Detonation for Dummies
 

Well, I plan to be boosting shortly, within a month hopefully. And as all new users read and read and read, the scariest thing we come by is the word detonation. :o

So, I wanted to get a write up about detonation, what exactly constitutes detonation, how to prevent/detect it, and pretty much just get a good thread for the New User FAQ all about detonation.

Re:Detonation for Dummies
 

Detonation/pinging/knocking are essentially all the same.

Your engine will run out of balance, perse. When there is inadequate fuel being delivered and the incoming air is hot enough to actual cause ignition (detonation is thus ignition previous to when the cylinder fires).

This is bad because when a cylinder fires prematurely, especially with the intake valves open to have 'fire' actually travel backwards in the engine. Along with this, your connecting rod will shake (I believe this is what you actually hear when the motor is pinging) and this can cause it to slip off its bearing, shatter, fall sideways, etc...

All in all keep your ear open for sounds of tapping metal, especially something that sounds like a garden hose being crimped in a "V" right near the neck of the hose. Thats the closest thing I can think of to how detonation sounds.

Re:Detonation for Dummies
 

mmm... have a good sized FMIC, change the timing at a min. of 0.5 degree per psi of boost, and well.. your fuel management is everything... and of course an air/fuel ratio gauge / boost gauge so you can make adjustments.

I'll tell you right now my only problem I've run into with detonation is that small intercooler I used on my setup... I'm updating it with a conquest one to give a better temp drop. I've also discovered that it's smart to wrap up your chargepipes with exhaust wrap... seriously. I've run some tests and find that after driving around easy or hard, my chargepipes seem to collect a good amount of heat from the engine, so it's safe to just wrap 'em up or shield them in some way.

The only way I've been able to detect detonation is to go on some quiet road, roll up your windows, turn off the radio (etc...) and do a roll start from 3rd gear or so and floor it. While building boost you will obviously be monitoring your air/fuel meter, but listen from the engine for a sound that resembles marbles in a can filled with water while being shaked... I'm sure there are other ways to describe it, but that's what it sounds like and you'll hear it if you have any... again, it could also sound like driving over a gravel road and little rocks are hitting metal. I need to find a wave file on the net or something.

Re:Detonation for Dummies
 

Thanks for the input, both of you, some good stuff. The only problem with finding a sound file of pinging is that no one is going to make their motor ping on purpose so people can hear it, or at least I don't think they would want to do that.

Re:Detonation for Dummies
 

the couse:running to lean

The damage:To my understanding detonation is coused by an untimed explosion that ocurs on the fourth stroke as the piston comes up to expel consumed fuel out of the chamber (right before the exhaust valves open).The untimed explosion couses the upward moving piston(moving up becouse the adjacent piston is moving down on the third stroke,combustion) to all of the sudden stop resulting in damage to most commonly the piston rod and sometimes to the block.

the cure:a stand alone computer is the best but we all cant afford that.The next best thing is an afc hack.Though not as accurate as a standalone,with propper tuning a V-AFC(AFC if you dont have vtec)will alow the engine to run without the risk of detonating.An FMU is ok for 5-7 pounds.I wouldnt use one though.

Well thats all i know about DETONATION.Fell free to mock me if im incorrect ;D


Rafael

Re:Detonation for Dummies
 

Well, unfortunately, I am going with the FMU on a 6-7 psi setup. Hopefully with a BTM I won't hear any pinging.

Re:Detonation for Dummies
 

If your using a BTM you should be covered.

Re:Detonation for Dummies
 

detonation/knocking/pinging.. also another name for it is Pre-Ignition. which sounds self explainitory.

Re:Detonation for Dummies
 

i've never heard of the hose analogy. i've only heard the bb's in a can sound (my truck does it when low octane is used). are you talking about the hose sound with the bb's in a can? the hose sound is probably the turbo spooling up unless you can hear that as well.

Re:Detonation for Dummies
 

That brings up another point about your octane's rating involvement in pinging. How deeply does it correlate to pinging? (the octane rating on gas)

Re:Detonation for Dummies
 

lets just say that subaru HIGHLY RECOMMENDS high octane for a wrx. All TURBO cars should use nothing less then 91.

Re:Detonation for Dummies
 

Octane is directly related to the amount an engine pings. The lower the octane, the faster it will burn. The higher the octane, the slower it will burn. This makes it less 'explosive' and less likely to burn uncontrollably.

Richard

Re:Detonation for Dummies
 

Another misconception about detonation is it doesn't always happen when your running lean. You could be pig rich all the way through the RPM band and detonate like crazy. If the cylinder is reaching max cylinder pressure when the crank, rod and piston are right at or slightly before TDC then you get a cylinder pressure that will normally double. So it could go from 2,000 psi to around 4,000 psi. That extra pressure has to go somewhere so it will end up trying to beat the crank out of the bottom of the engine or the head off the top. Or just blowing headgaskets. Too wide of a plug gap can cause detonation. A weak coil can also cause detonation.

About cooling charge pipes, a little trick I always did was go buy one of those cheap windshield visors that are like the aluminum foil look that only cost about $2.00, and just cut it to fit the pipes and wrap them and zip tie them onto the charge pipes. Always worked like a charm. The way I would describe detonation would be it sounds like something is loose and ratling under the hood. Hope the helps. ;D

Re:Detonation for Dummies
 

Would you guys suggest going with new plugs on a turbo set up? If so what kind...

Keep all the info coming its a great help.

Re:Detonation for Dummies
 

LOVE the idea of the windshield visors. I ended up making a decenly clean looking setup, but if I did that man, my friends would laugh even more... lol.

Re:Detonation for Dummies
 

Yeah we used to have people laugh at us for using it too till they saw our cars on the dyno. 97 Civic DX non-VTEC, with a T3, 340lph pump, FMU, with Rx-7 Turbo II Intercooler sitting on top of the engine(the car had a ram air hood so the cooler actually fit), put down 316 HP. And we wrapped the pipes in the sun visor material. Not too many people laughed after that. Look at alot of Indy cars and other track cars and see how they wrap pipes and hoses. Basically the same thing. It reflects heat. ;D

About plugs to hinder off detonation, it's usually a good idea to run a colder plug and a little bit shorter gap.