log manifold vs short length tubular

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240revival
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log manifold vs short length tubular

Post by 240revival »

I've decided to go with a hx35 so in turn I've decided to build a manifold for it instead of modifying one. And since this is my first manifold I want to keep it simple and keep the cost down. My question is, would it be worth the extra time and a little extra money in materials to build a short lenght tubular like this; viewtopic.php?t=44615. Or should I just stick with a basic log mani. It looks more effecient than a log mani, but is it really?
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supakat
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Post by supakat »

Look at my thread. I am using a cast top mount with hx35. Fitment is good.
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240revival
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Post by 240revival »

I did see what you were using, but I was thinking if I can make something that is more efficient for about the same cost as buying one that is less efficient it would be worth it. I guess looking at the log manifold makes my ODC kick in. I know theres a way to have a simple design that is way more efficient than a log.

To me it seems like the short length tubular would have better flow which would help the turbo spool faster while giving a little more top end than the log at the same time. And it would be almost as strong.
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Kamilitaryman
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Post by Kamilitaryman »

From my understanding, there is a limit for a log-style manifold and how far you can push it. Some companies claim that they're good for 400-500hp. They also spool a turbo faster. Even though, 400 is MY power goal, I decided to go with a ram-horn design because they've been proven to make numbers past that. Thus giving myself room for upgrades later. Since you are going to fab up your own, get 2 flanges and make both, this way you can decide which will suit your needs better.
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Post by nissanfanatic »

Anything with compressible fluid flow is typically factored by using the square of the speed of fluid velocity. The drag incurred by using a log manifold is probably along those lines IE less power loss at lower power levels.
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240revival
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Post by 240revival »

Although I dont plan on breaking 500hp, the power limit with a log manifold was another reason I was looking for a more efficient design.A side by side test would be interesting and a possibility in the future but it'll be awhile until Im making the power to really warrant that. Id rather use the $100 for one of those manifolds towards something else right now.
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Kfred
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Post by Kfred »

I have an etd manifold I will sell you if you aren't stuck on making your own manifold. Its thick mild steel, tough as nails. Pm me if interested.

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Post by nismo silvia »

It would build my own I dislike the rusty ass look mild steel gives
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Post by p00t »

If you're not in a rush and like doing things to learn making a log manifold is the best place to start. Just make sure you have something more powerful than the cheap China 90 amp welders.

My second manifold came out 3x better than my first log but that only because the log manifold taught me a bit about fabbing exhaust manifolds.
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Post by beercandrifter »

nismo silvia wrote:It would build my own I dislike the rusty ass look mild steel gives
power/ceramic/swain coating ftw.
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240revival
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Post by 240revival »

Most of it is about just making my own manifold and the rest is about saving money. I do have access to a mug welder that is plenty big enough, but I have been thinking about investing in a tig. After I get everything put together I will build the opposite style just for a dino comparison

Kfred: will that manifold have clearance with a holset?
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Kfred
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Post by Kfred »

Couldn't say if the holset will clear or not. The manifold is ceramic coated so there will be no rusting issues.
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mattheripper
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Post by mattheripper »

What thickness metal are people using for the exhaust flange and the turbo flanges?
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Post by Nova_Eclipse »

3/8 is fairly common, if I'm not mistaken. Go here:

http://sdsefi.com/techheader.htm

This is a more or less step-by-step of how to fab a turbo manifold, and what to make it out of.

There's a number of other fab/DIY articles and tuning info on that site. Go to http://sdsefi.com/tech.html to see them all. The article on making an intake manifold is an interesting read as well. :D
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beercandrifter
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Post by beercandrifter »

for your turbo a log manifold will exceed the boost on this turbo you are going to put out. believe me.

im at 20psi on my log manifold i put together and hx35.

that kind of pressure level you start to break things
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