MTH - there was a HUGE thread debating the use of fuel of varying octane levels and the effects it can have on our vehicle...

You being a bunch of Engineers ( hopefully ) should be able to give us some useful insight about running the *wrong* grade of fuel in an internal combustion engine designed by automotive engineers ( hopefully ) to use a certain grade.

I would also appreciate information about the map changes made in the MTH software to run 94 Octane rated fuel in *my* car vs 91, or 89.
( as I drive 1000 miles if I can't get Sunoco 94 will my Car EXPLODE ! ok that might be extreme, i don't think it will explode but what will be the observed impact )
We have all heard the arguments that you need to run higher octane rated fuel in cars that have higher compression rations to avoid the Evils of early detonation, but other than those generalization everyone has an opinions.

I know I can't trust SOTP to tell me that my car is running better or worse... I can however *hear* things that migh indicate the all is not the *same* in Engine Land...

Is the ECU so sophisticated that you might not be able to hear the Ping or Knock you might have heard in older vehicles, because the engine management system adjusts timing etc... to *** the Ping in the But ?

I at least would appreciate any information you can provide to enlighten us

Thanks,

 

No, your car won't explode. The ECU will handle the lesser fuel; you'll just make less power (unless you are tracking the car, of course).
Cars won't ping like they used to because of the knock sensors. When they detect knock they retard the timing -- instantly.
Read Dr. O's article in this months MC2 to get more detail.

 

If I could find issues #3 i would :(

Thanks - But he's a Rocket Scientist not currently working for an Automotive manafacturer designing car engines... is he ;~/ ?

 

And your point is what?
Dr. O simply states the basics. And he did an excelent job of it.

 

What !
I have to have a Point ! ( what's this world coming to - where everything has to have relevance !!)
A point I could chose to put forth would be that I would like some Indisputable evidence put forth with supporting empirical data - Firmly defining "The way it is" . period...

What do you think, am i dreaming of a utopia that does not exist... i'll wake up any second

 

This is some data showing the timing from 91 vs 100 octane gas. It's a noticable difference.... I don't think I need 100, but 91 certainly blows chow.

Matt

 

Thank you Heir Dr. !
WOW - Empirical Data !
uh... WTF am i looking at here ???
The Axis aren't labeled - I have no idea what R2 11 - R9 Kw are ...

( I guess i'll have to wait till i get my copy of MC2 to get the rest )

( i hope you know i'm kidding here...)

 

The time axis can be thought of as RPM. The vertical axis is timing advance. Knock window is what the ECU uses to determin if knock is imminant or occuring.

Also, our cars look at each cylinder separatly, and controls timing retard on each cylinder separatly. So for these two runs shown, there are 8 timing curves!

The one with the 91 octane shows retard all over the place. The one with 100 octane, shows pretty much none.

Matt

 

Ugh, I guess I'll have to keep paying for that 93 octane fuel. I was thinking of stepping back to 91 to see if it made a difference in cold starts and that low rpm stumble that occurs for the first couple of minutes.

Were the stats shown obtained from a stock MCS or one with mods?

TIA,

Richard

 

but I've seen data from cars without mods, and from cars running 93. The cars are tuned so close to the edge, that there will be a bit of retard if it's warm outside and you floor it in first or second. More airflow in thrid may help keep it in check. Such is the life of a computer controlled highly strung motor!

Go ahead and do your tests. It may be that the improvements you get in other areas off-set the performance you sacrifice. No way to know without testing. After you know the trade off, it will be easier to make the decisions.

Matt

 

Were getting there... so the top Blue and Red lines are for Timeing advance/retatrd
The Red being 91 the Blue 100

On the lower half of the graph the 100 plots are all nearly one over the other -
Can i interpret this as - all the cyinders are running about the same with no significant timming differences between the cylinders
The Lower graph not Blue lines are all over the place ( relatively ) indicating a significant amount of timing adjustment is being made accross all the cylinders ?

Yes ?
( I'm trying to understand - cause I dont know...)
Thanks,
( I appreciate the additional technical data - so we have a better understading of WTH is going on in there...( engine)

So a statement to the affect that "My car runs just fine on 87 gas " means the engine is making adjustments to compensate for the fule being used and it still works acceptably.
Now the difficult part - do you *think* we could Feel the difference between these two fuels ?
Maybe if you are *really* in tune with your car ?

continuing on ad nausem - so the MTH load i am running today is supposedly *tuned* for 94 Octane ( Sunoco - ethanol blend ( good/Bad ) )
so the Factory ECU tunning is programed for 91 octane and your graph indicated that there are *issues* with 91 and the default maps -
That makes me wonder if the MTH maps are working 100% with the 94 octane ?
Maybe i should try running the 91 map with 94 octane fuel but again would i notice the difference :(

 

The top lines are the Knock Window values... They use the virticle scale on the right... See that the blue on is pretty much always 0? That means the ECU isn't detecting any knock.

The lower curvs are the timing advance, and go with the left verical scale. There are a lot more curves here, because there's one per cylinder. And yes, all four cylinders are running with the same timing for the 100 octane, and for the 91, each cylinder is being retarded independantly based on the knock sensor output. If you look at the points around 6 to 7 seconds, you'll see the 91 octane timing is over 10 degrees later than the 100 on one of the cylinders. Overall, the 91 looks to be 4 to 8 degrees retarded compared to the 100.

Matt

 

more answers beget more questions...

( I'm not trying to pick holes in anything with these questions )
Were these stats gathered with the car on a Dyno ?

Would the application of WOT ( to the Floor ) significantly effect timing changes the ECU would inflict in the engine vs. gradual throttle application ?

Can you fill us in on how the testing was accomplished. what steps or method acquisition tools were used to collect this data...

I am thinking of putting my car on the dyno to see how the *real* numbers compare with the numbers the GTech *toy* is giving me.
I might be able to collect data like this at the same time with a few *tools*
A buddy has the hardware needed to connect a PC or PALM to the ECU to watch/log some attributes, it might be useful / informative...

 

Bim-COM beta.

They were power runs on the street in 2nd gear on a freeway on-ramp. I was testing ICs

These were just two runs out of about 50 or so done to evalutat a bunch of IC configurations.

If you're at part throttle, there's nothing to worry about, because you're not going to be stuffing the cylinder anywhere close to what WOT does. So the charge heating under compression of the cylinder will be much less than for WOT, and no knock. Also, if you're at part throttle, and you want a bit more, you just push the peddle farther.

Matt

 

ok -

So this was a tiny bit of representative data gathered when you were doing some real world data gathering...

Thanks for your patience and information...