alcohol maps in the 2.4L PCMs

[spyhunter]

I have a question for you people with the 2.4L. Have you ever wondered about the alcohol maps? Are they fully functioning? Is this some early GM flex-fuel implementation? Was this GM taking into consideration that people may be using alcohol cooling on the GM supercharger? Or was it GM knowing that E85 was coming out soon, but never finished testing on E85 at the time?

Potentially could we set that alcohol map for E85 settings, would the PCM "think things through" between the alcohol maps and the regular maps for a happy medium when you're going from E85 to regular pump gas?

Thoughts, ideas, comments, questions, inquiries, genius commentary is welcome.

I'm going to be doing an E85 tune in the next month or two, and am curious about these (alcohol) maps.

[SpdRcrZ]

I have no clue what the maps/tables are for, but I would like to find out.

[spyhunter]

DUM du DUM

[IanB]

Def. listening. If it is functional, you could use it as a race gas tune I would guess.

[redhotjamedjimi]

How would the engine be able to know that its such an high octane and switch over considering the Ve tables would be off.

?

[spyhunter]

How would the engine be able to know that its such an high octane and switch over considering the Ve tables would be off.

?

some of the little things we would like figured out. The only people I know that have access to deep dark secrets are the HP guys and GM. Anybody?

[spyhunter]

Def. listening. If it is functional, you could use it as a race gas tune I would guess.

Something like that for sure! It would be nice.

[Chris@HPTuners]

its a hack for the E85 stuff, your car needs a fuel composition sensor to take adavantage of the alcohol tables. Bottom line is if GM didn't calibrate it for alcohol forget about trying to make it work yourself, some of the options are compiled into the code.

[spyhunter]

That's really interesting, would be a nice option to play with.

So what you're saying is Chris is that it's somewhat incomplete in code as well as lacking of that fuel comp sensor? In essence a set of tables that have no use for us?

[Torg2000]

The L43 (S-truck) is calibrated for flex fuel.
The fuel composition sensor measures two different fuel-related parameters, and sends an electrical signal to the powertrain control module (PCM) to indicate ethanol percentage, and fuel temperature.
The fuel composition sensor has a three-wire electrical harness connector. The three wires provide a ground circuit, a power source, and a signal output to the PCM. The power source is vehicle system voltage (+12 volts), and the ground circuit connects to chassis ground. The signal circuit carries both the ethanol percentage and fuel temperature within the same signal, on the same wire. The composition sensor measures the ethanol percentage and fuel temp. The signal is both variable frequency and variable pulsewidth. The frequency of the signal indicates the ethanol percentage, and the pulsewidth indicates the fuel temperature. The output frequency is linear to the percentage of ethanol content in the fuel. The normal range of operating frequency is between 50 and 150 Hertz (Hz), with 50Hz representing 0 percent ethanol, and 150Hz representing 100 percent ethanol. The normal pulsewidth range of the digital pulses is between 1 millisecond (ms) and 5ms, with 1ms representing -40 degrees C, and 5ms representing 125 degrees C.

[imphat0260]

Vin code 5 (2200) would also be FLEX Fuel... (keep in mind, 2 Vin codes for 2200, 4/5)

[ksoggs]

so we can totally ignore the alc tables... without a sensor to activate those tables they are just lame ducks....

but now the Hi and Lo octane tables... (for PE and base) they are supposedly both used?? and the ECU inerpolates between them based on the knock learn. more knock, assumes lower octane so leans toward lo tables.

But i am told my engine, 2.4L twin cam LD9, does not support knock learn... or at least it does not allow you to display it in HPT.

I would like to know how exactly, if at all, it figures out the knock learn, and how i can monitor it so i know what timing it is using, so i can more acurately tune my car.