Backpressure opinions!?!

[MR.G]

Alright,so my 00' SS 6spd has Hooker longtube headers,3" Texas X-pipe,NO cats & bullit race mufflers.Under the hood is the SLP Flowpac system as well.

Some say there is not enough backpressure while others say that is outdated info so I'm just curious what your input is on the subject?

HOPEFULLY someone can prove one way or the other?????

Thanx!

[bills98ta]

The X pipe, H pipe, and Y pipe all reduce exhaust scavenging. Therefor, I think you have nothing to worry about !!!

[danziger]

You don't need backpressure at all. The less restrictive exhaust may cost you some low-end as it moves the power-band up the RPM range, but you won't lose power...you'll gain it.

[The Scientist]

Excatly what danziger said. You need backpressure at low rpms to produce torque but not at higher rpms.

[Anthracis]

ditto

[nhraformula]

backpressure=myth
look at race cars, they have dumps off the headers.

[mrr23]

backpressure=myth
look at race cars, they have dumps off the headers.

backpressure = myth is correct. the correct terminology that should be used is velocity.

race cars - can't compare that to a street car. there's a balance needed. pipe sizing to exhaust output/rpm.

you want to achieve zero backpressure. problem is you can't do that for all rpms. the larger the pipe, the less backpressure. but too large costs you in the lower rpms due to slow velocity.

i'll use the ole' garen hose example:

barely turn the faucet on to where the water slowly comes out (low rpms). this means not enough water to fill the entire area of the hose. now, pinch the hose. the water starts coming out faster and shoot further out. (this is where the whole backpressure myth confuses people). now, we have set the hose diameter to meet the requirements of the output of water.

now, turn the water on full blast (high rpms). water is coming out quickly and lots of it. try and pinch it off. the hose swells up. even though the water is shooting further away, there is less volume coming out now. that is what's called backpressure. the point where the area of the hose cannot support the volume of water coming out.

so, where is the happy medium, when it comes to street cars? here's little guide:

single = dual
2.50" ---- 2.00"
3.00" ---- 2.25"
3.50" ---- 2.50"

not only is rpms a factor, but also horsepower output. for most 400-500hp and up to 6500 rpms, a single 3.5", or dual 2.5" will be a good medium with the dual having a better overall curve.

[nhraformula]

if your stalled as i, you dont worry about low end rpm.

[mrr23]

if your stalled as i, you dont worry about low end rpm.

i do, because when i'm driving around, i'm under the stall speed of 3400. you are focused on racing. there's more to a streetcar than just racing.

[9t8z28]

i do, because when i'm driving around, i'm under the stall speed of 3400. you are focused on racing. there's more to a streetcar than just racing.

=+1

[nhraformula]

i do, because when i'm driving around, i'm under the stall speed of 3400. you are focused on racing. there's more to a streetcar than just racing.

even when not racing, the shift extension of the stall keeps your rpm higher than stock. any low end loss of a some tq shouldnt even be felt.

[mrr23]

depends on throttle input and STR of converter. normal driving for me is 3500 rpm shift point that drops to 2000 rpms due to converter.

[DirtyDave311]

Here is my expirence with back pressure. I have a 1970 baracuda with a 440 in it. We just got done with the car but the exhaust was on back order so we ran it without the back half of the exhaust for a good while. We were running headers coming down and a 1.5ft long 3.5" wide pipe off of each header. I ran 10.86 with that set-up.

This car is also a weekend rider too, anyway we started to notice that when we would change the plugs about once a month that oil was coming out of the spark plug holes. Well the exhasut came in and we put it on well when we ran it again my time actually fropped from a 10.86 to a 10.62 and the oil problem stopped.

Also im an apprentance at a shop doing SVT training and i see the same oil problem in cobra's that try and run off road pipes in place of the cats and havetaken off the mufflers,

I mean im not to sure if back pressure has anything to do with it but from what im guessing back pressure has something to do with it

[mrr23]

the mufflers provided a scavenging affect. they helped to pull the exhaust out, causing a vacuum behind the leading pulse. this helps pull the next one out.

[MR.G]

Guys...I appreciate all the helpfull input!!!