You have to run 93 for supercharger to kick in? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 01-29-2013, 03:57 PM   #1
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Default You have to run 93 for supercharger to kick in?

I have a 2000 SSEI L-67 series II 3800. I run 87 with no spark knock. My buddy had a Supercharged 95 Riviera and said the car detected lower octane and disabled full boost on 87 octane. Is this true or is he messing with me? Yes I know "newbie alert" ha ha
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Old 01-29-2013, 04:48 PM   #2
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The PCM is programmed to blow off boost, pull back on fuel and retard timing when it sees knock. If 87 fuel is used, then yes, this will happen under WOT conditions. I have heard that you can drive a L67 using 87 just as LONG as you stay out of boost.

And how do you know you are not getting knock? This can only be seen with a scanner or laptop.
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Old 01-29-2013, 06:19 PM   #3
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When the knock sensors detect knock they pull timing, not boost. Like Mike said, how do you know your knock sensors aren't kicking in and pulling timing? The only way to know for sure is a scan during WOT, and I will bet you are getting timing retard from the knock sensors.

There is no way I would run 87 on that engine.
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Old 01-29-2013, 06:41 PM   #4
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Actually, I'm not sure about the pulling boost part. One would think the PCM would blow off the boost because that is what'* causing it to begin with.

A L67 is the pretty much the same thing as a L36. Obviously the difference is the supercharger and some different internal engine parts. The only reason GM wants 93 in these engines is because of the super heated air that comes in because of the supercharger. Super heated air can cause pre-detonation with 87 octane.
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Old 01-29-2013, 09:16 PM   #5
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Well I will be running 93 from now on. Thank you for explaining this guys
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Old 01-30-2013, 10:07 AM   #6
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you might want to invest in some scanner that has live data, if nothing else its cool to be able to see what the engine is doing. the app i have for my android phone has knock retard, which is what would show you that. its $5 called torque. it also does about a million other cool thing for trouble shooting or fun. the only thing is you need a obd2 to bluetooth adapter which can go from 20-50 or more depending on the quality of the adapter.
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Old 01-31-2013, 10:29 AM   #7
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Quote:
Originally Posted by jwfirebird View Post
you might want to invest in some scanner that has live data, if nothing else its cool to be able to see what the engine is doing. the app i have for my android phone has knock retard, which is what would show you that. its $5 called torque. it also does about a million other cool thing for trouble shooting or fun. the only thing is you need a obd2 to bluetooth adapter which can go from 20-50 or more depending on the quality of the adapter.

Okay you are just showing off now Justin ha ha. I have an IP4 so may have to check if they have that program.

Again going back to my old cars I could always hear "spark rattle" or "pre detonation" "gas knock" whatever you want to call it. Had no idea it could be masked and causing damage in these new cars..

Could only get 9 gallons of 93 in the tank yesterday(other contents is the old 87 before I knew this) so it is too diluted to still work. Been considering going down the street and getting two gallons of racing fuel but hell that might melt something

What octane do you think this one will need? Something from NASA?
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Old 01-31-2013, 11:06 AM   #8
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one of the things that makes the newer cars more efficient is adding more timing for good gas and being able to back it off if the gas isnt so good. you wouldnt know though unless you have a scanner, just feels a little weak.

that camaro seems just about right.
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Old 01-31-2013, 11:25 AM   #9
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I thought it was photo shopped but found a video by accident on it where the owner says it came off a freight train or something and they fired it up one time,put it in drive,blipped the throttle real quick and it pulled the tire off the ground and blew both head gaskets
At 2:45 on video
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Old 01-31-2013, 11:40 AM   #10
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I bet he spent good money and time getting that to work on there too, only to not be able to use it.
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