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#46
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Mychailo :: 2006 Silver Mitsubishi Evolution 9, E85, 34 psi peak, 425wtq/505whp DJ :: 1995 Laguna Blue SVX L AWD 5MT (sold) Visit my locker SVX Mods: ND iridium spark plugs, Impreza RS fpr, afr tuned to 13.2:1 using a custom MAF bypass, custom exhaust, WRX 5MT w/ STi RA 1st-4th gear & stock WRX 5th gear, Exedy 13 lb flywheel & Sport Clutch, STi Group N tranny & engine mounts, urethane spacers in rear subframe, rear diff mounts, and pitch stopper, SVX Sport Strut Springs (185f/150r), custom 19 mm rear swaybar, urethane swaybar mounts, Rota Torque 17x8", 225/45-17 Proxes 4 tires, Axxis Deluxe Plus organic brake pads. |
#47
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One thing I would suggest be kept in mind is that the TCU does not have any sensors that are able to measure torque split. The readings given by the select monitor are only duty-cycle readings. A 10%, 50%, or 90% duty cycle does not necessarily mean you are getting 10%, 50%, or 90% torque transfer to the rear wheels. This is especially true if the transmission isn't in top condition, but even under the best possible circumstances, input values are not a good indicator of response. For example, half-opened valve does not mean only half the flow, or half pressure. In this example, if the plumbing is sufficiently large, a valve might need to be 90% closed to restrict any fluid at all. (Another example is the throttle valve in your car: the gas pedal. Ever notice how there isn't much difference between pushing the pedal halfway down and all the way down? There's a big difference between idle and 1/4 throttle, but not as much between 1/4 and 1/2, and almost no difference between 1/2 and wide open.)
I strongly suspect that the 90/10 and 50/50 figures are very much closer to the truth. I'd wager that even the slightest activity of the duty solenoid would necessarily cause at least a 90/10 torque split. It would be very difficult to modulate less than that. Even disabling the solenoid completely might not reduce torque split less than that. I'd also wager that the torque split does not increase significantly until the duty cycle reaches the upper 90% range. In these upper ranges, the degree of control would be marginal and it would be difficult to regulate torque split. In this upper range, torque split would probably be mostly 49% and 50%. Although the TCU makes great efforts to precisely control the torque split, I think the reality is that it's mostly just on or off. Quite frankly, there's no large fault with that. It works very well that way. |
#48
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-Chike
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"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
#49
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What you're saying makes good sense in theory, but is hard to prove in reality. I've posted my results using the SSM when in the awd diagnostic mode. The excerpt I posted at the start of this thread from the Road & Track Guide about the multi-plate transfer clutch seemed to reiterate these findings. If you or Harv can think of an elegant way to show the torque split is closer to 90/10 than 60/40 in normal driving (with no braking, acceleration or steering inputs affecting transfer) then by all means prove these results wrong. -Chike
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"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
#50
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Ssm
Chike
You might have missed the question in my post back a ways; Is it possible to buy a Subaru Select Monitor? If so, from where and how much? Thanks Joe
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#51
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I've seen them show up on EBAY from time to time... I think I was told that in addition to the SSM you will also need the SVX module/adapter?????
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Dave - 03 Baja - 92 SVX - 86 Brat - 08 OB 3.0 |
#52
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Chike, I think this is a great thread with very good information and I am glad to see someone take interest in "exploring" the SVX and it's working.
That is all I wanted to say and then I got thinking about this and driving around without a 90/10 split on the highway is really bad for mileage. Has anyone discussed the fact that the line pressure feeds the transfer solenoid? Perhaps maybe someday someone could correlate the line pressure and duty cycle from the transfer solenoid "C" with the actual pressure in the transfer housing. As I remember the EAT hydraulic line pressure varies with the throttle position. The line pressure which varies with the throttle setting then goes to the transfer solenoid "C" which regulates the hydraulic pressure going to the transfer clutch plates. So if the line pressure resistor by the battery is pulled or if a vacuum switch kit (small car) is installed, the line pressure is maximum at all throttle settings. Then 100% line pressure is fed to the transfer solenoid all the time. In this case the duty cycle numbers you read would be regulating the maximum pressure all the time and the duty cycle numbers would be equated to the torque split front/rear. When the line pressure is allowed to vary with the TPS setting, a lower line pressure is present with light throttle and maximum line pressure is available when the pedal is on the floor. This is totally independent of the transfer duty solenoid. A lower line pressure fed to the transfer solenoid that is wide open allows the low line pressure to enter the transfer clutch. The higher the pressure is to the transfer clutches the closer the SVX is to 50/50 and the faster the transfer clutches or something else wears out due to the forced slipping of the clutch plates when cornering.
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May your transmission live forever. SuperbVehicleXtraordinary Proud sponsor of a 1992 SVX. |
#53
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If you read back, on what I have written on the subject over the years, you will find that, I have allways been saying the same things. If you believed I said "that the split was allways fixed at 90/10", then you have not read what I have previously said. When the Road & Track report is used as "The Gospel ",to prove a technical point, I do tend to worry about the resultant conclusion. Just in the bit that you have posted to 'reiterate your findings', we find that they say," that the signal for the Transfer, comes from the ABS brake system". They get a bit confused on the technical bits. If you get to look at the Work Shop Manual, you will find a 3 Dimensional map, that shows the clutch pressure, relative to, selected gear, speed and throttle opening, that is a better guide to base conclusions on. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#54
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To put it easy, the C solenoid does not vary line pressure. It varies a regulated pilot pressure, that moves a spool valve, that applies line pressure to the clutch plates. As John says the resultant torque split depends on the line pressure, that the TCU can not read. So as John says. the only sure way to tell the clutch pressure affecting the torque split, is by monitoring the actual pressure applied to the clutch plates. The plot thickens. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#55
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I think Hocrest mentioned that they're sold on Ebay ocassionally - that would be the best bet if you ask me. -Chike
__________________
"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
#56
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I'm not using the Road & Track Guide as "Gospel" - if you look over my initial post, you'll see I center my conclusion around the results of my field research using Tom's Subaru Select Monitor. As far as I know, no one has ever done testing on the torque split of the USDM SVX using a Subaru Select Monitor before... How about looking at this problem in a different light. Do you know of anyone in OZ land who can loan you a SSM that'll be compatible with your VTD SVX? If so, I'll be interested in knowing the torque split values it'll show for your trans. If it accurately reads the preset 33.3%/66.7%, then I'm sure a similar licensed SSM is accurately reading the torque split on the 3 USDM SVXs we've tested (Svxfiles's, Green_eyed_lady & SVXRide). BTW, I know you're not saying the torque split is 90/10 - as you keep mentioning that it's always changing (I have re-affirmed this as well in the findings I posted). However, you HAVE mentioned in previous threads that when cruising on a highway at a relatively constant speed, the torque split would be very close to this value (95/5-90/10). My point of contention, is that not once during my testing with the SSM did I ever see the torque split registering anything close to this value. Even at a standstill in 'D', it showed 60/40... -Chike
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"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
#57
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Measuring the torque applied to the wheels requires some pretty fancy engineering. I don't think any of us are going to be proving anything any time soon. I'm pretty sure even Subaru doesn't know. They theorized, no doubt, but I'm sure trial and error was the method used to get it right. I do know for a fact that valves do not behave in a linear fashion. Even needle valves and other, more exotic, specially designed valves only behave in a linear fashion at specific available rates of flow and pressure with specific viscosity fluids. Fluid systems just aren't that well-behaved. Much like 1/4, 1/2, and 3/4 throttle doesn't make you go 25, 50, and 75 miles per hour respectively, very few valves will regulate pressure or flow in the same way. I think that oab_au and I both appreciate that the select monitor only shows what the TCU is trying to achieve, but not what is actually happening. Regarding the information provided by Road & Track, what is their source? Did they test it? If so, how? (Personally, I detest the media because it is so chronically full of misinformation.) If you reeeally want to know what's happening, a pressure gauge will give you the best data. What it tells you is far, far more meaningful than the select monitor. |
#58
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Doing the same to the VTD won't give the same results. It will only, show the % signal sent to the Limited Slip Clutch. The torque is divided by the gears in the diff, to the ratio of 36.4 F/ 63.6 R (not 33.3/66.7), the TCU does not control this split. The LSC is set to the driving conditions, to prevent wheel spin. So like your model, it will be applied "standing still in D", because it is ready for the start, when wheel spin is most likely. Just that, in the Euro, it is the rear wheels that spin first, due to them getting the most torque. I reckon if you cruised at about 80 MPH in D on a light throttle, you would see a lower signal. Not that it matters, as soon as you hit the pedal the signal would go up. Harvey.
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One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#59
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Thinking on.
About what SVXCommuter said, about the line pressure to the Transfer clutch with the dropping resistor disconnected. This would explain the problems that some have with transfer clutch binding, when the resistor is disconnected, or if the Shift kit is adjusted too much.
In short, the TCU sets the line pressure by adjusting the A solenoid, it knows what the pressure should be, so it sends the apropreate signal to the clutch, but if the pressure is higher, due to the resistor, the clutch pressure will be higher, to cause the binding. Harvey.
__________________
One Arm Bloke. Tell it like it is! 95 Lsi. Bordeaux Pearl, Aust. RHD.149,000Kls Subaru BBS wheels. 97 Liberty GX Auto sedan. 320,000Kls. 04 Liberty 30R Auto Premium. 92.000kls. |
#60
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-Chike
__________________
"Wise men talk because they have something to say; fools, because they have to say something." - Plato 2013 Cosmic Blue 5spd Evo X GSR 2006 Galaxy Gray 6MT RX-8 (sold) 2006 Steel Gray WRX TR (sold) 1996 Brilliant Red SVX L (sold) |
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