Quote:
Originally Posted by jeff4946
So why would you run a higher octane with nitrous, if you WANT timing retard? I would like to see the mods on this car. Our test engines are set for specific octanes and must run to a certain proficiency before product is released for sale. Cheap Gas? Ethanol? If an engine is designed for a certain octane, it is tuned to that octane... period.
I am betting this car is tuned, and is not updated for ethanol.
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Jeff,
I also work for an oil refining company, so your earlier points are dead on, no arguements on anything about fuels. But you're using old school carberator logic on a direct injection, highly ECU-managed engine. I've gotten slammed by that myself several times since I got the Camaro. Last Hot Rod I had was a 79 v8 with NO computer controlls whatsoever. I'm still trying to get out of my late 80's performance mindset and get used to the new world of computer controlled engines.
However; The 3.6 has a knock sensor. The engine ACTIVELY trys to add timing to max mileage/power. Once the sensor detects a knock situation, it backs off the timing for that RPM. Therefore, it adds timing to ANY octane rating. 91 allows more timing, 93 even more. Is there a max? Possibly. I don't know. Here is what I DO know:
With 87 Octane, running a data log shows timing starting at 11 and going all the way to 40 and dropping down to 20 and up again. it is the most uneven, ugly graph you've even seen. running 89, the drops were fewer and farther between, but still occured. Running 93 I had the timing start at 11, run up to 40, drop to around 36 and stay there, no further drops, except when RPM range shifted. I tested 91 later, when weather was much warmer. Seemed pretty much like 93, only was around 34 that the timing hung instead of 36. No idea if the difference was the temperatures, the octane, or both.
So, yes, I've tested the "myth" of 87 being the best gas. It's "Busted." 87 is 100% SAFE and effective with the advanced fuel/timing management this Bosch ECU has. But it is NOT the best. Based on my tests, anything 91 or better should see a smooth, consistent timing curve that follows engine RPM just like it should. For best budget, run 87, for best Mileage/Power run 91+