Page: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
|
|
Re: Interesting idea for a mod
Hi all, back early from our weekend trip thanks to change of weather and a noisy campervan parking near our tent(!). Thought I'd pop in and see what Rich is going on about and give some feedback on this circuit.
I don't want to create more myths than what is quelled with this circuit so I'll clarify a few things.
Noel I agree with you - in 2WD, if the wheels are spinning wildly they will remain so. To clarify my earlier statement (wheel spin stops with follow through to WOT), this occurred just prior to the change to 2nd gear at WOT. I was nearing redline and the front tyres were starting to grip more (I was on bitumen). As wheel slip slowed power started to go to the rear wheels (2 LEDS). In all other scenarios I've tried in 2WD (without wheelspin), the system engages power to the rear wheels at WOT. On dirt in 2nd, small incline, I managed to get power to flow to the rear wheels in 2WD at WOT. 3 LEDS lit, however there was a delay of what seemed to be a second. During that delay I could feel the front wheels slip but they weren't spinning wildly. I was wrong in my original thought of the system being reactive in 2WD though. The system is still proactive in 2WD, however only at WOT - just try going round a corner full blat in 2nd gear (2WD) and see what happens. I tried this and got wheelspin - but it wasn't both front wheels. It couldn't have been, because I still had full steering.
This circuit is simple in that its purpose is to measure when and how much power is being sent to the electronic coupling in the rear final drive. It is advertised that at full lock, torque split is 57% front and 43% rear. So this circuit will read on a scale of 1 to 10 how much of that 43% is being enabled. It does not display how much traction you have/do not have but it does tell you how much of a shot you have at traction. For us x-trailers, I hope it will help us unlock the All-Mode 4wd operation. From what I understand, this functionality (to tell when&how much) is not available from the factory in any of the ozzie softroaders that use an auto 4wd system so the circuit is exclusive and a one-up.
In general:
* I would recommend pulling out the 4WD actuator relay if planning a dyno run on a 2WD dyno.
* no LSD for us in Oz. Implemented via the electronic stability program (ESP) in euro models. That system is a quasi-LSD - it brakes the spinning wheel (not great for sand). New aussie pathfinder has this type of LSD
* in LOCK mode; when coasting (i.e. moving with no throttle input) there is 20% (i.e. 2 LEDS light) power to rear 0-10km/h; 50% 10-30km/h; 20% 30km/h-40km/h. Any throttle position > idle and under 30km/h = 100% power (i.e. 10 LEDS light up on display). in AUTO there is nothing without throttle movement (i.e. coasting&cruising yields nothing)
* I have noted up to 80% (8 LEDS) in 2WD mode. This was WOT acceleration and under 20km/h. Purpose of operation in 2WD appears to be for self-preservation of the drive-train (maybe the designers found they were getting wheel-spin in 3rd without it - who knows?).
It's still early days for this circuit and now that I know it works I will move on to installing it into the dash as a permanent fixture - like I did with the throttle position circuit.
Due to copyright (I didn't design the original circuitry), I can't post the article or circuit. For those interested in making the circuit, it is not available as a Jaycar/DSE kit anymore but you can see it in the Jan 99 issue of Silicon Chip (you can backorder or see it on-line).
Contact RCS Design to obtain the PCB board ( sales@rcsradio.com.au / www.rcsradio.com.au ).
Bob will make you up a PCB and even supplies a component layout for the board (so you don't even need to refer to the article if you just want to make the circuit up).
best regards
choppa
|
|
11/Jun/2006, 9:33 pm
|
|
|
|
Re: Interesting idea for a mod
Hi choppa,
Nice to have you back. I see you registered as member back in June 2004, and this is only your second post and it is very informative at that. 
Just one question for you: Where did you get the 57% front and 43% rear figures from?
It's very interesting in how the "Auto Mode" actually works and clears up a few myths on it's operation. So from what your saying then basically, in Auto Mode the rear wheels are engaging all the time? The amount of engagement is proportionate on the amount of throttle used? No wonder fuel economy is worse in Auto Mode than 2WD mode, and I bet it's not helping tyre wear as well.
If this product is not too expensive, I'm interested in installing this meter once you have it fully sorted out, so please keep us informed on it's progress.
By the way what do you mean by "throttle position circuit" ? What is this?
Cheers
Please feel free to visit the Introductions section of the forum, and tell us more about yourself: Introductions
As a new member I encourage you to familiarize yourself with the following section of the forum: Newbie Forum Guides
|
|
12/Jun/2006, 1:33 am
|
|
|
|
Re: Interesting idea for a mod
Thanks for the WB Noel. long time between posts for sure and at least that long since I've lived in Cairns as well.
http://www.nissan.com.au/xtrail/performance.asp?display#midpageAnchor
talks about the All Mode 4x4 system
yes, in AUTO, throttle appears to play a big part but reduces with speed (i.e. at low speed there is greatest power to the rear)
I'm not sure what you mean by tyre wear though. I would think tyre wear (on front wheels) is greatest in 2WD due to greatest strain on traction on the front. In AUTO mode, power is substantially reduced to the rear wheels as you go around a corner to help you drive around the corner. From what I understand, it is an electronic viscous coupling which means there is no actual mechanical connection between the front and rear final drives. Speed differential can exist between the two (I'm guessing thats why it states in the manual about overheat condition caused by speed differential - i.e. heavy sand workout). You could expect to chop up your tyres (predictably) in LOCK on sealed road though.
From memory (going back 6-8 months here), the PCB board was made&posted <$20 and components the same so cheap as chips. I'd recommend anyone interested in making this circuit to at least get the PCB as a start. Took a week or two to get this in the mail. I can post the component listing soon.
Throttle position circuit just measures the voltage (0 - 4.5v) on the throttle body motor. From this you'll know what position the throttle is (again, on a scale of 1-10). covered in more detail in post #1661 on the yahoo forum.
regards
choppa
|
|
12/Jun/2006, 9:45 pm
|
|
|
|
Re: Interesting idea for a mod
Unfortunately (due to lack of snow) I was unable to play around with WOT and it's affect on the drive being sent to the rear wheels in 2WD mode this weekend...
However I have come up with an idea for use as a "display" - in my Pulsar I had an AutoMeter Air Fuel Ratio gauge consisting of several LED's. I was wondering if this would be suitable to be used as a display - from memory I think the A/F gauge operated on a voltage of 0-1v. Ooops. Disregard that idea - the circuit choppa is using measures amps, not volts
Last edited by basshead, 12/Jun/2006, 10:32 pm
--- Rich. X-013(c)
'04 S2 ST Auto. Nudge_roofracks_tow_tints_Lightforce_GME_BFG_TBS_home-made-bashplate_50mm-spacer-lift
Click here to see >300MB of photos and videos All For His Glory. |
|
12/Jun/2006, 10:05 pm
|
|
|
|
Re: Interesting idea for a mod
quote:
choppa wrote:
I'm not sure what you mean by tyre wear though. I would think tyre wear (on front wheels) is greatest in 2WD due to greatest strain on traction on the front. In AUTO mode, power is substantially reduced to the rear wheels as you go around a corner to help you drive around the corner.
I was thinking of increased tyre wear to the rear wheels in "AUTO" mode, however I must agree with you about increased stain on the front wheels in 2WD mode. I regularly hear my front tyres ripping especially from a stationary start, so in 2WD what tyre wear I gain in the rear wheels by them free wheeling, I loose in the front wheels.
|
|
12/Jun/2006, 10:26 pm
|
|
|
|
Re: Interesting idea for a mod
OK - I'm pissed that I haven't had time the last few weekends to do my own testing at circuit design. But I'll get there! (By the way - where is the ABS/4WD electronic controller box anyway - haven't even had time to look!).
But I've been following the discussion and results with enourmous interest. My feeling so far is that the system always operates but is "tuned" differently depending upon 2WD/Auto/Lock mode. In 2WD it is tuned to operate only on the edge (WOT), Auto might be normal, Lock is tuned for the other edge - almost always on.
But another question.
I understand the rear coupling is a wet clutch that is tolerant to some slippage. But if it slips too much for too long it heats up and you get the 4WD failure light turning on and the system goes back to 2WD to allow the coupling to cool. I've read that wet clutches are pretty indescructable provided they don't overheat.
But where is the temperature sensor? I can't see one on the wiring drawings shown. Perhaps the solenoid itself heats up, resistance increases and so produces a higher voltage for the current going through it which is measured by the controller - maybe! Would this variation in resistance effect the reading of the bar graph LEDS. Solenoid power is proportional to current, so measuring current (rather than voltage) is the "right" way and should give more accurate results. But I was just going to measure voltage across the solenoid because it's easiest.
Anyway - my thoughts. But again, the results are really, really fascinating. Thanks!
Greg Smith, Perth, WA
|
|
14/Jun/2006, 12:35 am
|
|
|
|
Re: Interesting idea for a mod
Greg, faced with no conflicting information I'm inclined to agree with your hypothesis on how the ECU reads temperature. Common for ECU's to measure current in circuit this way (don't they do this to limit current to the fuel injectors so they don't burn the coil out?? - i.e., initial opening current then peak&hold current?)
As for the accuracy of the circuit, it is accurate enough. The real problem is how the measurement is made - as you rightly suggest.
Ammeters of old used a "shunt" (very low and accurate resistant value) in series with the load being measured. The ammeter would then read the voltage drop across the shunt (so, it is actually measuring a much smaller amount of current from the circuit). Problem with the shunt used in this circuit is that it is not a real shunt - its just a piece of wire. Still accurate enough though - within 10% they say.
So, if you put a "real" shunt in the circuit and measure the voltage drop across it then it will be deadly accurate - as in, the results would be no different if you used your multimeter ammeter in series.
Anyway, end of my playing with it for a little while it seems - my x-trail started mis-firing this evening on the way home from work...found a spark plug gap closed up on plug #1..very reminiscent of a fellow yahoo group member's experience back in 2004.
off to the dealer tomorrow  maybe they'll give me a new pathy as a loan car..won't hold my breath
choppa
|
|
14/Jun/2006, 10:58 pm
|
|
|
|
Re: Interesting idea for a mod
I'd say the ECU has some algorithm for working out if the clutch in the rear diff is overheating, since there is no temp sensor there.
Something like:
1. How much current is required through the solenoid to maintain the allowed wheel speed differences (front to rear and LR to RR)
2. throtle and engine revs
3. how long has the solenoid been engaged
The 4WD/ABS controller is right next to the ECU behind the glove box. There are a couple of specific wires they use to signal each other for VERY importantant things, and other more mundane things are communicated over the CAN "Cabin Area Network", which is what a CONSULTII or Cruise COntrol or any other smart units would plug into to talk to the ECU.
Choppa's done some good work there showing us how the ECU applies more or less clutch at the rear depending on the 4WD selector and throttle position etc. - very interesting.
Last edited by Eggins, 17/Jun/2006, 10:43 am
---
Shawn and Belinda Eggins
2003 STR, K&N, Strut brace, Ground wires, Dunlop LM702's, Tint, Mud flaps, Tow, Nudge, Spots, Mats, Rear scuff plate
http://eggins.synthasite.com/
|
|
17/Jun/2006, 10:37 am
|
|
|
|
Re: Interesting idea for a mod
Gee that sounds interesting. I almost forgot about this thread.
Shall be keeping an eye on you for progress on this Kev, thanks...
|
|
21/Feb/2007, 10:39 pm
|
|
Page: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Link to us
- Blogs
- Hall of Honour
- Chat
|
