Rb26 Single Turbo Exhaust Manifolds

[CruiseLiner]

so just the mount from the mid part of the gearbox isnt enough to hold it up? its the rubber stock one im talking about.

should the one from the bellhousing be totally solid (no rubber in between??) onto the exhuast and to one of the bellhousing bolts?

i get conflicting stories that bracing it too much will make it crack and others say not enough will crack it.

also where do u reccomend to brace the wastegate too? the engine block or the bellhousing or what?

Edited June 28, 2006 by CruiseLiner

[Sydneykid]

so just the mount from the mid part of the gearbox isnt enough to hold it up? its the rubber stock one im talking about.

should the one from the bellhousing be totally solid (no rubber in between??) onto the exhuast and to one of the bellhousing bolts?

i get conflicting stories that bracing it too much will make it crack and others say not enough will crack it.

also where do u reccomend to brace the wastegate too? the engine block or the bellhousing or what?

The exhaust system has to flex with the twisting on the engine on its rubber engine mounts. The question is where do you want to have that flexing occur? Personally I don’t want the flexing to be on the turbo itself, the wastegate or the manifold that they are bolted to. They are, after all, the most expensive parts of the exhaust system.

So I want the flexing to occur after them. The closest point with nice easy bolts to access is the point at which the engine block bolts to the gearbox bell housing. Then I have flexible joints from that point rewards along the exhaust system. One at the gearbox cross member, one at the front of the rear subframe and the other at the rear of the muffler. This means the weight of the exhaust system is supported by that solid bracket and the other rubber mounts along the length of the exhaust pipe.

It also means that the weight of the turbo and the wastegate are supported by that bracket and the manifold, sharing. Turbos and wastegates are heavy items, the bigger the turbo the more they weigh. This sharing means less weight (load) on the manifold, so it is far less likely to crack.

But (there is always a but) the pipework from the turbo and the wastegate changes length (expands and contracts) with changes in temperature. This has to be allowed for when thinking about the solid bracket work.

Firstly, keeping the distance between the turbo and the solid mount short is important. That means less length (of pipework) for expansion. Another reason for choosing the engine block bolts to the gearbox bell housing, they are about as close as you can get.

Secondly, you need to make sure that the bracket allows the pipework to expand a little when it gets hot. The trick is to make the bracket strong in two dimensions only. What I do is make the bracket out of a flat piece of mild steel, being flat it holds the pipework up and stops it moving side to side. But it also bends slightly as the pipework slowly expands and contracts.

This is the mistake a lot of people make, hence why some people erroneously say not to solid mount the exhaust anywhere. If you make the bracket solid in all 3 dimensions the expansion of the pipework will add to the possibility of cracking the manifold. But even then it is still less than the effect of half of the weight of the exhaust system hanging off the turbo. If you it properly then your manifold, turbo and wastegate will live a long crack free life.

Hope that was of some help

cheers

[madmax670]

Hey guys, I am from the US and I have been looking for a exhaust manifold for my single turbo application on my RB26 - T4 flange.

I have searched through this forum and have found some good threads regarding the topic, but I still would like some recommendations and to just have a general discussion about manifolds.

First of all, what about the ebay manifolds, are there any ones even worth looking at, if you have used one personally, please chime in.

The cast iron versus stainless steel debate rages on and I understand that as long as you support the weight of the turbo, you will not have problems with stainless steel manifolds.

My main point was to get some recommendations when it comes to my manifold, my application will be mainly street, but I will see some track. I am looking for a manifold that is good quality, has good airflow and heat properties, and will not crack on me; some recommendations would be great!

Edited June 29, 2006 by madmax670

[felixy69]

i have a friend who is using an ebay manifold for his RB25 with GT40R turbo and making 470whp

that thing lasted at least 7 months already..and still looks good !

i can't post a pic of his engine bay set up....idun think he wants ppl to know he's running an ebay manifold..

[felixy69]

Most times I see cracked manifolds it is because the whole weight of the exhaust system is hanging off the turbo. So many cars don’t have the solid mounting bracket at the bell housing and the flexible mount at the gearbox cross member. The weight of the entire exhaust hangs of 2 rubber mounts at the rear muffler and the turbine flange at the front. It’s any wonder that the manifold cracks, carrying the weight of the turbo itself and half the exhaust system, swinging around.

If you support the weight of the turbo, the external wastegate (if it has one) and the exhaust system properly, then all the manifold has to do is hold in the exhaust gas. Which doesn’t require huge thicknesses of stainless steel.

If you are concerned with a thin (ish) walled stainless manifold, spend $50 and get a couple of supports welded on from the turbine/manifold flange to the manifold/cylinder head flange. That will stop any flexing in the pipework itself.

cheers

Wow i never have thought about that point....i always thought it cracked because the exhaust gas is too hot...and never thought about the weight..distrubution.

i guess i'll make some custom bracket to hold the turbo when you get me my DAMN RB30 BOTTOM END ..then i can get the engine finished..finaly...

[saliya]

Wow i never have thought about that point....i always thought it cracked because the exhaust gas is too hot...and never thought about the weight..distrubution.

Hi,

So where's your cracked one mounted? Turbo + near gearbox x member + just before rear axle + rear muffler? Or elsewhere?

Regards,

Saliya

[discopotato03]

Felixy69 that a lot of turbo for 470 Hp , LOL I be interested to know where it comes alive rev wise .

G'wan post the pic , I'd like to see it and its T4 flanged manifold .

Cheers A .

[Sydneykid]

First of all, what about the ebay manifolds, are there any ones even worth looking at, if you have used one personally, please chime in.

The cast iron versus stainless steel debate rages on and I understand that as long as you support the weight of the turbo, you will not have problems with stainless steel manifolds.

My main point was to get some recommendations when it comes to my manifold, my application will be mainly street, but I will see some track. I am looking for a manifold that is good quality, has good airflow and heat properties, and will not crack on me; some recommendations would be great!

I always wrap my stainless exhaust manifolds, so no one knows what brand they are anyway. When someone asks, I just say it’s a good one

By wrapping them I achieve less heat transfer (outwards) than a cast manifold. I know that because of the under bonnet temperatures. So I figure if there is less heat getting out, then there must be more heat staying in. Bingo, that gets rid of the cast iron versus stainless argument as far as I am concerned.

No matter what stainless steel exhaust manifold I use, I always clean it up with the die grinder. Plus match it carefully to the exhaust ports. Some take a little longer than others, but I can’t say as I have spent $900 worth of my time making a “cheap” manifold as good as an “expensive” one. So the cheap manifold is always…..well…. cheaper.

No matter what stainless steel exhaust manifold I use, I machine the flanges to make sure that they are perfectly flat. I have found even the “expensive” manifolds are not always flat.

I mount the exhaust system the same as I have described above. If I know the car will have the exhaust manifold red hot for long periods of time, I also brace the turbine flange to the cylinder head flange. I first saw the load carrying bracing on the Gibson Skylines (refer to the pictures in the Group A Skylines thread) and thought it was a good idea. So I have copied the concept ever since. I have never had an exhaust manifold crack on one of my cars, even “cheap” manifolds.

cheers

PS I saw I picture in a post above of a HKS cast iron exhaust manifold that was cracked. They are very tough ,the only way I reckon you could crack one of them would be to swing a big exhaust system off it,

[Gunzla]

As SydneyKid has said, if the design is right and the manifold is supported properly with flex pipes then all the manifold has to do is its job!!! (spooling the turbo, not carrying the weight of the whole exhaust system!)

Anyway, I use a Trust Tuned length stainless Manifold, To4R Turbo, Greddy Wastegate and have had no problems with cracking, more thab likely due to the fact that the dump pipe was designed with flex pipes in it.

[saliya]

PS I saw I picture in a post above of a HKS cast iron exhaust manifold that was cracked. They are very tough ,the only way I reckon you could crack one of them would be to swing a big exhaust system off it,

Hey,

That one was one that I got from QLD. Personally, I can't see what all the fuss is about (in terms of manifold design)

- the design of the HKS cast almost-log-style manifold was certainly not as good as the 6boost one I have; nor the ebay

ones that go for $350.

BUT:

The section that was cracked was just where you'd expect that manifold to crack due to thermal stress - it's just

after where 3 pipes join into 1 that _isn't_ the main collector and it's right in the middle of the manifold - it's most likely

the 'hottest smallest' part of the manifold. The other 3 joined pipes go into the turbo outlet.

Yes, they have a big, heavy cross section that would no doubt be tough - but the location of the cracking means

that I'd be more inclined to say 'from design' rather than 'from a weight hanging off it'.

All conjecture at this stage, I guess I have no idea how that manifold got like it did...

Regards,

Saliya

[CruiseLiner]

i found my trust t78/88 manifold flange onto the turbo was not flat at all and required machining as there was a hump in the middle section and the edges dropped off.

u pay good money and still have to change things

[T04GTR]

steam pipe all the way

im in the process of puting one together myself out of "secret" diametre runners

my aim. 500rpm less lag than my ebay one

[madmax670]

MORE RECOMMENDATIONS!!

[mokompri]

If I know the car will have the exhaust manifold red hot for long periods of time, I also brace the turbine flange to the cylinder head flange.

this is exactly what the SSautochrome (http://www.ssautochrome.com/) manifolds came out with (brace from turbine flange to head flange). SSautochrome were one of the first, if not THE first to come out with the 'cheapy' style ebay manifolds. when they first came out, everyone jumped on the bandwagon and dismissed them as cheap crap that was useless and would crack easily. the first manifold they came out with was for the sr20det.

ive now been running one for almost a year now with no dramas, and its also heat wrapped. there have been 0 reports of SSautochrome manifolds cracking on 2 big silvia forums i frequent. although some of the other cheapy manifolds that are coming out china have had issues, mainly its the ones that have welds on the runners. the SSautochrome ones have a one piece runner design mandrel bent. the collector design is also fairly decent. flange on mine was off by around 1mm off from side to side, a bit of elbow grease with a metal sanding block and it was fine. didnt require machining

i suggest if your looking for a stainless steel manifold to get ones that have a one piece runner design to reduce chances of cracking. also as SK mentioned that brace is a good idea as well, it will stop the manifold from 'drooping' from the weight of whats hanging off it, when its hot.

the 6boost manifolds ive seen look very nice indeed, but they are pricier.

Edited July 5, 2006 by mokompri

[B-Man]

6BOOST for the win !

[discopotato03]

Hmm , any nice picks or links to pics of RB26 type single low mount split pulse T4 flanged manifolds .

Geoff Raicer from Full Race Motorsports was talking about doing them in the US but don't know when .

Cheers A .

[CruiseLiner]

any pics of the exhuast to bellhousing brace sydneykid? i dont get how u can make it expandable one way but not the other ? i know u use flat bar but how do u make it so the manifold can expand outwards from the engine block with a staight peice of bar? or do u have a bend in it?

pics tell a 1000 words for dummies like me

[B-Man]

Some pics of the 6boost manifolds (different types)

[Sydneykid]

any pics of the exhuast to bellhousing brace sydneykid? i dont get how u can make it expandable one way but not the other ? i know u use flat bar but how do u make it so the manifold can expand outwards from the engine block with a staight peice of bar? or do u have a bend in it?

pics tell a 1000 words for dummies like me

I don't worry about primary pipe expansion, they aren't very long so their actual expanaion is very small. They are also not straight, some expanion is upwards not outwards. Plus I have a solid bar from the turbo flange to the cylinder head flange, so they can only expand outwards as much as the solid bar does and its only 60 mm long. A 3% expansion is only 1.8 mm.

There is a far greater expansion potential for the turbine and wastegate exhaust as they are much longer, that's why I use a flat (2 dimensional) bracket there.

cheers

[Roy]

steam pipe all the way

Im still a big believer in weld the thing properly and you dont need to use big, heavy, thick wall pipe. The only reason i would use steam pipe is if you want to play with wall thickness to get a smaller runner ID for gas velocity. But the weight and ball ache in welding thick pipe...i dont see an advantage.

I don't worry about primary pipe expansion, they aren't very long so their actual expanaion is very small. They are also not straight, some expanion is upwards not outwards. Plus I have a solid bar from the turbo flange to the cylinder head flange, so they can only expand outwards as much as the solid bar does and its only 60 mm long. A 3% expansion is only 1.8 mm.

There is a far greater expansion potential for the turbine and wastegate exhaust as they are much longer, that's why I use a flat (2 dimensional) bracket there.

cheers

A bolted support makes it a lot easier to mount the manifold. A welded bit of rod between the head flange and turbine flange coiuld make the thing almost impossible to mount...