[gmacrae]

Hi guys, in another thread here i asked for information on how to use a zener diode in the turbo pressure sensor line to remove the boost cut.

I have a 3.3v zener diode and another diode of about .8v (couldnt get a 3.9-4.3v one). I told a friend (tv/stereo repair guy) what i was after and he came up with combining the 2.

The thing i dont get is:

How do i wire this into the tps wire? Im pretty sure it doesnt just go in line (series) between the TPS and the ecu, as in know it has to somehow dump unwanted voltage to ground...

Do i just strip a small section of the + TPS output by the ecu (but dont cut it), solder the right end of the zener diode in here, and he other end of the diode to a ground?

Thanks for any help guys - Gene

 

[BLKMGK]

Why are you touching the TPS wire?! MAP sensor! You understand what and why you're doing this right??

Umm, and how exactly will you be combining these together - they are NOT resistors. Been awhile since analog electronics but I'm not seeing how that's going to work....

 

[gmacrae]

When i say TPS i mean turbo pressure sensor, not throttle position sensor. That is the sensor the ecu bases its overboost fuel cut on right? THe same sensor the greddy BCC intercepts right?

The guy that put me onto combining the 2 really knows his stuff, dont worry about that. The diodes are connected in series back to back, dont ask me, but he tested it infront of me, worked perfect :dunno:

I think i've got it, car is running fine, gonna take a short run at 17psi and see what happens, will let ya know

 

[BLKMGK]

Okay, makes more sense now! :doh: You saw the diodes on the bench so I'll believe you but man I cannot see hpow that's going to work. If you've got this worked out be sure to post up exactly how you wire it so others can find it!

 

[gmacrae]

wil do - the good thing is i havent cut or stripped a single wire, i've actually wired it into the sensor's plug

if my extremely vague calculations are correct it should work lol, if not i spose a couple of diodes and maybe a fuse might go up in smoke...

 

[MaliCali]

carefull with this thread, as the diode boost cut mod takes away sales from BCC's so they often dont allow these threads to last very long, and be careful not to get banned because of it..

 

[swearitsstock]

ive got a spare bcc sitting in my garage... shoot me a PM and you wont have to worry bout screwing up an expensive car

 

[Jaxx]

Email or PM "quick" for some help and be done with this thread....

There's the best advice you will hear


^^

You can still screw up an expensive car by incorrectly installing a BCC :stickpoke

 

[gmacrae]

carefull with this thread, as the diode boost cut mod takes away sales from BCC's so they often dont allow these threads to last very long, and be careful not to get banned because of it..

Absolutely no offence meant to you man, thanks for the warning, but thats an absolute fucking joke. If the "sponsors" are gonna get pissed about a $1 mod doing the same job as a BCC, then make the friggin BCC cheaper!! IMO $150NZ for such a simple device is ridiculous....

ok, breathe lol

Turns out my "vague calculations" were just a bit too vague... it didnt work (surprise surprise lol)

I rigged the diodes up between the ground and black/yellow wireon the TPS plug.

It seemed to affect the fuel mix under boost, made it lean out quite bad. Im pretty sure this meant it was actually doing its job as i had intended it, but it seems my japspec car uses the turbo pressure sensor for more than just the sequential operations

 

[BLKMGK]

Whoa!!!!!!!!!! JDM uses that for it's PRIMARY LOAD CALCULATIONS! On a JDM car you do NOT screw with that - only on MAF cars

 

[gmacrae]

really? i thought the map sensor was in charge of all the load calculation stuff? As i understand it, the map sensor and the turbo pressure sensor are 2 completely seperate sensors - right?

If the computer is in fact using the turbo pressure sensor for its main source of info for running the fuel maps on my jdm car, surely it'd be a bad idea to use even a greddy bcc on a jdm car?

 

[BLKMGK]

As I understand it - and I don't own a JDM - that car has a single pressure sensor in place of the MAF and pressure sensor we run. I believe that a BCC cannot be used on those motors. Do you have BOTH a MAP and "TPS" sensor? So confused here and I'm sure I'm only making it worse for you too

 

[gmacrae]

Im always confused man, dont sweat it lol

I have the same turbo pressure sensor as you guys, thats for certain. The sensor that i always thought was the MAP sensor is screwed into the intake manifold just to the right of where the crankcase vent enters the intake manifold (when looking from the turbo side of the car). It's like a big 17/19mm hex with 2 wires, Pink/blue and brown/black.

Thanks for your responses BLK, it looks like this mod would work on the export supra nicely, if anyone wants more info on how i did it, let me know

 

[gmacrae]

wait a sec, i just remembered the turbo pressure sensor is also used for the fuel pump 9/12v switch, maybe it was just that the fuel pump wasnt switching over to 12v and not because the TPS has anything to do with running the fuel maps?

 

[Rich B]

I'd be concerned with using a zener - simply because the zener would sink current onto ground once its Vz is reached. A BCC presents a high impedance always to the pressure sensor, and draws very little current.

A BCC is pretty cheap - and if you are really chip and you know what a zener is, you might look at the MKIV writeup - IIRC it has a circuit diagram and you can put it together yourself.

My $0.02

Cheers
Rich B.

 

[bahraini_zupra]

guys ! i really wanted to know is it safe to use this diode on our maf mkiv or not ? and can somebody explain exactly how to install it and give me the DIODE SPEC EXACTLY PLEASE !!

thanks

 

[gmacrae]

Thanks RichB, didnt realize that was quite what happens, makes sense, but for the ppl that want to try it:

bahraini_zupra: OK, by the looks it's ok to use a zener diode on your export spec car. You can at least try it, just be careful when testing it, if your car seems to run under power as the turbo's are spooling (ie very lean), get straight off the gas and pull the zener the hell out. I'd also recommend at least a stoich (air/fuel) guage on the stock O2 sensor - wideband would be better.

The diode you should get is as close to 4.3v as possible, i'd say a 4.3v zener should be ok (you can get them - just not in my town) as they seem to gradually drop the voltage even before their actual rating. So a 4.3v zener would probably start reducing the voltage around 4v.

The zener doesnt seem to need much current/flow capacity (whatever it's called lol), the one i used was rated at 400mw, or just under half a watt.

so, get a 4.3v 400mw zener diode, wire it into the turbo pressure sensor plug like this:

wire the front of the zener (the end with the little band around it) into the middle wire in the turbo pressure sensor (this is the one that goes back to the ecu).

wire the other end into the forward most wire of the pressure sensor (this is ground)

I just wrapped the zeners wires round the contact then plugged it back into the plug.

You can pull the contacts out of the plug by first unplugging it, removing the white plastic bit inside the plug, then using something like a tiny flathead screwdriver to lift the tiny black plastic clips holding each contact in.

This way you dont have to damage the harness at all, and it's very easy to remove.

If anyone can spot a hole in this "method" post it up, im definitely not very 'electronically minded' and would be grateful for the input - Cheers :bigthumb:

Gene

 

[Ubermensch]

I built my own BCC a few years ago based on Bill's diagram:

It worked perfectly for years and I think it will cost you a few dollars to construct ( I had the parts in the lab so it was a freebie to me). I'm a ChemE not and EE so don't ask me to explain why yours doesn't work but I can follow the diagram :bigthumb:

 

[gmacrae]

Also, RichB: whats the article at mkiv you're talking about? IIRC? i searched MKIV.com, couldnt find anything? - Thanks

 

[gmacrae]

Sweet thanks Ubermensch