, the grinding of the divider is the only fitment issue with current Invidia pipes and 5MT; is that correct?

 

Thanks for the replies so far!

 

The divider issue is the only issue you should have if any with the invidia dp. The invidia is a quality piece aside from that one issue. Solid flanges, great fitment. 3 inch diameter piping all the way down.

 

The avo dp looks like a quality product plus you can change the turbo -> dp connection

http://www.avoturboworld.com/avoshop/index.php?cPath=1_58_3_8&osCsid=c0f9c117ad748e3cd077e5071afbaee8

So if you wanted a dp to work with your twin scroll setup if that was your direction than you could. However the avo dp compared to the invidia dp is very expensive.

2008 6mt Legacy Gt Spec B DGM - Not so Stock/Work in progress

2006 5mt Legacy Gt OBP - Sold

2005 5eat Legacy Gt OBP - RIP

 

R.I.P Coxx

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The divider issue is the only issue you should have if any with the invidia dp. The invidia is a quality piece aside from that one issue. Solid flanges, great fitment. 3 inch diameter piping all the way down.

However the avo dp compared to the invidia dp is very expensive.

 

+1, my invidia piece is great, install was 100% on...no grinding needed on mine.

 

FWIW, some tuners believe the divorced wastegate design makes a little more power than non divorced pipes. My datalogs (and butt dyno) show a pretty big jump in HP and TQ over the gutted stock DP I was running.

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+1, my invidia piece is great, install was 100% on...no grinding needed on mine.

 

FWIW, some tuners believe the divorced wastegate design makes a little more power than non divorced pipes. My datalogs (and butt dyno) show a pretty big jump in HP and TQ over the gutted stock DP I was running.

 

Is your Invitia catted or catless? Mine is catted, and the divider needed to be notched. I wonder if that's what makes the difference.

 

The divorce surely doesn't hurt, and probably does help a bit, but an open bellmouth would still be a huge improvement over the stock no-bellmouth design. :) It's just got the wastegate blowing straight into a flat plate, requiring two tight 90 degree turns to merge with the rest of the exhaust. Plus the larger diameter of piping overall. (I'm sure you know this having run both, I just wanted to clarify for the audience that the divider isn't the only reason you got more power.)

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Catless..I researched alot before going with the Invidia and there was some talk that the older design Invidia's (both catted and catless) suffered the divider issue.

 

Absolutly true, I have only run the stock gutted DP before switching to the Invidia. I am sure most of the power difference is a result of the bigger piping..not the divorced WG.

 

The odd thing is, there are a few dyno runs out there showing very little difference between a gutted DP and an aftermarket one. I for one, noticed a difference.

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I agree with rao.

Get the DP that fits your mood.

 

I for one got the Perrin 2-piece and boy the fitment was disasterous...

However, once put on and ready to go, it worked like a charm to me.

 

And this is nothing you have questioned about but gutted pipes will give you louder exhaust note and funky smell that you have to get use to.

I like both but staying catted for now.

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Spec B, Yeah your one of the lucky ones. Its just a small batch that had this issue with the invidia divorce holding the waste gate down with the divorce. It took me 1 month and a half to figure it out and once I did i was relieved. All i know is when i get one for my 5mt i will be grinding down the divorce just to be safe and not have to go back and forth removing it and reinstalling it.

 

I like perrin stuff but the thought of doing a 2 piece dp is just not my cup of tea. I like to eliminate all possible problems for example having to make sure the 2 piece dp doesn't have a leak is not what i want to be concerned with.

 

Fireb - did it lower the exhaust tone btw having the two cats? What numbers did you put down with what mods?

2008 6mt Legacy Gt Spec B DGM - Not so Stock/Work in progress

2006 5mt Legacy Gt OBP - Sold

2005 5eat Legacy Gt OBP - RIP

 

R.I.P Coxx

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i recently purchased the invidia catted dp and yet to install it. i was told that the first versions had issues needing to be grinded a little but the new ones being sold now will not have that issue. i will be installing my dp soon. the quality of the product appears good compared to other downpipes i have seen on the market.
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The avo dp looks like a quality product plus you can change the turbo -> dp connection

http://www.avoturboworld.com/avoshop/index.php?cPath=1_58_3_8&osCsid=c0f9c117ad748e3cd077e5071afbaee8

So if you wanted a dp to work with your twin scroll setup if that was your direction than you could. However the avo dp compared to the invidia dp is very expensive.

 

Interesting; I doubt that would be relevant to me, but the linked stuff looks quite a bit different than the "same" pipe on RalliTek's site:

 

http://www.rallitek.com/avohidopiwca.html

 

Sounds like Invidia's the way to go, as I'm not looking to spend more than is necessary...

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It doesn't seem to be working anymore :lol: BTW, it still doesn't matter :)

 

I tried :). Even though it doesn't matter, I still have to pick something! Besides, this bout of OCD may have saved enough to pay for the coating.

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Interesting; I doubt that would be relevant to me, but the linked stuff looks quite a bit different than the "same" pipe on RalliTek's site:

 

http://www.rallitek.com/avohidopiwca.html

 

Sounds like Invidia's the way to go, as I'm not looking to spend more than is necessary...

 

Nope that is the same pipe. The thing with the link i sent you is that you can change that top joint to meet your requirements. However again it won't really be necessary for most people since most don't care about using twinscroll turbo's etc.

 

Again i am just giving you info on the products you mentioned. I recommend the invidia since i have used it and had great results.

2008 6mt Legacy Gt Spec B DGM - Not so Stock/Work in progress

2006 5mt Legacy Gt OBP - Sold

2005 5eat Legacy Gt OBP - RIP

 

R.I.P Coxx

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Take a pic of the bellmouth before you install it, I'd like to see the different between the "new" and "old" Invidias.

 

I actually took pics of mine (specifically the bellmouth and divider)...I will dig them up and post them.

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Spec B, Yeah your one of the lucky ones. Its just a small batch that had this issue with the invidia divorce holding the waste gate down with the divorce. It took me 1 month and a half to figure it out and once I did i was relieved. All i know is when i get one for my 5mt i will be grinding down the divorce just to be safe and not have to go back and forth removing it and reinstalling it.

 

I like perrin stuff but the thought of doing a 2 piece dp is just not my cup of tea. I like to eliminate all possible problems for example having to make sure the 2 piece dp doesn't have a leak is not what i want to be concerned with.

 

Fireb - did it lower the exhaust tone btw having the two cats? What numbers did you put down with what mods?

 

Pm'ed Ya ;)

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