[99formulam6]

how does eveyone feel about them? i had to take off the exhaust to pull the tranny b/c i dropped something in the bellhousing but when i put it all back, i decided to leave the exhaust off and start the car.

hot damn i loved it. i stopped by an exhaust shop and bought two 16'' sections of 3'' pipe and used bandclamps to secure it to the headers so i wont fowl the o2's.

it is ungodly loud, and i love it. you can hear the cam alot more than you can with the 3'' duals on. it sounds like a real race car now. :lol:

 

[gettinthere]

I like it but I don't like it if that makes sense. I like how loud it is, but I hate how sloppy it sounds @ WOT.

 

[99formulam6]

i love it. i just wish the power was still there. i feel so slow, but it sounds so fast.lol.

 

[gettinthere]

On stock cubes you need the back pressure to help the power.

 

[99formulam6]

yea, i know that. but i wish there was a happy medium. im thinkin of taking off the bullets i have in my duals to see what it sounds like...

 

[gettinthere]

It'll be louder, no doubt.

 

[99formulam6]

do you think there will be enough back pressure though? right now its 3'' duals with 16'' bullets dumped at the axle. im worried about backpressure w/out the bullets..

 

[gettinthere]

Running it all the way to the axle helps. You should be okay.

 

[CamTom12]

On stock cubes you need the back pressure to help the power.

NOOOOOOO!!!!!!!!!


Without backpressure you will make more power.

it's the lack of negative pulses that's hurting your torque. Should shift your torque peak higher though.

Your Y or X junction is what creates the negative pulses in the exhaust and helps 'tune' your torque peak.

 

[gettinthere]

NOOOOOOO!!!!!!!!!


Without backpressure you will make more power.

it's the lack of negative pulses that's hurting your torque. Should shift your torque peak higher though

Won't an open ORY make more power than open headers?

 

[CamTom12]

More seat of the pants power, yes. The Y helps shift the torque peak down to a level that we use more on the street every day.

Why else would guys run header extensions only at the track?

 

[gettinthere]

But still, extending the air flow does the same basic thing. It adds slight back pressure.

I'm not saying anything is monumental, but maybe 2 ponies.

 

[CamTom12]

No, all backpressure is bad. All it does is fight the exhaust pulses coming out of the motor.

A Y or an X actually create a 'negative pressure' wave that sucks the gas out of the chamber. Tuning your exhaust is changing where in the RPM band that happens, which in turn moves your torque peak around

 

[gettinthere]

Makes sense.

 

[Jaberwaki]

I'm glad someone else gets this...
I hear back pressure bla bla bla all the time and it gets annoying explaining why it "feels" like there is more power with back pressure...

simply put the less pressure the further up the rpm band you will make power, and you will make more of it, the trade off is low end grunt and SOTP for more power and lower ET's

 

[99formulam6]

so your saying im making more power w/ the open headers...but it just doesnt feel like it since the torque is higher up in the rpm band..?

 

[CamTom12]

yup :thumbsup:

 

[five7kid]

More peak power - maybe.

But, more area under the curve power, probably not.

I was trying to get the '57 up to 100 mph at altitude, opened the headers to try to enhance that. After failing in that quest, I keep it corked up for the rest of the season, it was quicker and faster all year with the full exhaust than it was with the open headers.

Of course, I have a fairly mild cam, so a healthier cam would probably change that somewhat. However, collector extenders are the right thing because of the pulse tuning described, not because they increase "back pressure".

 

[99formulam6]

ok, so having the open headers wont help me racing from a dig then...?

i only ask b/c i have a race on sat night against a TT 97 Cobra. I raced him 2 weeks ago on street tires, and from a 1st gear punch with me spinning, i stayed right next to him. and from a dig with me spinning he was ahead by half a car....now i have on Nittos, and im running him again this sat night.

should i put the exhaust back on?

 

[1970judge]

You lose backpressure not to mention during winter can burn up your valves.