exhaust upgrade question
September-8th-2004, 01:38 PM
#16
Guest
Posts: n/a
agreed that increasing the diameter of the piping will also increase the average path/crossectional area where air can pass, BUT BUT BUT, this is only if increased too much like 3 or 3.25, a 4 cylinder engine with a .5 increase in the piping will have no adverse efects & NO LOSS OF POWER, and the better flow will outway the loss of minute almost none existant so much so it will never be noticed,velocity, again 3 inch piping would have a more evedent efect but even with that it still would be hard to notic at all, but not 2.5. with that ther is only a .5 increase and that is not enough to cause problems. especi
ASWELL THIS STILL HAS NOTHING TO DO WITH THE HP OF THE ENGINE, but the egine leter size compression ration and a few other factors, but not the HP.
and in responce to
Quote:
Originally Posted by ooosirkooo
For the piping HP levels dont matter (if they did the exaust on a decked out Skyline would have to be 7 inches as the HP is arount
900. but in the end its your choice good luck.
If tuned accordingly, HP and volumetric flowrate are directly proportional. However, in street applications peak HP shouldn’t be as
much of a concern as what is under the torque curve.
The volumetric flowrate is not proportionel to the cars hp no matter how you tune, here is a calculation to show what your volumetric flowrate is on your car
Actual volumetric flow rate (ft3/minute) is equal to MFK = Mass flow rate taken from Auto Tap log (lb/minute) OVER d2 = Density of air for the intake air (lb/ft3) there are other calculations for other types of engines and other ways to calculate it for your own engine, but this has no connectrion to the HP lever
So you can continue to sugest 2.25, but I DONT if the guy plans to do any mods, and if hes discussing increasing the piping system I would assume he plans to do other mods aswell. this will need the 2.5 pipe
ASWELL THIS STILL HAS NOTHING TO DO WITH THE HP OF THE ENGINE, but the egine leter size compression ration and a few other factors, but not the HP.
and in responce to
Quote:
Originally Posted by ooosirkooo
For the piping HP levels dont matter (if they did the exaust on a decked out Skyline would have to be 7 inches as the HP is arount
900. but in the end its your choice good luck.
If tuned accordingly, HP and volumetric flowrate are directly proportional. However, in street applications peak HP shouldn’t be as
much of a concern as what is under the torque curve.
The volumetric flowrate is not proportionel to the cars hp no matter how you tune, here is a calculation to show what your volumetric flowrate is on your car
Actual volumetric flow rate (ft3/minute) is equal to MFK = Mass flow rate taken from Auto Tap log (lb/minute) OVER d2 = Density of air for the intake air (lb/ft3) there are other calculations for other types of engines and other ways to calculate it for your own engine, but this has no connectrion to the HP lever
So you can continue to sugest 2.25, but I DONT if the guy plans to do any mods, and if hes discussing increasing the piping system I would assume he plans to do other mods aswell. this will need the 2.5 pipe
September-8th-2004, 08:41 PM
#17
Registered User
Join Date: Oct 2001
Location: Des Moines, IA
Posts: 381
The main reason, I recommend the smaller piping is becuase this isn't a race car. Personally, I like to have more low and mid range power where I spend the majority of my driving at.
Do you drive? If so, you're probably familiar with the accelerator pedal. The further you press it down, the more power the engine produces. The accelerator pedal is directly linked to the throttle. The throttle controls the volumetric flowrate. How is this not directly proportional to horsepower?
Originally Posted by ooosirkooo
The volumetric flowrate is not proportionel to the cars hp no matter how you tune, here is a calculation to show what your volumetric flowrate is on your car
Actual volumetric flow rate (ft3/minute) is equal to MFK = Mass flow rate taken from Auto Tap log (lb/minute) OVER d2 = Density of air for the intake air (lb/ft3) there are other calculations for other types of engines and other ways to calculate it for your own engine, but this has no connectrion to the HP lever
Actual volumetric flow rate (ft3/minute) is equal to MFK = Mass flow rate taken from Auto Tap log (lb/minute) OVER d2 = Density of air for the intake air (lb/ft3) there are other calculations for other types of engines and other ways to calculate it for your own engine, but this has no connectrion to the HP lever
Do you drive? If so, you're probably familiar with the accelerator pedal. The further you press it down, the more power the engine produces. The accelerator pedal is directly linked to the throttle. The throttle controls the volumetric flowrate. How is this not directly proportional to horsepower?
September-8th-2004, 10:30 PM
#18
The man behind the mask
Join Date: Oct 2003
Location: Birmingham, AL
Posts: 11,572
in all actuality GNO is correct. Backpressure does NOT equal torque. PROPER exhaust gas flow promotes scavaging which promotes torque.
Also, someone else said it earlier and it's basic physics: Just like with an intake, you can have 4" piping all the way down the length of the car but if your muffler has a 2" outlet you're only going to flow that 2"s. Your smallest restriction is going to be your biggest inhibitor. I have a header that meets at a 2.5" collector...it then plumbs into a 2.14" stock midpipe...after that it wouldn't matter how big my catback was....I'm NEVER going to flow anymore air than that 2.14" mid-pipe.
If you are designing a FULL exhaust from header back then YES you may only want a 2.25" exhaust since you're going to control the ENTIRE flow of the exhaust.
Does this make more sense?
Also, someone else said it earlier and it's basic physics: Just like with an intake, you can have 4" piping all the way down the length of the car but if your muffler has a 2" outlet you're only going to flow that 2"s. Your smallest restriction is going to be your biggest inhibitor. I have a header that meets at a 2.5" collector...it then plumbs into a 2.14" stock midpipe...after that it wouldn't matter how big my catback was....I'm NEVER going to flow anymore air than that 2.14" mid-pipe.
If you are designing a FULL exhaust from header back then YES you may only want a 2.25" exhaust since you're going to control the ENTIRE flow of the exhaust.
Does this make more sense?
September-9th-2004, 10:29 AM
#19
Guest
Posts: n/a
Original poted by Roddimus Prime
"in all actuality GNO is correct. Backpressure does NOT equal torque. PROPER exhaust gas flow promotes scavaging which promotes torque"
I never stated diferent, I number 1, I stated backpressure DOESNT CREATE TORQ, yes proper exhaust gas flow promotes scavaging which promotes torque, but increasing the pipe diameter by that .5 WILL NOT CREATE IMPROPER exhaust gas flow, (only if exadurated there will be a adverse afect ) so the coment is pointless.
I comented that If full pluming go 2.5 (and I still DO state go for 2.5), and thats ofcoarse from headers out, and if you plan to Turbo the car I sugest 3 inch all the way., As for the other coment
"Also, someone else said it earlier and it's basic physics: Just like with an intake, you can have 4" piping all the way down the length of the car but if your muffler has a 2" outlet you're only going to flow that 2"s. Your smallest restriction is going to be your biggest inhibitor. I have a header that meets at a 2.5" collector...it then plumbs into a 2.14" stock midpipe...after that it wouldn't matter how big my catback was....I'm NEVER going to flow anymore air than that 2.14" mid-pipe.
"
It was ME THAT SAID THAT!
So your telling me Im wrong on details I never disputed, verry interesting.
Anyways we can sit here and argue all we want, but know this Turbo mag has a MS protege (with the tiny turbo and they instaled 3 inch piping from the Downpipe back, and got 22.1 added HP, so argue all you want, but Dems de breaks, a tiny tiny stock turbo with 3 inch pipes will give 22 extra HP Think about that and the mods you plan to do, but if you plan to do anything real you have my sugestion
"in all actuality GNO is correct. Backpressure does NOT equal torque. PROPER exhaust gas flow promotes scavaging which promotes torque"
I never stated diferent, I number 1, I stated backpressure DOESNT CREATE TORQ, yes proper exhaust gas flow promotes scavaging which promotes torque, but increasing the pipe diameter by that .5 WILL NOT CREATE IMPROPER exhaust gas flow, (only if exadurated there will be a adverse afect ) so the coment is pointless.
I comented that If full pluming go 2.5 (and I still DO state go for 2.5), and thats ofcoarse from headers out, and if you plan to Turbo the car I sugest 3 inch all the way., As for the other coment
"Also, someone else said it earlier and it's basic physics: Just like with an intake, you can have 4" piping all the way down the length of the car but if your muffler has a 2" outlet you're only going to flow that 2"s. Your smallest restriction is going to be your biggest inhibitor. I have a header that meets at a 2.5" collector...it then plumbs into a 2.14" stock midpipe...after that it wouldn't matter how big my catback was....I'm NEVER going to flow anymore air than that 2.14" mid-pipe.
"
It was ME THAT SAID THAT!
So your telling me Im wrong on details I never disputed, verry interesting.
Anyways we can sit here and argue all we want, but know this Turbo mag has a MS protege (with the tiny turbo and they instaled 3 inch piping from the Downpipe back, and got 22.1 added HP, so argue all you want, but Dems de breaks, a tiny tiny stock turbo with 3 inch pipes will give 22 extra HP Think about that and the mods you plan to do, but if you plan to do anything real you have my sugestion
September-9th-2004, 12:04 PM
#20
The man behind the mask
Join Date: Oct 2003
Location: Birmingham, AL
Posts: 11,572
ooosir, firstly shut up with your attitude. No'one said you were wrong about anything. I only said GNO was right....and he is.
secondly, english must not be your first language so I'll let the horrible use of grammar and spelling slide but you need to pay more carefull attention to the way people word things.
lastly, If you honestly believe adding a 3" exhaust to a MSP will add 22whp then you are insane. They added a fuill exhaust, intake, front mount intercooler, etc and got 22whp increase. Ithink they even got 12whp from the intake if I remember correctly.
Turbo's do want as free a flowing exhaust as possible but even if you remove the entire exhaus from the cast exhaust housing and run nothing you wont get 22whp. I hate to burst your bubble. Don't be a "bench racer".
p.s. no'one here gives anyone a hard time so the attitude is not needed nor welcome.
secondly, english must not be your first language so I'll let the horrible use of grammar and spelling slide but you need to pay more carefull attention to the way people word things.
lastly, If you honestly believe adding a 3" exhaust to a MSP will add 22whp then you are insane. They added a fuill exhaust, intake, front mount intercooler, etc and got 22whp increase. Ithink they even got 12whp from the intake if I remember correctly.
Turbo's do want as free a flowing exhaust as possible but even if you remove the entire exhaus from the cast exhaust housing and run nothing you wont get 22whp. I hate to burst your bubble. Don't be a "bench racer".
p.s. no'one here gives anyone a hard time so the attitude is not needed nor welcome.
September-9th-2004, 01:31 PM
#21
Guest
Posts: n/a
Listen up In reguards to Turbo mad they got the 22 from the piping and also got 12 from the intake and FMIC, but , the hp level was below what the manafactuer braged (somewheres around 158whp) and they brought it up with the intake reflash of the ECU, and FMIC, and only then did they add the exaust and got 22 HP, you want to get fresh over a simple argument I was trying to be nice and argue my point of vue, go check there site they will confirm it,. SO keep your 2.25 and eat my exaust fumes PUNK!
FROM MACDADDYSLOMO: consider yourself censored and warned...your foul mouth will not be tolerated
FROM MACDADDYSLOMO: consider yourself censored and warned...your foul mouth will not be tolerated
Last edited by macdaddyslomo; September-9th-2004 at 11:49 PM.
September-9th-2004, 09:43 PM
#25
Registered User
Join Date: Aug 2004
Location: Huntsville, Al
Posts: 119
Dang!
Cous! All of that language was not called for! you must not know who you were talking to! You off da chains homeboy! It seems that someone needs some *****! Roddimus did not try to start a fight, you lost your cool get it together. All in all, if the exhaust is too big it will cause turbulence which disturbs exhaust flow and slows down the pace of exiting gas. And when that happens the effect that is looked for has been defeated. So that is why he said keep it 2.25 because if we can all take a minute to recap, the man who started this thread said that he did not want to go turbo in the furture. So keep it real and lets try not 
to belch all we know in one sentence. Which we found out was not too much.
to belch all we know in one sentence. Which we found out was not too much.
September-9th-2004, 10:21 PM
#26
Registered User
Join Date: Jul 2004
Location: Austin, Tx
Posts: 1,099
Well I didn't get the thumb that rodimus posted but DUDE! Thats messed up, your showing your self and it don't look cool!
As far as the size, I just sold my truck and I could us the same advice, I need a good cai, header, and a good size exhaust. I will be doing nos if I have enough left over.
I am learning a lot about these 4 bangers from you guys. But I spent 9yrs in the military and I don't need a lesson on being a potty mouth!
So any good critisium (Yea I know I cant spell, I don't need to I learned how to kill instead LOL)would be nice.
As far as the size, I just sold my truck and I could us the same advice, I need a good cai, header, and a good size exhaust. I will be doing nos if I have enough left over.
I am learning a lot about these 4 bangers from you guys. But I spent 9yrs in the military and I don't need a lesson on being a potty mouth!
So any good critisium (Yea I know I cant spell, I don't need to I learned how to kill instead LOL)would be nice.
September-9th-2004, 11:44 PM
#28
Moderator/ Pocket Tuner
Join Date: Apr 2002
Location: Tampa,Fl
Posts: 4,150
Originally Posted by GNO
Backpressure will not help with torque, however, exhaust velocity will. Exhaust velocity contributes to the scavenging effects, which in turn assists in torque output. Volumetric flowrate is a function of velocity and cross-sectional area. Given a fixed volumetric flowrate, an increase in cross-sectional area will yield a decrease in velocity.
If tuned accordingly, HP and volumetric flowrate are directly proportional. However, in street applications peak HP shouldn’t be as much of a concern as what is under the torque curve.
Once again, it all boils down to how far you plan on taking the vehicle. The difference will be minute, so if there’s a good chance that you’ll be building it up with higher compression or forced induction, then go with 2.5”. If you plan on racing regularly and will be spending a lot of time in the upper rev range, then again 2.5” would be better. However, you’ve already stated that FI is not in the plan and it doesn’t sound like you’ll be using the vehicle as a full-time racecar, so I will continue to recommend 2.25”.
If tuned accordingly, HP and volumetric flowrate are directly proportional. However, in street applications peak HP shouldn’t be as much of a concern as what is under the torque curve.
Once again, it all boils down to how far you plan on taking the vehicle. The difference will be minute, so if there’s a good chance that you’ll be building it up with higher compression or forced induction, then go with 2.5”. If you plan on racing regularly and will be spending a lot of time in the upper rev range, then again 2.5” would be better. However, you’ve already stated that FI is not in the plan and it doesn’t sound like you’ll be using the vehicle as a full-time racecar, so I will continue to recommend 2.25”.
GNo you rock....thought I'd have to do the stupid backpressure is not beneficial arguement...but you've got it handled quite nicely! Give him a cookie!!
explanation of the pic...band = banned...as in gone from the site
Last edited by macdaddyslomo; September-9th-2004 at 11:51 PM.
September-10th-2004, 12:08 AM
#29
The man behind the mask
Join Date: Oct 2003
Location: Birmingham, AL
Posts: 11,572
He's gone, I left the post up for those who may have thought I jumped to conclusions on that guy. My first post to him was a stern warning which he didn't want to take seriously. I love this forum and it's friendly helpfull members. Let's all keep it that way.
Back on topic. Hughes, I reccomend the Ebay CAI, Obx 4-1 header and catback of your choice. If you're planning on using N20 start a seperate thread about it when you're ready. I have good advice for you and even a nice dry kit for sale if you're interested.
Back on topic. Hughes, I reccomend the Ebay CAI, Obx 4-1 header and catback of your choice. If you're planning on using N20 start a seperate thread about it when you're ready. I have good advice for you and even a nice dry kit for sale if you're interested.