LE5 VVT OL vs. CL question

[patooyee]

I am building a turbo'd LE5 vehicle and and am considering running a carburetor for various reasons. Please don't let the whole debate of why EFI is better side track my main questions here. Please just assume I know the merits of EFI vs. carbs and have perfectly valid reasons to consider this. (I am by no means dead-set on it yet.)

If all I had to worry about was ignition, my answer on how to do this would be fairly straight forward. I would either run the stock ECM, disable all fuel-related functions and codes, and rock on or run an MSD box. The MSD is the more tried and true method, no big deal.

But ignition isn't all I have to worry about, there is also VVT. I know I can disable it. But what if I wanted to keep it? Here is what Alldata has to say about how the VVT functions:

CMP ACTUATOR SYSTEM OPERATION

The camshaft position (CMP) actuator system is controlled by the control module. The control module sends a pulse width modulated 12-volt signal to each CMP actuator solenoid to control the amount of engine oil flow to a camshaft actuator passage. There are 2 different passages for oil to flow through, a passage for camshaft advance and a passage for camshaft retard. The camshaft actuator is attached to each camshaft and is hydraulically operated to change the angle of each camshaft relative to crankshaft position (CKP). Engine oil pressure (EOP), viscosity, temperature, and engine oil level can affect camshaft actuator performance. The control module calculates the optimum camshaft position through the following inputs:

• Engine speed
• Manifold absolute pressure (MAP)
• Throttle position indicated angle
• CKP
• CMP
• Engine load
• Barometric pressure (BARO)

A locking pin keeps the CMP actuators in the parked position to avoid valve train noise upon engine start-up. The parked position is 0 degrees of camshaft actuation. The locking pin will release the actuator after the EOP is sufficient to overcome the locking pin spring pressure. The exhaust CMP actuators also have return springs. The return springs are necessary to assist the CMP actuators to return to the parked position due to the rotational inertia of the valve train components upon engine shutdown. The control module uses the following inputs before assuming control of the CMP actuator:

• Engine coolant temperature (ECT)
  
• Closed loop fuel control
• Engine oil temperature (EOT)
• EOP
• Engine oil level
• CMP actuator solenoid circuit state
• Ignition 1 signal voltage
• BARO

I think the bold bullet point means that VVT is only active in CL? But that doesn't make sense, does it? I've had someone tell me that they have seen their cam actuators active at WOT / OL during tuning, which would make more sense to me.

So would it be possible to run the stock ECM to control just ignition and VVT while allowing the dumb carburetor to control fuel? Obviously without controlling fuel the computer would always be in open loop.

I also know that Megasquirt 3 is an option for this but I have HPT, the stock ECM, and harness that I would prefer to utilize.

[cobaltssoverbooster]

Depends on the year of ecu you have. The newer ones have open loop catalyst positioning to help with preheat but after X sec of run time that system shuts down.
If you could fudge the ecu into a speed density mode and set the open loop factors to allow cam phasing then yes it would be active.
Most will still allow that function to run if the ecu is defaulted properly. The only version of ecu that i know for a fact stays active regardless of loop mode will not control your engine functions.

other problems you will have will be throttle setup(holley tps conversion does not work as a viable signal to ecu as ETC position, throttle pedal from original vehicle will also be required for ETP postion), vss replication, and fuel disable as mentioned before. Fuel settings are used as part of the load calculations system which may cause a problem with the Engine Load parameter mentioned from all-data.

Problem with MS3, unit must be of the Pro iteration in order to control phasing (either MS3 Pro or MS3 Old version with Pro Expansion Board), and it also requires destroying a set of cam phasers so you can input the correct data into the phaser control system. Same thing applies to Motec and Haltech units.

I do believe this is all possible just going to be a headache as you already know. Hardest parts will be Sensor Signal Replication for ETP, ETC, and VSS.

[patooyee]

Depends on the year of ecu you have. The newer ones have open loop catalyst positioning to help with preheat but after X sec of run time that system shuts down.
If you could fudge the ecu into a speed density mode and set the open loop factors to allow cam phasing then yes it would be active.
Most will still allow that function to run if the ecu is defaulted properly. The only version of ecu that i know for a fact stays active regardless of loop mode will not control your engine functions.

other problems you will have will be throttle setup(holley tps conversion does not work as a viable signal to ecu as ETC position, throttle pedal from original vehicle will also be required for ETP postion), vss replication, and fuel disable as mentioned before. Fuel settings are used as part of the load calculations system which may cause a problem with the Engine Load parameter mentioned from all-data.

Problem with MS3, unit must be of the Pro iteration in order to control phasing (either MS3 Pro or MS3 Old version with Pro Expansion Board), and it also requires destroying a set of cam phasers so you can input the correct data into the phaser control system. Same thing applies to Motec and Haltech units.

I do believe this is all possible just going to be a headache as you already know. Hardest parts will be Sensor Signal Replication for ETP, ETC, and VSS.

ECU is a 2006 E67.

I know this sounds crazy, but I would retain the stock TB and ETC. That eliminates the pedal sensing and throttle position sensing issues. I'm using 4t65e trans and the T42 TCM will still control that so VSS will be retained as well. Load calcs do present an issue I hadn't thought about yet though. Would affect transmission shifts points be affected by load calcs as well?

[patooyee]

Coming back around to this as parameters have changed. Transmission is longer computer controlled. I believe this should allow me to eliminate ETC completely. I only need to control ignition and VVT. All tables I see for that are air-mass vs rpm. This also eliminates VSS. Anyone disagree? Any other comments / advice?

I think the only sensors I should need are MAF for timing and VVT, MAP for boost, knock for retard, crank, and cam for rpm?

[nhanson]

Im running no VSS because I went from auto to manual and havent pinned it in yet. Everything works fine except my speedo of course.

[calgarylsswapper]

I'm also doing a 2.4L LE5 VVT Turbo project and I wonder why you would even be considering a carburetor.

Ive been tuning carbs since 1976 so i have a lot of experience with them. I can tell you the fastest ProMods have all switched to fuel injection from carbs. All the Turbo cars are FI. Even the Nitrous cars have gone FI. So i cant for the life of me think of any reason to use a carb. Just trying to understand your reasoning.

[patooyee]

Thanks guys. I decided to delete vvt to simplify things. I will be running microsquirt to control ignition with a propane mixer to supply fuel. After spending months trying to find info on trying to make the stock ecm work with little to no information I decided that I didn't have time to experiment with it and I know Ms will work.

[cobaltssoverbooster]

you will have poor performance disabling the VVT using microsquirt unless you take the time to correctly plot the cam position and make spacers to hold the cam phasers in the correct position. something i hope you thought about.

[patooyee]

I'm using a 2.2 head without vvt. It's getting deleted completely.

[cobaltssoverbooster]

You'll be fine then, good job thinking ahead