Roush Detonation??? What is it??

[129saleen]

What is detonation and what causes it???
Also what is "knock"???
I was driving the other day at about 50 mph and my car just started loosing power then it shut off....After i rolled to a stop I tried starting it again and when it started it made a loud knocking noise so i turned it immediatly turned it off...Its been at the ford dealership for the last 2 days and they started a total of 3 times the 1st time it did the same knocking noise then the 2nd and 3rd time it started normally....So I go up there today and start it and it starts fine but it feels really weak the exhaust doesnt sound as loud and the whole engine just sounds different....it is also making a ticking noise which saounds like its coming from underneath the car....
Does anyone have any clue what is wrong???
Cause so far the ford place has no clue what to do....
Any help would be appreciated....
Thanks

 

[BlackSaleen]

I think you will opening your wallet really soon. Dealers are idiots.
Aren't there any good Mustang Performance Shops in the Houston
area? Who tuned your car? I would go back and pay him a visit my friend

 

[marcus95]

Detonation and pinging or "knocking" are all one in the same. In a nutshell, detonation is unburned end gas. It's under increasing pressure and heat in the combustion chamber and it spontaneously combusts ignited by the intense heat and pressure. ( series II guys he he ) sorry. The remaining fuel in the end gas does not have sufficient octane rating to withstand this combination of heat and pressure.
The detonation is not the demon it's what happens from it. Almost every gas engine is run with some light to moderate knock all day long and you don't hear it. The detonation causes a huge fast pressure spike in there that breaks sh** like your piston or most likely in these stock mod motors a ring. Octane, Octane, is why you can run race gas in your motor with a crap load of timing. Heat is also a killer in there at the same time. You pulley down your blower, the tune is not dead on, and get a little liberal gas in there and kaboom. That's why the series I and II's after 11 or so lbs. of boost are useless becuase they lose efficiency and stop making power and start making a sh** load of heat. The ping isn't physical, it that actual resonating sound of metal ping from the spark and pulse. That's why people talk about the gas making their car knock although the Buick isn't running 21 degrees of timing or 12 lbs of boost in it.

Worst case you blew your motor. Just remember, any of us who want to go fast have been down your road. If you didn't grenade one of your pistons or rings then you will be happy you don't have to rebuild. You most likely are hearing a part in there. That's why you don't hear it all the time becuase it's movin around. Get it out of the dealer if the car is not under that factory warranty.

 

[129saleen]

well if the engine is blown what do i need to replace?
Can i just change the rods and pistons out....or do i have to get a whole new block?????
The 1st time this motor blew it wouldnt even start but it is starting right now so is that a good thing or does it not really matter?

 

[SVT Saleen]

marcus is essentially correct.

Detonation, knock or ping is officially known as pre-ignition. This phenomenon occurs when the temperature in the cylinder's combustion chamber increases to a point where the air/fuel mixture pre-ignites; e.g. it "spontaneously combusts" prior to the spark plug igniting it as would occur under normal circumstances.

In a properly operating internal combustion engine, the air/fuel mixture in the chamber during the compression stroke will remain at an optimum temperature, ideally just on the verge of pre-ignition, until the spark plug ignites it forcing the piston back down to begin the power stroke. The flame front caused by the spark plug ignition should ideally be uniform across the entire combustion chamber so that the entire air/fuel mixture is completely ignited. Of course no engine produced is 100% efficient so there is always residual unburned air/fuel which creates the exhaust particulates & gasses known as emissions.

Improper ignition timing &/or air/fuel mixtures create pre-ignition & also hot spots within the combustion chamber wherein some portions of the mixture are ignited prior to others with or without the spark plug igniting it, resulting in multiple, irregular flame fronts occurring.

As marcus stated, since the ideal 100% efficient engine doesn't exist in the real world (the ideal real world engine can maybe achieve 80% efficiency), there is always some irregular ignition & combustion occurring within a typical engine's combustion chamber. Proper tuning of the timing & air/fuel mixture minimizes the affects of this less than ideal operation, hence the current generation of computer controlled engine operating systems.

Also as marcus stated, left unattended, improper ignition & combustion can cause very unpleasant consequences for the internal parts of an engine resulting in cataclysmic mechanical failures.

 

[wsbrigham]

The exact same thing happened to my car a couple of months ago when I was dealing with some pinging issues. My car jsut about shut down on the freeway, was miss firing alot, seemed to loose back-pressure, and the exhause note was gone. The cause of my problem: my piston hit my spark plug and the cylinder stopped firing. After examing the cylinder and piston with a scope, we determined that here was a bunch of carbon build-up on the top of the piston that that may have cuased the impact. We flushed the engine and replaced the plug, got a new tune, and the problem hasn't recurred.

BTW,
Your Ford dealer should have a system for flushing-out the carbon and costs around $80.

Also, be sure to verify you haven't broken a piece of your piston. After speaking with many people on forums and locally, it seems that cylinder #2 is prone to this type of problem for some reason.

 

[129saleen]

Well I got my car back this morning and it turns out that the spark plug gap was completely closed so there was no spark at all.....It was the #2 cylinder also...they replaced the spark plug and it sounds and runs as good as ever... How do I get the piston checked to see if there was any damage...Should I even worry about it???

 

[wsbrigham]

Well I got my car back this morning and it turns out that the spark plug gap was completely closed so there was no spark at all.....It was the #2 cylinder also...they replaced the spark plug and it sounds and runs as good as ever... How do I get the piston checked to see if there was any damage...Should I even worry about it???

Yep. Same as mine. Either your piston made contact with the plug or a piece of piston may have broken off and made contact. Anyhow, your dealer/mechanic should have a scope for inspecting the cylinder. I'm having trouble remembering the name of the scope, but several people from this forum were kind enough to provide the name to me when I posted the same problem.....

Definitely get the piston checked so that you know what cuased the problem. If was a piece of piston, things are only going to get worse.

Good luck!