How much power loss or spooling time comes from manifold

[jeff01]

I'll start making exhaust manifold for my 2L type 4 engine. It gets a big turbo and I´m a-bit worried about spooling time.
Should I do like all do (4 to 1 with equal lenght pipes)
Or should I do it like 4 to 2 to 1  so that 2 ports in 1 head will be connected  like they are on subaru.
How big could be the difference?

second choise should be lighter, easier to make and give less heat away before turbo but what about spool time and power? how big difference?

thank you

[gizago]

I'd be tempted to do it the way subaru do- 4 unequal length pipes so you can run a bigger turbo with less lag, seems to work for them 

[Fiatdude]

I went from this



to this



Heat is what makes a turbo work == the more pipe you have the more heat loss -- The only change I've had to do with the second header is put a slip joint in the back cross pipe as my big engine grows so much it would cause the rear flanges to pull away from the heads and I'd get an exhaust leak -- next picture is a video -- click on it

[Zach Gomulka]

I'd be tempted to do it the way subaru do- 4 unequal length pipes so you can run a bigger turbo with less lag, seems to work for them 

And the reason why Subaru's sound like shit.
http://rusubaru.com/equal-length-vs-unequal-length-headers/
They are unequal length for packaging, not performance. Equal length headers for Subaru's are proven to make more power.

[BeetleBug]

For performance and driveability, make it puls split 1-3 / 2-4 and twin scroll. For best boost control use two wastegates.

[gizago]

And the reason why Subaru's sound like shit.
 

In your opinion 

I love the sound of subaru flat four turbo motor personally.

[Zach Gomulka]

And the reason why Subaru's sound like shit.
 

In your opinion 

I love the sound of subaru flat four turbo motor personally.

Do a search for "Subaru equal length headers" and you'll get a few sound clips (along with other good info). They really smooth out the note, gets rid of that dune buggy sound.

[Fasterbrit]

I thought the reason Subarus sounded odd compared to a VW is that they have a different firing order? I might be wrong...
To me they sound like a tuned VW running on three cylinders.
 
One way to keep exhaust enthalpy hot is to use stainless tubing and heat wrap it. Stainless tube dissipates heat at lesser rate compared to mild steel. One big mistake some people make is the belief that a turbo motor requires large bore tubing to perform. This is not always the case. Going too large on a turbo header will cause massive turbo lag. Far better to be slightly undersized than greatly oversized.  

On a turbo motor the inlet manifold design is far more critical for performance loss/increase. It takes far more than a good fabricator to make an efficient inlet manifold. This is where mathematics come into play in a big way.
 

[jeff01]

Thanks for all ansvers. Unfortunately I really didn´t remember subaru exhaust correctly.
My idea was connecting 2 ports in 1 head like they are connected in log style manifolds......I Mean that they are connected ~10cm from flange.

Like  here but I think I can do better.

Turbo will be in the middle of the engine and left-right side equal.
All Im afraid is  that what it does when 1 and 2   are connected nearly and  3 and 4 the same

Then 2 pulses comes from left, then 2 pulses from right but I don´t know is it good or not.  If its not good Then I have to do it another way.
 EDIT: I looked that when they do split pulse exhaust for 4 cylinder engine then they connect pipes so that  1 pulse to one pipe and second to another, third goeas where first went.....so connecting  1/2   and 3/4   in vw looks odd or I´m mistaken?

[Fredrik Grönlund]

Thanks for all ansvers. Unfortunately I really didn´t remember subaru exhaust correctly.
My idea was connecting 2 ports in 1 head like they are connected in log style manifolds......I Mean that they are connected ~10cm from flange.

Like  here but I think I can do better.

Turbo will be in the middle of the engine and left-right side equal.
All Im afraid is  that what it does when 1 and 2   are connected nearly and  3 and 4 the same

Then 2 pulses comes from left, then 2 pulses from right but I don´t know is it good or not.  If its not good Then I have to do it another way.
 EDIT: I looked that when they do split pulse exhaust for 4 cylinder engine then they connect pipes so that  1 pulse to one pipe and second to another, third goeas where first went.....so connecting  1/2   and 3/4   in vw looks odd or I´m mistaken?

On inline 4 cylinder you must pair cyl 1/4 and 3/4. Becuase Vw flat engine has different firing order you must pair cyl 1/3 and 2/3. Reason for this is that you  want 180deg between pulses on every cylinder.

cyl 1 0 deg
Cyl 4 90 deg
Cyl 3 180 deg
Cyl 2 270 deg

[Tekken]

For performance and driveability, make it puls split 1-3 / 2-4 and twin scroll. For best boost control use two wastegates.

Why two wastegates?

[Andy Sykes]

one for each side of the collector



there will be one on the other side as well

[markvo]

You may need an intake waste gate too! Whats gonna happen when you shut the throttle plate downstream of the boost? Nut on the turbo wheel may back off!

[paul_f]

I thought the reason Subarus sounded odd compared to a VW is that they have a different firing order? I might be wrong...
To me they sound like a tuned VW running on three cylinders.
 

The firing order is different, but the numbering of the cylinders is different to a VW, so they actually have the same firing order.

It is the manifolds that give them the different sound to a tuned VW

[mymedusa]

I thought the reason Subarus sounded odd compared to a VW is that they have a different firing order? I might be wrong...
To me they sound like a tuned VW running on three cylinders.
 

The firing order is different, but the numbering of the cylinders is different to a VW, so they actually have the same firing order.

It is the manifolds that give them the different sound to a tuned VW

thats true. my aircooled also sounds a bit like a subaru in fact of the true twin scroll header and turbo. and also what "all torque" says is totally  right. stainless keeps the energie in the system and wrapping could help too. not that big manifold also helps spooling. i have done all that and my spool is amazing! i have read somewhere in the net from a guy that works at garrett and he said...use manifold diameters LESS in diameter than a N/A engine would use with 2/3 of the power your engine should do...this is just over the thumb rule. but its good to think about it and keep it smaller. even the short as possible is good.
at the end it depends on how you want to use it. in race trim i would not keep it too small ...lets say small enough, and the pipes as short as possible and if possible same lenght. this are the things that will help on top end. you just need good spool in the area you will use your engine.

[Fiatdude]

I know this is the Lounge -- but who cares what it sounds like as long as it is making HP -- the video on my engine running (very shitty on a crap tune) isn't anywhere near equal length and it sounds OK -- and it made over 300HP @ 4000 on a short run due to the exhaust gasket blow out

I've got a lot of friends that are big names in the turbo world and all of them say that equal length headers are great for NA but HIGHLY over rated on a turbo application -- you want the shortest pipes possible to get the heat into the turbo as fast as possible.

The twin waste gates are not necessary -- just blowout a exhaust gasket or crack a manifold and you'll find how quick you will lose boost -- -- The V-8's use 2 because they are driving a turbo from each side of the engine -- If you really think you need 2 just get 1 big one -- they come in really big sizes --   here is a 60 mm one  http://www.turbosmartonline.com/index.php?id=51 --- --- most V-8 V-6 systems for 400-500 HP only need a 38 mm one -- it really doesn't need to be any bigger than your exhaust tubing --

IF you are running a blow thru system you diffidently need a pop-off valve between the turbo and the butterflies

Your turbo lag (spooling time) comes more from not sizing your turbo correctly to you application than to the design of your header --

[jeff01]

I think theres no reason for making twin scroll exhaust when you are using only 1 wastegate.
 With 1 wg you just connect 2 different side, then gases always go where its easier to go but the pressure is what pushes the turbo forward and you gonna loose low spool.

Maybe I´m thinking wrong

[Frallan]

Well, is not the wastegate ireleveant when it is closed and you are in spool mode.
When the wastegate is bleeding pressure, it does not matter if you have the two sides connected?

[BeetleBug]

I`m getting used to people thinking that putting a turbo on their engine will make up for other "mistakes" A poorly built engine will always be a poorly built engine, turboed or not. BUT it will probably make more power supercharged, for a while. A good header is just as important on a turbo engine as it is on a NA engine but perhaps not as critical?

Look at the header of one of the most powerful VW`s in the world, it is as short as it can be on our engines placing the turbo just above the engine case.

No need for two WG`s unless you have a split puls header. Simple is often better... sometimes.

BB

[jeff01]

Well, is not the wastegate ireleveant when it is closed and you are in spool mode.
When the wastegate is bleeding pressure, it does not matter if you have the two sides connected?

Sorry but I dont´t understand you 100%  because my language barrier.   What means: "ireleveant"  

I meaned that IMO all wastegates connect 2 pipes what should be isolated of each other until the turbine.
When boost is up theres no difference at all.

I`m getting used to people thinking that putting a turbo on their engine will make up for other "mistakes" A poorly built engine will always be a poorly built engine, turboed or not. BUT it will probably make more power supercharged, for a while. A good header is just as important on a turbo engine as it is on a NA engine but perhaps not as critical?

Look at the header of one of the most powerful VW`s in the world, it is as short as it can be on our engines placing the turbo just above the engine case.
No need for two WG`s unless you have a split puls header. Simple is often better... sometimes.
BB

Turbo engine just dont need that exhaust gases suck fresh air into the engine with gas interia in exhaust......because boost should be higher than pressure in exhaust manifild when turbo is choosed correctly.

Turbo helps a-lot when your engine is not breathing well but when shomething has to break then under boost it shurely does.

Heat what comes from short pipes is more important than equal lenght but when it doesn´t make it much longer then equal lenght is never bad and should be done. Like turbo on the middle of type 1 when 1 pipe comes from each corner......shortest way and  equal too.

I would always prefear 1 wg when turbo has not twin scroll.

[Frallan]

Well, is not the wastegate ireleveant when it is closed and you are in spool mode.
When the wastegate is bleeding pressure, it does not matter if you have the two sides connected?

Sorry but I dont´t understand you 100%  because my language barrier.   What means: "ireleveant"  

Sorry for that word. I could expalin it as "does not matter".
When the turbo is spooling up, the wastegate is closed until required level is achieved then it opens and yes at that point it connect the two sides but at that point, it does not matter.

By the way, I do not know, I am only thinking out loud in writing. Maybe someone knows and can help?

[jeff01]

when wg openes then it connects port from manifold to exhaust  but bouth side of the manifolds are connected all the time....isn´t it so?? 

wg is just a thing with 2 holes and you have to connect 2 sides of twinscroll manifold  to one hole.....you can´t do that without connecting them.

[jaqo]

it's possible to minimise this effect by a good manifold design but it's easier to fit 2 wastegates;)