not enough back pressure??

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not enough back pressure?? - 4/28/2003 3:25:32 PM    DougBlevins   Posts: 72 Joined: 1/20/2003 From: United States Status: offline when u put headers on and open up the exaust more, does back pressure become an issue? i had straight pipes and 1 chamber flowmaters but after adding MAC 1 5/8 equal lenth shorties and a 70mm TB, i went to an H pipe and 2 chamber flowmaters b/c of everyone telling me i wouldn't have near enough backpressure. now i miss the way my car used to sound and i wondering if quieting it down was even necessary. thanks. Post #: 1

not enough back pressure?? - 4/28/2003 7:00:59 PM    91GT5.0   Posts: 282 Joined: 3/7/2003 From: United States Status: offline You should keep the headers, put the old exhaust back on if you want (straight pipes and 1 chambers are too loud for me on a street car, but that's just me and the cops' opinion), but change the throttle body to either a 65mm or your stock one. Prolly your stock one because a stock engine really won't get any benefit from a bigger MAF until higher RPM's. The stock one should do just fine. If you remember, you prolly lost some lowend power when you put the 70mm on. Put a smaller one on and your powerband should drop some RPM's, i.e. more lowend. (in reply to DougBlevins) Post #: 2

not enough back pressure?? - 4/28/2003 11:10:10 PM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline YOU DON'T WANT f**kING BACK PRESSURE. ONE MORE DAMNED TIME AND THE KITTEN GETS IT. (in reply to DougBlevins) Post #: 3

not enough back pressure?? - 5/9/2003 4:43:55 AM    damein   Posts: 7 Joined: 5/9/2003 From: United States Status: offline hmm back pressure.... well im not 100% on this.. but back pressure only really comes into play at lower rpms.. like from idle to around 1500 rpms.. and if you drive a stang and you race it im sure you dont spend very much time in the 1500 rpm range.. casue if ya do i bet you loose alot of races.. and i asked this from 20 diff mechanics at 3 differant ford delaerships.. and my father is also a ford mechanic.. so im sure he knows a lil about stangs considerign he works on them all day long.. but hey dont take my word for it if you dont want to.. i never said i was 100%sure but hey im going by what i was told (in reply to DougBlevins) Post #: 4

not enough back pressure?? - 5/9/2003 3:44:33 PM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline Backpressure is the same on any car. What it is is "back" "pressure" sound that out. It's backed up by a restriction, the gasses can't flow fast enough. I don't see how that is beneficial to the power making of a motor, ANY motor. High exhaust velocity with zero backpressure is ideal, and extremely hard to get. However, Very low backpressure and high velocity is awsome. By jumping to say...a 6" pipe you would literally have no backpressure. BUT, the exhaust VELOCITY would be jack. Therein lies the problem, finding a diameter that offers high velocity and no backpressure for the RPM range the engine is used in the most. This is the same reason why X pipes can make as much, if not more, power and torque than open headers. Better velocity. (in reply to DougBlevins) Post #: 5

not enough back pressure?? - 5/10/2003 1:48:25 AM    jarrett   Posts: 10 Joined: 4/1/2003 From: United States Status: offline on a 5.0 you definetly need backpressure. on my 88 i ran open headers at the track because it sounded good. however my low end torque suffered greatly. backpressure can mean seconds on an et. my car ran 15.0 at 97. 15.0 is really slow but the fact that it was at 97 meant that it had the horsepower to run a mid-13.I talked to a guy at the track with a 10 second malibu and he told me that with some pipe my car could gain over a second in the quarter. this is just something to think about. (in reply to DougBlevins) Post #: 6

not enough back pressure?? - 5/10/2003 2:10:38 AM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline Blah Blah Blah BLAH. The open headers increase the flow velocity AT HIGH RPM'S. Go talk to some guys that build REAL cars and see what they say. I'd LOVE to hear guys from Nascar, F1, IRL, ect., say that. They know it's all about fluid dynamics. Nascar's are all running X pipes for a reason, they can tune it for the high RPM's and still meet the noise requirements. With very little-no back pressure, but high exhaust velocity. (in reply to DougBlevins) Post #: 7

not enough back pressure?? - 5/10/2003 8:18:15 AM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline This is where my buddy JEEP proves hios mopar-ishness. You DO want backpressure. Dont take advice from a guy who has a 2.5 inch (or whatever stupid thing you came up with) on a saturn. You want youre exhaust to be free-flowing but NOT at the expense of back pressure. (in reply to DougBlevins) Post #: 8

not enough back pressure?? - 5/10/2003 8:22:17 AM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline Jeep, he's not building a NASCAR He needs back pressure (in reply to DougBlevins) Post #: 9

not enough back pressure?? - 5/10/2003 7:01:55 PM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline I've got a stock puny 1 7/8" on the satty, danka-vara-much. We've dyno'd this stuff on the Chevelle I used to drive. Guess when it made the most power? On 3.5" X back pipes, no mufflers, and equal length long tubes. We had the highest exhaust velocity with that combo from 5000-8000 RPM, where I drove it the most. The car absolutely HATED backpressure, and I've yet to personally see a motor that liked it. (in reply to DougBlevins) Post #: 10

not enough back pressure?? - 5/10/2003 8:59:38 PM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline Sorry I thought I rememberd you saying you had some big ass exhaust on the that gay saturn of yours. Still, the no back pressure thing must be some type of myth made up by you mopar yutzs' (in reply to DougBlevins) Post #: 11

not enough back pressure?? - 5/10/2003 9:42:21 PM    makarovboy   Posts: 270 Joined: 4/26/2003 From: United States Status: offline I think Jeep's right. He isn't saying eliminate all back pressure, it depends on the pipe diameter, length, etc. You run a straight header, there may be no back pressure and your torque suffers. But the right diameter pipes, without mufflers, will free flow and give you the torque you need because you have built in SOME restriction. I admit you probably can't drive it on the street, but the smaller muffler and x-pipe would be less restrictive than all that hardware he's putting back on. (in reply to DougBlevins) Post #: 12

not enough back pressure?? - 5/10/2003 10:48:02 PM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline He's says the need for back pressure on any car is a myth. That is a flat out wrong statement!!!!!! (in reply to DougBlevins) Post #: 13

not enough back pressure?? - 5/10/2003 11:52:55 PM    makarovboy   Posts: 270 Joined: 4/26/2003 From: United States Status: offline Yeah lloyd, I agree with that. But the way he is explaining it, you do get back pressure, maybe he doesn't understand that. If no back pressure was required then just run straight out the heads. I ran a Y-pipe on my dirt car and had loads of torque without mufflers. It depends on how the pipe is engineered. Would'nt you agree with that? I would ask why top fuel cars run a certain length pipe with a certain bend. Why not straight out about two inches from the head. I totally agree with you, but jeep is talking about back pressure in every statement he makes whether he knows it or not. All the combo's he mentions create a certain amount of needed back pressure. You need back pressure, jeep! (in reply to DougBlevins) Post #: 14

not enough back pressure?? - 5/11/2003 1:48:19 AM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline The reason you don't run straight heads is because the exhaust gases aren't scavanged effeciently (that and nevermind having a workable engine bay). They just plop out. With a header, the velocity is increased and helps to create a vacume (on equal length long tubes) to help scavange out exhaust from the rest of the cylinders. All I'm saying is this: high velocity is what you want. How can you possibly think that there's backpressure with high velocity? (in reply to DougBlevins) Post #: 15

not enough back pressure?? - 5/11/2003 5:53:39 PM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline Maybe you should just stop talking. LOL (in reply to DougBlevins) Post #: 16

not enough back pressure?? - 5/12/2003 6:56:10 AM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline Or, maybe you could please provide some proof as to how I'm wrong, instead of just saying "you're wrong". If I am wrong, and someone can prove it, well, I'm wrong. Big sh*t. But I'm just going off of personal experiance here. (in reply to DougBlevins) Post #: 17

not enough back pressure?? - 5/12/2003 3:34:10 PM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline WRONG (in reply to DougBlevins) Post #: 18

not enough back pressure?? - 5/12/2003 5:45:39 PM    jeep45238   Posts: 2199 Joined: 3/31/2003 From: United States Status: offline Good bunch of proof...... (in reply to DougBlevins) Post #: 19

not enough back pressure?? - 5/13/2003 8:03:50 PM    lloydchristmas   Posts: 708 Joined: 2/14/2003 From: United States Status: offline I liked it (in reply to DougBlevins) Post #: 20

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