Someone said I lose torque by decreasing backpressure, is this true? You would think the less backpressure the more torque but then again i’m stupid. Someone plz explain this 1 to me cuz i was thinkin bout getting a 4-1 header over a 4-2-1… If the piston coming up has to work harder to push the gasses out, the piston on its down stroke has to work harder to push it up which seems like it would suck power. Oh well peace
First get a 4-2-1 header it will flow better the a 4-1.
Now unless your running a turbo then keep the pipe size under 2.5" even that is a bit big and some say 2.25" is best for N/A. You need some back pressure in your exhaust but not to much because it will affect preformance.
Ok here’s the way I understand this
You want as little back pressure as possible.
But bigger is not always better if you use to big of a pipe you slow down exhaust gas exiting speed.
The ideal way for an exhaust to work is for exhaust gasses already exiting to create a vacume and pull gasses that are behind out instead of being pushed out taking greater force from the motor to expell exhaust gasses.
So what size pipeing you use depends on what you are doing.
N/A 2.5in or so F/I or N2O 3in
I bag to differ with you on using 3" piping for N2O. I think unless your car is force fed then you should have between 2.25" and 2.5" piping
You do not need back pressure in any setup.This is an old wives tale. If you use an exhaust system that is too big for your setup you will lose power but it has nothing to do with backpressure.
If you needed backpressure then you would not remove the stock exhaust manifold to install a header.
The G2 Racer to use N2O to the fullest adv. you would need a bigger exhaust system. Whae you were not useing the bottle then it would loss some N/A performance. If you don’t upgrade the exhaust for N2O then the car will have more power when you are driving around town but when you spray you will not get the most power from the N2O. Its a trade off for what is more important to you.
Hey NC-B17A,
You are correct backpressure and the efficiency of an exhaust system is an old wives tale. The less backpressure the more effective your exhaust system can be, but what you do need is exhaust gas velocity for a NA engine. If you utilise too large a diameter of an exhaust system pipe you loose exhaust gas velocity, it’s scavenging properties, it’s ability to draw following exhaust out of the combustion chamber.
I don’t know if it is a wives tale or not, but i’ve driven my car strait off of the header before and the low RPM power is totally gone. I’ve driven it strait off of the engine too. hehe. I guess that scavenging effect- of the previous exhaust pulse does help pull the next one along.
Originally posted by NC-B17A
You do not need back pressure in any setup.This is an old wives tale. If you use an exhaust system that is too big for your setup you will lose power but it has nothing to do with backpressure.
If you needed backpressure then you would not remove the stock exhaust manifold to install a header.
The G2 Racer to use N2O to the fullest adv. you would need a bigger exhaust system. Whae you were not useing the bottle then it would loss some N/A performance. If you don’t upgrade the exhaust for N2O then the car will have more power when you are driving around town but when you spray you will not get the most power from the N2O. Its a trade off for what is more important to you.
To achiev e faster velocity you must compress the gas which puts a strain on the piston. I see some fo you are trying to say but it doesnt make much sense. You’re tellin me you need to get the gas moving fast so it will ‘suck’ exhaust gas out of the engine thus relieving the engine of pushing it out. But when you pull it out, it slows down its velocity which means the piston will hafta push some more on the next stroke to get the speed back up. And once you go fast enough, i’m pretty sure theres enough vacuum (caused by passing air) to suck out the gas (more so than a smaller pipe due to its larger surface area).
Originally posted by DB2-R81
[B]Hey NC-B17A,
You are correct backpressure and the efficiency of an exhaust system is an old wives tale. The less backpressure the more effective your exhaust system can be, but what you do need is exhaust gas velocity for a NA engine. If you utilise too large a diameter of an exhaust system pipe you loose exhaust gas velocity, it’s scavenging properties, it’s ability to draw following exhaust out of the combustion chamber. [/B]
He’s right. This guy knows his stuff. I had to go get my Nov 2001 SCC and it said pretty much exactly what he said. So no more fighting, take this as truth. BTW there is a good article in Nov '01 SCC on how to build your own exhaust.
Ben
Oh yeah and their pipe dia. guidelines are as follows:
1.5 - 2.0 L = 2 inch
2.1 - 2.5 L = 2.25 inch
2.6 - 3.0 L = 2.5 inch
These are for N/A. Add .5 inch for n2o optimized. And no smaller than 2.5" for turbo.
Ben
Originally posted by Ben Ogle
[B]Oh yeah and their pipe dia. guidelines are as follows:
1.5 - 2.0 L = 2 inch
2.1 - 2.5 L = 2.25 inch
2.6 - 3.0 L = 2.5 inch
These are for N/A. Add .5 inch for n2o optimized. And no smaller than 2.5" for turbo.
Ben [/B]
Umm dont our cars have 2.25"? I’m pretty sure my engine isnt a 2.1L 
and i thought the itr had 2.5?
Originally posted by SlprTeg
[B]
Umm dont our cars have 2.25"? I’m pretty sure my engine isnt a 2.1L and i thought the itr had 2.5? [/B]
ITR with a 2.5L ROTFLMAO Please it has a 1.8L like all ther other G3s.
Originally posted by The G2 Racer
[B]
ITR with a 2.5L ROTFLMAO Please it has a 1.8L like all ther other G3s. [/B]
I kno it has a 2.5" sumthin… collector maybe? flange? i heard 2.5 and type-r in the same sentence sumwhere 
Ok so everybody agree that if you use too big of an exhaust it is bad for what ever reason you want to think?
Umm dont our cars have 2.25"? I’m pretty sure my engine isnt a 2.1L and i thought the itr had 2.5?
:roll:
Originally posted by NC-B17A
[B]Ok so everybody agree that if you use too big of an exhaust it is bad for what ever reason you want to think?
:roll: [/B]
Lets not make fun of me, i kno the ITR has a 2.5" sumthin 
Assumed it was exhaust
I agree with the general concensus on this thread, but i believe its dependant on engine speed. The smaller exhaust dia is better for keeping the velocity up at low rpm speeds and the larger dia for the higher speeds. That’s why there has often been complaints about the sacrificing of “low end torque” in favour of high end hp in popping free-er flowing exhausts on. That’s why Stromung told me they made their cat back piping only 2" for my car; perhaps a compromise between both worlds.
Its the same deal as with head ports, IM runners, valve lift and duration…
that’s why we need vtec exhausts hehe. At 4500rpms the tube dia. widens .25" and away we go. Woldn’t that be nice
d
I’m sorry SlprTeg. You gave me the first chance to use one of the little faces.
Originally posted by SlprTeg
[B]
I kno it has a 2.5" sumthin… collector maybe? flange? i heard 2.5 and type-r in the same sentence sumwhere [/B]
Yes the JDM Type R header has a 2.5 collector. But you wrote 2.5L The Type R engine is not a 2.5L engine. Honda does not make an engine that big. I believe there biggest engine is the 2.2L H22A
I think the V6 in the Accord is bigger than H22
i know this for a fact, i had my pipe after the cat disconnected for a few days, the cat was still hooked, the car would accerate slower but it would max out at about 10 mph more, i guess cuz there was no waiting time for the exhaust gases to get out, but off the line it blew