Question on AWD

[Kelly Padfield]

On these cars everything I've read says the the rear clutch clicks in if the car see wheel spin on the front. So does this mean when you launch the car with traction control turned off its only launching in FWD. Then if it sees wheel spin it will lock in the Rear clutch? Or is there something for when launching in sport mode with traction control off it temporarily locks in the rear clutch?

Just curious because I was chatting with a friend of mine that has a '12 (mine is a '14) and he doesnt like the way these cars launch. Says his likes to slip for a bit till the rear clutch kicks in and it kinda jerks the car (I have yet to ride in his car to confirm this). But when I launch mine I've never noticed this. As of right now we are both tuned with 3 bar and mine has the ngk plugs and 170 thermo.

 

[brucelinc]

Launching with traction control off does NOT mean launching in FWD. Heavy throttle application will send some power to the rear whether the front loses traction or not. Your friend's description of slip until the clutch kicks in causing the car to **** doesn't really make any sense. My understanding is that there is a limit to the amount of torque that the rear will handle so with an aggressively tuned car, it is possible to have more front wheel spin without much rear wheel spin but there is still all the power going to the rear that it can handle.

http://wardsauto.com/technology/demand-growing-ford-s-intelligent-all-wheel-drive-system

The auto maker’s advanced system features software that preemptively reassesses road conditions 20 times faster than the blink of an eye, readjusting the power split between the wheels for an ideal blend of handling and traction.
Using a combination of software and sensors, the new system gathers data from 25 external signals, including wheel speed, accelerator pedal position and steering-wheel angle.

“We’re using AWD for more than just traction, we’re using it to improve handling for a competitive advantage over those who aren’t using AWD that way,” says Joe Torres, senior AWD engineer.

 

[Kelly Padfield]

This is what I figured. Now just for curiosity sake could one wire up a switch with a 5v reference to engage the rear clutch or would there be any be if it for this? I assume most things on the car run off 5v reference.

 

[SilverSH0]

This is what I figured. Now just for curiosity sake could one wire up a switch with a 5v reference to engage the rear clutch or would there be any be if it for this? I assume most things on the car run off 5v reference.

I would assume the rear clutches have modulated pulses. I have no specific information on this at all. Just assuming since most modern electronics on cars are no longer simple voltages.

 

[EcoBoostSHO]

I believe it is actually current modulated. I question why you would want to? All you have to do in a 13+ is power brake it a bit and it will start locking up the clutch for you. Since the car is FWD biased and driven off the tranny I believe that limits that max power it can send to the rear as it is and the "weak" point doesn't seem to be the lockup clutch. It might make for an interesting experiment, but I don't think you'll see any gains at the track with it and it wouldn't be a good idea to keep it locked up all the time for general driving or it might overheat?

 

[mrhighcaliber]

A few months back, I raced a "friendly" looking 2012 BMW 535ix. He had been trying to race my SHO for a while, I was one of the fastest on the street. Soo much hype on the internet for this race from everyone on the street scene. So we raced. My SHO got stomped off the line! 3 cars on me almost instantly. I held him to that 3 car lead the end of the quarter. That BMW boost launches so violently that it looks as though the front wheels are going lift. Lost 100bucks but I gained lots of insight to what true awd is. I began researching our awd system. This was months ago but If I remember correctly, that pwm signal is 12v 100%duty @ the connector. (Don't quote me.lol) Not 5v. Mind you I tested this at work on a 2017mkx, but same rdu design no less. Now boost launching my sho, I graphed the rdu duty signal and this signal will NEVER reach over about 80% until after the vehicle begins moving. Which if launched @ 2200rpm or more, causes front wheel slippage, then 95-100% rdu duty cycle occurs. By then its too late, the system is now acting reactivity, trying to stop the slippage thats occuring and the tuned BMW with secretly upgraded fuel pump and 60% e85 tune that secretly runs 12.3's is 3 car lengths ahead with your 100bucks. Now my propsed solution is not drag radials on the front, but a small regulated booster box that will be wired in series with the rdu signal harness that provides 2.5~volts DC to boost the pwm signal voltage to what would be a full lock signal on launch, while still allowing the pcm to control the rdu. This also would in theory, allow us to launch at higher rpms. The down side to defeating this electronic drivetrain 'failsafe' is that we would be increasing drive line stress on everything from the ptu to rear half shafts. Things that were not designed for drag launching a 4300lb vehicle.

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[SHOdded]

Besides the system wasn't designed for splitting more than 365 hp to the rear wheels ... or was it To date, no one has come up with a number for the power the RDU (and hopefully the driveshaft) can handle.

 

[Kelly Padfield]

A few months back, I raced a "friendly" looking 2012 BMW 535ix. He had been trying to race my SHO for a while, I was one of the fastest on the street. Soo much hype on the internet for this race from everyone on the street scene. So we raced. My SHO got stomped off the line! 3 cars on me almost instantly. I held him to that 3 car lead the end of the quarter. That BMW boost launches so violently that it looks as though the front wheels are going lift. Lost 100bucks but I gained lots of insight to what true awd is. I began researching our awd system. This was months ago but If I remember correctly, that pwm signal is 12v 100%duty @ the connector. (Don't quote me.lol) Not 5v. Mind you I tested this at work on a 2017mkx, but same rdu design no less. Now boost launching my sho, I graphed the rdu duty signal and this signal will NEVER reach over about 80% until after the vehicle begins moving. Which if launched @ 2200rpm or more, causes front wheel slippage, then 95-100% rdu duty cycle occurs. By then its too late, the system is now acting reactivity, trying to stop the slippage thats occuring and the tuned BMW with secretly upgraded fuel pump and 60% e85 tune that secretly runs 12.3's is 3 car lengths ahead with your 100bucks. Now my propsed solution is not drag radials on the front, but a small regulated booster box that will be wired in series with the rdu signal harness that provides 2.5~volts DC to boost the pwm signal voltage to what would be a full lock signal on launch, while still allowing the pcm to control the rdu. This also would in theory, allow us to launch at higher rpms. The down side to defeating this electronic drivetrain 'failsafe' is that we would be increasing drive line stress on everything from the ptu to rear half shafts. Things that were not designed for drag launching a 4300lb vehicle.

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Wow, great information. Maybe something to play with if one has free time on a rainy day or someone decides to come up with stronger driveline components if the need is ever there in the future.

 

[bpd1151]

Wow, great information. Maybe something to play with if one has free time on a rainy day or someone decides to come up with stronger driveline components if the need is ever there in the future.

Oh the need is there.

Although that crowd of people who "need" them is monumentally small.

The few who do "need" them, are ever hopeful.

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[EcoBoostSHO]

A few months back, I raced a "friendly" looking 2012 BMW 535ix. He had been trying to race my SHO for a while, I was one of the fastest on the street. Soo much hype on the internet for this race from everyone on the street scene. So we raced. My SHO got stomped off the line! 3 cars on me almost instantly. I held him to that 3 car lead the end of the quarter. That BMW boost launches so violently that it looks as though the front wheels are going lift. Lost 100bucks but I gained lots of insight to what true awd is. I began researching our awd system. This was months ago but If I remember correctly, that pwm signal is 12v 100%duty @ the connector. (Don't quote me.lol) Not 5v. Mind you I tested this at work on a 2017mkx, but same rdu design no less. Now boost launching my sho, I graphed the rdu duty signal and this signal will NEVER reach over about 80% until after the vehicle begins moving. Which if launched @ 2200rpm or more, causes front wheel slippage, then 95-100% rdu duty cycle occurs. By then its too late, the system is now acting reactivity, trying to stop the slippage thats occuring and the tuned BMW with secretly upgraded fuel pump and 60% e85 tune that secretly runs 12.3's is 3 car lengths ahead with your 100bucks. Now my propsed solution is not drag radials on the front, but a small regulated booster box that will be wired in series with the rdu signal harness that provides 2.5~volts DC to boost the pwm signal voltage to what would be a full lock signal on launch, while still allowing the pcm to control the rdu. This also would in theory, allow us to launch at higher rpms. The down side to defeating this electronic drivetrain 'failsafe' is that we would be increasing drive line stress on everything from the ptu to rear half shafts. Things that were not designed for drag launching a 4300lb vehicle.

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Sorry about the lost race especially to a BMW. I get what you are after, but if you are going to experiment first please don't add any voltage to the signal. As you noted it is pulse modulated (length of time the signal is on) not amplitude based (I.e. voltage). Adding additional voltage isn't going to do anything except potentially fry your ecu or AWD electronics. You could in theory provide an always on signal to the AWD input however I don't know what the control unit will think of that...even if you lock up the rear 100% off the start the system responds in milliseconds (supposedly) so I don't know that expecting big time increases there is the limiting factor. You've still got the fact that it's an inherent FWD system mechanically splitting torque to the rear. Also there are a few cars running low 12's and even fewer in the 11s and they don't need greater traction to do that (not that it wouldn't help for sure). If you do decide to try it let us know what the real world results are! I'm just spouting theory and without a schematic to back up how the systems really works so anything is possible. Just don't go destroying your car...

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