I just want to learn something about the tuning that goes on when it comes to people saying that they have a 91 octane tune and a 110 octane tune. This is on the same car.

My question is how does the ECU know when to switch between one and the other? Do you have to have a switch or piggy or what?

WADAD

 

Usually done using an S-AFC, etc. You just press the button for which one you want, I believe.

 

Oh Ok

I just notice the EVO guys always talking about have a racegas tune and a 93 octane tune... JUst wondered how you would switch from one to the other? Especially since when you get to E on the gas gauge there is about 1-2 gallons of gas left.

WADAD

 

Just install the appropriate octane and then press the appropriate button on your doohickey, as I understand it...

 

Simple enough

WADAD

 

A lot of guys have two tanks, one for day to day use and one in the trunk for track days.

 

I have to agree with DJ on this one... they have some type of PB or standalone that lets them switch their boost and fuel curves, and when they are driving they are on one, when they take it to the track and put some 104 in the tank they change the settings.

 

A'pexi S-AFC have no switch mode for octane. I'm not sure if E-manage have some sort of "profile" saves between modes.

When there is higher octane, the ECU usually advances its own timing conservatively like 1-2 degrees.

 

Baha is that true of the 4G94 lancers too? Would our ecu react to higher octane levels also?

WADAD

 

All ECU should advance timing to a certain extent.

+100 octane for NA = the ecu will probably treat the gas as if it was 93.
+100 octane for FI = the ecu is more prone to advance a bit more, depending on injector load before fuel cut and knock. There are more checks and balance.


BTW: for complete stockers, the ecu will advance timing, but all the factory's checks and balances for noise and air pollution would damper any performance notices. Thus, it feels like it has no effect.

 

If that is true then that would refute what people say about running higher octane gas making no difference to performance.

Isn't the whole premise of the PB's is to advance timing to take advantage of higher octane and no detonation?

BOT
How far can the timing be advanced when running some race gas compared to the stock ecu doing the 1-2 degrees like you said?

WADAD

 

I see you edited in answering one of my questions.

WADAD

 

Yes. People bellyache on this too much. If all gas were the same, then, I dare any DSM'ers, EVO, ITR, SI, and Vette owners to fill their entire tank w/ 87. Put their money where their mouth is . . . just forget what the manufacturer's reccomendation. Otherwise, they should shut up, because they don't practice what they preach.

It's a short cut on tuning, relying on others to do it for you. If a person can do, there is nothing wrong w/ self-tuners.

I don't know. I should have learned this during my days working on carby.

I do know a person cannot advance more than 10 degrees - absolute crazy timing. Computer timing is different than manually doing it.

 

i think the emanage can switch between maps, if you have your laptop hooked up you could save different ones. (i think)

 

most use different maps that they can load into their AEM, E-manage, etc. Some that have AFC's mark down tuning locations so that they can adjust the knobs back and forth. This is how they "switch tunes"... it's very simple.

Advancing timing depends on components of the car, engine temps, intake temps, and fuel for the most part. The faster you can disipate heat(aluminum parts)... and the cooler your intake charge... and the cooler your exhaust temps... and the higher your resistance to detonation(higher octane resists spontanious burning/detonation)... then the more you can advance timing. Eventually while advancing timing you'll get pinging/detonation or high temps. This is your peak point and you then retard things about 2-3 degrees from there to give you a safety cushion.

When i say safety cushion its kindof misleading as if any of the variables change you could detonate and destroy the engine... this is why people tend to keep setups constant and the fuel as high in octane as possible when working on this edge. For daily driving you pull about 5 degrees out of your tune done on your gas of choice(ie: 87 or 91)... agian then you keep with that constant so you can stay safe and the 5 degrees give's you a better safety zone incase you get some bad gas or it's hotter outside(higher intake/exhaust temps).

Hope this helps you some.