I hate drive by wire, my bmw has it, hate it
Drive by Wire
Started by
1987CR250R
, Jan 20 2012 06:02 PM
50 replies to this topic
Posted 06 February 2012 - 03:48 PM
Fbw is used on yamaha 1000cc sleds to control off throttle compression braking. It acts much like slipper clutch on bikes . You slam the throttle closed, fuel cuts off to kill power while the throttle plate stays open. Allows more coasting . When you open the throttle the throttle plate moves to position needed. 450's might benefit
I could feel the effect over the carb motors that didnt use it.
I could feel the effect over the carb motors that didnt use it.
Posted 06 February 2012 - 03:58 PM
highmarker, on 06 February 2012 - 03:48 PM, said:
Fbw is used on yamaha 1000cc sleds to control off throttle compression braking. It acts much like slipper clutch on bikes . You slam the throttle closed, fuel cuts off to kill power while the throttle plate stays open. Allows more coasting . When you open the throttle the throttle plate moves to position needed. 450's might benefit
I could feel the effect over the carb motors that didnt use it.
I could feel the effect over the carb motors that didnt use it.
Posted 06 February 2012 - 04:58 PM
true, I like it to on the 250F, and miss it riding twostrokes, too much on 450's why many run slipper clutches. Another preference thing. I don't like like a bunch of wires and complexity on bike's, but that wasn't the toipic
Another thing that is possible, and is done, Cam profile can be altered for better range of power. using the throttle plate position or rate of opening to keep velocity high, where the cam otherwise may have a flat power area. F1 leverages this tool. But in F1 electric servos can't move or react fast enough, so they've been using hydraulic to control the throttle plates more precisely.
just saying, there can more to it than just the twist grip.
Another thing that is possible, and is done, Cam profile can be altered for better range of power. using the throttle plate position or rate of opening to keep velocity high, where the cam otherwise may have a flat power area. F1 leverages this tool. But in F1 electric servos can't move or react fast enough, so they've been using hydraulic to control the throttle plates more precisely.
just saying, there can more to it than just the twist grip.
Posted 07 February 2012 - 05:53 AM
Lead Head, on 06 February 2012 - 03:04 PM, said:
Drive-by-wire does not in any way allow a race engine to make more power. A drive-by-wire throttle wide open is the same as a cable throttle wide open. Air flow is the same, fuel requirements are the same, and the only position where you can make peak power is WOT.
You do not need drive-by-wire to limit detonation because all modern bikes have a 3D programable spark advance system, and the EFI ones probably reference manifold pressure as well. There are two ways to control combustion pressure - throttle opening, and spark timing. Retard the timing and combustion pressures go down.
Most of the gains on modern vehicles are coming from variable valve timing, and far more precise fuel control from better air-flow sensors and wide-band oxygen sensors. Not drive-by-wire. Cams with lots of overlap make big power, but have poor low end torque, and quite poor emissions. Variable valve timing allows the use of very aggressive cam profiles, but during idle, low RPM, and cruise, they phase the camshaft timing apart to pretty much eliminate valve overlap, which grealy improves emissions. The main benifets of drive-by-wire are that it allows the computer much more control over engine power for things ilke traction control, and vehicle stability control, and during cruise it can cut the throttle blade opening slightly when the EGR opens, or the valve timing switches into EGR-like mode. I suspect it's mainly a traction and emissions thing in bikes as well.
Race engines were making 150HP/L well before the days of fuel injection, let alone drive-by-wire EFI. Even the carb'd 450s can be made to make 65HP at the wheel without too much effort, and still be quite rideable. That's 144HP/L from a single cylinder, carbureted engine.
You do not need drive-by-wire to limit detonation because all modern bikes have a 3D programable spark advance system, and the EFI ones probably reference manifold pressure as well. There are two ways to control combustion pressure - throttle opening, and spark timing. Retard the timing and combustion pressures go down.
Most of the gains on modern vehicles are coming from variable valve timing, and far more precise fuel control from better air-flow sensors and wide-band oxygen sensors. Not drive-by-wire. Cams with lots of overlap make big power, but have poor low end torque, and quite poor emissions. Variable valve timing allows the use of very aggressive cam profiles, but during idle, low RPM, and cruise, they phase the camshaft timing apart to pretty much eliminate valve overlap, which grealy improves emissions. The main benifets of drive-by-wire are that it allows the computer much more control over engine power for things ilke traction control, and vehicle stability control, and during cruise it can cut the throttle blade opening slightly when the EGR opens, or the valve timing switches into EGR-like mode. I suspect it's mainly a traction and emissions thing in bikes as well.
Race engines were making 150HP/L well before the days of fuel injection, let alone drive-by-wire EFI. Even the carb'd 450s can be made to make 65HP at the wheel without too much effort, and still be quite rideable. That's 144HP/L from a single cylinder, carbureted engine.
not hard at all to make 43hp from a 250F, that's 172 hp/l from a single cylinder carbied engine.
Posted 07 February 2012 - 05:02 PM
Throttle-by-wire is only as good as the programming in the ECU.Our UPS trucks have it and in that iteration it stinks, the throttle frequently does something different than what your foot is doing.
Posted 07 February 2012 - 05:15 PM
highmarker, on 06 February 2012 - 04:58 PM, said:
true, I like it to on the 250F, and miss it riding twostrokes, too much on 450's why many run slipper clutches. Another preference thing. I don't like like a bunch of wires and complexity on bike's, but that wasn't the toipic
Another thing that is possible, and is done, Cam profile can be altered for better range of power. using the throttle plate position or rate of opening to keep velocity high, where the cam otherwise may have a flat power area. F1 leverages this tool. But in F1 electric servos can't move or react fast enough, so they've been using hydraulic to control the throttle plates more precisely.
just saying, there can more to it than just the twist grip.
Another thing that is possible, and is done, Cam profile can be altered for better range of power. using the throttle plate position or rate of opening to keep velocity high, where the cam otherwise may have a flat power area. F1 leverages this tool. But in F1 electric servos can't move or react fast enough, so they've been using hydraulic to control the throttle plates more precisely.
just saying, there can more to it than just the twist grip.
bmw's new engines do not use the throttle body at all, everything is done by the valvetronic system, the throttle body goes to full open once the car is started up and stays full open
Posted 08 February 2012 - 09:23 AM
Before anybody goes nuts over that, it should be mentioned that those are direct injection engines.
Posted 08 February 2012 - 05:23 PM
servo controlled throttle plates CAN allow an engine to make more power, by virtue of allowing bigger throttle body intake diameters and/or more radical cam timing while still maintaining good power at partial throttle setting
In addtion to electronic engine management and better heads and lower friction pistons and valve train. Catalytic converters have also made modern engine's more powerful. They have allowed cam timing and overlap to be used that before wouldn't have been able to meet emissions. Even modern superbikes took a jump in hp when they started using catalyst.
some of these new cars rated at say 400hp, will only make that power for a short time. Hook a trailer up and go over a steep pass. Your 400hp truck at the bottom of the hill won't be at the top when the engine management starts taking timing out and pouring more fuel in to cool the piston...
In addtion to electronic engine management and better heads and lower friction pistons and valve train. Catalytic converters have also made modern engine's more powerful. They have allowed cam timing and overlap to be used that before wouldn't have been able to meet emissions. Even modern superbikes took a jump in hp when they started using catalyst.
some of these new cars rated at say 400hp, will only make that power for a short time. Hook a trailer up and go over a steep pass. Your 400hp truck at the bottom of the hill won't be at the top when the engine management starts taking timing out and pouring more fuel in to cool the piston...
Posted 16 February 2012 - 06:27 PM
the biggest advantages of drive by wire are fuel economy and emissions. seeing as how 2 smokers were bascially phased out because of emissions, it is a possibility. unfortunately, i dont think a simple stator or even the systems on fi dirt bikes can make enough power to run an electronic throttle body. street bikes can compensate by using a battery and healthy charging system. since weight is a factor, dirt bikes may not see them. if they do, i hope they have some failsafes in the programming so they dont end up like some of the newer harleys.
Posted 16 February 2012 - 09:39 PM
grayracer513, on 03 February 2012 - 02:20 PM, said:
In response to a "throttle chop" input at the gas pedal, the system reacts by cutting fuel, but "rolling" the throttle closed, so air follows the fuel through and out.
Does that affect response, though? I am hardly a professional rider/driver and I think that a quick roll off the throttle feels substantially different from chopping it altogether(and a chop input resulting in a roll-off response would feel weird). That's why I mentioned response and GDI (gasoline direct injection) since there is no port wall wetting with GDI. To be fair, though, I do not know how fast fuel evacuates an intake port upon throttle close, TBW or not.
highmarker, on 08 February 2012 - 05:23 PM, said:
servo controlled throttle plates CAN allow an engine to make more power, by virtue of allowing bigger throttle body intake diameters and/or more radical cam timing while still maintaining good power at partial throttle setting
More power how....and where? The optimum size of a throttle valve isn't dependent on whether a human or machine controls the opening of it.
Posted 17 February 2012 - 03:22 AM
HeadTrauma, on 16 February 2012 - 09:39 PM, said:
Does that affect response, though? I am hardly a professional rider/driver and I think that a quick roll off the throttle feels substantially different from chopping it altogether(and a chop input resulting in a roll-off response would feel weird). That's why I mentioned response and GDI (gasoline direct injection) since there is no port wall wetting with GDI. To be fair, though, I do not know how fast fuel evacuates an intake port upon throttle close, TBW or not.
More power how....and where? The optimum size of a throttle valve isn't dependent on whether a human or machine controls the opening of it.
More power how....and where? The optimum size of a throttle valve isn't dependent on whether a human or machine controls the opening of it.
yes, it definitely does on bmw's, I had to change how I clutch, if I clutch fast like my M3 the transmission still has power going to it, even though I have my foot off the gas, it's f'in irritating, I had to slow down my shifting
Posted 17 February 2012 - 08:13 AM
HeadTrauma, on 16 February 2012 - 09:39 PM, said:
Does that affect response, though? I am hardly a professional rider/driver and I think that a quick roll off the throttle feels substantially different from chopping it altogether(and a chop input resulting in a roll-off response would feel weird). That's why I mentioned response and GDI (gasoline direct injection) since there is no port wall wetting with GDI. To be fair, though, I do not know how fast fuel evacuates an intake port upon throttle close, TBW or not.
It depends on how it's set up. The BMW in the example above is apparently trying to emulate the "dashpot" effect that was used long ago with carbureted cars to eliminate the unburned rich mixture dump on throttle chop. In that case, it was just a simple damper on the linkage that physically kept the throttle from snapping shut quickly. My Accord (port EFI) does the same kind of thing, but it's managed by the idle air control stepping motor.
But with either port EFI or GDI, if the fuel is cut instantly on a chop, the car will behave as if the throttle was chopped, whether the plates actually close or not.
At 1500 RPM, it takes 80 ms to complete a whole cycle, so you'd have to figure that any trailing intake charge would be out the back by that time.
HeadTrauma, on 16 February 2012 - 09:39 PM, said:
More power how....and where? The optimum size of a throttle valve isn't dependent on whether a human or machine controls the opening of it.
Posted 17 February 2012 - 03:12 PM
More power by virtue of bigger cam timing and bigger throttle aperture at wfo, WITHOUT as much loss in power at partial throttle settings. DBW won't MAKE more wfo power, but will ALLOW more wfo power to be made with less compromise in other throttle position,
Even though fuel is injected it is still important to maintain port filling and velocity. example, the too big TB on the crf250, which honda later reduced in size for better power under wfo. If they had DBW they could have left it big and modulated the throttle plate control.
FWIW, I don't want this crap on my dirtbike, but it is possible to use the technology.
and yes shutting the fuel down and leaving the throttle plate open can and is used (in sleds) to tune compression braking. Don't believe it. try hitting your kill switch (same effect as shutting the fuel off) with the throttle held open, vs. closed.
Even though fuel is injected it is still important to maintain port filling and velocity. example, the too big TB on the crf250, which honda later reduced in size for better power under wfo. If they had DBW they could have left it big and modulated the throttle plate control.
FWIW, I don't want this crap on my dirtbike, but it is possible to use the technology.
and yes shutting the fuel down and leaving the throttle plate open can and is used (in sleds) to tune compression braking. Don't believe it. try hitting your kill switch (same effect as shutting the fuel off) with the throttle held open, vs. closed.
Posted 17 February 2012 - 04:38 PM
With regard to the matter of cylinder filling, let me ask a simple, totally off the wall question that will illustrate the point: How will the cylinder fill with air more readily; with a relatively small port, a relatively large port, or with the head removed?
Air velocity beyond mean piston speed is a product of the restrictions of engine design related to valves and/or ports, and in the case of carbs and normally aspirated two-strokes, the need to have air transport fuel mist over some distance. Holley carburetor tuning manuals point out that the ideal carb size is the smallest one that will produce a WOT intake manifold vacuum of zero measured just below the carb at peak torque speed. Think about it.
Air velocity beyond mean piston speed is a product of the restrictions of engine design related to valves and/or ports, and in the case of carbs and normally aspirated two-strokes, the need to have air transport fuel mist over some distance. Holley carburetor tuning manuals point out that the ideal carb size is the smallest one that will produce a WOT intake manifold vacuum of zero measured just below the carb at peak torque speed. Think about it.
Posted 17 February 2012 - 06:17 PM
D. a correctly sized port.
As the intake port is flowing and the valve slams shut there is still incoming momentum that can pressurize the charge in the port for a split second. If you time the valve back off the seat during this pressure you can realize a small supercharging effect. Kawasaki was the 1st I remember to really try to leverage the effect in production bikes (sportbikes)
Point being, too big or too small wouldn't be ideal. But really depends on the what the engine is being used for? also in 1 TB per cyl it becomes part of the port taper, which has it's own effects.
As the intake port is flowing and the valve slams shut there is still incoming momentum that can pressurize the charge in the port for a split second. If you time the valve back off the seat during this pressure you can realize a small supercharging effect. Kawasaki was the 1st I remember to really try to leverage the effect in production bikes (sportbikes)
Point being, too big or too small wouldn't be ideal. But really depends on the what the engine is being used for? also in 1 TB per cyl it becomes part of the port taper, which has it's own effects.
Edited by highmarker, 17 February 2012 - 06:23 PM.
Posted 18 February 2012 - 08:07 AM
think VVT benefits heavier vehicle like cars and trucks more than light dirt bikes. VVT on big street bikes (VFR) wasn't worth the complication IMO. But who knows someone might do it? emissions could also drive it's use someday
Posted 20 February 2012 - 06:25 PM
i cam from a car racing back ground its drive by wire makes it feel like your in a video game the car doesnt eally give u any feedback apart from the nissan gtr but thats another topic it would be interesting to see them have it on bikes.
Posted 20 February 2012 - 08:14 PM
highmarker, on 18 February 2012 - 08:07 AM, said:
But who knows someone might do it? emissions could also drive it's use someday
Absolutely. Emissions have pushed all of the recent engine development. 400 horsepower daily driver sedans and pickups are simply a result. The engine management was required for emissions but once it was in place the big horsepower numbers were only a few keyboard strokes away.
