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backpressure

This is a discussion on backpressure within the General Help forums, part of the LSx Technical Help Section category; Originally Posted by LS2Tuner Take a look next time you go to the track and notice how many 7 sec. ...

  1. #21
    member since may 2000 nhraformula's Avatar
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    Quote Originally Posted by LS2Tuner View Post
    Take a look next time you go to the track and notice how many 7 sec. door cars run mufflers.........Then again it will depend on weather or not there is any really fast cars there......... You actually build MORE power with a "good" exhaust than with nothing.Open headers is for the deaf old guys......
    The exhaust helps scavenge out the exhaust gasses which speeds up the process which builds volocity which builds power!!!!
    so all the top fuel guys are wrong???
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    no, but they have way more power..

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    member since may 2000 nhraformula's Avatar
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    Quote Originally Posted by 9t8z28 View Post
    Yes, I know! That is what I have been trying to say!!!!!!!!!!!!!!!!
    I wanted a response as to why backpressure was a MYTH!!!!!!
    people say you need backpressure and thats bullshit.
    go to a dyno with two like wise modded cars with the only difference of one guy has a full exhaust and the other doesnt.
    the guy running open headers will make more power, its been proven time and time again.

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    Pathelogical Liar BlackLT1Z28's Avatar
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    Its true. Ask Mr. Luos for his dyno sheets or vids of his dyno runs with his cutouts opened and closed. He gained ~8hp with the cutouts open over his full true-dual setup. But the sacrifice is low-end torque. But he ain't missin' it with all that power he's making up in the mountains.

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    Nitrous Tuner LS2Tuner's Avatar
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    Quote Originally Posted by nhraformula View Post
    so all the top fuel guys are wrong???
    I shouldn't even waste my time if your bright enough to compare a 7500-8100Hp nitro blown inj. motor to ANY motor that is being discussed on this site!!!

    Do you even have any clue of how nitro even works............ If you pour a shot glass full of nitro on a metal table and light it.............



    NO it won't burn!!! Now come back to the table with a 5lb. and strike that puddle and see what happens.............

    SO IN PLAIN ENGLISH "DOOR CARS" WOULD MEAN NOT A MOTOR WITH A 14-71 BLOWER AND NOT RUNNING ON NITRO SO NO WAS NOT REFERING TO ANY OF THE MILLION $ PRO TEAMS WITH THE MOST EXTREME MOTORS!!!

    Go to ANY PSCA race and then tell me ALL the cars there are wrong!!!!
    http://www.pscaracing.com/
    Don't be afraid of the bottle!!! Be afraid of your tune!!!

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    member since may 2000 nhraformula's Avatar
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    Quote Originally Posted by LS2Tuner View Post
    I shouldn't even waste my time if your bright enough to compare a 7500-8100Hp nitro blown inj. motor to ANY motor that is being discussed on this site!!!

    Do you even have any clue of how nitro even works............ If you pour a shot glass full of nitro on a metal table and light it.............



    NO it won't burn!!! Now come back to the table with a 5lb. and strike that puddle and see what happens.............

    SO IN PLAIN ENGLISH "DOOR CARS" WOULD MEAN NOT A MOTOR WITH A 14-71 BLOWER AND NOT RUNNING ON NITRO SO NO WAS NOT REFERING TO ANY OF THE MILLION $ PRO TEAMS WITH THE MOST EXTREME MOTORS!!!

    Go to ANY PSCA race and then tell me ALL the cars there are wrong!!!!
    http://www.pscaracing.com/

    well, i can see you have no fuckin clue

    Nitro (NG), also known as nitroglycerine, trinitroglycerin, and glyceryl trinitrate, is a chemical compound. It is a heavy, colorless, addictive, oily, explosive liquid obtained by nitrating glycerol. It is used in the manufacture of explosives, specifically dynamite, and as such is employed in the construction and demolition industries, and as a plasticizer in some solid propellants. It is also used medically as a vasodilator to treat heart conditions.

    now go get some nazzzzz while youre at it

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    member since may 2000 nhraformula's Avatar
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    Quote Originally Posted by LS2Tuner View Post
    I shouldn't even waste my time if your bright enough to compare a 7500-8100Hp nitro blown inj. motor to ANY motor that is being discussed on this site!!!

    Do you even have any clue of how nitro even works............ If you pour a shot glass full of nitro on a metal table and light it.............



    NO it won't burn!!! Now come back to the table with a 5lb. and strike that puddle and see what happens.............

    SO IN PLAIN ENGLISH "DOOR CARS" WOULD MEAN NOT A MOTOR WITH A 14-71 BLOWER AND NOT RUNNING ON NITRO SO NO WAS NOT REFERING TO ANY OF THE MILLION $ PRO TEAMS WITH THE MOST EXTREME MOTORS!!!

    Go to ANY PSCA race and then tell me ALL the cars there are wrong!!!!
    http://www.pscaracing.com/
    i know this much, with open headers my 73 T/A would run 2 tenths faster compared to closed dumps. it was no 7000 hp car either, it was youre run of the mill back halved car.

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    Nitrous Tuner LS2Tuner's Avatar
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    Well JR. we use Nitromethane in our alcohol motors all the time to gain power.....At a 10-15% ratio cause it stays dissolved with alcohol.....But you already knew that too. I guess you didn't understand in plain english the first time cause I didn't spell it out for you. http://en.wikipedia.org/wiki/Nitromethane

    And if you had a clue you would know that your carb tune for open headers and for exhaust is different to get the most horsepower. But you just go on with your top fuel tune there........NHRA...

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    member since may 2000 nhraformula's Avatar
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    Quote Originally Posted by LS2Tuner View Post
    Well JR. we use Nitromethane in our alcohol motors all the time to gain power.....At a 10-15% ratio cause it stays dissolved with alcohol.....But you already knew that too. I guess you didn't understand in plain english the first time cause I didn't spell it out for you. http://en.wikipedia.org/wiki/Nitromethane

    And if you had a clue you would know that your carb tune for open headers and for exhaust is different to get the most horsepower. But you just go on with your top fuel tune there........NHRA...
    who said anything about a carb?? i sure didnt. you shouldnt assume

    btw, im 37, far from a JR.
    im well aware what nitromethane is. but i just cant stand when people call it nitro, two different things.

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    Nitrous Tuner LS2Tuner's Avatar
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    K sorry for not USING PLAIN ENGLISH with you. O'h your 73 was blown and inj. right.....? O'h sorry when I say inj. that means injected.

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    all i have to say is look at peoples numbers, open dumps vs. closed.
    open dumps always make more h.p.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    O.K. I am not saying that anybody is right, but why is this?
    A friend of mine put dual on his truck that originally was a system simular to a camaro stock setup. Well, it turn it into a dog.
    Another one of my friends vehicles exhaust bused off(rusted) right after the cat, once again it turned it into a dog. Why is that. And you dont have to get sarcastic with me, I just want to get to the bottom of this! That all!

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    I guess those dogs won't hunt.

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    I figured "race" or "drag" cars ALSO didnt have full exhaust systems cuz its extra weight. Why have mufflers and extra piping when its built for a track?

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    As stated earlier, open exhaust is more H.P. and a complete exhaust will give more TORQUE. I believe someone quoted Mr. Luos dyno numbers. Torque is what gets you going and H.P. is what keeps you going at speed.

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    Quote Originally Posted by SSTODD View Post
    As stated earlier, open exhaust is more H.P. and a complete exhaust will give more TORQUE. I believe someone quoted Mr. Luos dyno numbers. Torque is what gets you going and H.P. is what keeps you going at speed.
    even if a person loses some tq down low, guys like me with stall converters are not affected.

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    oh i just love the guys that say you need backpressure, complete bs that someone told you and now you think its fact. If your so sure your right then show me some links that proves your claim. I have tons of links proving the less backpressure you have the better, and for all cars... Yes you do loose a few lbs of torqe around the 2k mark but the hp gain in the 5k mark outweighs any small torqe gain way down low and were talking like 5lbs of torqe, nothing that any of us can feal and on top of that almost none of us spend any kind of time under 2k rpm when racing, hell my launch is over 2k

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    Member LS1WS6's Avatar
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    oh one other thing how many of you go down to 2k when you shift the trans, um none so the torqe gain down there has squat to do with racing.

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    Quote Originally Posted by LS1WS6 View Post
    oh i just love the guys that say you need backpressure, complete bs that someone told you and now you think its fact. If your so sure your right then show me some links that proves your claim. I have tons of links proving the less backpressure you have the better, and for all cars... Yes you do loose a few lbs of torqe around the 2k mark but the hp gain in the 5k mark outweighs any small torqe gain way down low and were talking like 5lbs of torqe, nothing that any of us can feal and on top of that almost none of us spend any kind of time under 2k rpm when racing, hell my launch is over 2k
    heres the problem, they cant disprove the fact that when racing an open exhaust will net better E.Ts and traps.
    ive said it before and will say it again, backpressure=myth

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    Senior Member mrr23's Avatar
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    then let me.

    Now here's results of my exhaust endeavors. This is with 200 n2o. the stock vs cutout was same day for the nitrous runs.

    distance --- stock --- cutout --- cutout colder --- Bassani
    60ft ------- 1.987 --- 2.074 -------- 2.020 --------1.969
    1/8 -------- 7.902 --- 7.912 -------- 7.990-------- 7.739
    mph ------- 93.20 --- 93.97 -------- 92.16 ------- 98.60
    1/4 ------- 12.102 -- 12.080 ------- 12.191 ------ 11.814
    mph ------ 117.12 -- 118.06 -------- 118.20 ----- 121.35


    now, why did i gain .3 and 3 mph over stock exhaust with a cutout vs the bassani tru-duals?
    in the first two, you get to see exactly why having an open exhaust doesn't work. i lost in the 60ft only to gain it on the big end. overall gain, .02


    NA times

    distance --- stock --- cutout --- cutout colder --- Bassani
    60ft ------- 2.033 ---- 2.073 ------ 2.031--------- 2.044
    330ft ------ 5.788 ---- 5.822 ------ 5.759 -------- 5.723
    1/8 -------- 8.808 ---- 8.833 ------ 8.729 -------- 8.656
    mph ------- 82.33 ---- 82.55 ------ 83.70 -------- 84.27
    1000ft ---- 11.404 ---- blank ----- 11.278 ------- 11.196
    1/4 ------- 13.606 --- 13.636 ----- 13.449 ------- 13.345
    mph ------ 101.66 ---- 101.58 ---- 104.05 ------- 105.15

    it's not about backpressure, it's about exhaust velocity vs area of exhaust piping. too large of a pipe and the velocity of the exhaust is slowed down until the point where the volume of the exhaust matches the area of the piping. the whole water hose thing comes to mind.

    you turn on the water hose to the point where it's slowly coming out of the hose. not dripping out, but flowing not at full capacity of the hose size. now, you go and squeeze the hose end. water comes out of it faster and farther.

    now, turn the water on full tilt. the water is coming out at full volume. go and squeeze the hose end. the volume now is less and you can feel the hose backing up and see the hose swell. that's backpressure. backpressure is when you don't have enough area of piping to get the volume out.

    finding the right size pipe for your exhaust is the fun part. for most stock type applications a single 3", or a dual 2.5" will do.

    as far as all those race car at the track, who makes a muffler for a top fuel dragster making in excess of 6000 hp on a 800+ CID blown motor that wouldn't be a restriction? hell, the pipes for each cylinder are about the size of our stock intermediate pipe of 2.75", or larger.
    Last edited by mrr23; 01-21-2007 at 07:47 PM.

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