Posted on February 27, 2019February 27, 2019 by maxtorque — Leave a comment

Exhaust Gas Temps, Turbos, Turbo Shields and Making Power

Posted: February 19, 2019

Categories: Tech

ABOVE:An unshielded turbo means you’re leaving a lot of horsepower and turbo efficiency on the table. Increased turbo lag, lower max boost and increased underhood heat are all negative effects of an unshielded turbocharger.

You’ll see us talking up using Heatshield Products exhaust wrap and/or insulation to keep more heat in your exhaust system for multiple reasons. First is to cut down on the amount of heat the exhaust system radiates, which can increase underhood temperatures and interior heat; the exhaust pipes running under the floor will heat the floor and transmit that heat into the passenger cabin. Second, keeping more heat in the exhaust system helps increase performance, especially in turbocharged applications. You may be wondering, how does it increase performance?

With a gas or diesel engine, exhaust gas temperature (EGT) has a direct correlation to engine performance and health. Understanding EGT can be a tuning tool (especially for turbocharged applications) and assist in wrapping your headers and exhaust with an effective thermal barrier or insulation for solid performance benefits. EGT directly relates to exhaust gas velocity, in that as the temperature rises, the exhaust gas moves at a higher velocity. With an internal combustion engine (gas or diesel) the EGT will rise as the engine makes more power or as the air/fuel mixture leans out. In the case of a lean condition with the engine, an EGT that is too high can lead to major detonation and cause severe engine damage. Back in the 1970s and the era of carburetion and tightening emissions standards, the factory would tune engines to run as lean as possible to heat up the catalytic converters faster so that they could quickly perform their intended purpose and also to burn up as much as possible in the combustion chamber to reduce the amount of fluorocarbons and other pollutants left form the combustion process.

What does a safe higher EGT (meaning the air/fuel ratio is within optimal parameters) mean in a normally aspirated engine when it comes to better performance? As the EGT climbs and raises exhaust gas velocity for each cylinder, exhaust gas scavenging increases. More spent gases get sucked out of the combustion chamber while the exhaust valve is open. The more spent gasses that can be removed before the exhaust valve closes, the better the next combustion cycle will be as a fresh fuel/air charge is brought into the cylinder.

With a turbocharged engine, increased EGT helps on multiple fronts. The first is the same as with the naturally aspirated engine: getting all the exhaust gasses out of the combustion chamber for a better burn when combustion takes place. Second, with increased EGT, the turbocharger spools up to create boost much faster and also cuts down on turbo lag. This is from the increased velocity of the exhaust gasses, thanks to the higher EGT. The third benefit of the higher EGT is that with increased exhaust gas velocity, the turbo can spool higher and create more boost, leading to an increase of horsepower once the wastegate and blow-off valve are tuned accordingly for the increased boost.

It’s easy to keep more heat in the exhaust system to help boost the EGT. Ridiculously easy. Start with the turbo itself. A proper turbo heatshield on the exhaust side will help insulate the turbo housing to keep more heat in and boost the EGT. There’s also the added benefit of cutting down on the amount of heat the turbo radiates underhood, which lowers underhood temps and the negative affects of things getting hot under the bonnet. There are multiple options from Heatshield Products when it comes to turbo heat shields, including a DIY turbo shield kit for odd sized/shaped turbochargers.

Heatshield Products Lava Turbo Shield installed on the BroDozer monster truck

ABOVE: Adding a turbo heat sheet like the Lava Turbo Shield pictured above helps keep significantly more heat inside the turbo housing to increase EGT and exhaust gas velocity that decreases the time it takes the turbo to spool up and start making boost, along with reducing the amount of heat the turbo radiates underhood or under the vehicle (if the turbo is remote mounted). You can also see where the exhaust pipes feeding the turbo have been insulated with Heatshield Armor for the same reasons. This particular Lava Turbo Shield is mounted on Heavy D’s BroDozer monster truck. A true testament to Lava Turbo Shield’s ruggedness, this one has survived some serious beatings and looks pretty good for something that has been installed since June of last year. It is constantly exposed to the elements like dirt, mud and heat including an engine fire. Adding an exhaust wrap or exhaust insulation like Heatshield Armor to the feed pipe (on remote mounted turbos) and the downpipe helps to shield the turbo and to keep the EGT up to help keep EGTs up before and after the turbo, which helps sustain increased exhaust gas velocity longer for better performance and turbo consistency.

Posted on February 25, 2019February 25, 2019 by maxtorque — Leave a comment

Boost vs. Compression: Benefits of High Boost Levels and High Compression Ratios

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Boost vs. Compression: Benefits of High Boost Levels and High Compression Ratios

DSPORT ISSUE# 125 0 Comments

One-thousand horsepower, four-cylinder engines are today’s reality in import drag racing. This reality includes the leading-edge forced induction and engine-management technologies that make power production the easy part of building a racecar. Today’s performance engines are running at higher boost pressure levels and higher compression ratios than ever before. Understanding how both compression ratios and boost pressures affect performance is a key to maximizing performance from your street or race vehicle.

By Michael Ferrara // Photos by DSPORT Staff

4-stroke Engine Basics

Without going into a lengthy explanation of internal combustion engine dynamics, your vehicle’s engine is a machine designed for energy conversion. Using a four-stroke cycle, a fuel-and-air mixing strategy and a spark for ignition, the internal combustion engine’s first task is to convert the chemical energy stored in the fuel into thermal energy (heat) through a process called combustion. The engine’s second task is to convert this thermal energy into kinetic energy in the form of horsepower at the flywheel. How well an engine can convert the heat (thermal energy) into power (kinetic energy) is quantified by an engine’s thermal efficiency. An engine’s thermal efficiency is highly influenced by the engines static compression ratio.

Compression Ratio

As the name indicates, the compression ratio of an engine indicates how much the air-fuel charge is compressed during the compression stroke of the four-stroke process. A 10-to-1 compression ratio means that the air- fuel mixture gets squeezed down from the full volume of the cylinder to a volume that is just roughly one tenth of the cylinder’s size. So how does an engine’s compression ratio affect performance? All other factors being equal, an engine with a higher compression ratio will deliver a higher thermal efficiency. This means that the engine is able is turn more of the heat generated from the combustion process into horsepower instead of wasted heat. In basic terms, higher thermal efficiencies translate into additional horsepower and better fuel economy.

How much additional power can be expected with a higher compression ratio? The old-school rule of thumb is that each additional point that the compression ratio is raised will deliver an additional 4 percent power. In fact, more accurate projections can be found in the accompanying DSPORT chart. These values were obtained using the thermodynamics equation to establish the thermal efficiency of an Otto cycle engine.

Plugging through this equation we find an increase in compression ratio from 8.0:1 to 11.0:1 should result in a 9.2-percent increase in power. Likewise a reduction in compression ratio from 11:1 to 7.0:1 should result in a 12.3-percent decrease in power.

Believe it or not, high-compression engines of the late ’60s, with compression ratios up to 12.5:1, had higher thermal efficiencies than many of today’s engines. For the same size engine, the older engine would have been more fuel efficient if they had the fuel, cylinder head and ignition technologies of today combined with the high-octane gas of the 60s.

Boost Pressure

In dealing with naturally-aspirated applications, high compression ratios are the key to serious power levels. In dealing with forced-induction applications, it’s well known that increasing boost pressure on a properly sized turbocharger will increase power production (at least, to a point when the capacity of the turbo or fuel system is exceeded). Of course, the big downside to higher boost pressures is that the likelihood of encountering engine- damaging detonation also increases.

The balance of boost versus compression ratio has been an engine builder’s and tuner’s challenge for years. Picking up a copy of one of the 60’s- technology forced-induction manuals will highlight their solution. The higher the boost pressure, the lower the compression ratio of the engine. For “serious” race forced-induction setups compression ratios of 7.0:1 were not uncommon.

Fortunately, poor manifold and fuel delivery designs, as well as low-efficiency “blowers,” are not found on too many of today’s popular performance vehicles. Today, the average high-performance street or strip turbocharged four-cylinder race engine sports a compression ratio of 9.5:1, with some even running compression ratios as high as 11.5:1 or more on alcohol or E85. Modern technology allows our racing generation to get the best of both worlds. High boost pressures with high compression ratios.

Fuel and Detonation

Octane & Knock

The octane rating indicates the likelihood of the fuel to experience “knock.” Knock, the audible sound given to the condition, also goes by the names of detonation. Knock is detrimental to performance and reliability and it needs to be avoided. Knock occurs when the fuel-air mixture in the cylinder doesn’t experience an ideal burn (the process of combustion). An ideal burn allows the mixture to combust evenly initiating from the spark plug until all of the air-fuel mixture occurs. In a laboratory environment, the ideal burn will occur at about 100 feet per second in a vacuum. In the turbulence of an engine’s combustion chamber, good flame speeds may be up to 250 feet per second. During detonation or knock the burn rate will see a violent 2000 feet per second explosion instead of a burn. Burn rates are crucial to how pressure builds in the cylinder.

The burning of the air-fuel mixture results in a pressure increase. Ideally, pressure builds in the cylinder at the optimum time reaching a peak pressure somewhere between 17 to 20 degrees after top dead center. This allows the cylinder pressure to produce the most horsepower at the crank. When knock occurs, the pressure cycle within the cylinder doesn’t occur as desired. In fact when knock occurs, the original flame front and pressure wave from the desired spark-ignited front meet an undesired auto-ignited flame front. When these two pressure waves meet, the pressure oscillations produce a “knocking” sound. When knock occurs, power is reduced, while rod bearings, connecting rods, head gaskets and pistons may suffer slight damage or catastrophic failure depending on the severity of knock. Elevated temperatures generally result from knock and this can lead to preignition problems that cause the air-fuel mixture to ignite even before the spark fires.

Knock or detonation is not the same as preignition. Pre-ignition occurs when the air-fuel mixture becomes ignited before the spark plug fires. Sometimes elevated temperatures or a hot spot in the cylinder can cause preignition. While both knock and preignition cause undesired burns of the air-fuel mixture, the difference between the two is simple. Knock or detonation occurs after the air-fuel mixture has started its burn, preignition occurs before. Both produce undesirable pressure waves that affect performance and can translate into engine damage.

Need for Higher Octane

If your engine is experiencing knock, you’ll need to run a higher-octane fuel or retard ignition timing. The need for fuels with a higher octane rating generally occurs as peak cylinder pressures rise. Peak cylinder pressures tend to rise as compression ratio, volumetric efficiency, ignition advance and boost pressure rise.

The general rules are simple. Naturally-aspirated engines will need a higher- octane fuel as either compression ratio is increased or ignition timing is advanced. Forced induction engines respond the same, but will also need higher octane as boost pressures increase.

You may have heard the following: “don’t use too high of an octane fuel or you will lose power.” This is a half-truth. Having a fuel with too high of an octane will not make your engine lose power. However, having a fuel with a burn rate that is too slow can make your engine lose power. In general, the popular components used to make the octane of a fuel higher also slow the burn rate. Of course, that is just a generality and it doesn’t hold true for all fuels.

Alternative Fuels: Methanol & Ethanol

Methanol has been used as an alternative racing fuel to race gas for a number of years. One advantage of methanol is that it can be run very rich without a significant drop in power. This can allow the tuner to use the fuel as a cooling tool in the tuneup. However, methanol packs only about half of the energy found
in gasoline. Fortunately, you can burn about twice the mass of methanol compared to gasoline for the same amount of air. Depending on whom you ask, zero to ten percent more power can be made with methanol over racing gasoline.

There are significant tradeoffs for the power gains. First, methanol is highly corrosive. The entire fuel system must be methanol compatible and even then you will probably experience corrosive issues. It’s best to flush the system of methanol at the completion of the race. Methanol also requires twice the fuel delivery and storage capacity of gasoline. Your fuel cell or gas tank will either need to double in size or you’ll only be able to travel half as far. Injectors and fuel pumps will need to have twice the flow capacity of a gasoline setup as well.

Ethanol or ethanol-blends like E85 are now more popular than ever for street and racing use. Ethanol is the same type of alcohol found in alcoholic beverages. To avoid legal issues, manufacturers blend 98 percent ethanol with two percent gasoline to produce E98 or 85 percent ethanol with 15 percent gasoline to make E85. The advantage of ethanol is that it does not have the corrosive issues that you find with methanol. However, it does have a lower energy content than methanol. The Venom Racing team became the first import drag racers to run in the 6s running on ethanol as a fuel.

Dished pistons (front)are most common on lower-compression engines, while domed pistons (rear) tend to appear in higher compression engines.

17:1 Compression Ratio and 45psi Boost Pressure

No. Don’t go out there and try to build a 17:1 compression ratio race engine with the boost pressure cranked up to 45psi. As the late Gene Humrich of Centerforce Clutches used to always say, “For every action, there’s going to be a reaction. And if the repercussions of the reaction are worse than the benefits of the action, you are going to get screwed.” So what is the reaction to the action of raising your compression ratio on a forced induction application? A combination of too much boost or too much compression will increase the likelihood of detonation.

So how much compression ratio should you run for a specific amount of boost pressure? It depends primarily on three factors. Fuel quality, intercooler efficiency and the tuning state (how well the fuel curve and ignition curves are set) of the engine. Methanol or E98/E85 engines will allow higher compression ratios than racing gasoline. Better intercooler systems will also allow higher compression ratios. Some tuners can optimize the engine despite having the narrower tuning window of a higher-compression/high-boost application. In the end, engine development is the only way to get the answer to the question of the perfect compression ratio and boost pressure.

Looking back nearly 50 years ago, Chevrolet reigned supreme when its ultra- high-performance, 283-cubic-inch small block generated an unprecedented 283 horsepower—one horsepower per cubic inch. High compression pistons, a racing-profile solid-lifter camshaft and a pair of four-barrel carburetors made the impossible possible. Today, high output variable-cam-timing engines from Honda and Toyota generate almost twice that figure with outputs approaching 2.0 horsepower per cubic inch. Double-overhead camshafts, four-valves-per-cylinder, computer- controlled valve timing, advances in cylinder head design and electronic fuel injection take credit for the advances in naturally-aspirated power output.

Technology is always developing and new rules replace old rules when it comes to performance. However, the relationship among compression ratio, boost pressure, detonation and fuel octane is one that will always remain. Understanding this relationship allows tuners to setup an engine to maximize performance for a given fuel quality.

Posted on February 16, 2019February 16, 2019 by maxtorque — Leave a comment

Fwd: The Secret Life of Bearings: A Test Of Bearing And Oil Wear Rates

By Jeff Smith February 14, 2019

It can be a very tortuous existence for engine bearings. Think about it. Bearings are there to be abused and many engine builders treat them as a consumable. Most of the attention bearings receive is heaped upon design, clearances, and oil feed theory. But once the engine is broken-in and running, attention shifts to other concerns.

This story looks at how bearings, coatings, and the oil you choose can have a dramatic effect on bearing life. As you might expect, this means spending a little more money up front, but the results may make that an easy decision.

The engineers at King Bearings have recently developed a new performance rod and main bearing called the pMaxBlack. This is a bearing with major changes to the tri-metal alloy, in a quest to create a material that is still soft enough to handle a high-output engine, while simultaneously offering increased fatigue resistance and load carrying capacity. The inside story on how King developed this bearing is steeped in alloy-metal technology, so let’s just say they figured out a way to make a bearing stronger to withstand the abuse from increased power levels while still making it soft enough to properly do its job.

Bearing Theory

Race or performance oriented tri-metal bearings are built intentionally soft because, if a rod journal deflects or a crankshaft bends under high load, the journal may contact the bearing. If the bearing is soft enough, it merely wears slightly. Unfortunately, cold startups tend to take their toll on engine bearings, since the crank rotates for several revolutions before the film of oil builds up between the bearing and the journal. This is why you often see race teams pressure lube the engine each time before cold startup.

The King pMaxBlack performance bearing isn’t a coating but rather a new bearing top overlay that increases hardness by 24-percent yet with 17-percent greater fatigue resistance. Adding the pMax Kote coating makes these bearings even more wear-resistant.

King ‘s aluminum-alloy bearing material (HP prefix) is used in very high-load applications. According to Ron Sledge of King Bearings, “The duration of time of the loading is what separates which bearing to use, HP vs. XP or XPC. The HP will handle very high loading for a shorter period of time (like drag racing) whereas the XP or XPC will handle very high loading for longer time periods, like circle-track and off-road racing.”

“The advantage of the HP bearing is that it will tolerate handling debris and crankshaft deflection better than the XP or XPC because of the 0.012-inch thickness of the aluminum layer.” The babbit overlay on the XP bearing is only 0.0005-inch thick. This thinner layer does not tolerate debris and crankshaft deflection as well.

Bearing Hardness

BEARING MATERIAL	HARDNESS RATING
Aluminum	40 Hv
Tri-metal	11-14 Hv
pMaxBlack	18 Hv

Keeping Up With Technology

Today’s 21st-century street engines are now making more horsepower than pure competition engines from as little as two decades ago. Builders naturally expect the bearings to keep up with these enhanced power plateaus. This is why King Bearings developed the pMax Black bearings.

Taking this idea a step further, King developed a coating for this bearing called pMaxKote. This becomes the ultimate-performance King bearing, employing what the company calls a nano-composite polymer coating. According to Sledge, the term nano-composite just means it is made up of nanosized materials in a polymer base. The coating is added on top of the pMaxBlack overlay and does not increase the thickness of the overall bearing wall.

To maintain the same dimensions, King compensates with the thickness of the intermediate copper layer to allow for the 0.0002-inch thickness of the pMaxBlack coating. This allows for maintaining the same oil clearances as uncoated counterparts. The coating protects the bearing from mild abuse and is designed to be extremely wear resistant – even when slight contact is made with the crankshaft.

This is what happens when a connecting rod bearing runs for a short time at max load with insufficient lubrication. Connecting rod bearings often fail first because they are heavily loaded and are last in line for lubrication.

Put To The Test

All of this sounds really good, but the question becomes, how would this coating work in the real world of internal combustion engines? King thought that an independent test would be a good idea, so they collaborated with Lake Speed, Jr. at Driven Racing Oils, and the team at Shaver Specialties, where they set up an abusive test schedule. The plan took shape by placing a relatively mild 440 hp, 383ci small-block Chevy on the dyno. They used a purposely excessive cylinder test regime that would heap serious load on the connecting rod and main bearings and then evaluate the results.

This required a baseline or control combination, with a couple sets of King XP, Tri-metal bearings, and Driven supplied a mineral-based, 5W-20 as the baseline lubricant. To make this a true lubricant comparison, the engine oil additive packages had to be exactly the same. Because there were no off-the-shelf mineral-based and synthetics with the same exact additive package, Speed supplied both custom-blended oils for the test.

This is an example SPEEDiagnostix report sheet from this test. It shows the type of results you can expect as part of the evaluation. Any warning signs are immediately highlighted in yellow or red. If everything is good, the check marks are in green.

Neither is available as an off-the-shelf oil with this specific blend of additives, but they both are representative of high-zinc and high-phosphorus lubricants. Speed chose a lower viscosity base-oil which would intentionally decrease the oil film thickness and increase potential bearing contact and wear.

As you can see from the results chart, the differences are measured in as little as single-digit parts-per-million (ppm) numbers. In order to ensure these numbers are accurate, Speed also performed a flush procedure between each of the four tests. This involves draining the test oil, removing the Wix oil filter, and refilling with Driven’s break-in oil BR30 along with a new filter, and then running the engine for 30 minutes, including two full-power dyno runs. Then the break-in oil is drained and the filter removed and the next oil is added. This exact same procedure is repeated when the bearings are changed. This ensures that the results will be as accurate as possible.

This photo shows the uncoated XP rod bearing on the right after running loaded for over three hours using a 5w20 conventional oil. The same test with the same oil was performed on the King pMaxBlack XP bearing on the left. The wear reduction is obvious.

The accompanying results chart also lists the additive package. Zinc and phosphorus (ZDDP) are anti-wear additives that most enthusiasts are familiar with. Molybdenum and boron are friction-reducing additives while calcium is employed as a detergent. These were the main additive package ingredients for both the conventional and the synthetic oils so that the only difference was the base oil.

After the first test sequence with the petroleum-based oil, Shavers’ engine builder, Keith Chrisco, removed the first set of bearings and added a second set of identical XP bearings. He then ran the engine using the mPAO-based synthetic 5w20 oil.

The third test involved switching to a new set of King’s pMaxKote rod and main bearings, but returning to the traditional mineral base 5w20 oil. The fourth and final test saw the installation of another new set of pMaxKote bearings run this time with the synthetic oil. This created a comparison of coated and non-coated bearings with traditional and synthetic engine oil.

These are five of the lower, uncoated XP bearings as they were pulled directly from the engine after running the test using conventional oil. As you can see, there is considerable wear.

The evaluation criterion for each test would be a comparison of the wear count of the different metals (in ppm) by analyzing the oil drained from each test. The testing was performed by SPEEDiagnostix, a new oil evaluation company using the same metal spectrometer techniques as is used in current Formula 1 racing.

The best way to really load these bearings and ensure that the test schedule would be both consistent and survivable was to pull the aforementioned small-block Chevy down to an extremely low RPM with a high load. The SuperFlow dyno was able to pull this little Chevy down to 1,450 rpm for a total of three hours and fifteen minutes for each of the four tests. During this time, the low-RPM test was interrupted so the engine could also be subjected to a complete test up to just past peak horsepower a total of 14 times. Oil and water temperature was also closely monitored.

Instead of horsepower, this test was all about survivability. In the attached chart, we have condensed a much more expansive report down to the wear results. The important wear materials are iron, copper, lead, tin, and aluminum. Both the standard and coated King tri-metal bearings are made up mainly of copper, tin, and lead so these would be the major elements that would indicate bearing wear. Aluminum would originate mainly from the pistons while the iron would likely be sourced from the cylinder walls.

While the trace material numbers are relatively low PPM counts, it is the differences from each test that is compelling. Let’s start by explaining each category in the results sheet. The Oil Type indicates the type of oil – either conventional or synthetic. The Bearing Type indicates whether the bearings were coated or uncoated. The Oil Viscosity Index is a rating system applied to engine oil that indicates how much an oil viscosity changes over a wide temperature range. The higher the number, the more thermally stable the oil is over a wide range of temperature. This means that as the oil warms up, it loses less viscosity.

This bearing and oil test demanded the engine be subjected to multiple tear-downs to replace all the bearings but the results were well worth the effort. Shavers’ small-block has been torn down so many times it should have zippers. To save time, Chrisco changed the main bearings without pulling the crank. He loosened all the main caps and carefully removed the old bearings and installed the new ones by pushing the bearing while turning the crank.

Also note, that we’ve listed each additive component in ppm. This is important because this clearly shows that the additive packages for both the conventional and the synthetic oils were identical. So this means that any reduction in wear materials (when comparing oil) must be attributed to the quality of the base oil and not to the additive package.

Now that we’ve got that handled, the results indicate that the combination of King Bearings’ MaxKote bearing with an mPAO synthetic base oil is an excellent way to drastically reduce wear in an engine. As you can see, the baseline total wear number of 35 ppm (created simply by adding up the wear numbers of each individual element) using a conventional bearing and a mineral-based oil, was reduced 74-percent by using a high-quality mPAO synthetic like that from Driven Racing Oil, combined with the pMaxKote bearings.

Just changing to the coated bearings while retaining the conventional oil also produced a significant improvement, reducing the overall total wear count from 36 to 21 ppm, which is a 40-percent improvement in wear. This reveals the significant increase in durability from the coating itself. This is especially important when you get into a cost-performance ratio because the coated King bearings are roughly only 40-percent more expensive compared to non-coated rod bearings for a small-block Chevy.

You will note in the results a somewhat higher-than-anticipated lead wear metal reading in the third test with an uncoated bearing and the synthetic base oil. The lead is the dominant metal found in a tri-metal bearing overlay (lead babbit), so wear was slightly higher in this case compared to the conventional oil. While every attempt was made to keep the testing as standardized as possible, there are any number of variables that could account for this higher number. While the lead numbers were higher than any other test, the total wear metal count was still lower than uncoated bearings with conventional oil.

Shavers’ 383ci small-block Chevy has been horribly abused over dozens of dyno tests over several years and is still going strong.

While the synthetic oil used in this test was a custom blend to standardize the additive packages, Speed said that a Driven oil that would be comparable to the mPAO synthetic used in this test would be Driven’s XP line of race oils. These are available in several different viscosities based on how the engine would be used, ranging from a 0W to a 15w-50. This oil is more expensive, but when you consider the expense involved with rebuilding an engine, the cost is easily justified, because the oil will last so much longer with lower wear metal contamination.

Engine wear isn’t something that most hot rodders stress over, but with the sizable investment that most engines demand, perhaps it is a subject that should be given its fair share of attention.

Posted on February 16, 2019February 16, 2019 by maxtorque — Leave a comment

MLS Head Gaskets – Engine Sealing Do’s And Dont’s

By Casey Putsch February 11, 2019

Any business owner or life-long gearhead that personally does the majority of their own wrenching, knows the value of things beyond money. Time, for one, is huge. It is rewarding to work on your own stuff, but nobody likes doing a job more than once. Using good tools is paramount to success – as is the confidence in knowing a job you completed is going to be rock solid.

Success on the track, street, and/or the show field comes down to preparation. Many people who don’t find the same success of others – but try everything they can think of – will often blame money or politics. The truth however, is different. Successful people know a few tips, tricks, and techniques, to prioritize things in a way that less successful people might regard as luck or even magic.

MLS gaskets are designed with two to five sheets of spring or carbon steel sandwiched between the head gasket’s sealing material. Precisely shaped beads and stoppers work with the specific steel properties to increase the clamping force around the combustion chamber.

Speaking of “magic,” if you don’t know enough about Multi-Layered Steel (MLS) head gaskets, this is going to change your automotive life. Everyone focuses on power-making big items that are generally in your face, exciting, and expensive. But all of those parts have to work together. Preferably, without ever breaking.

Head gaskets are ridiculously important, but people rarely give them much thought. Enthusiasts buy the swap meet gasket kit, and place the gasket in the necessary locations. But, head gaskets have to contain millions of explosions, deal with the expansion and contraction of dissimilar metals, and a wide range of chemicals and extreme temperatures. Basically, they are expected to perform silently and flawlessly forever.

MLS Head Gasket Science

We contacted two leading gasket companies, Cometic and Fel-Pro to get the “magic” sorted. We have used products from both of these companies in the past. It turns out, even our jaded and sometimes arrogant selves learned a lot of seriously important information. That made writing this article very rewarding.

No other coatings are necessary on MLS head gaskets. – Jim Daigle Fel-Pro

Chief Engineer Rich Larson and Senior Product Manager Jim Daigle, of Fel-Pro, walked us through all the details. Fel-Pro traces its history back 101 years, that’s when the company began making felt products and got its big break making gaskets for the Ford Model T. One century later, that start has evolved into the company becoming the market leader in automotive gaskets.

Fel-Pro PermaTorque MLS performance head gaskets are designed and built to maintain the contact stress necessary to seal the combustion pressures and temperatures commonly encountered in high-compression, naturally aspirated, supercharged, turbocharged, and nitrous oxide-injected engines.

“Cometic was started in 1989, and was dedicated to serve the powersports industry,” said Mickey Hale. “To this day, Cometic products are 100-percent American-made, utilizing state-of-the-art technology to be able to make quality, custom gaskets for any application. The company is also family owned. Cometic is a customer-driven company, and is able to offer world-class workmanship directly to race shops and even a one-off part to the little guy.”

If you need to change the bore size and/or thickness of a gasket, the process starts with a phone call. After Cometic’s in-house technical sales team understands your needs, they work directly with design engineers to create exactly what you need.

MLS head gaskets are exactly as the name sounds. They are very thin sheets of stainless steel held together and coated with specialized surface coatings. They also have embossments to help seal when they are torqued into place. Generally, these gaskets utilize three layers, but there are specialized gaskets that may have up to seven layers depending on the application and needs.

MLS gaskets generally cost more than composite gaskets.

What makes MLS technology so special, is its ability to perform with a greater workload and deliver a better job sealing with much less effort. If we look at old-school composite head gaskets that utilize a fire ring, the basis of comparison becomes clear as to what makes MLS superior. Not only is MLS used across the board in modern day OE cars, it gets refined as time goes by, and is the likely choice for the future of internal combustion engines. There is virtually no reason not to use MLS head gaskets in your application.

Nerdy Details Make Big Differences!

By nature of the stopper and bore beads (embossments) and the spring-like effect of the metal, the builder now has a much simpler task of getting a solid seal at the combustion chamber. This, with less torque required from the head bolts or studs. It is also more forgiving if that torque is not applied evenly. Don’t take that as a reason to be haphazard with your installation. We’re just saying this gasket has your back like no other. This is also vastly important to OE-engineers going for every bit of performance, emissions control, and efficiency. By requiring less torque to make the same seal, there is less chance of casting distortion and cylinder wall distortion.

MLS technology can benefit both old and new engines. But, if your engine was originally designed to use composite gaskets, you will want to have the surfaces checked to make sure they are smooth enough for MLS gaskets, or have them re-machined.

The specialized coatings on MLS gaskets seal the two surfaces on the microscopic level. When you first start up and heat-cycle your engine, this chemically bonds the seal to the metals. An important note: this is also the point of no return, making the gasket non-reusable. An MLS head gasket can be cold-torqued more than once before final assembly, only if the surfaces are smooth and clean.

Ready to install with no extra coating needed

Heat cycles and dissimilar metals are the scourge of a head gasket. How many people have freaked out about blowing a head gasket if their car got hot? MLS head gaskets are the best design for coping with the movement of different metals expanding and contracting during the engine’s heat cycles. Think of it this way: those multiple layers can slide at the microscopic layer rather than falling prey to the laws of physics that are trying to rip your old-school composite gasket apart.

Getting Custom

Why are there different amounts of layers? Different applications and head-and-block modifications have specific needs. For instance, you might wish to alter compression ratio a bit or dial in your quench area.

A good sealing surface not only means smooth, but also straight. Checking for waviness as well as how rough the surface is will help determine MLS gasket sustainability.

With Cometic, gasket thicknesses range from .027- to .140-inch thick. MLS gaskets have a very wide range of thicknesses that will effectively seal and be just as reliable as a thinner one. That doesn’t mean that it is a cure-all for improper engine building, or for salvaging an old head that has been milled too many times.

As an example, it is possible to go from a .040- to .080-inch-thick gasket in a big block and drop a point of compression if you are looking to get away from detonation in a forced-induction engine. Of course, the ability to change gasket thickness gives you the ability to fine-tune the quench area.

Adjusting head gasket thickness is really only for fine tuning. – Mickey Hale, Cometic

Mickey pointed out, “people get too hung up on quench. Unless your build is already dialed-in perfectly, there are more important aspects to get right – such as compression ratio. Adjusting head-gasket thickness is really only for fine tuning.”

Got Boost?

Cometic also has the MLX gasket line, which is a special tooled-gasket. While it isn’t infinitely variable in design like an MLS gasket, does have a ring around the combustion chamber that laughs at 20-plus pounds of boost.

MLS gaskets can be very forgiving, but only under strict circumstances. The surfaces of both the block and heads must be sufficient to allow them to properly seal. The tolerance for roughness of the sealing surfaces is much lower – almost half of what you can get away with if using a composite gasket. The smoother the better.

Myths And Hot Tips

We asked both Cometic and Fel-Pro two very important questions. Why should anyone buy from your company or start a relationship with you? Also, what do you wish people knew, but you can’t get through to them?

Fel-Pro was happy to point out they are the industry leader in gaskets. The company’s strength is in creating a wide range of gaskets for various needs. It is able to back them up with rigorous real-world testing and quality control.

Fel-Pro’s lower-cost composite gasket still has a place in the performance world.

Cometic pointed out that they are performance-oriented head gasket people, and not just a one-size-fits-all company. Starting a relationship with them allows the builder to grow, as they can custom-build any gasket. You can buy the products off the shelf at places like Jeg’s or Summit Racing, or you can call them directly for your needs.

Several sheets of stainless steel are layered to give the desired thickness. An MLS gasket’s ability to protect against blow-out in high-cylinder-pressure situations is due to the embossed layers acting as a “spring” to account for increased head lift. The outer layers are embossed, but also feature a special coating to help it conform to both the head and block surfaces.

Daigle wanted people to know, “no other coatings are necessary on MLS head gaskets. As long as your surface preparation is correct, the gaskets are made to specifically work with properly prepared bare metal. That means a properly decked and on-plane surface with a surface finish of 70Ra or lower.” Ra value is a surface roughness measurement. He also wanted to caution builders that today’s hi-tech lubricants can make threads of head bolts and studs so slippery, that it is easy to yield a bolt. That means it may read the correct torque spec, but you have over-pulled the bolt or stud. Lastly, for gasket surfaces, keep it clean and dry.

Just as important as the gasket, is the order in which you torque the head fasteners. Always start with the center-most bolt or head stud, then work your way out in a spiral pattern. That helps spread the loading over the head gasket evenly to give it the most strength possible.

Cometic wanted to add, if you are changing your head-gasket thickness, don’t forget your pushrod length and gasket thickness may have to change as well. Also, do not use copper spray coatings with its product. It is designed to be used without it. Lastly, your fasteners (head studs and bolts) are key. Make sure you are holding that head down to proper manufacturer specifications and torque procedures.