Low Octane Fuel and Knocking

[Razor]

Shoudt

does this occur only when you're using this fuel?

check your idle setting might be too high.

[shoudt]

I have driven it only 1300 miles since I got the car. I have been all over the place from 87 octane to 94 octane. I am trying to figure out if the gas gauge works so I often top off the tank for fear of running out of gas.

It seems to read near empty a lot sooner than I would expect. So I end up mixing grades.

But with gas prices skyrocketing, I have been getting 87 octane recently. This run on only seems to happen now that I stick with 87.

Thanks

[halz]

continues to run for a little while. Every once in a while it gives a rather loud backfire then finally comes to a stop. Should I be using highedr octane?

You should first of all be getting your car properly tuned with particular attention to mixture and timing. If the problem persists then it is likely that you have carbon deposits in the cylinders that are forming hotspots. The hotspots remain hot enough to ignite any mixture present after you shut off the ignition and that is what causes the annoying run-on you are experienceing.

[Brett240]

Landmizzle is right on the money with his explaination of premium fuels. As he said, the additives (antiknock agents) prevent the fuel/air mixture from igniting prematurely. And yes, premium fuel has less BTUs per give amount of fuel. So, as it has been said many times before....is it's not pinging and your using regular grade fuel, everything is fine! Using a higher grade fuel is a waiste of $$$

of course this is not always the case if your looking for HP,

using a higher octane fuel means an engines threshold for knock is increased, allowing more ignition advance = more power, this is why you dont see hard tuned cars running low octane fuel.

also in aus our 98 ron fuels actually give better fuel consumption in cars setup to use it. this type of fuel is denser than regular fuel so a car tuned to use it will use less of it, which offsets the extra cost.

[beandip]

This is a ballancing act , because if you encrease the compression then you do need higher octain fuel. The same is true if the timing is advanced . This one of the reasons emissions require retarted timing and low compression and our fuel is now low octain. Premium fuel used to be 110 octane and some engines had over 10 to 1 .that was in the late '60s. The '70 --'72 Z had rather high compression . From then on the compression was lowered to the 8s. This is one of the reasons raising the compression helps these engines make HP. That and they are all high geared . It may sound cool to have a car that will go 130MPH , but if the rear end was changed to a 370 or 390 the car comes alive at driving speed . Some thing to think about. My 1 1/2 c. Gary

[venom42]

With the Talon, I have a datalogger that tells me the timing advance, knock count, etc., but with the Z I was afraid to risk it after I read the manual (91 or better). I will KNOW when it is pinging, right? If it does, will that one tank hurt it?