2.5 or 3 inch exhaust - Ford Forums

04-19-2002, 12:47

What's the difference between a 2.5 and 3 inch exhaust system? A majority of EA owners around here have 2.5 inch exhaust systems and I am curious to as why.

How much power do you gain from a 2.5 inch exhaust? Is there extractors and the cat to go with the new exhaust? What is the approx price for the whole set?

Bass Crazy · 04-19-2002, 21:54

Howdie Phil.

The larger the exhaust system, the more flow it will produce, resulting in a reduced amount of backpressure to the engine.

Common belief is that the 2.5" is suited to the EA for a balance between backpressure and flow.

Increased flow will generally help out at high rpm, but the reduction in backpressure means you loose power down low.
Noise is also an issue with bigger exhausts.

You can buy a complete exhaust system, including extractors, cat, muffs, and 2.5� from anywhere between $700-$1200.

On a standard engine, there will probably be about a 10-20kW gain from standard, obviously depending on the individual engine.

04-19-2002, 21:58

gheez 10-20w gain for 700 or so $$$ is that really worth it..

Bass Crazy · 04-19-2002, 22:04

The performance exhaust will help to achieve maximum performance out of other modifications to the engine, such as head work, performance cams etc.

Deciding on wheather it's worth it or not is entirely up to the person who is going to foot the bill, and drive the car.

04-20-2002, 14:13

Hey Bass

What is it really when someone converts a CFI 3.9L to a MPFI... I really don't understand it but then again, I guess that's about the standard performance modification done to EA engines.

I'll consider the 2.5 inch exhaust along with the complete system, cat, extractors etc... I'll consult with my insurance company to see about 2.5/3 inch exhausts.

EB2Ghia · 04-22-2002, 18:09

I have a 2.5 exhaust to a 3ich tailpipe over the diff. thsi is louder than legal, differant cars have differant emmision laws, for a ea or eb ed i think 2.5 with one muffler is still legal, 3 is not but i dont care cause it still isnt that loud.

ea_39_s · 10-20-2003, 05:03

bass, how much gain do you get from the 2.5 inch pipe and muffler alone? i bought that system the other day for 400 i noticed the difference straight away especially low down the rpm range would it be 3-5kw for just the system from the cat to the tip?

ea_39_s · 10-20-2003, 05:06

and a quick one for you mick, how are you going? and when did you get the coupe? we should have an ACT / NSW meet soon in civic or regatta point soon i gotta meet all of these new ACT E series people, maybe their veterans now since i've been away for ages heh

xtream ea · 10-21-2003, 07:35

my ea already has a 2.5" exhust, i'm pritty shore stock, and i'm planning to get a better exhust set up, how much would it cost for a howl new exhust set up that can give my car a fue more kw

Axeman82 · 10-21-2003, 17:58

The biggest problem i've heard with 3" exhausts for 6 (unless really worked) is that with the increased size you lose gas velocity which means that due to the increased area for which the exhaust gases flow through, they start to cool down and get heavy, resulting in poor performance.. thats why when idiots go and get 4" systems for their std wrx they are probably going more harm then good cos they lose velocity which affects spooling..

one exhaust place i was helping out at was installing a new system on an el xr8 and he installed 2x2.5" press bent, into a 3" mandrel pipe with a single straight through muffler. when I asked him why not put on mandrel 2.5" pipes he said that when combining the total volume for flow it was too large for the std engine and would hinder performance due to lower gas velocity..

there's lots of articles about it on the net if you look around..

go 2.5"...

i only have a stock 3.9L cfi and i'm thinking about going straight through 2.25"...

Dan..