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Breaking the 120 MPH barrier


Paul Booth
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I've spent the evening swotting up on the speed sense circuit in preparation for fixing my speed limit problem, the solution to begin with performing a reasonable kph/mph conversion.

 

Looking at the speed sense information path, I can't believe people only stick a pulse divider in series with the sensor and do nothing else; that would be crazy.

 

The only way I can see this not affecting performance was if the control mapping was strictly related to RPM/selected gear and speed was simply used for PPS and other ergonomic features.

 

Anyway, does anyone have a wiring/connection diagram for a proprietary SLD, along with any information as to what the SLD is doing to the EMU's input/output, that could be fax'ed/scan-emailed to me please?

 

Hopefully, I can use this to better understand what needs to be done to mine, first to restore it to original and then to convert it sensibly.

 

I don't want to buy the HKS SLD until I understand what it's doing and that it makes sense.

 

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Paul,

 

The de facto diagram of the speed sensor connections is on Pete Bett's website, but I guess you have seen this already.

 

Mr. Ash had offered to e-mail me the instructions for tha HKS SLD (pre-1996 auto version) but has not as yet. I think he has been too busy with his car.

 

If anyone out there has some HKS SLD instructions they would like to share, I would be interested in receiving a copy as well.

 

Darren

 

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Quote: from Darren Blake on 8:22 am on Aug. 13, 2001[br]Paul,

 

The de facto diagram of the speed sensor connections is on Pete Bett's website, but I guess you have seen this already.

 

Mr. Ash had offered to e-mail me the instructions for tha HKS SLD (pre-1996 auto version) but has not as yet. I think he has been too busy with his car.

 

If anyone out there has some HKS SLD instructions they would like to share, I would be interested in receiving a copy as well.

 

Darren

 

Not been to Pete's site so didn't know that data was there, many thanks.

BTW, what's the URL?

 

I too would very much like to see those instructions.

 

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DOH!!

 

I assumed that everyone knew about this so I didn't put in the URL. Here it is:

 

http://homepage.ntlworld.com/peter.betts/supra/TechTips/speedo.htm

 

Maybe if we all sit around the table, touch fingertips, burn some incense, and concentrate really, really hard, then Mr. Ash will arise from under his bonnet and help us out ;-)

 

Is there anybody there...............?????????????

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Thx guys.

 

I have found the site excellent, not least because the written notes on how the conversion should be performed confirms where I got to last night with my mulling over the diagrams.

 

I think I'll do the reverse mods tonight, if I'm not too whacked out when I get home. I'm going to solder the divider link on the Odo and *only* feed the speedo with the divided pulse train. I can live with a cruise control which only works inside the speed limit, especially as it works fine at 30 MPH.

 

Once I've done that, I'll take it for a blast and see what that's accomplished, hopefully tonight.

 

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Sorry, Darren, I have been up to my eyes in it of late. I had a quick look and I can't find the auto instructions but I'll have a good sift through my files after lunch and get back to you. The manual SLD only has 4 wires... plus and minus 12 volts and the speed-signal wire to the ECU is cut and both ends connected to the other two wires.

 

Yours,

J

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Quote: from Ash on 12:09 pm on Aug. 13, 2001[br]

Sorry, Darren, I have been up to my eyes in it of late.

 

No worries, Ash. I found out what kind of delimiting JIC do as standard which just confirmed my decision to leave the car un-delimited and fit the HKS part myself sometime in the future. I won't be doing it right away so I'm in no immediate rush for the instructions.

 

Paul: I *think* that the HKS devices "clamp" the speed sensor signal just below the limited speed so that for the majority of the time the ECU sees the "real" vehicle speed. The auto box version (according to Ash) has several more wires that allow it to talk to the auto box ECU as well, because that also needs to know how fast the car is really going.

 

Darren

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Quote: from Darren Blake on 1:19 pm on Aug. 13, 2001[br]
Quote: from Ash on 12:09 pm on Aug. 13, 2001[br]

Sorry, Darren, I have been up to my eyes in it of late.

 

No worries, Ash. I found out what kind of delimiting JIC do as standard which just confirmed my decision to leave the car un-delimited and fit the HKS part myself sometime in the future. I won't be doing it right away so I'm in no immediate rush for the instructions.

 

Paul: I *think* that the HKS devices "clamp" the speed sensor signal just below the limited speed so that for the majority of the time the ECU sees the "real" vehicle speed. The auto box version (according to Ash) has several more wires that allow it to talk to the auto box ECU as well, because that also needs to know how fast the car is really going.

 

Darren

 

Nevertheless, unless the speed signal is *only* used for limitation, the PPS and the cruise control, it's going to upset the EMU by changing its engine input parameters (RPM, etc.) but then telling it the speed hasn't changed (what a slipping clutch that would be).

 

I'm gonna assume the UK EMU is different as it has to handle all the differences I'm identifying on a different thread and therefore the speed limitation is embedded in the EMU software.

 

Anyone know what's really going on with the HKS SLD?

 

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Oh My God!!!!!

 

I think they've tee'd into just about every wire on the back of the dash.

 

1. power feed to the clock(!) cut through and tee'd into

2. earth to the speedo cut through and tee'd into

3. sensor feed to odo cut through and then re-connected without any other connection

4. sensor feed to speedo cut and split to converter box, 3(?) wires, one going nowhere

5. repeater wire (pink) from odo cut, odo end taped and the other driven from the converter box.

 

I think if someone hadn't stopped them, they'd have wired in the air conditioning too.

 

I do hope this wasn't done by JIC's people, it's a feckin disaster.

 

I seem to remember mentioning on more than one occasion that my car had been assaulted by a team of crazed, blind and lobotomised lunatics armed with wire cutters.

 

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The pulse converter has been made by Convertek in Galway but for who is not clear. Convertek are a small contracting electronics design house who'll knock you up something to your spec, or design something for you.

 

They've based it around the Motorola 68HC711. Pretty good in automotive applications with it's good resistance to electrical noise and temperature extremes, although I personally don't like the 6800 instruction set and would have gone for an 8031 derivative; or a PIC chip (yay!).

 

Given that the company who had the box made by Convertek seem to want to remain anonymous (I wonder why), I guess I'll be contacting Convertek to find out what all these apparently pointless wires are supposed to be for.

I guess I might as well use it's 8/5 pulse divider for the speedo, if nothing else.

 

I wonder....... if it's also got a built-in SLD. That would be too much to expect, wouldn't it?

If it has, it would explain all the tee points (not the abortion of a wiring job but you can't blame the box for that).

 

Hmm, pulse converter PLUS SLD in one box, Mr Betts where are you?

 

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I really hope it wasn't JIC that mauled it as my new baby is there getting the SVA at the moment.

 

Infact when I requested they didn't fit the delimiter they said they wouldn't do it because of the SVA and it's a doddle to remove anyway. Hardly the masacre you described.

 

I've got a whole host of electronics I need fitted, so hopefully i'll be able to find one of these field loom things before my new car turns up (RLTC, FCD, SLD).

 

Since me welding a soldering iron is a signifigant danger to myself and anyone around me i'll at least have a fighting chance of getting it right! Maybe i'll have a practice run on the old one! :)

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Quote: from Paul Booth on 3:44 pm on Aug. 13, 2001[br]
Quote: from Darren Blake on 1:19 pm on Aug. 13, 2001[br]
Quote: from Ash on 12:09 pm on Aug. 13, 2001[br]

Sorry, Darren, I have been up to my eyes in it of late.

 

No worries, Ash. I found out what kind of delimiting JIC do as standard which just confirmed my decision to leave the car un-delimited and fit the HKS part myself sometime in the future. I won't be doing it right away so I'm in no immediate rush for the instructions.

 

Paul: I *think* that the HKS devices "clamp" the speed sensor signal just below the limited speed so that for the majority of the time the ECU sees the "real" vehicle speed. The auto box version (according to Ash) has several more wires that allow it to talk to the auto box ECU as well, because that also needs to know how fast the car is really going.

 

Darren

 

Nevertheless, unless the speed signal is *only* used for limitation, the PPS and the cruise control, it's going to upset the EMU by changing its engine input parameters (RPM, etc.) but then telling it the speed hasn't changed (what a slipping clutch that would be).

 

I'm gonna assume the UK EMU is different as it has to handle all the differences I'm identifying on a different thread and therefore the speed limitation is embedded in the EMU software.

 

Anyone know what's really going on with the HKS SLD?

 

 

 

I believe the PPS and Cruise use their own ECUs I just used the devided signal from the divider on my speedo and fed that to the ECU on the loom close to the ECU (ie no chance of the signal being used by one of the other boxes) and everything was fine.

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Quote: from Gareth Davies on 11:32 pm on Aug. 13, 2001[br]Infact when I requested they didn't fit the delimiter they said they wouldn't do it because of the SVA and it's a doddle to remove anyway.

 

Gareth,

 

Just for clarification, are you saying that JIC were happy not to fit the delimiter?

 

I'm going to be asking them the same thing: connect the pulse divider to the speedo only, and leave the odo and the other connections well alone.

 

Darren

 

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What Paul has described is typical in my experience.

 

I've said this before several times, but in case anyone doesn't know it is a fire-brigade statistic that around 95% of all car fires are caused by badly fitted aftermarket electrical equipment.

 

As regards the SLD instructions, I had a search but cannot find them. Which is a PITA as I have to fit the unit to JF's car soon.

 

As to exactly what the HKS FCD's do: the auto version has about 15 wires connecting all over the place. So what it does, exactly, I'm not sure. The manual version is, as Paul says, probably some pulse-train divider.

 

If anyone who has the manual unit wants to know for sure how it functions then by all means post it to me and I'll stick a sig-gen and scope on it and so some tests.

 

Yours,

J

 

PS

I will come across the auto SLD instructions eventually. All I've done is to put them somewhere safe, and now I can't find them. :)  

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A dealer *has* to convert the speedo for SVA.

 

My car wasn't imported by JIC but another dealer whose owner brought it in for their personal use. He will have been the one woh had the conversion work done.

JIC will *only* have swapped the odo to a uk-spec version on my car.

I have to confirm this Steve but I'm only doing that to confirm what I already know.

 

JIC's people installed the cat1 alarm. I have to say, I wasn't over impressed with that but then my standards are a bit high in the wiring department. The last time I fully re-wired a car it was with fire-proof military aircraft cable, so don't use me as a yardstick.

 

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I wonder if JIC are getting confused about "not fitting the delimiter".

 

Yes, they have to convert the speedo for the SVA, but that does not mean they have to also wire it into the odometer, ECU, or anything else behind the dash.

 

As knowledgable as they are, Steve and Tim are not technical people. When asked "not to fit the delimiter" they may have thought they were being asked not to fit the converter box AT ALL, which of course would mean the speedo could not be converted.

 

Steve said he would ask their conversions guy to call me direct so that we could discuss what I did and did not want done before he worked on my car.

 

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I swear that if I ever catch up with the ar$ehole who did the kph/mph conversion on my car, I am going to tear him an extra ar$e and shove his head up it.

 

I couldn't understand why, even though the odo pulse feed had been re-made after being cut(???), the repeater (pink) feed to the Engine Management Unit/PPS/Cruise/etc. was cut and being fed by an extra wire from the convertor.

 

My loom is now, at the top end, as Japan, i.e. it displays kph and if the odo hadn't been swapped for a uk version, it would be clocking km.

 

I re-attached the repeater wire (pink) to where it belongs on the odo output and guess what, the cruise control has stopped working.

I have no means to tell if the PPS/etc. is getting a signal, yet.

 

Prior to my going to the diagrams, does anyone know of an easy access point for that circuit, e.g. on the cruise ECU?

 

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So that's what a speed limiter feels like.

 

Once the roads quietened down I took the car out onto the A419 passed Cirencester.

 

The effing cruise control worked fine from 25 mph up to 70 mph, I give up.

 

So having gone up and down the speedo a few times, I opened it up and waited to see what happened. Guess what, I hit the speed limiter.

For those people who've been trying to find out what that feels like, imagine running out of petrol in 2 second bursts, just long enough for the speed to drop a couple of mph, then it picks up again and almost immediately "runs out of fuel" again. Seriously weird.

 

Now the next bit is probably nonsense, however, I drove back along a nice windy, quiet, 'A' road for about 15 miles. I got the impression the car was always in the right gear, there wasn't the same hesitation on kick-down, didn't notice lag the same (result of being in the right gear). Overall, I felt the car was way more responsive.

 

Next job is a *good* SLD and we'll see if we've cured the 120MPH syndrome. Then I can fit the RL TC and mod the speedo to MPH *not the wiring loom*.

 

Ooh, I feel smug.

 

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