Digsy

Reading the one-touch window thread prompted me to post this about something I had been thinking about for a while: Is it possible to wire up a converted rear fog lamp with a new-style switch that un-latches when the tail lights are turned off and on again (a'la most new cars these days). Speaking as a pathological hater of people who leave their fogs on for days after the fog has cleared up, this technology can only be a good thing! I wondered whether you could somehow loop the fog lamp feed back to the +12v side of the relay coil so that it would stay on even when the switch was released, thereby allowing you to use a momentary switch (yeah, I know it has to be illuminated - I'm working on it). I need to draw the circuits out I suppose. Sounds like a good way to short something to me. Any ideas, anyone? Darren

Just my twopenn'th worth. Additional fuel injectors are sometimes used in production engines. The Lotus 3.5l V8 has eight sequential "normal" injectors hovering over the intake valves and an extra two injectors in the plenum just downstream of the throttle body. Interestingly, these are actually there to keep the intake air cool (through evaporation) and they only come on at full boost when the intake air is hottest and there is a risk of knocking. They are of course correctly mapped into the ECU. Even more interestingly, you can get big increases in power if you put the fuel injectors BEFORE the turbine compressors. The reason has something to do with therodynamics which my brain is far too small to understand, but it does work, at least in a "development" environment. No idea what it does for emissions and the durability of the turbos though, although I can hazard a guess... Regards all, Darren

Cheers Ash! Did I ever tell you what a top bloke you were? Mine will be a pre-VVTI auto. I'll be in touch when I find out more from JIC. All the best, Darren

Ash, just planning for the future here... If JIC say they will not delimit my car using the HKS box (or equivalent) and I opt to do it myself, could you photocopy or scan the fitting instructions and mail or e-mail them to me so that I can have a trial run without buying the part first? Cheers, Darren

Pete seemed sold on the "divider" method last time I corresponded with him, which is partly why I'm so surprised that there is such a consensus over using the HSK SLD this time around. I have just talked to Steve at JIC. I sent them a letter with my deposit cheque outlining pretty much the same concerns as in my original post (but with no conclusions as to which way to go). He is going to pass it to the garage that does their conversion (anyone know who this is?) and then give some feedback to me. Darren

Hi (again) Ash! I'm fairly comfortable with a soldering iron. I didn't really want to rip the dash off my car to get to the ECUs but if they are easy to get to then it sounds fine. Hopefully the correct wires are easy to identify? I'll check it out with JIC, but I am almost certain they just wire up the ECU to the speedo divider. I don't want my odo converted anyway. I'll ring them this week to find out and let you know what they say. I would like to read up a bit more on the HKS SLD. Where can I do that? Do they have a website? Cheers, Darren

Hi again Ash, Thanks for the continued replies. This is actually just what I wanted to hear. I don't like the sound of using the speed divider to delimit the car one little bit either. So this begs the question, how difficult is the HKS SLD to fit? If I'm thinking in terms of time, would it be worth asking JIC to fit one or is it so easy I could do it myself? Where does it fit, etc, etc? If its easy to do I'm thinking of not having the car delimited at all, but living with it for a while and then (probably) delimiting it myself. Oh yeah - dumb question: How fast can a LIMITED car go? Is it 120mph? Regards, Darren

Hi Ash, Pete Betts seems (according to his website) to be an advocate of also using the converter (divider) to delimit the car. Since I do not want to have my odo reading in miles it sounds like I need to just use the divider unit to convert the speedo and then get the HSK SLD to work its magic on the ECU and auto box. This sounds like method (2) to me. Interestingly (and at risk of this going off-topic) I also hear that if you ONLY want the speedo to be converted to mph, and something else is handling the delimiting, the easiest way to do it is to buy a UK spec speedo head. I need to get to the bottom of this. Which method does your car use? Darren

Right-ho. First off, sorry for the long post. I know this subject has been covered before on and off but I wanted to get all of the information I have learned from you guys together in one place so that a final verdict can be delivered. Everything I know about delimiting has been gleaned from you guys, so you only have yourselves to blame is any of the information below is incorrect! I am also familiar with the technical data on Pete Bett's' website, which was very helpful in understanding how the speed sensor signals are used throughout the car's systems. Here is what I know: There are two main ways to delimit a MKIV. 1) Use the speedo converter (speed signal DIVIDER) to fool the ECU into thinking the car is going at 5/8 of its true speed all the time. This is especially easy if you want the odometer to be converted to record miles instead of km since the ECU and the other speed-sensitive systems all take their speed signal from the odometer. Therefore if you divide the signal going to the odometer you also divide the signal to all of the other systems (its not quite as simple as that, but please read on). Note that this method does not actually delimit the car as the limiting software in the ECU is still active. Since the car thinks it is going at only 5/8 of its true speed, the speed "seen" by the ECU never gets high enough to trip the limiter. Hey presto - an effectively delimited car. I gather that most importers use this method because you get it "for free" with a speedo / odo conversion. With a little more perseverence and Pete Bett's diagrams you can also take the divided signal from the speedo converter and only wire it into the car systems that you really need to. This is especially useful if you want to fool the ECU and also raise the cruise control trip-out speed, but do not want systems like active aero and speed-sensitive PAS to respond atthe wrong speeds (as these both require NON-divided signals straight from the speed sensor). The odo can also be left to read in km if you want. However, there appears to be another way... 2) Use a true speed signal limiter (speed signal "CLAMPER"). This is a second "black box" which operates differently to the signal divider used to change the speedo from reading in kmh. Its allows the speed signal from the sensor to pass through unaltered until it reaches a threshold which is just below where the ECU would normaly step in and limit the car's speed. After this point no matter how "fast" the input signal is, the output from the clamper unit will always stay just below the limit threshold. This unit is obviously only connected to the ECU. This would seem to have the advantage of keeping the other car's systems unaffected and all working at the right speeds. Yes, you still need a separate speed divider to convert the speedo and yes you must still supply a converted signal to the cruise control ECU if you want to remove the trip-out limit on that. There is also apparrently a third "cheapo" way to delimit the car AND convert the instruments in one go - put a signal divider straight onto the speed sensor. From what I hear this has so many bad side effects that it should not even be considered. So assuming I've got all the above right, I now have a few questions: a) I've heard that the Supra in fact has TWO engine speed sensors. Using method (1) means that the two signals will NEVER agree since one is always divided. Using method (2) they will only not agree above the limited speed. Does this cause any problems? b) I would guess that the ECU needs to know the true vehicle speed for other reasons than just to limit its top speed. If it is constantly fed the wrong speed will this make the car run incorrectly? For example, if the car uses the engine RPM and roadspeed to work out which gear it is in, it will always get the wrong answer. c) What about the auto box? Doesn't the kickdown need to know how fast you are REALLY going? I drove an NA auto that had been converted using method (1) and the operation of the kickdown seemed very strange indeed. When I buried my foot, the car just sat there screaming for about two seconds, then launched off towards the horizon. When I drove my in-law's Merc a few days later I noticed that the box dropped a cog before the revs started to wind up. d) If anyone has direct experience of method (2), how much are the clamper boxes? I've been told £200 or so, fitted. e) In short - WHICH METHOD IS BETTER???? I know one is free, but I want to know the warts-and-all effects, including the ones that might not be immediately obvious (like the affect of delimiting via the odometer on the PAS). ECU error codes? Cruise / kickdown problems. Etc, etc, etc... I need to get a consensus before the end of the month when I go to JIC to look at my car. Thanks in advance, and hopefully you will put me right if any of the information I have above is a little wide of the mark. Cheers, Darren