Opinions please ! need some advice
Just an FYI..... Diablo Lew told me that either way would be ok. However deleting the converter on the LS4 would not buy me much. He said on the LS4 it is not that restrictive.
Lew will be doing the re-tune after the header install. I was messaging him today about getting the new ITune tuner and brought up the supject of the converter becuse I have read where he would have to tune out the code that will be thrown if the converter where deleted
Bottom line .... think I will keep my cat .... Meowow
Lew will be doing the re-tune after the header install. I was messaging him today about getting the new ITune tuner and brought up the supject of the converter becuse I have read where he would have to tune out the code that will be thrown if the converter where deleted
Bottom line .... think I will keep my cat .... Meowow
Just an FYI..... Diablo Lew told me that either way would be ok. However deleting the converter on the LS4 would not buy me much. He said on the LS4 it is not that restrictive.
Lew will be doing the re-tune after the header install. I was messaging him today about getting the new ITune tuner and brought up the supject of the converter becuse I have read where he would have to tune out the code that will be thrown if the converter where deleted
Bottom line .... think I will keep my cat .... Meowow
Lew will be doing the re-tune after the header install. I was messaging him today about getting the new ITune tuner and brought up the supject of the converter becuse I have read where he would have to tune out the code that will be thrown if the converter where deleted
Bottom line .... think I will keep my cat .... Meowow
Joined: Aug 2011
Posts: 38
The factory cat converter IS a modest restriction and I would upgrade it. I've run a 5" body Magnaflow spun metal converter, 51659 for the 3" in and out, which is twice the surface area of the typical "200 cell" spun converters.
Also, LS4ers are way too stubborn about dropping their single 2.5" exhaust, a 3" exhaust makes a difference if you're upgrading infront of the cat-back which you are. You can purchase a 3" cat-back without mufflers from ZZP; your exhaust shop would have to make minor mods to the Y pipe section to refit the Magnaflow mufflers but you could keep the mufflers from your current system, resell the piping to make some cash back.
You don't need a downpipe, your DT headers replace the restrictive OE downpipe, all you need is a cat and rear downpipe section to connect to the cat-back flange. ZZP should be able to sell you the tail end of the downpipe section in 3" with the flange, hanger and O2 bung to connect the headers to their cat-back if you go that route.
What do you have on the intake side of things?
Also, LS4ers are way too stubborn about dropping their single 2.5" exhaust, a 3" exhaust makes a difference if you're upgrading infront of the cat-back which you are. You can purchase a 3" cat-back without mufflers from ZZP; your exhaust shop would have to make minor mods to the Y pipe section to refit the Magnaflow mufflers but you could keep the mufflers from your current system, resell the piping to make some cash back.
You don't need a downpipe, your DT headers replace the restrictive OE downpipe, all you need is a cat and rear downpipe section to connect to the cat-back flange. ZZP should be able to sell you the tail end of the downpipe section in 3" with the flange, hanger and O2 bung to connect the headers to their cat-back if you go that route.
What do you have on the intake side of things?
Wish I would have known this. I Already have the Magnaflow Catback which I believe is a 2.5" exhaust. Your saying that the 3"" Catback exhaust on ZZP's site can go on the 06-07? And then I could simply use my current mufflers with minor modifications to fit them?
Wonder how hard the current piping would be to sell now.
Wonder how hard the current piping would be to sell now.
Last edited by Slugger088; Jan 16, 2014 at 09:03 AM.
Ya I have new Magna flows 2.5 " To pricey to change out now. I am using K&N for intake I ralize now CAI would have been a better choice
I guess that's what Will means when he says LS4 guys are too stubborn to switch it out to a 3"" exhaust. LOL. It's not that I am stubborn -- I would have went with 3'' piping from the very beginning if I knew the ZZP cat back fit this car and if I had known for sure this size was better if Headers were on the way.
It would be $400 for the ZZP piping without the mufflers. Then a custom job to attach the mufflers. All just to go up 0.5''.
You would need to add the 3"" Downpipe and the resonator if you wanted that as well. The total would be $600 something just for the new piping.
It would be $400 for the ZZP piping without the mufflers. Then a custom job to attach the mufflers. All just to go up 0.5''.
You would need to add the 3"" Downpipe and the resonator if you wanted that as well. The total would be $600 something just for the new piping.
Last edited by Slugger088; Jan 16, 2014 at 09:31 AM.
I guess that's what Will means when he says LS4 guys are too stubborn to switch it out to a 3"" exhaust. LOL. It's not that I am stubborn -- I would have went with 3'' piping from the very beginning if I knew the ZZP cat back fit this car and if I had known for sure this size was better if Headers were on the way.
It would be $400 for the ZZP piping without the mufflers. Then a custom job to attach the mufflers. All just to go up 0.5''.
You would need to add the 3"" Downpipe and the resonator if you wanted that as well. The total would be $600 something just for the new piping.
It would be $400 for the ZZP piping without the mufflers. Then a custom job to attach the mufflers. All just to go up 0.5''.
You would need to add the 3"" Downpipe and the resonator if you wanted that as well. The total would be $600 something just for the new piping.
exspecially after spending $635 on headers and $300 to put them in
Joined: Aug 2011
Posts: 38
Yes exactly lol amazing the amount of LS4 owners that have a K&N intake and a Magnaflow exhaust, those exact modifications.
2.5" to 3" doesn't sound like much but I posted this on an Impala forum a few weeks ago:
Lots of discussion if you google on exhaust size versus horsepower. David Vizard has some exhaust math using 2.2cfm per horsepower, which when you punch it out states that 300 horsepower should be running a 3" single exhaust. Magnaflow themselves state a 2.5" single supports a maximum recommended 350 flywheel. So the stock LS4 is right in the middle of that crossover point and by the time you have basic mods and sit at 280 wheel horsepower or just below, you have your 350 flywheel horsepower.
The ZZP 3" exhaust for the 2004+ Grand Prix will fit a 7th gen Monte and have the hangers in the right place, minus the mufflers. ZZP uses centre in and out mufflers, versus the traditional offset in, I don't know why, but that's the source of needing some minor mods to fit the mufflers, or get center and center out mufflers plus your choice of tips.
2.5" to 3" doesn't sound like much but I posted this on an Impala forum a few weeks ago:
If you do the math of the area of a circle (cause exhaust piping is, you know, circular), here are some numbers to consider:
4.9" = Single 2.5" pipe
5.5" = Dual 1-7/8" pipe
7.1" = Single 3" pipe
7.95" = Dual 2.25" pipe
9.6" = Single 3.5" pipe
9.8" = Dual 2.5" pipe
So, looking at the above, a few things to consider:
#1 - The factory dual 1-7/8" split doesn't choke the single 2.5" pipe that feeds it
#2 - A single 3" pipe doesn't have the same air volume capacity as a dual 2.25" pipe setup (also consider how popular a dual 2.25" exhaust is on say even a B-Body LT1 Impala aftermarket exhaust)
#3 - Increasing from 2.5" to 3" single exhaust piping may not sound like much, but its actually an increase of 45% in surface area.
4.9" = Single 2.5" pipe
5.5" = Dual 1-7/8" pipe
7.1" = Single 3" pipe
7.95" = Dual 2.25" pipe
9.6" = Single 3.5" pipe
9.8" = Dual 2.5" pipe
So, looking at the above, a few things to consider:
#1 - The factory dual 1-7/8" split doesn't choke the single 2.5" pipe that feeds it
#2 - A single 3" pipe doesn't have the same air volume capacity as a dual 2.25" pipe setup (also consider how popular a dual 2.25" exhaust is on say even a B-Body LT1 Impala aftermarket exhaust)
#3 - Increasing from 2.5" to 3" single exhaust piping may not sound like much, but its actually an increase of 45% in surface area.
The ZZP 3" exhaust for the 2004+ Grand Prix will fit a 7th gen Monte and have the hangers in the right place, minus the mufflers. ZZP uses centre in and out mufflers, versus the traditional offset in, I don't know why, but that's the source of needing some minor mods to fit the mufflers, or get center and center out mufflers plus your choice of tips.
