on 87 octance does the impala ss pick up alot of knock?
11-13-2007, 09:12 PM
#1
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on 87 octance does the impala ss pick up alot of knock? I was driving down the road and wondered why my stock 07 impala ss ran a 15.0 at 93 where everyone else is trapping closer to 100. Then I got to thinking about the fact that my girlfreind aways runs 87 octance in the car and started wondering if because the octane level was so low that the ecu could maybe have picked up knock under WOT and retarded the timing in the car slowing it down. What do you think?
Last edited by Clean94Z; 11-13-2007 at 09:17 PM.
11-14-2007, 08:02 AM
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A buddy of mine has an 06 SS and has used nothing but 87 in his since new with no knock problems. Personally I've never used 87. I used 89 for the first couple months than switched to 93.
11-14-2007, 08:12 AM
#4
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the owner's manual tells you that you should use at least 91... and that you can use lower grades, but if you do, you will experience reduced performance and possible ping/knock/knock retard.
and even though you can't HEAR it, I'm sure you are getting it....
I log mine, and even with using Mobil 93 octane, I get some knock/knock retard.... so I can't imagine running on 87...
and even though you can't HEAR it, I'm sure you are getting it....
I log mine, and even with using Mobil 93 octane, I get some knock/knock retard.... so I can't imagine running on 87...
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11-14-2007, 01:16 PM
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When I was logging data and had some KR, I could not hear it. Heat played a big part in KR even with 93. I think my home area is around 200-400 above sea level. With my car, heat causes more loss (ECM pulls timing when IAT is up) than anything. Right now it feels like a rocket even with the stock tune and a mix of 93 + 87.
11-14-2007, 01:37 PM
#7
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same here... car is LOVIN' the cold weather...
we have to come up with some kind of cryogenic cooling system under the hood...
we have to come up with some kind of cryogenic cooling system under the hood...
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11-14-2007, 03:00 PM
#8
How much knock does your pick up on 91? I wonder how much power is being lose per degree of knock?
and people wonder why I am not running in the 13's with my mods.
11-14-2007, 08:29 PM
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When I ran the car it had 250 miles on it on 87 octane. I now have 6k on it and I just put in a k&n panel filter and trimmed the air box. I filled the tank with 93 and I think I am going to the track friday night.
11-15-2007, 09:24 AM
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11-16-2007, 03:36 PM
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The LS4 loves the cooler weather, the tires....well....not so much and I have never seen any knock at all on the scanner regardless of the Octane. PCM is probably not recording it if it can control it.
At a guess, it probably retards the spark 4-5 degrees when it sees knock and costs a minimum of 15 horsepower between 87 and 91 (assuming aggressive enough timing by GM or aftermarket). In my opinion, the knock argument is mute as GM artificially limits torque anyway. Damn engine is hobled six ways from Sunday.
At a guess, it probably retards the spark 4-5 degrees when it sees knock and costs a minimum of 15 horsepower between 87 and 91 (assuming aggressive enough timing by GM or aftermarket). In my opinion, the knock argument is mute as GM artificially limits torque anyway. Damn engine is hobled six ways from Sunday.
Last edited by 06 SS; 11-16-2007 at 04:40 PM.
