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Thermostat vs. Pinging

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Morris

Morris

Yoda
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It finally got cold here in Central Texas so I put in a hotter thermostat (195˚F) to keep my tootsies warm. But now I can hear pinging on acceleration. So I wonder what is going to yield the best performance and economy and engine longevity:

1) Keep the ignition advanced and reinstall a cooler thermostat.

or

2) Keep the hot thermostat and retard the advance.

Whadda you guys think?
 
wouldn't have thought those two things are related so will be watching with interest.
 
Sounds like you have carbon builtup on the head.
Run some Seafoam (or just water) thru the intake and maybe you can keep the engine as it is.
BillM
 
Cooler is generally safer for these engines. I'd run a 180F. Should still make enough heat.

If it still pings (or as the Brits say, "pinks"), retard timing at that point.
 
I have a 175 on the shelf that I normally run in the summer. It doesn't keep my feet warm, but I can put on another pair of sox much more easily than I can rebuild the engine... again.
 
Battery powered socks?
 
Assuming no EGR or it has been removed, or maybe headers and not too high a CR, try a tank of 93 fuel. If this doesn't help, then recurve distributor or drop back on timing just a bit. IF the fuel helped, then try some 89. Then go back to 87, if that is what you normally run and tweak the AFR just a bit to richen. Between ignition and fuel, you should be able to cure the problem till spring.

Maybe a t'stat between 175 and 195 could be located? This might tell you where the critical point is with regard to the pinging and temperature.

If plugs are dry and overly white, then maybe a cooler plug will help too.

HTH,
Mike
 
948 stat is 180 degrees, in the winter I need a piece of cardboard over part of the radiator.
 
I think Jack hit the nail on the head. 180deg and some cardboard (block 1/3rd to 1/2 the rad). That's what I'd do...
 
I would tend to :iagree: with Jack and Steve.

Running hotter requires gasoline that doesn't ping at higher temperatures. They are mutually dependent. Also better gas = better mileage and better power.

However: "I wonder what is going to yield the best performance and economy and engine longevity"
Performance, hot like 98-110C is good, but 180F(82C) isn't at all bad.
Economy, very hot is good. (think, ceramic engines ~200C)
longevity, medium temp, never never never too hot. (at least never over 110-115C)

Me bad, I keep my Opel at 80C. It's at the bottom of the gauge. My mileage suffers. I'm only getting 33 mpg.
 
Is this engine using conventional carb/dist. setup or is it a computer/injection type with a wasted spark or coil on plug setup? If you have a custom installation of a ECM (like a 'Squirt" , MOTEC, TEC from Electromotive or the like), the re-mapping fuel to ignition should fix the problem. Might take a few tries, but that is the solution as well.

Thought about the colder T'stat and cardboard as well as the above on the drive to pick up the cylinder head I had cut 0.025" yesterday evening.

I'm categorizing the situation as a fuel/ignition issue at the highter operating temps. That is why plug cuts are still important in racing for the A-Series engines. EGT's and AFR's only show part of the story. The condition of the plugs complete the picture. IMHO, the A-series engines detonate a bit at partial loads if they get too lean.

Have a great new year!
Mike
 
Just to be clear to anyone who has not done this:

Mike's comment about a "plug cut" means reading spark plugs after a hard run up through the gears, holding the car at top speed for a period of time (maybe 10 to 30 seconds or so) and then shutting down the engine and coasting to a halt. Plugs are removed on the spot and "read".
This <span style="text-decoration: underline">must</span> be done with new plugs.
If you shut down and then restart to drive to the pits, the results aren't really valid.
Obviously, this isn't a simple undertaking, but it really works well.

This is also referred to as a "plug chop" or simply, "reading the plugs".

More discussion about this:

HERE

AND HERE (with some BCF members commenting)
 
I always run 93 octane. My CR is about 10.5:1 (I think). I was having a hard time getting a good reading on my combustion chamber volume. I was shooting for 10:1, but I over shaved my head a bit. Oh well... live and learn.

The car is a 1500, with a MegaSquirt control system. Spark is an EDIS (wasted spark) CoilOnPlug hybrid setup with the curve being controlled by the MS. The car is VERY fun to drive with this set up.

I retarded the spark 2 more degrees (with the 195 thermo installed) and I can no longer hear pinging. So far performance and economy seems to be holding up.

I will reinstall my 175 thermo again soon, and try slowly advancing spark. What I really need is a dyno. I should have asked for that from Santa instead of a new angle grinder... live and learn.
 
10.5 to me is on the upper limit of the 93 octane fuels. Modern cars probably get away with using 93 at that CR through using a "knock" or ping sensor and better combustion chamber shaping. The knock sensor would adjust timing based upon readings of whether the engine was pre-igniting or not.

I read something somewhere recently that talked about fuels and how the Motor Octane Number -MON vs Research Octane Number -RON influences fuel performance. In the USA, our pumps show the AKI or Anti-Knock Index or maybe the Pump Octance Number -PON, which is just the averaged number of the MON & RON. Two fuels could have the same AKI, but differing MONs and RONs. If you can find out the MON's and the RON's for some of your local 93 Octane fuel, try and go with a type that has a bit higher MON. This type of fuel is suppossed to be a bit more ping-resistant due to the difference in the MON vs RON testing conditions. If I can remember where it was, I'll provide a notation to it in the future.

Nial-Thanks for the clarificatin on the "Plug-cut" reference.

HTH,
Mike
 
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