Twin Scroll Turbos?? Monster Spool.. FACT or FICTION???
Nov 22, 2012, 01:20 PM
#256
http://www.youtube.com/watch?v=zDWA_4wpobc
This shows 2 advances. I am not tempted by the power of the Twin Scroll side.
BUT
I am tempted to put the TB pre turbo and let the turbo free rev in vacuum between shifts however. I mean it only made 1000whp per liter or so, and 80psi needs something to help it spool. There are SAE papers on this as well. The vacuum on the compressor is nothing new, but I know of ZERO people other than JR and I that have even talked about it. Anyone else?
1980 > most engines in 2010
This shows 2 advances. I am not tempted by the power of the Twin Scroll side.
BUT
I am tempted to put the TB pre turbo and let the turbo free rev in vacuum between shifts however. I mean it only made 1000whp per liter or so, and 80psi needs something to help it spool. There are SAE papers on this as well. The vacuum on the compressor is nothing new, but I know of ZERO people other than JR and I that have even talked about it. Anyone else?
1980 > most engines in 2010
I did some testing recently in addition to what we have learned with Jeff's drag car that leads me to the conclusion I was wrong.
A 1.15 T4 divided built 22.3psi of boost at 4500 vs a 0.82 T3 on the same motor and setup.
Comparing the 1.15 directly to a very similar build albeit with a 0.68 single scroll T4 showed equivalent spool but backpressure problems at high PR on the single scroll vs the twin scroll.
The main issue with people not seeing the results with twin scroll has been mismatched housings to turbos. The SAE paper that said a divided housing spools like its 60% of its size in an equivalent ope scroll is nearly exact.
1.15 x 0.60 = 0.69
It goes on to postulate that the housing can make 90% of the power for its size vs an open scroll.
1.15 x 0.90 = 1.03
Winning.
Aaron
Nov 22, 2012, 01:25 PM
#257
As far as factual data for response time I will have some in the next few weeks and months as I transition to a larger twin scroll setup on my car. I have a BW S360 with a 0.91 and 1.00 to try and if those arent quite what I want I'll order the 1.10 as well. It is only a 60mm inducer but it has a larger turbine than the 3794 I used last year so I am assuming I can get away with murder even on my large displacement, good VE, 2.4L.
We have also had a few Evos and STIs in lately with large twin scroll setups that I am going to post data from and compare to other cars with similar open scroll kits.
aaron
We have also had a few Evos and STIs in lately with large twin scroll setups that I am going to post data from and compare to other cars with similar open scroll kits.
aaron
Nov 22, 2012, 10:05 PM
#258
If only there were stainless steel twinscroll housings that could hold up better then the diesel cast iron stuff that is available. Even Ni-Resist would be better then what we have access to for the Garretts.
I think a lot of people thought poorly of TS not only because of sizing the hot side incorrectly, but also because there were several using TS turbine housings with open scroll manifolds getting junk results and saying the TS housings suck. There was also guys trying to use one wastegate, either only venting half the motor or teeing the separate runners together and then to the gate. Both of these situations kill the TS effect.
I think a lot of people thought poorly of TS not only because of sizing the hot side incorrectly, but also because there were several using TS turbine housings with open scroll manifolds getting junk results and saying the TS housings suck. There was also guys trying to use one wastegate, either only venting half the motor or teeing the separate runners together and then to the gate. Both of these situations kill the TS effect.
Nov 23, 2012, 09:00 AM
#259
Comparing the 1.15 directly to a very similar build albeit with a 0.68 single scroll T4 showed equivalent spool but backpressure problems at high PR on the single scroll vs the twin scroll.
The main issue with people not seeing the results with twin scroll has been mismatched housings to turbos.
The SAE paper that said a divided housing spools like its 60% of its size in an equivalent open scroll is nearly exact.
It goes on to postulate that the housing can make 90% of the power for its size vs an open scroll.
The main issue with people not seeing the results with twin scroll has been mismatched housings to turbos.
The SAE paper that said a divided housing spools like its 60% of its size in an equivalent open scroll is nearly exact.
It goes on to postulate that the housing can make 90% of the power for its size vs an open scroll.
It all revolves around the simple concept that a properly sized, more efficient collector design improves torque while minimizing power-robbing turbulence and standing waves simultaneously. It's a longstanding realization in the NA world that applies to turbo applications as well.
Keep us posted.
Nov 23, 2012, 11:56 AM
#260
If only there were stainless steel twinscroll housings that could hold up better then the diesel cast iron stuff that is available. Even Ni-Resist would be better then what we have access to for the Garretts.
I think a lot of people thought poorly of TS not only because of sizing the hot side incorrectly, but also because there were several using TS turbine housings with open scroll manifolds getting junk results and saying the TS housings suck. There was also guys trying to use one wastegate, either only venting half the motor or teeing the separate runners together and then to the gate. Both of these situations kill the TS effect.
I think a lot of people thought poorly of TS not only because of sizing the hot side incorrectly, but also because there were several using TS turbine housings with open scroll manifolds getting junk results and saying the TS housings suck. There was also guys trying to use one wastegate, either only venting half the motor or teeing the separate runners together and then to the gate. Both of these situations kill the TS effect.
The basic tenets of twinscroll are exactly that.
It all revolves around the simple concept that a properly sized, more efficient collector design improves torque while minimizing power-robbing turbulence and standing waves simultaneously. It's a longstanding realization in the NA world that applies to turbo applications as well.
Keep us posted.
It all revolves around the simple concept that a properly sized, more efficient collector design improves torque while minimizing power-robbing turbulence and standing waves simultaneously. It's a longstanding realization in the NA world that applies to turbo applications as well.
Keep us posted.
aaron
Nov 23, 2012, 02:25 PM
#261
Nov 24, 2012, 08:26 PM
#264
If done correctly, merging the paired cylinders does NOT kill the TS effect. The dyno plot from my car linked several times in the thread is a single wastegate TS manifold. As long as the paired cylinders are kept separate right up to the valve, the TS effect is still quite present.
I have to ask, has that divider actually held up? It looks too thin to hold up to the extreme heat it would see in that location.
Last edited by 03whitegsr; Nov 24, 2012 at 08:33 PM.
Nov 25, 2012, 06:23 AM
#265
^ Gotcha. I misunderstood your description, and yes, it's very similar to the stk turbine housing in execution. The divider is 16ga. 321 so it should be just fine. It's a new maifold design for me and all of it is 16ga. 321ss. I was going to pull the wg off and check the divider, as it has been on the car for the last 1,500mi. If it were mild steel or 304, the heat would definately make short work of it.
Nov 25, 2012, 08:23 AM
#268
Drifto, definitely curious as to how that divider holds up. I've been very curious to know if 321 can hold up in that situation or if inconel would be needed. What size gate are you using?
Aaron, something to consider, I think those turbos that use the throttle valve on the turbo inlet have special thrust bearing systems. The vacuum "pulls" on the compressor wheel and if the thrust bearing can't deal with that negative thrust force, it's probably going to cause problems. I can imagine controlling it might be tricky too.
Aaron, something to consider, I think those turbos that use the throttle valve on the turbo inlet have special thrust bearing systems. The vacuum "pulls" on the compressor wheel and if the thrust bearing can't deal with that negative thrust force, it's probably going to cause problems. I can imagine controlling it might be tricky too.
Last edited by 03whitegsr; Nov 25, 2012 at 08:28 AM.
Nov 25, 2012, 08:38 AM
#269
The early Buick T-Types had the TB in front of the Turbo, which worked fine as they were non-intercooled. Once you added 6ft of plumbing and I/C to them, the TB was relocated to the more conventional position, as it caused odd laggs in response to the throttle opening. With modern fuel injection, there may be ways to compensate for that.