Turbo Spruitstukken deel II / Turbo Manifolds Part II

[Walter S]

volgens mij zijn er zat B230FT's geleverd in NL. Of anders B230FK (LPT), daarvan zijn er zeker zat. Er staat er nog 1 in Etten Leur, eigenaar vind het niet erg als je dat spruitstuk eraf haalt. Zit je alleen met de LPI injectoren...

[TheSaint77]

ik ga Jeroen Bosma eens bellen. Want als ik dadelijk met de turbo wil gaan rijden moet er zoiets (MS LPG) in komen. Dus vandaar.

[Jw240]

een inlaatspruitstuk is voor weinig geld op de sloop ofzo te vinden. Laat maar weten als je problemen hebt om er een te vinden, ik heb nog wel adressen.

[stealthfti]

Hi.

All but one of the 90+ exhaust manifolds that I have examined had cracks in the back: around the goilet. I believe that the main reason those manifolds crack is because the outlet is so small; and because the Mitsu turbo is also very small on the turbine side. [the small outlet is a restriction to flow; and that leads to a lot of heat being retained in the manifold. That heat makes the manifold glow cherry red after a hard pull. And that heat can put a lot of stress on the manifold and cause it to want to twist and warp and crack.]

The picture showing the T3 flange gasket sitting there on the outlet shows just how small the opening is on the 90+ manifold. I use that gasket to scribe the outline of the standard size opening onto the 90+ outlet so that I know just how much iron to grind away with my air powered die grinder and carbide burrs.

I think that trying to use a Dremel tool to grind away that much iron would take you about a week to do the job. With the tool I have, it takes me about 6-8 hours to open up the outlet and blend the ports. [a lot of work; but worth it]

The other main reason the manifolds crack is because the four flanges...where the manifold bolts up to the head...warp. The four runners are tied together so that they cannot spread apart, but the high heat causes the runners to bend like a bow. This bending action puts enough stress on the manifold that cracks will form on the backside.

If you can find a 90+ manifold that has one, or two, or even three cracks on the backside, around the goilet, it IS possible to still use that manifold.

What is NOT usable is a manifold that has cracks on any of the four runners.

The 90+ that I have on my 245T has two cracks in the goilet. The 90+ that I installed on my son's 242T has three cracks back there. Mine has been on for three years, and is still fine. Ted's has been on for two years, and is also still okay. The cracks have not grown.

Besides porting the outlet to improve the flow, I also had to make sure that the four flanges were flat. EVERY 90+ manifold that I have examined has warped flanges. Every one that I installed had to have the four flanges restored to true flatness.

If the manifold you find has a crack or two in the goilet, but the cracks are not so large as to be close to letting a piece of the manifold fall out, then you could save it and re-use it:

...port the outlet to improve the flow: very good for power; and VERY good at reducing the amount of heat that stays in the manifold.

...restore the four flanges to true flatness. That will reduce the stress that can cause cracking; and it will also help to prevent any of the manifold studs from either breaking off or pulling out of the head.

Evaluating the cracks that you will see in the backside of a 90+ manifold to determine if the manifold is salvageable or not is not ends up being a judgement call. You might want to use the pictures of the manifolds I show in my pbase galleries as a guide: they can show you what to look for; and what is still usable. The picture that show the manifold with the three cracks is the one that I installed on my son's car.

If you find a 90+ manifold that has a crack or two, you might be able to buy it cheaper....because it has some cracks. Just don't tell them that you can salvage it by porting it. [no need to give away secrets]

If you cannot locate a 90+ manifold over there, then you might look on turbobricks classifieds: sometimes a 90+ comes up for sale. Or, post a 90+ wanted ad.

I don't have any spare 90+ manifolds right now. But if I come across one or two, I'll post that here.

TF

[Jw240]

yo Thomas, thanks for the explanation.

What about welding he cracks? I know that welding cast iron is harder than normal iron and that you need to preheat it before welding. But are there any advantages to have it welded?

[TheSaint77]

Thanks Thomas for your help. I appreciate it very much. I will keep these things in mind for now and let you know when I make progress with it in my project. To be continued.

About welding the cracks; I had a 244turbo before wich had a serious crack in the (standard) manifold. I had it welded (with pre-heating offcourse) and the new owner is still driving it with no problems. So it can be done but i don't think but its not recommended to do it self because of the preheating.

[stealthfti]

Yes, Jan Willem, welding the cracks is, and would be, a viable option.

I did not have the cracks welded on those manifolds because I wanted to see if the porting of the outlet and the reflattening of the four flanges' surfaces would slow down the cracking, or stop it altogether. So far, I have seen no evidence of the cracks that were on the manifolds that I did getting larger, or leaking any exhaust gases out. The cracks are still there, and they have not gotten any worse.

...of course, it could be surmised that I did not have the cracks welded because I am some sort of cheapskate, and did not want to spend the money for the welding. [haha] That was a minor issue; but to see if the manifolds could be saved and reused just by the other procedures was the main reason I did it that way. I did not know if it would work out at the time. I wanted to find out.

Welding cast iron is as much art as it is science; and finding a professional welder who can do the work successfully is a very good find. Definitely. Not too many welders will take the time to do the preheating correctly, do the welding, and then do the cooldown slowly enough to allow the iron to cool off without re-cracking, or inducing new cracks.

If the cracks can be repaired, then along with removing the causes of the stress that leads to the cracking, such a repaired manifold should give many years of service.

So, the way to go about it with a cracked 90+ manifold would be to have the cracks welded; and then port the outlet and reflatten the four flanges. Such an approach should correct the problem; and result in your having a very good manifold that performs well: better flow and more power.

TF

[deusjevo]

My English is not that well but "cast iron" means "gietijzer" in Dutch :?:

[Jw240]

ok TF, thanks. I just asked my welding class teacher and he wanted to help me with the welding. He worked in Africa for a couple of years and he has welded everything there (leaf springs, engine blocks, guns, everything :-P).
He said that 100% nickel electrodes should be used, preheating the workpiece, and a very very good cleaning of the crack. and even then its possible that the crack comes back close to where it was welded.

I'm gonna ask what reflattening of the flanges would set me back and i'll port the manifold. probably that is enough to keep it working without problems.

My English is not that well but "cast iron" means "gietijzer" in Dutch :?:

Yep.

[Lukas Lagerweij]

It will also help when you have welded the manifold to re-heat the area around the welding so the steel-molecules can get back in there original sitiuation. This is a manner to get less tensions inside the iron.