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Pinging on partial throttle

2K views 26 replies 5 participants last post by  malamri424 
#1 · (Edited)
Hey everyone,
I have a 2015 SRT @150k miles currently. I'm experiencing audible pinging (but no hesitation felt like a misfire) under partial throttle and when the engine is fully warmed. This mostly occurs when coasting and stepping on the gas. I think this is where the vct/vvt is in its most advanced phase.

The heads and valves were recently serviced at a machine shop when replaced all valve springs, so it's unlikely to be carbon build up.

Any ideas on what might be the causes?

Also, thoughts on going 1 step colder spark plugs? the car has CAI, 92mm throttle body, and a tune.

Thanks!
 
#6 ·
If the noise is more like a tinkling sound then in the good old days it would be a loose piston pin bushing. From your description of light load and fully warmed up to produce the noise that would be my opinion. A scan tool might show a bad knock sensor but I doubt it.
 
#13 ·
When the throttle is closed, as in deceleration, or only slightly open, during transition to cruise, the cylinder pressure is very low, even on the firing stroke. Air is restricted, as is fuel, and the static compression ratio is meaningless as there is insufficient air to build any amount of pressure- just enough to start combustion if the throttle is opened slightly. If the throttle is closed the fuel is shut off and no combustion occurs. So if the noise is on deceleration or slight part throttle, it's probably mechanical in nature rather than combustion. I'm still leaning towards a pin bushing. The appearance of the used plug certainly shows a great deal of wear and use, but also shows the heat range is correct.
 
#14 ·
From what I can see on the first photo of the plug ignition timing looks to a to advanced, this will cause pinging as the stock of the piston is to close to the top of the stroke or you have some hot points causing pre-combustion the combustion chamber in the heads is very corse from sand used in the cast poring although the shop where you just had the work done I assume would have or should have polished or smoothed out the coarse surface texture
 
#16 · (Edited)
Honestly man octane booster is just alcohol. You need actual fuel. Look at a motorcycle shop they should have a 5 gallon can of VP or something along those lines. Octane booster is a gimmick for real. You need real high octane fuel. Even a small airport should have pumps you can get to that have real high octane. It’s a pain in the ass but nothing you dump in the tank like an additive will do anything at all for you. They wouldn’t even make high octane they’d just sell you a bottle of that crap if it worked that good. Just going from experience man I’d get some real stuff
 
#18 ·
I’d still try legit fuel man. I’m not sure how much ethanol is in your fuel where your at. Over here in the states the max was upped to 15% and I noticed my R1 was pinging the other day after fresh 93. It only does that with crappy gas like the 87 octane my friend put in after borrowing once and then no more. It was 80°F out and I was in traffic and the engine was hot so it was definitely the right conditions for some detonation on the low end for me. I know I’m rambling but I guess what I’m getting at is I’m not sure the integrity of fuel at the pump right now is trustworthy. Anywhere. Just try to keep that in mind. Maybe a bad knock sensor? Failing injector? I’m still leaning toward fuel. That’s usually the cause in my experience. Let us know what you find!!! I’m curious if my fuel theory has any outcome. I’m going to hafta cut my fillups with vp now is my try.
 
#19 ·
Who does your tuning? Do you still have your stock TB? If so throw that on and see if you still get the ping. Seen lots of issues and trouble tuning larger TB's over the years with funny behavior. With those few of mods there should be no reason to go one step colder on plugs
 
#22 ·
Pretty good increase in numbers. When you say non-mds cam, is that a stock non-mds cam from another vehicle or like a comp cams non-mds cam? For a stock cam those numbers seem solid but with a cam id suspect more than that. I put down 404 tq and 407 hp on stock tune and just an intake on 91
 
#24 · (Edited)
looking at that graph, is it possible you have to much timing down low? your HP and Torque fall off low, mine pulled and made HP all the way up to the stock 6200 redline as with most others I have seen. You make HP really low and then it falls off quick. Attached mine for reference. But you can see your stock numbers climb the same as mine. Then after the tune its all down low and falls off up top.

Rectangle Triangle Font Slope Parallel
 
#27 · (Edited)
Got some updates for anyone interested:
1- Injectors were good, regardless I had them cleaned and it made no difference.
Test tube Cylinder Gas Laboratory equipment Drinkware


2- Bought myself a MPVI2+ (hp tuners dongle) and started digging deeper. Long story short, my tuner raised the threshold for knock sensors way high (about 2x the stock setting), in addition to finding multiple modifier tables zeroed out, meaning the ignition timing was not responsive to things like coolant temperature, air intake temperature...etc Needless to say I removed that tune and now the pinging is mostly gone.
 
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