Pinging on 93 Tune when hot outside

02LincLS

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I'm looking for additional info from anyone that uses an OBD scanner and an app like Forscan or Torque. I believe the hotter engine temps I'm encountering are causing pinging issues under WOT with a 93 tune I'm running. It is a rattle sound and occurs at and near WOT. Its more likely when cruising and then passing, rather than WOT romp from a stop. I'd like to see what other people get for values on their cylinder head temp, intake air temp, and anything else that might be relevant; fuel rail pressure, fuel pump duty cycle, sparkadvance etc.

Here's a list of bad things that cause pinging and what I've done so far to address it... Hopefully the format encourages replies to specific parts people might have experience with. (Temps in degrees F)

Too much compression
Well, there's not much I can do about this. The LS is pretty high to start with. Are combustion deposits an issue on this engine? Can anything be done if there is deposits? The engine is not babied (pinging is not an issue most of the time- just in the hot weather it seems).

Over advanced ignition timing
Well, it was a remote tune from a long gone vendor on here. I pulled 6 degrees of timing from 2K to redline and it helped reduce pinging. I might do another 2 degrees. It stinks to pull so much timing and lose power.

Lean fuel mixture
In addition to pulling timing, I bumped WOT 6% richer. This combo has greatly reduced the pinging. I don't have a wideband O2 sensor though and don't want to hurt the cats going too rich (letting off the throttle is the stop gap for the more serious issue of pinging). I may try going to 8% richer. I'm running a fuel pump from an '06 Ford GT since I use nitrous on rare occasions (don't worry, its set up rich so that cooling effect as well as cooling from the nitrous means no ping). Fuel pressure is constant 40 psi under WOT, and pump duty cycle is, well I forgot, but its not even trying. 20% at idle, maybe 50% WOT? Forgot. I might have to look at that PID with my xcal to be sure 50 does not mean 100%, but pretty sure its right since fuel pressure is constant.

Low octane fuel
Guess I can try Mobil 93 instead of Sunoco in case there's some tomfoolery at this specific station. Is there an octane detection pid on a car this old?

Spark plug too hot
Well, I'm using a 1 heat range cooler than stock so I doubt its an issue. However, its Iridium tip (NGK). Never had an issue with them before and they look great after 100K miles. They're pretty new and properly gapped.

Engine Overheating
From another thread, it seems that while many many LS' run cool enough to keep the gauge parked in the middle, the truth is that I should be seeing temps from 195 to a max of 210. I think my recent pinging issue starts here. This car idles and does stop n go traffic at 212, but at highway speed near 2K RPM and above, the temp climbs. Going up a hill while passing, it can hit 230 momentarily. It drops VERY FAST if you let off and downshift to 3rd and get some good engine braking. Is that purely a result of cylinders pulling in air and not burning much fuel, or is there something going on with coolant flow? Is it fair to say that since I can get 210-214 idling in a 100F+ parking lot with A/C cranked, but climb in temp on the highway, that its coolant flow issue? I cleaned a lot of sand out of the radiator but there are still some pebbles jammed in there (and this surely helped because I never got the fan to go in jet-mode since- even in harsh conditions and driving). Fins could be straighter too. I guess the easy next thing to try is the thermostat; maybe its not opening fully. I don't remember any bad overheats where the car warned me; I know those could damage the t-stat. There's got to be a way to troubleshoot whether its radiator or water pump. System and cap pressure test good so heads/gasket should be fine. No smoke in exhaust, no coolant/oil cross contamination etc. It seems I've always had these temperatures since I searched before posting; I found a post I made years ago and the temps I reported are roughly equivalent.

High intake air temperatures
This car gets toasty! Its stock air box and intake tube. It sits right on top of the radiator and essentially the exhaust manifold. I've seen 160 at one point in stop and go traffic in the beating sun where it was 103F outside. If this car isn't moving, it climbs FAST. I don't see this on my turbo Flex so whats the difference? Is the sensor in the LS located in a spot that is easily heat soaked? Is it a good representation of what is actually entering the throttle body? Should I bypass the coolant line that goes to the throttle body? (I'd valve is so it can be "reversed" for winter driving if I ever do that in the future). Should I bother wrapping the intake tube to insulate it? Seems overkill. What do you guys get for temps? and do you have any custom cold air "kit"
Other fears include small shards of old $hitty plastic blocking passageways or a bad water pump/impeller. The car has always had fresh coolant so I doubt there's any corrosion but who knows.

Loss of EGR
I assume no issue since I have no codes. Is that a safe assumption?

Bad knock sensor
Well maybe but seems unlikely. If I knew where they are and tapped them while data logging, I wouldn't know how to interpret the pids (assuming I looked at the right ones)


In summary, the spark timing pull and richer map helped reduce pinging. There was none when I first hit coolant operating temp of 212, but after some highway driving, it came back, though it was greatly reduced. I guess one last thing to try is returning to stock but that would be too easy.
 
All my LSes have always pinged under WOT... Didn't matter the brand of 91 fuel or the temp.
 
I've long been a believer in a bit of methanol spray under performance conditions. Instead of cutting back on the spark I simply let a micro-switch on my throttle tell my methanol pump to, 'Shoot the juice to it, Bruce'.

My NX system uses methanol entirely as added fuel so under moderate conditions, I don't activate the nitrous oxide part of the package. Methanol is very forgiving in terms of being a booster/coolant/power adder.

KS
 

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