Got a 2010 JK, with 33" tires, small lift and ProCal programmer to adjust the computer to the tire size. Been feeding it 93 octane, was getting pinging on highway in 5th gear when on the gas. Switched to 87 octane a couple tanks ago, still hearing a little pinging on highway.

Likely a ProCal issue?? Or maybe is what I'm hearing not really pinging at all? It's faint, and the jeep is noisy inside...

 

Doubt it's the ProCal, since it's just a programmer, not a tuner like the hypertec or superchips. Possibly from running 93 octane on a stock tune?

 

Are you talking about the AEV procal. That does nothing to the motor, dont put in 93 unless you have the superchips to tune it correctly.

 

Don't run anything but 87 Octane with a stock JK, 93 Octane is more expensive and screws up the computer. The Procal adjusts settings and does nothing with octane settings. If you want to run 93, get a super chips.

 

Yup, been running 87 ever since the forum crew here enlightened me

Question is now... is 1 or 2 tanks enough to retrain the computer to the 87 octane? If not, maybe that's why I'm still getting pings...? Or do I just need to do a little more jeeping?

 

I'm still getting pinging with 87 octane. Always been using Mobil, going to try another brand. Running stock gearing (I think it's 3.73) with 33" tires (actual size more like 32.25). Usually occurs in 5th gear at 60 mpg at about 2k RPM, when I then load it a little by gently opening the throttle, but think I hear it in 3rd or 4th occasionally too (again on gently throttle). I drive pretty gently. Maybe it's not pinging I'm hearing? But sure sounds like it. Already been through a couple tanks, so I've ruled out the "bad gas" theory. What's going on??

 

How many tanks of fuel have you gone through? I had some knocking in 1st gear last year and I ended up running a tank of 89 octane to cure it. Stepped down to 87 again and all was well. Now I use the Superchips with an 87 Octane tune. No knocking and it performed well today wheeling hard.

 

93 octane is much more knock resistant than 87 (this is its ONLY function), so running 93 octane should not cause knock. Also if it was truly knock it should have also gotten MUCH worse when switching from 93 to 87 octane. So my guess is that you are just more aware of sounds since your install. I know when I put a CAI on my last Jeep, in addition to other things, the valve noise (that sounded a lot like minor knock) increased a lot. So relax and if the same noise is there with 93 octane as with 87, just feed it the cheap stuff and don't worry about it, it is probably just normal engine noise. Just so you know you can trust me as well, I am a fuel scientist

 

For the fuel scientist: What are the circumstances where premium can result in poorer performance?

 

The only time a premium gasoline can result in poorer performance compared to regular gasoline would be if the compression ratio was so low that it didn't allow for complete ignition of the more stable gasoline (a.k.a. more knock resistant and higher octane number). But I am talking that the compression ratio would need to be extremely low (like 6:1 or lower). And actually the JK's 3.8 is on the opposite end of the spectrum where I am amazed that they recommend regular 87 octane with its 9.8:1 compression ratio. Usually for car/truck engines anything over 9:1 usually calls for premium gasoline, but they probably added a ton of swirl and tumble in the cylinder to keep the ignition stable at the higher compression ratio.

So really there are no circumstances (short of bad gas of course) where the JK would get worse performance with premium gas.

Edit: After re-reading my post I realized that maybe the exact mechanism by which they control the auto-ignition (knock) of 87 octane at the high 9.8:1 compression ratio may be the exact mechanism that COULD lead to poorer performance with higher octane gasoline. The high rates of swirl and tumble in the cylinder not only keep auto-ignition from occurring, but it can also extinguish the flame front that propagates through the cylinder after ignition by the spark plug. So if they designed the fluid flow in the cylinder to keep auto-ignition from occurring it could also not allow complete combustion of the air/fuel charge with more stable higher octane gasoline.