Peter Betts

****************************** Also, I think temperature is something you will not have to consider as that should already be taken care of. ****************************** Isn't the standard air temp sensor in the MAF housing so I would have to take care of it wouldn't I? Pete

************************************************ So to replace it, you need a piece of gubbins that takes in manifold pressure and RPM and processes these signals to produce a composite "air flow" signal that you then feed into the ECU instead of the MAF signal. You can estimate it by assuming turbo and intercooler efficiency of 70%. Now stick it all into a computer and plot a graph of flow - versus - manifold pressure and Bob's your uncle. ************************************************* Precisely what I needed to know. The data logging idea is also a good check of the theory. I think this is what the HKS VPC thing does isn't it? Thanks Pete

***************************** 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.

Bingo! Cheers Pete

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

A MAF measures the mass of the incoming air directly and to replace a MAF system you need to substitute with a Speed Density system which must estimate the mass air flow based on MAP and IAT. Speed Density uses RPM, MAP, and IAT to estimate air flow. So who is good at physics? If I want to calculate MASS of air flow then what calculation do I do? I have PRESSURE, TEMERATURE and RPM as available inputs to the equation. I guess we need the MASS of an air molecule and the volume of the engine? Ummm... getting woolier by the minute..... then I guess every rotation of the engine we have shifted a volume of 3lt (assuming 100% efficiency). Knowing the "gas laws" we can work out what the MASS of the air entering the engine was given the pressure at the manifold and "inlet" temperature. Is it then just a case of scaling this figure to match the frequency or voltage range of the original MAF? Regards Pete Key:----------------------- IAT: intake air temperature, which measures the temperature of the air the engine is about to inhale SD: Speed Density MAF: Mass Air Flow MAP: Manifold Air Pressure RPM: Revolutions Per Minute The IAT is also used to control ignition advance. ** Cold inlet air *** helps the engine resist detonation, so the engine can tolerate a bit more advance (the cold air tends to condense the fuel mist from the injectors back into liquid fuel, which takes longer to burn). *** Very hot inlet air *** is more likely to cause the engine to detonate, so less advance must be run to avoid that destructive detonation

Leon had loads just taking up room in his driveway. He may have had a chuck out but you never know. I kept my old system just in case. Give it 6months and I'll probably chuck it as well. I always keep the 2nd CAT though just in case I get an ar*e of an MOT guy. There are generic CAT systems which you could get couple to your flanges but the second hand route is the one to choose in my opinion. BUT you shouldn't have to pay for something that would have been thrown away. Be warned though. I found my stock system extremely restrictive. Even though it functioned really well on emmisions etc there was a collapsed baffle somewhere which made it extremely asthmatic on any boost higher than about 1.1bar. I never really noticed it until I got Hybrid turbos and it upped the boost a little. Fitted a Mongoose system and BOY! what a change! I'd always run with NO CATS but the back box was a problem so it turned out. So be warned with second hand gear.

Moved over. Appologies for wrong discussion area.

****************** I've fitted a converter just after the gearbox speed sensor, no other wiring mods ****************** So the whole car is seeing a modified 5:8 signal. **************************** however having had an HKS SLD (delimiter) fitted, the gearchange is now perfect **************************** 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? **************************** 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" **************************** 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

gs300 1993 model (toyota aristo) Anyone fitted a speedo converter or know the wiring diagram for the speed signal? I'm assuming it's a digital speed sensor signal. Anyone know of an owners group I can ask? Cheers Pete ps. sorry for off-topic query.

No. I should have been explicit. my 95 GZ Auto Aerotop does not suffer from Cruise stuck at 70mph. The 5/8 scaling mod works. Pete

************ Wanna stick a scope on an HKS 'auto' box (once it's in situ, say in 2-3 weeks)? ************ Just let me know. ************** Mine is a '93 model. Anyone else with a funny cruise: what's the age of your car? ************** Mines a 95. Pete

Ah the subtle approach of "just rip it out and bung up the hole" :-)

I agree with Ash's comments and I know we've spoken about this a long time ago :-) It is possible using the pulsing method but I'd like to know how JIC get it done. But as Paul says, at £60 for a new one (didn't know they were so cheap?) why bother. That more than covers the time spent on doing the other mods.

*************** Better to have an earth pulse applied to the pin for 5 seconds after ignition on and then removed. *************** I'd also considered such a simple solution. Not wanting to modify anything to do with the normal operation of theTRC but saving my memory and turning it off for me as I've got the RL TRC. But again never quite got around to doing it. ********************** This could be done with a simple Schmidt function, basically a tranny (Darlington?) a capacitor and resistor, but it would be nice if it was on a PCB and potted........ Pete ********************** Depends on the take up of the idea. Time is precious to us all as you know. You might get away with Veroboard design as it's only a few components. Probably use a 1" cube potting box. To give you an idea of size. I've got loads of ideas similar to you Paul but not all of them would sell in the hundreds so that rather limits what I spend my time on. Maybe I should do a Justin and pack up my normal job? Err! Not just yet. Good luck Justin by the way. What does the HKS TRC kit include then? and do they do one specifically for the Auto? Pete

Ah! But you can clock it up and roll over, and count up to the lower figure. Effectively counting down. (in an ass backwards sense) This is dodgy and I'm not telling anyone how to do it. Be warned some later Odo's do have a latch up mechanism which locks it at 999,999 to prevent just this.

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?

Also check out.... http://www.trlperformance.com/supra and click on "550cc injectors" I've upgraded a Jap Spec Supra from 440cc to 550cc without any problems, but I did use the resistor pack from a UK spec to do it. Pete Betts

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.