Split Pulse Turbo/Manifolds

[bbq1988]

Hey guys,
Can someone fill me in on the pro's & cons of the Split pulse setup?

Turbo in question to make the manifold for is possibly a Holset HX40 (Super40)

Cheers

[92mr2paddy]

no point having a split pulse turbo on a non split pulse manifold vice versa,what motor is it going on?? the split pulse suposed to help spool up on large turbos, hope someone on here has more knowledge

[Lith]

Hey guys,
Can someone fill me in on the pro's & cons of the Split pulse setup?

Turbo in question to make the manifold for is possibly a Holset HX40 (Super40)

Cheers

Aside from being a little more work to construct, and sorting out wastegate feeds could be tricky - imho there is no cons to going split pulse. I am a huge advocate of it!

Some proof in the pudding for a single scroll vs. twin scroll housing/manifold combination on the same car:

http://forums.toyspeed.org.nz/viewtopic.php?t=71870

Don't do a single pulse manifold with a twin scroll turbo, though - make sure they are both split pulse.

[thegreatestben]

Have a twinscroll on the mr2 and a single scroll on the corolla.
Obviously not identicle engines but both are mitsi evo td05's.

The way the turbo spools in the mr2 is far superior, very responsive unlike the corolla which has nothing until 3500-4000rpm

[Dell'Orto]

In fairness, AW has another 200cc to spool it with though.

[thegreatestben]

As mentioned but 200cc wouldn't make as much of a noticable difference as there is. The corolla has a much better link/tune/ignition too.

Twinscroll is FTW in my application anyway

[matt dunn]

As mentioned but 200cc wouldn't make as much of a noticable difference as there is. The corolla has a much better link/tune/ignition too.

Twinscroll is FTW in my application anyway

200cc will make a massive difference to an engine of that size.

[Lith]

Yeah 200cc makes quite a big difference which sucks as twin scroll does as well, I'd imagine the one with 200cc+twin scroll would be a different animal.

[steve murch]

split pulse can improve response but kills horsepower.
and well designed exhaust open scroll turbo will perform better all round.
now a split feed waste gate works very well.
the turbos i mod for twin scroll evos and subs get the split modded big time,end result better response and more hp, up to a 20kw gain.
the headers on a turbo car aren't overly important for tuned length but too long can hurt response.
as a rough rule the header pipe should be around the same volume as the cly displacement,eg: a 2ltr is 500cc per pot
only at one point does any header work its best,every where else is a compromise.
if you want good response and power then open scroll, remember when doing a pulse tuned exhaust you increase the turbine back pressure that's why you gain a little more response,back pressure hurts power.

[mjrstar]

I was wondering about cam selection/timing with twin scroll turbos. As scavenging can be quite as complete as an open scroll, do you need to compromise and have less aggressive cams and cam timing to ensure a decent scavenging effect.

I guess the flip side is you can go larger in the exhaust hsg AR on a twin scroll and have similar boost response to a smaller open scroll housing?

I'd really like to see some back-to-back runs on twin vs single scroll as I'm seriously considering a twin scroll setup as I’m happy with the moderate power level of my 2 litre at 245kw but would love to get boost on a few RPM earlier.

[steve murch]

I was wondering about cam selection/timing with twin scroll turbos. As scavenging can be quite as complete as an open scroll, do you need to compromise and have less aggressive cams and cam timing to ensure a decent scavenging effect.

I guess the flip side is you can go larger in the exhaust hsg AR on a twin scroll and have similar boost response to a smaller open scroll housing?

I'd really like to see some back-to-back runs on twin vs single scroll as I'm seriously considering a twin scroll setup as I’m happy with the moderate power level of my 2 litre at 245kw but would love to get boost on a few RPM earlier.

more cam no matter what your using helps boost response due to the overlap but if there's high back pressure due to the turbine hsg like a split pulse youll find cly temps go up and you cant run as much timing.
the theory of going big due to the split doesn't always pan out,you should never rely on these sorts of things to compensate for a poorly designed setup.
ultimate one to one boost versus back pressure is what your after but its a case of you cant have your cake and eat it to, most road cars factory are around two to one as in 10 psi boost 20psi backpressure thus they respond well but fall over quickly.
split pulse has its place with large singles on big displacement but were talking about turbine hsg or 1.75ar or bigger.
always remember no matter what your setup is you need to push the cfm needed to make the power your after regardless of motor size.
the bigger the motor the easier to do.

try this for length p=850xed/rpm
p= primary header length( to the end of the cone collector)
850=half the speed of sound in ft/sec
ed= 180 degrees plus the number of degrees the exhaust valve opens before BDC.
for intake runner length a 10" runner will surport 10,000rpm.
so dont go too long in header lenght in relation to intake or itll work too far up the rpm range and that can make even a little turbo look like a monster.
try to keep the inside dia of the headers to port side and short,or you can start off 1/16 to an 1/8th bigger in pipe size then step it down to get the same thing but with two different points that it works which isnt a bad idea for a broader power range.
then again boost over comes all when you run past 20psi and more.
but this is the number one rule: THE MOTOR DESIDES WHAt YOU GET NOT YOU.

[Lith]

split pulse can improve response but kills horsepower.
and well designed exhaust open scroll turbo will perform better all round.

if you want good response and power then open scroll, remember when doing a pulse tuned exhaust you increase the turbine back pressure that's why you gain a little more response,back pressure hurts power.

Hi Steve, thats quite interesting.

What is it about split pulse housings that can kill horsepower?

Do you have any theories on that thread I linked to where a chap I know with a 300ZX swapped from a single entry turbine housing to twin scroll, with modifications to manifold to suit ended up with both better power and better spool?

[Bazda]

I like the twin scroll idea.
Seems to work well and I know alot of dads Race mates who are using their cars for track use the twin scroll method.

One of his mates has a t04z with a split pulse exhaust housing, something like a 1.0 a/r. maybe bigger I cant remember. With really long manifolds! Basically feels like it has zero lag which is crazy. Makes over 600hp as well. This is all done on a 4 cylinder SOHC with something around the 2.3L region.

[strx7]

long runners is where its at IMHO, if i had the space I'd have a full extractor type set up before the turbo.

[steve murch]

split pulse can improve response but kills horsepower.
and well designed exhaust open scroll turbo will perform better all round.

if you want good response and power then open scroll, remember when doing a pulse tuned exhaust you increase the turbine back pressure that's why you gain a little more response,back pressure hurts power.

Hi Steve, thats quite interesting.

What is it about split pulse housings that can kill horsepower?

Do you have any theories on that thread I linked to where a chap I know with a 300ZX swapped from a single entry turbine housing to twin scroll, with modifications to manifold to suit ended up with both better power and better spool?

none of this is a theory, its well documented threw people like SAE and Owens developments in England who build allot of the turbos for WRC and they detest the split pulse for making power.( feel free to question these people )
the problem is the divider cuts off nearly a 1/4 of the feed to the turbine wheel thrus increases back pressure reduces horsepower.
as for what your mates done from memory the old zed ran a split pulse manifold and open scroll hsg so with what hes done with mods to which i gather is extensive porting hes picked up performance as the stock setup was very poor to start with.
and if what Barry has written above if hes talking about mike delmonts bmw, i know for fact he doesn't run a split pulse turbine as i helped do his last setup to which feel free to ask mike but im sure your dad knows how to get hold of him.
if its not him and its a 2.3 pinto they love big turbos and responed well wether its a split or open, kane scotts merker is a prime example of that.
i apologise is either of above is wrong barry.
also going to any increase in displacement will improve response thats why its done ( cant bet more cub's ) since your making more exhaust energy it goes hand in hand.
there is allot of people who use pulse tuned headers and get good results,im talking about making more horsepower and still have response.
the motor that barry's dad had to rebuild again( his dad knows why) for a very good mate of mine was changed from split to open brought boost on 1000rpm sooner and picked up a good increase in torque.
as with above long runs can make you more power thats why its done but generaly they arent split pulse and still the tuned length is worked out in relation to whats needed, cams head flow compression intake etc etc all come into it.
so i guess its what works best for you and if you get the numbers then its well worth doing.

[Bazda]

split pulse can improve response but kills horsepower.
and well designed exhaust open scroll turbo will perform better all round.

if you want good response and power then open scroll, remember when doing a pulse tuned exhaust you increase the turbine back pressure that's why you gain a little more response,back pressure hurts power.

Hi Steve, thats quite interesting.

What is it about split pulse housings that can kill horsepower?

Do you have any theories on that thread I linked to where a chap I know with a 300ZX swapped from a single entry turbine housing to twin scroll, with modifications to manifold to suit ended up with both better power and better spool?

none of this is a theory, its well documented threw people like SAE and Owens developments in England who build allot of the turbos for WRC and they detest the split pulse for making power.( feel free to question these people )
the problem is the divider cuts off nearly a 1/4 of the feed to the turbine wheel thrus increases back pressure reduces horsepower.
as for what your mates done from memory the old zed ran a split pulse manifold and open scroll hsg so with what hes done with mods to which i gather is extensive porting hes picked up performance as the stock setup was very poor to start with.
and if what Barry has written above if hes talking about mike delmonts bmw, i know for fact he doesn't run a split pulse turbine as i helped do his last setup to which feel free to ask mike but im sure your dad knows how to get hold of him.
if its not him and its a 2.3 pinto they love big turbos and responed well wether its a split or open, kane scotts merker is a prime example of that.
i apologise is either of above is wrong barry.
also going to any increase in displacement will improve response thats why its done ( cant bet more cub's ) since your making more exhaust energy it goes hand in hand.
there is allot of people who use pulse tuned headers and get good results,im talking about making more horsepower and still have response.
the motor that barry's dad had to rebuild again( his dad knows why) for a very good mate of mine was changed from split to open brought boost on 1000rpm sooner and picked up a good increase in torque.
as with above long runs can make you more power thats why its done but generaly they arent split pulse and still the tuned length is worked out in relation to whats needed, cams head flow compression intake etc etc all come into it.
so i guess its what works best for you and if you get the numbers then its well worth doing.

Interesting. He told me last time I talked to him he was running a split pulse :S.
Must of said the wrong thing I guess.

I see him every weekend down at the workshop, I will ask him again.

[bbq1988]

Cheers for the info guys,

After finding out a price for the HX40 i think i will be giving it a miss and going with a Masterpower T64 from barry as its about 1/2 the price, the Holset takes up a good quarter of my budget ($2600 at trade price ), without the manifold/wastegates

I Was considering a DSR/DPR/KKR Turbo but after one of my friends having one of Al's DPR Turbos fail after 3 months on the car i wont be going down that track.

[steve murch]

split pulse can improve response but kills horsepower.
and well designed exhaust open scroll turbo will perform better all round.

if you want good response and power then open scroll, remember when doing a pulse tuned exhaust you increase the turbine back pressure that's why you gain a little more response,back pressure hurts power.

Hi Steve, thats quite interesting.

What is it about split pulse housings that can kill horsepower?

Do you have any theories on that thread I linked to where a chap I know with a 300ZX swapped from a single entry turbine housing to twin scroll, with modifications to manifold to suit ended up with both better power and better spool?

none of this is a theory, its well documented threw people like SAE and Owens developments in England who build allot of the turbos for WRC and they detest the split pulse for making power.( feel free to question these people )
the problem is the divider cuts off nearly a 1/4 of the feed to the turbine wheel thrus increases back pressure reduces horsepower.
as for what your mates done from memory the old zed ran a split pulse manifold and open scroll hsg so with what hes done with mods to which i gather is extensive porting hes picked up performance as the stock setup was very poor to start with.
and if what Barry has written above if hes talking about mike delmonts bmw, i know for fact he doesn't run a split pulse turbine as i helped do his last setup to which feel free to ask mike but im sure your dad knows how to get hold of him.
if its not him and its a 2.3 pinto they love big turbos and responed well wether its a split or open, kane scotts merker is a prime example of that.
i apologise is either of above is wrong barry.
also going to any increase in displacement will improve response thats why its done ( cant bet more cub's ) since your making more exhaust energy it goes hand in hand.
there is allot of people who use pulse tuned headers and get good results,im talking about making more horsepower and still have response.
the motor that barry's dad had to rebuild again( his dad knows why) for a very good mate of mine was changed from split to open brought boost on 1000rpm sooner and picked up a good increase in torque.
as with above long runs can make you more power thats why its done but generaly they arent split pulse and still the tuned length is worked out in relation to whats needed, cams head flow compression intake etc etc all come into it.
so i guess its what works best for you and if you get the numbers then its well worth doing.

Interesting. He told me last time I talked to him he was running a split pulse :S.
Must of said the wrong thing I guess.

I see him every weekend down at the workshop, I will ask him again.

mikes a nice guy but wont admit to outside help from others,when i saw his last setup only making 440hp there was many things wrong with it so i did what i thought would fix it and it did getting him 680hp?
somewhere around there but the tune on the car was realy bad,it was over 1090 degrees c on boost!!!, its no wonder it feel flat at 4500rpm and lost 150 ft/lb of torque after that regardless of all the cams he had done to try and fix it.
he also runs launch control, flat shift.traction control( two switch on the autronic) and any other control he can find which makes good for low threshold point.
and being a circut car when you spend 80% at WOT lack of response isnt normaly a problem regarless off turbo size or header design

[Lith]

none of this is a theory, its well documented threw people like SAE and Owens developments in England who build allot of the turbos for WRC and they detest the split pulse for making power.( feel free to question these people )

I wasn't talking about the single being better than split pulse being a theory, I was asking why the guy with the Z got gains. It was a twin turbo Z that was converted to single turbo - if you read the thread it always had custom manifolding for the turbo setup, he tried 2/3 single scroll turbos on it and never got a satisfactory result.... went to a twin scroll one and all his problems went away.

the divider cuts off nearly a 1/4 of the feed to the turbine wheel thrus increases back pressure reduces horsepower.

Yeah thats the bit I was always dubious of, I would love to have access to such things to play around with - now there are a few people I find very credible completely contradicting each other haha. Most TS setups I have READ (yes, not experienced...) about have dropped turbine pressure and been able to take more timing. I know only one person in real life who has done the change from twin to single scroll and that was also his experience which did sway me a bit, I have to admit.... though have noticed things like the TR30R and IHI RX8 seem to come in very fancy looking single entry layouts.

So much to learn....

[steve murch]

none of this is a theory, its well documented threw people like SAE and Owens developments in England who build allot of the turbos for WRC and they detest the split pulse for making power.( feel free to question these people )

I wasn't talking about the single being better than split pulse being a theory, I was asking why the guy with the Z got gains. It was a twin turbo Z that was converted to single turbo - if you read the thread it always had custom manifolding for the turbo setup, he tried 2/3 single scroll turbos on it and never got a satisfactory result.... went to a twin scroll one and all his problems went away.

the divider cuts off nearly a 1/4 of the feed to the turbine wheel thrus increases back pressure reduces horsepower.

Yeah thats the bit I was always dubious of, I would love to have access to such things to play around with - now there are a few people I find very credible completely contradicting each other haha. Most TS setups I have READ (yes, not experienced...) about have dropped turbine pressure and been able to take more timing. I know only one person in real life who has done the change from twin to single scroll and that was also his experience which did sway me a bit, I have to admit.... though have noticed things like the TR30R and IHI RX8 seem to come in very fancy looking single entry layouts.

So much to learn....

changing from a twin to a single is going to make it more responsive regardless since you now have twice the exhaust flow feeding one housing even being split pulse also the single hsg will be effectively smaller in area over the twins.
the turbine scroll design is another story all together and plays a big part in response and backpressure,you cant really compare the tr30r to the rx8 there totally different from each other for what they were designed for, the tr30r is rated max to 560hp and only afew wrc teams used it.
i have a bunch of prodrive wrc impreza turbos here to do for overseas customers and theres differant again,everyone has there theories of what works best