Headers and x-pipe question
Thread Starter
Drifting
Joined: Jan 2009
Posts: 1,503
Likes: 1
From: Tennessee
Headers and x-pipe question
Okay guys. I have done a lot of reading but I have a question. I had a rather lengthy discussion with a tuner today. I have purchased some kooks 1 7/8 headers and cross pipe without cats for my 2009 Z-51 coupe. I do not need the cats where I live. The tuner told me that I will probably lose hp and torque installing the headers and cross pipe and that I would have been better off with the cats for back pressure on the exhaust. Is this guy correct? I plan on installing the headers, the v max spiral ported throttle body, low profile electric cut outs and I already have a varram intake. I plan to have the car tuned after the install. This guys opinion about loss of hp and tq when installing the headers in contrary to everything I read. I would appreciate your experienced input here. Especially on the cats.... Btw I plan to keep the NPP exhaust. I cannot afford a new borla at this time. Thanks for your opinions and experience in advance.
Safety Car
Joined: Sep 2007
Posts: 4,359
Likes: 6
From: Los Alamitos California
St. Jude Donor '09
Okay guys. I have done a lot of reading but I have a question. I had a rather lengthy discussion with a tuner today. I have purchased some kooks 1 7/8 headers and cross pipe without cats for my 2009 Z-51 coupe. I do not need the cats where I live. The tuner told me that I will probably lose hp and torque installing the headers and cross pipe and that I would have been better off with the cats for back pressure on the exhaust. Is this guy correct? I plan on installing the headers, the v max spiral ported throttle body, low profile electric cut outs and I already have a varram intake. I plan to have the car tuned after the install. This guys opinion about loss of hp and tq when installing the headers in contrary to everything I read. I would appreciate your experienced input here. Especially on the cats.... Btw I plan to keep the NPP exhaust. I cannot afford a new borla at this time. Thanks for your opinions and experience in advance.
The cutouts won't net you much if any power and will add some weight, but it's your car.
San
Burning Brakes
Joined: Oct 2006
Posts: 995
Likes: 2
From: Virginia Beach VA
Somewhat dubious input from tuner, but...
General wisdom is 1-3/4 is all you need for 99% of LS2/3 motors, but realistically it's not a great deal of diff. for your basic street car. No cats, combined w/ 1-7/8 theoretically could pull the torque down thus your 0-60 will have neg. effect. Torque is what gets you outta the hole. Lotsa opinions on cats, IMHO, unless you're building a race car, all pain, little gain. At WOT, he's just plain wrong on the loss of HP. Finally, I would highly rec. leaving the NPPs & adding A M2W controller, don't waste time effort, & money w/ cutouts when your essentially accomplishing the same thing w/ NPPs. If you go LTs, w/ no cats, you're gonna have a loud car & your gonna want the ability to tone it down, kill the drone, carry on a convo, avoid added LEO attention, etc. There's enuf debate on 1-7/8 & cats to sick a battleship, but when the smart guys chime in 1-3/4 best, keep cats, & personally w/ NPPs in place your blowin' a lot of money gaining virtually no hp. Spend it on a ported FAST 102, & prlly have a grand left to do as you like.
Last edited by Mike V.; Aug 21, 2011 at 01:22 AM.
Race Director
Joined: Aug 2011
Posts: 10,779
Likes: 491
From: Shits Creek NY
no cats
1st, Id say that I agree with oldmansan in looking for another tuner. Additionally, I never heard of losing power by keeping cats - just the other way around. My last Vette was an 03 Z06 with kooks headers into straight pipes right into a Corsa catback (no cats). The car was very loud in an abnoxious manner (plenty of attitude). It didnt bother me much because it was just a toy that I'd show and take out on the weekends. I will say, I could imagine the loudness could become old quickly depending on how you use your car so I would also have to agree with Mike V on his feelings about the noise. Hope this helps...
Former Vendor
Joined: Feb 2007
Posts: 2,572
Likes: 1
From: Austin Texas
Yes, you need cats where you live....it is a Federal Law. There is no torque loss going to 1 7/8" over the 1 3/4". No need to use 1 3/4" anymore and the Kooks 1 7/8" are very nice and well designed.
Thread Starter
Drifting
Joined: Jan 2009
Posts: 1,503
Likes: 1
From: Tennessee
General wisdom is 1-3/4 is all you need for 99% of LS2/3 motors, but realistically it's not a great deal of diff. for your basic street car. No cats, combined w/ 1-7/8 theoretically could pull the torque down thus your 0-60 will have neg. effect. Torque is what gets you outta the hole. Lotsa opinions on cats, IMHO, unless you're building a race car, all pain, little gain. At WOT, he's just plain wrong on the loss of HP. Finally, I would highly rec. leaving the NPPs & adding A M2W controller, don't waste time effort, & money w/ cutouts when your essentially accomplishing the same thing w/ NPPs. If you go LTs, w/ no cats, you're gonna have a loud car & your gonna want the ability to tone it down, kill the drone, carry on a convo, avoid added LEO attention, etc. There's enuf debate on 1-7/8 & cats to sick a battleship, but when the smart guys chime in 1-3/4 best, keep cats, & personally w/ NPPs in place your blowin' a lot of money gaining virtually no hp. Spend it on a ported FAST 102, & prlly have a grand left to do as you like.
First of all thank you guys for taking the time to offer me your input. Second of all this brings another question to mind.
I already have the M2W installed. If I skip the cut outs as you have recommended and go ahead and add the fast 102 intake what type of gain might I expect in the hp and tq area?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Drifting
Joined: Jan 2009
Posts: 1,503
Likes: 1
From: Tennessee
I already have the x-pipe without cats sitting in the garage. It's gonna be a pita to send them back and swap them out. I guess I should have ordered with the high flow cats....? I have no inspection required here. The question of legality of running this set up aside I am more concerned at this point about hp and tq. Is it going to be worth the trouble to swap them out? If the vendor will even let me....
Thanks again guys...
Thanks again guys...
Former Vendor
Joined: Feb 2007
Posts: 2,572
Likes: 1
From: Austin Texas
I like the cats installed since they really clean up the exhaust gasses. No cats tend to have a rich smelling exhaust and with the high flow cats, they do not restrict the exhaust flow very much. The Kooks 1 7/8" Headers have shown 25 rwhp with no tune. Of course, there is a little more if you have it tuned. Spend a little extra time rotating the X-Pipe to keep the tips level. The headers just slide up in from the bottom with no issues with fitment. Kooks sends exhaust gaskets and I use the GM MLS Gaskets.
Race Director
Joined: Aug 2011
Posts: 10,779
Likes: 491
From: Shits Creek NY
I already have the x-pipe without cats sitting in the garage. It's gonna be a pita to send them back and swap them out. I guess I should have ordered with the high flow cats....? I have no inspection required here. The question of legality of running this set up aside I am more concerned at this point about hp and tq. Is it going to be worth the trouble to swap them out? If the vendor will even let me....
Thanks again guys...
Thanks again guys...
Race Director
Joined: Mar 2007
Posts: 11,331
Likes: 18
From: Missouri City Texas
I'd keep the catless setup. I much prefer the tone, volume, price and not having any power loss with a catless setup.
However, if you have very strict inspections you may reconsider. If they just scan for codes you'll be fine. Or just fine a "friendly" inspection place.
Also, your tuner is a fool...find a new one.
However, if you have very strict inspections you may reconsider. If they just scan for codes you'll be fine. Or just fine a "friendly" inspection place.
Also, your tuner is a fool...find a new one.
Race Director
Joined: Mar 2007
Posts: 11,331
Likes: 18
From: Missouri City Texas
I'm pretty sure none of us care about that, including you, since you're recommending Kooks longtubes.
Former Vendor
Joined: Feb 2007
Posts: 2,572
Likes: 1
From: Austin Texas
Well, you are right about that. I have friends of mine in the ATX that were pulled over and the officer looked for cats. They were issued citations for improper equipment for not having cats. Most don't care about the longtubes. It depends on how picky law enforcement wants to be. They were pulled over for excessive noise and exhaust fumes. That lead the officer to inspect the car for violations.
Thread Starter
Drifting
Joined: Jan 2009
Posts: 1,503
Likes: 1
From: Tennessee
Well after a ton of reading and trying to find another tuner I went ahead and sent the cat lees x-pipe back today and got the one with cats. I plan to skip the cut outs and keep the NPP. I hope to be able to find a really good deal on a fast intake or maybe a z06 intake. I hope I can find a good tuner close by. I think the closest forum shop is vengeance racing and that is still a good ways away. Wish me luck. I will let you guys know how it goes.
Thanks for all your opinions and good information.
Thanks for all your opinions and good information.