Thought I'd give you guys another data point. My car is a stock 01 making 0.7 bar. Did some runs today on straight 91 octane and then added 5 gallons of trick 101 unleaded (97 R+M/2) for a mix of approx 94 octane.

I tried to make the runs as consistent as possible, leaving at 3500 rpm with a clutch slip to full power and shifted at 6100 on the tach. All 60's were in the 2.1x range.

I did 3 runs on 91 with an average trap speed of 112.2
Bumped it to approx 94 octane and did 3 runs with an average trap 114.0

So there it is, 91 octane can hamper even a stock car (at least in my case).

 

what was your time with the trap?

 

Nice comparison, albeit not surprising. Your ECU adapted to the higher octane by advancing timing, thus giving you more power.

What's your elevation? Your trap speeds seem low for a stock car.

 

In general ECU adaption cant "advance" timing. In this case it is just retard less timing on 94 vs 91.

This again is why "self adjusting" tunes don't really exist. It just a matter of how hard a specific tune/tuner bumps up against the knock sensor.

 

Density altitude was 5700', passes were high 12s to low 13s.

 

So if it retards less timing from 94 to 91 as you state, and then reverses the process once is sees 94 octane, isn't it essentially "advancing" timing from the more retarded state it was at while on 91? Semantics?

Point is, the stock ECU made some adaptations when it saw an increase in octane.

 

I think what Tony is saying is: it is likely tuned for 93 (or very aggresively for 91). When you run it on 91 it yanks a little timing. When you run 93 it makes more power because it DOESN't yank any timing. I don't think any ECU can "ADD" timing.

 

Exactly.

My main point is, you should never think of the DME "advancing" timing... only retarding timing.

If an ecu is tuned properly for the octane it runs on.. it will never "self adjust", it will run MBT timing or close to it out of the box.

 

Thanks for the inputs, fellas. I had a hunch the stock maps were a little agressive for 91. Tony, these were baseline runs before I order up a flash from you this winter

 

A true 91 oct map tuned for Denver altitude... basically identical to your conditions .

 

Good data! thanks for sharing

 

Unretardeds teh timings.

 

except that Denver 91 octane sucks bawls!!!


thanks for sharing this info.

 

Not sure I am understanding this. If the factory tune was designed for say 93 octane at 70 degrees, and you run 91 octane at 80 degrees, you are retarding timing. If you run 94 at 80, you might be running right at designed timing or close. However if you are running 100 octane at say 60 degrees, there will be no retarding of timing obviously, but does this mean that timing will advance beyond what the ecu was designed for. If so then you would be correct. If not then I think Tony is right, it is retarding timing.

Is the only way to design a file that is adaptive to multiple octanes to design it for say 100 octane and you can run 91 at much lower boost, but when you put 100 in it, it goes to full advance and you are fast?