Pre Cat Manifold
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Ok I am doing this as well but..
First off the pre-cat keeps backpressure. Dont gut it. Second, Hotshot and Stillen make 2 inch downpipes. I measure mine and stock its 1 13/16. The downpipe should be 2 inches. Third, I am heat coating and wrapping the manifold for the most velocity out of the header. Dont do 2 1/4! I guarantee a loss in power. Also a flex pipe isnt really needed. Thats gonna just hurt flow.
First off the pre-cat keeps backpressure. Dont gut it. Second, Hotshot and Stillen make 2 inch downpipes. I measure mine and stock its 1 13/16. The downpipe should be 2 inches. Third, I am heat coating and wrapping the manifold for the most velocity out of the header. Dont do 2 1/4! I guarantee a loss in power. Also a flex pipe isnt really needed. Thats gonna just hurt flow.
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Oh yeah
Did you ever see how big the pre cat is? That things friggen huge. If thats gutted you may no only not pass emissions but lose hp. Cause thats like 4 inches wide! If I dont like the gain im getting I may investigate into 1/2 gutting it if possible.
Did you ever see how big the pre cat is? That things friggen huge. If thats gutted you may no only not pass emissions but lose hp. Cause thats like 4 inches wide! If I dont like the gain im getting I may investigate into 1/2 gutting it if possible.
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One more thing
Have you checked to see if the exhaust manifold ports can get dremeled? I am still investigating into this. I am doing one step at a time. I also just bought a bypass valve to open header at higher rpms.
Have you checked to see if the exhaust manifold ports can get dremeled? I am still investigating into this. I am doing one step at a time. I also just bought a bypass valve to open header at higher rpms.
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Ok Goku, just got word from Shawn
Oh this is the deal. For the best setup. A 2 1/4 downpipe, dont gut the pre cat, port the exhaust manifold(where the flanges are) if possible, and wrap and heat coat the manifold. This will give awesome results. The gutted pre cat will be detrimental to torque.
Oh this is the deal. For the best setup. A 2 1/4 downpipe, dont gut the pre cat, port the exhaust manifold(where the flanges are) if possible, and wrap and heat coat the manifold. This will give awesome results. The gutted pre cat will be detrimental to torque.
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ok, don't listen to a fu(kin thing NISSANFREAK has to say.
DO what ya want, 1st of all. Gutting the pre cat will most definately lose torque, but the hp gains high end make up for it, and then some. Just like a header, when installed, you lose torque, but gain hp in the power band. Larger piping, yes you lose torque, but you gain hp as a result.
I would guess a good way to start off is:
match port the manifold to the head
gut the precat, but not completely, because it is so large
match port the new down pipe with the end of the manifold at the flange
flex pipe won't hurt anything, and if you don't have it, you crack the manifold
i think a 2" downpipe is good enough, but if you wanna go 2.25", that should be ok, but you will lose a little more low end, and might not get the expected gains in high end. A large downpipe is only good for a forced induced car, like turbo, n2o, or super charged.
DO what ya want, 1st of all. Gutting the pre cat will most definately lose torque, but the hp gains high end make up for it, and then some. Just like a header, when installed, you lose torque, but gain hp in the power band. Larger piping, yes you lose torque, but you gain hp as a result.
I would guess a good way to start off is:
match port the manifold to the head
gut the precat, but not completely, because it is so large
match port the new down pipe with the end of the manifold at the flange
flex pipe won't hurt anything, and if you don't have it, you crack the manifold
i think a 2" downpipe is good enough, but if you wanna go 2.25", that should be ok, but you will lose a little more low end, and might not get the expected gains in high end. A large downpipe is only good for a forced induced car, like turbo, n2o, or super charged.
ok here the reason im doing the flex pipe is because mines has a leak and need to be replaced...doing the down pipe 2 1/4 shouldnt be a problem ..as for top end i really dont need that ..im not running my car for top end just more torque and low end ..i have a spare Pre cat anyways so i can always replace it back to stock ..i belive Nismo gutt his cat on this altima and hes spraying NOS ..he gave me the idea so imma go ahead and try it ...he seems to know what hes doing so ,imma try it ....does anyone have a damn dremmel ? i cant seem to find any friends with one i can borrow ..i might just have to do that another time ..anyways i should have it done next week (hopefully) i know theres alot of mixed opioions which is good.. it shows me theres guys on this site that have differnt views ...hopefully what im doing isnt a waste of time and gain some HP or torque ..and the reason i rather have low end is this reason : if your traveling on high way speeds..everyone is going to be travel at that speed ..doesnt really matter how much HP you have on highways speeds..i rather have the low end to get me there from the start off line ...well wish me luck i keep you guys update .thanks nismo (where are you bro?)
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you have the wrong idea about torque. Yes, it gets you off the line a little faster, but once you're in the end of first and shifting to 2nd, torque is overpowered by hp. Why would someone put on a header when they know they're losing torque? Because they also they're gaining hp in the power band and it makes up for that little loss.
Doing what you plan on doing will not gain you torque, but rather hp. Still seems like a good idea and good luck, but you'll be gaining hp, not torque. If anything, you'll lose torque, because of loss of back pressure
Doing what you plan on doing will not gain you torque, but rather hp. Still seems like a good idea and good luck, but you'll be gaining hp, not torque. If anything, you'll lose torque, because of loss of back pressure
thanks for the correction ...so do you guys think its worth the labor in putting the Gutt Pre cat in ? or should i just leave the stock one with new down pipe? maybe i should just have them installed the piping in 1st and see how it runs ... then later on try out the gutt Pre cat ....
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First off your 1fastaltima!
Your so dumb for saying that. Seeing how "Shawn" said to not gut the cat cause you will lose torque! You can gut it and lose low end. I dont think its worth it on our cars since we need all around power especially in launching. Have you seen the precat!! That things f-ing huge! 1/2 gut it? Man your stupid 1fastaltima! Cause this dude wants to pass emissions! Gutting the precats going to fail your emissions! I already said what to do. 2 1/4 downpipe as from the words of "Shawn". Shawn knows his shit and 1fastaltima get a timeslip!
Your so dumb for saying that. Seeing how "Shawn" said to not gut the cat cause you will lose torque! You can gut it and lose low end. I dont think its worth it on our cars since we need all around power especially in launching. Have you seen the precat!! That things f-ing huge! 1/2 gut it? Man your stupid 1fastaltima! Cause this dude wants to pass emissions! Gutting the precats going to fail your emissions! I already said what to do. 2 1/4 downpipe as from the words of "Shawn". Shawn knows his shit and 1fastaltima get a timeslip!
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NISSANFREAK, you call yourself a "sleeper"? Why? These are your mods:
94 NISSAN ALTIMA(sleeper)
Performance:
-APC customed short shifter
-Stage 2 RPS clutch
-Dynomax HI-flow cat
-Dynomax Ultraflow Muffer w/ 2 1/4 inch piping
-PRI CAI
-PRI Motor Mounts
-Advanced Timing
-Indexed and Gapped Plugs
-NGK Blue Racing Wires
hell, half of those i wouldn't even list. Gapped plugs? Blue wires? Short Shifter? Those help out maybe .00001 of a sec. You might be sleeper to grannies in Hyundia Tiburon's, but in the real world of street racing, you're a joke
. And i have about 15 slips, how about you?
I didn't know that he was trying to pass emissions, oh that's right! He's not! He lives here in FL where there are no emission controls. He can gut that cat all he wants, it's his project. And yes i've seen the pre cat, i had to take the fu(ker out when i put my header on. I realize the size of it, hence the reason for not gutting it completely. But doing a little will help. And you'll lose torque, i already addressed that issue. The gains up top will over power the lose in low end.
originally posted by NISSANDUMBASS
I suggest working with it (pre cat). Do a little, and try it out, do a little more, til you get it how ya like it. Why else would people put larger exhaust, headers, and hi flo muffler on their cars? FOR MORE HP, that's why. Everyone knows about the lost torque, you don't have to be a rocket scientist for that one.
94 NISSAN ALTIMA(sleeper)
Performance:
-APC customed short shifter
-Stage 2 RPS clutch
-Dynomax HI-flow cat
-Dynomax Ultraflow Muffer w/ 2 1/4 inch piping
-PRI CAI
-PRI Motor Mounts
-Advanced Timing
-Indexed and Gapped Plugs
-NGK Blue Racing Wires
hell, half of those i wouldn't even list. Gapped plugs? Blue wires? Short Shifter? Those help out maybe .00001 of a sec. You might be sleeper to grannies in Hyundia Tiburon's, but in the real world of street racing, you're a joke
. And i have about 15 slips, how about you?I didn't know that he was trying to pass emissions, oh that's right! He's not! He lives here in FL where there are no emission controls. He can gut that cat all he wants, it's his project. And yes i've seen the pre cat, i had to take the fu(ker out when i put my header on. I realize the size of it, hence the reason for not gutting it completely. But doing a little will help. And you'll lose torque, i already addressed that issue. The gains up top will over power the lose in low end.
originally posted by NISSANDUMBASS
Oh well since you're the genius with plugs and wires and a clutch, he should listen to you, i'm sorry i forgot. You also have weight reduction, ooooh.
I suggest working with it (pre cat). Do a little, and try it out, do a little more, til you get it how ya like it. Why else would people put larger exhaust, headers, and hi flo muffler on their cars? FOR MORE HP, that's why. Everyone knows about the lost torque, you don't have to be a rocket scientist for that one.
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2,049 Posts
Sounds good GOKU!
Honestly dont **** with the precat. Its better to have some torque then lose. I mean do what you want. But I dont like the idea of getting spanked off the line. Me personally.
Honestly dont **** with the precat. Its better to have some torque then lose. I mean do what you want. But I dont like the idea of getting spanked off the line. Me personally.
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2,049 Posts
Umm no
I rather win off the line and the long run! You want both torque and hp! You dont want lower torque then hp. I guess its whatever you want. I am doing what I am doing. Gut your cat if you want. I guess I like pull you back in your seat power and high end as well.
I rather win off the line and the long run! You want both torque and hp! You dont want lower torque then hp. I guess its whatever you want. I am doing what I am doing. Gut your cat if you want. I guess I like pull you back in your seat power and high end as well.
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