hi all,

I've posted about this before but now I can be a bit more specific.

My L has a 4lb pulley and CAI and JDM Xcalibrator2 tune.

I have not yet fitted my colder range plugs (being done this weekend).

The problem that I am having is that when in fourth gear at about 45mph, if i give it some throttle when it builsd to around 10lbs of boost it sounds like it is detonating. (approx 50mph) In fact I am pretty sure it is.

Folks have suggsted that maybe it is blowing out the plugs as this can happen. But the crackle sounds like detonating to me. (not that I know anything!)

To check this out, today I filled up with 98RON fuel (US 93 Octane). And it doesnt happen anymore. It gurgles away but no crackling noises.

A friend suggested that as a result of the plugs getting too hot, they may be glowing a bit causing the detonation. But being a worrier I just get unhappy about these things.

I will know after the new plugs go in. But just interested to know (as Pistons with holes in arent much use to me).

Obviously the solution is to stick with the high Octane fuel ($145 per fill)

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I am not sure of your location but contact Danny at the site below.
He may be able to check your tuning and has access to a Dyno.
Give him a call.


www.adrenaline-race.com

 

read the dash board it says "Premium Unleaded Fuel Only"
i have never put anything but.

 

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You have to fill up with 98 octane or Tesco 99 octane.
I always use Shell Optimax 98.
Yep, it's expensive at 93p per litre but it's cheaper than a rod through the block.

DO NOT use 95 octane under any circumstance especially cheap supermarket petrol.

I think I mentioned this before but we (guys from the AMVO and Rebel V8) are having a Dyno day on Feb 26th at Witham in Essex.
You are quite welcome to come along if it's convenient.

 

dustin

You can't buy anything else in the UK. All our unleaded is 'Premium'

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The tune is specifically for 95 RON. (It is a JDM 91 Octane cold weather street program) But I guess it isnt quite right on UK fuel.

Just had a quick word with the chap who tunes my skyline and he explained that changing plugs won't help. If its detonating now, plugs alone won't change it. Looks like I will have to get a different tune or put up with Optimax

Annoying thing is that I do 2-3 tanks in a week.

Essex! Isnt that south of Manchester!?

Cheers

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Colder plugs will not fix detonation. Colder plugs will fix pre-ignition.

Put in some higher octane and see what happens. Could you pull back the timing?

 

[QUOTE=rutherk1]Colder plugs will not fix detonation. Colder plugs will fix pre-ignition.

[QUOTE]

Aren't these the same? Detonation is short for Pre-detonation or pre-ignition.

 

[QUOTE=SILVER2000SVT][QUOTE=rutherk1]Colder plugs will not fix detonation. Colder plugs will fix pre-ignition.

I was taught (many years ago) that detonation was an uncontrolable explosion of the combustion mixture, i.e. the flame kernal could start anywhere in the chamber, not at the spark plug tip when it fired.
This was related to too high a compression ratio or the ign timing being too far advanced.
Pre-ignition was when there was a hot spot in the combustion (from either carbon build up or the plug tip, plug threads or other sharp edge) being too hot which would fire the mixture early.

Essentially, the same effect but different

 

Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.

Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. The two are completely different and abnormal phenomenon.

 

Good explanation of the differences right here






Bird