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Modding the Supercharged 3800 for Dummies


digitaloutsider
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On 4/18/2017 at 7:52 PM, digitaloutsider said:

ZZP bolt-in downpipe. If you're keeping the stock catback (which is generally good to 300 WHP), select the 3" DP and 2.5" flange exit.  If you're having an exhaust shop weld up a full 3" exhaust, select the 3" DP with 3" exit or exit flange depending on how you want it.  Do not buy the 2.5" downpipe for a supercharged application.  It's up to you whether or not you want to buy a catted version, but be aware that not having a cat will trigger a check engine lamp.  The ZZP downpipe can be used standalone or mated to a..

Thanks for the excellent write up for a newbie to this.

For the sake of understanding, what is wrong with the 2.5" downpipe if very mild mods (front plog, pcm, 3.6 pulley, intake) are planed after all maintenance is completed? Does the crossover that's before the downpipe have an inside diameter over 2.5"?

Attempting to keep exhaust quieter with as little drone as possible (stock after dp)

Appreciate any knowledge/guidance for due dillagence.

 

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21 minutes ago, loumatt said:

Thanks for the excellent write up for a newbie to this.

For the sake of understanding, what is wrong with the 2.5" downpipe if very mild mods (front plog, pcm, 3.6 pulley, intake) are planed after all maintenance is completed? Does the crossover that's before the downpipe have an inside diameter over 2.5"?

Attempting to keep exhaust quieter with as little drone as possible (stock after dp)

Appreciate any knowledge/guidance for due dillagence.

 

Anytime you drop a pulley on a l67 check the KR. The goal is to get the lowest KR as possible. I'm currently running a 3.5 inch pulley, 2.5 inch zzp DP (deletes the u-bend) which is very restrictive. You can just delete the u-bend in the exhaust. 

I still have stock headers ( I really want to get a Plog on my car). I have a CAI, tune, colder spark plugs (autolite 104), new wires, TB spacer, 180 Tstat and I'm running 93 octane. I get maybe 1* of KR while accelerating sometimes but at WOT my scan tool always read 0* KR. 

I would suggest before you mod your car get a baseline of what the KR is. Before I dropped the pulley size I checked my car first. A 3.6 pulley isn't that drastic of a drop, and you can probably run it with minimal mods. 

Link to a zzp u-bend delete. 

https://zzperformance.com/products/ubend-delete

Edited by 94 olds vert
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Thanks for the response 94.

ZZP reviews have a handful of buyers who have used the 2.5 pipe for the L67...maybe you are one of them.

I have asked them and the response was the 2.5 would be somewhat quieter and an upgrade over a ubend delete.

From my very limited understanding on exhaust dropping down isn't as bad as going down then up, that is the reason for the question on the i.d. of the cross pipe.

How did your d.p. installation affect sound?

I will heed the warnings of the KR issue. The last thing I want to do is cause a catastrophic issue. Digital outsider's advice on maintenance before going fast seemed to make sense.

A lot to learn on the KR and tuning for me. Glad to have found a resource that understands the specifics of the 3800.

Just looking for a better running GS and if I can pull better performance and mpg out of it at the same time, why not?

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I would do the maintenance stuff first, scan, then colder plugs, downpipe, scan again before dropping pulley size.  The, if you can, convert to E85 and you can run a smaller pulley.   

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The DP I think didn't have too much effect on my exhaust. I already had magnaflow mufflers on my car, and the DP made the exhaust sound a bit different, but I don't think it made the exhaust louder. 

 

Edited by 94 olds vert
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2 minutes ago, pwmin said:

I would do the maintenance stuff first, scan, then colder plugs, downpipe, scan again before dropping pulley size.  The, if you can, convert to E85 and you can run a smaller pulley.   

I've been thinking about switching over to E85 on my GTP. It costs less per gallon. I don't drive my car much didn't even put 500 miles on it last year. 93 is still around $5 a gallon. 

If I did switch it over to e85 I could drop my pulley size down. 

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The downpipes don't make them louder, IME.  I even changed out the resonator for a smaller one and it didn't change the sound at all.

It's not quite a miracle drug, but it's close.  Allows me to run a 3.2 on a top swap.  Converting is really easy.  It's better to tune for it, IMO, but you can just switch to 42.5's, get rid of the gasoline, put E in it and you're good to go, maybe a filter change pretty quickly.

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3 minutes ago, pwmin said:

The downpipes don't make them louder, IME.  I even changed out the resonator for a smaller one and it didn't change the sound at all.

It's not quite a miracle drug, but it's close.  Allows me to run a 3.2 on a top swap.  Converting is really easy.  It's better to tune for it, IMO, but you can just switch to 42.5's, get rid of the gasoline, put E in it and you're good to go, maybe a filter change pretty quickly.

I wonder if I get away with not tuning for it. I have a ZZP 1.0 PCM. I've heard that fuel filter will need to be changed out. 

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2 minutes ago, 94 olds vert said:

I wonder if I get away with not tuning for it. I have a ZZP 1.0 PCM. I've heard that fuel filter will need to be changed out. 

I tuned for mine since I was in the middle of tuning, anyway.  I've never done it without tuning, but tons of people swear by it.

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