Detonation (aka Knock) - Destroyer of Engines, Dreams, and Bank Accounts

What is Detonation?

Detonation is when the air : fuel mixture burns at an extremely fast rate due to combustion chamber conditions resulting in a sharp rise in cylinder pressure and temperature. Detonation can vary in intensity from light, moderate, to severe depending on several factors.

Here’s a more technical definition: Detonation occurs after an ignition source, either pre-ignition or the spark plug firing, creates a primary flame front who’s acoustic shock wave and thermal gradient kick off auto-ignition in the end-gas (remaining unburnt mixture). This auto-ignition energizes the shock wave further resulting in an exponentially accelerating burn rate. The rate of the primary burn and propagation of the detonation is relative to the homogeneity of the mixture and the sensitivity of the fuel.

Terminology Used in this Article

Flame Front – This is the edge of the burning mixture. The spark plug fires and the flame radiates outward towards the walls of the cylinder. The leading edge is the flame front.

Consumed Mixture – This is the spent, consumed, burnt air:fuel mixture.

Hot Spot – This is a region of the mixture that is more volatile and nearest to auto-ignition. It can be due to a heated part of the piston or valve, or lesser octane due to fuel quality or oil vapor, or perhaps even both.

Homogeneity – In a perfect world the fuel and air molecules would be evenly distributed in a nice symmetrical pattern throughout the combustion chamber and kept at the same pressure and temperature. This would be a homogeneous mixture. The measure of how close the mixture is to this ideal situation is known as homogeneity.

TDC / BDC – Top dead center and bottom dead center. These both relate to the position of the piston in the cylinder. See the below image for more clarity.

TDC vs BDC

How Does Detonation Happen?

Compression Stroke

The start of the detonation cycle begins with a non-detonation firing event. The spark plug creates a spark at the moment the ECU signals, or the mechanical distributor causes, the ignition to fire. This moment occurs at a calculated or mechanically set point when the piston is still compressing the air : fuel mixture (on the upward stroke).

Combustion

The spark plug will fire anywhere from 40° to 5° before the piston reaches Top Dead Center, TDC. Since this even is before the piston reaches the top of it’s compression stroke, it’s more specifically known as BTDC (Before TDC).

The spark kernal ignites the air : fuel mixture and thus begins the combustion event. The ignition creates the flame front which propagates at a nominal rate outwards. This ideally burns the entirety of the mixture and creates a rapid, but controlled, increase in chamber pressure as the piston is on it’s downward power stroke. This occurs between the ignition moment and about 30° ATDC (After TDC). Ideally, you want peak cylinder pressure to occur between 14 – 18° ATDC to maximize the mechanical leverage of the rod and crank positions.

Exhaust Stroke (Groundwork for Detonation Event)

Prior to the piston reaching the bottom of it’s stroke, bottom dead center (BDC), the exhaust valves will begin to open. The residual pressure in the chamber is high which creates a strong blow-down in the exhaust once the valves reach significant lift (0.050″ or 2mm). This allows the chamber to decompress before the upward exhausting stroke, reducing pumping losses. By allowing the exhaust gas to exit over a longer moment of time, the exhaust port can also be smaller in cross sectional size, improving engine performance at lower throttle / lower flow moments.

Once the piston begins it’s upward stroke, the combined residual pressure and the pressure generated from the decreasing cylinder volume work to expel the majority of the exhaust gasses. Any left over exhaust gas creates dilution in the incoming mixture. This can be good or bad depending on you goal. Bad for power, but good for fuel economy and emissions since it displaces incoming fuel, acts as a defacto displacement reduction, and reduces NOx emissions by reducing the combustion temps; hence the purpose of modern EGR systems. Without getting too far into it, bigger cams create “valve overlap” which allows the intake pulse to blow down the chamber through the exhaust. It does this by actuating the intake valves before the exhaust valves are closed. As you can imagine, timing and valve position are important.

At this point the combustion chamber has created heated regions of the piston crown, valve, or chamber that will contribute to the next cycles detonation. These are also known as “hot spots.”

Flame Front Shockwave

Intake Stroke

A small fraction before the piston reaches TDC the intake valves begin to open. The incoming air : fuel mixture blows down into the chamber as the piston generates vacuum on it’s downward intake stroke.

2nd Compression Stroke

Once the piston reaches BDC it then begins it’s return; the compression stroke of the drawn mixture. The hot spots in the chamber have begun to warm the incoming air : fuel mixture.

During the compression stroke the piston travels upwards while the cylinder is still filling. The intake valves will begin to close a few degrees past BDC to allow complete cylinder filling. As the cylinder volume begins to decrease the air : fuel mixture is compressed together. This compression causes the molecules to rub against each other, which generates heat. The heat and pressure continue to build as the piston compresses the mixture. This pushes the mixture closer and closer to it’s auto-ignition point.

This causes a highly accelerated burn rate which ramps up cylinder pressure and temperature even further, which in turn causes an even faster burn rate. The burn rate moves further and further away from controlled and begins to fall into the explosion category; hence “detonation.”

To further the carnage the flame fronts slam into each other and cause a sharp, instant rise in cylinder pressure. This shock wave then travels through the piston, wrist pin, connecting rod, and attempts to shove the connecting rod into the bearing surface. The only thing preventing engine failure is about 0.002″ of oil film at the rod bearing. Even if this dampens the blow, the force is transmitted to the crankshaft, which creates a sharp torsional and compressive load. This continues as the waves continuously bounce around the cylinder.

This force is transmitted through the entire engine and the harmonic generated is what you hear as knock or ping. The frequency generated is a result of the engine bore and many other measures, but typically is around the 6400Hz range. It’s similar in mechanism to the sound generated by an aluminum baseball bat when it makes contact. It’s also what the knock sensor is actively listening for to determine the engine is knocking.

When the knock sensor, a piezoelectric sensor, senses the harmonic (i.e. 6400Hz) it signals the ECU to take action. This action is almost always to reduce ignition timing. Reducing the timing cools the combustion somewhat and gives less time for detonation to occur. If the knock sensor continues to sense knock it will continue to reduce timing further and at a faster rate. This is because detonation needs to be over-corrected due to the added heat causing further and more significant detonation events, even pre-ignition. It may require 3 – 7° of ignition timing correction to tame severe detonation.

Beyond moderate and heavy knock you get into what is known as superknock. When you have superknock it’s questionable if it even matters to reduce timing. Generally you’ve managed to reduce compression via piston ventilation or your connecting rod wants to leave the crankcase.

Various Detonation Levels vs. Pressure

What Causes Detonation?

There are several causes of detonation and each can be remedied multiple ways. Let’s break down the individual sources of detonation. It’s important to note that each can be additive or part of the cause. There is no hard and fast rule for it.

Ignition Timing (Advance)

A very common cause of detonation is running too much ignition advance. This causes long burn times during critical moments where charge density is highest and the burn rate is at its peak. Aggressive timing advance increases pressure and heat while the mixture is being compressed. This can cause the remaining mixture to detonate.

High Load / Low RPM (“Lugging the Motor”)

This is a bit of a silent killer. Most people associate low RPM with being easy on the motor and in most cases they are right, but low RPM also equates to longer windows of time for detonation to occur. The faster the piston travels, the quicker you get away from the high compression moment and the less time the mixture is subjected to heating from hot sources in the engine. In tuning, this is most of the reason why you need to slowly add back ignition advance as the engine RPM rise.

Adding high load (or high boost pressure / WOT) greatly increases the chance and severity of detonation. This is why nearly all OEMs recommend avoiding heavy acceleration in the lower half of the RPM range.

High Dynamic Compression Ratio

Most people express compression ratios using the static compression ratio generated by the reduction in total cylinder volume (head volume + deck height volume + swept volume) from BDC to TDC. However, the dynamic compression ratio is more complex, but is a better representation of the actual compression ratio.
Dynamic compression ratio uses the rod length, stroke, and rod angle, known as the rod to stroke ratio, or rod ratio for short, to determine the physical location of the piston when the intake valve closes. This begins the real measure of the compression ratio.
As an example, a stock engine with a 10.5:1 static compression ratio may have a dynamic compression ratio of 8.0:1, but adding a higher duration camshaft can lower this dynamic compression ratio to around 7.7:1. This is why big camshafts necessitate higher static compression ratios, to help offset the original loss.
Anything that alters the intake valve timing will also change the dynamic compression ratio. This includes secondary cam lobe profiles like those used on Honda’s VTEC as well as cam phasing technologies like BMW’s VANOS and Subaru’s AVCS. It’s important to adjust ignition timing to meet the needs of advancing or clocking back the intake valve’s timing. Here’s the rule for cam phasing:
Intake Cam Advance – This will close the intake valve sooner in the compression stroke. Advancing the intake cam will raise the dynamic compression ratio. This means you need to run slightly less ignition timing.
Intake Cam Delay – This will close the intake valve later in the compression stroke. Delaying the intake camshaft will lower the dynamic compression ratio. This means you need to slightly increase the ignition timing.

The 30° of intake advance range on the 08+ Subaru EJ257 engine will increase the dynamic compression ratio 1.33:1 at full advance.

One thing to keep in mind is that compression ratio does not linearly increase pressure and temperature. As the graph below will show, there is an increasing rate of both pressure and temperature rise as the dynamic compression ratio increases.

Adiabatic Heating and Pressure Increase vs. Compression Ratio

Thick Headgaskets / Reduced Quench

Running a considerably thicker headgasket opens up the area between the piston crown and pads on the combustion chamber, known as the quench area. The quench area is collaborative region between the cylinder head’s chamber design and piston crown. It relies on the attached boundary layer of molecules on both surfaces to displace virtually all of the air : fuel mixture inwards. This reduces chamber volume, which increases thermal efficiency. The quench effect also reduces the likelihood of detonation by creating large amounts of turbulent flow in the mixture, reducing available areas for hot spots, and reducing the distance the flame front needs to cover (which requires less timing advance).

Typical quench spacing is about 0.040″ or 1mm.

High Coolant & Cylinder Head Temperature

In most engines, the coolant passes first through the block and then to the cylinder heads. This reduces the available thermal capacity and cooling ability of the fluid at the combustion chamber and exhaust ports. Which in turn raises the temperature of the combustion chamber, leading to greater mixture heating and the reduction in detonation threshold.

During sustained, high load situations the coolant can begin to boil within the cylinder head(s). While a small amount of nucleate boiling is beneficial to cooling, there is a point where the vapor barrier builds and greatly reduces the cooling ability of the coolant. This will create a localized hot spot and most assuredly will cause detonation and/or pre-ignition.

Modifications & Tunes

It goes without saying that a bad tune is going to cause problems for you and the engine. This is why you should always go with a tuner that has a wealth of knowledge and experience. While every engine operates within the realm of physical law, it is beneficial to have specific knowledge about the ECU parameters, how the ECU handles and reacts to those parameters, locations of key sensors, and all of the little quirks and issues of the vehicle being tuned.

As far as modifications go, just about any modification that affects the volumetric efficiency (VE) or metering of incoming air flow will run a chance of increasing detonation. Likewise, body mods that reduce cooling flow through heat exchangers, such as a grill guard, can raise boosted air temps and cause greater chances of detonation. Here’s a list of common mods that require a re-tune, or should be re-tuned for.

Mods that Have to be Tuned

Fuel injectors
MAF / MAP sensors
Camshafts (Aggressive)
Changes in Boost Pressure (2+ PSI)*
Larger wet nitrous setups (e.g. 250-shot)

Mods that Should be Tuned

Intakes on MAF equipped cars
Exhaust manifolds, downpipes
Intake manifolds
Camshafts (Moderate)
Changes in Boost Pressure (1 – 2 PSI)*
Wet nitrous setups (e.g. 50-shot)

Mods that are Generally OK

Cat-back exhaust
Intercooler upgrades
Fuel pump
Intakes on MAP equipped cars
Fuel pressure regulator (as long as base fuel pressure is not lowered)
Water / methanol injection (or water injection alone)

• – This is a bit car dependent. Some factory tunes are better than others at making proper adjustments, while others will have major issues. Regardless, you will want to re-tune, the car will run a lot better and make better power.

Quench Area

Low Octane or Octane Dilution

Octane rating is a measure of a fuel’s detonation threshold relative to two fuels: n-heptane and iso-octane. There are two main methods for determining octane ratings: MON and RON. A higher octane fuel will rate similarly to a fuel mixture containing greater amounts of iso-octane; hence the name.

What is the Difference between RON, MON, and AKI Octane Ratings?

Motor Octane Number (MON) is a method of fuel testing that tests using a higher RPM, preheated air : fuel mixture, and varied ignition timing. This number will always be lower than RON figures. The MON rating of a fuel does not always scale with the RON. Three different 100 RON rated fuels could result in MON ratings between 88 – 92.
Research Octane Number (RON) is a widely accepted method for testing fuel using a standardized engine with variable compression ratios. The results are compared to a control fuel (n-heptane / iso-octane) to determine their RON rating.
Anti-Knock Index (AKI) is an average of the two testing methods primarily used to rate fuels in the US. US pump gas is based on the Anti-Knock Index (AKI).
US Octane to Japanese or European Octane (RON)

AKI + 4 = RON

So US 93 octane premium fuel is similar to 97 octane premium fuel in Japan or Europe. US 87 octane fuel is similar to the 91 octane base fuels in other countries.
Octane Rating of Common Fuels
Fuel - AKI (RON)
US Prem. Pump Gas - 93 (97)
US E85 - 96 (106)
Ethanol - 99 (108)
Methanol - 99 (108)
Toluene - 114 (121)
VP MS109 Race Gas - 105 (109)
VP X16 Race Gas - 116 (118)
Diesel - 15 - 20 (N/A)

MON vs. RON vs. Octane Index

What Octane does Not Tell You … Fuel Reactivity and Varied Auto-ignition Resistance

A 93 octane fuel from Shell will have a slightly different detonation threshold compared to the same octane fuel from another supplier. Even different formulations such as winter vs. summer gas can cause shifts in detonation threshold. This is because of the differences in fuel additives and the quantities of those additives between the different fuels.

Furthermore, a 104 octane gasoline will have a different detonation threshold versus a 104 octane ethanol fuel or a 104 octane toluene based fuel, even if you corrected for the difference in charge cooling.

The difference is fuel reactivity and it’s ability to resist auto-ignition at varied temperatures and pressures. A 93 octane gasoline may have greater knock resistance in an engine that has a higher charge temperature but lower compression ratio than the other way around. The relationship is not always linear, especially with varied homogeneity and the other multitudes of variables.

This is especially true of the MON testing method, which offers very little correlation to real-world knock performance in secondary full scale testing.

Obviously we can’t expect Joe or Jane to understand the complexities at the pump, and octane is a pretty close measure so we stick with that. Although some have offered a more respective alternative without market traction.

Octane Dilution & Bad Gas

Octane dilution can come from a variety of sources. However, the major sources of octane dilution are the gas pump and the crankcase.

Bad Gas at the Pump

The fuel at gas stations is stored in an underground tank. These tanks are typically sealed from the elements by covers, but these covers can be damaged, worn, or improperly sealed which allows water and runoff to enter the tank.

Alcohol’s affinity for water causes it to separate from the gasoline, which reduces the overall octane rating of the fuel. The water can also interact with the gasoline and further cause complications. The result is lower than expected performance and a high amount of detonation (knock).

Another cause of “bad gas” is due to either mistakes or deception within the supply chain. Refineries make mistakes that can cause entire batches of fuel to be contaminated. Fuel wholesalers and suppliers can make errors when filling the tanks, inadvertently putting a lower octane fuel into the higher-octane tank. Store-owners can also engage in deceptive tactics such as diluting high-octane fuel with low-octane fuel to improve profit margins on pump sales. Fortunately, these incidents are fairly rare.

Crankcase Oil Vapor aka “Blow-By” from the PCV System

An issue particularly troublesome on high RPM and high boost motors is aerated oil vapor being blown back through the intake track via the positive crankcase ventilation, PCV, system. The oil has a significantly lower auto-ignition temperature and will ignite early causing detonation in sufficient volumes.

The oil comes from the high-pressure power stroke bleeding gas past the compression rings (rings #1 – 2) and down into the crankcase. The crankshaft is spinning at a high rate of speed, which creates a very turbulent environment of air and fine oil droplets known as “windage.” These droplets coat the cylinder walls and help to cool the engine and lubricate the pistons, but they also get blown down through the PCV.

On modern vehicles, the PCV is routed back to the intake tube where the blow-by vapors are consumed by the engine. Typically this is not an issue, but in sufficient volumes it can be. This is why air : oil separators are installed on performance engines which are particularly prone to these issues.

Fuel Mixtures

It’s important to know that rich / lean mixtures are relative. Each engine will have an ideal air : fuel mixture ratio where cylinder pressure and temperature hit their highest figures. Typically this is around 11.8 – 13.2:1 AFRs, but lets assume that 12.5:1 is ideal for this example. The engine would make peak power at 12.5:1 provided the fuel would not detonate. However, in real life, we have to add fuel to slow the burn rate and reduce the chamber temps somewhat, resulting in a 12.0:1 ratio to avoid moderate detonation.

Octane Performance at Various Pressures and Temperatures

Lean Knock

Lean knock occurs because the fuel that normally would slow the burn rate is not present. The mixture burns quickly and as the pressure rises the remaining mixture detonates. Extremely lean mixtures will simply misfire rather than detonate.

Combustion Chamber Design & Head Material

Over the decades combustion chambers have evolved from large, slow burning designs like the publicly popular “HEMI” chamber to smaller, faster-burning, pent-roof designs. This has greatly improved detonation resistance and allowed for much higher compression ratios in modern engines along with improved fuel economy.

A slow burning chamber requires significant amounts of timing advance. Where a modern engine may use 20 – 25° BTDC an older chamber may use 40 – 45° BTDC. This gives significantly more time for detonation to occur.

Another consideration for older cars and trucks are iron cylinder heads. Ductile iron is incredibly resilient, especially with heat, but it also doesn’t conduct heat anywhere near as fast as aluminum. The result is less cooling of the combustion chamber and a greater chance for knock to develop with high amounts of continuous load or spark advance. It’s common for iron headed motors to run a degree or two less timing.

Running Too Hot of a Spark Plug Heat Range

Spark plugs are rated in their ability to shed / resist heating from the combustion process. This rating is known as a “heat range.”

Auto-Ignition Delay of Fuels (vs. P / T)

Colder Heat Range plugs have more insulation and shed more heat into the combustion chamber roof. They will always reduce detonation, but too cold of a plug can cause other issues like misfiring, lower performance, and fouling.
Hotter Heat Range plugs have less insulation and shed less heat into the combustion chamber roof. They will increase the chance of detonation, but a sufficiently hot plug is needed to maintain a healthy combustion cycle.

Each plug manufacturer has their own heat range scale. NGK for example offers a BKR5E plug which has a heat range of 5. An NGK BKR6E plug is one step colder with a heat range of 6. The BKR5E is standard on the naturally aspirated 140 HP Nissan SR20DE engine, but the BKR6E is the standard plug for the turbocharged 205 HP Nissan SR20DET engine.

High Intake Air Temperatures

The higher the temperature the more likely detonation is to occur. For naturally aspirated engines the major source for hot air is the engine bay. Running an open element intake under the hood ensures you will be feeding heated air to the engine. Even with a basic air box or divider the AITs will climb.
For supercharged and turbocharged engines the issue is much more dynamic. The air entering the air filter might be 100° F on a spring day, but after being compressed that temperature can exceed 400° F at high boost pressures. Fortunately, intercooling is far more popular and prevalent. An intercooler can shed off a large portion of that heat and get the air back down around 120 – 130° F, but it eventually will begin to warm up and lose efficiency.
Known as “heat soak,” the amount of heat energy being pumped into the intercooler is greater than the amount it can shed to the air or water passing through it’s core. Eventually the boost temperatures will rise. You could see 130° F turn into 230° F rather quickly with some stock intercoolers. This is when detonation is more likely to occur.

How to Prevent Detonation

Avoid Excessive Ignition Advance

One of the easiest ways to avoid detonation is to reduce the ignition timing. This is what the ECU does when the knock sensor senses detonation.

Downshift or Get into the Powerband

If you are driving a car with a 7000 RPM rev limit, avoid flooring it anywhere below about 3200 RPM. Downshift and use the powerband. Lugging the engine around at low RPM isn’t preserving your engine.

Tune for the Dynamic Compression

If you can tune the engine’s cam phasing, then you will want to either reduce timing, enrichen the mixture, or close the intake valve a bit later. If you can’t, then just be careful about how much throttle you give it while the intake cam phasing is advanced. Typically this shouldn’t be a problem unless you’ve modified something, and at that point, you really should be getting a tune.

Be Mindful of Detonation with Engine Builds

Here are 10 tips while building your motor:

1. Quench areas are there for a reason. Doubling the headgasket thickness is a crutch.
2. Deburr anything that is in the chamber. Seats, pistons, reliefs, valves, etc.
3. Cam specs affect your dynamic compression. Order pistons accordingly.
4. Cam phasing is important. Order camshafts accordingly.
5. Be mindful of heat and thermal load. Cool metal is happy metal, especially aluminum.
6. Minify frictional losses. Friction is heat and wear; it’s also power loss.
7. Choose a nice tight combustion chamber, if the opportunity presents itself.
8. Improve oil and coolant cooling. Run the highest quality oil you can afford.
9. Keep the compressor wheel in an efficient range of speed / pressure ratio.
10. Use a cooler spark plug heat range with higher power builds.

PAO vs. Ester Base Stock Oil

Be Mindful of Thermal Loads

Subaru STis have a relatively high piston failure rate due, in part, to the complexity and design of the power unit and the driving habits of their owners. Here’s an analysis of certain driving conditions that present an ideal foundation for detonation.

Stuck in Traffic + Sudden Acceleration

You’ve been stuck in stop and go traffic for 30 minutes, but suddenly you reach your exit and you go for it. You drop the hammer in 2nd gear and the EJ257 goes to work. Problem is … the 180° F air your turbo is ingesting is coming out of the turbo at over 400° F. That hot air is being fed to a heat-soaked, top-mounted intercooler (TMIC), which hasn’t had time to cool after being cooked under the hood. The result is feeding your engine 350°F air at 15 PSI of boost pressure. Add in additional compression from the AVCS cam phasing and you can see just how easy it is to destroy those brittle hypereutectic pistons.

High Speed Runs

You’re out on a cool night and you run into a Mustang that wants a piece of you. You start off in 2nd gear and the race is on. Third gear goes by and then 4th gear, it’s neck and neck and you go into 5th gear. After being heated from the quick sprint through 2nd – 4th gears the continuous load during 5th gear will add more and more heat to the system. At this point, the tune comes into play.

Ignition timing needs to decay the longer the car stays into boost to accommodate the rising temperatures from the intercooler heat soaking and the combustion chamber rising in temperature. Many OEMs work this into their algorithmic tuning parameter(s), as does Subaru. As the coolant temperatures rise the ECU will begin to reduce timing. Unfortunately the Subaru system does not use a post intercooler temperature sensor and in most cases light detonation will begin to occur. If you stay in the throttle the car will be noticeably heat-soaked and feel flat as well. Ideally, the fuel mixture should be enriched to further reduce chamber heating. Aftermarket tuners can even trim individual cylinders and adjust timing / fueling depending on gear. It’s common for 5th and 6th gears to have reduced total ignition timing.

On modified cars, depending on the mods, the car can quickly develop heavy knock and cause ring land failure. Certain mods like radiators, intercoolers, oil coolers, etc. will help prevent detonation in this case.

In short, be mindful of how much heat you’re asking the engine to work with. After you’ve run it hard it’s a good idea to cruise a bit at speed to let the built-up heat escape via the heat exchangers. An intercooler can shed heat very quickly, in a matter of seconds at highway speeds, but the oil and coolant both may need a few minutes to settle back.

Run an Effective Air : Oil Separator (Breather / PCV Setup)

Don’t vent the breathers to the open air. You want to maintain vacuum on the crankcase and heads as this improves ring seal, power, and efficiency. Venting oil vapor under the hood is also just a bad idea. Instead, plumb an effective air : oil separator canister inline to strip the oil vapor out of the breather gasses and run the cleaned air back into the intake tract.

There are other methods for pulling vacuum on the crankcase such as going to a multi-stage dry-sump, vacuum pumps, or plumbing the PCV system to a shallow angle feed in the exhaust and relying on the Bernoulli effect to pull vacuum. These are meant for specific applications and should be installed by experienced builders.

Run a Group V Ester Based Oil – Motul 300V

Synthetic PAO oils found in Group IV have about 10% higher auto-ignition temperatures than conventional oils. The ester based Group V stock oils have higher auto-ignition temperatures compared to synthetic oils, which offers slightly more safety against oil vapor induced detonation and pre-ignition.

Spark Plug Heat Ranges

In US Government backed testing ester Group V oil allowed for an additional 1.5 of timing advance before knock developed compared to 3 other PAO Group IV oils.

High performance oils also help to reduce friction and cool key components in the engine. In the event of detonation, it’s absolutely vital that the motor oil be capable of doing all that it can to absorb the blow. This involves proper flow and a stable profile to maintain pressure at all temperature ranges, especially elevated ones. The oil film is all that stands between detonation and bearing failure.
You can get Motul 300V here for a fair price

Choose a Proven, Experienced Tuner

Quick Tips to Choose a Tuner for your Car
Ask yourself, or the community, or the tuner these questions:
Q: Do they have a proven history of reliable tuning?
A: A long history with your make / model.
Q: Are they familiar with your application? (i.e. Turbo LSX, Turbo 3-Rotor, etc.)
A: Worked with a wide diversity of setups, including your specific engine and power level / fuel.
Q: How do they handle re-tunes if there is a problem or simple change?
A: Quickly, in-person or via email at a fair price (or free).
Q: How do they handle engine failure? (i.e. Respectful, Thorough, Proactive?)
A: A good tuner will help to find the cause of the failure and handle it quickly and fairly.
Q: How long have they been tuning similar applications?
A: Technology changes quickly as do applications, so a few years or longer is ideal.
Q: Where will they be tuning your car and what equipment will they use?
A: Turbo vehicles absolutely should be tuned using an eddy brake dynometer such as a Mustang MD-600, or MD-500-AWD, if you have the choice. This is because the tuner can induce high load conditions and mirror the typical road conditions you will encounter. Generating high amounts of load with the eddy brake will create earlier spool-up and longer acceleration times in a gear. This allows the tuner to create a tune that is much safer and less likely to detonate.
A typical inertia drum dyno, such as most Dynojet dynometers, is suitable for sub-3000 lb. naturally aspirated engines and sub-2500 lb. turbo, supercharged, and nitrous motors. While a tuner can create additional load by selecting a higher gear, it is ideal to use an eddy brake dyno. Tuners should also use a properly calibrated and fresh wideband O2 sensor and provide ample cooling fans to keep coolant, oil, and charge temps low.
Q: Can they handle your specific setup?
A: Tuning an engine to make big power for a 9-second 1/4 mile run is much easier than tuning the same engine to run for a 30-minute long road course event. Likewise, tuning an engine to produce 800whp out of a turbocharged 2.5L Flat-4 is significantly different than the same engine with simple bolt-ons. Look for a tuner that has a wide experience base and isn’t going to be learning on your fresh build.

Run Adequately Sized Intercoolers & Heat Exchangers

Radiators, oil coolers, and intercoolers are all absolutely vital to keeping your engine happy. Just because your coolant temps or charge temps are OK putting around town or running through a gear or two does not mean they are adequate! Ideally, you should be able to beat on the car for minutes and see very manageable temperatures.
It’s also absolutely vital that you give your heat exchangers a good, clean, and well-ducted stream of air flow.

E85 is Amazing for Power and Avoiding Knock

Seriously, it’s that good. The only complaint about it is the low range and typical alcohol issues. You should really look into it for any forced induction application or big bore N/A motor. It cools the inlet charge and is very tolerant of timing.

Conclusion

There are a multitude of causes that generate detonation, and each has a specific fix, but the modal tone behind knock mitigation is simply to reduce the total amount of heat inputted into the engine’s cycle and slow the combustion rate down. While this ultimately limits an engine’s specific output and fuel economy, it greatly enhances the longevity of the motor. However, there are many things that can be done to raise the detonation threshold with careful design and implementation of engine systems.

Thanks for Reading!

This is my first article on CarThrottle. If you liked this one and would like to see more, feel free to follow me. If you have any questions or comments, please respond below and I will do my best to respond to them.
Since I’m new, here’s a little bit about myself. I’ve lived in Austin, TX nearly all of my life and enjoy just about anything with wheels and a motor. I’ve owned quite a few cars ranging from a 07’ Porsche GT3RS to a 89’ Nissan truck (my first car). I currently daily drive a very unimpressive 99’ Honda Civic CX hatchback and also own an 11’ Subaru STi hatchback with a blown motor (ringlands) and a 95’ BMW M3. Motor in the Subaru will be going back together with a forged bottom end, cams, and a GT3076R that I have sitting in the garage.
You can view the original article, along with others here