simple log style top mount manifold

[7808]

heres the plan. 1.25" 45* weld els, (maybe a 90* for the farthest cyl) ,extended a little with 1.25 tube, each merged into either a 1.5" or 2" length of pipe, a 90 on the end with a t4 flange on it (top mount)

weld els and tube would all be schedule40 mild steel. already have a mild steel head flange.

what do you guys think ? 1.25 runners into a 1.5 or 2" tube should flow ok?

after ordering another ebay cast manifold, my unprofessional engineering opinion tells me it cant possibly flow that well, mainly the blocky inside of the "collector", the ebay tubulars manifolds looks they flow good enough but are too risky, and the non ebay cast manifolds are too spendy for what they are, and I think I can do better. also my BW turbo is pretty big, im not 100% sure my turbo will clear everything with any of the off the shelf manifolds.

I tried to realize my thoughts in sketchup for the hell of it, but quit shortly after.

[7808]

this is kinda what I was thinking..




I was more or less asking if stepping up to 1.5 or 2" pipe for the main runner would be worthless, or cause flow to slow down, 1.5 vs 2 etc..

[autowa]

http://www.bimmerforums.com/forum/sh...Turbo-Manifold

I think that style is what your after?

[wazzu70]

I actually think something like this would work just fine. Schedule 40 steel is heavy as hell. Maybe use schedule 10 stainless instead which is still plenty thick.

Instead of using a T into the log, maybe use a 90* and notch it into the main runner. A little more work, but it keeps the flow going in the right direction and is a little better transition.

Treadstone sells some "DIY" manifold kits with weld els and also they have cast collectors ect if you want some ideas.

[m3mods]

I actually think something like this would work just fine. Schedule 40 steel is heavy as hell. Maybe use schedule 10 stainless instead which is still plenty thick.

Instead of using a T into the log, maybe use a 90* and notch it into the main runner. A little more work, but it keeps the flow going in the right direction and is a little better transition.

Treadstone sells some "DIY" manifold kits with weld els and also they have cast collectors ect if you want some ideas.

+1 on the 90*'s I think they'd be hugely beneficial to the design.

[Nutzy]

I'm fairly confident that a nicely made 6-1 or TS variant manifold would be a superior device with some HP gains, but I've often wondered how a nicely made 'log style' would work out? Of course notch in the 90* weld-els and so on to make sure flow proceeds in the right direction etc. WG placement can be in a good spot, the mani is compact and relatively simple, heat dissipation kept to a minimum (lower surface area). I can see some pluses for sure, and in a 24V RHD E30, space restriction is no joke!
As for a tapering up in size, how needed (or how much, if it is) is this really, considering we are not dealing with constant flow but rather pulses?

Test like this one:

http://www.full-race.com/articles/Bs...st_writeup.pdf

Show a tubular mani against the worst in log style design.

This is better ja.

[7808]

yeah that's very similar to what I was thinking also. I like that. minimal welding and fab work, and surface area for heat in the engine bay was a good side effect I didn't think of..

was not planning on using Tees, keep the flowing going towards the end. tees are fine for 4cyl with a center exit, I was going for 45s , not sure if id even need 90s, probably only for the farthest cyl so it just goes right into the end

yes sch40 is thick walled, also easy for welding though, probably minimal weight gain. few pounds. big deal.

I was wondering if stepping up to 1.5" for the main runner would be beneficial or not, or 2", but that might actually slow down the flow of hot gas to the turbine.

other idea I was kicking around was pairing 123, and 456, (also into a "log") both main branches 90 up and merging them at the flange. would be fairly easy too. easier to fill in a t4 flange also

[Gmfwd]

I built one from hacked up stock manifolds and exhaust tubing. It lasted me a season of drifting now I am trashing it, If I made it properly however, It could of been nice I guess. Oh well for 40 bucks in parts it was a cool learning experience.



Made 280whp at 8 psi on a base ignition tune and a gm truck turbo. I am swapping to a SPA manifold now and leaving the rest unchanged so I can see if the manifold really flows that crappy or was my tune that bad. 1 deree of timing gained me 20WHP but then I had to be off the dyno, so I assume the tune is pretty far off.

[7808]

Hacking up the stock manifolds crossed my mind, the ebay cast manifolds are pretty unimpressive, i dont think you can do much worse, but they work fine. I already bought a nice mild steel head flange from fabrication supply

[Nutzy]

I suppose another way of thinking of it is the SPA manifold is pretty much a log style, no? And it makes some good numbers. I'd have gone for something like the SPA save for the face the car is RHD and the steering would be in the way of the turbo.

[Butters Stoch]

$475 shipped for new SPA. T3 or T4. I think I have a couple kicking around.

[jjjjjjj]

I'd love to have a cast top-mount manifold option. I'm paranoid after my old headers cracked repeatedly and couldn't easily afford $2k+ for an AR!!

[7808]

I prefer top mount as well. if I was a pay to have turbo kit installed and then never mess with any part of it for yrs type, I probably wouldn't really care. but I like working topside on my car if possible, I don't have a lift. also not a fan of using pumps to make sure the turbo drains and other low hanging piping.

[m3mods]

I'd love to have a cast top-mount manifold option. I'm paranoid after my old headers cracked repeatedly and couldn't easily afford $2k+ for an AR!!

Been wishing there was a cast top for e36's for quite some time now too

[wazzu70]

If you got enough people together and contacted a company like SPA or Treadstone you could probably have one made.

[m3mods]

If you got enough people together and contacted a company like SPA or Treadstone you could probably have one made.

That's the hard part.. Would be pretty cool though

[7808]

ill see how the one I make turns out, maybe I can offer others decent priced mild steel top mount manifolds.. for people like me that don't want ebay top mount, cant/wont swing the money for the pretty stainless ones only to bolt it between a filthy engine and a cast steel turbine housing, and don't want to buy a poor flowing ebay cast bottom mount.

Im guessing spa just doesn't sell enough bmw manifolds to bring the price of having them cast down? not sure why else they would be 5x the price of cast manifolds for other cars.