ECM - 5 Volt Feed

[Jerryl]

Some of you experts can probably answer this. I was thinking . . . Lots of the sending units for pressure readings run off a 5V feed.

I know that the ECM has a good circuit for 5V feed and you can “tap into". There is also one on the PL.
If you use PL for logging , you may decide to add: oil pressure, fuel pressure, alky pressure, additional IAT.
So the question is: What is the circuit capacity of this ECM 5V feed as in . . . . How many sending units can you really run off this circuit before **** blows up?

 

[karolko]

Subscribed

 

[BRAD_PADGETT]

Clean 5 volt power on circuit c14. This is where my three bar MAP sensor now gets clean power, Brad

 

[TurboBob]

depends on the sensors....

The 5v output on the PL is the same as the TPS stuff, but the wireing in the PL cable is really small. I would wire no more than one sensor to the PL 5v. I would add no more than 2 to the TPS.

(just guesses on my part though)

Bob

 

[aminga]

I drive the MAP off the ISAC and the pressure transducers are plugged up to that circuit. I think that makes the TPS the only thing on the 5V ecm buss. WOnder if that's why the factory used the 5V IP feed for the MAP?

 

[TurboDave]

That raises an interesting question. When one is setting the 5v reference level on the Powerlogger's F3 screen, which value should we use? The 5v at the C14/TPS, or the 5v seen on the PL's analog block???

 

[BlackBandit]

Good question. I don't know the answer to the stock ECU's limits for powering sensors but if one wanted to add more sensors they could add a constant +5VDC power supply to power them easy enough. The ECU only needs to see the signal voltage.

 

[HighPSI]

Why aren't you guys using the 12volt transducers that have 0-5 volt outputs? Caspers has them in stock. We use them on the XFI's with a harness that plugs into the EGR plug.

 

[Jerryl]

Why aren't you guys using the 12volt transducers that have 0-5 volt outputs? Caspers has them in stock. We use them on the XFI's with a harness that plugs into the EGR plug.

Simple; Because that would be way too easy! LOL!!!

Seriously, I am trying to figure out this junk on one of the cars.
I am soooo LOST with it, but, that’s another thread. . . . . This is what started me thinking.

 

[Jerryl]

Good question. I don't know the answer to the stock ECU's limits for powering sensors but if one wanted to add more sensors they could add a constant +5VDC power supply to power them easy enough. The ECU only needs to see the signal voltage.

Yeah, saw a few on Evilbay . . . . just not sure how accurate/stabile they are.

 

[Daniel Jost]

I cant see there being much of an issue with running even 3 or 4 more sensors on the original 5v circuit. You are adding very minimal load to the circuit since the ECM is only using it as a reference voltage, it's not using it to physically control anything. I guess you would have to see what type of current each transducer draws to make sure there isn't for some reason a high current transducer.

My .02, Dan

 

[hootowl]

I drive the MAP off the ISAC and the pressure transducers are plugged up to that circuit. I think that makes the TPS the only thing on the 5V ecm buss. WOnder if that's why the factory used the 5V IP feed for the MAP?

The 5V IP feed is generated in the factory boost/tach gauge in the dash speedometer cluster. This 5V power has nothing to do with the ECM as the ECM does not sense the boost pressure. It is used to power the stock 2-bar MAP for the factory boost gauge. Any sensor using this 5V source would be less accurate than a sensor powered by the 5V generated in the measuring device (ECM, PL, etc.)

Mel

 

[BlackBandit]

Jerryl. As long as you have enough voltage a regulators output shou,ld be constant. A 5 vdc regulator shoud put out 5vdc whether the input is 8 vcd or 15 vdc. (assuming it can handle the load.) I don't know what you've seen on ebay but if it's a regulator it should work. Think about your alternator. It's up to speed the only thing that changes it's voltage is if the load exceeds it's power capabilities. Also, as long as the supply voltage is contant for things like our maps and such that is what's important. Whether it's 5.2vdc or 4.8 vdc if that voltage doesn't change then our tune won't change.

 

[aminga]

The 5V IP feed is generated in the factory boost/tach gauge in the dash speedometer cluster. This 5V power has nothing to do with the ECM as the ECM does not sense the boost pressure. It is used to power the stock 2-bar MAP for the factory boost gauge. Any sensor using this 5V source would be less accurate than a sensor powered by the 5V generated in the measuring device (ECM, PL, etc.)

Mel

I know all of this that's why mine is powered off the ISAC. Besides It's only inaccurate if your Dash feed doesn't produce close to 5V last time I measured the 5VDC dash feed was 5.01V on my car