Pinging ("Pinking" in Europe)

[gr_diver]

Hello everyone once gain!

Before starting to describe my problem some facts:

-First of all, I use SuperLRP fuel in my car since 2001, as leaded fuel was removed from fuel stations in Europe.
-Secondly, from the 135 original main-jetting (SOLEX 32/32 DIDTA), I have reduce to a 125 in order to pass the state emissions test (had little emissions at 2000rpm). Now to the problem.

If I set the timing to the original 5 BTDC, my car is pinking, only if I try to accelerate medium to hard while going uphill, starting from 2000-2200rpm and until about 3000rpm (most evident in third gear). At slow acceleration, or hard acceleration on lever road it does not pink.

In order to eliminate this pinking I have (gradually) reduced my advance to about 1 BTDC.

My question is, could the pinking be caused by the smaller main-jet (i.e. the smaller throat vaccum when opening throttle cannot suck enough fuel through the jet)? Or is it because of the crap LRP fuel? Well I know that what i am asking is just a guess, but what is the most propable cause?

I would like to add, that in my Haynes manual, it is stated that if one whats to use Unleaded fuel (with one tankful of leaded every 5 unleaded), the timing must be retarder up to about 5 degrees. Does this retardation should be done for SuperLRP as well, (and the behaviour of my car should be considered normal), or is it caused by the jetting?

Thanks guys!

[N61WP]

"If I set the timing to the original 5 BTDC,
In order to eliminate this pinking I have (gradually) reduced my advance to about 1 BTDC."

If I'm reading this correctly, you have actually advanced your timing, not retarded it.

You are correct in thinking that a larger jet (richer mixture) will be less likely to ping then a lean (weak) mixture. So putting the larger jet back in should help.

Jc

[gr_diver]

"If I set the timing to the original 5 BTDC,
In order to eliminate this pinking I have (gradually) reduced my advance to about 1 BTDC."

So, the spark used to come at 5 degrees Before TDC, and now it comes at only 1 degree Before TDC. Why have I advanced more? I would be advancing if I set it say at 10 BTDC, so the spark would come even earlier...

Anyway, thanks for the confirmation of my thought man!!!!

But can anyone say if usage of SuperLRP requires reducing advance?

[baz]

i would say you have retarded the ignition the correct way and i think you might want to do a switch to the original jet for 364 days a year and put the small 1 in for the test
or start to use an octane booster to beat the pinking with the small jet

[N61WP]

You're right...sorry...I hadn't had my first cup of coffee yet when I wrote that... :o
Jc

[gr_diver]

N61WP: Don't worry my friend, it's OK! Sometimes this first cup of coffee can make a really BIG difference! One day, I was searching for my sunglasses for 20 mins before I realized I had them on my forehead... :-)

baz: This is what I am going to do then... The car doesn't like the change much anyway... especially when the engine is cold...

Thanks both of you!

[gr_diver]

I changed to the original 135 main-jet, which made big difference in driveability. It though did not affect the timing at all, I still have to run at the very same setting to avoid pinking. I have one question though. As I don't yet have a timing light, I measure timing by means of a timing disc.

Today i noticed this:

So far I brought the centre of the rotor's "contact" at the centre of the the cap's lead for #1 and then looked at the timing disc to see what advance I am running. Today I thought "let's do it the other way around". I brought the crankshaft at 5*BTDC and then looked where the rotor was pointing. The very right edge was EXACTLY at the middle of the cap's lead. And I am thinking:

Maybe the spark starts to "jump" at this point and I am advancing correctly at 5*BTDC, while I thought that the spark jumps when the contact is centrallized to the cap's lead, and was measuring incorrectly?

I am unlucky enough not to have any friends that share the same passion for cars, so as to have timing light to borrow, and see...

[kwilford]

Originally Posted by gr_diver As I don't yet have a timing light, I measure timing by means of a timing disc. Today i noticed this: So far I brought the centre of the rotor's "contact" at the centre of the the cap's lead for #1 and then looked at the timing disc to see what advance I am running. Today I thought "let's do it the other way around". I brought the crankshaft at 5*BTDC and then looked where the rotor was pointing. The very right edge was EXACTLY at the middle of the cap's lead. And I am thinking: Maybe the spark starts to "jump" at this point and I am advancing correctly at 5*BTDC, while I thought that the spark jumps when the contact is centralized to the cap's lead, and was measuring incorrectly? I am unlucky enough not to have any friends that share the same passion for cars, so as to have timing light to borrow, and see...

No, you MUST use a timing light to set ignition timing, or do it as I am about to describe below. Where the rotor is pointing has little (well, almost nothing) to do with ignition timing. What actually creates the spark (and determines the exact time of the spark) is the opening of the points. That is why you MUST re-time an engine after adjusting the points, even though you haven't moved the distributor relative to the rotor. Changing the point gap will cause them to open at a different spot relative to the distributor cam, and hence relative to the crank. As long as the rotor is even CLOSE to the cap post when the points open, the spark will jump the required gap. In fact, it ALWAYS jumps the gap, as the rotor never actually touches the outside cap posts.

When you adjust the points, you are setting them to a specific "gap", but it is really the "dwell angle" you are setting. "Dwell angle" is the "...number of degrees of distributor rotation that the points are closed...". In effect, this determines how long the coil is "charged" prior to the the points opening, which in turn "...collapses the magnetic field around the secondary core, creating the high voltage ignition spark...". For more interesting stuff, read
http://www.mgcars.org.uk/electrical/body_timing.html

Anyway, you may already have LOTS of timing advance. A very effective way to set the timing is to advance it until you start to get "plinking" (we call it "pinging"; more accurately called "detonation" or "pre-ignition") and then slightly retard it. I sure wouldn't be changing the jets in response to detonation alone; plug colour (and driveability) is the number one method. Set your timing (either by the method above or with a timing light) and THEN determine your optimum jetting by doing a run, and pulling and inspecting your spark plugs. For more info, do a search for "RallyBob's" posts and "jetting".

HTH

[gr_diver]

Thanks for the reply kwilford!

All the info you supplied was very intresting, it gave me a very good impression of what's going on on the distributor's breaker plate...

Of course I am not trying to eliminate detonation by changing jets... I just thought that MAYBE the smaller jet I put for emmisions test was the cause (as in most manuals one can read that maladjusted carbs might be the cause for pre-ignition...) and asked for an opinion... and then just posted the results...

Anyway, if I rotate the engine by hand until the points just open at the #1 lead (measuring by multimeter, not by eye), I am already ATDC, confirmed visually through the spark-plug's hole, by seeing the piston on it's downstroke... What the hell is going on in there? Anything more advanced will cause slight detonation during hard acceleration. The car is pulling strong though, and doesn't overheat at all (symptom of too retarder ignition)...

[Turbo X]

gr drver
Anyway, if I rotate the engine by hand until the points just open at the #1 lead (measuring by multimeter, not by eye), I am already ATDC, confirmed visually through the spark-plug's hole, by seeing the piston on it's downstroke... What the hell is going on in there? Anything more advanced will cause slight detonation during hard acceleration. The car is pulling strong though, and doesn't overheat at all (symptom of too retarder ignition)...

think of it this way..a car move down the road, say 20 mph and you want to
throw a rock at it from the side.. you know you can't just throw it at the car
you will miss it, you have to aim in front of it for it to hit. just like the timing of a cylinder, it must send the spark pryer to the piston reaching TDC.
pre ignition is when fuel explodes before TDC. detonation is when you get two starting point of ignition in the cylinder and when the two collide you get the pinging sound. no lead in the fuel and or a lean fuel air mixture will cause this. your problem is more likely the no lead in the fuel.. I use 100 low lead aviation fuel every other tank full or so.. and it makes the defence.