2.25" or 2.5"?

[Downfall]

i am going to be getting my exhaust system done very soon and i wanted to know what pipe diameter would be better. i have a l26 engine with the 71 SU's in my 71 240Z. it has headers on it and i plan to get the exhaust system done from the headers back. i've heard from many people to go 2.5" but the collector at my headers doesn't even seem that big. it seems 2.25" and the mechanic that is going to do the exhaust system for me says that it's not that good to go 2.5" as i will lose the low end torque. i already know that but don't you gain more in HP with 2.5" over 2.25"? the mechanic also told me it's not good to go bigger than the collector pipe.

any suggestions?

[ZmeFly]

for the Z have at least a 2.5 inch collector. if your engine and the like are mostly stock then i wouldnt go above 2.25, if you have a little more then stock or are planning to go further then by all means get the 2.5

i ran my wrecked 72 just off of headers alone and i dont know what hes talking about losing low end torque. i could rip and run that car all day long:devious:

[beandip]

with a stock L-26 block stick with 21/4 the largest . It is true you will give up low end with the bigger pipe. Now if you did some head work and cam and maby triples then you could benifit with the larger 2.5. I am running a 280 with a milled head and street cam and electronic ignition, headers and a 21/5 exhaust and wish I had the 21/4 . I dont run on the track and on the street I dont push the Rs close to red line and so the low end is where I want the power band. :classic: my 2c

[texasz]

So if you go with a pipe that is too big you will loose power on the low end?

So it sounds like 2.25 is the best size to go with unless you have a fairly modified engine.

[kmack]

A large diameter pipe gives better breathing at higher rpm's, therefore giving better power in the upper rev range. The tradeoff is you loose some of your low-end response. Not so much loosing power, just some of the quickness off idle.

If you have a basically stock motor (L24,L26, and even a stock L28) then you should really stick with 2-1/4" system. The 2-1/2" system will resonate really bad and with a stock motor, you won't notice any difference in performance.

Now if you have a ported/polished, shaved head, wild cam, triples, etc. L28, then by all means use the 2-1/2" system. You'll love it!

[PrOxLaMuS©]

by means of modded engine...

if I have an all stock engine... would adding on headers change anything?

I was thinking of getting a set of coated MSA headers, with 2.25" exhaust.

With the headers would the 2.25" be ideal, or would 2.5" be better for all around performance?

[zed240au]

with a mild 260 motor i would go with the 2.25 thats what i ran on my 260 motor and it went real sweet sounded great too

Mick

[kmack]

With the headers would the 2.25" be ideal, or would 2.5" be better for all around performance?

If you're planning to stay with essentially a stock motor, then go with the 2.25" pipe. There will be less resonance.

As for the headers, I'd still get them. There won't be a big noticable increase in power, but it will help the breathing of the engine.