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Gains from 3" downpipe on a stock GTP... opinions?

Elite6

Elite6

New member
Snagged a 3" DP from ZZP during the black friday sale. Car will be basically stock except for intake and ZZP wires. What can I expect and is this mod worthwhile on essentially a stocker? Don't think I wanna go through the bs that seems to come with installing headers.
 


Gain is minimal in my opinion. Its more about freeing up flow for future mods. I only got my ZZP DP because my stocker came apart at the flex.
 
The affects you feel are minimal, if catless you get a good sounding exhaust. But it is an essential mod on these cars if you haven't gone with headers.
 
I wouldn't advise dropping pulley if that's where this is going.

Basically your car won't pull as much timing, You might see 5-10whp depending how badly your car was knocking before.
 


no looking at a pulley drop right now, wasn't even sure if DP and Plog could warrant a drop? I was thinking the DP for now and look at tuning next before anything else.
 
You won't really *need* a tune after a 3" DP as the car will automatically not knock as much as it does stock (3-6* KR), thus providing you with more usable timing (and HP) by removing some of the stock restriction. Personally i think you'd do better getting headers as they not only remove the awful front manifold and crossover on these cars but also serve to remove the u-bend the same as a 3" DP would with the added benefit of futureproofing yourself for further mods.
 
My car still had a good amount of KR when I went to a catted 3'' dp.
I wasn't able to run KR free on the stock pulley with stock timing/AFR (AFR which is actually quite rich) until I got headers.

Once I got headers I was able to lean out the AFR almost a full point and run an 04+ timing table.



As someone else said you'll be lucky to see 5-10whp.
 
Minimal gains, shouldnt need a tune too bad. I would pick up another easy mod like rockers and then worry about tune.
 
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