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Dang WOT pinging, TQ secondaries?

mopower440 said:
Its strange though, when i hit it WOT and it pings, i can back off the throttle just a hair, i mean a hair , like 1mm, and the pinging stops, rpm BARELY drops and the timing im sure doesnt retard any with only letting out that hair, so if it was coming in too quickly, wouldnt it still be pinging when letting of just a hair being the rpm didnt hardly drop?
Click to expand...

i will admit I’m just speculating - but when you slightly back off the throttle the engine load falls off significantly, especially with a torque converter. My theory is engine load make a lot of difference. If it didn’t a lot of motors with manifold vacuum advance advance at idle and 44+ degrees initial and vacuum advance (at idle) would be pinging away just idling. And I’m fairly sure the relationship between engine load and timing is more exponential rather than linear. Slowing down your advance may well help - I think a lot of guys try to bring the advance in too early on the street. And you may need to back off another degree or two on total timing.
 
Make sure none of your plug wires are close together. The spark can jump from one wire to another and create pinging under load.
 
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The scientists amongst us will have to detail the why's and wherefore's, but suffice to say
there is less BTU's of energy in alcohol than there is in gasoline....
which is why oftentimes fuel economy suffers.
Ethanol is already at least partially oxidized, so it's energy content per unit of density is
lower than that of straight gas; that means you need more of it to go the same distance
typically.
Not to mention....the crap evaporates out of carburetor vents when the car sits AND alcohol
attracts water, too - increasing chances of frozen fuel lines.
Finally, it tends to eat through older "rubber" fuel lines too, meaning you need to use "fuel injection"
rated fuel lines to try to avoid collapses.

I'll run etha-crap in my modern vehicles because they're designed to tolerate the stuff better, but
I don't put any in ANY older vehicle (like Fred) or ABSOLUTELY not any 2-cycle small engines,
like chainsaws or weedwackers - it eats their plastic parts!

To find "straight gas" stations in your area:
https://www.pure-gas.org/
 
messed with it for a while today. Filled it up with 93 octane, not ethanol free but will next time now that i know where to get it. 1 thing i found was the vacuum dash pot that holds the secondary air door closed until the right time was blown out, so replaced it with a good one. Seemed to help a little bit. Then i tightened the secondary air door and seemed to help a small bit more, then limited the secondary air door a little more and it seemed to help a small bit, but all in all it still there some, just not as bad.
 
mopower440 said:
messed with it for a while today. Filled it up with 93 octane, not ethanol free but will next time now that i know where to get it. 1 thing i found was the vacuum dash pot that holds the secondary air door closed until the right time was blown out, so replaced it with a good one. Seemed to help a little bit. Then i tightened the secondary air door and seemed to help a small bit more, then limited the secondary air door a little more and it seemed to help a small bit, but all in all it still there some, just not as bad.
Click to expand...
I try to have all my advance in around 3000 to 3500 rpm. I plug the vacuum advance off, rev the engine up to about 3500 rpm, and set total advance to 34 degrees. Vacuum advance should not be part of your problem, because vacuum drops off if you are pounding on the gas pedal. I don't know about U.S., but here in Canada, Shell V-power is 91 octane and has no ethanol in it. That's what I burn in my '67 R/T with 9.5 compression.
 
IMO...
#25 is correct....ethanol has half the heating value (energy) as in Btu/gallon as gasoline, the fuel mixture MUST BE INCREASED in roughly the same percentage as the ethanol content is increased. IF you are experiencing WOT detonation (aka "pinging"), its usually related to too much distributor advance OR because of the fuel mixture is running lean or some combination of both.
Its easier to reduce the ignition advance slightly BUT consider increase the secondary fuel feed circuit by increasing the secondary metering jets slightly (0.002" - 0.003") and maybe 0.002 on the primary side ad well. The coloration of the spark plugs should offer some results and direction. Delaying the secondary air valve's opening rate by increasing tension of the sir valve's spring will accomplish nothing to fix the issue. If you feel more fuel is required, increase the size of the secondary metering jets. Detonation at WOT under max loads is serious and can result in engine damage.
BOB RENTON
 
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Hey M440,..I usually run 13-15° initial base timing advance with 20° Max centrifugal limited to get my 35° total timing (not counting vac)...Your 20° initial might be agrivating the problem , so try backing down your initial advance & see if it helps...Also, with no bogging, you've got adjustability room to additionally run cooler thermostat & colder plugs..tom.
 
Frank Mopar said:
I put one link up and here is another about spark plug heat range and pinging. A combination of timing, fuel delivery and plug heat range is need for the best performance.

https://www.enginebuildermag.com/2011/05/understanding-spark-plug-heat-range/
Click to expand...

This is where to start. Its gotten 2 common to run a hot plug thinking a cold plug will not last and foul. The mindset has some people backing off compression to run pump gas when they just needed to get away from the oem recommendation and run a colder plug. You could mess with your jets but you should check your afr first... but start w the plugs.
 
Curiousyellow71 said:
This is where to start. Its gotten 2 common to run a hot plug thinking a cold plug will not last and foul. The mindset has some people backing off compression to run pump gas when they just needed to get away from the oem recommendation and run a colder plug. You could mess with your jets but you should check your afr first... but start w the plugs.
Click to expand...

For the past decade, most manufacturers used a hotter (than a normal heat range plug) plug because EGR was introduced in the fuel charge, which lowered the combustion chamber temps to the point cold fouling was possible. Now with VVT engines, external EGR systems have been eliminated in favor or Gasoline Direct Injected engines with high compression ratios (10.5:1 - 11.0:1) using 87 octane fuel.
IMO...Spark plugs do not cause detonation but can be damaged as the result of detonation.....melting of the electrodes and or piston damage. Detonation is USUALLY caused by too much spark advance or lean fuel mixtures or too high compression for the octane of the fuel used, or possibly too high operating temps (inadequate coolant temps or circulation issues) or some combination of all possibilities. The easiest way to proceed is reduce the total amount of advance (both initial and rate of advance), to see if the detonation is reduced or eliminated.
How do you measure the A/F ratio (which is an instantaneous occurance) and if "incorrect", how is it "fixed or adjusted"....by jet changes? Whereas spark plug coloration will provide a "average" of all operating conditions. Just my thoughts...
BOB RENTON
 
I was not particularly pointing toward how the engineering and plugs have changed on newer engines. I was referring to often people try running a hot plug recommended oem for a engine w 7.5:1 and expect it to work in 10:1. The electrode can get so hot it will cause cause detonation, It's really no different then a combustion chamber or piston that has hot spots or poor uneven flame travel which result in preignition. By running a colder plug often you can run more timing before you see detonation. In performance engines plug choice is important and regardless of what anyone thinks it is easy to try changing plugs to see its effect. If the plugs are already a cold heat range for the application then you have to go with less timing, get the engine to run cooler, etc. Agree a/fr is instantaneous. Plug reading is still a good method but a bit of a lost art. I remember shutting the car off at the end of the quarter to pull and check a plug... before we ran afr gauges. Thankfully you can use a tool like this to help in tuning. It will say if you are lean at wot. Its just a tool, detonation will likely change your afr as well. Its up to the tuner to know what 2 change. Holleys are certainly easier to go up a jet size or too then a thermoquad. For a TQ you can change jets to, they use to make street/strips kits available to tune them as well.

Screenshot_20210117-155412_Chrome.jpg
 
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