Phantom Knock

[Hammer]

Every so often the issue comes up is this real knock or phantom. How can you tell? Well until now you guessed or you thought it might be solid mounts or whatever etc... But now you can fill your tank with E85 and run that and check for knock. If the knock disappears with E85 then you did have real knock. Go back and detune with gas to eliminate the knock. If the knock does not go away with E85 then it is phantom knock.

[VR4Drive92]

except for that pesky Stoichiometric stuff with E85...

DON'T go and fill up on E85 without the fuel system for it.


Just a simple word of advice...

[silky]

If you are getting knock readings when you are not in a high load situation (ie boost) than most likely it's phantom knock or knock from motor mounts/exhaust banging etc.

timing logs?

[Hammer]

Originally Posted by VR4Drive92

except for that pesky Stoichiometric stuff with E85...

DON'T go and fill up on E85 without the fuel system for it.


Just a simple word of advice...

I highly doubt one tank of E85 will cause any problem for the engine.
The worst that might happen is you run into fuel cut with E85 with your setup. I am not recommending E85 for a change of fuel but rather as a simple test for knock. E85 can run very lean and still not cause knock. That is good enough for a one tank test.

If you still have knock with E85 then it is Phantom knock if not then what you had with gas was real knock and you need to detune pronto. Let me put it this way as a test bed for a car that has some real knock if you keep driving it with real knock you WILL cause far more damage to the engine with gas than you will running one test tank of E85 even lean.

And if you do not have any knock at all then there is no need to try a test tank of E85 and no need to risk any damage at all. This is only meant as a test method for those that might be causing continous real damage to there engine because of knock which they believe is not real. And thus in the long run will actually save them from more damage not cause it.

[VR4Drive92]

Or just putting in Octane Booster or some sort of race fuel.


This idea will NOT work on a stock fuel system car. You need 30% more E85 than you would gasoline. Running it like that would piss it off. I had a friend try it one time.

You can not treat E85 and petrol the same. It is foolish to treat E85 as if it were gasoline in someone's tune.

[Hammer]

Virtualy no one that needs to test for knock is running a stock fuel system.

Almost everyone that is running into knock issues phantom or real is running very very rich tunes on gas and still complain of knock issues. It is possible that they are flowing at least 10% more fuel than they need for the already rich gas tune. E85 does not need 30% more fuel to run. It needs 30% more fuel to make power. E85 should work quite well in many of these applications.
But they will most likely run into fuel cut so it is not a good switch over fuel without further changes as you said but is good enough for a one tank test bed.

And your friend that tried E85, what happened to him? Did he have to get his car fixed after running E85 or not? I.E. Did it in fact hurt anything?

I can only lead the camels to water.

[donniekak]

Stoich for E85 is 9.76:1, gas is 14.7:1, huge difference. It would be like a 20:1 cruise tune, probably wouldn't even run.

[VR4Drive92]

Originally Posted by Hammer

Virtualy no one that needs to test for knock is running a stock fuel system.

Almost everyone that is running into knock issues phantom or real is running very very rich tunes on gas and still complain of knock issues. It is possible that they are flowing at least 10% more fuel than they need for the already rich gas tune. E85 does not need 30% more fuel to run. It needs 30% more fuel to make power. E85 should work quite well in many of these applications.
But they will most likely run into fuel cut so it is not a good switch over fuel without further changes as you said but is good enough for a one tank test bed.

And your friend that tried E85, what happened to him? Did he have to get his car fixed after running E85 or not? I.E. Did it in fact hurt anything?

I can only lead the camels to water.

HMMM... lead them to the waters of a car that won't run...

As far as I know the motor was remotely unharmed. BUT, if you feel like having to drain the tank because the car won't fucking run right then you go right ahead fill your tank up with E85 and barely drive around.

DO NOT put E85 in your car unless you have the injector and fuel delivery to support it.

There are warning labels on the E85 tanks FOR A REASON.

Please refer to a thread about E85... the first post on that page.
707AWHP 620AWTQ Stock Heads Stock Cams Pump gas



IF you want to figure out if you have phantom knock then go buy a can or two of some kind of Octane Booster and put it in your tank. Its CHEAPER than a tank of E85 and you car will actually run!