What are the reasons for fly-by-wire throttle?
08-14-2006, 06:57 PM
#1
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What are the reasons for fly-by-wire throttle?
Alot of cars, including the RX-8, have fly-by-wire throttle. What are the reason for having such a feature?
Pros and cons?
Pros and cons?
08-14-2006, 07:09 PM
#3
It allows the PCM to control the throttle opening for maximum effect. Just because you want to go faster...doesn't mean the throttle butterfly needs to be fully open. In fact for some loads/flow levels it is better to have less than full opening at WOT.
The problem is they don't necessarily use maximum performance for the parameters that they choose.....the damn emissions thing tends to get way more than its fair share of consideration
The problem is they don't necessarily use maximum performance for the parameters that they choose.....the damn emissions thing tends to get way more than its fair share of consideration
08-15-2006, 12:41 AM
#7
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Wot....
Dannobre makes a good point about the partial throttle being faster than WOT sometimes- my old RX-3 was modded so that the secondary venturies in the little four barrel carb would flap wide open, instead of being vacuum actuated "as needed".
If you slammed the pedal down at low revs, the intake velocity would drop right off and the car would bog down, even stall if done right!
Another thing I've noticed on my '8 is that 90% throttle is often faster than 100%. This is evident at high revs and high speeds, if I back off the gas, the car will actually give a little surge forward, when it was losing momentum at 100%. Go figure.
S
If you slammed the pedal down at low revs, the intake velocity would drop right off and the car would bog down, even stall if done right!
Another thing I've noticed on my '8 is that 90% throttle is often faster than 100%. This is evident at high revs and high speeds, if I back off the gas, the car will actually give a little surge forward, when it was losing momentum at 100%. Go figure.
S
08-15-2006, 11:43 AM
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First of all F1 cars have it too (they would definitely not have it if it would slow anything down).
With fly by wire throttle the engine management has much better control over the engine, for instance, it can better control the amount of exhaust gases going back into the engine in order to increase mileage (reduce pumping losses) and reduce emissions. There's no reason, for the driver to control the airflow. The driver only needs to tell engine management how much power is needed.
Some decades ago, the driver did not just control the airflow directly, he or she did also controlled timing of ignition. You could also ask why can't we control timing anymore.
With fly by wire throttle the engine management has much better control over the engine, for instance, it can better control the amount of exhaust gases going back into the engine in order to increase mileage (reduce pumping losses) and reduce emissions. There's no reason, for the driver to control the airflow. The driver only needs to tell engine management how much power is needed.
Some decades ago, the driver did not just control the airflow directly, he or she did also controlled timing of ignition. You could also ask why can't we control timing anymore.
08-15-2006, 12:19 PM
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Throttle by wire allows for the Honda Civic to have inverse half vtec.
Without it the mileage/driveability suffers, the automatic (base) is rated at 30/40, the manual shift transmission is less.
Without it the mileage/driveability suffers, the automatic (base) is rated at 30/40, the manual shift transmission is less.
08-15-2006, 01:46 PM
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One other advantage to Throttle By Wire is the packaging aspect. Much easier to place a stepper-motor throttle positioning unit on the throttle body and run some wires to it, than to have to bend/thread/plan for a throttle cable assembly.
With the placement of some of todays throttle bodies, substantial underhood space is used to route a throttle cable (and, throttle cables are just danged ugly).
With the placement of some of todays throttle bodies, substantial underhood space is used to route a throttle cable (and, throttle cables are just danged ugly).
08-15-2006, 01:59 PM
#13
Originally Posted by mysql101
I don't doubt that there are advantages to it, but as I said, there is a noticable delay between throttle input and the car responding.
08-15-2006, 08:06 PM
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Originally Posted by MazdaManiac
Its actually faster and smoother than a cable in most circumstances.
They've been doing that for years in the exotics. Get used to it.
The butt is not a dyno.
Consensus is not science.
They've been doing that for years in the exotics. Get used to it.
The butt is not a dyno.
Consensus is not science.
Doesn't matter if the butt is not a dyno. It's the only instrument for measurement that really matters.
08-15-2006, 08:25 PM
#17
Just for your information, the throttle-by-wire system in the 06 civic SI sucks *** in 1-2 gears at crawling speeds. It's an uncontrollable bucking bronco of a ride. Maybe if I had more seat time, I could figure it out, but damn, you breath on the gas pedal and you're lucky to hang on for 8 seconds.
08-15-2006, 09:09 PM
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Originally Posted by MazdaManiac
Its actually faster and smoother than a cable in most circumstances.
They've been doing that for years in the exotics. Get used to it.
They've been doing that for years in the exotics. Get used to it.
08-16-2006, 12:08 AM
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Ok. But to me what I feel is more important than what a machine tells me I should feel.
When it comes down to it its all about what you feel behind the wheel, not numbers on a sheet of paper or computer screen.
When it comes down to it its all about what you feel behind the wheel, not numbers on a sheet of paper or computer screen.
08-16-2006, 02:17 AM
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Drive-by-wire is also used by car manufacturers as warranty insurance.
They sell a car that comes with say....a three year unlimited mileage warranty. Said car is supplied with say....a high horsepower engine. Now if Johnny Leadfoot were to buy this car, as sure as God made little girls, he'd cane the living daylights out of the thing. That's what it's designed for, right? Why put a high hp engine in a car unless you expect it to be purchased by someone who likes to fry rubber?
To make good money on a car sale, the manufacturer needs to sell the car and not have it return next week with a broken diff. Johnny will be happy too, he gets to impress the girls down at the mall with his clouds of smoke for months on end. To keep Johnny and the company accountants happy, the engineers put DBW in Johnnys ride. This way, they can control how many horses reach the rear wheels when Johnny sinks the slipper. No massive torque application.....let's dampen it down a tad so we can still spin the wheels, but do it without a big hp spike when the pedal kisses the carpet.
Everyone wins. This is why manufacturers love DBW in performance cars. The trade off is a tenth or two over 1320ft.
Cheers.
They sell a car that comes with say....a three year unlimited mileage warranty. Said car is supplied with say....a high horsepower engine. Now if Johnny Leadfoot were to buy this car, as sure as God made little girls, he'd cane the living daylights out of the thing. That's what it's designed for, right? Why put a high hp engine in a car unless you expect it to be purchased by someone who likes to fry rubber?
To make good money on a car sale, the manufacturer needs to sell the car and not have it return next week with a broken diff. Johnny will be happy too, he gets to impress the girls down at the mall with his clouds of smoke for months on end. To keep Johnny and the company accountants happy, the engineers put DBW in Johnnys ride. This way, they can control how many horses reach the rear wheels when Johnny sinks the slipper. No massive torque application.....let's dampen it down a tad so we can still spin the wheels, but do it without a big hp spike when the pedal kisses the carpet.
Everyone wins. This is why manufacturers love DBW in performance cars. The trade off is a tenth or two over 1320ft.
Cheers.
08-16-2006, 02:29 AM
#23
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Originally Posted by mysql101
I don't doubt that there are advantages to it, but as I said, there is a noticable delay between throttle input and the car responding.
08-16-2006, 08:24 AM
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Originally Posted by mysql101
I've already had my *** handed back to me on that comment, thanks for the extra kick 
It's MM's *** I'm kicking....not yours!