I was reading this article



http://www.modified.com/tech/modp-09...n/viewall.html



and was curious if anybody has ran this type of system on their car. I assume you run 2 wastegates in a twin scroll too, right?

 

The sonata turbo is running a divided housing/ twin scroll turbo from the factory. I'm planning on using a twin scroll system as well when I upgrade my turbo.



Yes you do need two waste-gates as well as an extra waste-gate dump of course.

 

Twin Scroll turbo's have 2 exhaust routes "in", but only one outlet(exhaust). The wastegate should be 'shared' between both sides of the twin scroll, if it's not, you can end up bleeding down exhaust pressure from one half of the engine more than the other half and cause all kinds of problems!



Here's one example (Subaru Boxer engine)

http://www.airpowersystems.com/wrx/a...roll/turbo.htm

For rock steady boost control, the APS TSR 70 turbocharger is delivered complete with a competition, 44mm Tial vee band mount wastegate system. The wastegate is designed to divert a balanced flow of exhaust gas from each of the two exhaust gas routes in the APS up-pipe.

 

From what I've heard it's the other way around i.e. a single waste-gated manifold is harder to design and get working correctly. Doesn't using two waste-gates manage the boost better?

 

If you look at any of the factory twin scroll turbos (Subaru, BMW) they use a single wastegate. It's not that hard. Having 2 wastegates means more weight, size/packaging constraints, and synchronization issues



The usual way to run a wastegate on a twin scroll is to run two pipes to a *collector* that is a devided circle. The wastegate seals to the outer edge of the circle and to the line down the middle so there is no crossover there. Then a single wastegate vents both evenly.

 

hmm ... interesting. What's the reasoning behind using two waste-gates then? The handful of people I know with twin scroll setups all have two waste-gates.

 

In a "home built" system or cheaply made system, have to use 2 wastegates, as it is very hard to build the divided round pipe needed for a single wastegate, and I don't know of any place you could get one "built" as the bends/curves would application specific. It's not like you could buy divided round pipe (I've never seen it offered anywhere) and then bend it yourself, unless you've got a mandrel pipe bender in your garage. Heck I don't even know if it's possible to mandrel bend divided pipe without mucking up the divider between the 2 passages.



So if you're home building, or buying a turbo kit from a company that only makes a handful a year, yeah, you'll probably have 2 wastegates.



You don't WANT 2 waste gates though. You want the exhaust from both banks to route around the turbo equally. With 2 wastegates you've got the potential for one wastegate to open before the other, or have one open 75% and the other 50%, or worst case, one completely open and the other still completely closed. When you have a single wastegate, it's easy to figure out if it's opening too soon(not enough pressure, or slow pressure build to peak), or not opening soon enough or not opening completely(Overboost/too much pressure).



With 2 wastegates...which one is the problem child? You need to Sync them both very carefully. Make sure they both open the same amount @ a given pressure level. You need to setup both wastegates to make sure they start to open @ the same pressure level. otherwise you're wasting energy from half the cylinders. You also need to make sure they both open the same amount(distance or degrees) about every 2 psi, or again, you're wasting the energy from half the cylinders.



99% of the time Wastegates aren't light switches. They aren't just "OPEN" or "CLOSED"..they vary anywhere from fully closed to fully open, and anything inbetween. If those 2 wastgates aren't 100% in sync, you're wasting energy from half the engine.

 

Wow, thanks for the info. Will have to keep all that in mind when I go to do my build. Reason number one why I'm liking this site more and more over the other ones.



P.S. Gave you a couple rep points Random haha.

 

Just because this thread hasn't been derailed yet, I wasn't aware that random still posted. Hey dude!



What about an solenoid operated system? Iirc Nissan RB engines use a solenoid to control how much air the wastegate 'sees', so you could possibly set up a simple feedback system to keep both wastegates operating equally. It might be cheaper than messing around with sections of pipe.

 

When you say "solenoid"...do you mean to actually OPEN the wastegate, or do you mean to control the air pressure to the wastegate?

If you mean to OPEN the wastegate...that's gotta be one damn high temp solenoid! I can't say I've ever heard of a unit that could take Turbo/Exhaust heat and live for very long.

If you mean use the solenoid to adjust air pressure that the wastegate see's...yeah, you can do it that way, but you've still got to go through the trouble of syncing the 2 wastegates and how they respond to the pressure signal the solenoid sends them. If you had a way of adjusting the solenoid's...you could sync them that way, but that would be quite a feat to control 2 solenoid's to respond to x pressure in and get them to send x+1 to one wastegate and x-1 to the other wastegate.