Newer cars and engine compression ratios...

[Phil Thien]

Just had an opportunity to drive a new Toyota Corolla while visiting another state, and felt that it was pinging a little.

I suspect my 2009 Honda Odyssey requires at least mid-grade fuel (89 octane instead of 87) in order to avoid pinging. I use the premium (93) because I was so freaked out at the amount of pinging on 87 that I wanted it to stop to prevent engine damage.

Internet research seemed to indicate Honda used an engine with formula-car type compression to get the mileage up (I guess the Odyssey is something like 10.5 or 11:1).

Are all newer cars the same? Is this a CAFE (Corporate Average Fuel Economy) issue or what?

I'm impressed a car the size of the Odyssey can get 25-MPG on the highway (the 2011 apparently gets 27-MPG on the highway), but you pay for that performance via higher prices at the pump. Just wondering if other brands/models are the same.

[Ken Fitzgerald]

Phil,

I am driving a 2005 Honda Pilot. It gets 25 mpg on the highway and it's 4WD/AWD. I alternate one tank low grade, the next middle grade. We live in what was a seperate community and we are about 800' higher in elevation than the downtown area. Some of the streets leading up to the "Orchards" are 11% grades. Thus I want a little more octane.

[Phil Thien]

Phil,

I am driving a 2005 Honda Pilot. It gets 25 mpg on the highway and it's 4WD/AWD. I alternate one tank low grade, the next middle grade. We live in what was a seperate community and we are about 800' higher in elevation than the downtown area. Some of the streets leading up to the "Orchards" are 11% grades. Thus I want a little more octane.

So you top-off the tank when it is half-empty (or half-full)? Or do you run it nearly dry before filling up?

[Ken Fitzgerald]

I fill it when it gets to about a 1/4-1/2 of a tank left. In the winter time, I don't like to get below 1/4 tank in case there might be some water in it. I don't want it to get into a gas line and freeze. While we are pretty mild here compared to the surrounding area, I've seen -10-12º F. They are talking low teens and blizzard conditions for the next few days, so this evening I made a special trip to fill up.

My wife drives a 2003 Honda Accord v-6 and I've seen it get 29 mpg on the highway. She gets better mileage driving it than I do for 2 reasons. 1) If it's mountainous, winding roads, she'll ask me if I'd like to drive and I will. 2) She doesn't drive as aggresively as I do. I don't speed but if I slow down, I'll get back up to the speed limit faster than she will and it shows in the mileage. All she uses is low grade.

[Rob Vicelli]

HI Phil, i did not see where you mentioned if it was a 6, 4 or Hybryd?? Anyway the regular engines use variable cam timng to eliminate help avoid gas knock associated to high combustion chamber temps which contributes to gas knock (ping). I would find it very strange that that vehcile would have a ping without some type of light coming on, They moniter for knocking/ping. ANyway you should be able to follow what ever the recommendations of the manufacuturer are listed in the manual for octane, If it still pings....something is wrong

[Phil Thien]

HI Phil, i did not see where you mentioned if it was a 6, 4 or Hybryd?? Anyway the regular engines use variable cam timng to eliminate help avoid gas knock associated to high combustion chamber temps which contributes to gas knock (ping). I would find it very strange that that vehcile would have a ping without some type of light coming on, They moniter for knocking/ping. ANyway you should be able to follow what ever the recommendations of the manufacuturer are listed in the manual for octane, If it still pings....something is wrong

The ping is very subtle. Yes, they have knock sensors and variable timing, but in engines with high compression ratios they can only do so much. (BTW, this is what I've read, I'm not an expert on gasoline engines.) At certain RPM's/loads, you can hear very subtle pinging.

Manufacturers are hesitant to tell people to use premium fuels, and whatever damage occurs to the engine is likely going to happen beyond the standard warranty period.

BTW, I'm not sure what the Toyota was, it sure drove like a 4. My Odyssey is a 6.

So I can use 87 octane and (IMHO) shorten the life of my engine, or I can just suck it up and use 89 or 93-octane and try to maximize engine life.

I was just surprised when I got into the Toyota and noticed the same thing going on. It doesn't hit you like a ton of bricks, but it is there.

[Paul Ryan]

Phil,

I would be real suprised if it was pinging you were hearing. As others said with the diagnostics that are built in the cars today if you had consistent pining going on your SES light would have some on. I also really doubt that the compression ratio of the engine is 10.5 or higher. Most engines are designed to be run on 87 or 89 octane fuel and that would be about a 8-9.5 ratio. Higher octane will not necessarily raise fuel mileage or power. In many cases running a higher octane will lower your fuel mileage. A higher octane fuel burns cooler and will lower engine temps and reduce a high temp "ping" but could cause other problems in other cases. Higher elevations require a lower octane fuel due to less oxygen in the air. In this case oxygenated fuels can help. Read your "super secret" document that came with the car, that is what technicians call it because no one reads them. In many cases it is called an owners manual. It will tell you what octane to run. I drive around 1000 miles a week in a 07 chrysler sebring 4 cylinder. It gets 33 mpg in the summer and about 30 in the winter on 87 octane gas with 15% ethanol. Winter gas has all sorts of additives that reduce your mileage in order to prevent some drivability issues. If I switch to 89 I will loose aproximatly 1 mpg. If I fill up in Iowa at a station that sells straight gas with out ethanol I have gotten as high as 36 in the summer. So I guess what I am trying to explain is that high octane fuel usually reduces fuel ecomomy due to engine designs. Higher engine temps will provide the best fuel economy and higher octane fuels reduce that in many cases. A lot more goes into that just octane or compression ratios. I could go on a on about emissions and, engine temps, compression ratios, and fuels. But run the fuel that your owners manual recommends. If the SES light comes on because of it some thing is wrong.

[Phil Thien]

Phil,

I would be real suprised if it was pinging you were hearing. As others said with the diagnostics that are built in the cars today if you had consistent pining going on your SES light would have some on. I also really doubt that the compression ratio of the engine is 10.5 or higher. Most engines are designed to be run on 87 or 89 octane fuel and that would be about a 8-9.5 ratio.

2011 Honda Odyssey Compression ratios (10.5):

http://automobiles.honda.com/accord-sedan/specifications.aspx

The 2010 is 10.0, but I can't find an official Honda page saying so. Google has the answers, though.

It is absolutely pinging. If you google "honda odyssey pinging" you can read plenty of other people that have discussed same.

I'm doing more googling now, and it apparently is occuring with more and more newer engines. Not only Honda.

When summer comes around again I'm going to try 89 octane in the Odyssey and see if it works as well as 93.

[Bob Turkovich]

Phil,

Ditto to what Rob is saying. You shouldn't have to run higher octane than what the manufacturer recommends for that specific engine/vehicle combination. If you're running the recommended octane and getting ping you should be setting a light - if not, something's wrong and needs to be checked out.

Contrary to Ken's comment - running a higher octane than recommended gains you little or nothing as the engine calibration is based off of the recommended octane. Some manufacturers will program the engine controller with two calibrations to run at two different octane levels. In this case, they will recommend the higher octane (for better FE & performance) but - if sensing that a lower octane is in the tank - the contoller will run the second calibration to protect the engine.

BTW -in today's auto industry, it's always about CAFE.

[Chris Parks]

I will back what the others have said, it has an issue. The knock sensors retard the timing and power drops if the fuel octane is too low. Make sure you can replicate it and take a technician for a ride to show him. The knock sensor may have failed, thus no timing change.

[Dan Hintz]

My S2000 has an 11:1 compression, and it's 10 years old...

[Phil Thien]

I will back what the others have said, it has an issue. The knock sensors retard the timing and power drops if the fuel octane is too low. Make sure you can replicate it and take a technician for a ride to show him. The knock sensor may have failed, thus no timing change.

LOL. Here, this article summarizes things perfectly:

http://www.cartalk.com/content/features/premium/questions.html

Now let me just state that the matter is complicated a little by the fact that the car seems to use overdrive a lot. That is, it skips to a higher gear and runs the engine at lower RPM while "cruising." And let me also state that I notice the problem in hotter weather (in summer). Not so much in winter. Finally, allow me to state that I recently had a "transmission software upgrade" due to a recall. And I haven't driven in summer since. I do notice slightly different shifting.

But seeing as I'm not the primary driver of the car (wife/kid), and seeing as I can't be there to listen if the engine is pinging when they are driving, I feel more comfortable running premium.

But you'll note in the car-talk article that they say "Why? Because there's only so much that your car's knock sensor and computer can do to adjust the engine's timing." I've heard that advice on the show, as well, where they told a caller that at higher compression ratios, there is only so much the computer can do to avoid pinging.

[Chris Parks]

I haven't heard a car ping in many years, so long in fact that I can't remember the last time it happened. I would think that a knock sensor and the car's ECU would eliminate knocking within the range of normal fuels for that market, in other words they look at the octane range for a given market and create a fuel and ignition map for that market. The reason the car lugs in higher gears is purely to increase the fuel economy, all cars do it now without exception and today's autos sometimes have a sports mode to bring things back to what you or I might call normal and are more used to in times gone by. Either Honda have not gotten the fuel and ignition map right or there is an issue, either way I would be jumping up and down to get it rectified as the car is not operating outside its designed parameters and it should not knock. It is possible there maybe a software upgrade if Honda have found an issue, it certainly doesn't hurt to ask.

[Dan Hintz]

The problem with relying on ping sensors to handle constant use of poor gas is they are constantly being called upon to retard the timing. When the ECU no longer hears pinging, it will slowly dial the timing retard back out... which leads to pinging, and the problem starts all over again. This cycle starts again every few minutes. Even a single ping is damaging to some small degree, but having ping happen over and over again on every single trip starts to add up.

[Steven Hardy]

I have a 2010 fusion with a 2.5 litre. I use only 87 octane and it never pings...even while driving in the heat of florida.

[Phil Thien]

I have a 2010 fusion with a 2.5 litre. I use only 87 octane and it never pings...even while driving in the heat of florida.

That engine is 9.7:1 compression. The 6 cyclinder is 10.3:1, and apparently Ford uses TWO knock sensors to hear ping and retard the timing so you can use 87 octane.

Adaptive Spark Ignition. Included on the V-6 configurations, this system can sense what type of fuel is being injected into the motor and communicates the information to the powertrain control module (PCM), which adjusts the spark accordingly. The ignition system features two knock sensors rather than one to further improve performance. These two sensors detect the presence of uncontrolled burning in the chambers more accurately, so the control module can retard engine timing as needed to eliminate the potential for engine knock and pinging. As a result, V6 engines run equally smoothly and are able to deliver power ratings on regular unleaded fuel instead of the more expensive premium.

Source: http://media.ford.com/article_display.cfm?article_id=29450

I highlighted "eliminate the potential for engine knock and pinging" because it just strikes me as odd. They retard timing when the sensors detect pinging. So if timing is retarded because the sensors detected pinging, how exactly is the potential for knock and pinging eliminated?

[Chris Parks]

The problem with relying on ping sensors to handle constant use of poor gas is they are constantly being called upon to retard the timing. When the ECU no longer hears pinging, it will slowly dial the timing retard back out... which leads to pinging, and the problem starts all over again. This cycle starts again every few minutes. Even a single ping is damaging to some small degree, but having ping happen over and over again on every single trip starts to add up.

Detonation causes damage, pinging is not detonation and causes no damage.

[Dan Hintz]

Detonation causes damage, pinging is not detonation and causes no damage.
The ping sound you hear is an unintended, uncontrolled detonation of the gas/air mixture... what name you choose to call it is irrelevant. The wavefront from the unintended detonation hits parts before they are ready to be hit, putting extra stress on linked components. If you're lucky, the unintended detonation happens at roughly the same time as your sparkplug fires, so it's roughly the correct time to apply pressure to the piston, but stray too far from that ideal time and you have a pressure wave pushing when it shouldn't... that's always bad.

[Bob Turkovich]

Detonation causes damage, pinging is not detonation and causes no damage.

So....what do you consider the difference is between pinging and detonation?

[Phil Thien]

So....what do you consider the difference is between pinging and detonation?

Pinging is simply premature detonation. The air/fuel mix detonates before the spark, because it is sufficiently compressed in a very hot cylinder. The higher the octane of the fuel, the more resistant it is to premature detonation.

[Dan Hintz]

Phil,

I think Bob's question to Chris was pointing out Chris's belief that pinging is somehow different than detonation and therefore safe for the engine.

[Stephen Tashiro]

Phil,

I think Bob's question to Chris was pointing out Chris's belief that pinging is somehow different than detonation and therefore safe for the engine.

Pinging is premature detonation, but perhaps not all premature detonation causes pinging. This might bear on you previous question of why sensors should work. Perhaps they can sense the detonation is "premature" before things get to the point where there is a ping.

[Bob Turkovich]

Dan,

Yep.....that is indeed my question. I've always heard the two terms used interchangeably (sp?). If detonation is considered "heavy pinging" then I'll respectfully disagree with Chris's point that pinging won't eventually lead to issues.

[Phil Thien]

Phil,

I think Bob's question to Chris was pointing out Chris's belief that pinging is somehow different than detonation and therefore safe for the engine.


Sorry Bob, I didn't catch that. Too much caffeine in the morning.

[Phil Thien]

Dan,

Yep.....that is indeed my question. I've always heard the two terms used interchangeably (sp?). If detonation is considered "heavy pinging" then I'll respectfully disagree with Chris's point that pinging won't eventually lead to issues.

My concern is, if an engine's control unit uses the knock sensor in a feedback loop to control engine timing, they are basically reactive to pinging, not proactive. So the system prevents significant pinging, but it uses nominal pinging as the input to do so. I don't know this for sure, I'm making a lot of assumptions based upon my experience in designing control systems for industry (and that is experience from 20+ years ago).

And compression isn't the only factor, apparently. The design of the cylinder/piston are also factors. Some engine designs will obviously handle lower octanes better than others.

But my nagging question is, what is the cumulative effect of any nominal pinging that occurs over many years?

[Dan Hintz]

Phil,

This is what I was alluding to in my earlier post... any amount of detonation (including what some people seem to be calling "pinging") is bad. If it's kept small, the cumulative effects are obviously better off than if it's allowed to grow larger, but it's still a cumulative problem. The ECUs need to hear the little pings so they can prevent the big ones, but it's still pinging / detonating when it shouldn't. The ECU will retard timing until the pinging disappears, but being a closed loop system that wants to provide the most power for the given gas, it will eventually start to add the timing back in... all leading back to the beginning again.

Cylinder design isn't a huge factor in so much as it's either compression or hot points that cause the premature detonation. Carbon buildup in older engines create hotspots, which are major points of a detonation nucleus... the cylinders themselves rarely have sharp points. Too low of octane for a given compression will lead to premature detonation in the same manner that a diesel engine ignites the mixture via pressure rather than a sparkplug.

[Phil Thien]

Thanks for the information, Dan.

Maybe some day someone will publish an article or paper about the long-term use of "regular" gas in higher-compression engines. If you ever see one please let me know.

[Stephen Tashiro]

The ECUs need to hear the little pings so they can prevent the big ones

Do their sensors actually detect the sound of pinging? I'd think that a pressure sensor would be theoretically the best sensor to have. I wonder if there is a sensor that can stand up to that.

...and Chris may be able to defend his point of view with the technicalities in the Wikipedia article on "Engine knocking".

[Dan Hintz]

Stephen,

The sensors are tuned for specific frequencies, generally the resonance frequency of the cylinder. A pressure sensor would be living in a very nasty environment... high pressure, high heat.

[Dave Wagner]

My 2003 mustang is 10.5:1 compression and 32 valve (305HP) and it will ping with anything less then 91 octane. It gets 25-27MPG on the highway (Not lead footing it of course), otherwise, a solid 23-25 on the highway.

[Dan Hintz]

Hmmm, kinda forgot... my 370Z also has 11:1 compression. I guess I have two high-strung vehicles outside ;) The Z only gets about 24mpg, though, mostly highway.

[David Nelson1]

My only comment to this discussion is to point out that 10:1 or 11:1 compression ratios are the advertised ratios. Usually the static compression that the engine can mathmatically achieve. Calculations rely on piston bore, piston stroke the, pistion to block relief, thickness of the head gasket, and combustion chamber volume. The second ratio is harder to calculate because it's dynamic and relies on cam profile specification such as duration, lobe lift , rocker arm ratio, and over lap.

Engine rpm also plays into this factor. slower speeds allow (depending again on over lap and duration) combustion pressure to bleed off which will allow the use of a slightly less octane. As vehicle speeds increase engine rpm decrease because we shift gears and should still allow for a lower octane gas. Only in extreme circumstances ie, heavy acceleration while in the wrong gear or climbing a steep grade the engine and ECU should perform within the parameters set by the manufactor.

In conclusion, in my experiences, certain variable have been the problem with pinging/detonation. Vaccum leaks, worn valve guides, excessive carbon deposits, bad gas, and malfuntioning engine controls. Following the manufactors required octane rating should result in absolutly no pinging.

If the right gas is being used there is the old problem of deficient engineering on the manufactures part.

How about an after market PROM that can be adjusted by the user? Of course if you can find one you will be looking for a CARB certification if you are required to partipate in vehicle smog testing.

[Paul Ryan]

Thanks for the information, Dan.

Maybe some day someone will publish an article or paper about the long-term use of "regular" gas in higher-compression engines. If you ever see one please let me know.

I have seen what type of damage lower octane fuel does. It starts by small hot spots on the piston. Then the side of the piston starts to melt and deteriorate and eventually the damage reaches the upper compression ring. The cylinder head is usually damaged too. The time it takes depends on the severity of the ping/knock, the length of time, and how much heat. Heat is usually the biggest culprit to pining. You can get by with lower octane fuels if the temp is lower or the altitude is high. I have a 96 ram that is designed to be run on 87 octane gas. But on real warm summer days when going up hills is will ping a little. I run 89 octane in it year round to take care of this. The magnum motors were known for this because the timing is right on the edge and the older ones 96 or older run OBD I diagnositic which has a much higher tolerance for miss fires than OBD II or latter. Bottom line is any pinging while burning the recommended fuel by any late model car is not good and should be checked out. Honda could have a flash to resolved the problem.

By the way knock sensors on a V6 are mounted in the valley of the engine 1 for each bank of cylinders. They are not very precises instruments. As Dan alluded to they pick harmonic variations. Some times a severe ping can be required to make changes, but in most cases you wont feel anything and they will be "counting up".

[Dan Hintz]

the older ones 96 or older run OBD I diagnositic which has a much higher tolerance for miss fires than OBD II or latter.
OBD-I versus OBD-II is simply a difference in communications protocol (and available system information) and therefore has no difference on an ECU's tolerance to pinging. That said, the manufacturer may have set their tolerance higher on OBD-I vehicles, or the extra info on OBD-II equipped vehicles would allow them to run with more sensors, but it's not a direct correlation.

[Chris Parks]

I have seen what type of damage lower octane fuel does. It starts by small hot spots on the piston. Then the side of the piston starts to melt and deteriorate and eventually the damage reaches the upper compression ring. The cylinder head is usually damaged too. The time it takes depends on the severity of the ping/knock, the length of time, and how much heat. Heat is usually the biggest culprit to pining. You can get by with lower octane fuels if the temp is lower or the altitude is high. I have a 96 ram that is designed to be run on 87 octane gas. But on real warm summer days when going up hills is will ping a little. I run 89 octane in it year round to take care of this. The magnum motors were known for this because the timing is right on the edge and the older ones 96 or older run OBD I diagnositic which has a much higher tolerance for miss fires than OBD II or latter. Bottom line is any pinging while burning the recommended fuel by any late model car is not good and should be checked out. Honda could have a flash to resolved the problem.

By the way knock sensors on a V6 are mounted in the valley of the engine 1 for each bank of cylinders. They are not very precises instruments. As Dan alluded to they pick harmonic variations. Some times a severe ping can be required to make changes, but in most cases you wont feel anything and they will be "counting up".

What is described above IS NOT PINGING IT IS DETONATION. Please remember that and don't alarm people whose motors might ping a few times and then think it might blow up.

[Dan Hintz]

What is described above IS NOT PINGING IT IS DETONATION. Please remember that and don't alarm people whose motors might ping a few times and then think it might blow up.
Pinging is simply a feel-good word for unintended, low-level detonation... a rose by any other name. Please remember that and don't lull people into a false sense of security by calling an undesired explosion a hiccup.

[Karl Brogger]

my vehicle has a 17.1:1 compression ratio, no pinging. Lots of knocking, but no ping.:D



I like the baloney statement of F1 style compression ratio. Well, maybe.... but not when you factor in that the minivan isn't turbo charged, and runs on regular gasoline it just becomes a marketing ploy.

[Chris Parks]

Ok, I will play the game, please explain to everyone reading this the difference between pinging and detonation, especially when both happen and why. Pinging as experienced by Phil (OP) will hurt nothing.

[Phil Thien]

Ok, I will play the game, please explain to everyone reading this the difference between pinging and detonation, especially when both happen and why. Pinging as experienced by Phil (OP) will hurt nothing.

From Wikipedia:


Knocking (also called knock, detonation, spark knock, pinging or pinking) in spark-ignition internal combustion engines (http://en.wikipedia.org/wiki/Internal_combustion_engine) occurs when combustion of the air/fuel mixture (http://en.wikipedia.org/wiki/Air-fuel_ratio) in the cylinder starts off correctly in response to ignition by the spark plug (http://en.wikipedia.org/wiki/Spark_plug), but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel-air charge is meant to be ignited by the spark plug only, and at a precise time in the piston's stroke cycle. The peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle (http://en.wikipedia.org/wiki/Four-stroke_cycle). The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive. It should not be confused with pre-ignition (also discussed in this article).

Seems to confirm: (1) Pinging = detonation. (2) Effects range from inconsequential to completely destructive.

I'd love to take your word for it that the pinging I've heard will hurt nothing, my common sense tells me otherwise.

[Bob Turkovich]

What is described above IS NOT PINGING IT IS DETONATION. Please remember that and don't alarm people whose motors might ping a few times and then think it might blow up.

Chris,

Maybe you missed my earlier post where I asked what you considered the difference between pinging and detonation.

For the record, I am a retired Chrysler Engineering Manager (retired two years ago). I spent the last 30 of my 36 years in Powertrain. To be clear, I never had responsibililty for the actual combustion process (it stopped just short of the combustion chamber.)

I posed this issue this week to a fellow Powertrain retiree whose responsibilities at one time clearly included resolving ping/knock issues. (His pastime for the last four years was coordinating engine builds for a major NASCAR engine builder in North Carolina - some retirement gig, huh?). Here's what he had to say:

He defined ping as low-level detonation (couldn't define ping without using the word "detonation".) The root cause of the two is the same.

The knock sensor is set to pick up pre-audible detonation. If you are hearing ping while running the recommeded RON level and are not setting a MIL light, you have a system issue (likely faulty knock sensor) and need to get it addressed.

Pinging - if allowed to go on long enough - will result in enough cumulative damage to cause engine durability issues. I couldn't get an opinion of "how much for how long" - too many variables to give a specific answer.

2 1/2 years ago, my small lunch group at work included corporate combustion experts and engine calibration specialists. There would have been about 150 years cumulative experience on this..... Unfortunately, most of their discussions on subjects like this were over my head:o

[Paul Ryan]

OBD-I versus OBD-II is simply a difference in communications protocol (and available system information) and therefore has no difference on an ECU's tolerance to pinging. That said, the manufacturer may have set their tolerance higher on OBD-I vehicles, or the extra info on OBD-II equipped vehicles would allow them to run with more sensors, but it's not a direct correlation.


Dan,

Will all due respect there is a lot more involved between the 2 than just a communication protocol. OBD II was the 1st global communication protocol. But it also address emissions big time. This is when you start seeing upstream and down stream O2 sensors, EVAP systems, and as I explained earlier less tolerance to miss fires along with a whole slew of other changes to drivability.

[Dan Hintz]

Dan,

Will all due respect there is a lot more involved between the 2 than just a communication protocol. OBD II was the 1st global communication protocol. But it also address emissions big time. This is when you start seeing upstream and down stream O2 sensors, EVAP systems, and as I explained earlier less tolerance to miss fires along with a whole slew of other changes to drivability.
As I mentioned in parenthesis, it allows for a wider range of information per the spec, but in and of itself is nothing more than a comm protocol. It's up to the ECU to decide what to do with the extra sensor info, and as such, any reduction in tolerance to misfires is up to the ECU firmware, not the change from OBD-I to OBD-II. It's not a perfect analogy, but it's akin to RS-232 versus USB... they're both comm channels, but the higher speed of USB allows for more info in the same period of time... but I wouldn't say a system using USB is faster at calculations than one using RS-232, as that's the CPU's job, not the comm channel.

[Bob Turkovich]

Ok. At the risk of reopening this thread....

I had lunch today with 6 other Powertrain engineering managers - 5 retirees (max. retirement 3 years so relatively up-to-date) and two active. There were two hardware guys (myself included) - four engine calibration specialists (each with at least 20 years of calibration experience)- and one systems guy who used to run our California Emissions research facility. I used it as an opportunity to discuss this thread and here's what they had to say:

Pinging is low-level detonation. How low? ....could not get a consensus :confused: but detonation is a complete no-no.

Mixed reaction re: pinging causing engine durability issues. Depends how much pinging and for how long. Some manufacturers calibrate such that pinging is allowed under heavy throttle conditions. :eek: Therefore, you may get pinging and not necessarily have a bad knock sensor. Chrysler's philosophy is to calibrate to just below audible pinging - an astute customer may pick up an occasional ping under high loads (e.g., heavy throttle on grades.)

Is there any benefit running higher octane than recommended? I got a surprise answer here - Yes, but not just due to the additional octane. Higher octane fuels usually come with additional additives that do not affect the octane rating (which I did not know) but will clean/prevent the formation of carbon deposits. So,if you're running the recommended octane and getting pinging, using a higher octane fuel will help.

OBD vs. OBD II - the calibration guys stated the difference is just a communication protocol yet the other hardware guy and I remember having to replace stepper actuators with linear actuators (e.g., idle air control valves or EGR valves) soon after the time we converted to OBD II - at their insistence - as it gave the calibrators greater control over those features. (The linear EGR valve was a royal pain to develop...)

Paul, if your 96 Ram truck had a 4.7L engine, it may have not had a knock sensor.:eek: Trucks were the last to get them (and the 4.7L engine was the last to get it - around '96 but the two truck guys weren't sure.)

As you can see, just like the rest of this thread - not complete agreement - however, I thought you'd like to hear what we discussed. We meet once a month....if you have further questions, let me know.

[Dan Hintz]

Is there any benefit running higher octane than recommended? I got a surprise answer here - Yes, but not just due to the additional octane. Higher octane fuels usually come with additional additives that do not affect the octane rating (which I did not know) but will clean/prevent the formation of carbon deposits. So,if you're running the recommended octane and getting pinging, using a higher octane fuel will help.
Bob, I'll disagree slightly here, so feel free to pass my reason along to the guys and see what they say. While the higher octane gas will have more cleaners, it will not prevent pinging on a clean (i.e., new, or well taken care of) engine. If the pinging is caused by carbon deposit buildup, you would be better off spending $10 once for a deposit cleaning solution washed through the block than spending $2 extra with every fillup. If the pinging is not caused by carbon deposits, the extra cleaners in the high-octane fuel will do zero for the problem.

So, I agree with them as far as pinging being reduced with higher octane fuels (and the cleaners) on a dirty engine, but I feel the problem can be resolved more inexpensively with a designed-for solution (the cleaner).


OBD vs. OBD II - the calibration guys stated the difference is just a communication protocol yet the other hardware guy and I remember having to replace stepper actuators with linear actuators (e.g., idle air control valves or EGR valves) soon after the time we converted to OBD II - at their insistence - as it gave the calibrators greater control over those features. (The linear EGR valve was a royal pain to develop...)
Having to change out the motor type for the EGR valves is coincidence, if you will, to changing protocols. Moving from OBD-I to OBD-II is akin to changing from Fisher-Price preschool speak to high-school level discussions. The older people can understand the preschool stuff, but the preschool kids can only understand a portion of the high-school language... but both know how to tell others if they're hot or cold. It's up to others (i.e., hardware) to decide what to do with that information (e.g., open the heater core valve).

[Bob Turkovich]

Bob, I'll disagree slightly here, so feel free to pass my reason along to the guys and see what they say. While the higher octane gas will have more cleaners, it will not prevent pinging on a clean (i.e., new, or well taken care of) engine. If the pinging is caused by carbon deposit buildup, you would be better off spending $10 once for a deposit cleaning solution washed through the block than spending $2 extra with every fillup. If the pinging is not caused by carbon deposits, the extra cleaners in the high-octane fuel will do zero for the problem.

So, I agree with them as far as pinging being reduced with higher octane fuels (and the cleaners) on a dirty engine, but I feel the problem can be resolved more inexpensively with a designed-for solution (the cleaner).

Having to change out the motor type for the EGR valves is coincidence, if you will, to changing protocols. Moving from OBD-I to OBD-II is akin to changing from Fisher-Price preschool speak to high-school level discussions. The older people can understand the preschool stuff, but the preschool kids can only understand a portion of the high-school language... but both know how to tell others if they're hot or cold. It's up to others (i.e., hardware) to decide what to do with that information (e.g., open the heater core valve).

Dan,

Not so sure....if the manufacturers calibration is set up to allow some amount of pinging and you - as the customer - aren't happy with it - wouldn't running a higher octane raise the threshold for pinging?

Another thing - one needs to be careful with the additives. There is no way the companies pushing these things can do the amount of development work the auto companies do and guarantee their additives don't cause other issues (e.g., long term incompatibility with injector seals).

Unfortunately, the same thing can be said about the additives the oil companies put in their fuel as well. A few years ago, I had a major warranty issue that reared itself in cold temperature. Deposits were being formed that caused a control valve to stick. The issue was limited to the Great Lakes area and up and down the I-75 corridor (retirees going to Florida for the winter). Zero issues anywhere else in the country. Talked to the customers and they all bought their gas from one company....had to be the fuel.

Re: OBD. I'll defer to the experts here, (moving electrons is not my forte) but I'm convinced the calibarators used OBD II as an excuse for driving changes to some of the components. ("Higher sampling rates allowing for better control, etc., etc., etc."). Maybe there was a coincidental ECU change that I'm not remembering.

[Phil Thien]

Unfortunately, the same thing can be said about the additives the oil companies put in their fuel as well. A few years ago, I had a major warranty issue that reared itself in cold temperature. Deposits were being formed that caused a control valve to stick. The issue was limited to the Great Lakes area and up and down the I-75 corridor (retirees going to Florida for the winter). Zero issues anywhere else in the country. Talked to the customers and they all bought their gas from one company....had to be the fuel.


Funny you bring that up, because that was quite an ordeal in the Milwaukee area. Lots of people replacing fuel injectors.

I never had a problem, I was buying all my gas at Shell at the time.

Do you remember the gas company that had the additive problem? I'm not sure I ever found out.

[Dan Hintz]

Not so sure....if the manufacturers calibration is set up to allow some amount of pinging and you - as the customer - aren't happy with it - wouldn't running a higher octane raise the threshold for pinging?

Another thing - one needs to be careful with the additives. There is no way the companies pushing these things can do the amount of development work the auto companies do and guarantee their additives don't cause other issues (e.g., long term incompatibility with injector seals).

Unfortunately, the same thing can be said about the additives the oil companies put in their fuel as well. A few years ago, I had a major warranty issue that reared itself in cold temperature. Deposits were being formed that caused a control valve to stick. The issue was limited to the Great Lakes area and up and down the I-75 corridor (retirees going to Florida for the winter). Zero issues anywhere else in the country. Talked to the customers and they all bought their gas from one company....had to be the fuel.
Bob,

Don't get me wrong, I'm not necessarily pushing additives, I'm simply saying the direct cause of the pinging (deposits) should be resolved (by cleaning) rather than placing a band-aid on the problem (using higher octane gas). If there are no deposits (clean engine) and you're still pinging, the additives in the higher octane gas will do nothing for you... in that case, you need to determine what the real underlying issue is.

Re: OBD. I'll defer to the experts here, (moving electrons is not my forte) but I'm convinced the calibarators used OBD II as an excuse for driving changes to some of the components. ("Higher sampling rates allowing for better control, etc., etc., etc."). Maybe there was a coincidental ECU change that I'm not remembering.
You actually have it... OBD-II allows for more data (via both higher bandwidth as well as more sensor types). It's like the difference between taking a picture with a 100-pixel camera and a 1,000,000-pixel camera... you can do more with what you have. In your case, doing more meant being able to control the valve in a different manner.

[Dan Hintz]

I never had a problem, I was buying all my gas at Shell at the time.
About 6 (?) years ago Shell had a similar issue... too much sulfur in their gas. Screwed up a lot of catalytic converters, cost them a bundle to replace. I think even a single tank full was enough to toast them.

[Bob Turkovich]

Funny you bring that up, because that was quite an ordeal in the Milwaukee area. Lots of people replacing fuel injectors.

I never had a problem, I was buying all my gas at Shell at the time.

Do you remember the gas company that had the additive problem? I'm not sure I ever found out.


Bob,

You actually have it... OBD-II allows for more data (via both higher bandwidth as well as more sensor types). It's like the difference between taking a picture with a 100-pixel camera and a 1,000,000-pixel camera... you can do more with what you have. In your case, doing more meant being able to control the valve in a different manner.


About 6 (?) years ago Shell had a similar issue... too much sulfur in their gas. Screwed up a lot of catalytic converters, cost them a bundle to replace. I think even a single tank full was enough to toast them.

The issue we had was with a sticking idle air control valve. We found sulfate deposits on the valve seat seal causing the sticking. Computer modeling of the intake manifold for this application (the problem was vehicle-specific) showed we were getting back flow of EGR gas (after it entered the intake) into the control valve area. We figured there were only two ways we could get sulfates into that area - either it was being applied somewhere in the manufacturing process (e.g., as a lubricant) or as part of the combustion process. We traced the entire production process - from valve seal manufacturing through the production of the car - to see if some unauthorized lubricant was being used. Couldn't find anything. After we got enough data to show the issue was geographically specific we focused on the fuel. The combustion process does not normally create this particular sulfate (i.e., more sulphur did not cause the problem) but rather required a catalyst for the chemical process to take place. The additive - whatever it was - provided the catalyst.

I am reluctant to name the "oil company" (think "member discount") as they just get their gas from the regional distributor that they had a contract with at the time.

In the time that I had tenure over fuel injectors ('06 - '08) I remember only one injector issue. That one was in a low volume/high performance vehicle application and was not fuel specific. For such a complex component, the warranty on injectors was really quite low.

I liked your camera comparison, Dan. BTW - re: your discussion with Paul, the group didn't think knock sensor control logic/sensitivity changed w/ OBD II.

[Ken Fitzgerald]

It's amazing how far gasoline qualities have come in the last 20 years and how it's effected vehicle maintenance.

I bought a used Toyota 4-Runner with 19,000 miles on it, 22 RE engine and automatic transmission. About every 18-22 months the darn thing would develop a little miss noticeable only when stopped at stop sign. I'd take it to the dealer and a couple hundred dollars later after the fuel injectors were cleaned, it would be fine for another period of time.

I finally got fed up with taking to the dealer and talked with my SIL. Both he and my daughter have college degrees in automotive mechanics and he was certified in many different areas at the time. I asked him what a professional cleaning equipment would cost. His advice was to get 2 cans of a gasoline additive (brand specific) put it in the tank, fill the tank up and drive it until it was running on fumes and then start using that brand of gasoline. This happened around 1990-1991. I did as he suggested. I bought two bottles of that gasoline additive added them to the tank, filled the tank and the wife and I took the 4-Runner from Lewiston, ID to Missoula, MT to Cour dalene and back to Lewiston. I filled up when it was absolutely necessary. I started running that brand of gas and never cleaned another fuel injector on my personal cars or my company cars.

Now days...all the major brands of gasoline don't appear to foul fuel injectors.

[Paul Ryan]

Paul, if your 96 Ram truck had a 4.7L engine, it may have not had a knock sensor.:eek: Trucks were the last to get them (and the 4.7L engine was the last to get it - around '96 but the two truck guys weren't sure.)



Bob,

Ram pickups weren't offered with 4.7 litter engines until 2003. After spending 17 years working on chrysler vehicles I remember lots of changes through out the years. And how much easier diagnostics became once OBD II came around. Yes, OBD is just a communication protocol, but the change of communication protocol also signified a major change in drivability diagnostics and emission controls. The higher data speeds allowed the better diagnostics. For example a 95 ram truck did not come from the factory with knock sensors. There was no way to pick up miss fires unless you used a scope. In 1996 when OBD II became manditory from every manufacturer knock sensors appeared along with a host of other changes. Now instead of using a scope to determine the location of a missfire you could use the scan tool saving time. This is the biggest reason you hardly see any scopes in use any more. I still have a 1960 model sun scope in my shop collecting dust. In 2004 when CAN bus came to chrysler vehicles and became manditory to all automobiles built in the US in 2008 a whole a new chapter was written. Controler Area Network which is much higher speed than the original OBD II lead to drive by wire systems that so common today.

My truck is a perfect example of what your engineer friends were talking about when they suggested higher octane to take care of a a ping. The timing controlled by the PCM is so close that higher temps, and load will cause pinging to happen. Higher octane gas takes care of this. But when loads and temps are normal pining should not occur on any vehicle.

I am unsure what additive were used in fuels in MN the winter of 1999. But that winter fuel injector failures were very common. Most shops didn't have the pressurized cleaning systems that are used today. I was working at a Ford dealer at the time. But in a month we replaced more injectors then I have ever since due to something that was in the fuel. Once it warmed up and the additives were changed the fuel injectors working like normal. Since that winter widespread failures haven't been common either. The failures weren't isolated to Ford either it was every manufacturer. But Rochester injectors seems to be effected most frequently.