Hi...

Anyone have any hints on how to ground Wastegate control "F2" on a 749ECM with $58 code Eprom above, lets say, 140kPa. Planning on using the wastegate control function to activate a second fuelpump at a certain boost level.

or any other ideas how to activate it via the ECM, otherwise I'll have to buy a boost switch......

/N.

 

I just use an adjustable Hobbs Switch.
A search at like TruboBuick.com should turn up a NAPA number for one.

 

The ECM logic is "inverted" when it comes to wastegate control. In other words, the wastegate line is "active" at low pressures and "inactive" at higher pressures. (Just the opposite of what you want.) Although I haven't completely verified my thinking here, my assumption is that the wastegate defaults to an "open" state when the ECM line is inactive (or when the wire/solenoid is disconnected from the wastegate)...?

Two possibilities come to mind for going the ECM-based route. First, it looks like it would be possible to change one byte in the original $58 code and rescale the table at $3E6 to use boost instead of TPS to get something like what you want. This would also require quite a few additional calibration changes to get the rest of the wastegate control logic out of the way. Or, since we have the ability to modify $58 code at will, we could make a source code change! The calibrations at $3B3/$3B4 could be reused as a MAP hysteresis pair to trigger the output.

Let me know if you're interested in either option.

 

Hobbs switch sounds easy/simple.

I dont have the knowledge of doing source code changes yet......but If someone can do it and check on a ecm bench, it would be great!

I will order the xtra fuelpump today.

Can the F2 handle to ground a xtra relay?

 

I can make the source code changes to $58. I think you were one of the few people testing my "$59" WBO2 patches. Would you prefer the changes are made to an original copy of $58 or to the $59 code? I'm pretty sure I have a copy of the source code before the expansion to the 256k chip, WBO2 changes and V8 EGR fixes. Let me know what you want and I'll put together the code and test on the bench.

Are there any other qualifiers you'd like in the new logic? Modifications based on coolant, TPS, MPH, etc.....? We can do whatever you want while we're in there!

I'm not certain of the output specifications of the ECM. However, I would imagine you could use any existing ECM-controlled solenoid as a baseline. Check the impedance of something like an EGR solenoid (which should be pretty close to what was used on the wastegate) and compare it to the relay you want to drive the second pump. Ideally, your relay will have an impedance greater than or equal to the EGR solenoid. If the relay's value is quite a bit less, you might run a risk of cooking the ECM's output driver......

 

thx!

A MAP value to enable F2 output will work for me. I'm using a modified $58 code for now, I can send you a copy if you like?

I'm planning on using a regular power relay, I will test this week how much current it needs, maybe it would be "safer" to use a hobbs switch, I mean my ECM is already powering 8p/h injectors.......... and I dont have any spare ECM............

/N.

Looking at Ludis page, it seems like the same circuit in the ECM is also powering TCC/Ac relay so if its up to power those things it should handle a xtra relay and a small light/diod? or am I missing something............ RBob, Grumpy?

 

Any of the ECM quad driver outputs will drive a standard GM relay, such as that used for the fan, A/C compressor, or fuel pump. Just use that relay (each of those functions use the same part# relay) and it'll work. Also makes it easy to carry a spare.

RBob.

 

Has the $58 code you're running been heavily modified? It takes some time to go through the process of disassembling a *.bin file to make it so it can be changed and reassembled in the source code domain. If you don't mind, shoot me a copy along with any information on what you've changed and I'll see what I can do. In the event you're running Grumpy's $60 code, we'll want to talk to him to make sure this change meets with his approval.

 

thx..

Will send my current bin tomorrow, but its no hurry fixing it........

Just found water in my oil so I have started tearing it down

/N.

 

Ok, any news? Got my new fuel pump, and I started to put together the engine again........

/N:

 

Modified .bin is on it's way to you now. Let us know how things work........

 

adjustable hobbs switch connected to what?

 

solenoid