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Old 02-22-2007, 02:12 AM   #1
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Default Do not put 85 octane in your SSEi. (KR comparisions)

**In no way do I reccomend or endorse the idea of using anything less than 91octane in a supercharged motor, this is for entertainment purposes only**

Bone stock 2000 SSEi, nearly every tuneup item has been replaced in the last 3 weeks.

I had the oportunity to borrow an Actron 9190 this weekend and I thought it would be interesting to see what effect 85 octane had on a L67 with a 3.8" pulley in cold temperatures. I should mention the 9190 is a heck of a nice scantool, not a tech II but its very easy to navigate. The tank was completely empty, warning light on HUD for the past few miles. I put 5 gallons of 85 in (I've only run 91 and 93 thus far). Temperatures were in the mid 20s. Ambient air temps (iat readings) were roughly 10 degrees above the outside air temp but varied a bit.

On a 0-90 run I experienced 0* of KR after every shift even the 2-3 shift. I did not exceed 90mph because that is outside of normal driving speeds and would defeat the purpose of my experiment. Also with the 4th gear problem on the car I dont want to push it near the point where it HAS to shift...3rd I dont trust the tires pas normal highway speeds. I then tried several runs 0-80/90 or so and maintained 0* of KR. I then tried some downshifts from 3rd to 1st at around 25-30mph. Same thing, no KR at any point. I tested it for about 30 minutes of driving and could not get it to retract timing.

Basically I attribute this to the low temperatures, no KR now will have nothing to do with when it gets 100* outside this summer. I run 91 octane all year round but I thought it would be fun to test 85 since its been cold and we know the correlation between boost and temperatures. The overall blend would be 5 gallons 85 octane and 1 gallon of 91, I'd say this equates to 86-87 octane average since I dont know how accurate the fuel sender in the 2000 is.

Regardless, dont put anything less than 91 octane in your SSEi even if your car is stock. If the weather gets warm you could get likely get knock from regular gas and in the event the PCM does not pull timing, this could be bad news. In the event that the PCM does pull timing like it should, this would lead to less than normal fuel economy defeating the purpose of trying to save 20 cents a gallon.

I also hooked up the scanner to the roomates 2000 GTP, the only place we were able to get any KR (up to 4 degrees) was between the 2 and 3 shift, it is stock and was runing 91 octane. Why this is could be a number of things, perhaps its due to the fact it has not had a tuneup...maybe ever? Differences between the bonnie and gp in the fact the gp has a u-bend, its hard to say for sure.

I just thought I'd share the results, even if it is a pointless thread.
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Old 02-22-2007, 07:56 AM   #2
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There are so many factors in the PCM that try to keep you from having knock. There are high and low octane timing tables, there are knock counts (not KR), there is learned knock channel noise, (expected) and many other factors.

Then to add onto all of this, the PCM learns changes at different rates. Certain items take about 100miles to seat into the PCM, and others are nearly instant.

By putting in 85 and pushing the car, whether cold, warm or whatever....you got lucky you didn't launch your car and have to explain to any potential buyers on Ebay why the motor didn't work any longer.
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Old 02-22-2007, 10:22 AM   #3
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Many more facts are needed here not just I ran 85 vs 91 octane. What was your timing at for instance? What mods are on the car, etc... A well modded car can run low octane fuel with no KR although power output will be diminished.

For example I could run 87 octane in my car with a 3.8 pulley on but my power output woudl be signgicantly less than with the 2.6 on it
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Old 02-22-2007, 11:09 AM   #4
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Uhhh.....There is such thing as 85 octane???? Lowest I have ever seen was 86, and they cut that off almost 10 years ago here. /endofftopic
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