RB down pipe for HKS manifold & external gate?

[mello88]

I know a few of you guys currently run (or have ran) the HKS bottom mount manifold with external wastegate. I'd like to see pictures of your down pipe or DP design if possible? Looked around briefly and didn't find anything in this regard.. Did HKS make an RB specific down pipe to mate with their manifold, wg and turbo (probably wouldn't clear on LHD but it would be nice to reference)?

I imagine the pipe will end up looking something similar to this (see pic), although I haven't measured anything yet.. I don't have the skills or equipment to fabricate this so the actual cutting/measuring/welding will be "outsourced", although I have some idea how I'd like it to turn out... Your criticism, links, measurements or suggestions are appreciated.

[SeVa-S13]

Simple custom donwpipe and a long screamer pipe will be it for me, pretty sure carl runs a screamer too.

[mello88]

Thanks for the response! I wouldn't run a screamer on my ride, although they are pretty cool

Do you have any pictures of your DP off the vehicle?

[Yellow4g63]

I know a shop that could knock out that downpipe for you but there pretty busy right now. How soon do you need it?

[mello88]

I already have a local shop lined up to do the fabrication (Xtreme Metal Works), I just wanted to see what the other guys with the HKS manifold are running. My requirements are pretty simple; a 3" cat flange with flex sections on the WG dump and the main pipe itself. I think it would just make it a little easier if I had something to show these guys, I'll take them that quick image if nothing else..

Anyone know if HKS made a downpipe to match up to this manifold? I've never seen it if so...

[Bluefire]

Any competent fabricator can make the dump pipe without having to see a picture. The only thing they would need to know is that you want the flexpipes and where they should put it. Also make sure you use quality flex pipes... a lot of the crappier ones out there will restrict flow...

-bluefire

[mello88]

Good to know. Thanks for the response

How do they restrict flow, rough inside edges??

[Sil240]

Thinking about it.You only need one Flex pipe, because the WG and the turbo are bolted to the Manifold.The manifold is bolted to the engine.It is all going to move as ONE unit.

So you should just need that one Flex pipe.

Plus I would put the O2 bung before the flexpipe in case it does go it wont mess with your 02 readings.

Don't know about the one your getting but the stock one on my Altima broke and the weave is missing on one part and the pipe looks like an Accordion.

[Bronze MFP]

do you even need a flex pipe? stock it doesnt have one.

[Sil240]

Unless your using solid motor mounts I would use one. You do realize that when you hit the gas the motor does move.

I never took the heat sheilding off the stock DP I just threw it out.

[mello88]

Sil240, the flex sections do two things, one like you say is to prevent damage from vibration & twisting like bottoming out the exhaust or the motor rocking during acceleration. This is the reason I want the flex on the main pipe (of course). But the flex sections also allow for thermal expansion, which apparently is an issue for the external waste gate dump pipe. The small dump pipe stays relatively cool while the gate is closed, but heats up rapidly as the gate opens. This causes the pipe to expand, and after enough cycles it may lead to a cracked weld at the dump pipe junction (expansion/contraction stresses the weld I guess). At least thats what just about every article I've read tells me.

Just pricing out the pipe, reducer, flanges, flex tubes and estimating labor I expect this dump to be fairly expensive anyways, so I don't mind spending the extra $50 or $100 to have the flex sections if it helps reduce the chance of destroying the part because I didn't use them.

O2 bung can go anywhere I guess; I was thinking it might see better readings a little further downstream where the gasses aren't as turbulent?... But I'll keep your suggestion in mind!

Yeah from what I see the flex sections are that flexible accordian tubing just wrapped with some kind of woven steel mesh. Still not sure what makes one flex section "better" or higher quality than another though?

Thanks for the input guys!
Modified by mello88 at 2:26 PM 3/14/2007

[Yellow4g63]

Point A in your pic should be a Vband clamp on that thing. screw bolts.

[mello88]

I got a decent deal on a T3/T04E but it has the 5 bolt dump and I don't intend on replacing the turbine housing. Do you like the VBand setup because it's easier to get the pipe on/off -- or does it provide superior sealing?

What do you think of these things:



I suppose that would make getting the pipe on/off easier, but it doesn't really solve the gasket/bolt/sealing issue.

[JerryRigRB240]

The thermal expansion and stress on the welds is only really seen on extremely high hp cars. This means ~40lbs of boost. Also the thermal cycles are seen at a much greater extent in drag motors than street driven ones. Basically for a street driven (even if you go to the track all the time) vehicle you will almost never have to worry about thermal stress on the weld causing failure, unless you have it welded by an incompetant welder.

Also I'd like to point out that if you're saying the flex tube causes less heat to reach the pipe past it, then you're saying that the gas is losing thermal efficiency. Loss in thermal efficiency at that point would cause the gas to slow down and flow would be inhibited.

If I were you I would design it for the best power you can get, not the off chance a weld might crack.

[Yellow4g63]

I got a decent deal on a T3/T04E but it has the 5 bolt dump and I don't intend on replacing the turbine housing. Do you like the VBand setup because it's easier to get the pipe on/off -- or does it provide superior sealing?

What do you think of these things:



I suppose that would make getting the pipe on/off easier, but it doesn't really solve the gasket/bolt/sealing issue.

Thats what I had in mind. You can also turn your own flang into one. It makes life so easy, but it can be a little pain in the *** if your not use to it. and yeah no worries about gaskets there.

[mello88]

Thanks for chiming in JerryRig; Are there other downsides to running those flex sections I'm missing? Aside from the minor increase in cost, or the potential for leak (?), or added turbulence(?)? They seem like cheap insurance but maybe I'm missing something.

[JerryRigRB240]

If you get a quality one I don't think leaking will be a problem. They do however cause turbulance, which is probably why you'll want to put it as close to the cat. as possible.

[Yellow4g63]

You might not need it but what the hell, the motor tq's left to right and if you bottom out you won't really farq stuff up. You won't need one on the dump tube tho. The fabricator dose it right you won't need one.

http://www.3rdgearvtec.net/And...).JPGh ... nd...).JPG

[Bluefire]

Good to know. Thanks for the response

How do they restrict flow, rough inside edges??

i wish i had a picture on hand, but I was shown 3 flexpipes of varying quality. the lowest being the typical steel mesh on the inside, second one looked like almost rings on the inside(hard to describe) and the best one was nearly smooth inside(cannot possibly describe without showing you a picture)

Also the purpose of the flex pipe on the dump, should really be just for easier removal and installation of the pipe. like others aid thermal expansion is not really in issue hear. Just make sure you use quality ss and hope that they know how to properly weld it.

[integra7]

I made my own v-band conversion and downpipe. The reason I made my own vband conversion instead of buying one is because when you make your own, you can change the angle to fit your application. The main concern with the flex pipe is that most are only partially stainless steel. The 100% stainless steel ones are pricey, those are the ones you want. Same thing goes for the vband flange set (sometimes the flanges are stainless and the clamp is not, look for both stainless flanges and clamp).

As for o2 bungs, you want one relatively close to the turbo (maybe within 6 inches) for the stock o2 sensor. I also added a second o2 bung right before the flex pipe for wideband.

oh yeah, dont be a wuss, run open wastegate, no need to close loop it.

here are some pics: