Signs of detonation on spark plugs...UPDATE

Few days ago i,v replaced my spark plugs so i can keep a eye out on them for signs of detonation

I went for colder NGK BKR8IX iridium plugs instead of existing standard NGK 6-s

Run the plugs for few hundred miles on way to Anglesey and back including giving it beans round the track

Lastnite took plugs out for inspection, here is the pic



Looked up on net for articles about plug reading and what i'v learned is basically telling me following

Mixture seems reach due to black deposits on base ring of the plug

Porcelain remained nice and white as it shoud so heat range seems spot on and electrode and tip are burning off petrol additives deposits nicely

Only thing is those little spots/balls which seems fused aluminium which sugests mild detonation?

AFR stayed good all day so its getting plenty fuel

EGT-s hovered around 800-850* on full chat round track

What else can cuase detonation? Heat and high cilinder pressure?

Car is booked in to check map/ignition timing on road in real world driving on friday but i just want some ideas from you lads so i can give them as much info as possible

Cheers

 

From what I've read the colour of the plug just tells you how hot it's running. too many carbon deposits and it's not getting hot enough to burn them off, glazed and it's running too hot.

 

Red few articles lastnite and yes you are right, but most people tend to reffer to colour of the porcelain and electrode which is wrong, apparently

If the plug is right for application porcelain remains white

Carbon deposits on base of the plug are normal due to plug not beign able to get hot enough and burn them off on that part as its conducting heat to cilinder head

Also read that plugs will show evidence of pre-ignition on tip of the electrode if its to far advanced

 

Sambo the 6's are the colder plugs not 8's they won't be cold enough, Jordy and James all use BKR6IX's

that's why you will be getting detonation as the plugs will be getting too hot.

its Denso's that are colder the higher the number.

i have a set of 6's if you want them when you come for the N2O Filling.

 

Well confused now brooky

Not what it says here!

http://www.sparkplugs.co.uk/pages/manufacturer/about-ngk-spark-plugs.htm

Higher the number colder the plug!

Its bosch and few bothers that work oposite way

 

Also same info here

http://www.ngk.com/charglossary.asp?kw=Heat+range

 

Good reads about detonation and pre-ignition

http://www.supras.org.nz/techinfo/detonation.htm

http://www.misterfixit.com/deton.htm

 

Thats how i read it also. Good info on when to go colder. 75-100hp/heat range. If you are running near 500hp shouldn't you be going up to a 9?

 

I was considering it, once i resolve this potential detonation problem i will try a set of those

 

This was on that spark plug website. According to the underlined part it says 2 heat ranges per 100hp

 

Horsepower has nothing to do with it.
Think peak cylinder pressure, combustion shape, flame propergation, piston speed and spark plug location and you have a small start ti chossing the right spark plug and heat range.

 

Sounds very involved. There has to be a baseline as to where to start ie horsepower or torque. Because alot of that information is difficult to know or work out without using alot of equations.

 

well my car is going in friday to motorsport developments in blackpool

they will take car out for some spanking and data log it so i'l update here what they find

seem like knowlegable lads there

 

Ooops sorry about that got Denso and NGK Mixed up 6's for NASP and 8's for higher power turbo.

Close the gap on the plug to 0.25 it will be 0.65 out of the box.

I run 8's when running on the Gas , sorry my mistake too much on the go at the mo

MK1 Project
T4 Project
Conservatory Project
Patent of 5 products on the go.

 

brooky is that 0.25mm?

 

And isnt that going to make spark very small and inefficient?

 

some info on spark gaps here

 

2. It is almost always necessary to use a plug with a smaller gap setting when running increased boost. The additional charge in the combustion chamber dictates that more voltage is required to jump the standard spark plug gap. Options are to close the original gap of the standard plugs by approx 0.2mm, this will relieve the strain on the ignition system, meaning a smaller voltage will be required when off boost and when on boost enough voltage should be available to fire successfully and reduce the risk of misfire. For some plugs, equivalents with a smaller preset gap are available (e.g. original part BKR6E-11 (1.1mm gap) can be replaced by BKR6E which has a preset gap of approx 0.8mm) - this is preferable to adjusting a larger gap which can put the electrodes out of true and also weaken the ground electrode. A similar effect can sometimes be had by replacing a standard copper plug with a fine wire precious metal plug (e.g. platinum or Iridium). A fine wire type plug may be able to maintain the standard (larger) plug gap setting due to the inherent lower firing voltage requirement, this benefits the engine, larger gap = larger spark - providing enough voltage is available to produce a spark!

 

The people who develop base engines do not estimate baselines unfortunately. Equations/matlab models are validated on real prototypes iteration by iteration, using tools not normally accessable by Joe Auto Garage, to determine compliance to targets.

Horsepower is poor way to measure spark plug performace. Torque may be a bit better as it relates to varying cylinder pressure. Cylinder pressure would influence knock intesity, if spark angle or leaner fuel is set incorrectly. A small engine that develops the same internal cylinder pressure as a larger one twice the size cannot and would not have the same torque or horsepower a similar rpm. Hence you cannot apply that blanket statement from the quote.

 

For me I always aim for a tan colour on the porcelain and have never had an engine failure on any bike/ car I`ve tuned.

You have to remember the little balls of aluminium are pieces of piston so you want to get it sorted out sooner rather than later..

Only downside to running atoo cold plug is cold start fouling so I`d be tempted to run an NGK 9 or 10..

As for plug gap you want the biggest you can get away with without missfire, 0.7mm is a good starting point, I found poor idle was the main by-product of too close a gap. Iridium plugs let you get away with running bigger gaps due to the reduced tip (Denso`s are even better at 0.4mm ).