Lately I have noticed that My is creating alot of Detonation/ spark knock. I live in the south where it is hot. I normally use 89 octane gas, with the exception of 87 sometimes. I went to the Mountains in North Carolina. Filled up with 87 when I got to Tennessee, went to drive up a steep mountain, and all I heard was spark knock the whole way up. It was a little frightning as I could not or did not want to stress the engine too much, while other cars behind me seemed to form a long line because i was holding up traffic. I was wondering that even though the temp gauge does not even sit in the middle most of the time it always sits below the middle which is making me think that the engine is running cool? So why am I hearing the spark knock? Could it be the coolant?? I replaced the temp gauge for the car a year ago, I had water filled in the cooling system because I had a radiator hose to blow off for some unknown reason, and just before that, my heater core blew, and im thinking that both were related to the new radiator pressure cap I bought, So before anything else blew I just put the original radiator cap back on. I did drain the water out of the radiator, and filled the radiator with new coolant, but I didnt do a full flush of the engine, So im thinking that water may still be in the engine which is causing my issue here. I cant even accelerate heavy/ let alone floor it without that spark knock.

 

Maybe your ignition timing is advanced too much, you have excessive carbon build up in your combustion chamber(s), or you got bad gas.

 

I dont know maybe it was bad gas. I adjusted the ignition timing, and that helped a little also, then again I guess the heat index and high altitude can contribute to it also.

 

There's less chance of pinging at higher altitude than there is at lower altitude.

 

Hmm I guess I got bad gas then, then also I had alot of build up in my intake manifold too, but I cleaned it out while doing my injectors.

 

Lower octane gas can cause destination of the cylinders to happen as it takes more heat (spark) to ignite the air fuel mixture in the combustion chamber. Owners manual states only premium octane fuel be used in maximas.

 

I thought that was only for the SE VE30DE engines that premium fuel was recommended for. Others said it was a waste of money to put premium in a VG, But it should be for all Maximas. It seems I get better mileage on 89 than 87, but gas is a little high now.

 

I thought that was only for the SE VE30DE engines that premium fuel was recommended for. Others said it was a waste of money to put premium in a VG, But it should be for all Maximas. It seems I get better mileage on 89 than 87, but gas is a little high now.

 

Do you have even the vaguest idea what knock or detonation is? Do you realize what you just said there is plain nonsense? 505max94se summed it up 100% correct earlier - as I told you in that other screwed-up thread recently, octane rating has to do with the fuel's resistance to spontaneous combust under extreme pressures, and as 505max94se said already, at higher altitude the air is less dense, so your maximum cylinder pressures are lower than at a lower altitude so your onset of knock safety margin increases with altitude.

Please lets not screw up another thread because of your insistence on the right to post garbage

 

Lmfao seriously dude? Did you even go to school F
for automotive technology? If you want i can write what is said in the automotive technology text book i have from college. As i see it you love to just fight people on the forums. Destination occures from a spark lighting the a/f mixture in the cylinder other then from where it is suppose to happen which is the spark plug. In other words from friction in the cylinder whether from carbon that broke free or from the piston making friction against the cylinder wall. I'll post what the college technology book says once i get home from work.

 

WTF! This thread is full of fail...

 

Also, LvR is correct and and elusivemax93 is wrong lol

 

Lol LOL I still dont understand why elusivemax posted the same thing 5 times?????

 

You do that yes ....................

 

I didnt post five times. Im on my android phone and it does odd things at times. Now to clarify for morons of the forums. For those wanting to verify what im about to write out of the automotive technology book.

A systems approach 4th edition. By Jack Erjavec

Chapter 26 page 673 second paragraph

Normal combustion occurs gradually in each cylinder. The flame front advances smoothly across the combustion chamber until all the air/fuel mixture has been burned. Detonation occurs when the flame front fails to reach a pocket of mixture before the temperature in that area reaches the point of self-ignition. Normal burning at the start of the combustion cycle raises the temperature and pressure of everything inside the cylinder. The last part of the mixture is both heated and pressurized, and the combustion of those two factors can raise it to the point of self-ignition. At that moment, the remaining mixture burns almost instantaneously. The two flame fronts create a pressure wave between them that can destroy cylinder head gaskets, break piston rings, and burn pistons and exhaust valves. When detonation occurs, a hammering, pinging, or knocking sound is heard. However, when the engine is operating at high speed, these sounds cannot be heard because of the noise from the engine and road.

Fuel Performance

many of the performance characteristics of gasoline can be controlled in refining and blending. The major factors affecting fuel Performance are antiknock quality, volatility, sulfur content, and deposit control.

Antiknock Quality

An octane number or rating was developed by the petroleum industry so the antiknock quality of a gasoline could be rated. The octane number is a measure of the fuel's "TENDENCY NOT TO EXPERIENCE DETONATION IN THE ENGINE."
"The higher the octane rating, the less of a tendency the engine has to knock". By itself, the antiknock rating has nothing to do with fuel economy or engine efficiency.
Two methods are used for determining the octane number of gasoline : the motor octane number (MON) method and the research octane number (RON) method. Both use a laboratory single-cylinder engine equipped with a variable head and knock meter to measure knock intensity. A test sample of the fuel is used in the engine as the engines compression ratio and air/fuel mixture are adjusted to develop a specific knock intensity. There are two primary standard reference fuels : isooctane and heptane. Isooctane does not knock in an engine but is not used in gasoline because of its expense. Heptane knocks severely in an engine. Isooctane has an octane number of 100. Heptane has an octane number of zero.
A fuel of unknown octane value is run in a special test engine, and the severity of knock is measured. Various proportions of Isooctane and heptane are run in the engine to duplicate the severity of the engine knock when the test fuel was run. When the knock caused by the Isooctane/heptane mixture matches that caused by the fuel being tested, the octane number is established by the percentage of Isooctane in the mixture. For example, if 85% Isooctane and 15% heptane produced the same knock severity as the tested fuel, that fuel would be rated as having an octane rating of 85.


I rest my case.

 

okay.
now... I must be missing what contradicts what lvr said...
but i am tired, and going to bed.

 

Ben keep out of it. Unless your also one of the morons

 

You get 10/10 for effort
You get 10/10 for accurate reproduction
You get 10/10 for neat typing

You fail absolutely and miserably on relevance to your justification of your earlier brainfart expressed as "Lower octane gas can cause destination of the cylinders to happen as it takes more heat (spark) to ignite the air fuel mixture in the combustion chamber".

Arthur Wellesley said it best I think - "Publish and be damned" .................. and damned you are sir.

 

Lmfao ok fukktard it's azzholez like you that ruin what is suppose to be a forum put together to help others your stupidity doesn't help and you under trained knowledge of automotive shows how stupid you are. Ive learned from two well trained former master technicians of Honda Nissan ford and bmw. Both of them with a combined amount of years in the automotive industry of 35+ years. I went to college for automotive and what about yourself? Probably just a backyard mechanic who doesn't know the true technical side of the industry. Congratulations on showing me your stupidity and true nature of always being rude and mean to people coming to this forum. Not the ones trying to put 4" exhaust and turbo without any knowledge of automotive

 

Unlike everyone on here i don't flame burn or roast people for having an idea. Helpful criticism is one that points someone in the direction they are looking for. Not just bring them down every chance you can. Hence another reason i don't waste my time asking you all much. I call fellow college class mates questions or problems im having who like myself know what we do.

 

I absolutely agree - I am the fukktard and azzhole and unlike you I have never ever been able to justify what I said

 

Abnormal combustion

When unburned fuel/air mixture beyond the boundary of the flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur. Detonation is characterized by an instantaneous, explosive ignition of at least one pocket of fuel/air mixture outside of the flame front. A local shockwave is created around each pocket and the cylinder pressure may rise sharply beyond its design limits. If detonation is allowed to persist under extreme conditions or over many engine cycles, engine parts can be damaged or destroyed. The simplest deleterious effects are typically particle wear caused by moderate knocking, which may further ensue through the engine's oil system and cause wear on other parts before being trapped by the oil filter. Severe knocking can lead to catastrophic failure in the form of physical holes punched through the piston or head (i.e., rupture of the combustion chamber), either of which depressurizes the affected cylinder and introduces large metal fragments, fuel, and combustion products into the oil system. Hypereutectic pistons are known to break easily from such shock waves.
Detonation can be prevented by any or all of the following techniques: the use of a fuel with high octane rating, which increases the combustion temperature of the fuel and reduces the proclivity to detonate; enriching the fuel/air ratio, which adds extra fuel to the mixture and increases the cooling effect when the fuel vaporizes in the cylinder; reducing peak cylinder pressure by increasing the engine revolutions (e.g., shifting to a lower gear, there is also evidence that knock occurs more easily at low rpm than high regardless of other factors); increasing mixture turbulence or swirl by increasing engine revolutions or by increasing "squish" turbulence from the combustion chamber design; decreasing the manifold pressure by reducing the throttle opening; or reducing the load on the engine. Because pressure and temperature are strongly linked, knock can also be attenuated by controlling peak combustion chamber temperatures by compression ratio reduction, exhaust gas recirculation, appropriate calibration of the engine's ignition timing schedule, and careful design of the engine's combustion chambers and cooling system as well as controlling the initial air intake temperature. Knock is less common in cold climates. As an aftermarket solution, a water injection system can be employed to reduce combustion chamber peak temperatures and thus suppress detonation. Interestingly the addition of certain materials such as lead and thallium will suppress detonation extremely well when certain fuels are used. The addition of tetra-ethyl lead (TEL), a soluble salt added to gasoline was common until it was discontinued for reasons of toxic pollution. Lead dust added to the intake charge will also reduce knock with various hydrocarbon fuels. Manganese compounds are also used to reduce knock with petrol fuel. Steam (water vapor) will suppress knock even though no added cooling is supplied. Certain chemical changes must first occur for knock to happen, hence fuels with certain structures tend to knock easier than others. Branched chain paraffins tend to resist knock while straight chain paraffins knock easily. It has been theorized that lead, steam, and the like interfere with some of the various oxidative changes that occur during combustion and hence the reduction in knock. Turbulence as stated has a very important effect on knock. Engines with good turbulence tend to knock less than engines with poor turbulence. Turbulence occurs not only while the engine is inhaling but also when the mixture is compressed and burned. During compression/expansion "squish" turbulence is used to violently mix the air/fuel together as it is ignited and burned which reduces knock greatly by speeding up burning and cooling the unburnt mixture. One excellent example of this is all modern side valve or flathead engines. A considerable portion of the head space is made to come in close proximity of the piston crown, making for much turbulence near T.D.C. In the early days of side valve heads this was not done and a much lower compression ratio had to be used for any given fuel. Also such engines were sensitive to ignition advance and had less power.
Knocking is more or less unavoidable in diesel engines, where fuel is injected into highly compressed air towards the end of the compression stroke. There is a short lag between the fuel being injected and combustion starting. By this time there is already a quantity of fuel in the combustion chamber which will ignite first in areas of greater oxygen density prior to the combustion of the complete charge. This sudden increase in pressure and temperature causes the distinctive diesel 'knock' or 'clatter', some of which must be allowed for in the engine design. Careful design of the injector pump, fuel injector, combustion chamber, piston crown and cylinder head can reduce knocking greatly, and modern engines using electronic common rail injection have very low levels of knock. Engines using indirect injection generally have lower levels of knock than direct injection engine, due to the greater dispersal of oxygen in the combustion chamber and lower injection pressures providing a more complete mixing of fuel and air. Diesels actually don't suffer exactly the same "knock" as gas engines since the cause is known to be only the very fast rate of pressure rise, not unstable combustion. Diesel fuels are actually very prone to knock in gas engines but in the diesel there is no time for knock to occur as the fuel is only oxidized during the expansion cycle. In the gas engine the fuel is slowly oxidizing all the while it is being compressed before the spark. This allows for changes to occur in the structure/makeup of the molecules before the very critical period of high temp/pressure.
An unconventional engine that makes use of detonation to improve efficiency and decrease pollutants is the Bourke engine.

 

Ive retarded the timing a bit so far, But I may have gotten a half tank full of bad gas. I took about a 300 mile round trip to tennessee to the Mountains, and places Ive never been! It was a great trip, and the MAX was holding the road, even through all the curvy mountain roads and hills. Just when I got off I-40 to refill, I got the cheapest gas. She started knocking so badly as I was trying to enter the interstate, I had to ease off the pedal. But going bak home was a breeze, once I got out of the mountains, and at an average cruise speed of 75-85mph I was bak home in no time.

 

Glad the obvious answer was the correct answer then.

 

Run some 93 octane and see what happens......