Ryan K

iTrader: (11)

Ok, here is what I am trying to do.

I have a 98 w/a turbo. I wanted SD tuning due to the turbo and SD tunes transition into boost much smoother. So, I got a Fuel controller and the PCM is disconnected from the injector firings. Now that I am running with the SD tune, I am disconnecting the MAF and removing it from the system.

The question is, How can I tune the timing curves with out the MAF? Do I need to tune the VE tables for the PCM to Back calculate the GMS/cyl? Is there a calculation for GMS/Cyl? Can anybody help me figure this one out?

Also, does HP tuners and LS1 edit have the same axis for the timing curves? Edit's is GMS/Cyl vs. RPM.

Any help would be super!

Ryan K.

Gary Z

My understanding is that the PCM always calculates dynamic cylinder air and thus always has an entry into the spark table. If the MAF sensor is disconnected or not working then the calculation depends on the VE table (along with MAP, IAT and ECT). If your VE table is accurate, timing should be unchanged with or without the MAF. If your VE table is not dialed in then you need to keep timing on the safe side. You don't have an independent means for adjusting timing. I think you know all this. Your question interests me but I'm probably missing something.

Gary Z

I think I get it now. You have two controllers, your new fuel controller and the PCM controlling spark. They don’t directly communicate. The problem is how to get them to act together, to “track”. Or am I way off base?

Ryan K

iTrader: (11)

Yup, thats what I am going on.

Ryan

Gary Z

I just realized that you are doing SD tuning and you need to deal with two VE tables. They don’t share the same units but they should be linearly related. You need to scale one so it is always the same shape as the other. This all seems so inconvenient that it might outweigh any benefit of the separate fuel controller. Why can't your fuel controller also control timing? The advantages of a single integrated controller are significant.

Gary Z

When I first started thinking about your problem, I imagined a situation similar to an engine with a distributor and a carburetor. The apparent simplicity is attractive. With such systems control of timing and fuel seem separate. The analogy with your system breaks down because the old system is actually united by a shared physical world. Modern engine control systems rely on models, such as the VE table, that must be shared or duplicated if control of fuel and timing are separated. This necessity destroys the anticipated simplicity of two separate controllers.