Possible Knock

[Hanaldo]

Hey all,

I was just out giving my car a bit of stick, and on my way home it made a strange sort of sound on high boost. To me it sounded a bit like I had blown a hose clamp, it was that sort of hesitation gurgling noise from the engine but without the obvious cut in power. My mechanic mate in the car said it sounded like detonation to him, I've never personally heard detonation so I'm not sure.

Thing is, it is intermittent. I kept my eye on my AFR gauge and on full load it was at around 10.5-11, which is normal. So I gave it a few full load runs listening for the sound and watching all my gauges, but it seemed to have stopped, was all going fine. So I thought maybe it got hot and pinged a bit. But then on the last run it happened again. It was also backfiring a little more than normal and it is popping around on idle a fair bit (my car has quite a profound lean pop normally but it seems like more than normal to me).

Now I'm thinking maybe coilpacks or sparkplugs? The coilpacks are Splitfires though, and the plugs are NGK's gapped to 0.8. Any advice? I wouldn't have thought there could be any confusion between those sounds?

[89CAL]

What heat range are the plugs?

[Hanaldo]

I THINK they are NGK Iridium BKR6EIX, but it's been over a year since I put them in so can't really remember

[DVS JEZ]

Try running 7's. Bit colder plug. Was it a hot day?

[89CAL]

ix are irridiums or platinum aren't they?

Just get some copper heat range 7 plugs to try out

[Hanaldo]

Yes they are Iridiums. I'll try some new coppers. Won't load it up again until I've tried. Thanks mate.

[Black_CSR]

Detonation or Pinging sounds like a bunch of small coins rattling inside a metallic container.. if u did hear it it's not good.. Have u checked all hose clamps n hoses are secured where all the boost of air travels through??

[tridentt150v]

If you are driving a 34 [in your sig] then you should see your check engine light flashing when it knocks, sounds like a lazy plug to me.

[paulr33]

MONITOR, 1 CHANNEL, KNOCK

press UP to display top score

press RIGHT to clear top score

flog it

check peak knock level

if its over 50ish get the tune checked / check fuel / back out some timing

[lilcrash]

Don't drive your car til you get your tuned fixed, you have been warned.......

Just joking. Just goes to show it happens to all the people who have got perfectly tuned cars too.

Edited December 11, 2011 by lilcrash

[SargeRX8]

I really doubt you heard the knock. While flogging it, with windows down or up, turbo spooling, exhaust screaming and the road noise its f**king hard to hear knock. The only way I know I knock is with my power fc. If you can hear something happen out the exhaust, its probably not knock. I don't think detonation would cause any alteration to exhaust noise, because if it did then it would be listed as a known method for picking up knock.

[lilcrash]

Knock is actually pretty easy to hear, i wouldn't recommend this but if you want to see for your self, go fill your car with 91 octane fuel and go for a drive, you won't even need wot, it will just ping it's ass off under any load.

[Hanaldo]

Detonation or Pinging sounds like a bunch of small coins rattling inside a metallic container.. if u did hear it it's not good.. Have u checked all hose clamps n hoses are secured where all the boost of air travels through??

Yeh it didn't sound metallic to me which is why I didn't think it was knock. But worst case scenario it is knock, so I'll treat it as such until I can resolve it.

I've checked all the hose clamps and vacuum hoses and everything is nice and tight. Thing is, it didn't cut power completely like a blown clamp or vacuum leak usually would. It felt like a little bit of a flat spot when the noise came on, but only just noticeable and only really to me because I know how my car feels. My mates didn't really feel it.

If you are driving a 34 [in your sig] then you should see your check engine light flashing when it knocks, sounds like a lazy plug to me.

Yeh well I was connected to NIStune when it occurred and it didn't trigger the knock maps. AFR's were good, timing looked fine, it was still in the primary maps, everything was normal. But then I don't want to put complete faith in the stock knock sensors.

I really doubt you heard the knock. While flogging it, with windows down or up, turbo spooling, exhaust screaming and the road noise its f**king hard to hear knock. The only way I know I knock is with my power fc. If you can hear something happen out the exhaust, its probably not knock. I don't think detonation would cause any alteration to exhaust noise, because if it did then it would be listed as a known method for picking up knock.

And my car is LOUD. External gate, screamer etc. This noise was when I was on full song and it was definitely audible. I just didn't want to take it lightly; an engine noise under full load that I haven't heard before on a hot day after the car had been given a fair hiding... If it's a lazy plug or something like that then I'm all good, but if it's knock...

[Bsa]

My mates vl turbo used to make strange noises on a hot day only under load. He has a simular setup turned out it was a faulty plug and was back firing out the screemer almost sounded like knock

[LANDSCRIBBLE]

How long should plugs last on a tuned motor anyway?

[Hanaldo]

Depends. I check the condition I mine every service (3000 kms).

[SargeRX8]

I replace them every second oil change or when they die, which ever comes first. I get the odd miss with my car now, 1.1 on anything above standard turbo and boost just won't work.

Don't get iridium plugs, coppers are tried and tested to be better performers.

Edited December 12, 2011 by SargeRX8

[89CAL]

Coppers don't perform better. they perform the same but are far cheaper, they just supposedly don't last anywhere near as long

You can't just say there better. if i could get iridiums for the same price id probably run them

[SargeRX8]

Ive read, not once, but many times that the copper plugs can give a stronger spark than the iridums. Iridums are just designed to last >99000km, which won't happen on a modified engine.

[Hanaldo]

Iridiums perform fine. The issue is, as 89CAL said, that Iridiums are much more expensive and on a modified engine they won't last that much longer than a copper one anyway. So there's no point getting Iridiums. Which, if my plugs are my problem here, is the case in point as mine are only about 10,000kms old.

Wish I'd known that before I bought mine