Twin Scroll Turbos

[Howling Mad]

I was reading through the "next big thing" thread and saw someone talking about twin turbos so that got me thinking. Why does no body use twin scoll turbos on our lc2 motors? I know the import people love them just curious why no body has tried one on our cars. I know there would have to be some custom work done, headers and such. Like I said just very curious.

 

[Mike Licht]

Because since the invention of the terry Houston downpipe and ease of install we are stuck in 3 bolt turbo land 4 bolts would make more power with better spool and you can use a spool valve with a twin scroll

 

[dr_frankenstein]

i went threw this awhile back, when i was building my own turbos before i knew about Brian being on key with modern technologys. I was trying all kinds of stupid stuff... ruined alot of v6's! ask charlie... he was around for the daily threads of scattered internals.

Twin scrolls dont have much effect on the buick with stock headers because we merge all of our exhaust into a single point.

the idea behind the twin scroll is it seperates the pulses of the engine (4cyl) so that there is no loss in energy in the exhaust. having 2 cylinders that are opposite of each other merged at a single point also helps with exhaust scavaging.

however, thats not to say if you had some bitchen headers that split the buick inhalf, you could use this type of technology. I think Donnie Wang is pioneering this use as we speak.

correct me if i wrong guys....

 

[Mike Licht]

while you are technically not wrong and the headers you speak of would be interesting, the twin scroll does open up things like this http://www.gtrpwr.com/showthread.php?t=1665 which I know for a fact was used on a TSO car with GREAT success to get a big turbo up fast.
Mike

 

[dr_frankenstein]

while you are technically not wrong and the headers you speak of would be interesting, the twin scroll does open up things like this http://www.gtrpwr.com/showthread.php?t=1665 which I know for a fact was used on a TSO car with GREAT success to get a big turbo up fast.
Mike

I have seen that and i would agree 100% that it could make a difference! little scroll on the street, huge scroll at the end of a WOT pass.

love it.

thanks for the heads up on how the big boys are playing..... looks like i got a credit card to ruin.

 

[Reggie West]

That would be interesting.

 

[Howling Mad]

i went threw this awhile back, when i was building my own turbos before i knew about Brian being on key with modern technologys. I was trying all kinds of stupid stuff... ruined alot of v6's! ask charlie... he was around for the daily threads of scattered internals.

Twin scrolls dont have much effect on the buick with stock headers because we merge all of our exhaust into a single point.

the idea behind the twin scroll is it seperates the pulses of the engine (4cyl) so that there is no loss in energy in the exhaust. having 2 cylinders that are opposite of each other merged at a single point also helps with exhaust scavaging.

however, thats not to say if you had some bitchen headers that split the buick inhalf, you could use this type of technology. I think Donnie Wang is pioneering this use as we speak.

correct me if i wrong guys....

With out a slic there is a lot of room in front of the motor. It would be an odd design.

 

[Reggie West]

Donnie has been catching hell for it too.

 

[nocutt]

very, very old setup...

car is '88 chevrolet beretta with 3800S3 v6...(streetdriven)

currently the car is using two wastegates...
it is doable...

 

[Howling Mad]

Well that's just bad ass

 

[dr_frankenstein]

very cool man

 

[nocutt]

thanks guys...

 

[haywire4130]

I'd love to see more pics or video of your beretta, in my area (northeast) they are almost extinct! I had one for my first car, always thought it would be neat to transplant a turbo grand prix 3.1 into one and modify from there. Nice to see one survived and is no doubt pretty fast!

 

[nocutt]

I'd love to see more pics or video of your beretta, in my area (northeast) they are almost extinct! I had one for my first car, always thought it would be neat to transplant a turbo grand prix 3.1 into one and modify from there. Nice to see one survived and is no doubt pretty fast!

I lost my acct on youtube and have not uploaded anything of recent...but thanks, yes out here in LA, I used to see a couple back in the late 90s...then in the junkyard...I don't remember when I have seen either a GTZ or GTU...they are indeed rare or extinct lol

Regardless I think the science of twin-scroll is out there...the application has existed since the late early 80s...

 

[20psiofevil]

I have been thinking of doing something different. Think a 67/66 with h cover and twin scroll will be a very good match for my motor. One thing I heard about twin scroll turbine housings is a 1.10 ar is comparable to like a .81 in volume capability.

Anyone have input on sizing a ts turbine housing?

 

[nocutt]

I have been thinking of doing something different. Think a 67/66 with h cover and twin scroll will be a very good match for my motor. One thing I heard about twin scroll turbine housings is a 1.10 ar is comparable to like a .81 in volume capability.

Anyone have input on sizing a ts turbine housing?

I personally don't agree...A/R are weird especially when not within the same "family" of housing(s)...but I get what you maybe trying to say; is to move up an A/R. All things held equal; an open volute turbocharger of your choice can be up-sized at the turbine housing if you using a twin scroll...(seems to be a good rule of thumb...up to a point especially for street driven cars.

You probably cango to an engineering forum or turbo diesel forum to get more hits. I don't know, but I am sure their may be formulas for these floating around...

 

[87_we4]

My first car was a 89 gtu five speed with the high output 2.8

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[20psiofevil]

This is what I got from another website and is similar what precision explained to me...

"The twin scroll design came about from turbo diesels, which have huge exhaust pulses and very low operating RPMs... this means lots of slow but forceful pulses of exhaust spooling up the turbo. Keeping them seperate has proven to be beneficial this way. On a smaller displacement, higher revving motor the benefits are much less because you're dealing with smaller faster exhaust pulses which create an almost linear pulse on the turbine wheel.
The twin scroll turbos are spooling a bit faster, but its because the volume of the turbine housing is less due to the divider being there. Basically a .82 standard housing has more flow potential than a .82 divided housing because the division integrated into the housing uses up some of the volume."

 

[TTipe]

while you are technically not wrong and the headers you speak of would be interesting, the twin scroll does open up things like this http://www.gtrpwr.com/showthread.php?t=1665 which I know for a fact was used on a TSO car with GREAT success to get a big turbo up fast.
Mike

Hows about VGT (variable geometry)/VNT (variable nozzle) technology. During the developement of the intercooled cars (1985) we had one developement regal T with VGT. It was controlled by a Motorola controller. Honeywell also has a turbine wheel configuration where the exhaust gases don't make a 90 deg turn in the wheel pocket itself reducing temperature and friction. Since we don't create/destroy energy less gas expansion turns into heat and more of the energy is used mechanically . There are lots of improvements which can be made to the old style turbochargers.

 

[nocutt]

This is what I got from another website and is similar what precision explained to me...

"The twin scroll design came about from turbo diesels, which have huge exhaust pulses and very low operating RPMs... this means lots of slow but forceful pulses of exhaust spooling up the turbo. Keeping them seperate has proven to be beneficial this way. On a smaller displacement, higher revving motor the benefits are much less because you're dealing with smaller faster exhaust pulses which create an almost linear pulse on the turbine wheel.
The twin scroll turbos are spooling a bit faster, but its because the volume of the turbine housing is less due to the divider being there. Basically a .82 standard housing has more flow potential than a .82 divided housing because the division integrated into the housing uses up some of the volume."

I am not honestly convinced that all else been equal a .8X a/r divided tang turbine and a comparative similar .8X a/r undivided tang housing is any restrictive, I don't know how the volumes play as I have never measured one or seen one measured...but with everything turbocharger, there are simply many variables as you may know. Forget all the hullabaloo and hype the twin scroll is getting today; some of the benefits are actually scientific...the problem is with most things new, polarization occurs especially with market and misinformation involved. Pulse and constant pressure turbocharging are like apples and oranges really...but importantly we have to look at the whole system first and see where each is applicable.

Having said that...I put together my own turbocharger, first looking at the compressor wheel map and finding the best turbine wheel to support a twin scroll. Believe it is or not blade design affects the spool, choke characteristics...I was looking for a power band between 3k rpms to ~6k rpms and about 4XXhp, while still keeping the cam stock and converter stock. I don't race...my setup work very well for me.

I believe a lot of ppl tend to see artifacts of poor design when using the divided housing and then throw a blanket statement...the whole principle behind this is simply to increase the pressure differential across the turbine to create a more efficient turbocharger, while there are relatively many ways to do this...there are simply just a few that can do it effectively as a system...


PS: To quickly address your comment...i think Mazda may have employed this technology on gas application in the late 80s, but it used asymmetric volutes...and high revving engine irregardless. It is not simply the matter of quick spool, look at the system as a whole... case in point; I used a modified gn turbo in my first setup around '98...with this new setup I am still seeing boost threshold around the same rpm...what I have not said is that my turbocharger is much closer to the heads and a better design overall...the variables are just so many!!