You're running a HQ 107 ST @ 10:5-1 like mine so not an unusual question. With compression at the level, plus with the 575, fairly short duration cams with the HQ kit, detonation without a pretty damn good tune is likely. You really have to get a tuner who knows how to tune the Air to fuel ratios, which is your case is probably too little fuel and too much air as well as timing. You also likely have too much timing, which is good for power, not so good for hot weather and hot motors. It's finding the sweet spot, typically on a dyno. What kind of MPG are you getting? If it's high, you may have to sacrifice some of that a bit, for a cooler running and no ping bike. Mine is pretty much tuned to where it doesn't ping at 30% and don't think it is gonna ping at 100% this TX summer, but it might need a tweak. We'll see.

 

Yeah Glider I know the tune is off and plan to go see Ed out your way as soona s I get a few weeks in twon, travel alot for work. I am wondering if I am doing a lot of damage and what that damage is. We dont have any good tuners here in So Fla, adequate but not good.

 

That's a good question about the pinging, I only use hi octane, but am gonna watch this for future reference.

 

What kind of pinging are you experiencing? All of the time, only at roll on during cruise, WFO?

 

Roll on in second at 2500 rpm, and at roll on going from 60 to 100 mph in 6th. It also pings in the 3100 area in 6th at slight roll on. Not major ping but ping nonetheless , it drives me nuts, keeps me from enjoying the power in the motor as much as I should.

 

Detonation will pound out your rod bearings, and can break the ring lands on the pistons.
Its bad mojo! It makes no sense to build in a bunch of static compression and start pulling timing out. Anything you would have gained in compression is now lost in timing retard. You better off having an engine at 10:1 with a decent amount of advanced timing than you would be with an engine at 10:5 that has to be detuned because it detonates. You do not gain that much in power with a half point of compression. It is a linear curve on compression. You have to make a couple points of compression change to make more appreciable power.

This all said, detonation occurs when a mixture of gasoline and air ignite before the piston reaches Top dead center. In other words you have a piston travelling up at speed, and the combustion mixture ignites before the piston reaches TDC and can return on a down stroke. The piston has to complete the TDC before it can travel back down the bore. This is the part that pounds the hell out of your rod bearings and break pistons.

The one way to fix this is with a higher octane fuel. Octane ratings rate the ability of the fuel to be compressed with heat before igniting. Lower Octane=Faster Flame front. Higher Octane=Slower Flame front. If your using the best quality premium fuel money can buy and have detonation. Than you can look at pulling some timing. Generally you will loose some power in this process. Given it was not over advanced in the first place. If tuning does not work, the next thing you could try is using a cam that has more overlap. This reduces static compression but only at low RPM. Where generally under load is where detonation rears its head. Next would be lowering compression, this is the best fix, with very little lost in power. You can have detonation and not have it be audible to the ear. You can verify this by looking at the spark plugs. If you see little flecks of aluminum around your electrode. This is melted small pieces of your aluminum piston.

There are allot of ways to have a detonation prone engine, as there is to correct it from detonating. Simple, yet complicated when you push the envelope with the gasoline that is on the market, and feed it into a high compression engine. There is much to the discussion to have. But basically, this should give you some understanding of what it is, and how it happens, and how it destroys engines. Anything over 10:1 is pushing it on todays gas. Sure some people depending on Combination run 10:5 without problems. But you are dancing close to the limits of the pump fuel we have on the market. Tuning, cam selection, smooth combustion chambers really matter at this level!

 

Back in the day I had a '70 Ford Torino with a 429 Cobra Jet, and it was running 11.3:1 compression stock. Needless to say in the '80's it knocked on every pump gas available, which eventually cost me a valve job. Anyway, Holley came out with a water injection system for high-compression engines to stop/reduce detonation, so I gave it a try. When the engine was under load it shot a small stream of water into the intake tract, and it actually worked really well. IIRC it only cost like $45.
Makes me wonder why someone hasn't come up with a similar setup for late-model Harleys...?

 

Yes you've got to much timing at those RPMs, 2500-3200 is where you'll create the most cylinder pressure with a low duration cam, your AF might be off also, but sounds like mostly a timing issue. Pinging is usually most damaging to pistons, if it's bad enough it can burn a hole right through them. A forged piston can handle it a lot better, but still not good, try & avoid the situations you describe until you get a better tune, downshift to get into a different RPM range, etc. Sometimes it can be a throttle position deal also, your timing might be to high at that RPM range at partial throttle, experiment & see if it makes a difference if you go to full throttle at that RPM instead of a partial roll on. Bottom line is don't let it do it! So avoid that RPM range by downshifting until you get a good tune, a good octane boost will help also, not the cheap Wallyworld stuff, I've found Liquid Horsepower to be one of the best, small bottle & it doesn't take very much, throw one in your saddlebag, it works great if you can't find premium also. A lot of HD shops carry it, I know J&P has it, not cheap, but it works.

 

Great post

 

You can go to home depot and buy some Toluyene<spelling> in the paint department It raises octane, and is the ingrediant in most high dollar Octanes in a can. And do it for allot cheaper. Careful with it. It eats paint! Many know about it.