Pinging

[ward00]

My 1.8L 75 spider with 10.1 compression pistons and dual IDFs has started to exhibit pinging when I start putting it under slight load when at 3K RPM in 3 and 4th gear. Under the slight load, once I get above 3K RPM the pinging disappears. If I don't lug the engine, there is no pinging

Assuming that using more octane booster, or retarding the timing is off the table (which it is not), I'm wondering what else can be done to try to eliminate the pinging.

The car runs slightly rich in all gears and RPMs (11-13 measured with AF gauge), but changing jets to be leaner would only make things worse right?

Could using a stronger distributer spring (that would reduce advance at lower RPM) help?

[SteinOnkel]

There's a few things that cause pinging or knock. Mainly heat.

1) Too much ignition timing too fast. Perhaps disconnect the vacuum advance. Or pull back initial timing. Or better yet, invest in a programmable box. The CBPerformance black box comes to mind.
2) Too lean a mixture. It sounds like you're having it ping just before the main jets open up, perhaps one size up on the idle jet is in order?
3) Low octane fuel
4) Engine coolant or oil too hot

With 10:1 cr you should not need an octane booster. I run 11.5:1 cr on CA pump gas in my other car (open source efi). I simply don't throw a lot of timing at it, unless I'm on track with race gas. Then I bump up the ignition 3* across the board.

11:1 is far too rich, unless you've got a turbo and you're under full load. I understand these carbs have issues regulating fuel properly, but that is off the charts rich.

Cheers
Steiny

[AndyVAS]

What is your ignition timing at? Both initial and full and what RPM are you seeing full?

What spark plugs are you running?

What AFR are you seeing at the time it pings?

[ward00]

What is your ignition timing at? Both initial and full and what RPM are you seeing full?

What spark plugs are you running?

What AFR are you seeing at the time it pings?

Andy

Adding more additive to gas did not help

Static timing is 9 degrees at about 3200 its at its maximum of about 30 degrees (3200 and below is where it pings). I thought the timing maxed out at a higher degree setting? With 9 degrees initial, what should max advance be?

Sparks are 8kr6eix iridiums - these are not to hot right? Took them our and they were brownish looking - not sooty)

AFR when pinging is about 12 - (the car has always run rich, no matter what I do with the jets its always 13 or less AFR)

Which is leading me to think that I may have built up carbon deposits, since the pinging started only recently, and that I should try throwing some Seafoam into the engine to see if that helps.

[SteinOnkel]

I think you are absolutely spot-on that it is carbon deposits giving your grief. Sea-foam might help.

Where is your PCV routed? My ITB car hates having the PCV blowby sucked in on track and will ping under full load.

I would seriously consider ditching your carbs for something better at regulating fuel. Running constantly below 13 AFR is not doing your engine any favors, especially not your rings. This is all technology from the stone age anyways and was never all that great to begin with. The only carbs I would consider are cv carburettors made in this century by Keihin or Mikuni. The rest is all outdated junk.

Cheers
Steiny

[18Fiatsandcounting]

If the pinging only occurs when the engine is lugging, the solution is very simple: Don't lug the engine. It's hard on bearings and generally not where you want to be. A very slight pinging under occasional operating conditions is generally OK, but if the pinging is heavy, constant, or across the rpm range, that definitely needs addressing.

-Bryan

[SteinOnkel]

"Hey Doc, it hurst when I go like this"

"So don't go like that!"



Seriously though, I would not consider "pinging when I start putting it under slight load when at 3K RPM in 3 and 4th gear." lugging by any means. It should not ping within those parameters.

[ward00]

I think you are absolutely spot-on that it is carbon deposits giving your grief. Sea-foam might help.

Where is your PCV routed? My ITB car hates having the PCV blowby sucked in on track and will ping under full load.

I would seriously consider ditching your carbs for something better at regulating fuel. Running constantly below 13 AFR is not doing your engine any favors, especially not your rings. This is all technology from the stone age anyways and was never all that great to begin with. The only carbs I would consider are cv carburettors made in this century by Keihin or Mikuni. The rest is all outdated junk.

Cheers
Steiny

You touched one of my last remaining neurons. Recently I added a completely closed cold air intake system. The crankcase recirculation hose is now routed to a completely closed system. In fact, I'm finding oily residue in it now, where before, with my open air filter, there was just not that much vacuum to pull it up. The added recirulation gasses and residue might be the issue. On the way home today I'm going to remove the hose and see if there is a difference. If not, Seafoam it is. BTW, what year did Spider start using an actual PCV valve?

[18Fiatsandcounting]

Seriously though, I would not consider "pinging when I start putting it under slight load when at 3K RPM in 3 and 4th gear." lugging by any means. It should not ping within those parameters.

Steiny, I totally agree! Perhaps I was just keying off of ward00's comment that if he didn't lug the engine, it didn't ping.

Slight pinging under occasional conditions = OK in my book. Heavy pinging, and perhaps what ward00 is experiencing = not OK. I also recall in my studies of engine performance that optimal power can be developed in an engine with slight ping (slight, not heavy/continuous).

-Bryan

[AndyVAS]

Put in a set of normal spark plugs. The DOHC motors don't like fancy plugs.

You timing is close enough. Total advance between 3k and 3500rpms is right.

They never ran a PCV. Just crank vent to the filter side of the throttle. The EFI cars had the vent very close to the throttle without issue. Just be sure the cyclonic trap is in the hose or it will ingest a lot of oil.