So I fueled up yesterday at a different station. $20 worth of premium. Pulled out and within a 1/4 mile Jessie starts pinging. Lovely! I stopped immediately and dialed the timing back. better but still pinging. I dialed it back some more. I'm probably 8-10 degrees back at this point and it doesn't ping. I sigh heavily, curse the fuel company that obviously put the wrong fuel in the tanks and go on. Power is down considerably at these settings, but when I cranked her up this morning something unusual happened. She ran perfect. No misses, no skips.

I'm trying to determine whats happening, why, and how I can get this consistency with normal timing. I am thinking that advancing the timing is causing the occasional miss as the spark is sometimes insufficient to ignite the less dense charge properly. Does that seem correct? Is there something else at play here?

I have a new coil ( original secondary coil ) but it's not a Jag part, just compatible. My understanding is that the secondary coil is mostly required for high RPM conditions when a single coil doesn't have time to recharge between discharges. Perhaps I'm wrong there. Should I replace the secondary coil with another std replacement as a first test?

Would a higher voltage primary coil like the Pertronix FT II and no secondary coil be best or should I just put a single DAC6093 in it?

EDIT: New Champion plugs gapped correctly. New Taylor wires. New rotor. Good dizzy cap.

 

The cylinder charge has the same density irrespective of ignition advance.

Even if the retailer sold you 87 instead of 91 octane, and your car actually needs 91 (many don't need more than 87), it shouldn't require retarding the ignition 8-10 degrees to stop the detonation.

It might be the refuelling was not the cause, but just a coincidence.

 

Maybe you're referring to the cylinder charge density at the end of the intake stroke. Cylinder charge density at time of spark is what I'm referring to. The fact that it is less compressed earlier in the compression stroke. I am not saying that is the cause. I'm speculating that it may be and I could be completely wrong!

I'm sure I can advance it from where it is without detonation. But that is where I left it to get home. I'm not saying it NEEDS that much reduction to run well on this fuel.

Coincidence is always possible. But in this case it was quite apparent to me that as soon as the injector lines were emptied of previous fuel and had been filled with new fuel it went south. I punched it pretty well to leave the station, and no issues. A quarter mile later i barely pressed it and the rattles came out. Drop timing and it subsided. Seems an open and shut case to me.

 

Ah- you are referring to cylinder pressure. I follow.

Greater spark energy is required as pressure rises, so by firing the plug earlier (as with your present retarded timing), a weaker spark might just be adequate.

If you only put $20 of fuel in it, why not fill completely with known good fuel if you still suspect low octane?

 

Pardon me for butting in, but could the problem be moisture in the newly purchased fuel? I have had the same problem exactly, and occur less that 10 miles from the gas station.

Just my thoughts and I could be totally wrong... It's happened before!

Scott

 

Very possible!

 

Wouldn't that make it run like ***** regardless of timing? My "problem" is that it's running so much better!

I don't want to just dilute the low octane ( possibly just poor ) fuel with more. It won't take long to run out the 8 or so gallons; especially if I try!

 

Did it have ethanol in it ? ooooopps, i'm off

 

haha malc4d. It almost all does here. I did see a station with regular that was ethanol free.

Still pondering what's changed. Filled up from a known good fuel supplier. Increased my advance close to, but not quite to where it was previously. No knocking.

And it's still running better than before this whole fuss. I still have a periodic misfire happening, but more infrequent. Unaffected by the timing change.

I'm still suspecting poor ignition.

Has anyone tried running any pertronics ignition modules in the HE v12s? They have them specified for the Pre HEs but I don't see any stating they'll work with the HEs. I was interested by the D 72000 HEI III Module. I have a tech support ticket open with one of their engineers to see if it ( or any of their systems ) is compatible with the HE Lucas system.

 

Its important that the coil primary resistance be the same as the previous dual coils. If the resistance is higher the coil time constant will be effected. This is time it takes to charge the coil.

The idea behind the dual (parallel) coils is is reduces the primary resistance allowing the coil to charge quicker.

To calculate the resistance of dual coils use this formula.

1/RT=1/R1+1/R2

So 2 coils, coil 1 = 2ohms and coil 2 = 3ohms

1/Rt=1/2+1/3
1/0.833333 = 1.2ohms

 

Are you saying that the car now runs better than before the suspected bad load of gas? I'm confused.

 

I'm afraid so.

Maybe I had the timing way off. Maybe a spark plug was fouled and cleared up. Maybe it's a Jaguar. I'm confused too.

It's still missing occasionally. That has not been resolved and is still my focus. I'm working my way through it component by component.