**Using Fuel Adjustment to Rev Limit Engines**

When it comes to rev limiting engines, there are several methods that can be used to achieve this goal. One common method is to use a fuel adjustment, which involves adjusting the air-fuel mixture to reduce power output and prevent the engine from increasing in RPM. This approach is often used on production vehicles, where the engine management system is programmed to limit power output above a certain point.

To set up a fuel adjustment for rev limiting, the fuel injector is typically adjusted to provide less fuel than usual at higher RPMs. This reduces power output and helps to prevent the engine from increasing in RPM. The fuel adjustment can be fine-tuned to achieve the desired level of rev limitation. When using this method, it's essential to ensure that the fuel injection system is calibrated correctly to avoid any issues with fuel flow or engine performance.

**Lean Air Fuel Mixture for Rev Limiting**

Another approach to rev limiting involves running a lean air-fuel mixture, which means reducing the amount of fuel injected into the engine. This can be achieved by adjusting the fuel injector to provide less fuel than usual at higher RPMs. By doing so, the engine's power output is reduced, and it becomes more difficult for the engine to increase in RPM. This method is often used on high-performance vehicles or those with turbochargers.

Running a lean air-fuel mixture also has an additional benefit: it reduces emissions. By reducing fuel flow, there is less unburned fuel in the exhaust system, which leads to lower emissions levels. When using this approach for rev limiting, it's essential to ensure that the engine management system is calibrated correctly to avoid any issues with fuel flow or engine performance.

**Ignition Control and Two-Step Rev Limiters**

When it comes to ignition control, there are two common approaches used in rev limiters: cutting ignition completely and retarding timing. The first approach involves stopping spark output altogether when the engine reaches its desired RPM. This is often used on production vehicles or those with anti-ag systems.

However, this method can lead to issues if not implemented correctly. When the spark is cut off, combustion ceases, but fuel continues to flow out of the exhaust system at high pressure and temperature. If the vehicle has a turbocharger, this high-pressure gas can spool up the turbine and cause the engine to increase in RPM.

To avoid this issue, some rev limiters use retarding timing instead. By delaying the ignition spark, the engine's power output is reduced, and it becomes more difficult for the engine to increase in RPM. This approach also helps to reduce emissions by minimizing fuel flow out of the exhaust system. When using a retarding timing method, it's essential to fine-tune the ignition control system to achieve the desired level of rev limitation.

**Two-Step Rev Limiters and Anti-Ag Systems**

There is often confusion between two-step rev limiters and anti-ag systems. While both methods aim to prevent engine over-revving, they operate in different ways. Two-step rev limiters are designed to limit power output at higher RPMs by adjusting the air-fuel mixture or ignition timing.

However, some two-step rev limiters can be associated with anti-ag systems when used improperly. If not calibrated correctly, these rev limiters can lead to issues such as excessive fuel flow out of the exhaust system, which can spool up the turbocharger and cause flames to appear in the exhaust. To avoid this issue, it's essential to use a high-quality ignition control system that is designed for rev limiting.

**Retarding Timing for Rev Limiting**

Another approach used in rev limiters involves retarding timing to prevent engine over-revving. By delaying the ignition spark, the engine's power output is reduced, and it becomes more difficult for the engine to increase in RPM. This approach also helps to reduce emissions by minimizing fuel flow out of the exhaust system.

When using a retarding timing method, it's essential to fine-tune the ignition control system to achieve the desired level of rev limitation. By doing so, the engine will sit at the set RPM, and the ignition spark will be triggered later than usual. This approach can be effective for both naturally aspirated engines and those with turbochargers.

**Rev Limiting with Fuel Adjustment vs. Retarding Timing**

When deciding between using a fuel adjustment or retarding timing for rev limiting, several factors come into play. Both methods have their advantages and disadvantages. The fuel adjustment method is often easier to implement, as it involves adjusting the air-fuel mixture to reduce power output.

However, this approach can lead to issues if not implemented correctly. If the fuel injection system is not calibrated correctly, it can lead to problems with fuel flow or engine performance. On the other hand, retarding timing provides more precise control over the ignition spark and can be more effective for achieving the desired level of rev limitation.

Ultimately, the choice between using a fuel adjustment or retarding timing depends on the specific application and requirements. Both methods have their benefits and drawbacks, and it's essential to carefully consider these factors before making a decision.

**Conclusion**

Rev limiting engines requires careful consideration of various factors, including engine management systems, fuel injection systems, and ignition control systems. By understanding the different approaches used in rev limiting, including fuel adjustment and retarding timing, you can make informed decisions about which method is best suited for your specific application. Whether using a lean air-fuel mixture or retarding timing, it's essential to ensure that the engine management system is calibrated correctly to achieve the desired level of rev limitation.

"WEBVTTKind: captionsLanguage: enhello everyone and welcome in this video we're going to be talking about two-step rev limiters what they are and how they work now a two-step rev limiter very simply is just having two different stages of having a rev limiter so you're going to have one at a lower RPM and one at a higher RPM the lower one is typically going to be used for launch control so when the car is stationary and then you're going to have a second final rev limiter which is going to be at your red line or just slightly past your red line and that's going to try and prevent uh you know excessive vibration uh float from occurring anything that could damage your engine if it were to exceed red line and so you've got two different uh set RPMs at which you're going to have these rev limiters and so that's what two-step is so you know lots of modern cars come with launch control these are all a form of a two-step rev limiter any modern car out there and it's becoming increasingly common which is a cool feature to have uh and so you know why do you need this at a lower RPM well for launch control when you are launching to get the op optimal launch you don't need all of that power you don't need to be all the way at 7,000 RPM or whatever your red line may be uh you're going to get away with lower uh RPM as far as not having those wheels just sit there and spin and so you know you want a little bit of slip but not too much and so that's generally going to occur at a lower RPM especially if it's a two- wheeel drive vehicle and so you'll set that first rev limiter something like 3,000 maybe 2,000 if it's rear wheel drive something like that depending on the engine all kinds of different characteristics uh but you're going to have that earlier RP M and that's purely going to be used for launch control and then once you're moving your only rev limiter is going to be that second one which will prevent your engine from getting damaged so how do these rev limiters work well there's really two major methods that you can use in order to create a rev limiter you can adjust the fuel or you can adjust the ignition and So speaking of adjusting the fuel this is more commonly used in OEM Solutions so cars that you buy from the dealer wherever uh they're going to be using these um because it's a safer thing to do and also because it's better for emissions so when you have a fuel adjustment uh there's two different ways this could work you could run a lean air fuel mixture so once you start to get uh to Red Line there and you want to stop uh the engine from increasing you can lean out the air fuel ratio and that's going to be less fuel which means you're going to make less power so it's going to prevent it it's going to start to slow it down from increasing in RPM then you can finally just shut off fuel completely and by shutting off fuel completely obviously it's not going to increase in RPM and you know you're going to sit there and you can adjust that so you inject fuel just to keep it enough to keep it at that set RPM so it'll be on off on off on off and you're going to be keeping it there at that set RPM now like I said the reason why this will be common for as an oem solution is because you're not going to be injecting fuel into the exhaust uh when you're not when you don't have the engine running so this is going to differ with ignition control so this is kind of an aftermarket solution uh which you may commonly see there are two different methods which you can use for ignition control you can cut ignition completely so you're killing your spark no spark of course in a gasoline engine you're not going to have uh any combustion occurring but you're going to be sending that fuel out your exhaust so as that fuel goes out the exhaust the exhaust is hot and mixes with oxygen once it leaves the exhaust crackles pops you know makes a little bang and that's why two-step can be associated with seeing you know Fire coming out the back of an exhaust that as well as the retarding method uh where it retards timing so another method to reduce the engine from increasing in RPM so while you have your piston coming up there's an ideal time that you want that spark to ignite so that you get the maximum amount of work useful work pushing that cylinder back down pushing that piston back down so when the Piston's on its way down if you the timing and ignite that spark later then you're not going to get all of that useful work and so the engine's not going to be able to continue to rev higher so you can the timing and in doing that your engine will just float there at that set RPM now this is where two-step rev limiters start to get confused with anti-ag systems two-step rev limiters by Design are not anti-ag systems but they operate in a very similar fashion and they can have that as a result of the way that they operate so you know there's two different ways we're going to look at this uh but basically when you're retarding the timing that means when your piston has reached bottom dead center you're still going to have a high amount of pressure and a high amount of temperature that's all that wasted work because you didn't optimize when you ignited that spark spark and so when you open your exhaust you're going to have this high pressure and high temperature uh gas that's going to move out and if you do have a turbocharged vehicle then that high pressure and high uh pressure high temperature high pressure gas is going to spool up that turbo and keep it spooled up and can act as an anti-ag system while you're sitting there you know keeping your engine at that rev limiter uh before you launch now if you heavily the timing meaning you know you're waiting really late to ignite that air fuel mixture uh so that you can keep the engine running but you don't want it to increase in whatever RPM you've set that rev limiter at well then when you open your exhaust you may still have combustion occurring so that air fuel mixture is still burning while it's going out and then it's going to be spooling up that turbo and then of course you know it can be spitting Flames out the exhaust things like that so this is how you know two-step rev limiters got associated with anti-ag systems and spitting Flames out the exhaust because if they do heavily the timing you can be sending combustion uh you can still have combustion occurring in your exhaust manifold and in your turbocharger so clearly you know you want to have a system that's built properly for it because you are going to be putting a huge strain on your exhaust system here uh which you typically wouldn't be doing uh by doing something like the fuel adjustment wouldn't be quite as harsh or if you were to not the timing too much uh so that you didn't have combustion occurring in the uh you know exhaust manifold and Beyond so thank you guys for watching and if you have any questions or comments feel feel free to leave them belowhello everyone and welcome in this video we're going to be talking about two-step rev limiters what they are and how they work now a two-step rev limiter very simply is just having two different stages of having a rev limiter so you're going to have one at a lower RPM and one at a higher RPM the lower one is typically going to be used for launch control so when the car is stationary and then you're going to have a second final rev limiter which is going to be at your red line or just slightly past your red line and that's going to try and prevent uh you know excessive vibration uh float from occurring anything that could damage your engine if it were to exceed red line and so you've got two different uh set RPMs at which you're going to have these rev limiters and so that's what two-step is so you know lots of modern cars come with launch control these are all a form of a two-step rev limiter any modern car out there and it's becoming increasingly common which is a cool feature to have uh and so you know why do you need this at a lower RPM well for launch control when you are launching to get the op optimal launch you don't need all of that power you don't need to be all the way at 7,000 RPM or whatever your red line may be uh you're going to get away with lower uh RPM as far as not having those wheels just sit there and spin and so you know you want a little bit of slip but not too much and so that's generally going to occur at a lower RPM especially if it's a two- wheeel drive vehicle and so you'll set that first rev limiter something like 3,000 maybe 2,000 if it's rear wheel drive something like that depending on the engine all kinds of different characteristics uh but you're going to have that earlier RP M and that's purely going to be used for launch control and then once you're moving your only rev limiter is going to be that second one which will prevent your engine from getting damaged so how do these rev limiters work well there's really two major methods that you can use in order to create a rev limiter you can adjust the fuel or you can adjust the ignition and So speaking of adjusting the fuel this is more commonly used in OEM Solutions so cars that you buy from the dealer wherever uh they're going to be using these um because it's a safer thing to do and also because it's better for emissions so when you have a fuel adjustment uh there's two different ways this could work you could run a lean air fuel mixture so once you start to get uh to Red Line there and you want to stop uh the engine from increasing you can lean out the air fuel ratio and that's going to be less fuel which means you're going to make less power so it's going to prevent it it's going to start to slow it down from increasing in RPM then you can finally just shut off fuel completely and by shutting off fuel completely obviously it's not going to increase in RPM and you know you're going to sit there and you can adjust that so you inject fuel just to keep it enough to keep it at that set RPM so it'll be on off on off on off and you're going to be keeping it there at that set RPM now like I said the reason why this will be common for as an oem solution is because you're not going to be injecting fuel into the exhaust uh when you're not when you don't have the engine running so this is going to differ with ignition control so this is kind of an aftermarket solution uh which you may commonly see there are two different methods which you can use for ignition control you can cut ignition completely so you're killing your spark no spark of course in a gasoline engine you're not going to have uh any combustion occurring but you're going to be sending that fuel out your exhaust so as that fuel goes out the exhaust the exhaust is hot and mixes with oxygen once it leaves the exhaust crackles pops you know makes a little bang and that's why two-step can be associated with seeing you know Fire coming out the back of an exhaust that as well as the retarding method uh where it retards timing so another method to reduce the engine from increasing in RPM so while you have your piston coming up there's an ideal time that you want that spark to ignite so that you get the maximum amount of work useful work pushing that cylinder back down pushing that piston back down so when the Piston's on its way down if you the timing and ignite that spark later then you're not going to get all of that useful work and so the engine's not going to be able to continue to rev higher so you can the timing and in doing that your engine will just float there at that set RPM now this is where two-step rev limiters start to get confused with anti-ag systems two-step rev limiters by Design are not anti-ag systems but they operate in a very similar fashion and they can have that as a result of the way that they operate so you know there's two different ways we're going to look at this uh but basically when you're retarding the timing that means when your piston has reached bottom dead center you're still going to have a high amount of pressure and a high amount of temperature that's all that wasted work because you didn't optimize when you ignited that spark spark and so when you open your exhaust you're going to have this high pressure and high temperature uh gas that's going to move out and if you do have a turbocharged vehicle then that high pressure and high uh pressure high temperature high pressure gas is going to spool up that turbo and keep it spooled up and can act as an anti-ag system while you're sitting there you know keeping your engine at that rev limiter uh before you launch now if you heavily the timing meaning you know you're waiting really late to ignite that air fuel mixture uh so that you can keep the engine running but you don't want it to increase in whatever RPM you've set that rev limiter at well then when you open your exhaust you may still have combustion occurring so that air fuel mixture is still burning while it's going out and then it's going to be spooling up that turbo and then of course you know it can be spitting Flames out the exhaust things like that so this is how you know two-step rev limiters got associated with anti-ag systems and spitting Flames out the exhaust because if they do heavily the timing you can be sending combustion uh you can still have combustion occurring in your exhaust manifold and in your turbocharger so clearly you know you want to have a system that's built properly for it because you are going to be putting a huge strain on your exhaust system here uh which you typically wouldn't be doing uh by doing something like the fuel adjustment wouldn't be quite as harsh or if you were to not the timing too much uh so that you didn't have combustion occurring in the uh you know exhaust manifold and Beyond so thank you guys for watching and if you have any questions or comments feel feel free to leave them below\n"