Twincharged Wastegate Plumbing

I have a dual port wastegate on a Twincharged project. Turbo feeding charger.

Should I plumb the lower half of the gate to the primary non compounded boost of the turbo and the upper side to the componded boost after the charger.? The upper side will be pwm controlled with a MAC valve for boost control. This would give hold the gate shut abilities... 

Or should the wastegate only see componded boost as it will have more control over the final boost made.?

Anyone forsee any potential issues? 

Sounds like you're running a sequential turbo setup? Thie is how a mk4 Supra is plumbed:

They're not doing anything special with the wastegate gas, so I'd say you should dump them both to screamer pipes for maximum performance.

Not sequential, compound. I'd look at what tractor pullers do.

GameboyRMH said:

Sounds like you're running a sequential turbo setup? Thie is how a mk4 Supra is plumbed:

They're not doing anything special with the wastegate gas, so I'd say you should dump them both to screamer pipes for maximum performance.

They are using MAP as reference for the WGs. I assumed WGs got pre throttle body boost only as a reference? 

Keith Tanner said:

Not sequential, compound. I'd look at what tractor pullers do.

I thought compound was sequential? Parallel would be switchng from one to the other and sequential was one blowing through the other in constant arrangement.?

Craigorypeck said:

Keith Tanner said:

Not sequential, compound. I'd look at what tractor pullers do.

 

I thought compound was sequential? Parallel would be switchng from one to the other and sequential was one blowing through the other in constant arrangement.?

Parallel typically means a standard "twin turbo" system where you have two identical turbos and one hangs off each bank.  I dunno what it would mean in a super+turbo twincharged application.

Sequential systems sound cool on paper, but to make them work right you need a lot of specialized parts and the complexity doesn't really seem to be worth it in general.

codrus said:

Craigorypeck said:

Keith Tanner said:

Not sequential, compound. I'd look at what tractor pullers do.

 

I thought compound was sequential? Parallel would be switchng from one to the other and sequential was one blowing through the other in constant arrangement.?

 

Parallel typically means a standard "twin turbo" system where you have two identical turbos and one hangs off each bank.  I dunno what it would mean in a super+turbo twincharged application.

 

Sequential systems sound cool on paper, but to make them work right you need a lot of specialized parts and the complexity doesn't really seem to be worth it in general.

 

Sequential means that one turbo comes on before the other - a small one for the bottom end and a big one for the top end. Compound means you have turbos feeding turbos. No fancy routing, just a big turbo ramming air into another one so they boost the boosts so you have many boosts.

Here's a production implementation of sequential turbocharging. I'm a little confused by the Supra diagram posted above having "wastegates" on the intake side. Note that this is operating as a compound system in the intermediate step.

In reply to Keith Tanner :

Thanks. You'd think I'd know that seeing as I'm building in that category.!

I'm gonna go with total compound boost as a reference. That way its relevant . 

Either way would work but one way might be more responsive than the other. The only reason why 'total boost' would work in this case is because your supercharger boost is fixed by pulley ratio. Otherwise you would HAVE to plumb it differently because if it were two turbos you could get the same final boost with different PR contribution from each turbo and have wildly different heat and response outcomes depending on which turbo was 'doing more' etc. 

Vigo said:

Either way would work but one way might be more responsive than the other. The only reason why 'total boost' would work in this case is because your supercharger boost is fixed by pulley ratio. Otherwise you would HAVE to plumb it differently because if it were two turbos you could get the same final boost with different PR contribution from each turbo and have wildly different heat and response outcomes depending on which turbo was 'doing more' etc. 

 

For sure, I'm on a more "linear" scale with this arrangement than with turbos.

IMHO, use the compounded boost to control the wastegate. After all, it's the boost that the engine sees that you're concerned about, not the boost the supercharger sees. 

whiskey_business said:

IMHO, use the compounded boost to control the wastegate. After all, it's the boost that the engine sees that you're concerned about, not the boost the supercharger sees. 

Exactomundo. 

Keith Tanner said:

No fancy routing, just a big turbo ramming air into another one so they boost the boosts so you have many boosts.

My favorite sentence of the day.