|
|
12-22-2011
I was wanting to get a down pipe for my 01 GT off zzp and I was wondering which one I should get? There are 16 models and don't know which will work best with my K&N air filter and i'm going to get a overkill computer. What do you guys/girls suggest? Thanks!
ZZPerformance - ZZP Downpipes #
12-22-2011
Maybe consider headers? but if you dont want headers then you can do a 3in catted or catless downpipe.Good performance and good for flow.
12-22-2011
3".
no, headers are not too much for a N/A car as long as they're 1 and 5/8ths primaries.
And yes, Speed daddy's/SSAC's are 1 and 5/8ths.
12-22-2011
Link in signature for one...
For another...if you don't care about emissions or rust...get the cheapo bolt on 3" DP.
12-22-2011
I'm not going to do a top swap so I don't need a 3in downpipe and I want a bolt in downpipe. I dont care about emissions.
12-22-2011
Nope quite literally a 2.5" is a waste.
3" or headers.
12-22-2011
Ok thanks. Should i get it with or with out a cat. I'm getting a overkill PCM so I will be setup to run with out a cat.
12-22-2011
Sorry but for NA I still say a 2.5" down pipe is plenty. Even on my DOHC which moved much more air then NA l36's the stock 2.5" dp on it was plenty for it. That engine went to 7000 rpm at the track and high 6k daily driving. Not to mention its four valve heads would way out flow the 3800 heads. I knew of a guy with a DOHC that tried a 3" dp on his and he lost a bunch on he butt dyno and his 60' suffered.
Being NA u really need to keep from going to big on the exhaust and loosing what some call "back pressure". What your really trying to do is maximize exhaust scavenging. This is where each progressive exhaust pulse pulls the next from the vacuum the last pulse left behind. My l36 has speed daddy headers. When I did the swap I started with headers so I have never felt it with stock manifolds. But it deff pulls nice. I feel if I was gonna build an all NA l36 I would take a set of speed daddy's and when replacing the flex. I would go with 2.5" or slowly step down to 2.75" and then 2.5". Also my current cat back sonds and flows great so that too would stay part of the system if I were to build an all NA system.
But from what u are saying it sounds like u want a dp and not headers. Honestly I feel a front ported manifold or plog is more important.
12-22-2011
back pressure helping is a myth. you want to maintain VELOCITY. a 3" downpipe does not destroy velocity and a 2.5" is ALWAYS too small.
12-22-2011
Honestly i felt more low end gain when i did my 3in downpipe.How? i have no idea but like i said its good for performance just as much as flow.Before i did that i did have 2.5in straight pipe but it wasnt quite enough.
12-22-2011
I would like to buy headers but they are a little spendy for me.
Last edited by Pontiac Man; 12-23-2011 at 12:31 AM.
12-23-2011
pfyc made a dp built like a freakin tank. preey sure they dont anymore but maybe you can find a used one
12-25-2011
I have a 2.5" on my N/A car and it is more than fine. I don't think it would make a difference with a 3" vs a 2.5". The U bend is the real problem area. It is such a minor modification that you really shouldn't be able to tell at all. I didn't even really notice the gains from the downpipe until it was paired with a HV3.
12-26-2011
from what im seeing the people that are saying the 3" was better have rockers. my DOHC didnt have the option of increasing the flow via rockers or cams so a 2.5 was fine and my guess now is if your staying with the stock l36 valve train, that the 2.5" is the way to go. if your going to swap to diff valves or a cam a 3" might benifit you.
12-26-2011
200 bucks is too spendy? Hell most catted downpipes will cost you that with shipping.Originally Posted by Pontiac Man
12-26-2011
i got my SD headers shipped for about 180! but then again you need to modify them if you dont want issues... i havent modified mine yet. and am contemplating it when i tear it all down for the topswap.... prob have the flex moved and down pipe shortened so the goose neck is not as low.
12-26-2011
valves won't help you much in improving the exhaust velocity and flow in a n/a application.
look at abbot racing heads.
GM3800V6
Abbott Racing "Big Valve" Cylinder Heads
A common misconception is the exhaust needs to be ported as much or more than the intake. Research on our own IHRA Top Sportsman BBC engine plus other engine combinations has proven that a smaller exhaust port will make more power and will make the engine rev gain quicker than a large port, even on engines with superchargers and nitrous. A key to quick acceleration in the car, whether it is on the drag strip or the autocross track, is a quick accelerating engine. The smaller exhaust ports keep the velocity of the air high enough to let the motor accelerate as quickly as possible. An exhaust port too large leaves the engine sort of "out of breath" at the upper portion of the exhaust stroke in the engine. You may ask, why not keep a smaller intake port too? The reason the intake needs to be larger is because that is where the air and fuel enters the engine. It needs to flow as much as possible to get as much air and fuel into the combustion chamber to make a more powerful explosion. The difference between a set of heads working on naturally aspirated engine and engines with power adders is in the camshaft. Nitrous engines will run a little more exhaust duration. Engines equipped with turbochargers and superchargers will need the smaller exhaust port, less exhaust duration on the cam, and a wider lobe separation to keep the velocity up in the exhaust tract. The reason a wider lobe separation and less exhaust duration is used on high boost forced induction applications is because the exhaust is pushed out of the combustion chamber by the boost of the turbo or supercharger. If the lobe separation is too close, there is too much overlap of the intake and exhaust valves being open and some of the new and unused air/fuel charge is pushed out of the chamber into the exhaust.
UPDATE: R&D on the big valve cylinder heads is complete and we have come to the conclusion that the larger intake valve is not beneficial. We tested with valve sizes ranging from 1.86"-1.88" and the amount of air moved through the ports changed very minutely and lowered the efficiency of the heads. The smaller 1.84" valve should be the best candidate for the best power and best accelerating engines.
12-27-2011
AR is legit.
I plan on going to them this time around for head work when I grenade the silver car for the first time with boost. Don't worry, it'll happen. They really tend to know their stuff the more I read about them, especially on the 3800 FBody stuff.
| « Previous Thread | Next Thread » |
| Tags for this Thread |
| Bookmarks |
Bookmarks |
