tnning twins
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from what I understand on the LBZ/LMM trucks you can pretty much run the vanes wide open, or very close to 0% once the big charger spools. The LLY's are different, so like I said the LBZ thing is just what Ive heard. IdahoRob would know best
ben
ben
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1,957 Posts
The 'theory' behind tuning twins focuses around putting both chargers in their efficienty range. This means having boost gauges between the big and little charger, and a drive pressure gauge behind the little charger at least.
What you're looking for is the sweet spot for the pressure ratio of each charger. A compressor map can be helpful for putting the theory together in your head. That compressor map is of a GT4202, you can see it's more comfortable working at a 4.5:1 P/R than the 4294. With a boost guage before and after the little turbo, a person can measure the P/R each turbo is operating at - and tune the wastegate or vane table to best target the sweet spot.
Vanes don't just open and close, they make a smooth transition with RPM and fuel to feed the big turbo while keeping the engine in boost. Likewise, wastegates can be adjusted to limit total orifice size and pop off pressure.
Of course this is a birds eye view and there are a lot more factors that go into twin sizing and tuning, but this might get the ball rolling in your head.
Nick
What you're looking for is the sweet spot for the pressure ratio of each charger. A compressor map can be helpful for putting the theory together in your head. That compressor map is of a GT4202, you can see it's more comfortable working at a 4.5:1 P/R than the 4294. With a boost guage before and after the little turbo, a person can measure the P/R each turbo is operating at - and tune the wastegate or vane table to best target the sweet spot.
Vanes don't just open and close, they make a smooth transition with RPM and fuel to feed the big turbo while keeping the engine in boost. Likewise, wastegates can be adjusted to limit total orifice size and pop off pressure.
Of course this is a birds eye view and there are a lot more factors that go into twin sizing and tuning, but this might get the ball rolling in your head.
Nick
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1,076 Posts
Cool thanks nick. Can I still use my edge insight as the boost gauge for the small turbo? I planed on getting a 2 guage pillar pod to put a boost gauge for the larger charger as well as one for drive pressure.
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1,957 Posts
Unlikely. Your Edge Insight will be out of range if used 'post small turbo'. I'd do a three gauge pillar with two boost gauges and a DP guage.
Nick
Nick
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