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Discussion and questions related to the course Practical Reflash Tuning
While working on the file from my Opel Insigina OPC, I found 4 tables available as the main spark advance as it shows in the attached file.
Knowing that its a "V" type engine, would you please explain how these tables work and the correct way to optimize each one of them and if the same is applicable to all other V/H type of engines.
Appreciate your feedback
I'm assuming this is the 2.8 turbo but this applies to any dual overhead camshaft engine, turbo (like a GM 2.0T) or non turbo (like a GM 2.5). It does not apply to GM 2 valve engines (pushrod engine like in Corvettes and vehicles that use its small block engines) because the variable valve timing cannot control intake and exhaust valves separately. The VVT applies to intake and exhaust cam lobes equally. Here is my response:
Your engine has variable intake and exhaust cam shafts. The ECU interpolates among the maps according to the VVT position.
Intake min exhaust min means that your engine has the VVT locked at the 0 position. So your intake valve is at its most retarded position and your exhaust is at it's most advanced position. This is the baseline position when your engine starts and the hydraulic VVT isn't moving, or there is some kind of fault, or if the VVT maps are just set at 0 for your engine condition.
Intake min exhaust max means that your intake position is locked at the 0 position (most retarded) and your exhaust is at its most retarded position. In this condition the engine has overlap and low effective compression; it's basically a fuel economy setting.
Intake max, exhaust min means that your intake cam is at its most advanced and your exhaust cam is at its most advanced. This is a high effective compression ratio, high overlap condition. It's typically used in medium loads for fuel economy (internal EGR), and it's used at low speed/high load for more torque when your engine isn't making much boost.
Intake max, exhaust max is the max overlap position, with intake most advanced and exhaust most retarded. This is typically used to blow fresh air through the combustion chamber for scavenging in order to spool the turbo.
In the GM control system (not just GM really) there is a model of engine operation that includes volumetric efficiency. The volumetric efficiency , combustion speed, and other models interpolate according to the VVT position. So it's not just a spark thing, it's related to the airflow model which relates to the torque model and calculation for required fuel (the other tabs you see there).
Somebody somewhere probably has an interpolation Excel tool to help. Similar such tools are used for example on ford VVT engines. I would contact HP tuners and see if they can recommend anything to help. Make sure they know that you are NOT working on a V8. Otherwise, without some special method or Excel tool from HP tuners you are going to have to look at your VVT position in your datalogs and see which maps are closest. For example, if you go WOT at 3000rpm and you see your intake VVT is 30 and your exhaust VVT is 5, then it's probably Intake max, exhaust min condition that is closest.
Appreciate your extensive explanation, I shall update on the same once I get a reply from HP tuners.