norcalridin

iTrader: (1)

i was just wondering what the best uppipe is for the money... i was thinking of either going with a helix flex, or a invidia downpipe... either way if i go with either brand, i am going to get a downpipe from the same company..

WindingRoad

iTrader: (15)

can't go wrong with helix up & down setup

andrew12

get a crucial racing up and dp... for real.... do it!!!


chile

TurnWRX

iTrader: (3)

+1 if the poster meant best up/dp for the money (i.e if money is no object).

But their dp is not a full dp so u will need to replace the midpipe.

testes1010

+1 for Crucial...

WRX2ndregime

iTrader: (2)

if you want to save money and have a great up-pipe with excellent fitment, STI uppy. People sell them on here for less then 100 bucks all the time. I have the helix, but I kind of wish I had the STI.

fastnoypi

to a certain extent, brands dont mean anything to me...the best upipe criteria to look for is one that has the same interior diameter as the end of where the uppipe connects to from the merge of the collectors.
A wider diameter will cool exhaust to an extent and slow down exhaust flow to your turbo. Unfortunately only TXS is the only aftermarket manufacturer that has one in cast iron that I know of. I hear mixed reviews in terms of fit, but it has the best thermodynamic properties. An alternative of course is to get one jet hot coated and thermal wrapped.
Also, look for an uppipe with thick flanges, they hold better and are less prone to crack at the welds if they do not have a flex section.

VIBEELEVEN

iTrader: (2)

I have the helix and I love it, I would never buy a non'flex uppipe! as for the crucial... it is ceramic coated, who cares but it's not a flex design that I know of, If you can find an sti up get it, it looks stock and if you resister the egt sensor and tuck it away, nobody will ever know

TurnWRX

iTrader: (3)

CRS pipes are thermal coated which helps keep the heat down in the engine bay.

meilers

I think the Crucial pipe is overhyped (no flex is a problem, unless you have upgraded motor mounts or only drive on asphalt) and the Helix is pretty thin; you want more mass to hold in heat.

Let's do a comparison. Here's the Crucial pipe:



Note the flat ends, sharp edges, lack of taper and no flex.

Here's the Helix:



No coating, flex looks like a basket but again sharp edges and a narrow inlet.

Now, if price is not the issue, there is the APS model. It is easily $125 more than any other pipe out there (I've seen it selling for $325.00) but it is the only pipe I have seen that has the slightest sign of engineering behind it. Check it out:



Note how it is two sections, one cast-iron to trap heat, the other stainless steel which has more flex. The cast-iron section has a very subtle taper to it which is designed to prevent vortexes when you get vaccuum instead of pressure (while shifting). Also note the wide openings and the bevels on the edges, and the very thick plates. Expensive, but this is the Lexus of turbo inlet pipes (the real name for up-pipe).

DomozitoLK

iTrader: (20)

On a similar topic...anyone know if uppipes all have similar diameter tubes? Someone brought it to my attention that some might have bigger tubes and flow better than others. Is this true?

Here is my Bosal uppipe I bought. It's got a factory look, much like the STI. I got it for $159 brand new.

Thanks!

Rob

meilers

You have to love blanket statements with no evidence or numbers to back them up.

In response to DomozitoLK, all up-pipes have a similar inlet and outlet diameter (though some taper internally, like the APS pipe) for three reasons: one, the size of the exhaust port on the engine block isn't going to change; two, Subarus tend to use VF-series turbos and you need to be compatible with the hot-side turbine gasket and fitting; and three, on the inlet side, gas pressure and retained heat is more important than actual flow. You WANT as much pressure as possible on the turbine side, and as little pressure as possible on the exhust side, in order to create a pressure differential and cause the exhaust gases to be "pulled" through the turbine as quickly as possible. When the diameter of a pipe changes, the speed of the gases in the pipe slows down (the same happens with water -- try comparing a large-bore hose to a small-bore hose with an equal flow of water), and it is the speed of the gas (as well as the heat) which imparts force to the turbine. This is why the APS pipe actually narrows in diameter as it approaches the turbo, to increase pressure and velocity.

testes1010

i agree 100%...

for the comment made 'no flex section being a problem' on the Crucial uppipe

the flex section is not needed on an uppipe if the uppipe is designed properly which the Crucial piece is as well as many others PDE, helix, etc.....the flex section will only add turbulence to the exhaust flow, slowing spool...

as far as i know there has been no fitment issues w/ the crucial uppipe....

for the money spent on any uppipe, it should be designed properly....otherwise you might has well just gut the stocker & save yourself some cash....

rex nfx

^^I agree

Why would you want a flew section in an uppipe? The stock one obviously doesn't have a flex setion in it...the entire engine, manifold, uppipe and turbo assembly move as a complete unit. There is nothing that needs to flex until you get to the rest of the exhaust that is tethered to the car's chassis in some way (brackets, hangers).

Companies add the flex section to help n00bs install it because they don't know the proper way of doing it in the first place to ensure Zero leaks.

The crucial pipe is the same diameter as the turbo inlet therefore there is no need for it taper. A taper or larger pipe will only increase turbulence when it enters the exhaust housing of the turbo.

The flanges are surface ground after they are welded to the pipe to ensure a flat surface in case they happened to warp.

As for the ceramic coating...if you aren't aware of the benefits of maintaining exhaust gas velocity and shielding cylinder number three from heat, then you should sell your WRX and buy a Honda...

mbquarts

iTrader: (10)

Incorrect. The stock uppipe does have a flex section. The flex section is not for movement it is for heat expansion. The exhaust manifold and uppipe will expand when in use. The flex section will flex when the uppipe gets hot in order to prevent the welds from cracking or the flanges from warping.

WRX Rush

iTrader: (7)

I have the STi Up-pipe from Japan, it has the same heatshield as stock, it has the same flex as stock, it has no egt bung.

I have never heard the theory of flex becoming a turbulent for exhaust. I will have to look into that. Even if the flex did add exhaust turbulence, the normal street driver would never feel that difference.

From the issues I have heard about a flex up-pipe is just re-assurance of no exhaust leaks, the no flex up-pipes, I have heard need to be machined, need to be double and sometimes triple gasketted in order for them to work the way they should.

I would say the best up-pipe for the money would either be the STi JDM up-pipe or the bosal, a copy of the JDM.

Cheers,
Austin

subabu05

+1 for STI uppipe.

meilers

As the other posters have pointed out, the STOCK PIPE has a flex joint itself; you just can't see it under the heat shield. Care to revise your statement?


Ah yes, the "buy a Honda" comment -- Study the thermal properties of cast iron vs. steel and get back to us. I think you'll find that a ceramic-coated rolled steel pipe is just about the same as a cast-iron pipe in terms of heat retention and prevention of hot spots.

meilers

The stock WRX and STI pipes both have a flex section, from the factory; I guess Subaru engineers have a few things to learn, according to you? Second, even though the flex is differently-shaped on the outside, the actual tubing diameter inside is consistent and smooth -- the flex is a change in the thickness and walls of the pipe, with a woven "basket" of steel mesh to prevent heat loss; it isn't as rough on the inside as it appears on the outside. See the pic of the APS pipe further up the thread, you can kinda see inside and the "woven steel" look is only on the outside.