Ram Ping - Causes and Elimination

Dodge Ram Magnum engines have gained a reputation for persistent engine ping. Many people have been working to solve the problem (some with success) and posting thair findings to the DiRT list. Here are some of the excerpts:

What causes ping?

   One of the results of all the years of detonation research is this - when you compress a gas, both the pressure and temperature go up. At a high enough compression you begin to get pinging.
   Is it the higher temperature - or the higher pressure - or both - that causes the ping? The answer turned out to be that it is mostly the higher temperature of the last bit of mixture that burns - the so called 'end gas.' The end gas needs to be kept less than about 1900 degrees. Pressure doesn't seem to matter much.   This is the discovery that led to fitting intercoolers to turbo/superchargers. Intercooling is a way to partially compress - then cool - then compress the rest of the way. A supercharger that gives you 15 psi of boost is like a compression ratio of 2x. If you then feed this 2x into a cylinder with a compression ratio of 7, it is like you had a total compression of 2 x 7 = 14. This will work without pinging, but if you tried to run an engine with a compression ratio of 14 to begin with, it would almost surely ping. If interested, you can read about this in "The Internal Combustion Engine in Theory and Practice, vol 2" by CF Taylor on page 59. ISBN 0-262-70027-1 That whole chapter is about 50 years of research at MIT on how to reduce pinging.

There is mostly bad news about part-throttle operation and pinging.

   The O2 sensor and the PCM try to control the air/fuel mixture at 14.7 air to 1 when you are driving around at less than full throttle. This is because the catalytic converter needs the air/fuel mixture to fluctuate back and forth near 14.7 to 1 mixture so that the cat converter can reduce the three bad things: NOx, HC, and CO. Unfortunately, 14.7 to 1 mixture IS THE ABSOLUTE WORSE MIXTURE FOR CAUSING PINGING but it is the mixture that the engine has to run at for pollution control. 14.7 is where the temperature of the gases in the cylinder, and the speed of the combustion are highest. Even if your MAP sensor or IAT sensors are off a little, it doesn't matter at part-throttle, because the O2 sensor will constantly 'self-correct' to the 14.7 range. If it pings less at full throttle, then that means that your PCM is correctly enriching the mixture. So to get rid of part-throttle ping, so need to think 'cold' coolant or cold air.
   There is no use to check the IAT or MAP sensors if it is pinging at part-throttle. A partially clogged fuel injector also is not likely to be the problem if part-throttle pinging is occurring.
If your truck pings worse at part throttle, then that limits what you can do to stop it.
   When you hear a racer say: "One of my cylinders got a little too lean and then detonation blew a hole in that piston," what he really means in "Engineer Speak" is: "My mixture was running at the best-power ratio of 13 to 1, then something happened and one of the cylinders' mixture began to drift leaner and leaner until it got close to 14.7 where detonation began. "

   In the January 2000 issue of High Performance Mopar, there is an article about what a good machine shop does when they build up a Mopar engine. The article is about Roger's Engine Shop (RES) in Lansing Michigan, which apparently specializes in Mopars. The title of the article is "Bottom End Beef Up."  In the article RES is complimentary about the quality of late-model Mopar blocks, and says that mopar connecting rods are first rate, but says this about Mopar crankshafts:
(begin quote) ----------------- "Most OEM crankshafts are out of stroke spec, some by as much as 0.025 to 0.050 ! That means you'll be down on cubes in one or all cylinders. Indexing the crank is a time-honored way of ensuring you engine makes all the cubic inches advertised. Additionally, the as-delivered factory cranks seldom place the rod journals at 90-degree intervals, so timing the ignition and cam is off. " ------------------ (end quote)
   Obviously there may be a bit of 'hyping' in these statements in order to draw in crank grinding business to their shop, but it got me to wondering about Mopar crankshafts and the reports on Dirt of pinging in 318/360 engines that sometimes defies easy cure. While the article emphasizes the small loss of cubic inches from a crankshaft having undersized stroke, a crankshaft that had an OVERSIZED stroke on one cylinder of 0.050 inches would have increased compression ratio in that cylinder.
   An oversized stroke of 0.050 from 3.58 to 3.63 inches would bump the compression ratio from the 360's spec of 8.9 to about 9.4 So that cylinder would tend to ping earlier than the other seven cylinders. If the rod journal on the crank of that cylinder happened to be at 91 degrees rather than 90, that could cause further ping problems, because even if the sparkplug is fired at the correct time, the piston is one degree short of where it should be. In this condition the cylinder would act like its ignition timing had been advanced a degree.
   So maybe "Mystery Ping" on Magnum 5.2/5.9 V8's could be related to sloppy tolerances on crankshafts - which are very very seldom pulled out at a dealership and measured. If the machining on the deck height of the block, and the underside of the head were slightly off-spec on the too-small side, this would make things even worse. The article in High Performance Mopar is worth a browse if you are killing time near a magazine rack.


Solution one: Reroute/replace the spark plug wires

Check/replace the spark plug wires. Even on engines with few miles, many have experienced pinging problems caused by bad spark plug wires. One cylinder (maybe more) would misfire, causing the ECM to detect a rich condition, and lean out the mixture to the other cylinders, causing the engine to ping. Look for open wires, intermittent wires, and leaking wires (look for leaky wires on a dark, damp night).

Wire rerouting:   You don't need to buy the overpriced Dodge parts listed, just look at the passenger side of your engine and examine the wire clips that push down in the valve cover bolts. Go to an auto parts store and buy some of these, plus some nylon wire ties and some of that blacksplit plastic tubing (Dodge calls this 'convolute') to cover & protect wire.

Solution two: Replace a leaking intake manifold and plenum gaskets

Chrysler now recommends a more sensitive test to see if the Magnum V8 intake manifold to block gaskets are leaking. If this gasket is leaking, it can cause the engine to ping.
    The old test (I think it is described in the TSB's) was to take the PCV valve loose from the passenger side of the engine and oil vapor breather-to-air cleaner hose loose from the driver's side.
    With the engine running at idle, use your two thumbs to seal the PCV valve hole on the passenger side and seal the hose going to the valve cover on the driver's side.
    Wait a few seconds. If you feel a slight pressure building up due to blowby gases filling the engine block's interior - your engine is normal and your manifold to block gasket is probably ok.
    If you feel a slight vacuum - your manifold-to-block gasket may be bad and one or more leaks is allowing the high vacuum in the manifold to suck the gases out of the interior of the block.

Many technicians now feel the above method only finds really bad leaks.

    To find the lesser leaks they recommend putting two doses of 4-IN-1 Blacklight dye (Mopar part number 05010042AA /cost $8 per tiny bottle) in the engine oil and driving the truck for 200-300 miles.
    They then take off the air cleaner and shine a blacklight down into the throttle body. If they see ultraviolet dye glowing on the bottom floor of the intake manifold - they take the manifold off and re-do the gasket.
    I thought about that - it sounded good - but then I remembered that the PCV valve empties into the intake manifold - and the oil vapor breather empties into the air cleaner housing which is almost the same thing. I asked him, "Wouldn't some dye find its way into the manifold through the PCV and the breather even if there was not a leak?"     He said, "We haven't found that to be a problem."
    I bought two bottles of the blacklight dye - but I may temporarily disconnect my PCV and breather for the 200 mile test anyway - because for out-of-warranty work I would be the one to pay if they misdiagnosed a leak that wasn't there.       Hank

Solution three: Replace or Reprogram the PCM

Solution 4: Replace thermostat, antifreeze, and/or radiator cap

   A cooler 180 degree thermostat and cooler intake air will reduce the tendency to ping at part-throttle. The 180 not only causes the truck to run cooler (reducing the intake air charge temp), but it also causes the truck to run cooler (this fools the computer, which believes that the truck is not completely warmed up so it runs a richer air\fuel mix).
    Some have even used a 170 degree thermostat. Each 5 degrees of thermostat drop is supposed to be about like adding 1 Octane number to that of whatever gasoline you are using. The 170 thermostat may set a fault code for "Engine operating temperature not achieved in specified time" and illuminate the "Check Engine" light. Some have experienced this, others have not set the fault code.
    According to Dakota Power Secrets in the January 1999 issue of Mopar Muscle, the Magnum thermostat is rated at 195 degrees F. The engine controller is designed to make maximum power at 182 deg F. Especially with a high performance engine computer, the engine generates high combustion chamber temperatures under heavy throttle conditions and this heat is transferred to the coolant above the chamber. The hot coolant forms air pockets that create combustion chamber hot spots; engine ping is the result. Dropping the thermostat to 185 or 180 degrees will stop most of the coolant pocketing, and the engine fuel economy and power will improve.

   Another cheap thing that helps your cooling system to suppress pinging is to change out your 16 lb radiator cap to a 20 lb radiator cap. Mercedes, BMW and Caddilac vehicles use 20lb radiator caps and they will fit the Ram's radiator. Cost about $12.
    The 20 psi cap will help suppress a thing called 'nucleate boiling' of the coolant on the hot spots of the cylinder head. This is where the metal is so hot that a steam bubble forms. More pressure makes the bubbles harder to form. Be sure to switch radiator caps when the engine is dead cold - not just for safety - but because the cap needs a cold coolant to fully build up the 20 psi pressure as it gets hot.
   Along the same lines you could drain out 5 quarts of the 50/50 ethylene glycol/water coolant that is in your engine and replace it with 5 quarts of pure ethylene glycol. Cost about $8. There are 15 quarts total in the Ram's cooling system, so this substitution with make your system consist of the 5 fresh quarts of new EG, plus 10 old quarts that are a 50/50 mixture (ie 5 quarts EG and 5 quarts water). The new mixture therefore is 10 quarts total EG plus 5 quarts water. This is 66% ethylene glycol and 33% water. This is the greatest mixture of EG that Chrysler recommends - any more and the dissolved corrosion additives will drop out of the mixture and plug radiator tubes. A 66% mixture has good and bad points: it does tend to help eliminate cylinder head hot spots/steam bubbles and hence lessen ping - but it can't quite carry away as much total heat from engine to radiator as either straight water or a 50/50 mixture. You probably won't notice this lessened heat carrying ability unless you tow a trailer up a mountain pass.

Solution 5: Change fuel, add octane booster, use fuel system cleaner

For ping at WOT only, try a higher octane gasoline.
For part throttle ping:

   If you run a cylinder compression test and find one or more cylinders that measure higher than 170-180 psi, there is a good chance that it will ping on anything less than high octane gasoline. A build up of carbon deposits on the piston tops (from engine oil leaking through an intake valve stem seal or intake manifold gasket) is the most common cause of high compression readings from one/two cylinders.
    For engines with carbon buildup or persistent part throttle ping, run through three Techron treatments. Let your gas tank get down to one quarter full (about 8 gallons to dry) and add a $7 bottle of Chevron Techron. Run this down to empty. Then add 12 gallons more gasoline and add another bottle of Techron. Run this to empty, add 12 more gallons plus a third bottle of Techron. What this will do is clean out carbon deposits out of your combustion chambers and lower your compression ratio back to the factory 8.8 number it had when the cylinder was clean shiny metal. It is a cheap thing to do and I almost guarantee it will lessen the pinging on 93 octane. Carbon deposits not only raise compression - it also insulates the cylinder head and prevents good cooling from above. The Techron may also clean out a partially plugged fuel injector that is causing one cylinder to run leaner than the other seven. This is the same problem as the low fuel pressure but is confined to one cylinder. There is no guarantee that a Techron treatment will completely eliminate the pinging.

Chrysler has a combustion chamber cleaner that the service departments use.   

Here is some more info on heavier-duty injector cleaning:
For off-the-engine cleaning, with three manufacturer's systems reviewed: http://www.asashop.org/autoinc/sept98/techtotech.htm
For on-the-engine cleaning: http://www.asashop.org/autoinc/june98/techtotech.htm
{These are very well written, comprehensive articles.}

   Get your dealer to check your fuel pressure - on the road - at wide open throttle acceleration at 75 mph in 2nd gear. Hook up the gauge with a short hose extension and tape it to the windshield so you and the service guy can see it. It should be 49.5 psi or better. Any less and your fuel injectors are not putting out what the computer is expecting them to. This will cause your engine at WOT to run lean above 14.7 Air/Fuel when Mopar expects good fuel injector flow to make it slightly richer (say 13.7) to suppress pinging. Pinging is at its absolute worse at about 15 to one.

Solution 6: Change to cooler spark plugs - Stock OEM: Champion RC12YC

Equivalent-to-stock, normal heat range plugs for 5.2/5.9 V8 engines

   RC12YC - The 12 is the heat range. Higher is hotter with Champions. You can buy a RC10YC or a RC09YC (stock numbers 4434 and 4412). All will be progressively colder than the factory stock RC12YC.
    If you need a colder range than the Champion RC9YC, page 23 of the "High Performance Heat Range Chart and Tuning Guide" says that Champion Racing plugs C63YC, C61YC, C59YC and C57YC are available. Here the '63' to '57' are the very cold racing heat ranges. Plugs that are too cold can make the engine a cold-tempered beast - hard to start and warm up in cold temperatures, and prone to fouling.

Stock recommended gap is .035 but many have been measured at .040 to .065.

   Bosch 4+ and Splitfire sparkplugs have a reputation for pinging in Magnum engines. Champion Truckplugs or the Bosch regular platinum FR7DPX seem to work best, particularly in the number 7 and 8 cylinders because they seem to run the hottest.
    If your counterguys are really clueless and can only find plugs by car model - tell them to give you the : {Sparkplug Manufacturer of Your Choice} plug for the 1995 Dodge Stealth 3.0L V6 Turbo - this car's engine is turbocharged but the cylinder head design is similar to the Magnum V8. It takes one heat range colder than the Ram, otherwise it is the same style/thread sparkplug. NGK recommends the platinum tipped PFR6J-11, stock number 2743 for the Dodge Stealth turbo.
    Champion distributes a little booklet with good color photos about reading plugs after test runs called "High Performance Heat Range Chart and Tuning Guide". It is Publication Reorder Number 98770 and Champion will send it to you for free.
   Buying 16 plugs, and finding the 8 that stop or "index" correctly at the best angle by chance, is worth the extra time and money. The Magnum 'Squish and Quench' cylinder head design seems to like indexing. To Index: Aim the side of the sparkplug with the open gap toward the center of the engine.

    If you are running the KN FIPK with the inlet inside the engine compartment, that might be something to try changing. Engine compartment air is higher temperature - and higher inlet temperatures lead to higher temperatures at every stage of combustion.

Solution 7: Check/replace the EGR valve

Gasoline engines run an aggressive spark advance curve and rely on EGR to prevent engine ping. If the EGR valve has clogged or stuck (or been blocked by those seeking to improve mileage), the quick advance curve will cause the engine to ping. If all else has failed, verify that the EGR circuit is functioning properly.

Solution 8: Water Injection

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I did a lot of "cut and paste" on this page. If you find errors, let me know. Dave

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Last Update: March 22, 2000