Custom made Exhaust manifold

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dilmah

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Well I thought I would try my hand a building an exhaust manifold out of steam pipe. I have a rough idea on the cost of parts - $100ish. The YD25 exhaust manifolds are made from cast iron and have a habit of cracking. If anyone knows my build then it will be running significantly higher boost than most Navs.

What I need to know is how would I go about bolting it up to the head? Do I reuse the flange and just cut the rest of the cast iron off? And what would be a suitable size pipe to use? 1 1/2" or 2"

Turbo will be in the same place as the old one so I don't have to redo too much of the exhaust.

Cheers
 
cast welded to mild steel- you might want to re think that!

I'd go grab a gasket and use it as a template to cut one out of 6 to 8mm plate steel.. job done and you can weld it up with no concerns of it cracking between the cast and mild steel :)

And that way you can line the ports up nicely............ broombroom
 
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for the flange you want at least 12mm plate steel. gives a little roof for planing later. 10mm is bare minimum.
find a spare head to bolt it to while welding. getting it to not bend from the welding is important.

design wise, i would go semi/short extractor style. its always going to be a compromise on flow vers volume/length.
 
^+1 cast iron and mild steel expand at different rates.

I wonder if it's possible to make extractor-like exhaust manifold that combines near the current turbo position, allowing you to orient the turbo a little better so that the dump pipe doesn't have such a tight exit angle.
 
^+1 cast iron and mild steel expand at different rates.

I wonder if it's possible to make extractor-like exhaust manifold that combines near the current turbo position, allowing you to orient the turbo a little better so that the dump pipe doesn't have such a tight exit angle.
You can definitely build an equal length manifold, just depends how much time you want to take and how good your welding is.

As above, for the flange plate, grab a gasket and take it to an engineering joint that does laser or water jet cutting and get them to chop one out of 12mm plate.

As for what size pipe to use, just match it to the port size. Depending on whether you want equal length or log type will depend on what you need to use. If you want to build a a log type, you may get away with 2 90deg bends and 2 tee pieces. Then cut the outside of them out and weld the turbo flange plate on.

If you want equal length you will have to get creative. Maybe google some pics to see how others have done it.

Should be a very interesting project anyway.
 
Yeah I have CAD so designing flanges is no problems. I will make it all out of mild steel now you have said that about welding cast to mild. I'm thinking log type as I don't have the room to make equal length piping
 
you don't want equal length extractors. but if you can place the turbo in a good spot and pair the runners you could do unequal length extractor which has the advantage of less manifold volume and better flow than log.
 
I really want to move the primary turbo off the back of the firewall and higher up but with the compound setup thats a lot of work as I would have to redo the exhaust from the primary - secondary and the exhaust off the secondary as that might end up moving as well.

I really need to pull the old exhaust manifold off one off first to see what I'm up against
 
Few pics of the OEM head, the intake ports are of decent size but the exhaust ports are tiny, only 32 x 32mm





To stop the flange warping during welding I bolted it to a offcut of 75 x 50 x 5mm RHS. I torqued the 10mm cap screws down to 60 ft/lbs.



I got the flange laser cut by tracing around a new exhaust manifold gasket.


I got 2 x T pieces and 2 short 90 degree bends. All 1 1/2" steam pipe.
 
I then cut 20mm off the ends of the T pieces so they would match up with the elbows and 12mm off one of the T pieces to it would match with the other one. All mocked up ready to be tack welded in place





I need to grind a lip on the edges I cut so the weld will get some good penetration. I should have it finished tomorrow, stay tuned for an update!
 
Nah just mild steel;. Ill get the finish product triple coated to improve the exhaust gas flow

Few more pics, its 95% welded now





I baked it in the oven to stress relief the welds so it wont warp too much when I release it

 
Haven't decided yet, going to bolt it to the head and sus out the orientation. Won't be for a while though. I will do this in the offseason. trying to get the car ready for racing ASAP
 
Nice work mate.

I see extractor style exhaust manifold was brought up. Interesting to note that Mercedes on the latest generation of F1 turbo engines started out with extractor style system but went back to log style, saying the shorter run, less volume and more heat was more beneficial (in there case anyway) than any scavenging advantage created by extractor style system. Being F1 i would imagine they would have worked out every pro and con down to the 10th. decimal place :)
 
WOW $550 for a manifold???

To put this in perspective I spent $46 on steam pipe, $25 to get the flange laser cut and maybe 4hrs to do all the fab work (including making the jig). If I didn't have to make the jig then Id say 2hrs tops on the fab work.

If I finished what I have to an OEM replacement spec there is about another hour worth of fab work to put the turbo flange on. Lets say 3hrs all up of fab work.

This guy must be making a decent profit, $100 in materials and 3hrs labour.
 
If you start making them and selling them, I'll buy one haha.
The guy on ebay is the only alternative to another stock cast manifold.
Unless you got a shop to custom fab a manifold for you. Which I'd imagine would be expensive.

Sent from my SM-G900I using Tapatalk
 

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