A new thought for twins - Compound Turbos? Maybe?

[TitaniumTT]

Originally Posted by antman0408

Boost Logic has been working on a kit for the supras, you should search supraforums and see what they have done or give them a call. They probably have the most knowledge of a compound kit on a gasoline engine.

Thanks Anthony, I'll do a little searching around.

Originally Posted by RotaryProphet

The big turbo sucking through a small turbo is the same as a big turbo sucking through an inch and a half inlet; the big turbo is going to pull vacuum on it as soon as it starts to spool, and then the smaller turbo is just a restriction.

What you'd want is a sequential system with a reasonably large turbo for the top end, and a small turbo to create boost down low; that's what I'm working on with my sequential controller. It uses electronic controlled valves to control the secondary turbo and the wastegate, and allows a small turbo to boost to say, 14 PSI almost immediately, and allows the big turbo to make as much boost as you care to let it when it spools. And since the wastegate is electronic, it doesn't even start to crack until the second turbo is at full boost.

Would you mind sharing your idea for this? This is something else that I'm considering. Without doing any math, the sizes that I'm looking at are GT25/28 for the small, and a GT3071-R for the large. My thoughts for this type of system are

Exhaust - an equal length mani, each with a wastegate and an internally gated turbo just to give the turbo the chance to vent out as much exhaust energy as possible. The two individual gates will plumb back into the exhaust AFTER the second larger turbo. The larger turbo is also internally gated.

Intake - First, I'm undecided if the intercooler will be a dual inlet or not. For simplicity and to give the first turbo the least amount of space to pressurize, I believe the turbo's will be merged as close to the first turbo as possible and an electonic cut-out will be utilized. So, the first turbo is plumbed strait to a merge collector. The second turbo is plumbed to the merge collector as well but inline is an electric cut-out to keep the first turbo from back-spinning the second. There also needs to be a vent to allow the turbo to spool without creating a TREMENDOUS amount of exhaust backpressure.

Control.... well I'll be using a Motec M800 so the control's are virtually limitless. I'm thinking there needs to be a 3d map setup such that when MAP = the charge pipe for the seconday turbo, the valve opens and the vent closes. Easily accomplishable. Two different WG controls but the closed loop being on the larger turbos internal gate and the WG on the mani's being run off duty cylce at a preset limit to control "absolute boost"

Thoughts?