Scanmaster detecting knock
Thread Starter
Teching In
Joined: Jul 2004
Posts: 34
Likes: 0
From: Littlestown, PA
Scanmaster detecting knock Almost two years ago I had Mikey at Rapid Motorsports install a cam and tune the car and never had a problem until last Fall and again this spring since I started driving the car again.
I think this all started to happen last Fall when the local Sunoco stations went out of business and I started running 93 octane instead of 94. The problem is I am getting knock retard on my Scanmaster even though the car still seems to run fine with no audiable pinging/knocking. I took the car out the other day and beat on it and it seems most of the time I only get knock retard if I slowly roll on the throttle as opposed to mashing it or just driving normal. My readings where between .5 to 3.4 degrees and I just never had this problem before. The only time I used to get any knock retard was after running through a few gears and then slowly shifting it into 5th or 6th gear and even then I don't remember seeing anything over 1.0 degree and usually it was around .5 degrees or so.
This spring I found a Sunoco so I ran the tank of 93 down to the last hash on the gas gauge and put about 9 gallons of 94 in. I ran that empty again and put another 13 gallons or so in it and I thought that would have bin enough to get pure 94 running through it and cure the problem but so far it hasn't. I might try running it empty again and run five gallons of 100 octane race fuel to see if the gas is the problem and if that doesn't work does anyone have any ideas? Sorry for the long post. Thanks for any advice.
I think this all started to happen last Fall when the local Sunoco stations went out of business and I started running 93 octane instead of 94. The problem is I am getting knock retard on my Scanmaster even though the car still seems to run fine with no audiable pinging/knocking. I took the car out the other day and beat on it and it seems most of the time I only get knock retard if I slowly roll on the throttle as opposed to mashing it or just driving normal. My readings where between .5 to 3.4 degrees and I just never had this problem before. The only time I used to get any knock retard was after running through a few gears and then slowly shifting it into 5th or 6th gear and even then I don't remember seeing anything over 1.0 degree and usually it was around .5 degrees or so.
This spring I found a Sunoco so I ran the tank of 93 down to the last hash on the gas gauge and put about 9 gallons of 94 in. I ran that empty again and put another 13 gallons or so in it and I thought that would have bin enough to get pure 94 running through it and cure the problem but so far it hasn't. I might try running it empty again and run five gallons of 100 octane race fuel to see if the gas is the problem and if that doesn't work does anyone have any ideas? Sorry for the long post. Thanks for any advice.
Thread Starter
Teching In
Joined: Jul 2004
Posts: 34
Likes: 0
From: Littlestown, PA
I finally ran the tank down to empty and put in 5 gallons of 100 octane fuel and this seems to have taken care of my knock problem. I guess the real test will be at the next fill up to see if the Sunoco 94 will run fine in it, which I'm sure it will. I can't believe a gallon or two of 93 could dilute over a tank full of Sunoco 94 enough to make the car knock, but I guess that's what happened.
