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Breaking the 120 MPH barrier (bis)


Paul Booth
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I've had to start this thread as there's something strange going on with the original thread, i.e., I can 'quote' but if I hit reply, strange things happen, so..........

 

So far so good. Using the JIC speed converter, I have modified the speedometer to read in MPH not KPH.

 

This entailed cutting a 4mm section from the signal track and then scraping back the insulation from each new end, then removing the insulation from a 4mm length on 2 others.

 

I tinned all new contact points on the flexi-pcb and soldered the +ve and gnd wires, on the converter, to the main instrument live and ground tracks (previously stripped and tinned), about 20mm from the connector.

 

I soldered the input to the converter to the cut track, nearest to the connector and the converter output to the end nearest the speedo screw terminal.

 

After completing the soldering, I applied a strip from a glue gun across each wire about 10mm from the solder point to prevent stress tears in the flexi-pcb.

 

I mounted the converter on the plastic bracket on the rear of the combination meter used, I believe, to push the wiring loom passing behind the speedo away from the back of the speedo.

 

Works a treat and if I ever get a UK combination meter, I can just swap it straight out with no modifications required on the wiring loom.

 

I have now proved that:

1. the odo pulse shaper output has been damaged during the original conversion and it's breaking down, probably in thermal runaway, so the pulse train stops being delivered to the various ECUs after about 5 minutes. or

2. One of the ECU's has a similar problem on it's input buffer and it's overloading the speed pulse bus once it gets warm.

 

I'm using the converter's 2nd output (I know it's 8/5) to drive the ECUs until I get the replacement odo to test and, even if an ECU has an input problem, the converter's output is sufficiently macho enough to handle it. I rather think it proves my point about the odo though.

 

So, once I've got the guaranteed pulse train, from Sensor No 1 via the pulse shaper, it's time to fit the SLD, (See other thread) then I can see if my 120 MPH problem has gone away.

 

I'm going to update this thread only in as much as I reach conclusion on the odo, then it'll all be about the SLD.

 

Oh yeah! unless the SLD doesn't cure my 120MPH limit problem.

 

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Paul,

I have the same problems, no cruise above 70, top end appears to be about 120. Conversion done by JIC.

I have asked Steve (JIC) if he can send me details about the conversion and await a reply. However, I would be very interested if you have managed to cure both problems, or had a reply from Steve yourself.

 

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I've talked to Steve at length about this and their conversion will work OK on manual Supras. It may work OK on most autos too but the odd one might just be quirky.

 

Their converter kit is way better than the one which was fitted to mine originally (thanks Steve).

 

What I've done is use the perfectly good JIC converter box to convert the speedo *only*. That is, I've modified the flexi-pcb on the back of the speedo to fit the converter directly to the speedo. When the speedo comes out, so does the converter.

 

JIC also fit a UK spec odo so it doesn't need any hacking of the wiring loom but they *do* feed the 8/5 signal from the converter to the ECU daisy chain (it removes the speed limitation) and hence the output from the odo is left floating.

 

I've restored the wiring loom back to original and discovered the pulse shaper in the new odo (it cleans up the sinusoidal signal from Sensor No 1 and makes it a fixed voltage square wave) is goosed (technical term).

 

I ordered a replacement odo (£60ish inc VAT), delivery in 2 days but they ordered a f*****g warning light panel instead and I've got to wait until next week now (see side-light thread with barbed wire stick incident).

 

I have the HKS SLD waiting to be fitted but in the short time the original odo worked after I restored the loom, everything worked much better (gear changes smoother, PPS felt heavier at mid range speeds, etc.) right up to the dreaded speedlimit barrier.

 

I feel very hopeful that once I have a fully functional odo in place driving the ECU chain with the correct pulse chain, the car will be ready for the SLD.

 

If that doesn't fix the 120MPH issue then it's down to Ash's as he has the appropriate kit I no longer have and is x1,000,000 more familiar with all the other bits likely to be causing a problem.

 

With regard to the cruise control, that doesn't make sense however you cut it. If it's getting 8/5 pulses (and it's supposed to be), then it should *not* top out at 70MPH. That's making me nervous right now as it suggest something beyond the obvious.

 

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Quote: from Paul Booth on 5:50 pm on Sep. 1, 2001[br]JIC also fit a UK spec odo so it doesn't need any hacking of the wiring loom

 

Hmmm.

 

Wouldnt be too sure about this, Paul. They were going to feed my odo with the same 5/8 signal that goes to the speedo (until I stopped them).

 

Because I have an auto, I too have a speedo-only conversion a'la PB (except my loom is modded rather than the speedo) head.

 

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Darren,

 

No. I've spoken to Steve about this. They buy a few UK spec odos to always have some on tap and those they take out get converted to UK spec by a 3rd party company (mine is one of those, I believe, and was not protected from thermal/static damage).

 

The wiring loom change at the odo is where they feed the 8/5 signal into the ECU chain. They cut the pink wire from the odo pulse shaper output and attach the converter output no. 2 to the ongoing line.

 

'They',  as in a 3rd party autoelectrician, *not* JIC in person.

 

Simon,

 

That's exactly what I did to identify what's really going on. Your speedo reads in KPH, your odo clocks up miles, you have a 112MPH speed limit and everything else works perfectly.

 

You can then mod the speedo *only* to read MPH and fit the HKS SLD to remove the 112MPH speed limit.

 

I don't know what signal (1/1 or 8/5) your cruise is receiving so I can't comment. If it's like mine then you have the same issues, which don't make sense.

Interestingly, when I was running unconverted, the cruise still gave me more than an expected 40ish MPH. The cruise control is doing something not just covered by the Sensor No 1 signal.

My worst fear is that someone is tapping Sensor No 2 (the gearbox speed sensor) for the cruise but it's highly unlikely. That only leaves a cruise control which is doing something more than watching Sensor No 1.

 

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Quote: from Paul Booth on 11:20 am on Sep. 2, 2001[br]No. I've spoken to Steve about this. They buy a few UK spec odos to always have some on tap and those they take out get converted to UK spec by a 3rd party company (mine is one of those, I believe, and was not protected from thermal/static damage).

 

The wiring loom change at the odo is where they feed the 8/5 signal into the ECU chain. They cut the pink wire from the odo pulse shaper output and attach the converter output no. 2 to the ongoing line.

 

'They',  as in a 3rd party autoelectrician, *not* JIC in person.

 

Okey dokey. I suppose there's really no point in arguing over it, but Steve *did* put me in contact with their auto electrician.

 

I gathered from our conversation that their standard procedure was to "clock" the odo back to the equivalent miles reading and then feed it with the 5/8 signal. Fitting UK spec odos was never mentioned. *However* I could have got my wires crossed (geddit?). Anyway, whatever they did (or are doing now) its academic for you and I since we both have beautifully unadulterated electrics :-)

 

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Simon, what you are describing is very common.

 

Problem is, most auto electricians should be working in a butcher's shop and the base knowledge of most owners is other than in electronics and/or mechanics.

 

The solution(s) to these problems are really quite simple.

 

To get your cruise working at a more reasonable range - 40 mph to 120 mph - all you do is feed it with a 5/8 divided speed signal.

 

I often read about instances where people quote what they have been told, on this BBS, by (so called) experts.

 

For example, I would dearly love to know how the odo can be "clocked" to the equivalent miles reading. For that you would have to make the reading less. You can clock the odo upwards by feeding it with a sig-gen. But you cannot clock it down.

 

Yours,

J

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Guys, in case you've ever wondered I've done all this before years ago and sell speedo converter units at £60 each. I've got full schematic details of how to wire it in and the effects different mods can have.

 

Getting cruise to work, active spoiler working is all easy and achievable on ALL MkIV Supras. Trust me, I've modded so many.

I think the JIC converter may just be a pile of *** by what you are all saying.

 

Check out

http://www.trlperformance.com/supra

and click on "speedo conversion"

 

There's lots of other stuff on there as well for the electrically minded.

 

Pete Betts

 

I also sell fuel cut controllers (like the HKS FCD's) plus a load of other stuff.

I hardly ever look at this site as my time is limited, should have got here sooner. I'm mostly on the older UK Supras site.

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Quote: from Peter Betts on 8:20 am on Sep. 3, 2001[br]Guys, in case you've ever wondered I've done all this before years ago and sell speedo converter units at £60 each. I've got full schematic details of how to wire it in and the effects different mods can have.

 

Getting cruise to work, active spoiler working is all easy and achievable on ALL MkIV Supras. Trust me, I've modded so many.

I think the JIC converter may just be a pile of *** by what you are all saying.

 

Check out

http://www.trlperformance.com/supra

and click on "speedo conversion"

 

There's lots of other stuff on there as well for the electrically minded.

 

Pete Betts

 

I also sell fuel cut controllers (like the HKS FCD's) plus a load of other stuff.

I hardly ever look at this site as my time is limited, should have got here sooner. I'm mostly on the older UK Supras site.

 

Well about f*****g time. I wondered when you'd show up. LOL.

 

A couple of us have got weird things going on Pete. Specifically, although the ECU chain, normally fed indirectly via the pulse shaper in the odo, is supposedly being fed with an 8/5 pulse train from a simple 8/5 frequency converter, the cruise control is still only allowing a top speed of 70MPH. This is contra-intuitive.

 

As you know, with the ECT, PPS, Engine ECU, etc. being fed from the 5V pulse train from Sensor No 1, to simply feed an 8/5 signal to that ECU chain is a total bollox on an auto vehicle. Although strictly speaking the ECT uses Sensor No 2 as it primary speed information and only uses Sensor No 1 as a backup, I have strong evidence that with Sensor No 1  providing conflicting data, the gearbox is not performing optimally.

Now as to why the cruise control should be behaving as it does, that's a total mystery.

 

I'm still 100% convinced, subject to getting some seriously accurate data complete with proof, that converting the speedo-only to MPH, swapping the odo for a UK spec version and finally fitting something like the HKS SLD which takes the gearbox into consideration in it's signal control path (hence HKS having a simple SLD for manuals and a seriously over-fed Octopus for auto systems) is the *correct* way to go.

 

If'n yer going to keep playing with the kids on the other BBS Pete, yer gonna miss out on grown up conversations :biggrin:

 

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A true speed delimiter may be the key rather than using the scaled 5/8ths signal.

I haven't personally seen a problem with my Auto box using the scaling method but then I've driven so long with it I've forgotten what it's like with the original 1:1 signal. What does this feel like?

 

>swapping the odo for a UK spec version

 

You know the two units are identical apart from two surface mount resistors that are located in different positions. One lights up the MILES and Km display and the other controls how the device interprets the digital signal from the speed sensor. i.e. how many pulses for Km and how many for Miles.

 

 

 

> HKS SLD which takes the gearbox into consideration

 

SLD = Speed Limit Device? Is that right?

If so what connections does it have to the gearbox ECU?

 

>and a seriously over-fed Octopus for auto systems) is the *correct* way to go.

 

Got any installation instructions anywhere?

 

I've just redesigned my speedo converter boxes to have both a 1:1 scaled output, a 5:8 scaled output (Both with +/- 10% calibration adjustments) and I might add a true Speed Delimiter Output as well if this is the way to go.

 

I'm not sure why the cruise isn't working above 70mph.

I've got my ECU, gearbox ecu, PPS, Cruise, Odo and Speedo receiving 5:8, and the Active spoiler receiving 1:1. I know I should have the PPS receiving 1:1 but I've just never got around to changing it back again.

 

Regards

Pete

ps. Still looking into the Toyota ECU internals Paul?

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Quote: from Ash on 8:15 am on Sep. 3, 2001[br]For example, I would dearly love to know how the odo can be "clocked" to the equivalent miles reading. For that you would have to make the reading less. You can clock the odo upwards by feeding it with a sig-gen. But you cannot clock it down.

 

I suppose I must have got confused then...

 

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> I haven't personally seen a problem with my Auto box using the

> scaling method but then I've driven so long with it I've forgotten

> what it's like with the original 1 to 1 signal.

 

My car is doing all sorts of weird shit, as are other people's autos that have been converted with a 8/5 divider box. When I restored mine to orginal spec, the gear changes became smoother, especially going up the box.

No proof but, as the TRC ECU uses the same pulse train and the ECT uses the TRC to reduce engine torque during up-changes by flipping the sub-throttle closed for a millisecond or so, I think there may be something going on in that interaction.

Although the ECT uses Sensor No 2 for it's reference point and 'officially' only uses Sensor No 1 as a backup, it may be that the ECT does comparisons and gets upset by mismatching data; maybe it splits the difference.

 

> You know the two units are identical apart from two surface mount

> resistors that are located in different positions. One lights up the

> MILES and Km display and the other controls how the device

> interprets the digital signal from the speed sensor. i.e. how many

> pulses for Km and how many for Miles.

 

Yep! JIC originally bought a few UK spec odos to fill the pipe. Then they have the ones they take out converted in the manner you mentioned. With the occasional wastage (oops, we f**K

ed this one up) they still have to buy the odd one. Mine is a conversion, I checked, and I'm convinced they've knackered the pulse shaper output drive.

 

> SLD = Speed Limit Device? Is that right?

>

> If so what connections does it have to the gearbox ECU?

>

>> and a seriously over-fed Octopus for auto systems) is the

>> *correct* way to go.

>

> Got any installation instructions anywhere?

 

Think it's Speed Limit Defence, but don't quote me. HKS do 2 very distinct types. One that is basically a 8/5 converter for manual cars, *but*, they do one which hooks into the whole ECU stack area for autos.

Bearing in mind the ECT ECU and Engine ECU use the TRC ECU to control torque during up-changes, anything affecting perceived speed has to take this operation into consideration.

 

All the HKS instructions are in Japanese but I have the supplied manual scanned and copied into a Word document with all the Japanese text removed. A friend's friend is a Japanese middle-manager at the Honda plant down the road in Swindon and I've been assured that once he's back in the UK, he'll read the HKS manual and give me the English words to enter into my Word doc. Then it's public domain.

 

> I've just redesigned my speedo converter boxes to have both a 1:1

> scaled output, a 5:8 scaled output (Both with +/- 10% calibration

> adjustments) and I might add a true Speed Delimiter Output as well

> if this is the way to go.

 

Wanna stick a scope on an HKS 'auto' box (once it's in situ, say in 2-3 weeks)?

 

> I'm not sure why the cruise isn't working above 70mph.

> I've got my ECU, gearbox ecu, PPS, Cruise, Odo and Speedo

> receiving 5:8, and the Active spoiler receiving 1:1. I know I should

> have the PPS receiving 1:1 but I've just never got around to

> changing it back again.

 

That cruise control is confusing the shit out of me. It's so illogical.

 

One thing that *just* occurred to me. The Japanese are buggers for updating the embedded software and changing the reaction to changing stimuli (as you know). They call it 'improvements' I call it 'changing where the bugs are'. This would be a large factor in the difference in behaviour between models.

 

Mine is a '93 model. Anyone else with a funny cruise: what's the age of your car?

 

> ps. Still looking into the Toyota ECU internals Paul?

 

I've got that on my list but I'm not even thinking about it until:

A. my car has been successfully speed delimited with the HLS SLD for autos

B. the cruise control's behavious is understood, or at least predicatable

C. I have the RL TC fitted and working

 

I have another idea on suppression of the shitty original TC without affecting the auto up-change torque control. I'll start a thread "Suppressing stock TRC" later today. As it's only basically a Schmidt, you might want to knock some up. I can only do software these days (no bench, no kit - moved house, wife put her foot down).

 

 

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Paul, mines a 93 auto gz aero, converted odo as yours and with the same cruise problem (and limited to 120 top end as well)

 

I would willingly pay someone who REALLY knew what they were doing to fix it for me. I don't have the time to have it off the road whilst I try worting it out.

 

Any offers, Pete?

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I don't want to raise *any* expectations but this is starting to get the feel of an age related software *feature*, i.e., the equipment version number.

 

Simon, if this turns out the way I anticipate, you'll be able to do it yourself. You can handle a soldering iron and wire cutters, can't you?

 

Failing that, once I'm totally sure we have it cornered, if Pete doesn't want to do it, Ash will have all the details and could probably be persuaded by greasing his palm.

 

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Yep, use to build rain alarms from practical electronics too many years ago to remember.

 

By the way, the JIC guy who does the conversions is I quote from Steve:

"If you can call our garage ( Andrew ) he will be able to enlighten you on 01342 325544" unquote

 

I'll try him tomorrow and see what he can tell me.

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