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#16
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Phil, Apologies, I DO read your posts, but having connected up the JDM control unit, and finding the speed signal giving me a very "fast" signal on the mileage, i.e. the mileage was clocking up at non-representative rate, I disconnected it, and put back in the Euro one. Now I appreciate the fast mileage thing was caused by the SS2 signal being fed in whereas the box was set up for the Hall effect one, so my subsequent search for a forced Power mode solution was based on the expectation that the JDM and Euro TCUs are largely the same, and it would be good to find the switching mode to make the Euro box have Power mode full time. If what you are saying is correct, and possibly also if the US TCU control box is wired similarly to the JDM one because of the Hall effect VSS2 sender, then it is actually possible that grounding a4 on the US one will activate full Power mode, where I would have been expecting Econ mode. {It might be difficult to detect if the US boxes switched on Econ from pin 4, as I imagine their combination meter is not wired up for the Econ light. If grounding the a4 pin switched on the Power light for them, then you would know which way things were hanging} As I have already tried your JDM solution, and determined that the Power light comes on when the Econ switch is on, can you now tell me how the JDM TCU will accept the in-gearbox SS2 signal, and not give a crazy speed/mileage output? In other words, if I plug in the JDM TCU, do I also need to sever some of the Hall effect connections that are redundant in order to get a meaningful and usable speed signal? Is it even possible we would need the US TCU to make this Pin 4 grounding give us Power mode without getting a distorted speed output? Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#17
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Woke up early!
Such a lot of controversy and confusion . Thanks for volunteering to try it out on a U.K spec box Joe. |
#18
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On the UK wiring diagram, the only thing between the speed sensor and the speedometer is that circuit a17-c6 that converts the speed sensor signal to a square wave suitable for the speedo. From what you've discovered, the circuit in the UK TCU must divide the signal by the final drive ratio but the JDM one doesn't. Possibly it's done in software and the constant is missing because the circuit is not connected on JDM cars. I don't see any easy way to work around that problem, other than fitting a JDM speed sensor.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II |
#19
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Agreed Phil
That's why I have resorted to trying to impose Power mode on the UK variant, long term it would be more useful to more people. I might try earthing those pins to see what would happen. The other thing that occurs is that the Econ mode is the obverse of the Power mode. Do you think it might be a runner to offer say 5v to that same pin, to see if that might trigger Power mode, or would I be playing with fire and blow the box? Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#20
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The way that transistor electronics normally work is that the inputs are either in one of two states. Either "grounded" (ON) or "not-grounded" (OFF). The TCU "floats" the pin at 5v and then it detects when the pin is "pulled down" to ground. Not that I really know anything about electronics. The ultimate solution would be to reverse engineer the software in the TCU. It's just a simple 6800-based computer. I wrote an OS for a similar board for my final year project at university. If I knew how to download the code onto my PC then I would spend a little time disassembling it. It would be cool to be able to customise the shift maps, particularly for the guys who have changed their diff ratio. There are solder tags on the board that could be some sort of serial or jtag interface for diagnostics. But I don't have the hardware expertise to figure it out.
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Subaru ECU and TCU Website 1992 Alcyone SVX Version L 1992 Alcyone SVX Version L 1994 Alcyone SVX S40-II 2004 Subaru Legacy 2.5 SE Sports Tourer 1996 Subaru Legacy 2.2 GX Wagon 1988 Subaru Justy J12 SL-II Last edited by b3lha; 09-02-2006 at 03:04 PM. |
#21
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#22
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You are sure to be correct Pete. Adding 5v to that pin would be pi$$ing in the breeze.
I have a new plan that takes account of Mike's advice that will work for UK cars. [The US cars can use a variant of it also if they want] Using the Econ switch I will feed the 5v line to the TPS pin of the TCU. To stop the 5v going back up the line to the ECU and causing problems, I will be adding an in-line diode to the connection so the 5v can only go one way to the TCU, and not feed back to the ECU. In addition I will put an interruptor in the line, so the TPS pin is reading 0-5v rather than a steady 5v. This will ensure Power mode is permanently on. I am not sure what Mike means by a "555 timer", but if it is simple and easily installed, that is what I will use. Something like what breaks the circuit for the indicators or the hazard lights would do nicely, but of course no way I would accept the clicking. An inaudible device would have to be found. I find it interesting that in the JDM TCU that has switchable Power mode, the speed sensor two input is a 5v square wave. Connecting this square wave internally in the box to the TPS input would have the same effect as described above. I wonder if this is what is done internally in the JDM box to turn Power mode on, when pin 4 is earthed? We will never know, I suppose. Anyway, I now see a way forward. I will rewire it when the new gearbox is in. I don't want to do any messing with the wires until I am sure all the readings and input/outputs are in the correct range. That way I won't compound a felony. Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl Last edited by svxistentialist; 09-05-2006 at 04:59 PM. |
#23
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Pete. |
#24
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Thanks for that. Just in case the dropping off after 10 seconds is peculiar to the USA tranny computer, it will make sense for me to just try the solid 5v feed first. If it remains stable, then Bingo, problem solved. If it drops off after X, we won't even ask Y, we'll 555 it. Ta Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#25
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If You Really Want Power Mode All The Time Just Adjust Your Tps Sensor To Far Found That Out By Accident.power Mode Is On As Soon As The Car Is Started.
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#26
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Sounds interesting. Thanks man, I might give it a go. Did you adjust your Caps Lock too far at some stage also maybe?
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#27
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Some clarification needed:
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Can you throw some light on this question for me? You described using a pulsed or interrupted 5V signal to the TCU pin for the TPS signal. You may have used a voltage divider to provide 5V, and interrupted the 5V using a 555 timer. Now you say this genuinely works, and turns on Power mode. However, in your earlier descriptions, you mention that showing the TCU this WOT voltage also sends the gearbox into defcon 5 mode, i.e. it activates kickdown to the lowest gear. Can you please verify if this is the case? If the TCU needs to see variable voltage there on that pin, so it can decide when to activate kickdown, then this applied fluctuating 5V to the TPS input pin will give Power mode OK, but may also apply kickdown full-time, which is a little less desirable for those who want to live. What's the story? How did it work for you? Thanks Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#28
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The 555 Timer does the TPS blips into the TCU while you maintain control of the engine by way of the physical accelerator pedal (TPS signal to the ECU). Blipping the TPS wire to the TCU with 0 -> 5 -> 0 -> 5 -> 0 -> 5 does not cause the transmission to kick down gears. It depends on the length of which +5V is applied. If it's for 250 ms (for example) there's not enough time to kick down gears. Now if you maintained constant (or long period of time) +5V to the TPS input, the TCU will kick down ...it will think, "what the heck? this guy is flooring the car, but the RPMs are barely increasing - let me kick down a gear cuz this guy wants to MOVE." Gear changes are determined more by the RPM signal input into the TCU (which we are not changing). Does this help?
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Mike - Proud owner of a Pearl 92 SVX LS-L 5MT with 78k miles and climbing 5-Speed Status: DONE! Lambo Door Status: On hold but will be a success 04 WRX 5MT, STi Short Throw Shifter, Group N tranny mounts, AZA Z-2 18x7.5 Rims, slotted/cross drilled rotors, stainless steel lines, 35/20% window tint, ecu bead crush, power mode button; 7" In-dash touch screen LCD, mobile computer, voice recognition, alpine PXA-H701 DSP, 2 JBL amps, focal speakers all around, 5 farad cap, and fiberglassed subs in the trunk. The Mobile Computer Interface - featuring the SVX | My Locker | My Secret Stash |
#29
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Yeah. A lot. Thank you. If the 0-5v break is short enough, then the TCU circuitry decides that Power mode is required [because of the sudden-ness of voltage rise] but because the 5V is not maintained, it does not cause kickdown to a lower gear. That is magic in a way. You are then saying that the shift map uses rpm and road speed to assign gear changes. But these changes are assigned from the Power mode shift map, not from the Normal map. The key or trick to it is keeping the 0-5V interval very short, using the 555 switch, that presumably has a variable interval. Thanks Mike, that seems to solve the conundrum. Joe
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Black Betty [Bam a Lam!] '93 UK spec, still languishing Betty Jersey Girl Silver '92 UK [Channel Isles] 40K Jersey Girl @ Mersea Candy Purple Honda Blackbird Plum Dangerous White X2 RVR Mitsubishi 1800GDI. Vantastic 40,000 miles Jersey Girl |
#30
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It would not be difficult within the TCU, to separate two such individual signals, so that it would appear that a RPM signal would not be required in respect of the original arrangement. You have certainly carried out some interesting experiments and the information you have provided is very much appreciated.
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Trevor, New Zealand. As a child, on cold mornings I gladly stood in cowpats to warm my bare feet, but I detest bull$hit! |
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