Detnation..maybe..I dont know

[Maaso]

I was thinking back the the second day I had my truck, and I beat on it a little just to get the taste of all the "hype" about these trucks. And what I thought was it bouncing of the rev-limiter might have been detnation y'all said.

Now, I know enough to know what detnation technically is. But I was just wondering what it does exactly when its happening?

Like...for example. About 4800 the truck would jolt real bad and stop climbing on the tach until I shifted. Then the truck pulled hard all the way back to 4800 in the next gear.

Now I realize thats a vague description of what happened, but it was a while ago and too much has happened since then for me to recall exactly what happened. And I dont want to do it again just to refresh my memory.

So I was just wondering if that is the dreaded detnation that I was experiencing, or was I just bouncing off a rev-limiter. I know from my old Camaro that factory rev-limiters can be shady to say the least, and can accually do more harm than good in some cases.

Any ideas....or a more detailed description of what to expect when detnation occurs?

Thanks,
Mitch-

 

[dgoodhue]

Re: Detnation..maybe..I dont know

The stock chip rev limiter is 4800 rpm. If your hearing detonation that is bad, you can still have setonation that the ECM is picking up. To me detonation sound like a a hollow mettallic sound.

 

[Loeryder]

Re: Detnation..maybe..I dont know

A scan tool would tell you if its detonating.
It will show up as spark retard.

As the ECM retards the timing it decreases power and attempts to save you from damaging the engine's internals.

What is actually happening is the compressed fuel charge is igniting before the plug fires.
It is putting an extreme downforce on the piston dome and thus the rod as it is still compressing the fuel charge.
Detonation can burn holes in pistons and twist rods up like pretzels. (especially our stockers)

Now if you had a scan tool you could record data on then you could watch the RPMs and boost climb, note the spark retard and determine if it was "knocking" as it approached the 5k mark. Stock trucks should be shifting before 5k anyways so if you are getting it that high you've got other issues as well.

Extreme detonation can be heard and felt.
If you hear a sound like marbles going down the intake its BAD!
Some say it sounds like shaking a can of marbles.

Once it becomes audible knocking the ECM has probably removed all the timing it can and you are one your own. Our ECM can back out 15+ degrees of timing (I thought 17* was the magic #), but even at 5-6* you should be checking for problems.

I am sure someone can elaborate more that has more detailed knowledge than me, and I could be wrong but that was my understanding.

 

[turbodig]

Re: Detnation..maybe..I dont know

I was thinking back the the second day I had my truck, and I beat on it a little just to get the taste of all the "hype" about these trucks. And what I thought was it bouncing of the rev-limiter might have been detnation y'all said.

Now, I know enough to know what detnation technically is. But I was just wondering what it does exactly when its happening?

Like...for example. About 4800 the truck would jolt real bad and stop climbing on the tach until I shifted. Then the truck pulled hard all the way back to 4800 in the next gear.

Now I realize thats a vague description of what happened, but it was a while ago and too much has happened since then for me to recall exactly what happened. And I dont want to do it again just to refresh my memory.

So I was just wondering if that is the dreaded detnation that I was experiencing, or was I just bouncing off a rev-limiter. I know from my old Camaro that factory rev-limiters can be shady to say the least, and can accually do more harm than good in some cases.

Any ideas....or a more detailed description of what to expect when detnation occurs?

Thanks,
Mitch-

What you're describing, in the context of a stock chip, sounds like the rev limiter.
4717 was the stock limiter value.

Could be an overboost cutoff as well, depends on the chip.

You can mimic the effects of deto. Go to a junkyard, and get an old cast piston.

Take a hammer, and beat on the top areas around the rings. See how long it takes before the ring land gives up. This isn't an exaggeration. This is very literally what's happening inside. Potentially, with even more force than the hammer.

Also, take the rod that's attached to the piston. Stand it up between 2 bricks. Hit the top (small end) with an 8 lb sledge. See how long before the rod bends.

Repeat the exercise with a set of bearings, both rod and main. See how long before they get out of shape enough to contact a crank.

There are soooo many trucks out there right now that detonate on a regular or semi regular basis. This is why there are so many motors out at any given time.

Rods don't give up because there's a problem with the rod. Bearings don't spin because of lack of oil. (usually) Cranks don't break because the metal was weak, or not treated. Deto is the culprit 95% of the time.

There's a lot of people who really don't care; they're planning on rebuilding anyway, or are looking for a reason to do a rebuild. Where they fool themselves, is thinking that the better parts are immune to deto. They will survive the abuse longer, but they too, will die.

If you want to save your motor, get yourself a mechanism to monitor knock. A scan tool of some sort is really the only way. The indicator lights on ultimate boxes tell you little... people either miss seeing the light, or ignore it when they do.

People also don't seem to want to do what it takes to alleviate knock. This takes either:

1) A commitment to learn what it takes to get rid of knock in a modified motor, and the time necessary to learn this.

2) The patience and $$$ necessary to have someone do it for you.

3) The self discipline to leave things that are running fine alone; that there is such a thing as "fast enough".

 

[dhorsman2000]

Re: Detnation..maybe..I dont know

Loeryder pretty much hit it on the head as far as a technical description. But for me the sound of detonation is like if you were draging a bolt on a string right under the truck...or marbles in the oil pan. Sounds to me like you were just over-reving and hitting the rev limiter. Either one is bad...take it down a notch on the gas pedal

 

[Maaso]

Re: Detnation..maybe..I dont know

Aight, so chances are I probably didnt experience the dreaded deto then?

I havent been mean to it since, I bought this truck mainly to drive it....and I cant drive it if its tore up. And I dont want to be paying bills on a truck thats sitting in pieces all over my garage you know.

 

[Loeryder]

Re: Detnation..maybe..I dont know

Aight, so chances are I probably didnt experience the dreaded deto then?

I havent been mean to it since, I bought this truck mainly to drive it....and I cant drive it if its tore up. And I dont want to be paying bills on a truck thats sitting in pieces all over my garage you know.

Well you mighta bought the wrong truck. lol

If you maintain it and don;t beat on it it CAN be reliable.

 

[James Thomas]

Re: Detnation..maybe..I dont know

Here's a little tip that will save you trouble, money and even make your truck faster in a race if its stock or mildly modded (stock heads & cam with other bolt on's). JUST LEAVE IT IN D! It will shift it's self in the right power band and at the right time. Also get Tuner Pro or Datamaster before you hammer on it any more, your truck and your wallet will thank you for it.

____________
James