digital throttle control

[madmechanic]

Why?
How is the response time?

[DRAGON88]

RE: digital throttle control

Why? Because fly by wire has been around for years and has proven it's self to be worthy. Also you can have cruise control with a fly by wire unit without an extra servo. The whole industry is moving to FBW throttles, MC, Bu', SC, exc.

Response? About the same as a normal cable modern FBW throttles are much more responsive then their early models. I'd say that they could acctually be more accurate too...

[AbunDiga909]

RE: digital throttle control

Couldn't tell any difference at all when I drove the 220. If I didn't know about it, I wouldn't have thought anything. Seems to be working well... no complaints so far from anyone I've heard of...

[Mikeski]

RE: digital throttle control

Don't know more than I have read in different postings on this board. From what I understand they still use a cable which is attached to a position sensor instead of the throttle body. Then they have a servo connected to the throttle body. This allows the computer to make actual adjustments to the throttle body as well as the driver.

My opinion is that they should have eliminated the cable all together attaching the position sensor directly to the throttle handle, so I have a negative view of the system as a whole since it adds more components rather than reducing components. I believe the main point of DBY was to eliminate the need to have a cable connected to the motor thus making it easier to install the motors in cars/boats, plus enabling the computer to modulate the throttle body allowing it to reduce power for traction control, etc. In the long term it may prove beneficial for use with Perfect Pass systems, but I think the current system is somewhat of a gimmick.

[AWhite70]

RE: digital throttle control

FBY gives the engine computer (ECU) another degree of freedom to control engine response. With the previous cable throttle, throttle position is controlled by the driver. This controls the ammount of air allowed into the engine. The ECU then reacts to that throttle position by delivering a quantity of fuel to maintain the proper air/fuel ratio.

With FBY the throttle position is an input to the ECU from the driver that basically relays a need for more or less engine speed, power, or both. The ECU then decides what is the best way to deliver that power and has full control over air flow and fuel delivery. It gives greater capability for control over air fuel ratio.

Although for the most part gasoline engines run stoichiometric air/fuel ratios the A/F ratio can be adjusted slightly on either side of stoich to deliver better power (richer A/F say down to 12:1) or to deliver better fuel economy (leaner A/F). Having electronic throttle control allows for the best of both worlds

[skisix@38]

Re: RE: digital throttle control

Check your info...
What you have said is true for cars but not for boats. The exhaust temps in a boat run much cooler and are saturated by water so there is no way to tell what air/fuel ratio is running. The amount of fuel provided is determined by a set of fuel/throttle position/ambient pressure curves that are saved in the ECM.

And true, that by adding in a single cable to the system, all gains of the DBW are lost. MC has the servo mounted directly to the throttle body.

FBY gives the engine computer (ECU) another degree of freedom to control engine response. With the previous cable throttle, throttle position is controlled by the driver. This controls the ammount of air allowed into the engine. The ECU then reacts to that throttle position by delivering a quantity of fuel to maintain the proper air/fuel ratio.

With FBY the throttle position is an input to the ECU from the driver that basically relays a need for more or less engine speed, power, or both. The ECU then decides what is the best way to deliver that power and has full control over air flow and fuel delivery. It gives greater capability for control over air fuel ratio.

Although for the most part gasoline engines run stoichiometric air/fuel ratios the A/F ratio can be adjusted slightly on either side of stoich to deliver better power (richer A/F say down to 12:1) or to deliver better fuel economy (leaner A/F). Having electronic throttle control allows for the best of both worlds

[AWhite70]

What I said could most certainly be true for boats, whether or not they're used that way I don't know. I haven't seen what GM's code looks like.

Just because a marine engine doesn't measure A/F ratio via. an oxygen sensor doesn't mean it can't vary A/F ratio. It just means that it's not using closed loop feedback to control A/F. Air flow can be modeled from engine speed, throttle position, and Manifold Air Presure, and temperature. The ECU can vary fuel delivery through the injectors and thus vary A/F ratio. Depending on the rate of throttle change or fuel change the ECU can determine the best operating point.

True that fueling is controlled by sets of fuel/throttle position/pressure maps, but there can be multiple sets of maps that are used for various operating conditions.

I do engine calibration for a living I know what I'm talking about.

[ccskier16]

I believe you still need a cable to the transmission? I was looking at MC's at the boat show this week and at quick glance that is what I saw. Another trip to the show tomorrow and I'll check the big 3 out for this.

[skisix@38]

I'm not arguing with you and I'm not saying they couldn't pull off a closed loop system. The fact is none of them do. Without the closed loop system the engine is left to pre-determined maps to run from.

What I said could most certainly be true for boats, whether or not they're used that way I don't know. I haven't seen what GM's code looks like.

Just because a marine engine doesn't measure A/F ratio via. an oxygen sensor doesn't mean it can't vary A/F ratio. It just means that it's not using closed loop feedback to control A/F. Air flow can be modeled from engine speed, throttle position, and Manifold Air Presure, and temperature. The ECU can vary fuel delivery through the injectors and thus vary A/F ratio. Depending on the rate of throttle change or fuel change the ECU can determine the best operating point.

True that fueling is controlled by sets of fuel/throttle position/pressure maps, but there can be multiple sets of maps that are used for various operating conditions.

I do engine calibration for a living I know what I'm talking about.

[ag4ever]

How do you know there arn't multiple maps for different situations?

I am sure they could use the extra control, but how do we actually know if they are or are not unless they have released the info or are talking to a factory engineer who designs the stuff?

[2fat2ski]

Volvo/Penta is using O2 sensors in their manifolds. MerCruiser is experimenting with O2 sensors in there 8.1 liter motors, with there 555 ECM. Once one of the marine engine builders get this perfected, all of the manufacturers will use it. The tree huggers in California are really pushing to get the emissions lower on these motors.

The "pulsewith" of the injectors are controlled by the ECM, which get there inputs from various sensors on the motor. The most relied-on sensor is the MAP sensor, which tells the ECM of the load. The T.P. sensor also lets the ECM know what the demand on the motor is (WOT, steady cruise). The ECM will vary the pulsewidth according to the demand, or "load", keeping the engine running as close to the magic 14.7:1 ratio as possible. The adaptive strategy in the ECM is programmed in the RAM of the ECM and cannot be changed. It will run rich at start-up and the pulsewidth will taper off as engine temp raises. Obviously, the best way to monitor efficiency is through O2 sensors, which are most likely just a few years away. MerCruiser's ECM is already programmed for O2 sensors, but the pin's are not yet being used. My Diacom diagnostic software I use in marine engine driveability diagnosis has O2 sensor readout capabilities, but are not yet in use. Hopefully, PCM will get them in use soon and go to a closed-loop system.

[east tx skier]

I've driven a 2005 MC 197 with throttle by wire.

The why would, in my understanding, be geared toward speed control. True, MC had issues getting their system to work with PP (so many software revisions). But once they got it, it locks in on the set rpm value really fast compared to my older boat running PP DP 6.5 ng. We started out the opposite direction heading toward the turn island, and it engaged before we made it around. No overshooting. No hunting.

Installation of PP on these boats is a lot quicker. Very plug and play.

The down side. I've read some issues about the throttle being engaged by user error or rollers. This was not a problem when I was driving. But I didn't want to discount what some might have experienced.

My only complaint (and it's not really a complaint) was that you don't really feel the rpms in the palm of your hand like you do on older boats with traditional cable setups. It felt almost as if I was clicking "go" with the mouse. In a 350 hp boat, I ought to be able to feel it. I had no idea whether I was giving my skier sufficient juice or too much or what. Hopefully, the other boat makers (and MC when they revise theirs in the future) will incorporate a bit of feedback into the throttle lever for the driver.

Just my $.02.

[SGY]

I still don't understand why CC set their FBW system up they way they did. Can anyone explain CC's thought process.

[Laptom]

I'm with you SGY... In my opinion (and a bit technical point of view) it's a real strange setup.

[j2nh]

Anybody know if it is possible to retrofit an 05 ZR6 with throttle by wire? I know it would involve a new ECU but not what else would be involved.
Thanks
Jim