Subject: Re: tuning and MAP questions by djxib on 2012/7/11 16:39:54
Quote:
tjpreul wrote: I bought the Procharger and unit off of ebay, it had the piggyback and software with it. This was a never installed unit that had been purchased in '06. However the Split Second p/n is FTC1-075. Which I don't think is available anymore due to the lack of sales. It is a fuel and spark management system. It has a vacuum hose that runs to the box, then sends the voltage to the factory ECU for the MAP reading. You set the output voltage by changing the value in the table to match the factory MAP at atmospheric pressure. By doing this it will compensate for having a forced induction engine. After that you have a table that you adjust the fuel levels with. According to them it is to trick the factory ECU to thinking it is at a different part of the set table. Then you are to readjust the fuel at that certain MAP point to even it out. Here is a link.
It is to add or remove fuel when and where it is needed. Then this table is an "overlay" of the factory table. My confusion is when I called Split Second they say to tune without the O2's. When I first start my car the AFR is reading high 13's to 14's. Then it drops to 10, which I think is when it goes to closed loop.
Yes, the signal wire from the MAP sensor is cut. The new signal is sent to the factory ECU from the piggyback. At 0 psi, I have them matched at 4.7v. When at idle (although not connected) the factory MAP has an output of 1.9v, and the piggyback has a 1.2v. This makes the factory ECU think it is running at a lower rpm, so then you can use the fuel table to adjust to the correct level.
OK - I read through the tech notes and I think I understand what it's trying to do. Basically without going into the stock ECU it tricks the ECU into a different part of the VE tables based on a modified MAP signal, and you can modify that signal using the Split Second tables.
From memory the 1-Bar and 2-Bar MAP sensors have some funky overlap at low voltage which can make idle and low speed tuning very hard. However, you have the overlay table that should help out.
I guess the piggyback expects that somewhere in your stock ECU table is an entry that will deliver the correct fueling for any given 2-Bar MAP signal and bigger injector combination.
You are going very rich (10:1) when in closed loop - are you seeing rich on both O2's (i.e. pegged above 900mv) in a scan? Or are you just watching a wideband sensor? Do you have an aggressive cam? I ask because I have a fairly aggressive cam and I get horrible split BLM's on my 92 that messes with the readings at idle, and you could chase your tail on a 'false rich' reading.
I havent tried disconnecting the O2's to force open loop (I do it in the ECM) but in general you want to run in closed loop for a while during datalogging because it can give you some very good initial idea how the engine is running (BTW - low MAP voltage means the ECU is looking up a lower KPa reading, not lower RPM).
I'm not sure if I am helping much because this approach is new to me too - however I do recommend that you capture some scans so you can see where the ECU thinks it's running rich or lean (you'll need it to be in closed loop for this).
If you have some datamaster scans I'd be happy to take a look.
