VVTi Tiptronic Speedm8 speedo converter

I wonder if anyone with a Speedm8 speedo converter (or other make), specifically fitted to the VVTi tiptronic model, would be prepared to share their experiences of it's performance.

The reason why I raise this is because I've been getting erratic behaviour from another speedo converter (I can provide more details but this has been discussed on the forum before - problems with speed sensitive steering, traction control, etc.) and thanks to the wonderful search facility of this forum (and the input of it's members), found that the Speedm8 device appears to offer a unit that meets my requirements, namely:

• recalibrate the speedo. (odo.) input signal so it reads mph (miles) rather than kmh (kilometers)
  
• leaves all other 'downstream' devices (those that rely on an output signal from the speedo.) unaffected.
  
• er, that's it!
  

Sounds simple but, judging by shared experiences on the Tiptronic model, is in reality quite difficult to achieve. I think the difficulties have been exacerbated by an extra requirement - that's deliberately not on my list - to delimit the top speed.

Anyway, I approached the company that sells the Speedm8, tried to verify that it met my requirements. I was informed that it did and also provided a speed delimiter in a single (programmable/adjustable) device. Great! I ordered one and it turned up today.

Imagine my disappointment then when the fitting instructions made it clear that the Speedm8 device is fitted at the ECU, used a supplemetary speed input signal (ABS sensor? rather than the one sent to the speedo), generated a converted speed signal from this and fed this to the speedo - all of which means, of course, that any devices that depend on the output of the speedo get a converted signal and ... I'm back where I started.

Or so I thought.

I queried this with the Speedm8 technical support team (great bloke called George) who said that they were already aware of this problem and could provide a second unit (to be used in addition to the first) to overcome this.

Interestingly, I think he was only aware of this affecting the active front spoiler, not other systems. I'd be interested to know if anyone using one of these particular devices currently has experienced any problems with, for example, power steering or traction control.

I explained to George that there was now a known 'feature' of the Tiptronic cars that have been delimited (possible kick-down into the red at high-leptons) and asked whether a 'simpler' version of the Speedm8 could be programmed to meet my requirements without a combined delimiter in a single unit and could, therefore, be fitted behind the dash.

Apparently no-one has ever asked for this before but the man from Speedm8 he say yes!

I'm sending mine back today for an exchange unit and I'll let you know how I get on but I'd still really like to hear other people's experiences in the meantime.

Sorry for the long post but it really gets to me that such a simple thing as changing the way the speedo behaves can have such a drastic effect on an otherwise brilliant car!

pmed you bud

Responded mate.

Incidentally, if you do have one of these units (or the ultra-rare Thor/TRL version) already fitted to your Tiptronic, you can very simply remove the top speed delimiter function. You may also find this gets rid of problems with gearbox change points and traction control (random 'snow' mode).

Pin 2 on block C of the ECU is the input speed signal (red wire). If you have a speed delimiter fitted it will be 'between' this wire. To remove the speed delimiter:

• disconnect (and insulate) the output wire from the speed delimiter that is joined to the ECU side of the red wire;
  
• leave the input wire to the speed delimiter, that is joined to the loom side of the red wire, attached (needed for speed conversion);
  
• rejoin the red wire ends, to reinstate the input speed signal to the ECU.
  

All this will do is stop the speed signal being 'capped' so you will hit the ECU speed limit if you exceed 112mph. The speed converting functions are unaffected by this change so, if you're not experiencing any other adverse affects (because systems 'downstream' of the speedo are still getting a converted signal) you're done!

Me - I'm still waiting for the new SpeedM8 version to arrive ...

Back home from holiday last night and found 'new' (alternative) version waiting for me.

This SpeedM8 unit just fits behind the dash and will NOT act as a delimiter (only on the Tiptronic model - the enclosed instructions indicate that it WILL delimit non-Tiptronic 'late' models, i.e., those with non-digital odometer).

I'll try to find some time to fit it today and report back ...

Apparently no-one has ever asked for this before but the man from Speedm8 he say yes!

Like fook they haven't!!

Let me know how it goes and they can reprogram mine like I asked for in the first place.

[edit] re-reading this, are you saying you don't want the delimiting function? I'm confused. Kick down doesn't happen until about 125mph plus anyway, just don't go that fast.

Like fook they haven't!!

 

Let me know how it goes and they can reprogram mine like I asked for in the first place.

 

[edit] re-reading this, are you saying you don't want the delimiting function? I'm confused. Kick down doesn't happen until about 125mph plus anyway, just don't go that fast.

Yes (re: [edit]), that is exactly what I was trying to say. The version I had before (not SpeedM8) was trying to work the same way as the SpeedM8 VVTi Tiptronic version, i.e, fitted at the ECU to do the speed conversion function but also delimit. On my version, this led to random problems with traction control, in particular 'Snow' mode. I'm not sure if the SpeedM8 unit has this problem but I'm pretty sure that it will exhibit undesired behaviour in any systems using the converted output signal of the speedo (definitely active spoiler but may also include speed sensitive steering) unless you've fitted another SpeedM8 device to overcome this (see post above). All the uncertainty here is what prompted me to start this thread asking for feedback.

In the absence of any response and to avoid these problems, I decided that I wanted a 'simpler' unit with no delimiter function, just a speed converter function that would/could, therefore, have no effect on any other system in the car other than the speedo needle and odometer. Hopefully that's what I've got here on my desk in front of me.

I hear what you're saying about the kick-down issue and my reasoning is if I'm not going 125mph, am I bothered (with apologies to Catherine Tate) if I can't exceed 112mph? For me the answer is "No" - it's far more important to me that the car works as Mr T. intended.

N.B. If this new version does work for me (still haven't got around to fitting it), I'm afraid that if you want similar functionality, as well as reprogramming the unit, you would have to do a little rewiring too (doddle).

Shame, I've got a little device that'd convert a 1/8 signal for you and do nothing else you could've had for free.

Shame, I've got a little device that'd convert a 1/8 signal for you and do nothing else you could've had for free.

That's good of you Pete but I've looked at similar devices before and their major drawback is you also need an unconverted signal output too. Let me explain (you probably already know this but for the benefit of others who might not).

The speedo takes an input signal (SI) that is used to move the speedo needle and increment the odometer BUT it also uses this to create an output signal (4P) that can be used by 'downstream' systems that use the vehicle speed as a parameter, e.g., active spoiler, power steering, cruise control. Crucially, the input (SI) signal is not in the same format as the ouput (4P) signal but it is directly proportional to it.

This is where problems can start to arise. If the speedo input signal is converted from kmh to mph, it is reduced by a factor of (approximately) 5/8 and, therefore, so is the speedo output signal. Effectively this means that downstream systems get the reduced signal and do not operate as intended, e.g., speed sensitive power steering that should become more resistive as speed increases will do so at a reduced rate and could, therefore, appear quite 'loose' to a driver even at high speeds. Similar problems would be experienced with the active spoiler control: it wouldn't deploy/retract. until a much higher speed was attained; instead of 50mph it would be (50 x 8/5) = 80mph!

So, a 'good' speedo converter not only provides a converted speedo input signal but also an unconverted output signal, to simulate what the speedo would have generated if it had been fed with an unconverted input signal (N.B. in this respect the SpeedM8 VVTi Tiptronic version is not 'good' as it doesn't provide an unconverted output signal). A really good speedo converter would also provide a top speed delimiter (the SpeedM8 VVTi Tiptronic version does do this). If this is the holy grail of speedo converters, I'm not sure it exists (at least in a single unit).

Fitted the 'Analogue' version of the SpeedM8 speed converter today, behind the dash rather than at the ECU and, as hoped for, it works perfectly:

• recalibrates the speedo. (odo.) input signal so it reads mph (miles) rather than kmh (kilometers);
  
• leaves all other 'downstream' systems unaffected.
  
• that's it (no side-effects)!
  

:Pling:N.B. the one thing it doesn't do on the Tiptronic model is act as a top speed delimiter. If you need a top speed delimiter for this model then you require the VVTi Tiptronic version that requires fitting at the ECU but be warned this has the potential to cause problems with gear changes at high speeds (possible down-change resulting in over-revving)

I would say that if you already have the VVTi Tiptronic version fitted then unless you're really worried by the gear change problem or you're experiencing problems with steering feel, active spoiler deployment, etc. (and even these problems can be resolved by using an additional SpeedM8 unit) then it's definitely not worth changing it, particulalry if the speed delimiting function is important to you.

If it ain't broke don't fix it!

That's good of you Pete but I've looked at similar devices before and their major drawback is you also need an unconverted signal output too.

Yes, it does that.

1:1 and 1/8 output.

I've spent considerable time previously playing with this and wound up doing similar as you have, but really wanted it delimiting to use the cars full potential on track days / Pod.

I'm still convinced there is no way to get around the gear dropping issue without hacking at the ECU to feed it a none clamped signal or remove the delimiter functionality itself.

I've never experienced the kickdown and I have some really dodgy cheap converter installed that was done by the people who imported it. They didn't even splice it in properly, just cut the wire behind the speedo and ran a new one down to the unit taped to random wires along the way... nightmare when I was trying to find a speedo signal for my blitz bits. Anyway, maybe I just don't drive fast enough. Once my car kicks into 4th from WOT then I get a little hesitant that I won't be able to stop before the end of the runway

Yes, it does that.

1:1 and 1/8 output.

 

I've spent considerable time previously playing with this and wound up doing similar as you have, but really wanted it delimiting to use the cars full potential on track days / Pod.

 

I'm still convinced there is no way to get around the gear dropping issue without hacking at the ECU to feed it a none clamped signal or remove the delimiter functionality itself.

I think you're absolutely right Pete. The thing that doesn't make sense to me though is why this problem has appeared at all. If you put the Tiptronic into manual mode and try to change down (most likely accidentally) into a gear that would put the revs in the red, you get a polite beep and it stays in gear.

My feeble reasoning leads me to believe that it does this by comparing the current revs with what they would be if you changed down and it's calculating that based on the respective gear ratios, e.g., if you're in third (ratio 1:1) and you try to change down to second (ratio 1:1.531), then

N.B. I've simplified that slightly (cheated!) by choosing third (1:1)

If the 'new' revs calculated are higher than the red-line then 'BEEP'! Vehicle speed doesn't come into the equation and why should it ($64k?)?

Answers on a postcard please ...

I've never experienced the kickdown and I have some really dodgy cheap converter installed that was done by the people who imported it. They didn't even splice it in properly, just cut the wire behind the speedo and ran a new one down to the unit taped to random wires along the way... nightmare when I was trying to find a speedo signal for my blitz bits. Anyway, maybe I just don't drive fast enough. Once my car kicks into 4th from WOT then I get a little hesitant that I won't be able to stop before the end of the runway

As I kind of said before, if it works (really works - no unexpected side-effects) then don't knock it!

Seriously, it probably is the case that we just don't normally drive fast enough for this to actually happen. The problem with that argument is though, it's only got to happen once and you're engine is toast.

Not something you'll have to worry about for long with a new ECU on the way!

...

Seriously, it probably is the case that we just don't normally drive fast enough for this to actually happen.

...

I think the actual speed above which this problem may be exhibited will depend on the 'capped' speed that is sent by the speed delimiter to the ECU.

So, for example, if the capped signal is set at 110mph then I would expect the problem to only be experienced at speeds above that.

However, it is my belief that some speed delimiters set the capped speed to just 85mph, in which case the problem is potentially (worryingly) more likely to occur.

I have read that the SpeedM8 capped speed is 105mph.

So, for example, if the capped signal is set at 110mph then I would expect the problem to only be experienced at speeds above that.

Correctomundo.

Clearly the gearbox map thinks you're only doing 110 so when you're foot goes to the floor it thinks "ah, it's safe to change down now so I will". If you could feed the ECU with a real speed signal but defeat the code which limits within it then you're laughing.

I'm sure if you were an electronics buff it would be trivial. I guess it depends upon how much is programmed and how much is systems logic.

Perhaps this could be approached from a slightly different angle, maybe by working out how the top speed limit is actually achieved and 'overriding' it, i.e., what does the ECU 'do' to the engine to stop speed increasing?

I don't think it's the same as traction control (separate throttle butterfly) and it doesn't sound like fuel cut either (I've never experienced that but it sounds more dramatic than top speed limit). Just ignition/timing?

Ah! A thought has just occurred to me - could it be the drive-by-wire throttle control (effectively ignoring pedal input)?

Fitted the 'Analogue' version of the SpeedM8 speed converter today, behind the dash rather than at the ECU and, as hoped for, it works perfectly:

 

recalibrates the speedo. (odo.) input signal so it reads mph (miles) rather than kmh (kilometers);

leaves all other 'downstream' systems unaffected.

that's it (no side-effects)!

Can i ask how this converter achieves this, the input signal to the speedo i converted to miles at the speedo, so how is the output from the speedo not effected? or am i just being thick as usual?

regards colin

Can i ask how this converter achieves this, the input signal to the speedo i converted to miles at the speedo, so how is the output from the speedo not effected? or am i just being thick as usual?

 

regards colin

No, I didn't make this clear

The SpeedM8 unit is '2-Channel': the analogue version takes the speedo input signal and from that creates both a converted (kmh:mph) speedo input signal and an 'unconverted' (1:1) speedo output signal to simulate what the speedo would have output if it had received an unconverted signal. Consequently, the actual speedo output (as opposed to the one generated by the SpeedM8) is left disconnected.

Hope that makes sense!

The 'perfect' speedo converter for the VVTi Tiptronic model would be (at least) '3-channel':

1. converted speedo input signal
   
2. unconverted speedo output signal
   
3. capped ECU speed input signal (to disable top speed limit)
   

I am in posession of such a device - it's a Thor/TRL unit that has been modified by Pete Betts (genius) specifically for the VVTi Tiptronic - but when fitted, on my car at least, I experienced 'random' problems with traction control going into 'Snow' mode (Pete did try to explain this to me but I can't remember the full details - I'll dig out the e-mail if anyone's interested). Unfortunately, I think Pete has given up trying to perfect it (I've recently been informed by Thor that no more VVTi versions of their unit will be produced).

I haven't been able to ascertain whether the SpeedM8 VVTi Tiptronic version is susceptible to this problem - possibly not because it's only 2-channel (and, therefore, you'd need two of them to replicate what the Thor/TRL unit was doing). Certainly, the Analogue version isn't - it can't be as it doesn't go anywhere near the ECU.

Found the e-mail from Pete:

The problem is the VVTi car uses the ABS wheel speed sensors to work out speed, rather than a dedicated speed sensor in the gearbox.

 

The ABS sensors output a smaller level signal, A.C. (+ve and -ve) rather than TTL 0->5V pulses (like the earlier Supras)

 

So the mod is internally to the unit.

Voltage divider circuit on the input to decouple it from ground and place the mid point (zero crossing) at about 1.8V (the TTL switching threshold)

 

The result of not doing this is if the car pulls away slowly, the SNOW mode sometimes kicks in, as it thinks the car is moving the wheels but has not forward motion.

Pulling off fast would likely result in it not doing this, hence it seems intermittent.

[/Quote]

Thanks for that :thumbs:makes sense now.

Looking at the ECU pinouts for the VVTI auto

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=41284&d=1155155220

there seems to be a lot of speed sensor inputs/outputs from the rear, 3 !!! thought i only had 2 wheels back there but there is also a front speed sensor and front speed sensor (O/D Clutch), the speed delimiters only seem to be targeted at one of these, or perhaps the wrong one but it makes you wonder how the ecu is meant to work out which is correct when we limit just one of them

It's a five channel system like the UK spec.

Thanks for that :thumbs:makes sense now.

 

Looking at the ECU pinouts for the VVTI auto

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=41284&d=1155155220

 

 

there seems to be a lot of speed sensor inputs/outputs from the rear, 3 !!! thought i only had 2 wheels back there but there is also a front speed sensor and front speed sensor (O/D Clutch), the speed delimiters only seem to be targeted at one of these, or perhaps the wrong one but it makes you wonder how the ecu is meant to work out which is correct when we limit just one of them

Those pin-outs are a bit misleading (in fact the whole thing's a bit questionable): each sensor usually has it's own ground (i.e., what the sensor signal itself should be compared to) but is not labelled as such in that list (shares the same name).

It would be good to find out what mechanism the ECU actually uses to limit the speed. Now I m undecided as to whether to tell the garage to delimit the car and put up with any spurious behaviour or to go with the undelimited route, the later is winning at the moment, as 100% of the time in day to day use this wouldnt be an issue. Track or airfield would be the only issue honest officer:search: