Well I had some midlength mac headers with an orp and a cutout on my car and i just installed some flowtech longtube headers. Im planning on trying out the car with open headers since i dont have a y-pipe or anything right now for them. Will open headers slow me down or help me out. Ive heard it will slow me down cuz i wont get enough back pressure from several people, but the again several people have told me it will help me out becuase of my stroker motor.
I have a MTI 383 stroker, MTI stage 2 heads, MTI r1 cam, all boltons, have run 11.1s with the macs.
To your alls experiences, would open headers slow me down or help me out, thanks.

 

Don't think your front O2s are going to read an accurate A/F ratio with open headers.

 

Explain what you mean by this.

 

the 02's need an honest reading of air and fuel misture from your motor. When there is outside air close like in your situation, the outside air will combin with the exhaust and create a bad reading, most likely it will say your car is running lean, when in reality, its just sensing your exhaust AND the outside air. In all, you will run rich, and pop. Its accually pretty funny. Ive never seen an LS1 run good with open headers. Dont let you motor get too hot IMO, no back pressure will be a big problem on a hot motor. Ive ran mine around the block with open mids before and it didnt do much, just poped lol. Some people think if they move the 02's up closer and away from the open pipe that they will get a better reading, well accually your just getting the 02 hotter and give it a little while and the 02 will go out. In all, dont expect any power, only time i ever ran open headers was when i had to gto to the exhaust shop. Good luck, let us know how it sounds! And dont just say LOUD lol.

Kevin

 

Too much outside air will reach the the O2s and effect their accurately reporting the O2 in the exhaust gas if there is not a sufficient amount of pipe after their location.

edit - he beat me to it.

 

I ran open headers for about 2 weeks and it's TOO FAWKING LOUD!!!
Everything rattled and the drone was awful. Sounded awesome at idle though!!!
I noticed it was slower off the line with open headers too. Felt nuts on the top end though. I was also running really rich with the open headers. Just my $.02 from what I experienced.

 

sorry

 

I ran open headers for about two months, the car got terrible gas milage and bogged down in low rpms. Maybe with your engine it wont so much because mine was stock but it did really bad. Oh yeah lots of people dont like it when you drive next to them or anywhere around them. IF you go on a long road trip on the highway get some kind of ear protection.

 

For the misinformed people, my examples (You will have to cut and paste)

http://www.geocities.com/sqwznss/HP_open_vrs_closed.bmp
http://www.geocities.com/sqwznss/Tor...vrs_closed.bmp

Now, rationally explain how open headers will slow you down. Mind you, my setup is not the typical open header setup. I have LT's that go to dual 3" cut outs. There are aprox 12" dumps that come off the diagnal portion of the cut out. When closed, quiet as can be. When open, just a little loud.

SOTP it "feels" slower, but down the track it shows a constant gain every time. My only thought on why SOTP "feels" slower is it is an illusion. Sound level vrs increase in speed is not comprable so it "feels" slower.

 

So do you gain hp running open headers? I have tts lt headers, custom ypipe, open borla, lid, ported tb, custom tuning- predator, asp, ftra. I hit 353hp at 5800rpm while hiting my 115mph speed limiter(factory 16in tires) on my first dyno run- 99z m6. Are you saying that I would produce more hp if I bolted in my cats(y pipe can accept bolt in cats or off road pipes)? My AF was steady, kind of lean peak rpm.

 

You will make more power and go faster open headers with dumps (No cats, straight 3" pipe by 12-16 inces long)

 

i put my headers on the fri before the thunder shootout weekend and i lost about 1-2 thenths and i was open but when i put exaust i picked up tremendously i was so disgusted that i didnt race at the shootout

 

To run open headers without O2 sensor problems (throwing the LTrims waaaaaaaay positive which will kill some performance) you need to run SOMETHING behind the header. This could be a simple 18" open pipe or possibly a cuttout might be good enough in some applications. How much pipe you need behind the header collector is going to vary in large part due to the collector design and the O2 sensor placement.

Trust me, you DON'T want to drive around in or race an engine that has the Ltrims pegged at +25%. Been there, done that.

 

does it sound horrible?? i only started mine with open headers when i put my motor in... it was nice with the tr 230

 

THANKS, I appreciate the advice, I guess i wont be running open headers, damn car sounds way to loud, you can feel the vibration standing a couple feet away from it. Im planning on fitting a friends x-pipe tommorrow(friday) and run the car tommorrow night. These mac headers were way small compared to the flowtech longtubes i got, hopefully the new headers and xpipe will drop me into the 10s. Ill let you all know how i did, thanks again.

 

i know this is an old thread but i have a question for the gurus out there. I am running the old T-rex cam in my car (244/248 608/612 110) with stage 2 heads and the car makes most power between 4000-7000 rpms. I also have a 4000 stall converter. would running open headers give me more power because of the power band being in the 4000-7000 range? I really don't care how much noise it makes. thanks

 

Actually no. Open headers sort of dead heads at the atmosphere and robs you of the vacuum wave. Even running 18" extensions off the headers will give you more power.

Best would be to x pipe and then dump. That will give you the most power

 

you shouldn't be running LTFT with open headers in the first place....

 

True but he don't care. Threads from 04 lol
Tuned with open headers and some collector extensions it will make more power.

 

I agree. that's the best way to get an accurate W/B reading, the type of sensor and some extension pipes for the WB02's help too.