Twin scroll manifold with unequal length runners?

[spooled240]

I'm noticing more and more OEM and aftermarket applications NOT using equal-length runners on their twin scroll turbo setups. Some are almost log style, like the BMW N55/N20 and the evo x engine.

I'm considering fabricating a twin scroll bottom mount manifold for stealth and small packaging and would like some input on any performance drawbacks. Thx

[S14rebuild]

Those log style manifolds are cheaper to fabricate/ manufacturer hence thats more the oem cars.

Equal lenght is the way togo

[RalliartRsX]

Reliability, cost and efficiency.

It cost a while lot less to mass produce a much more reliable cast manifold that doesn't lose a whole bunch in terms of efficiency compared to tubular.

[spooled240]

Right, but there must be a reason why they still went through the effort in going with a twin scroll turbo.

Open scroll < unequal length TS < equal length TS

What I'm curious to know is just how much of an advantage it is to have equal length runners. Would be cool to see a test between the two twinscroll setups.

[S14rebuild]

I think FULL RACE did some testing reguarding this...ill see if i can find it, might bring some info to the thread

[S14rebuild]

https://www.full-race.com/full-race-...type-analysis/

https://dsportmag.com/the-tech/twin-...-great-divide/


Not what i was lookn for, but heres sum info
...

[RalliartRsX]

Originally Posted by spooled240

Right, but there must be a reason why they still went through the effort in going with a twin scroll turbo.

Open scroll < unequal length TS < equal length TS

What I'm curious to know is just how much of an advantage it is to have equal length runners. Would be cool to see a test between the two twinscroll setups.

As I said, you are not losing THAT much efficiency for it to warrant dropping the developmental and manufacturing cost for a true EL TS manifold. Packaging concerns also dictate not designing a true equal lenght. Also all that extra material generates a significant amount of heat

OEM mass produced = a non EL is not necessary

If you are spending the cash, get a proper equal lenght TS.

[spooled240]

Originally Posted by S14rebuild

https://www.full-race.com/full-race-...type-analysis/

https://dsportmag.com/the-tech/twin-...-great-divide/


Not what i was lookn for, but heres sum info
...

I saw that, but its comparing open scroll and twin scroll

Originally Posted by RalliartRsX

As I said, you are not losing THAT much efficiency for it to warrant dropping the developmental and manufacturing cost for a true EL TS manifold. Packaging concerns also dictate not designing a true equal lenght. Also all that extra material generates a significant amount of heat

OEM mass produced = a non EL is not necessary

If you are spending the cash, get a proper equal lenght TS.

I guess what I'm looking to find out are the quantifiable differences in performance. Spool time, top end hp etc. I hate huge, complex tubular manifolds. Not stealthy and emit a ton of heat.

[S14rebuild]

Equal lenght will always provide more hp.

On low hp setup cast manifold will allow for quick spool. But once tryn to produce higher hp it becomes restrictive and exhaust pulse fight one another and acually hinder spool time.

[spooled240]

Originally Posted by S14rebuild

But once tryn to produce higher hp it becomes restrictive and exhaust pulse fight one another and acually hinder spool time.

Well that doesn't make sense. The exhaust ports are matched in a way where they never interfere with each other in a twin scroll setup.

[S14rebuild]

Originally Posted by spooled240

Well that doesn't make sense. The exhaust ports are matched in a way where they never interfere with each other in a twin scroll setup.

That is correct for a equal lenght twin scroll... i was stating that for a log style/aka cast oem manifold. The pulse just slam into one another and then just forced thru the turbo.

[Kingtal0n]

While I appreciate the effort, engineering, attention to detail, etc...

As a general hobbyist (consumer based product source with budget in mind and limited fabrication ability)

I'd recommend to carefully to select a manifold based on
1. clears A/C, PS and other systems easily
2. Hardy/longevity construction (won't break under extreme circumstances)
3. utilizes easy to source and replace components i.e. traditional exhaust gaskets and tubing
4. easy to access and work on, turbo isn't out of reach, lines are easy to snug, etc...
5. Offers a range of upgradability (many turbo choices and housing choices will fit)

Rather than one which offers all out peak performance at the cost of being difficult to work on, difficult to find parts for, may interfere with accessories, hard to replace if it cracks or is damaged, and so forth

In other words, if a guy who doesn't like to work on the car, just drive it, he may prefer the easiest manifold to work with that will last the longest. Not necessarily the best performing model.

[foreverdeath]

Most aftermarket manifolds are not equal even if they are divided. It takes a great deal of work to make a equal length manifold in a tight space, especially if you want a narrow collector angle (for good top end flow).

I think it took me 2 weeks to figure out how to make my k24a2 turbo manifold in investor better I wasnt hitting the subframe, shock tower, hood and I had space for the wastegates. It turn out a twisted bunch of noodles which was a PITA to weld. My new design is better but at the cost of a wider collector angle. This manifold the runners are all within ~1% length.


The length of the runner I would think is more of a factor on turbine efficiency when trying to spool up as it can work like a good equal length header scavenging exhaust while turbo manifold pressure is low, which aids in quick spool. Once spooled I dont if it really has a noticable effect other then a sound.

Sent from my SM-G960U using Tapatalk

[PoorMans180SX]

Here are some good threads to glean information from. They provide real world and back to back examples, unlike what you'll find on most of the internet.

https://www.evolutionm.net/forums/ev...xperiment.html

https://www.evolutionm.net/forums/ev...xperiment.html

https://www.evolutionm.net/forums/ev...-gtx3576r.html

https://www.evolutionm.net/forums/ev...-setup-10.html

Basically what it comes down to is optimization. A small runner, compact manifold will help reduce heat loss and might net you a little spool. However, if you're looking to maximize efficiency and power production, an equal length manifold is where it's at.

Here's another back to back test:

http://morrisonfabrications.com/tech...-dyno-testing/

[spooled240]

Originally Posted by PoorMans180SX

Here are some good threads to glean information from. They provide real world and back to back examples, unlike what you'll find on most of the internet.

https://www.evolutionm.net/forums/ev...xperiment.html

https://www.evolutionm.net/forums/ev...xperiment.html

https://www.evolutionm.net/forums/ev...-gtx3576r.html

https://www.evolutionm.net/forums/ev...-setup-10.html

Basically what it comes down to is optimization. A small runner, compact manifold will help reduce heat loss and might net you a little spool. However, if you're looking to maximize efficiency and power production, an equal length manifold is where it's at.

Here's another back to back test:

http://morrisonfabrications.com/tech...-dyno-testing/

This is exactly what I was looking for, thanks!