gareth60

All,

As I read about this "det" thing quite a lot on this BBS, could someone explain what is sounds like. I know what "pinking" is as I get it a lot on my old Golf Gti that doesn't like running on unleaded, is it the same?

Many thanks
Gareth.

DavidRB

Pinking, Knocking, Det and Detonation are all the same thing - petrol vapour igniting prematurely inside the cylinder. And it's not good news for the engine.

Pavlo

Pinking is pre-ignition, which can be caused by glowing carbon igniting the inlet charge, and plenty of other things.

Detonation is generally considered to be somewhat different, essential instead of the inlet charge burning in a controlled manner, it explodes. This causes big pressure spikes, shock loads on engine internals and high cylinder and piston temperatures.

Pinking is a kind in 'tinkling' sound, where as detonation tends to be short sharp bursts that sound like a pin being dropped in a tin can. Detonation tends to go 'det det det det' such that you can hear each detonation almost individually, whilst pinking is a fairly constant stream of sound.

There are also various things inbetween, but the above are easy to spot.

Paul

Raks

whats the sound i get after i have been driving for a while?

i think it sounds like it orginates from the exhaust. possible 'popping'?

Pavlo

Exhaust pops on overrun quite possible, especially if you tickle the throttle on and off as you coast after a full power acceleration run.

If you get a "tink, tink, tink" sort of sounds when stopping, that's just the heatshields cooling and contracting.

Paul

gareth60

I think I might of had it on my old car when I had the boost turned up to high, I thought it was the wastegate rattling. Is that what it sounds like, rattle, rattle, rattle....., a metalic rattle...?

Pavlo

Det really does sound like a pin dropping in a tin, it's pretty bad if you can hear it in the car. The exact sound will vary from engine type to engine type, largely dependant on bore size, think of the cylinder as a sound box of sorts.

I haven't really heard wastegate chatter except from rally cars, so can't really comment, but it's not really like detonation.

Paul

R19KET

Don't forget that a car can be detting like crazy, but you won't always hear it. THIS is the worst kind.

If you have any doubt, and don't have a Knock Link, set to MAX sensitivity, get it checked out by some one with det' cans.

Mark.

gareth60

Hmmm,

From what people are saying, it would be imposible for a stardard Impreza turbo (uk) to Det unless there is a problem. I "tweaked" the boost up, but only to a level so that the CPU didn't cut the fuel.

What i'm getting at, is, I was thinking of playing with the same thing on my Sti7 and i'm assuming that the CPU has a simular protection.

Tim Bomford

When I was unfortunate enough to hear it once it sounded like a can of nails (hit it with a hammer kind) being shaken. Got the knock link fitted after that....then some other stuff too

Tim

RichiW

Yup, rattly sound, generally from thre inlet manifold.

Rich.

Pavlo

If you can hear it, you might notice it a few times, but then it's gone, mainly because the ecu has pulled the ignition. The trouble is, I think the factory ecu waits for cumulative det events, and then retards, it also waits for the load to reduce before measureing again, as detonation is kinda self feeding (if you retarded enough to stop constant detonation, you might overcorrect for normal running).

The net result is if you hold the engine at a fairly constant speed (5th gear up a hill say) and the engine dets badly, there is a good chance it will wait too long to pull it back enough to prevent disaster.

I was getting some det on mine (I noticed a few singluar type det noises on about 5 occasions), but the ecu has retarded the ignition and I've heard no more.

The ecutek guys know more of how the newer ecus work as found on the STI7, but I suspect they can deal with removing detonation somewhat better than mine.

Paul

paulwadams_my99

its a real shame no one ever has a dat recorder and stuff at the rolling roads. Standing by the car you can hear all kinds of stuff, aint it true? Would be nice for a link.

Claudius

A standard STI has 38% knock at 4000 rpms!

john banks

38%?