[OffRoadFun]

Nice summary and very informative.

On a lighter note, what about this myth?

Does petrol catch fire if one shoots a bullet in the fuel tank as shown commonly in movies :-) ?

Me thinks NOT.
https://www.quora.com/If-you-shoot-a...wer%20%3A%20NO.

Originally Posted by Zippy_wheels

Can you please break it down for us whether its okay to use 91 regularly in normal city and occasion highway driving conditions?

Is the only difference power and mileage or can it cause more engine wear and tear/damage?

Thanks!

It is absolutely OK to use 91 rating not just once in a while but always, the ECU will change ignition timing accordingly with no damage to the engine.

It's just that this engine has been designed to deliver mentioned peak power using that octane rating. In real life, on drag strip or when you floor the paddle your power/acceleration may not reach the peak value mentioned, again, without damaging the engine or any part of the vehicle. But you will be off the peak power/acceleration by may be by 5% or so in worst case and for all practical purposes never even feel in real life driving conditions.

Using a fuel with rating significantly below 91 regularly may cause damage though.

[Sen]

Originally Posted by Zippy_wheels

So I have a fairly simple question.

Same engine, thanks for asking this question.

Personally speaking, I use 95 Octane (XP95) for only one reason - I personally love the change in characteristics that the fuel brings to the engine. It makes it peppier and more rev-happy comparatively. This entire thread is excellent and well worth a read.

If you fill 91 RON fuel (the standard in India, and this is from the refineries directly to the bunks, no matter which bunk you fill from) IIRC, your car's ECU will happily tweak the settings accordingly and ensure that the engine will run for the usual lifespan (with regular maintenance as is expected of course) with no issues. I switched to XP95 fully after about a year into owning Taco, and the difference is worth it for me personally with my heavy right foot!

If you want to save cash wherever possible, 91 RON fuel will do. And do well. Don't sweat the details or worry about engine damage or anything.

[vjvinamara]

Originally Posted by NomadSK

1:Some Myths which comes to my mind and needs to be busted;

1: Premium gas is better for your car.
It’s true that premium is the better gas in terms of octane levels, but that doesn’t mean it’s better for your car. Higher-octane fuel is designed for high performance vehicles with high compression ratio. Your owner’s manual will tell you if it’s required for your car.

Thank you, that was much needed clarification. At some fuel outlets I've personally seen Pump attendants push for the higher octane or "Premium fuel" citing reasons such as better performance and mileage to even 150-200 cc bike owners. I guess better margins are the rationale behind this.

[shankar.balan]

Originally Posted by Zippy_wheels

So I have a fairly simple question. The manual of my car (1.0 TSI) says use 95 octane and in emergency it is okay to use 91 (slight power loss and lower fuel efficiency) Attached is the part of the manual that describes this. Can you please break it down for us whether its okay to use 91 regularly in normal city and occasion highway driving conditions?

Is the only difference power and mileage or can it cause more engine wear and tear/damage?

Thanks!

What car is this please?

[thanixravindran]

Originally Posted by Sen

Same engine, thanks for asking this question.

Personally speaking, I use 95 Octane (XP95) for only one reason - I personally love the change in characteristics that the fuel brings to the engine. It makes it peppier and more rev-happy comparatively. This entire thread is excellent and well worth a read.

If you fill 91 RON fuel (the standard in India, and this is from the refineries directly to the bunks, no matter which bunk you fill from) IIRC, your car's ECU will happily tweak the settings accordingly and ensure that the engine will run for the usual lifespan (with regular maintenance as is expected of course) with no issues. I switched to XP95 fully after about a year into owning Taco, and the difference is worth it for me personally with my heavy right foot!

If you want to save cash wherever possible, 91 RON fuel will do. And do well. Don't sweat the details or worry about engine damage or anything.

I guess you are all referring to the India 2.0 cars of VW and Skoda 1.0 TSI engine. I have Kushaq 1.0 and was using 91 RON for more than a year and this is my pet peeve against them. If most of the target market for your mass market car is using 91 RON, why a heavily localised design should be specified to 95 RON is a puzzle. But I got some answers from this beautiful thread.

The simple reason I didn't used XP95 though widely available is I had bad experiences with IOCL in the past and don't prefer them. I was always worried whether regularl 91 RON will lead to reduced reliability of 1.0 engine in longer run.

After the launch of HP Power 95, I have switched to it for few months now and can clearly observe the engine note feels refined. I don't know whether it is placebo effect but I am happy to stick to Power 95 where possible.

[NomadSK]

Originally Posted by careind

Is it just really just ONLY a marketing ploy by the oil companies to sell high octane/cetane fuels and the average normal customer does not benefit in anyways?

I , like so many of us, was attracted to the below by IOC that says about its XtraGreen
https://iocl.com/pages/XtraGreen

Your valuable thoughts?

That's totally a marketing Gimmick. As we move ahead with environmental regulation, it is mandatory for the fuel to have lower sulfur Ppm's. And If you see the corelation between sulfur content and Cetane number, you will observe, higher cetane has lower sulfur content. Hence there's an improvement in the tailpipe emission, because of lower sulfur content and not the other way round.

This statement from IOCL;
"Third -party testing agencies have also reported a nearly 6% increase in fuel economy. A new age eco-friendly fuel, XtraGreen has been critical to driving the Nation with sustainable and eco-friendly energy solutions"
is good enough to make an educated inference.

With standard gasoline cars, it generally does not benefit the engine if the driver fills it with a gasoline that features an octane rating more than the amount recommended by the manufacturer. Similarly, vehicles that run on diesel do not perform any better by using fuel with a cetane number higher than the recommended amount for that specific engine, instead it might hamper with exhaust system.

Originally Posted by Sam800

I have couple of noob questions.

1. If dirty air filter doesn't affects the mileage in newer cars, wont the mileage drop if one presses pedal to metal to overcome the sluggish acceleration due to clogged filter?
Pressing the accelerator harder will obviously draw more fuel to the engine. I understand the engine won't pump more fuel by itself but the driver will push the pedal harder to overcome the sluggishness. And i think older carb car will be affected the same. Correct me if i am wrong, sir.

2. I understand carb engines had mechanical fuel pump which was operated by crankshaft and new ECU engines have electrical fuel pumps. The carb fuel filter used to be small netted cylinder and modern fuel filters are much better. But often in restoration posts we have read the fuel lines and pump got clogged due to rust and debris in fuel tank. Now these vehicles are mainly carb ones.

So in such cases, does the fuel filter can't perform its job or it is simply too small for debris or the lines get clogged before reaching the filter??

For;

1) There is a study specifically done for this, I have attached the picture of the conclusion. If you want the full technical report, let me know.

2) Jeroen have answered you on this.

Originally Posted by Kkumar

A wonderful article that can also be titled “MYTH BUSTER”. It has cleared a lot of misconceptions when it comes to fuel. Nice to see such well researched and lucid article. It is also one of the reasons why I joined this forum.

Thanks for your kind words. Knowledge is power.

Originally Posted by norhog

What is the OCTANE numbers of gaseous fuels.
LPG which is Buthane and Propane at various mixing levels.
CNG which is Methane with some impurities.

This is very easy peasy, just google it. Will throw the answers.

The octane number scale covers the range from 0 to 120 octane number, but test method has a working range from 40 to 120 octane number. Typical commercial fuels produced for automotive spark-ignition engines rate in the 80 to 90 Motor octane number range. Typical commercial fuels produced for aviation spark-ignition engines rate in the 98 to 102.

Originally Posted by dj96

Thank you for such an extensive write up. I just wanted to ask a few questions.

1. How does methanol injection come into play in all of this? I saw Jay leno's 600 grosser video where he mentions that he has added methanol injection as california gasoline comparatively low octane.

2. Please recommend some suitable octane boosters which one can carry as in India, high octane fuel is not readily available.

1) Methanol has high octane value (remember it's with respect to a scale of 100), like ethanol, it will increase the octane number of the fuel, meaning can sustain high compression. The high octane of methanol provides a convenient and cost effective way to upgrade low octane gasoline components. Its all about mixing and chemistry.

2) That's the myth I really want to debunk. Rather than filling in Octane boosters, fill the gas with higher octane value.

Originally Posted by Zippy_wheels

So I have a fairly simple question. The manual of my car (1.0 TSI) says use 95 octane and in emergency it is okay to use 91 (slight power loss and lower fuel efficiency) Attached is the part of the manual that describes this. Can you please break it down for us whether its okay to use 91 regularly in normal city and occasion highway driving conditions?

Is the only difference power and mileage or can it cause more engine wear and tear/damage?

Thanks!

As others have mentioned you are good to go as long as you are above 91 ON (not for extended period). But the screenshot you have shared, is mentioning, 2 octane numbers, which generally I haven't seen in the manuals. Hence, I would go with 95 ON.

Originally Posted by Silver Knight

Not correct, the nozzles are similar in most cases. You can even interchange the nozzles. At some very high-volume outlets where many trucks fill the nozzle size of diesel dispensers is slightly big.

As per the regulations, the diameter of the nozzles for Diesel and Petrol dispensing are different, which has been ammended lately, with color coding of the Nozzle. So probably you are correct on this.

Originally Posted by Sai Teja

I can somewhat comprehend the variability of RON due to altitude, humidity and air temperature, however the other factors like spark advance, coolant temperature and combustion chamber deposits make me think whether it's really the fuels ability to resist detonation or there is some part of the engine architecture that is making the fuel to hold up longer from detonation. Am I missing any part of the puzzle here? may be someone could help me clarify this.

You are right on this, engine also plays a role. Science is evolving on daily basis. One more pointer, Exposure to fuels to UV wavelengths shorter than 550 nm for a short period of time may significantly affect octane number ratings.

Originally Posted by OffRoadFun

Nice summary and very informative.

On a lighter note, what about this myth?

Does petrol catch fire if one shoots a bullet in the fuel tank as shown commonly in movies :-) ?

Me thinks NOT.

I missed to put up this MYTH, yes you are absolutely right this will not burn/explode the tank. Let me explain and debunk this,

For a fuel to burn, it has to be in the explosive range, Between LEL and UEL. Lower/Upper explosive limits. Below LEL, fuel/air mixture is too "lean" to burn. Above UEL, fuel/air mixture is too "rich" to burn. Gasoline range is 1.2% to 7.1%. Hence gasoline percentage in air has to be in this range to burn. Surely this range will depend on temperature and pressure. Gasoline, in its natural liquid state, is not flammable. In vapor state, however, it is highly volatile and this vapour needs a spark for explosion. That's why painting in an confined space is an extremely hazardous/critical activity, it gives off enough vapour for explosion to happen. Be super careful, when your cars are painted in a confined environment, specially when I see non approved, electrical lighting, heck, even a static discharge is enough for the explosion.

In a gasoline fire, it is the vapors that burn, causing the fire to appear to "rest" on top of the pool of gasoline (gasoline vaporizes readily at room or typical ambient temperatures.) Firefighters suppress such fires by applying water containing an agent that spreads as a film across the surface, like a foam. This film stops the gasoline from vaporizing and creating a barrier, cutting off the fuel supply to burn off.

So, an environment where a tank is shot at, is too "rich" a mixture for the gasoline to burn. That's why in our "Oil and Gas" terminology we say, full gasoline tank is in safer condition than partially filled. Even throwing a lit cigarette in the gasoline wouldn’t explode if there aren’t sufficient vapors to catch fire. Makes sense, or did I confuse you.

Originally Posted by vjvinamara

Thank you, that was much needed clarification. At some fuel outlets I've personally seen Pump attendants push for the higher octane or "Premium fuel" citing reasons such as better performance and mileage

Thanks for your kind words. Don't fall for that trap. Learning is always an Upward curve.

Cheers

[Jeroen]

Originally Posted by Sam800

Okay, understood. Does the fuel pump in fuel injected engine pumps the fuel at constant pressure all the times or the pressure is regulated as per demands from the engine? I understand the fuel is supplied to the cylinders through the nozzles but what about the pressure from fuel pump?

Yes, the actual pressure depends on many factors. But the pressure is kept fairly constant by means of some sort of pressure regulator. The pressure inside the feedline to the injector determines needs to well controlled and kept between a pretty narrow band width. Too large variation will likely cause problem for the injection/combustion.

Originally Posted by Sam800

Oh dear, thats terrible. What can be done so that neither petrol turns sticky, nor the tank gets rusty? Are there any additives for the petrol which can be added to it to prevent jelly-fying?

There are all kinds of additives. But their effectiveness is debatable. If anything they just prolong the petrol going bad, never really stop it.

Best thing is to maintain the fuel system properly, make sure you get high quality petrol. If you need to put your car away for a long time, fill the tank to capacity.

Originally Posted by Zippy_wheels

So I have a fairly simple question. The manual of my car (1.0 TSI) says use 95 octane and in emergency it is okay to use 91 (slight power loss and lower fuel efficiency) Attached is the part of the manual that describes this. Can you please break it down for us whether its okay to use 91 regularly in normal city and occasion highway driving conditions?

Is the only difference power and mileage or can it cause more engine wear and tear/damage?

Always follow the manual!! I will do a more detailed write-up below

Originally Posted by OffRoadFun

It is absolutely OK to use 91 rating not just once in a while but always, the ECU will change ignition timing accordingly with no damage to the engine.

Please enlighten us to what your qualifications and experience are? Apperently, you know better than the car/engine manufacturer who states very clearly you should not use octane 91 for any prolonged use!

Jeroen

[Kkumar]

Originally Posted by Jeroen

One of the problems with classic cars is they stand idle for months sometimes years. All fuel will go off over time. Normal petrol will turn into an almost jelly type of stuff, very sticky. It has happened to me once when my Alfa Spider was in storage for more than a year. We had to take the complete fuel system apart.

Jereon

Hi, normally heavy machineries, aircrafts, military equipments etc are mothballed and then kept in storage. Is there any similar options available for cars; if yes, then how to go about it.

[Jeroen]

In addition to NomadSK excellent write-up on this topic, I thought I would add a bit more detail on some of the other aspects relating to this topic. Some members have already mentioned ignition advance, engine knock in relation to the octane number of a fuel

Let's first look at some basic terminology. Three terms come into play, knock, detonation and pre-ignition.

I am borrowing various bits of text and images from the internet.

People often describe the process of petrol being ignited inside the cylinders of a regular petrol engine (technically an Otto cycle) as being akin to an explosion. Something that happens instantaneously. It is not! The air-fuel mixture does not explode when ignited by the spark plug. It burns evenly across the combustion chamber, starting from the spark plug. It is fast, but it is not an explosion, it needs to be very well controlled. Depending on the engine it takes anywhere from 60-90 degrees of crankshaft rotation. If you factor in typical engine RPM you can calculate the ignition time. (3-8 mili seconds or thereabout)

As the mixture starts to ignite the pressure inside the cylinder increases rapidly. The timing needs to be so that the peak pressure occurs well past TDC (Top Dead Centre). If the piston/crankshaft can only produce torque/power during its expansion stroke, so past the TDC.



Here you see a graph depicting the pressure inside the cylinder versus crank angle degrees.



If the combustion process moves too fast and the pressure peak occurs too early, the result can be excessive pressure, excessive temperatures, and unstable pressure pulses known as “detonation.” That’s because when the piston is near TDC, it can’t move downward in the cylinder to relieve the pressure (and accomplish some useful work in the process).

Detonation or knock are (generally speaking) the same.



Contrary to popular belief engine knock is not always a bad thing. Most engines do run in a "knocking regime" a bit now and then. So engine knock is not always a problem. It comes down to how much knocking an engine was designed to handle. The rule of thumb is that an NA engine can handle more knock than a turbocharged engine.

This detonation, or knock can be audible. Your engine knock sensor is just a microphone tuned into specific frequencies. When it detects (too much) knock the motor management system will adjust the ignition (sometimes also the injection timing). It shifts the peak of the curve towards the right.

There is also a phenomenon known as pre-ignition. Which is very different from detonation/knock. Pre-ignition is the ignition of the air-fuel mixture before the spark plug firing. Anytime something causes the mixture in the chamber to ignite before the spark plugs fire, it is classified as pre-ignition. The ignition source can be an overheated spark plug tip, carbon or lead deposits in the combustion chamber, or (rarely) a burned exhaust valve of these things can act as a glow plug to ignite the charge prematurely.

Such a hot spot in the chamber can ignite the charge while the piston is very early in the compression stroke. The result: For a significant portion of the entire compression stroke, the engine is trying to compress a hot mass of expanding gas. This puts tremendous mechanical stress on the engine and transfers a great deal of heat into the aluminium piston crown and cylinder head. Substantial damage is almost inevitable.

As you can imagine pre-ignition is more likely to occur on older engine that has not been looked after well enough.

Pre-ignition is almost impossible to detect in an otherwise well-running engine. It does manifest itself quite spectacularly though, and usually ends with a catastrophic failure of the engine or at least some parts.

This is what a piston looks like after some pre-ignition.



Pre-ignition damage is often mistaken for detonation/knock damage. But detonation and knock has the most profound effect on the rod bearings of your engine. They are getting a pounding they were not designed for.

Although pre-ignition is a stand-alone phenomenon, heavy detonation can also induce pre-ignition. So you get the worst of both!

The Octane number of your fuel determines to a large extent how effectively the combustion process can be run. Your engine management system, within a certain bandwidth, can adjust parameters such as ignition timing and fuel injection. But it is only within a certain bandwidth. As I have mentioned a billion times the most relevant parameter in all of this is compression ratio. And on our engines that is fixed. And ignition adjustment can only compensate for that much.

The engine knock manifests itself as cumulative wear on various engine components. that is why you see in some owner manuals the recommendation to use low-octane fuel only in case of emergency, for short durations and not to load your engine too much. Never trust people who tell you the owner's manual is wrong. Unless they are willing to foot the repair bill!

Anorak fact: Pilots learn quite a bit on detonation/knock/pre-ignition and such. The reason is that on a single engine reciprocating engine, pilots have separate controls for the fuel amount, mixture and engine RPM. You can't hear r knock in a plane, there is too much noise. So you need to be able to adjust fuel, mixture and RPM based on other engine parameters, such as exhaust temperatures.

I found this YT video which I thought was a very good explanation of all of what we have been discussing on this thread.

https://youtu.be/G5bJlFHKOX0?si=L1jms86_UHez8kjV

Jeroen

[Jeroen]

Originally Posted by Kkumar

Hi, normally heavy machineries, aircrafts, military equipments etc are mothballed and then kept in storage. Is there any similar options available for cars; if yes, then how to go about it.

Mothballing equipment is quite a science these days. Be it a marine engine or a plane. In all cases, all fuel will be removed. Very often all fluids. (oil, cooling fluids, transmission fluids) are likely to be drained. They will apply special conservation techniques to all surfaces.

It is way too complex and expensive for our cars. When I lived abroad my cars were kept in storage. They only ran every 12-18 months. I never did anything special as preparation apart from two things. Inflate the tires to about 1,25 -1,50 times normal pressure and fill the fuel tank to capacity.

In all those years I only experienced the fuel going bad once!

Jeroen

[OffRoadFun]

Originally Posted by Jeroen

Please enlighten us to what your qualifications and experience are? Apperently, you know better than the car/engine manufacturer who states very clearly you should not use octane 91 for any prolonged use!

Jeroen

I have mentioned the reason why I believe lower octane rating poses no threat and believe my qualification/experience is irrelevant to this discussion.

Again, modern cars have been having knock sensors for decades now to adjust the timing and for a 1.0 TSI engine 95 --> 91 RON should not make any meaningful difference under the conditions. VW/Skoda know this and have been selling 1.0 TSI engines in India for years with no complains/damage to the engine.


In fact, the ECU has no idea about the octane rating of the fuel, it calculates it based on closed loop readings. Car and Driver did an experiment on putting lower rated fuel on various cars including a BMW M5 and no, it does not damage the engine but just reduces the peak power (and 0-100 times by few tenths of the second).



https://www.caranddriver.com/feature...dodge-charger/

Here is excerpt from the article:

Your car doesn't know the octane rating of the fuel in its tank. Instead, the engine controller calculates an inferred octane with closed-loop logic that continuously advances the ignition timing until it detects knock, which occurs when a portion of the fuel-air mixture ignites before the spark-plug-initiated flame front reaches it. The further the computer can advance the timing without provoking knock, the higher the octane rating.

During knock, the flame front travels through the combustion chamber up to 10 times quicker than the normal spark-initiated flame front. Left unchecked, these pressure waves can damage the head gasket, pistons, or cylinder head. But the occasional brief knock is a useful tool for checking that the engine is operating efficiently. It's detected with one or more knock sensors bolted to the block to sense the oscillations created by the pressure waves with a typical frequency between 7 and 16 kilohertz. Stephen Russ, senior technical leader for gas engines at Ford, says this normal knock is usually detected and addressed within one or two combustion cycles and poses no threat to the engine. —ET

For a car designed to run on RON 100+ if one puts RON 91 or lower, yes, it can lead to damage as there would be limit to what can be done using ignition timing change. For 1.0TSI, RON 95 --> RON 91 would not matter much in all likelihood. While adhering to manual is always desirable, such margins would be built into.


Check out in the comments section, people have been running even Porsches with lower rated octane with no damage.

[Jeroen]

Originally Posted by OffRoadFun

I have mentioned the reason why I believe a lower octane rating poses no threat and believe my qualifications/experience are irrelevant to this discussion.

While adhering to the manual is always desirable, such margins would be built into it.

You have answered my question, you think you know better than the manufacturer, based on some internet articles.

The internet is awash with all sorts of fuel tests.

When it comes to finding the effects of knocking the article you refer to is amateurs at work at best. Yes, a bit of engine knock is not a problem at all, if you read my previous post I already said so. But persistent engine knock can cause serious damage to your car. The 200 miles they did in this test is of course way too little. And they did not open up the engine before and after either. So drawing any conclusion as far as effects of knock this test is completely insufficient

Engine knock, as I mentioned has a cumulative effect on several parts. Things don't break immediately (they might and often do in case of detonation).

Also, contrary to popular (internet?) wisdom you can't always hear an engine knock.

Please note the article refers to the US way of classifying Octane numbers. And as I mentioned before they are lower numbers than what most of the world uses.

Roughly speaking the US 91/93 is comparable to what all of us call 95/98. So none of the testing was done on an Octane 91 as we call it! The "87" that is referred to is sort of similar to our 91!

Please consider this when you read these articles and draw and extract your interpretations towards internet advice!

What the article does highlight is you might get some benefits of using a high octane number. But it depends on the engine. Some engines might benefit, and some won't.

Same with low Octane numbers, some engines can handle it, some not. In case of the latter, you will see a warning in the Owners handbook.

People keep hammering on about advancing the ignition timing. But the ignition timing can only do so much. Of course, the lower the octane number the ignition is not advanced, but retarded compared to normal.

[OffRoadFun]

Originally Posted by Jeroen

When it comes to finding the effects of knocking the article you refer to is amateurs at work at best.

I thought C&D people made a living out of analyzing autos. The Ford guy for sure.

Originally Posted by Jeroen

Yes, a bit of engine knock is not a problem at all, if you read my previous post I already said so. But persistent engine knock can cause serious damage to your car. The 200 miles they did in this test is of course way too little.

Engine knock, as I mentioned has a cumulative effect on several parts. Things don't break immediately (they might and often do in case of detonation).

Any knock, for any reasonable amount of time, as the Ford guy mentioned also, is read by ECU and ignition timing is adjusted accordingly to fix it. If it can't be fixed by adjusting ignition timing, depending on the car, a knock sensor error and/or a Power Control Module Error will kick-in no time. And that does not need to show up after first 1000 miles. If a talented auto engineer from Stuggart or Bavaria can design an engine which can tolerate only a narrow band of octane rating, he/she should be able to incorporate a safe mode. If knocking can not be fixed by the ECU, a limp mode or a lower power mode would be activated by Power Control Unit to avoid damage to the engine(as these knocks are more probable at higher power points).

Almost all modern cars are equipped with these modes to avoid damage to the engine/transmission.

I once installed a chip tuner with plays with MAF readings to increase boost in my Audi. The Power Control Unit immediately activated(and reduced power) sensing fishy readings from the sensor to protect the engine.

https://www.team-bhp.com/forum/modif...uning-box.html (Audi Q5: Why I picked an ECU remap over a tuning box)

Originally Posted by Jeroen

Also, contrary to popular (internet?) wisdom you can't always hear an engine knock.

I would think a mention of knock sensor on this forum would automatically imply sensor reading fed to ECU, after all the cars are very well (sound) insulated these days.
>> It's detected with one or more knock sensors bolted to the block to sense the oscillations created by the pressure waves

Now one should not drive the car if errors regarding engine are seen. One may not hear "knocking" owing to lower octane rating, it is unlikely one would not "see' the knocking related error from the ECU. If an error is not seen, the engine in all likelihood able to work with the octane rating of the fuel.

Nice illustrations and video depicting ICE BTW, must have been prepared using a good software for graphics I would think.

[Jeroen]

Originally Posted by OffRoadFun

I thought C&D people made a living out of analyzing autos. The Ford guy for sure.

No, C&D people make a living by producing a magazine that needs to make a profit. Apart from the required knowledge, running proper test programs is way beyond the means of any magazine. I have done some R&D engineering work on various engines. I was in charge of designing and running several programs to determine what factors contribute to engine wear. We ran our engines between 5-7500 hours. We took them apart before the test and we took them apart after the test program, so we had meaningful measurements. We always ran identical engines in parallel to further validate readings and measurements. All these engines were hooked up to data loggers recording dozens of engine parameters during all of the testing. We ran laboratory tests as well as tests in a real-world environment

These programs were co-designed by well-known, independent, scientific institutions who were considered to be leaders in engine design and testing.

The closest any car magazine used to come was the German Auto Week. Not sure if they still do, but they used to take cars apart after so many years/kilometre and inspect all parts. Those were interesting articles!

But you can imagine that proper (scientific) engineering testing is way beyond the means of any car magazine.

Originally Posted by OffRoadFun

Any knock, for any reasonable amount of time, as the Ford guy mentioned also, is read by ECU and ignition timing is adjusted accordingly to fix it. If it can't be fixed by adjusting ignition timing, depending on the car, a knock sensor error and/or a Power Control Module Error will kick in no time. And that does not need to show up after the first 1000 miles. If a talented auto engineer from Stuggart or Bavaria can design an engine which can tolerate only a narrow band of octane rating, he/she should be able to incorporate a safe mode. If knocking can not be fixed by the ECU, a limp mode or a lower power mode would be activated by Power Control Unit to avoid damage to the engine(as these knocks are more probable at higher power points).

It appears you still do not get my point. What the Ford guy is referring to is knock condition that occur normally. Whilst using the normal rated octane fuel. All engines will knock most likely. Especially under high load, and low RPMs.

I am referring to engine knock which occurs more often due to using a too low octane rated fuel. For some engines, RON 91 will be insufficient and will lead to engine damage in the long run.

Your knock sensor and ECU are not suited to pick up such a problem. Because you need to be able to correlate engine knock, frequency, engine RPM and a few other parameters and time to wear.

Originally Posted by OffRoadFun

Almost all modern cars are equipped with these modes to avoid damage to the engine/transmission.

I doubt it, not from what I read in manuals! You are likely to see limp modes in higher-end cars. But many cars, especially those with manual transmission don't have limp home modes.

When it comes to knock, I know of very few cases where limp mode would get triggered due to engine knock. In all cases, I have seen, a bad or not properly working knock sensor will trigger a limp home mode

Originally Posted by OffRoadFun

Now one should not drive the car if errors regarding the engine are seen.

Agree, although it does depend on what error you are getting. Again, your owner's manual will clarify whether you can drive on and get it sorted later, or stop the engine immediately.

Originally Posted by OffRoadFun

One may not hear "knocking" owing to lower octane rating, it is unlikely one would not "see' the knocking-related error from the ECU. If an error is not seen, the engine in all likelihood able to work with the octane rating of the fuel.

Disagree, and that is the reason why there is a warning in the owner manual!!

And not to put too fine a point on it: The guys from C&D adhered to the manufacturer's recommendation as well. They did not run any tests at lower Octane rating than recommended! So you might ignore the manual, They did not and I don't think the Ford guy would advise you to ignore the manual.



Again, it is my same argument over and over again. Any engine will have a minimum Octane rating. If you go below it, you are likely to cause engine damage in the medium to long run. Control systems, knock sensors and ECU are not designed to cater for problems caused by ignorance. On American cars when you read your manual, you are likely to find a clause that voids your warranty if using too low Octane fuel. Whereas most cars can handle RON91, some can't. The USA (and Canada I believe) still have places where they sell so-called High Altitude fuel which is rated according to the US system as 85 (So about RON 88-89)

It's a bit of a carry-over from the olden (carburettor) days and is perfectly legal to be sold. But it can play havoc with your engine!

Originally Posted by OffRoadFun

Nice illustrations and video depicting ICE BTW, must have been prepared using a good software for graphics I would think.

Thanks, I just copy-paste from either my documentation or from the Internet. I am the worst PowerPoint maker in the world. I might be able to make a bullet list, but even that is often beyond my capabilities.

I think we have said enough and repeated our points of view often enough. Let's leave it at that.

Jeroen

[Sam800]

Thank you everyone for their inputs. They have been very valuable for this forum. The level of deep knowledge and minute details surprise me to no end.

This image shows the size difference of petrol and diesel nozzle. Right two nozzles are of diesel but only one nozzle is thick one. They had to replace the other one.

Picture source- my phone.




Any pointers why there is electrical resistance mentioned for fuel tanks?