vtec69

My mods are ls/vtec with a type-r head fully worked with a jdm type-r header with 2.5in collecter carsound 2.5in cat, crower 403 racing cams, and ctr pistons.

Should i get 2.5inch exhaust or 2.25 exhaust??

vtec69

ttt

R-Rated

2.5"

vtec69

any other comments with explantions

garados

iTrader: (3)

I would get the 2.5 inch exhaust beacuse everything else is 2.5 inches. Also, I sounds like you'll be all out racing, so the 2.5 would be less restrictive and makes more top end power. the 2.25 would be good on a mildy worked on engine (i/e/h) because it would make good top end power(not as good as 2.5 inch) and some low and mid-range torque. I have a 2.5 inch and it pulls hard from 5000-8100. I would have gotten the 2.25, but I have bigger and better plans for my car ^_^ Hope that helps.

EagleR

You seem to be modding seriously enough to warrant 2.5.....you'll like the top end.

Big Teggie

Get a 2.5 inch mandrel bent system.

Anyotherone

Who makes a 2.5" exhaust. Also, I've heard that the JDM DC 4-1 (2.5" collector) is the biggest bang for the buck when it comes to a header, is that true?

Thanks.

tonydatyga

If your collector is a true interior diameter 2.5" then get a matching 2.5" system. The only reason for going w/ a 2.25" would be for exhaust gas scavenging and that's usually not affect as much by the piping after the collector as it is in the header system. Since the collector is 2.5" you don't need the pressure gradient provided by the switch to 2.25" piping at that point in the exhaust system. Hope that made an ounce of sense. Btw, what are the characteristics of your ls/vtec? rev range, powerband, cr from ctr's?

neo1z

the dc jdm 4-1 or the comptech....love the comptech. 4-1 top end with 4-2-1 low end torque. yum.

i beleive thermal has one, isnt the apexi n1 2.5 as well?

Fooser

depends on how much power you want to put down as well. 2.5 will be less restrictive. I'm in the same boat. with 2.25" header, cat, and begining of the exhaust. Dont know why Greddy does that but it goes from 2.25 to 2.5 on the cat back.

Soon I'm going to be upgrading my cams and I will more then likely have to upgrade to 2.5" header, cat, and exhaust. Bad planning on my part. If only I knew as much then as I do now.


[Modified by Fooser, 6:43 PM 7/1/2002]

IC x Prince

I think the best bang for your buck would be the DC JDM 4-1...It's only $288 at inlinefour.com

JCushing

any system thats designed to bolt on the the factory exhaust (cat) is gonna be 2.25 at some place even if it opens up to 2.36 at the end (like the evo). this is because the factory cat outlet it 2.25 so if it mates up its 2.25 somewhere. im still looking for an aftermarket exhaust thats minimum 2.5" all the way through. im thinking custom is the only way to go (short of a thermal 3")

Anyotherone

So the N1 isn't 2.5" all the way through?

JCushing

explain to me how it could be if it bolts to your factory cat... for instance thermal gives instructions with there 3" systems that it doesnt bolt up and you need an aftermarket cat or at least an adapter.... i do believe that the n1 muffler itself however is 2.5" and most of the piping is to but it still has a bottleneck at the cat.... it is possible to weld in a new 2.5" peice with a 2.5" cat too

Anyotherone

Makes sense to me...

GSRGuy17

I got a quick question. I have axle back with 2.25" I believe. When I go to the muffler shop to get the rest of the piping (too cheap to buy a cat-back), what do I tell him? Replace everything up to the cat? Would that make it a "cat back" system? And, how much would a hi-flow cat.

Fooser

I suggest if your going to be upgrading your cams or going FI just redo the entire exhaust system from the headers back to 2.5" all the way through. That what I would of done if I had to decide again. Dont skimp out by just upgrading your exhaust from the cat back either because you will have to replace it eventually.

RedTeg95

I just upgraded to the DC JDM 4-1 and carsound cat last weekend. To my surprise my DC cat back exhaust was only 2 inches!!! So now I'm in a quandry about what to do. I have a Tanabe racing madalion sitting in my garage which I took a look at and it also is 2 inches where it connects to the factory cat then a few inches down the pipe opens to 2.25 inches. I orginaly had that on the car but it was just too loud for my tastes. Can anyone tell me what the diameter of the Apexi WS is?


[Modified by RedTeg95, 10:46 AM 7/5/2002]

Fooser

factory is 2.25" so the DC is at least 2.25 to fit your stock components. Thats the standard size for an aftermarket bolt up application without modifing the size of your cat.

So to answer your question. If the exhaust connects to your stock cat, then its more then likely 2.25. For example my Greddy exhaust. It connects at the cat with a 2.25" opening and then gets bigger down the piping to about 2.5". This dosent really help me since there is a point in the exhaust that is 2.25".

RedTeg95

This is what I thought as well. I guess I just measured it wrong.

StyleTEG

Factory is actually 2" unless you have a TypeR (which is 2.25" after the cat)
What you need is an 2.25" cat, and then have a 2.25" connector welded on.

SMSP sells a connectors which fix the bottleneck. You just have to buy it and have a muffler shop weld it on.

The Apexi WS is a 60mm diamater, with a cambered muffler. It also has the 2" connector flange on the end.


[Modified by StyleTEG, 4:04 PM 7/5/2002]