I've have been tweaking with the SCT programmer onmy 99 5.9 R/T. This is a California truck. Sean/Hemifever has sent me a couple of new tunes with reduced timing, however, I am still getting some ping under load (89 tune to run on 91). I'd love to run the 91 tune. The plenum plate has been done, colder 3923 plugs, cooler thermostat, K&N cold air intake, MAP sensor, and it has been seafoamed. Unfortunately, I only have crappy California 91 fuel to work with. Any ideas on how to help this issue out? Truck currently has 142,000 miles. Thanks.

 

I got pinging under heavy acceleration when I was running a 93 Hemifever tune with 87 octane in the tank... That was solved by putting it back to the 87 tune. Are you saying you're running 91 fuel with an 89 tune?

 

did you put the 180 thermostat in that Sean requires?

 

I didn't know it required that. I've got the stock tstat as far as I know. Thanks for the heads up though.

 

Stock is a 195, Sean usually encourages/requires a 180 to reduce the Cylinder Haat Soak temperature, helps keep the combustion chamber cooler and reduce ping. If the PCM didn't frown upon too-low of temperatures, a 160 would be feasible. The PCM throws a "engine too cold" alarm at 165 or less for a certain time frame.

 

The tune that he provided as an attempt to cure is an aggressive 89 tune to run on 91. Helps somewhat but still pings above 3000 rpm on harder acceleration, especially when warm. The 91 tune, which I love how it feels, won't ping until temps are warmer and some heat soak has occured, but once it does, pinging really rears its ugly head above 3000 rpm from moderate load on up. Yes I am running a 180 tstat.

 

sounds like he got too aggressive with the timing curve, or the fuel isn't really what it's labeled as. The tune I have is marked as a 94 tune that I had him concoct at my request, and I get very minimal pinging after 4500 on 93 pump gas under load, and turning on the methanol spray relieves that (keep in mind my water temp never goes over 184- hovers around 176-182 with the E-fan on). It's a very aggressive timing curve with some other stuff thrown in.

 

I used to run his 93 tune on 89 gas in my 5.2. Never saw any difference between 89 or 93 gas. Stock t stat and autolite 3923 plugs. Have you tried different gas station?