Pinking ??

steveshaw · Post by **steveshaw** » Wed Oct 13, 2010 9:50 am

SD1 engine on SU's, with "Opus ignition" all STD exept filters and headers.
I think I have pinking problems, but not too sure.
Have had static timing from 2 to 8 btdc with not much difference, currently set at 10 btdc at 1200rpm.
Much worse cold than hot, so it could be piston slap, but from memory the pistons looked unworn when I rebuilt it and bores were perfect.
Can you tell from the spark plugs if you have pinking?
I am also shy on power between 3000 and 4000, is this pointing to the Opus ignition, I am considering replacing it with a BBC dist and coil.
Fuel pressure is set at 3psi, anybody think this is not enough?

Steve

Quagmire · Post by **Quagmire** » Wed Oct 13, 2010 11:01 am

I would have expected less pinking noise when cold as a cold mixture will burn slightly slower thereby cancelling out some advance.

Could be wrong though...

Pete! Where are you?

sidecar · Post by **sidecar** » Wed Oct 13, 2010 11:52 am

Quagmire wrote:I would have expected less pinking noise when cold as a cold mixture will burn slightly slower thereby cancelling out some advance.

Could be wrong though...

Pete! Where are you?

Don't ask me!!!

No really you are right, the pinking should be worse when the engine is hot as the combustion temperatures will be higher.

As to whether you can see evidence on the plugs it really depends on what is going on...

My understanding of pinking is when the whole fresh charge in the chamber burns before the plug even fires, this could be due to hot carbon or a mega hot spark plug. I don't think that this will show on the plug other than it might show signs of over heating due to the very early burn of the mixture which will cause eccessive pressure BTDC.

Detonation is another can of worms and this can show on the plugs, This is when the mixture is lit by the plug but as the flame front travels across the chamber the unburnt (yet to be burnt) mixture experiances such a rise in pressure that it spontaniously ignites, this starts a second flame front. The two flame fronts then hit each other and the shock wave knocks aluminium off the piston crowns. This ali then sticks to spark plugs and can be seen as specs on the insulator.

I run my 4.6 with more advance than Rover specified and I did with my old 3.5 lump, I can't see the standard rover settings for any RV8 ever causing a problem because they are a really retarded and crap!

However I would check the timing for both static and full advance. A 3.5 should be able to run 36 degrees all in without any bother.

All just my humble and therefore bo-larks!

kiwicar · Post by **kiwicar** » Wed Oct 13, 2010 2:38 pm

Hi
Might well be a leaky exhaust gasket, this can sound like a "metallic" rattle, not dissimilar to a tappet rattle/piston slap or pinking.
Pinking is detonation of the mixture where the shockwave of the expanding gas accelerates faster than the flame front further compressing the mixture at the shockwave front heating it rapidly and causing the mixture to react more rapidly further accelerating the shockwave and the flame front . . . net result is that the detonation shock wave moves supersonically and the temperature of combustion goes up very rapidly, often combustion is complete before the piston has reached the top of the stroke and cylinder pressures go through the roof causing damage to heads, plugs and pistons, often the the cylinder temperatures get so high that the alluminium burns in preferance to the fuel.
Pre ignition is just that, as described carbon build up, or other hot spots, ignite the mixture before the spark plug, strictly it is not necesserily pinking as the shockvave and flame front are still sub sonic, however it can very quickly lead to detonation as it causes cylinder pressures to rise rapidly and you get the same net result an explosion in the cylinder.
The plugs will tell you as they often look as if they have been hit with a hammer, the electrode often burns and will have flecks of alluminium on their surface. Also a simple look at the tail pipe, if you have a very light coloured deposit that looks metalic (again flecks of ally) then you have severe detonation, still check the plugs even if there is no sign on the tail pipe as the plug check will tell you earlier.
I think it is your exhaust manifold gasket.
Best regards
Mike

steveshaw · Post by **steveshaw** » Wed Oct 13, 2010 7:23 pm

Appreciate the suggestions;

Pretty sure exhaust manifolds are tight, had a listen with a tube and heard nothing.
No sign of "particles" on the plugs I just took out, colour is "off white", Ill check new plugs after a good run at the weekend.
Noise is most noticable on light acceleration from low rev's, can't really hear much other than the exhausts if you floor it.
Have tried disconnecting the vacuum advance, no change. (does work).
Thinking of trying a good dose of octane booster as part of the diagnostics.
TDC pointer is spot on (since I tweaked it)
Cheers - Steve

DaveEFI · Post by **DaveEFI** » Wed Oct 13, 2010 10:39 pm

steveshaw wrote:Appreciate the suggestions;

Pretty sure exhaust manifolds are tight, had a listen with a tube and heard nothing.
No sign of "particles" on the plugs I just took out, colour is "off white", Ill check new plugs after a good run at the weekend.
Noise is most noticable on light acceleration from low rev's, can't really hear much other than the exhausts if you floor it.
Have tried disconnecting the vacuum advance, no change. (does work).
Thinking of trying a good dose of octane booster as part of the diagnostics.
TDC pointer is spot on (since I tweaked it)
Cheers - Steve

Pinking is most likely under heavy load at medium revs. Or rather that's when you usually hear it.

sidecar · Post by **sidecar** » Thu Oct 14, 2010 4:41 am

DaveEFI wrote:
steveshaw wrote:Appreciate the suggestions;

Pretty sure exhaust manifolds are tight, had a listen with a tube and heard nothing.
No sign of "particles" on the plugs I just took out, colour is "off white", Ill check new plugs after a good run at the weekend.
Noise is most noticable on light acceleration from low rev's, can't really hear much other than the exhausts if you floor it.
Have tried disconnecting the vacuum advance, no change. (does work).
Thinking of trying a good dose of octane booster as part of the diagnostics.
TDC pointer is spot on (since I tweaked it)
Cheers - Steve
Pinking is most likely under heavy load at medium revs. Or rather that's when you usually hear it.

Yep, what Dave said!

The throttle needs to be wide open to allow enough charge into the engine to create high cylinder pressures. The revs will be around peak torque because again that is where the engine draws in the most charge per stroke.

I think that the noise is something else!

Your plugs sound like they are a good colour too!

kiwicar · Post by **kiwicar** » Thu Oct 14, 2010 2:07 pm

Hi
I don't think this is pinking from what you are describing but if you want to clean the combustion chambers so they are all sparkly clean . . . let the tank empty (or pretty close) and chuck about 4 gallons of supeplus unleaded through the engine, that should give it a good clean just in case you have any hot spots, then if you really want sparkling combustion chambers, do a plant sprayer de-coke (described on here recently) in another thread.
Best regards
Mike

steveshaw · Post by **steveshaw** » Thu Oct 14, 2010 2:15 pm

How far do we think the timing would have to be advanced to "guarantee" pinking for me to hear.
Then I can decide if what I have is pinking, or some other problem.

Steve

sidecar · Post by **sidecar** » Thu Oct 14, 2010 2:45 pm

steveshaw wrote:How far do we think the timing would have to be advanced to "guarantee" pinking for me to hear.
Then I can decide if what I have is pinking, or some other problem.

Steve

Russel RAM bunged up a post ages ago where he stated that he could not get his motor to pink no matter how much advance was dialed in. It all depends on the peak cylinder pressure. This does not mean that an engine with loads too much advance will perform well!

kiwicar · Post by **kiwicar** » Thu Oct 14, 2010 3:13 pm

Hi
What cam and compression are you running, if it is less than 9:1 on any form of performance cam you will have to put fuel in from a really bad batch of supermarket fuel in it to get it to pink, even wih the bog stock cam it is unlikly to pink on a CR of less than 8.5, all provided the engine is in otherwise good health.
Best regards
Mike

steveshaw · Post by **steveshaw** » Thu Oct 14, 2010 6:44 pm

The collective wisdom seems to indicate that its not pinking that I have.
So I think I will set it to 6btdc, keep a close eye on the plugs, tailpipes,quit worrying and get on with the body prep.
Thanks for all the input.
Steve

ramon alban · Post by **ramon alban** » Fri Oct 15, 2010 10:03 pm

kiwicar wrote: if you really want sparkling combustion chambers, do a plant sprayer de-coke

This is the griff of an even earlier post I put up last year.

Steam Clean Inside the Engine - Whilst its Running

Introduce small amounts of water continuously into the engine intake/plenum via a 1/8" dia pipe, under the influence of inlet vacuum whilst the engine is running at 1500 rpm?

The water turns to steam inside the combustion chamber and under normal compression pressures of about 120 to 160 psi the superheated steam cleans off carbon crud from everything thereabouts.

Including - Rings and Ring Grooves - Piston Crown - Combustion Chamber - Valve Heads - Exhaust Valve Seat Area - Exhaust Channels in Header/Manifold - Downpipes - Catalytic Convertors.

The expelled carbon residue floods out of the tailpipe into a very large black puddle.

Keep allowing in water under the influence of vacuum until the tailpipe expels clean water. It can take as much as 20 litres.

Using water in a pressurised plant sprayer would seem to simplify the whole process and make it very controllable. I'm gonna have to give this one a try.

For the full thread with its various responses go here:

http://www.v8forum.co.uk/forum/viewtopic.php?t=4597&