[VR Baron]

Originally Posted by 1LEornothing

Gas chamber cant pass Cali emissions, I think they may soon require Californians to install catalytic converters in their rectums so that they themselves as humans are emission compliant...

Haha, wouldn’t be surprised ��. My fifth gen I traded for my new car passes smog with shorty headers, tune and stage one cam. But as it will get only worse out here I am glad I have a new, stock car that is just as fast and a far better car and don’t have to worry about it
As to headers,a friend had a 2015 z28 that has the tri-y stock headers. He got 13 ho with headers, however a tune added a lot more, about 25 more. Our cars with the better efficiency and the computers controlling the parameters won’t make the gains from certain mods

[LT1ornothing]

Originally Posted by DaveC113

IMO, there's a lot of pointless mods going on these days that are only snake oil, for example catch cans for otherwise stock motors.

Today's cars are really good and many times it's difficult to improve on them.

2" primary headers for our cars are just stupid and you lose power due to decreased exhaust gas velocity and therefore decreased scavenging effect. I've used the same simulation software to design manifolds that the pros use... The only reason to use such headers would be for a totally built non-street use motor making a lot more power at higher rpms vs stock.

Strong supporter of the factory manifolds as well, but the 2" longtubes have their place on the street as well as the track. A full bolt on heads and cam LT1 benefits from the 2" longtubes, especially when complemented with a high ram intake manifold and a 103mm throttle body. Same goes for the mild to wild blower set ups. The 2" longtube headers here also show significant gains through the curve after turning over the factory manifolds. That being said, anything 500rwhp and under is cake for the factory manifolds, they are good pieces.

[DaveC113]

Originally Posted by 1LEornothing

Strong supporter of the factory manifolds as well, but the 2" longtubes have their place on the street as well as the track. A full bolt on heads and cam LT1 benefits from the 2" longtubes, especially when complemented with a high ram intake manifold and a 103mm throttle body. Same goes for the mild to wild blower set ups. The 2" longtube headers here also show significant gains through the curve after turning over the factory manifolds. That being said, anything 500rwhp and under is cake for the factory manifolds, they are good pieces.

I can't support the removal of cats, and the car will never pass emissions with long tube headers, so they shouldn't be used on the street.

Folks are going too far with mods, and while I think diesel trucks are to blame, EPA has now taken the position that uncertified mods are illegal even for race cars. Part of this blame certainly goes to those choosing to remove cats and run unreasonably loud exhaust systems on the street.

Things have gotten too ego-driven and loud, showy cars and trucks that openly flaunt the laws were bound to cause problems for the rest of us who are more concerned with performance. Coal-rollers deserve a special place in hell for what they have done.

tl/dr... removing cats for 10 hp is STUPID. If you do this you are part of the problem, and you shoulder some blame for the EPA's crackdown.

[LT1ornothing]

Originally Posted by DaveC113

I can't support the removal of cats, and the car will never pass emissions with long tube headers, so they shouldn't be used on the street.

Folks are going too far with mods, and while I think diesel trucks are to blame, EPA has now taken the position that uncertified mods are illegal even for race cars. Part of this blame certainly goes to those choosing to remove cats and run unreasonably loud exhaust systems on the street.

Things have gotten too ego-driven and loud, showy cars and trucks that openly flaunt the laws were bound to cause problems for the rest of us who are more concerned with performance. Coal-rollers deserve a special place in hell for what they have done.

tl/dr... removing cats for 10 hp is STUPID. If you do this you are part of the problem, and you shoulder some blame for the EPA's crackdown.

Sucks to hear man, no issues with emissions here down south though. I agree with your cat delete for 10 hp is dumb comment, but on some of these street blower builds, they rob much more power and can clog and cause engine damage. The cats also hurt the power on the heads and cam builds.i can understand your frustration though, I couldn't live somewhere that has emissions checks and tests.

[s346k]

cars on e85 without cats have been passing emissions for the last 20 years.

[6spdhyperblue]

Would be good if we could keep this on headers vs manifolds

Just sayin lol

[DaveC113]

The point is to respect other people. If your car or truck stinks or is extremely loud, you are not, and this is causing issues.

Should be common sense, but that seems to be in short supply these days...

[6spdhyperblue]

We’ve seen these posts on headers a few times but they’ve mostly all been 1-7/8” headers. I really wish op did 2” as his reports are pretty thorough especially now we’ll see what the car does going back to manifolds.

[L78toLT1]

I've been running around 750whp with standard Kooks high-flow cats for a couple of years now. Plenty of track days and spirited driving involved with no issues. With the right tune, cats will live at reasonable high power levels.
I agree with Dave that coal rollers and obnoxiously loud cars are not doing enthusiasts any favors. I don't think running catless on extremely high powered cars is terribly socially irresponsible though, provided the car isn't obnoxious in some other fashion. There just aren't enough of those cars around to make a measurable difference. One good house fire would probably dump more pollutants into the air than every catless 6th gen in existence

[NA18CamaroSS]

This thread certainly took an unexpected turn. I expected more pushback on my original premise. I did not anticipate a debate on the lack of social responsibility displayed by persons choosing to eliminate catalytic converters.
There may some headers that are more equal than others. Pray has said that in his testing the TSP headers flow the best. I never expected my two thousand dollar investment to lose power. I went with 1 7/8" headers because the plan is not to make a race car that revs to 8,000 RPM. Exhaust gas velocity is a thing, and you can go too big.
Others may choose a huge cam, a high ram, two inch headers and an open exhaust. My approach to modding this car has been baby steps. Then test. Test. Test. Verify. Analyze. I did not expect to gain 20 HP by installing headers and exhaust, but I really did not anticipate LOSING 16 HP. Some of the loss can be attributed to the false knock generated by the headers. However, even after the tune was corrected to compensate for the noise created by the headers and the engine was running the correct timing, the car was still down 7 HP.
Putting the stock exhaust manifolds and exhaust back on the car is a lot of work, but I really want to know the answer to my question. Now back to your regularly scheduled debate on the merits of the EPA and the future of fossil fuels.

[TheRealJA105]

Hey he said something about a catch can too and I just let that go

Just installed a dual catch can setup on my C6Z. I bought it with catted American Racing Headers already installed, but i think the LS7 manifolds and cats flowed pretty well too. (Still not as well as the LT1/LT4)

[6spdhyperblue]

I understand the theory and simulators pointing to 1-7/8 headers or smaller but there is an anomaly in this motor that isn’t accounted for in those models. Is it the relatively restrictive exhaust port, characteristic of the the pulse or something else, but it’s been said over and over and over that 2” headers pickup over 5hp over 1-7/8 everytime on at Bolton level. I can tell you for sure tsp 2” headers haven’t slowed down a single car I personally know of

[NA18CamaroSS]

There is a thread where Jannetty does some testing and the 1 7/8 headers are better up to about 6,000 RPM.:
https://www.camaro6.com/forums/showthread.php?t=472259
Which was interesting.

[enzia35]

Wonder if the time of year you tested had much to do with it.