Mike’s Carburetor

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We have a ton of technical information for just about any carburetor and new information is being added on a daily basis. Check back again.

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Mike

Carburetor Percolation

Percolation can happen when your engine gets hot, then you turn the engine off and the fuel boils over, sometimes over the top of the carburetor, or more often, simply evaporates. Back in the day we called this vapor lock, which simply meant that the fuel turned to vapor before getting to the engine.

This has been a more common problem these days because our gas has a lower boiling point than it used to. Yup you guessed it, ethanol.

This makes it hard to start the next time. You have to crank and crank, or pour a bit of gas down the carburetor to get the engine started.
What can you do:
  • One of the best ways, but a lot of work, is to run a 3rd line from the fuel pump back to the gas tank. This extra line will help cool the fuel, allowing the fuel pump to pump gas instead of vapor. There are some fuel filters out there that include a return port. There are also return regulators available.
  • Put heat wrap around the fuel line in the engine compartment.
  • Put a spacer under the carburetor mount. These are hard to find so you will probably have to make one. Yup, a mill would be handy about now. And you will probably need to put longer studs in the manifold to accommodate the extra height.
  • Instead of a spacer add extra mounting gaskets. A couple of 1/32 thick gaskets isn’t going to do much. Hopefully thicker gaskets will be available for your engine.
  • Add a helper electric fuel pump. Just before startup, you run the electric pump for a few seconds, then turn it off. Use only a low pressure pump. 7 lbs max. You may end up also adding a regulator because you don’t want the pump to overrun your mechanical pump. Most 1 & 2 bbl carburetor run 4-4.5 lbs. Bigger carburetors might handle 5-6 lbs.
  • Cool the engine with a cooler thermostat, bigger fan, or bigger radiator.
  • Try different brands of gas. Different octanes won’t help you here.
  • Use non ethanol gas if you can find it.
  • Remember when we used to put wooden clothes pins on the fuel line? The clothes pins act like a heat sync, drawing heat away from the fuel line and my wife says the wooden clothes pins are still available at the dollar store.
Anyhow, the basic answer here is to cool your engine and/or fuel.




How a Choke Works Integral Type

When the engine is cold a richer fuel mixture is needed. As it warms up the mixture must be leaned out. This is where the automatic choke circuit comes into play.
Choke ThermostatChoke Thermostatic Coil

The choke shaft extends through the carburetor into a round housing. Inside the housing there is a thermostatic coil spring. This spring will wind & unwind depending on the temperature. When cold the thermostat will hold the choke valve closed. As the temperature warms up, the spring expands and allows the choke valve to open.



Vacuum BreakChoke Vacuum Piston

The choke vacuum piston is linked to the choke butterfly by a small linkage. At idle, which will have full vacuum, the piston will be pulled into the piston well. This puts pressure against the thermostat coil trying to open the choke valve slightly.


Offset Choke Valve

Not all carburetors will have this air valve. Marvel Schebler & the Holley 1 barrel carburetors are a few examples that do. The air valve is placed offset on the choke valve. This keeps the choke from causing a too rich condition.

stove PipeStove Pipe

Most automatic chokes systems will use a stove pipe to heat up the thermostat coil. The pipe heats up, using the exhaust manifold and the heat is then pulled up to the thermostat using vacuum from the carburetor, which is fed by the intake manifold.

Motorcraft 4300 Power Piston

The Motorcraft 4300, 4 barrel carburetor power piston is used to supply extra fuel when powering up.

Motorcraft 4300Motorcraft 4300

The power piston is made of brass (at least the piston itself is) and fits into the float bowl top. See #26 in the diagram. The purpose of the power piston is to supply extra fuel when you are in the power mode. At idle and low speeds, vacuum is at the highest level and pulls the power piston up and off of the power jet (closing it). The power jet is located in the bottom of the float bowl. As you gain power, vacuum starts to drop and the spring on the power piston rod forces the power piston down and pushes the pin on the power jet open. This allows more fuel to feed into the carburetor throat.

It is very important that the power piston works smoothly. When you push on the spring and pin end, the piston should move into the top, then when you let go it should snap back. The power piston is moved by vacuum alone, so it needs to work without any binding whatsoever.

You will need to remove the power valve from the well in order to give it a good cleaning. Buff the brass piston using a wire wheel. Polish the well with crocus cloth to make it smooth. Lubricate with Silicon Spray Lubricant.




Gas Tank Fuel Gauge

For most original gas tanks, the tank gauge unit is located in the gas tank.


Tank Gauge UnitThe tank contains a float that is attached to a resistance device similar to that used in an electric oil pressure sender. See the resistance unit in the illustration. The travel of the float up, or down, causes the resistance to vary, depending on the depth of the fuel in the gas tank.

Most gauges are designed to read empty when one or two gallons of gas is left. This allows the driver to get gas when the gauge indicates empty before running out of gas.

When the float drops, current flow to ground through the bimetal metal coil will be less, because it must travel through the more resistance wire. This cools the bimetal haripin and pulls it together. When the tank if filled the contact slides up, cutting out resistance and current flow increases. This heats the hairpin and the ends separate, causing the needle to move toward the full mark.

Gas Gauge

 

 




Tips on Removing Frozen Parts

Over the years I have learned the hard way how to remove screws & bolts that are frozen. Using the techniques below I seldom need any specialty tools for removing screw, bolts & nuts.

Here are some ideas that might help you:

Removing the Small Screws on the Choke, or Throttle Shaft

Take your time removing these screws. It will pay off big time. These screws are usually mushroomed on the threaded end. Using a dremmel tool, grind the threaded end flush with the shaft. Using a screw driver that fits the screw head well, twist the screw counter-clockwise. It is sometimes a good idea to turn the screw back in, then out again. This helps flush out rust particles. Don’t turn too hard, or the screw will break.

Not coming out? Put a block of some kind on the threaded end to prevent the shaft from bending, then hit the screwdriver with a hammer while you try to turn the screw. This will sometimes break the screw loose.

Still not coming out? Using a butane torch heat up the area around the outside of the screw. Don’t apply too much pressure, or you risk bending the shaft.




Did you break the screw? You will have to drill & tap. Using a drill bit (and a good one), just shy of the screw diameter, drill out the screw. If you do this carefully you will be able to remove the screw without damaging the threads. The trick here is to have a good set of small drill bits.

After inserting the new screws, you can mushroom the end, or as I do use thread locker.

Frozen Shafts

The best way to un stick frozen shafts is to heat the area outside of the shaft and tapping on the end of the shaft. The shaft will almost always come loose. If it doesn’t then it is most likely beyond repair.

Frozen Screws, Bolts or Nuts

When a screw is damaged to where a screw driver won’t hold, use a drift punch and hit it a few times with a hammer. This will cause the screw slot to shrink hopefully enough to allow the screwdriver to work. The banging will often times jar the screw.

For bolts use the same drift punch technique to see if the bolt comes loose. Avoid using 12 point sockets. A 6 point will give you a better grip. When a bolt start to loosen, then tightens up, stop. Try moving the bolt back and forth to help loosen it up.

Still frozen? Apply heat around the outside of the screw, bolt, or nut.

Always use good tools and the correct tool on nuts & bolts. That does not include a cresent wrench.

Nut or Bolt Has a Stripped Head

Use a flat file to file the flat parts and remove the mushroom edges. From there try a smaller socket or wrench. Sometimes moving from a US wrench to a metric wrench will do the trick, otherwise a vise grip will be in order. Again applying heat will probably help the nut, or bolt move easier.

Stromberg WW Worn Throttle Shafts

Stromberg Worn Throttle Shafts

Stromberg WW carburetors are notorious  for having worn throttle shafts. Unfortunately unlike most carburetors, the WW wears out the shaft instead of the throttle body.  As I mentioned, most carburetors wear the throttle body and while not a simple process, re-bushing the throttle body on these carburetors is very doable as long as you have the required tools, like reamers and good drill bits. We used to be able to get new throttle shafts to replace the worn shafts, but they haven’t been produced for several years now and finding a used donor carburetor is very difficult unless you happen to find one that has been sitting on the shelf for several years.



To our rescue is someone that I have consulted with many times in the past, “The Old Carburetor Doctor”. Jeff, the owner, has a fix for this problem, which he does when rebuilding the Stromberg WW. He tells me that he will repair your throttle body without a complete rebuild if that is what you want. He just asks that the throttle body be stripped down completely.

Here is what is says about this problem.

Stromberg WWs are no problem. Yes, the shafts are always worn, but we have developed a fix:  I plug the (usually) free right-hand end of the shaft bore with a welch plug, and I rebush the left-hand (throttle lever) end with an extended bushing which allows the un-worn part of the shaft outside of the casting to be supported by new bushing material.  Just look at a WW and you will see how it accommodates this fix; the factory should have done it that way in the first place!

To have your WW rebuilt, you can call Jeff at 800-945-2272. Please do not call Jeff for technical advice. That isn’t what he does. He is a carburetor restoration expert. Leave your technical questions here on this site. Jeff does not sell parts of any kind.

Late to the Electric Party

April 1st, 2016 Tesla unveiled their much anticipated Model 3. Thousands put down deposits, even though Tesla itself says, “Model 3 will begin production in late 2017,… ” That’s a long wait, but early adopters aren’t easily dissuaded, as shown by demand for the impressive Tesla Model S. But just how innovative is the electric car?

1890: the party begins

Electric Car

The first four-wheeled electric Vehicle took to the roads of North America in 1890. Eight years later Ferdinand Porsche (yes, that Porsche,) was driving his electric P1, which he followed with the worlds first hybrid car. By 1900 28% of the cars built in the US were electrically-powered. (Admittedly, only 4,192 cars were built in total that year.)

1900 saw the founding of the Baker Motor Vehicle Company in Cleveland, OH. One of many electric car start-ups, Baker prospered, thanks to a reputation for quality, until the arrival of the electric starter.





What really killed the electric vehicle

The Model T launched in 1908, and the rest is history, as they say. Well not quite. Many people weren’t convinced of the benefits of internal combustion. The early gasoline vehicles were noisy, smelly, and hard to start. They had a crank at the front of the engine that had to be turned by hand. When the engine “caught” and started to run the crank would fly around, injuring more than a few automotive pioneers.

Thanks in large part to Henry Ford’s efforts, gasoline powered vehicles were less expensive than electrics. By 1916 a Model T could be had for $650, (not an insignificant sum,) but an electric roadster would run around $1,730. Economics played a part in pushing out the electric car, and Baker Electric were one of many to cease manufacturing, but the final blow was delivered by one Mister Charles Kettering.

Now largely forgotten, (except by the students attending the college named after him,) in 1912 Kettering invented the electric starter. Instantly, this changed the acceptability of gasoline vehicles. Sales grew rapidly while electrics disappeared, until the late 1990’s.

They’re back!

Electric cars were largely forgotten until the late ’90’s. That was when, responding to a clamor for “greener” vehicles, (mostly from California,) GM created the EV1. An unattractive blob, it was slow with a limited range. Sales were miniscule, but it might be argued this was also the dawn of the modern electric vehicle era.

Toyota launched the first generation Prius in 1997. Initially sold only in Japan, it reached the US in 2000 some months after the Honda Insight hybrid. It wasn’t an instant hit but dramatic rises in the price of gas saw car buyers take notice, and sales climbed.

A hybrid isn’t a pure electric vehicle as it carries a gasoline engine, but the growth of hybrids, along with legislation on gas mileage, stimulated interest in electrics. In 2008 Tesla started selling the electric-only Roadster. In 2010 Nissan gave us the all-electric Leaf, in 2012 Tesla launched the Model S, which was followed by BMW unveiling their i3.

The electric car is most definitely back and you won’t need carburetors, or fuel injectors.

O2 Sensors – Engine Performance from a Capsule

O2 Sensors – Engine Performance from a Capsule

Long gone are the days when car engine were simply using 4, 6 or 8 pistons, a carburetor and a few other auxiliary elements in order to make the vehicle move forward. While, from a mechanic’s point of view, such powertrain units were simpler and easier to fix or upgrade, they featured a big downside: efficiency.

More efficient thermal engines needed a way to create a better mixture of fuel and air and make use of better motion delivering mechanisms, all to generate a bigger power output. While various materials have replaced iron in engine construction to ensure a higher degree of kinematic movement, to enhance air and fuel mixture, you would first need to figure out how much of each product gets mixed within the cylinder.

Obviously you can’t just section a running engine in half to check it out; this is how the need of O2 sensors was created.

Where and how does it work?

In case you are wondering, yes, your car is most likely to have at least one oxygen sensor mounted right at the end of the exhaust manifold. It’s just one of the dozen sensors modern cars use in order to increase efficiency and power output; after all, that’s what all is about: getting more and more of it.

If the term O2 sensor or oxygen sensor doesn’t sound familiar to you, it may be because this very same capsule with a wire at the end is also called a lambda sensor.

Does that ring any bells?

The placement of the O2 sensor on the exhaust manifold isn’t random; in fact, that is the best place to create a precise estimate on how much oxygen actually gets used in the air-gas mixture happening inside the cylinders. There are two main cases:

  1. Too much oxygen

When there’s too much oxygen used while mixing air and fuel, we are calling it a lean mixture. What happens is that during the mix, the air to fuel ratio (AFR) exceeds its preset value. To create a better picture, a regular gasoline engine works at an AFR of about 14.7:1. This means that for every part of gasoline, 14.7 parts of air should be used to attain an efficient combustion. If more oxygen gets through, peak pressure inside the cylinder increases and by default, chances of knock increase. When a cylinder knocks, it can basically create a rotational force that opposes the one generated by the crankshaft, generating severe consequences.

 

 

  1. To little oxygen

We’ve found out that too much oxygen is definitely not as good as it may have been initially presumed. However, the other extreme isn’t promising. A low oxygen level within the mixture (an AFR below 14.7:1) won’t allow the entire amount of fuel to be burnt, and thus generate an efficient combustion process. This is called a rich mixture. The immediate result is a considerable increase in fuel consumption; those injectors are pumping more fuel than the available oxygen is able to aid burning.

An oxygen sensor constantly monitors the amount of oxygen output traveling through the exhaust manifold, then sends the acquired data to an Electronic Control Unit (basically a computer for the vehicle) which then adjust the amount of fuel being pushed through injectors into the combustion chamber. Since it’s purely electrical, an oxygen sensor varies its electrical input in order to feed data to the ECU: 0.9V for rich and 0.1V for lean mixtures.

What is it made of?

The probe itself features a ceramic cylinder with platinum electrodes plating both on the inside and on the outside. On top, a metal gauze protects the whole system, like a capsule. It is important to know that oxygen sensors only work effectively while heated at about 600 F (or 316 C). That is the reason why modern sensors also feature heating elements added to the ceramic cylinder, speeding up the heating process. Unlike them, older sensors based solely on the exhaust gas heat to warm up.

Oxygen sensor failures

The best indicative for the wellbeing of an oxygen sensor is the way your vehicle performs. A lower overall performance may be caused by a faulty oxygen sensor, but it isn’t always the case. First of all, it is perfectly normal for a vehicle to exhibit lower performance when cold started. It takes a while for the lambda probe to heat up; until then, since it gets no input from the sensor, the Electronic Control Unit of the vehicle will supply a preset amount of fuel, usually a little above the normal Air to Fuel Ratio.

Electronic Control Units also consider input data from engine coolant sensors when “deciding” how much fuel to inject into combustion chambers; this is why a faulty coolant sensor indicating a higher temperature will cause the ECU to push less fuel through injectors.

If your vehicle traveled more than 100,000 miles, then find out that this equals to the average lifespan of a heated lambda probe. Although you may not feel any serious downshifts in performance, it may actually be a good idea to replace your car’s oxygen sensor with a new one, maybe even opt for a premium product.

 

Premium Oxygen Sensors

Is there an actual reason you should switch to premium sensors or it’s just a new marketing stunt? The truth is, yes, your car can benefit from having a premium oxygen sensor installed. Considering the fact that premium quality sensors are built with higher grade technology and come with various prerequisites such as coated threads with anti-seize compound, fuel efficiency and power output of your vehicle may shift from good to better.

Although premium sensors are mostly after-market products, they are built by the same brands employed by major automakers to develop OEM parts. It is, however, important to check full compatibility with your vehicle before acquiring a new oxygen sensor.

 

 

What Kind of Fuel Mileage Can We Expect

While fuel efficiency isn’t the only factor when deciding on which car to purchase, it is an incredibly important one. Considering the current prices for gasoline, as well as the country’s tumultuous relationship with many oil-producing nations, fuel efficiency can determine your financial future. Rather than changing your plans on which class of car to purchase, you can instead make sure to look into fuel efficiency when making your car decisions.

  • Fuel-Efficient Hatchbacks
    • The vehicles boast some of the best fuel economy in the industry. Many of these vehicles work in tandem with electric engines in order to minimize the fuel needed to power the vehicle. While many of these vehicles can be expensive on the front end, they can end up saving money, depending on the distance you plan to drive your vehicle. The 2015 BMW i3, for example, boasts a whopping 139 miles per gallon (38mpg on gas engine only). Even if you don’t choose to go with an electric car, you might consider another fuel-efficient hatchback. The Toyota Prius is a more affordable option that still gets up to 44 mpg.
  • Subcompact Cars
    • Not everyone is going to prioritize fuel efficiency. Subcompact cars, like the Honda Fit, might be a reasonable option for people looking to avoid hatchbacks and hybrids. The Fit is calculated at 33 overall miles per gallon. Small doesn’t always mean “efficient.” The Scion xb is a small car with only 23 overall miles per gallon.
  • Compact Cars
    • The Honda Civic and Volkswagon Jetta are both on the higher end of fuel economy in their class. The hybrid versions of these vehicles offer the best mileage, while the regular versions are also quite efficient in their use of fuel.
  • Sporty Cars
    • Just because you are looking for a sporty car doesn’t mean you have to sacrifice on fuel prices. Mini Coopers, while sleep and sporty, also offers reasonable fuel efficiency. Mini Coopers maintain an overall score of 30 miles per gallon; however, some sporty cars fare much worse. The Chevrolet Camaro Convertible, for example, gets only 17 overall miles per gallon, which is almost half of that of the Mini Cooper. This just proves that no matter what type of car you are looking for, you need to look into how much money you will be spending on gasoline.
  • Midsized Cars
    • Midsized cars can be a very responsible decision for people who are looking for practical yet efficient vehicles. One of the best options for midsized cars is the Mazda6 Sport. The Mazda gets up to 32 miles per gallon, with the Nissan Ultima close behind at 31 miles per gallon.
  • Upscale/Luxury Cars
    • Upscale Luxury vehicles doesn’t necessarily mean fuel-inefficient. The Tesla Model S, for example, gets up to 84 miles per gallon in tandem with the electric engine. The Lexus ES, which isn’t an electric or hybrid model, still gets up to an overall 26 miles per gallon. The Chevrolet SS, on the other hand, gets only 17 overall miles per gallon.
  • Small SUVs
    • SUV doesn’t have to be synonymous with gas guzzler. These small SUVs offer comfort and size without entirely sacrificing fuel efficiency. The Subaru Forester, for example, gets up to 28 overall miles per gallon, which rivals some of the more “practical” options.
  • Midsized/Large SUVs
    • The Hyundai Santa Fe, which is on the larger end of SUVs, still gets up to 23 miles per gallon. There are also several hybrid SUV options, such as the Toyota Highlander Hybrid, which gets up to 25 overall miles per gallon. Some larger SUVs; however, prove much less fuel efficient. The Ford Expedition, for example, only gets 14 overall miles per gallon.
  • Minivans
    • While minivans can be incredibly practical, they don’t always offer the best mileage. Even the Honda Odyssey, with some of the best mileage in its class, only  gets up to 21 miles per gallon. The Chrysler Town and Country fares even worse, at 17 miles per gallon.

As vehicles continue to evolve, fuel efficiency keeps getting better and better. Even if you aren’t willing to purchase an electric or hybrid vehicle, there are so many options within each class of car, that it’s important to make sure that you aren’t choosing a car that will end up costing you more money than you intended. Depending on how much you drive, fuel can be incredibly taxing on your financial stability. While you don’t necessarily need to make any sacrifices on the class of car you purchase, you might consider paying special attention to fuel efficiency when looking into potential buys. Not only will you save money, but you will be doing your part to help the environment.

Injector Types

Different Injector Types – How Do They Work?

You have probably been driving your car around for years without giving too much thought to the principle of action behind the engine. You don’t need an engineering degree to understanding the basics of an engine. The purpose of a gas-based engine is to transform controlled fuel explosions into kinetic energy, which is further transmitted to the wheels through a gearbox. The fuel is collected through a fuel pump from a tank then it’s delivered and injected into the engine.

The injector

Injectors

 

A critically important component within the injection mechanism is the injector. It sprays a finely tuned amount of fuel into the ignition chamber where a piston compresses it then a spark plug makes it explode and create kinetic energy. As previously mentioned, the amount of fuel sprayed by the injector is highly tuned by the ECU (electronic control unit). Any variation would prove to have a considerable impact over the vehicle performance, usually lowering it.

In order to optimize performance based on the type of fuel used, purpose of the vehicle and to adhere to the latest technological improvements, more than one type of injector has been developed. Currently there are 3 main injector types being used in automotive engine construction: top-fed, side-fed and throttle body injectors.

Throttle body injectors (TBI)

Initially introduced in airplane construction, throttle body injectors are also called single point injectors. Unlike their more Throttle Bodymodern counterparts, single point injectors are located directly inside the throttle body rather than on a rail.

They were the first upgrade of the classic carburetor system, and thanks to its design, a throttle body injection system can make use of mostly the same components as the carburetor did.

Along with their compatibility on older carburetor based throttle systems, throttle body injectors are also relatively cheap to repair or replace when compared with the other available injection systems. However there is also a drawback. Although computer-controlled, due to their emplacement and way of action, throttle body injectors are not very efficient. The fuel is dumped into the intake, creating what is known as a “wet manifold”.

Multi point fuel injection

 

Also known as port injection, multi point fuel injectors are designed to work as a group, with each engine cylinder having a fuel injector of its own. Injectors are placed right outside the intake valve, the fuel vapor is ensured to be delivered completely to the ignition chamber.

This allows a better tuning of air/fuel ration while in the same time it lowers chances of fuel condensing inside the manifold, as it Injectorsometimes happen with the throttle body injection systems.

Even with the high proximity placement of the injector, multi point injection systems still lack a perfect suction of the fuel inside the ignition chamber; it is however, more effective than TBI systems.

Sequential injectors

 

Based on the multi-port injection system, sequential injectors are also assigned one per each cylinder and attached as close as possible to the intake valve. However, unlike regular MPIs, sequential injectors are controlled individually by the ECU (electronic control unit), allowing them to open one at a time.

Sequential injection allows for fuel to be delivered solely when the intake valve opens so it directly travels inside the cylinder chamber. In case of regular MPIs, all injectors fire at the same time regardless the state of the intake valve. Sequential injectors can be timed to spray fuel in the same manner spark plugs are set to ignite it.

Fuel economy is increased with the use of sequential injectors. However, incomplete fuel consumption may arise when injectors are poorly tuned, leaving traces on the intake manifold or over the surface of the valve.

Direct injection

 

Used on more recent engine types, direct injection systems bypass intake manifolds and valves, spraying fuel directly inside the Injectorignition chamber. Computer-controlled, direct injectors are timed to spray fuel differently according to engine type.

Diesel fuel is injected either through a high-pressure common rail connected to injectors. The other option is to use unit injectors which increase the pressure of the fuel within the injector rather than within the common rail.

Ultra lean burn is achieved when using direct gasoline injection (also known as Fuel Stratified Injection – FSI, or Gasoline Direct Injection – GDI) while also completely removing “wet manifold” issues and reducing emissions.

Although they provide more performance and better fuel efficiency, direct injection systems are also more expensive to repair or replace when damage occurs.

 

Side-feed and Top-feed injectors

 

Along with emplacement injection type, fuel injectors also differ according to the way fuel is supplied to them. Injectors can be either is supplied with fuel from the side (side-fed) or from above (top-fed). While the overall aspect may not look very different to the naked eye, there is a series of advantages and drawbacks for each type.

Side Feed InjectorTop Feed Injector

Side-feed injectors are fit inside the common-rail. The rail is fixed either to the engine block or the manifold. Side-feed injectors are constantly surrounded by fuel; given this, they benefit from improved cooling, thus being less prone to damage. The side-feed is the most common used injector type.

On the other end of the barricade are top-feed injectors. Unlike their side-feed counterparts, top-feed injectors are attached between the rail and the cylinder chamber. This makes them easier to replace or upgrade, as there’s usually no need to adjust or replace the common rail as in case of side-feed injectors. However, due to the fact that they are not surrounded by fuel at all times, top-feed injectors may suffer from a lower life expectancy, needing to be replaced more often, especially in high-performance vehicles.