http://roadraceengineering.com/evo/p...alledatcat.jpg that doens't look like a 2.5 neckdown... in fact i don't know why there is a neckdown there... i think it's a 3inch flange that may not be ti.... now that is really bugging me...

 

trinydex,

Look closer at the picture, it absolutely necks down at the cat.

David Buschur
www.buschurracing.com

p.s. Our downpipe fits perfect, is 3", no reducers and is the lightest out there.

 

but it doesn't neck down to 2.5... it necks down like a millimeter... which is why i ask... why is there even a nenckdown there... and i think the answer is... if it's a 3" flange and the exahust system is 80 mm there is a few mm of difference.

 

i am going w/ the helix dp and test pipe, good reviews, full 3" piping, nice chrome finish and a believe a 2yr warranty, reasonable price.

 

It neck down to fit the stock cat.. what size is the stock cat/exhaust??
If I remember correctly, HKS, JIC and various Japanese based company all told me
around 2.5"...

Reason why I stay away from ALL of them when shopping for catbacks...

 

Helix is indeed 3"... but it does neck down at the downpipe where it connects
to the stock 02 housing... It has to.

 

Stock cat inlet i.d. is 2.45", outlet i.d. is 2.35"

 

but the flange is more or less the same size... and the piping on the greddy is VERY thin... so that outter diameter you see is what you get practically... i guess you guy's gotta see it... i've seen it... didn't notice the neck down thing... look at the pictures of people's installs and ask them... there's no noticeable neckdown.

 

Well if size really the big issue, how about 80MM downpipes.

 

no good... there is no such thing as an 80mm cat... and that's where the cat back hooks up... although if you're running straight pipe that's less of an issue... however i think japan is the only place you find 80mm piping, which is what you'd have to find in order to get an 80mm striaght pipe.

honestly the 2 or 3 mm is not such a big deal... if you're playin' your mods right and you get a 3" dp with a 3" cat and an 80mm catback (which is what lots of people are already running with the greddy ti) you get a straight flow design from the turbo back (assuming you got your o2 housing done) and you get a miniscule expansion after the cat is completely tolerable and will not affect performance in a negative way.

better to go from smaller to bigger... as the gasses will be expanding from the time they exit the engine all the way until they exit the tail pipe. however if you got an 80mm dp and shrunk down to a 3"cat... i can't conceive that as being good although the difference there will prolly be negligible also.

 

The downpipe necks down more than a millimeter, even my eyes aren't good enough to see a millimeter in a picture.

David Buschur
www.buschurracing.com

 

Try look at a Auto Produce Boss or G.P. Sports Cat.

 

Well i guess im going with the vishnu signature series dp with the helix ti catdelete.... and please dont say anytihng bout the ti catdelete pipe cus i have it already and i like the piece. hehe cus people already told me its too expensive and dumb but its all gud!

 

The main diameter is 79.7mm OD

The "smaller" neck down diameter is 77.5mm OD

Mike W

this is email referring to the picture of greddy exhaust on rre's site.

 

evo8silver, we have a 3" mandrel bent 304 SS downpipe that will bolt right up with no reducers or restrictors in it for $275. The catdelete from us is $55 also.

Better check as I heard that Shiv (not trying to start anything and someone correct me if I am wrong) is not longer offering his line of exhaust, he is simply selling the Helix.

David Buschur
www.buschurracing.com