2 step tuning - back pressure an issue?
02-21-2015, 06:37 AM
#1
2 step tuning - back pressure an issue? Was messing around trying to build some boost, and I have 11.8psi springs in the wg's. With the 2 step engaged and the engine/turbo developing around 7-8 psi, all off a sudden I hear popping and I momentarily lose some psi but it climbs again. I'm assuming the wastegates are cracking open. But my question is, is it due to backpressure or the normal opening of wastegates? I wasnt sure if there was any kind of backpressure at the 2600rpm step limit.
What else can I do to get more boost w/o getting into CO2 or using heavier wg springs?
What else can I do to get more boost w/o getting into CO2 or using heavier wg springs?
02-22-2015, 12:10 AM
#4
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Was messing around trying to build some boost, and I have 11.8psi springs in the wg's. With the 2 step engaged and the engine/turbo developing around 7-8 psi, all off a sudden I hear popping and I momentarily lose some psi but it climbs again. I'm assuming the wastegates are cracking open. But my question is, is it due to backpressure or the normal opening of wastegates? I wasnt sure if there was any kind of backpressure at the 2600rpm step limit.
What else can I do to get more boost w/o getting into CO2 or using heavier wg springs?
What else can I do to get more boost w/o getting into CO2 or using heavier wg springs?
Yes you will have some backpressure in the exhaust even on the 2 step. It will be lower than the boost pressure so 3-4psi of backpressure is possible.
The popping could be a rich or lean condition or could be popping out of the exhaust from to much timing cut if your using that. You can't go by the a/f ratio when your on the 2 step. Generally a pop back through the intake is a lean condition. Popping out of the exhaust is timing or rich condition. Raise the 2 step rpm if you can and see if it generates more boost. Verify the tune to make sure it's right.
02-22-2015, 05:45 AM
#5
Yes you will have some backpressure in the exhaust even on the 2 step. It will be lower than the boost pressure so 3-4psi of backpressure is possible.
The popping could be a rich or lean condition or could be popping out of the exhaust from to much timing cut if your using that. You can't go by the a/f ratio when your on the 2 step. Generally a pop back through the intake is a lean condition. Popping out of the exhaust is timing or rich condition. Raise the 2 step rpm if you can and see if it generates more boost. Verify the tune to make sure it's right.
The popping could be a rich or lean condition or could be popping out of the exhaust from to much timing cut if your using that. You can't go by the a/f ratio when your on the 2 step. Generally a pop back through the intake is a lean condition. Popping out of the exhaust is timing or rich condition. Raise the 2 step rpm if you can and see if it generates more boost. Verify the tune to make sure it's right.
But wouldn't a wastegate start to open anyway with 7-8psi if I had an 11.8 spring in there?
02-22-2015, 10:38 PM
#6
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Thanks Dustin. Its the normal popping like a lot of turbo cars I hear with gates vented to the atmosphere. Timing dumps to 5* once the engine gets to 1psi and I have fuel set to a fixed amount (80lbs/hr). Anymore fuel and I cant build as much boost. Timing I have a little more leeway with.
But wouldn't a wastegate start to open anyway with 7-8psi if I had an 11.8 spring in there?
But wouldn't a wastegate start to open anyway with 7-8psi if I had an 11.8 spring in there?