Breaking the 120 MPH barrier (bis)

[Guest Ash]

 

 

There are very few people who REALLY know their way around the MKIV. Of course, like with anything, there are those who claim all kinds of stuff which turns out to be largely BS at the end of the day.

 

Problem is, these days cars are very sophisticated machines. To truly know what is going on with the MKIV, you need to understand electronics engineering and mechanical engineering to quite a high degree *and* have the time to take the car apart to see what is going on. Which also means you need the tools.

 

Tools used to mean all kinds of mechanical contraptions designed to remove fasteners, and so forth. But these days, you simply cannot do without electronic equipment such as a decent sig-gen and oscilloscope; data-logging equipment, etc.

 

I'm not any kind of commercial outfit, but if I were to have to replace all my tools tomorrow the bill would *easily* be over £20,000 (probably more like 30K).

 

That's the kind of investment that even a hobbyist, such as myself, has to make in order to perform tuning and other modifications to a decent standard.

 

Another problem is, good people tend to be booked up *long* in advance. Not only that, they are usually involved in the racing side of things... as opposed to (what they would see as) basic, run of the mill stuff.    

 

Yours,

J

 

 

[Simon]

Ash, I understand and realise the technical aspects of todays modern car, that why I stopped rebuilding my cars when I realised I didn't have the electronics knowledge or the time to get the knowledge, which actually bugs me a bit. But anyway, if Paul gets to the bottom of this and I can't understand what needs to be done (other than adding/removing wires etc, then I would welcome (and pay for) the expertise to help. It seems that your very busy, but would you recommend anyone else (mail me off list if you prefer)

 

[email protected]

[Paul Booth]

 

In other words, Ash is really expensive 'cos he's got a wife and scope to support :biggrin:

 

[Simon]

Yeh, I know that need for cash, wife, kid, dog, fish, snake, 2 supras (MkIV and a Mk3), a Trooper and moving house.

[mark brown]

I thought I'd just add my thoughts to this conversion/delimiting thread as I too has loads of aggro. Mine is 1994 GZ auto import. I've fitted a converter just after the gearbox speed sensor, no other wiring mods. ODO reads in miles and speedo works correctly. No problems with cruise control either works from 40 mph to 120 mph and the car is delimited, well up to 180 mph. Problem was gearchange was a bit iffy, however having had an HKS SLD (delimiter) fitted, the gearchange is now perfect.

 

Just a quick question, if I was to remaove the converter and leave the HKS SLD in place, fit a UK speedo and ODO, would everything work OK including Cruise Control, its just I am not a fan of these add on "boxes"

 

Mark Brown

[Peter Betts]

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I've fitted a converter just after the gearbox speed sensor, no other wiring mods

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So the whole car is seeing a modified 5:8 signal.

 

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however having had an HKS SLD (delimiter) fitted, the gearchange is now perfect

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I'm unsure how this would have solved the problem unless you were able to get the original speed signal to the gearbox unit?

 

Can you remember how it is finally wired in now? Anyone got the instructions from a SLD for an Auto?

 

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Just a quick question, if I was to remaove the converter and leave the HKS SLD in place, fit a UK speedo and ODO, would everything work OK including Cruise Control, its just I am not a fan of these add on "boxes"

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In this senario no signal is altered. The Speedo and Odo just INTERPRET the signal differently for UK spec MPH but the Cruise will be seeing the original signal now and hence will only work up to 70mph. The top speed limiter of 180kph will remain in place BUT because you've fitted a SLD this will now be removed.

 

So almost right, just the Cruise wouldn't function as you'd expect I my diagnosis.

 

As I said before I'm remaking the speedo converter units I make and as it's PIC (microcontroller) based I can change anything I like and add new output signals so if a true speed limiter output is required then I'll add it (the PCB is a generic design of mine only the SW changes)

BUT analysing the SLD operation in the AUTO will be the key to all of this.

 

Pete

Pete

 

 

 

 

[Guest Ash]

 

 

Mark............

 

You haven't taken account of your air-con amplifier and the PPS, both of which will now be receiving a signal with a frequency of 5/8 of what they should be receiving. I take it you haven't got the active spoiler as if you had it wouldn't be operating at the correct speed and you would have mentioned it.

 

I also note that feeding the ECU with a divided signal caused your iffy gearbox.

 

Pete.........

 

The operation of the auto SLD is *much* more complex than the manual. There are many more wires going all over the place. I've no idea what it is doing as I've given up messing around with the stock stuff; because I decided when I get the engine back together in my car, I'm simply going to replace the ECU and design some kind of interface between the new ECU and the auto-gearbox ECU.

 

Generally, I am surprised this thread has attracted so many posts when the speed and odo conversion is *so* darned simple to implement by anyone who can use very basic tools. Pete and myself have explored the pros and cons of every avenue to do with speed conversion and the data is published on Pete's website for all to see.

 

The only thing Pete does which I cannot recommend is to feed the ECU with the divided signal. This is because I've have reports from owners who have felt their auto box feels a bit iffy during changes when you do this.    

 

Basically, all you need do is to feed the speedo and odo with a divided signal, cut the odo re-broadcast wire and feed it with the original speed signal; and if your cruise stops at 70mph then feed the cruise ecu with the divided signal also. That's all there is to it. If you wish to remove the speed-limiter then simply fit the HKS SLD... and there you have it, job done.

 

If you are feeling brave, then you can replace a couple of surface-mount resistors in the odo to make it read miles and/or display a MILES icon. In which case there is no need to re-route the odo re-broadcast wire.

 

Paul has mentioned about the pulse-shaping of the re-broadcast signal: while he is technically correct, it's strictly not necessary. I have monitored the pulse with an oscilloscope, before and after connection, and while the rise-time is slightly affected it's nothing to worry about.

 

Another simple way is to feed the speedo only with a divided signal and replace the odo with a UK unit and clock it with a sig-gen to the equivalent number of miles.

 

Yours,

J

[Peter Betts]

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The only thing Pete does which I cannot recommend is to feed the ECU with the divided signal. This is because I've have reports from owners who have felt their auto box feels a bit iffy during changes when you do this.    

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I agree it's not perfect but as we said before no one gave me hard evidence that it was a problem. Maybe only now people are seeing the effects? I was a cost thing only, why buy another de-limiter if scaling works. That's the key.... scaling does work to raise the limit but other effects are now being presented.

This is why I'm keen to add the correct output signal to the new units to sort this out once and for all.

 

 

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then simply fit the HKS SLD... and there you have it, job done.

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But what I cannot yet understand is whats wrong with just sending the unmodified signal to the auto gearbox and also to the ECU but just clamp the frequency just below the speed limit threshold on the ECU input?

I think this should work and not affect the gearbox unit.

 

What the HKS SLD does sounds a lot more complicated than that.

 

Pete

 

[Paul Booth]

As I said before I'm remaking the speedo converter units I make and as it's PIC (microcontroller) based ....

 

A man after my own heart. Are you using the newer pretend 8051 models or the original models for *real* programmers.

 

[Paul Booth]

Generally, I am surprised this thread has attracted so many posts when the speed and odo conversion is *so* darned simple to implement by anyone who can use very basic tools. Pete and myself have explored the pros and cons of every avenue to do with speed conversion and the data is published on Pete's website for all to see.

 

and BTW y'all, this thread *was* about my (and others) having a 120MPH speed limit.

 

I personally only got involved in the speed delimiting issue when I felt I had to restore my car to original spec and then perform a decent KPH/MPH conversion, which entailed the modification to speedo *only* with 8/5, a UK odo and the HKS SLD for everything else.

 

Once I've done that, that's when I get to see if I've cured the original problem and whether I still need a trip to sunny Ash Towers.

 

Please note the thread title "Breaking the 120 MPH barrier" not "How to delimit correctly".

 

NB

Rise time *can* be critical to some circuit designs. As you pass threshold voltages, often needing to pass the unstable point in under X ns as a function of the circuit's AC characteristics.

 

There's also the matter of load handling (fanout) of the speed sensor. Can it handle the ECU stack or is the buffer amplifier in the odo used for that purpose (rhetorical, only having detailed spec on the components used would answer that, plus Toyota are not required to stick with the same component on each car if another meets the design tolerances).

 

I'm not going to risk feeding the ECU stack with a signal which collapes under changing load conditions which are outside of its design spec. Sensor No 1 was not, as far as I know, designed to drive the ECU stack directly, otherwise why have the buffer amp in the odo.

 

In this case, I'm going by the book. I'm the one with the 120MPH ceiling.

 

[Peter Betts]

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A man after my own heart. Are you using the newer pretend 8051 models or the original models for *real* programmers.

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Microchip PIC16F84 running at 10MHz, can source 25mA or sink 20mA on each output.

I've got other designs with PIC16877's.

All Flash programmable which is nice.

8051? Guess I'm not a "real" programmer then :-0

 

Regarding your fanout issue of the Sensor Number 1. This is why my next speedo converter unit (already built 4 prototypes) has a 1:1 scaled output, a 5:8 scaled output and maybe a 1:1 scaled but frequency limited output. ALL with +/- 10% calibration in 16 steps.

 

That should sort most things out I think.

 

[Paul Booth]

Quote: from Peter Betts on 1:07 pm on Sep. 4, 2001[br]*****************************

A man after my own heart. Are you using the newer pretend 8051 models or the original models for *real* programmers.

*****************************

 

Microchip PIC16F84 running at 10MHz, can source 25mA or sink 20mA on each output.

I've got other designs with PIC16877's.

All Flash programmable which is nice.

8051? Guess I'm not a "real" programmer then :-0

 

Regarding your fanout issue of the Sensor Number 1. This is why my next speedo converter unit (already built 4 prototypes) has a 1:1 scaled output, a 5:8 scaled output and maybe a 1:1 scaled but frequency limited output. ALL with +/- 10% calibration in 16 steps.

 

That should sort most things out I think.

 

It'll work *brilliant* on the manual boxes.

 

On the auto front, let's see what comes off the HKS SLD.

 

I'm mad curious myself. It'll open up so much insight into what's going on with the Engine ECU and the ECT ECU. Hopefully, it will give me some clues as to how to remove the TRC ECU completely.

 

[Guest Ash]

 

 

Pete..........

 

Sorry, in my previous post I'm confusing the HKS FCD with the SLD.

 

The auto FCD is the one with a zillion wires. The HKS SLD just has +- and speed-signal in/out.

 

Yours,

J

 

[Guest Ash]

 

 

 

Pete (again)..............

 

Clamping the speed-signal frequency to a level just below speed-cut is the best way IMO. The negative reports I've had concern the actual gear changes, which isn't really an issue at 120 mph+.

 

Yours,

J

 

 

[Paul Booth]

Quote: from Ash on 2:03 pm on Sep. 4, 2001[br]

 

Pete..........

 

Sorry, in my previous post I'm confusing the HKS FCD with the SLD.

 

The auto FCD is the one with a zillion wires. The HKS SLD just has +- and speed-signal in/out.

 

Yours,

J

 

 

Except on the auto box version where the HKS SLD has a zillion wires.

 

 

[Guest Ash]

 

 

Yes, Paul is right and now I'm double wrong.

 

Okay........ the HKS SLD for the auto has 16 wires (not a Zillion ) and the man SLD has just 4.

 

I don't recommend the HKS FCD for any car as it leans out the fuelling.

 

Sorry, I just flipped for a moment and got my 3 character abbreviations mixed. Thank-you, Paul, for setting me right.  

 

Yours,

J

[Paul Booth]

Quote: from Ash on 2:06 pm on Sep. 4, 2001[br]

 

 

Pete (again)..............

 

Clamping the speed-signal frequency to a level just below speed-cut is the best way IMO. The negative reports I've had concern the actual gear changes, which isn't really an issue at 120 mph+.

 

Yours,

J

 

 

 

Now this is *exactly* what I believe and I'm hoping to prove once I've got the HKS SLD on board.

 

Using my car as a testbed run it through it's paces with the HKS SLD, then drop in Pete's 1:1 frequency capped board and see what difference it makes.

I used to have a PC based chart recorder but I'll bet money (mine too) that I can't find it now I actually want to use it.

 

Of course, if I'm wrong about the frequency limiter (they wouldn't put that many wires on it for nothing would they? Those who know my opinion of Japanese programmers know *my* answer to that one) I will still have a working HKS SLD fixing my problem (quick, find me a piece of wood to touch. Ah, mein Kopf, of course).

 

[Simon]

Paul, one more check to do tomorrow, but I think my 120 limit had more to do with a light right foot. Saw 130 briefly this evening - on a private road of course - Cruise operates from 25 - 70 all speeds as indicated on the speedo.

[Paul Booth]

Oh I can achieve 130MPH, if I've got 1-2 miles to do it in.

 

[Rich J]

Been follow this thread for a while and can't work out what the speed cut problem with the Autos is supposed to be. my J-spec Supra TT GZ Auto had speedo in MPH, ODO in MPH, Active spoiler working fine, Speed related PAS working fine, No cruise on mine (odd for a GZ but that's Jap options for you) all using one speed divider and Pete Betts website instructions. And my car was often over 120MPH (got it to 160MPH once), so why does the HKS SLD (for Auto) have 16 wires, and whay are they needed?

 

Rich

[Guest Ash]

 

 

Rich........

 

Fact is, no-one really knows because no-one has yet got to the bottom of what, exactly, the auto box ECU is saying to the engine ECU.

 

I *will* get around to it, eventually, as I have decided the engine ECU on my car has got to go. But I *do* like the auto box. So at some stage I'll have to work it out.

 

All I know is that HKS produced an SLD that they say was manual only. But UK dealers fitted them to autos. However, an informed source at HKS (I do have my moles ) has told me directly that said fitment was *not* recommended by HKS.

 

So there we have a case of HKS head-office saying that they do not recommend something their own UK dealers are fitting.  

 

Then, sometime after they brought out the manual version SLD, an auto-version SLD appeared. This unit has *loads* of wires connecting all over the place - as opposed to the 2 wires +PSU of the manual version.

 

So something MUST be VERY different about the cars because the two SLD's are VERY different... and that's all I have to go on at the moment.

 

When I put the question to HKS, all they said was that they were aware UK dealers were fitting the manual-version SLDs to auto cars but that they (HKS) did not recommend it. The person I spoke to further stated that they had made a specific request to their engineers in Japan for an auto SLD. This did (eventually) come about: which is the unit currently on sale for the auto.

 

So yes, I wholeheartedly agree, it is *mighty* confusing.

 

Yours,

J

[Phil Wall]

I have an auto box (which I think is very good), a JIC conversion box, no spoiler and no cruise, miles on both odo and speedo  The car pulls like a train at 170+, with still more to go but not got there yet.:biggrin:

 

My JIC box has the remains of a removed sticky label, I wondered if it was a Pete Betts unit!!!!

 

[Paul Booth]

As per the earlier, can people who have *no* problems let us know the year of the car and like wise for those who do. With what little eveidence we have so far, K reg might be the problem.

 

[Rich J]

Mine was late 95 N, Speedo and ODO convertion done by Eurospec (Camberley), I ran an extra wire from the Speedo divider output to the ECU (cutting the ECU standard output). Hope this helps.

[Phil Wall]

Mine is M. Left the factory July 1995.