Just got my zzp downpipe.Do I need this???

TDCRacing · 03-05-2008

ok well i just got my zzp down pipe in and am kind of dissapointed in the size of the exhaust pipe.i got the 2.5'' offroad pipe w/ no cat and u-bend delete.come to find out the actual u-bend o.d. is the same as the new zzp down pipe!! so should i return it and get the 3'' off road down pipe?? i dont plan on doing any more exhaust work other than a plog from zzp for the front.I just dont see me getting any performance gains from this.other than not havig a cat i imagine the flow will be about the same.yes the ubend does disrupt flow a little but again it is the same size pipe.what is your take on this?? has anybody gotten the 2.5 before and noticed a difference in performance?? just need some advice.thanks in advance

**Bio248** · 03-05-2008

should have just got the 3". the 2.5" will suffice if you have a gt.

TDCRacing · 03-05-2008

the rest of the exhaust is 2 or 2.5'' (stock) how would the 3 inch down pipe help me if im not planning on upgrading any of the exhaust execpt to do a plog? just a question.it is a gtp by the way.

TDCRacing · 03-05-2008

just found this when i was browsing online...made 400 whp with a turbo with a 2.5 inch dp on an 04 gtp....so should i return this thing or what???

***************The exhaust side is finished off with a custom stainless steel crossover assembly, specific mandrel bent, TIG-welded, 2.5-inch stainless steel downpipe with a U-bend removal and a CarSound high-flow catalytic converter. Happily, the outlet bolts directly to the stock exhaust system or Borla, DynoMax , or SLP systems to greatly simplify installation.

**Coogles** · 03-05-2008

The 2.5" will be fine. With guys trapping 115 on S&S headers running a 2.5" downpipe, what in the world does anyone need a 3" downpipe coming off of stock manifolds for? 2.5" is plenty large to support the power levels it sounds like you're wanting to achieve. Plus, if you're still running a stock cat-back there's absolutely NO reason to even think about going bigger than 2.5". The 3" section before a small 2.25" cat-back would KILL exhaust gas velocity and create a huge area of high pressure in the downpipe.

TDCRacing · 03-05-2008

thanks but i'm just going to do from the downpipe to the plog.nothing else with exhaust.so is it worth doing the 3inch dp if im not going to match it up the rest of the way with 3inch exhaust??? anybody else???

TDCRacing · 03-05-2008

Originally Posted by Coogles

The 2.5" will be fine. With guys trapping 115 on S&S headers running a 2.5" downpipe, what in the world does anyone need a 3" downpipe coming off of stock manifolds for? 2.5" is plenty large to support the power levels it sounds like you're wanting to achieve. Plus, if you're still running a stock cat-back there's absolutely NO reason to even think about going bigger than 2.5". The 3" section before a small 2.25" cat-back would KILL exhaust gas velocity and create a huge area of high pressure in the downpipe.

thanks i was kind of thinking the same...but do you think it would be worth the money to basicly just have the cat and the ubend removed(pretty much what the out come is going to be)?? any power gains cuz if not im going to return it.... anybody else feel the same???? got the car up and cooling off so let me know!!! thanks!!!

TDCRacing · 03-05-2008

Originally Posted by IndeedSS

If you look into the opening of the stock DP, you will understand why the ZZP DP is less restrictive. Also with the ZZP DP you don't need a ubend delete. The 2.5 DP is plenty for a NA.

***************its not n/a its a gtp!!!! sorry!!!*******************

TDCRacing · 03-05-2008

let me clarify....

basicly since the exhaust tube sizes are the same between the stock exhaust and the zzp downpipe the only real difference is that i will no longer have a cat or u-bend...is that worth the reduced level of kr(if any) / the increased hp and or tq and the money spent for these inprovements??

**Toasty** · 03-05-2008

Originally Posted by TDCRacing

let me clarify....

basicly since the exhaust tube sizes are the same between the stock exhaust and the zzp downpipe the only real difference is that i will no longer have a cat or u-bend...is that worth the reduced level of kr(if any) / the increased hp and or tq and the money spent for these inprovements??

the stock DP is still more restrictive than the zzp... use what you bought, you wont regret it.

**IndeedSS** · 03-05-2008

Originally Posted by TDCRacing

***************its not n/a its a gtp!!!! sorry!!!*******************

sorry man I deleted that post right after I made it. I guess you were faster at the quoting than I was at deleting.

and I agree with Toasty

TDCRacing · 03-05-2008

yea when i posted it i was like wtf?...then i said oh he must have realized it was a gtp i was talking about...lol but it's cool...i appreciate the reply's guys and im glad u all convienced me not to return it(or just made me realize what was best)..i hate going through the hassell of returning crap to where i bought it lol...im going to put it on now so i hope i can maybe tell somewhat of a difference...we will see

**Going Too Phast** · 03-05-2008

I'll refrain from ranting on this, but it is ridiculous how much 3" DPs are pushed onto people. I've got a 2.5" DP on my GTP and I got that on purpose. By the time a 2.5" is going to hold you back, you are in header territory. I personally think a 3" DP is useless. The stock exhaust is routed pretty bad anyway, the DP band aid can only do so much. 2.5" will help you keep low rpm part throttle response, and won't make any appreciable difference at higher RPMs. The 2.5" DP is also cheaper and you don't have to worry about flipping your sway bar. And I am not the only one who feels a 2.5" is just fine for a GTP. From Overkill's website:

"Which size is right for my vehicle?

We recommend 2 1/2" downpipes for most vehicles. If you have a GT, you'll retain your torque better. On any vehicle however, supercharged included, that is keeping the less restrictive factory cat-back exhaust or has a 2 1/2" aftermarket system, the 2 1/2" will compliment its flow better...A 2 1/2" downpipe with Powerlog will support bolt-on vehicles idealy." Emphasis added.

When comparing a stock DP with an aftermarket, you also need to keep in mind that the stock is double walled and has barely a 2" ID. So yeah, feel good about keeping it.

TDCRacing · 03-05-2008

WOW!!!

So i went and installed like i said...

I had presoaked everything in pb blaster stuff and man i must of made about 80 1 inch turns on each of the two bolts that connected to the rear header lol....Damn tight spaces!!....so anyway i popped it out and put the new one on and started it up...let it sit for a second and heat up the exhaust so it could bond the gaskets to the mating surfaces(just in case to help prevent a blow out in the gasket)....

So anyway im driving and i decide to get on it from a stop and i noticed right away it spun the tires a little longer than normal....then i got on it from about a 30mph roll and was on it while going about 80...i was recalling what it felt like (pulling wise) to when it was suppose to shift into second and im like....ok its about to shift...look down and its only at 4500rpm's...

so in other words it was pulling like it was at 5500 before the dp install...but now it starts pulling the same at like 4500-5500.

conclusion: Money well spent!!! noticeable gains!!!

But yea now that i think about it it is pointless to have the 3''dp if you are leaving the rest at 2/ 1/2''....but just wanted to check with my buddies first lol...and by the way with o2 sensor unplugged no ses light has come on yet...drove for about 30 mins...o well even if it does my tuner will be here monday so ..problem solved!!!

later fellas