The Big Problem With Modern Manual Transmissions - Rev Hang

Hello everyone and welcome to this video sponsored by Advance Auto Parts. We are looking at the differences between mechanical throttle bodies and electronic throttle bodies. Let's discuss why electronic throttle bodies lead to a common

problem

with

modern

manual

transmissions

. Rev Hang, so first. Let's define everything we are discussing. This is a mechanical throttle body and is directly linked to the driver through the accelerator pedal, so when you press that accelerator pedal, it forces a cable to turn the throttle valve to allow more air to pass through. into the engine as more air enters the engine, more fuel is injected and more power is generated, so the driver directly controls how much airflow the engine receives.

An electronic throttle eliminates that direct link between the driver and the accelerator, so now when you press the accelerator pedal, a position sensor tells a controller that tells an electric motor how much to open this throttle valve; However, you can listen to other inputs and choose the exact amount you want to open, you don't have to directly listen to exactly what the driver tells you to do and eventually suspend revs, making shifts and

manual

transmissions

sluggish. and choppy. Rev

hang

ing is caused by electronic throttles, not heavy steering wheels that slowly close when the driver lifts their foot off the accelerator pedal, so once you go into upshifts, the revs stay high and slow.

They start to come down, so once you release the clutch, drop those revs and shake the car. Now many thanks to Advance Auto Parts for sending parts for this video demonstration. You can use the advanced system. auto parts mobile app for your parking needs, so how do we get from here to here? Despite what many enthusiasts will say about electronic throttles, they actually offer quite a few advantages. Yes, mechanical throttles will give you the best direct throttle response. valve and is a simple system and basically eliminates Rev Hang, which will be the main focus of this video.

All things great, however, electronically controlled throttles come with many benefits and you might be surprised to know that one of them is actually better pedal feel. In the world, can electronic throttle improve feel compared to a purely mechanical system that is literally attached to your foot? Something you may have noticed if you've driven cars with mechanical throttle bodies is that what you press on that accelerator pedal doesn't necessarily correlate linearly. With the amount of torque you end up getting, why? Look at what's happening with the throttle body, let's say the throttle valve is fully closed and then you open it ten percent, that's a massive percentage increase in the amount of airflow. you were allowing to go from zero to ten percent and then when you open from ten percent to 20 percent, that's a hundred percent increase and how open that throttle position is, now you're allowing a lot of air.

You'll see a good increase in torque very quickly, but then as you open it up more and more, from twenty to thirty percent, just a fifty percent increase, from forty percent open to fifty percent open, just a increase of twenty-five percent, finally passing ninety percent. to open one hundred percent, open the throttle valve all the way, just an 11 percent increase in that actual space that you're allowing airflow to go through, so what does this mean if you look at a graph of torque versus throttle position with a mechanical throttle? You will see that the torque increases very quickly at first as you press the accelerator pedal and then slowly and decreases as you get closer to one hundred percent.

With an electronic throttle body, you can make the torque versus throttle position curve look however you want. you want so you can have a linear correlation between how much you pressed the accelerator pedal and how much torque you actually get from your engine, how does it do it so well? It just opens the throttle less than you asked, so if you give it 25 percent throttle, with a mechanical throttle you could get 50% of your torque, compared to an electronic throttle, it will say okay, they they want 25% of your torque because they lowered the throttle position to 25%, so it's going to limit how much you actually open this throttle valve so that you get exactly 25% torque instead of what you would mechanically based on how much you've pushed. the accelerator pedal, the other thing you need to take into account is the engine rpm etc. think about an engine at 2000 rpm vs 6000 rpm, well if it spins three times as fast it needs three times as much air then what that means is that you most likely don't need to rev fully at low rpm to get maximum torque, so if you look at a torque versus throttle position curve here and in our example we're just going to say that at 2000 rpm you only need 25 percent of that throttle position opening to get maximum torque because you don't have as much input. airflow and therefore with a mechanical system you will reach that maximum torque at 25 percent of pressing the accelerator pedal and then you will have 75 percent of that zone where it doesn't matter where your food is. that accelerator pedal, it doesn't make any difference in the amount of torque you're getting compared to an electronic throttle that you can adjust for different rpm, so if you're at 2,000 rpm you can flatten it out so that actually wherever your foot is on That accelerator pedal actually correlates to that percentage of torque, which will be very intuitive for the driver, but that's just one of many advantages.

Electronic throttles can provide better cruise control adjustment. They can allow smoother shifting with automatic transmissions. They can improve how quickly catalytic converters heat up. By controlling the balance of air-fuel ratios and throttle position, they can improve throttle control during cylinder deactivation, can eliminate jerky driving and manual transmission vehicles, and can provide safety features such as improvements to the stability control, traction control and throttle input reduction if the brake pedal is depressed there is a long list of benefits and just one of those many benefits is how the -zz electronic throttle can improve emissions, so how Electronic throttle bodies lead to better emissions and how does this lead to lower revs?

So I found a study from the 1990s details this process, so the important thing is to know that the catalytic converters used to improve your car's emissions are effective in a narrow air-fuel ratio range, so the amount of air and fuel entering your cylinders at that ratio is very important to controlling emissions and your catalytic converter is very sensitive to that ratio, so according to this study, if your engine is running at a rich ratio air and fuel, you will have a lot of carbon monoxide and hydrocarbon emissions coming out of that catalytic converter. and likewise, if you're running your engine on an air-fuel ratio, you're going to see a lot of nitrogen oxide emissions coming out of that catalytic converter, so it's absolutely critical that you properly control the air-fuel ratio, So what is the scenario? where it's difficult to control the air-fuel ratio, the throttle zooms in and out, so zooming in is when the throttle is closed and then you open it up very quickly.

Takeoff is when the throttle is open and then you close it very quickly. So if you look at what happens in an engine in these scenarios, you can see why the air-fuel ratio c

hang

es so that with the tip of the throttle valve you close it and then you open it and when you open it, a burst comes out. of air. on that engine and depending on the engine's ability to time fuel injection initially, you will have a lot of air in that cylinder and not enough fuel to make up for it, so you will see a lean peak and then a tip out.

What you're going to do is close the throttle valve to shut off the air, but you're still injecting fuel, so now you have a peak of fuel-rich air in the air-fuel ratio, so the challenge here is you want to maintain a sort of flat line here of that air-fuel ratio instead of these big variations that you see to keep it out of these regions where emissions will be low goes into the electronic throttle valve, so this is where we can finally understand why it exists Rev Hang. Looking at the results of this study comparing a mechanical throttle body in red to an electronic throttle body in blue here, we looked at throttle position, air-fuel ratio, and hydrocarbon emissions and what they noticed during a shift.

March. What we are looking at here is a gear change, so we are on the accelerator, we release the accelerator, we press the clutch and then completely release the accelerator, then you change to the next gear, you released the clutch, you go back to the Accelerate and there you can see that you're back on the throttle and what you noticed happens with the mechanical throttle body is that during that gear change, when you have that top-end scenario, you have a rich air-fuel mixture and that air-fuel mixture . When rich, there is an increase in hydrocarbon emissions and this is what they are looking to control using this electronic throttle body.

What they do is two things: First, they cut off the fuel, but there is still some fuel left once you close the throttle valve. Instead of closing it very quickly, it delays closing the throttle valve to burn the remaining fuel, and in doing so, that means the engine rpm drops slowly, so it cuts off the fuel. It slows down the throttle but keeps the air-fuel ratio at a low point. it actually reduces the fuel, so here you see that the peak is very lean, but you're just not injecting fuel, but you're keeping that basically flat line of air-fuel ratio outside of that and by doing so, by delaying the throttle closure, no If you ever produce that rich mixture and by doing so, you don't produce these hydrocarbons, so the benefit is that now the hydrocarbon emissions have been reduced.

One of the interesting things about this study is that they didn't actually see an improvement. using the electronic throttle on nitrogen oxide emissions, however, the important thing was that they wanted to be able to control the air-fuel ratio to control the emissions and in doing so, using that electronic throttle and delaying the throttle closure means that you will have that acceleration. This occurs when the rpm does not drop quickly when changing gears. Obviously, current engines are much more advanced than those used in testing in this study in the 1990s, so current engines can change parameters much more quickly and have much more computational power, however, the

problem

of rev drop still exists and one of the unique challenges that still exists with

modern

transmissions, modern vehicles with a manual transmission is when they are combined with engines that use port injection, so what happens is a process where you have a wedding on the wall. for example, let's say you are shifting gears and you release the throttle to shift gears and when the throttle closes there is still some fuel left on the walls of that intake port and so even though the fuel has been cut off immediately , that fuel ignites. the intake port will still make its way into the engine and since there is no air coming in it will have a rich air fuel mixture and still have those hydrocarbon emissions so if you delay closing the throttle which of course causes Reb hangs You can burn off the remaining fuel that is trapped in the walls of the intake port as it makes its way to the engine.

Now, of course, direct injection won't have this problem because it doesn't inject into those. The intake port walls are injected directly into the cylinder and that doesn't necessarily mean that direct injection engines have no revs. There are still reasons why it may exist, but between my two personal vehicles, my Subaru Crosstrek and my Mazda MX-5, which has direct injection the Subaru Crosstrek which has port injection has significantly more revs, so big thanks to advanced auto parts for sponsoring the video, of course, check out the link in the video description and check out their mobile app if you have any questions or comments, of course. feel free to leave the ones below thanks for watching