Hi All

At last, there is the glimmer of hope that someone may know why there is the rumour that electronic centre diff & ABS will not work. I'm not sure why Moray won't post it here, and I'm afraid I don't know how to contact him 'off-line' How do you find out someones e-mail address on here ?????

I had been going along the lines of using the speed input signal, which is fed into the engine ECU. This is derived either from a reed switch in the dashboard which is driven by the speedo cable, or from a sensor directly in the gearbox. I hadn't thought about using the ABS sensors. I'd prefer not to use as they will have a higher frequency output per wheel revolution than the speedo.

By the way - I've started on the software for the vehicle speed enhancements today, and realised that I will need some way of calibrating the unit for the differant size wheels/tyres that people run. Are there standard sizes used on the sccobys ? if so, I might provide some sort of list to choose from, otherwise I guess it will have to worked out by some other method. [Still thinking about this !!]


Andy

 

to find someones email address click on

and moray's email is moraymackenzie@hotmail.com

David

 

on the TSD rally software we have a factor that is used to convert pulse rate into wheel size.

take a look at http://www.drizzle.com/~glenn/tsd/default.htm

you will find the input hardware and software used to use the ECU speed trigger. If you need more info on this drop me a mail, Glenn is a pal of mine who lives in Seattle, very clever guy.

 

Thanks David - should have worked that out for myself really !!!

John - what is TSD rallying ? I'll have a look at that site. I've got no problem doing the conversions etc - I'm just not soo sure how to present this to the user on the laptop, so that it's not to tricky to setup. I thought that if I could give them a list of wheel sizes and they just picked the one that applied, that would be simple. But I've a funny feeling that it's not that simple. I think the gearbox speedo drive has a different ratio on some cars. I'll check this with our gearbox people tomorrow. How do you go on with this TSD software if you change wheel size etc ?

Andy

[Edited by johnfelstead - 8/18/2002 3:50:59 PM]

 

With regard to the old version diff controller. This new version is a huge leap forward. The MK I, was an 'adapted' unit (it was intended to do something else). The MK II, has been desgined for the sole purpose of being an active centre diff controller. It has features that just where not possible with the MK I. (See Johns comments above)

If you're finding that your car feels 'nervous' when you lift off the throttle or under braking, then upgrade. This was the biggest problem with the MK I - you got 0% diff load under off throttle conditions.

Where are also looking at adding enhancements to the MK II (such as road speed factors and a form of 'Launch Control'). But don't worry about missing out on these - if you have a MK II controller, you only pay the differance in cost for the upgrade.

If you have a MK I unit however, you will need to pay the full price to upgrade to a MK II as the MK I was supplied by another party.

Andy

 

Hi andy.

TSD (Time Speed Distance) rallying is a form of rallying where you are given a set time to complete a distance in a stage. You are normally set a speed of say 50MPH, and you have to drive that section bang on 50MPH. 1 second either way and you get penalised. You dont have a stage finish point that is timed, there are hidden controls mid stage that take your time at that point, so you have to keep the correct speed to within a second on a stage that may have 40 speed changes and be 200Km long!

I did a rally in canada on snow in feb, where on a 120Km stage we were acurate to less than one second over the entire stage using this software.

At the start of the event you get a calibration stage that you use to set the wheel size factor. Basically you are putting in a very acurate measurement of the wheel size. This is OTT for this aplication so a few set sizes would be quite acceptable.

the most common sizes used on the impreza are 215/40x17 and 205/50x16

 

apart from jons need for accurate speed timing I dont see why you need to accurately calculate the speed fromt he diameter of the wheel.

Surely the road speed input needs to be a relative signal allowing you to alter the map against the speed you perceive. Whether the ecu knows its 45mph or thinks it is 50mph is surely irrelevant so long as it is mapped on a car to car basis.

Even if you put in a standard wheel size, I cant imagine the variation between modded wheels etc would be significant enough to create a distinct problem.

If you are going to worry about this then you also need to consider that the take off speed signal from the gear box comes before the crown wheel and pinion meaning it doesnt take into account final drive. The speedo normally enters the final drive ratio factor in.

This means that if you create one generic unit for use on all cars (assuming you install the manual diff in a uk car) you need to accomodate into the program a method of switching between 3.9, 4.11 and 4.44 final drives.

I assume most of your business will involve modding cars already having the diff and these with the exception of the uk 22b will ll be 4.44s.

 

cruise control?

 

Hi All

Adam - I think you've made a very good point. I guess that as long as we can repeat the accuracy of the speed measurement, and it's within say 10mph of actual speed, then I guess for what we're doing with it it won't make much differance.

I've still not heard anything from the guy who thinks he knows why variable centre diff & ABS won't work together.

Cruise control ?? Is this some cryptic message ? If so, I need another clue !

Andy

 

TEG Sport,

Would it be worth investigating an alternative sensor for road speed ? I.e. actually measure road speed directly rather than drivetrain rotatations converted to road speed.

This would be especially useful for loose surfaces i.e. wheel spinning like a mad thing would give you 20mph from a gearbox pickup where road speed may only be 5mph .

I'm sure I've seen these, I think they are optical units ?

Also, are you looking at using steering input for the Diff ECU, either now or later on ?

By the way, I would watch that John F bloke, he has the habit of melting stuff

Cheers

Ian

 

cruise control for TSD rallying is what I meant!

 

Ian

When we (where I used to work) developed the active diff system for the Ford works team (still running Escorts then), we tried allsorts of things ranging from monitor all 4 wheels and take the average, through to fire a laser beam at the ground and use the doppler effect !! Never managed to come up with a 100% accurate reading though !

However, I have thought of a much better way of doing it since then - I'm not saying too much yet, but it will not matter how much slip you have, nor what wheels/tyres you are running - I will always know exactly what the vehicle speed is !! (Assuming my idea works !)

Paul - I thought you wanted me to fit 'Cruise Control' into my diff controller - I did think it was a bit of an odd request !!

Andy

 

Andy,

if you have any novel ideas,

I can recommend a good patent attorney!

 

How about GPS??

 

GPS is way inaccurate - and most sat nav systems use a speed signal (inc tyre/wheel sizes) to make it "more" accurate

 

GPS on its own it inaccurate, but with the combination of some maths and also measuring the doppler shift in the GPS signals you can get very accuarte speed and location information.

 

actually I think you will find they use a speed sensor when the gps signal goes down as a back up, they combine this input with a 2d accelermeter top determine where they are when gps goes down.

the more advanced items like pioneer have a 3d accelerometer sop can cope with underground hills!

gps speed sensing is actually now very accurate indeed.

 

They use GPS positioning to shift the gears on F1 cars, it's acurate to a few cm's.

 

John,

You jest ?

 

Sure GPS is accurate but I was told there was a load of latency built in.. I maybe wrong though !!!

 

No, i dont jest! The gearchange is pre-programmed into the cars before the race now, they pick their shift points based on GPS position. One of my mates worked on this for one of the top F1 teams.

 

So using traction control and automatically shifting gearboxes that know where to shift is now ok... please can someone remind me why these F1 drivers are paid so much? Surely they sould be paid less now that all the loud pedal and shifting functions are computerised... all they have to do is turn the wheel and press the brakes now and then... unless those are also gps controlled now?! Still, it certainly adds fuel to the "Rally drivers need to be more skilled than circuit drivers" argument.

 

Is the central diff in version STI 7 (RA spec C) based on diff from Type R? Is possible to map central diff on this car?