Stock Exhaust Manifold? When To Change?

[Badgaz]

Howdi everyone,

i've been thinking ALOT about where to next with my skyline. my modification list is as follows

PowerFC

z32 maf

850cc injectors

GTR Fuel pump

Evo 3 intercooler (stock piping positions)

greddy type rs bov

factory exhaust manifold

hi-flowed factory turbo.

i've been following and looking at the posts regarding the GT3076R turbo and noticed this turbo can fit with the factory manifold. my end power goal is a reliable 450-500hp

what is possible with a turbo like this and keeping the stock exhaust manifold?

[GTSBoy]

Where are you measuring this HP?

[Badgaz]

wheels

[Ben C34]

Scottynm35 has seen huge power through stock mani. I would leave it there.

[Badgaz]

thats good my tuner thought these might be a restriction....are they worth hpc coating or any of that jazz? what would be the holset equivalent to the 3076r?

[GTSBoy]

That's upwards of 340rwkW and is therefore still within the ability of the stock manifold to flow, but getting well up toward the top of what works. So you'd do well to look into die grinding the runner ports a little to open them up, but particularly at the outer ends where they don't tend to line up with the head ports as well. Clean them up to get better alignment basically. Maybe a little tickle into the collector.

The best thing you could do though would be to look at the Hypergear thread and see what he has done (somewhere in the last 10 pages) to a stock manifold. Makes it able to support a hell of a lot of power by fixing it so the wastegate flow doesn't have to go through the collector into the turbo housing. (Obviously for mounting an external gate on it). It's not a trivial mod, but almost anyone half handy should be able to do it.

[Badgaz]

Thats good information to know.... i think i'm probably being a tad optimistic for that power figure given that my donk has done 300,000kms now....perhaps 300rwkw is more realistic. will mosey on over to the hypergear thread.

[jay-rod]

300k....good luck, better hope that engine is in good nick :S

[Badgaz]

change the oil religiously(every 5k). it doesn't go too bad....this was the other night. http://www.youtube.com/watch?v=Nhb2pNCTWzY

[Blackkers]

wow how does it go with 300k on it? does it just drink oil? I reckon mine would at that mileage..

[Badgaz]

its fine...i've just changed the oil...it drinks probably half a litre between oil changes? i put 5 litres in and about 4.5 litres come out. i've just tidied up the tune so hopefully its a little better now...was running 9 afrs @ wot prior to tune for a good 50-70 thousand kms.

[AngryRB]

I've had a 6boost twin scroll and a stock manifold with a GT/GTX3076 setups on same tune and was running around 320-340kw, both felt the same on the street which was unexpected, the 6boost has larger and longer runners and collector which in comparison to a stock

manifold might effect things negatively on a street car?? just my opinion

Edited February 25, 2014 by AngryRB

[Badgaz]

That's upwards of 340rwkW and is therefore still within the ability of the stock manifold to flow, but getting well up toward the top of what works. So you'd do well to look into die grinding the runner ports a little to open them up, but particularly at the outer ends where they don't tend to line up with the head ports as well. Clean them up to get better alignment basically. Maybe a little tickle into the collector.

The best thing you could do though would be to look at the Hypergear thread and see what he has done (somewhere in the last 10 pages) to a stock manifold. Makes it able to support a hell of a lot of power by fixing it so the wastegate flow doesn't have to go through the collector into the turbo housing. (Obviously for mounting an external gate on it). It's not a trivial mod, but almost anyone half handy should be able to do it.

Yeah when i did my manifold studs and gasket last i took to it with the die grinder and took all the casting marks off and tried to port match the end manifold ports a little better...its quite the lip isn't it!

[ARTZ]

300-350 is usually considered about the safe area for stock manifold that sees some hard duty... I'm sure you can always push 400 through it but question is, do you really want to...they are already prone to warping and cracking. Of course if it's only a street car that does the occasional skid, its not really going to be an issue though.

[scotty nm35]

With a big enough turbo you should see 450wkw through the stock manifold, but it will become a restriction at much less. You should be fine with 340kw on the right setup.

Obviously the better flow from a good aftermarket manifold helps with the top end, but larger runner manifolds also take longer to build pressure, causing the turbo to be slightly less responsive down low. They are also illegal so I only like changing to them on track cars, otherwise there is a good chance you will get defected the minute the bonnet is popped.

its quite the lip isn't it!

Just remember, the manifold grows considerably in length as the exhaust temp rises. I imagine the ports would line up fairly well when the manifold is cherry red, as it could be around 10mm longer than it was. The water cooled alloy head wouldn't expand anywhere near as much.

[GTSBoy]

The manifold is clamped to the head. I would tend to think that the thermal expansion turns up as stress in the cast iron rather than much actual dimensional change. Otherwise the fasteners will be sliding across the flange surface and the flange will be sliding across the gasket and everything should turn to poo within a few hours of operation (ie fall apart and start leaking).

Edited February 25, 2014 by GTSBoy

[Badgaz]

hmmm the conical washers are the only thing that are there to take up this expansion...and are some of the stud holes on the manifold slotted slightly? is this why?

[scotty nm35]

The manifold is clamped to the head. I would tend to think that the thermal expansion turns up as stress in the cast iron rather than much actual dimensional change. Otherwise the fasteners will be sliding across the flange surface and the flange will be sliding across the gasket and everything should turn to poo within a few hours of operation (ie fall apart and start leaking).

That is exactly what happens, and why you need large thick washers under the nuts. I wonder why the manifold studs are always snapping...

Clamp the manifold down to tight and it will transfer the stress into the manifold, good chance it will crack not long after, unless the stud lets go first. I would be torquing them down to manufacturers specs with oem gaskets, I am sure Nissan did a fair amount of r+d on the subject.

[Badgaz]

those thick washers are conical in shape to allow for the expansion.....i've snapped 4 studs before and had to drill out a snapped easyout on cylinder 6....always use the factory washers.

[GTSBoy]

How do conical washers allow for expansion along the plane of the flange?

Conical washers are a SPRING washer. They allow for expansion along the axis of the bolt/stud so that they don't get loose through heat cycling.

The thermal expansion along the plane of the flange is the reason that studs end up breaking. They get worked from side to side.

I'm surprised I have to explain this stuff.