another post to add to the myriad of exhaust questions

[chmercer]

this is about backpressure (sort of) and i know there are many many posts on this but i still wanted to ask my specific question, as none of the other posts quite define what im asking.

I want to eventually go turbo (rb25det) but i want to upgrade my exhaust somwhat soon, so i dont want an all motor exhaust and have to go bigger when i get a turbo. I am looking at the greddy power extreme with a gutted junkyard cat or a test pipe (if the fine isnt too high )the piping on this is pretty large; how much would the loss of backpressure effect the cars drivability? any ideas?

if i bought a catback exhaust and a testpipe/gutted cat, would there be any other parts to consider when upgrading an N/A exhaust? and what else would need to be purchased/changed if i got a turbo?

also, can somone explain exactly what is a downpipe? its the pipe that comes off the intake manifold from the turbo right...? (dont flame me if im wrong, im talking out of my *** :p)

[SilviaLuvr]

from what i gathered, besides waiting to get your RB25 don't buy it. sicne your N/A go with simple like A custom pipping or B apexi N1 (don't know the measruments but i believe ther is a 2.5") If you buy a turbo exhaust, first your car is going to sound bad, second, from ehat i believe, you will loose power depening on how built your engine is. I may be wrong on this though.

[krazy skwerel]

dont use a gutted cat if anything use a test pipe but if i were you id wait and buy my exaust when i got my engine since you dont really need it now. just a thought

[lessthanjakejohn]

this is about backpressure (sort of) and i know there are many many posts on this but i still wanted to ask my specific question, as none of the other posts quite define what im asking.

I want to eventually go turbo (rb25det) but i want to upgrade my exhaust somwhat soon, so i dont want an all motor exhaust and have to go bigger when i get a turbo. I am looking at the greddy power extreme with a gutted junkyard cat or a test pipe (if the fine isnt too high )the piping on this is pretty large; how much would the loss of backpressure effect the cars drivability? any ideas?

if i bought a catback exhaust and a testpipe/gutted cat, would there be any other parts to consider when upgrading an N/A exhaust? and what else would need to be purchased/changed if i got a turbo?

also, can somone explain exactly what is a downpipe? its the pipe that comes off the intake manifold from the turbo right...? (dont flame me if im wrong, im talking out of my *** :p)

Your down pipe connects your turbo to your catback exhaust.

A NA engine will flow less air than a turbo one. Therefore you will have less stuff coming out the headers on a NA engine than on a turbo engine. There is like an optimum velocity for exhaust flow out the tailpipe. I larger pipe will flow the same amount of air slower than a smaller one. **If the pipe is too small, there is too much resistance(backpressure) and the air cannot go through at all, Iff the pipe is too large the air doesn't really have any place to go, lollygags around and ends up going slow and causing backpressure**

Therefore a turbo exhaust on a NA motor in fact raises the back pressure, not lowers it. Gas Engines HATE back pressure, dont let anyone tell you that they need it.

**I am not an expert on thermodynamics, don't quote me on that until someone backs me up...

[lessthanjakejohn]

Does anyone know waht that magic airflow velocity should be? you could do some simple calcuations first finding the CFM of the KA at several points and then figuring out the exhaust gas temps and then figuring out the expansion rates of the gas. Then you could take how much gas you have and divide it by the size pipe you have.

[SR Sil80]

from what i gathered, besides waiting to get your RB25 don't buy it. sicne your N/A go with simple like A custom pipping or B apexi N1 (don't know the measruments but i believe ther is a 2.5") If you buy a turbo exhaust, first your car is going to sound bad, second, from ehat i believe, you will loose power depening on how built your engine is. I may be wrong on this though.

the N1 is 75mm-95mm with i think 105mm tip (maybe 115mm) which is like 3in-3.5in w/ a 4in tip (roughly). That sucker is loud on an N/A application haha I had it on mine before I got the SR (still have it) and it was jus so ungodly loud. was about to shell out the $50 for the silencer hehe

[chmercer]

isnt 3 - 3.5 inch piping really big for N/A?

[red240ne]

The downpipe comes off your exhaust manifold and goes to your cat, if you have one.