Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

924 Carrera GTS replica tach/boost gauge
Goto page Previous  1, 2, 3
 
Post new topic   Reply to topic    924Board.org Forum Index -> Body and Interior
View previous topic :: View next topic  
Author Message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Tue Oct 25, 2022 8:18 am    Post subject: Reply with quote

OK, found the right wiring diagram, I see this that way:

Terminal 1 goes to DME / Injector PWM switched to GND.
Terminal 2 hangs in the air
Terminal 3 goes to always hot +12V (same as clock).
Terminal 4 GND
Terminal 5 switched +12V
Terminal 6 goes to the ignition coil



The tach looks like that:


and the PWM-possible-motor:



According to the service manual economiser uses speed sensor (hall) and signal from injectors (PWM to ground). When stationary it shows fuel consumption per hour. So if there is nothing on the Hg, then only by applying PWM'ed signal (switched to GND) on Terminal 1 it should move the needle... In theory.

If that works, then it's just finding the correct PWM signal to drive the needle as needed - that would be nice
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Sun Nov 13, 2022 10:25 am    Post subject: Reply with quote

One step forward:



I have one extra, so if interested PM me.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
morghen  



Joined: 21 Jan 2005
Posts: 8696
Location: Romania

PostPosted: Sun Nov 13, 2022 6:24 pm    Post subject: Reply with quote

Would be cool if you could actually just implement an oldschool boost instrument there instead of some electronic stuff.

I'd take one in green letters matching my S1 931 dials if it used just a vacuum hose as an input.
_________________
https://www.the924.com
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Sun Nov 13, 2022 9:11 pm    Post subject: Reply with quote

Morghen it crossed my mind, but I could not find a mechanical boost gauge with the scale as in this gauge (VDO makes though 50mm marnie gauge that is electronic and kind of matches this scale). Most of the mechanical boost gauge do travel like 3/4 of the full turn.

EDIT: And yes, green should be possible as well.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Sun Nov 20, 2022 4:42 am    Post subject: Reply with quote

So it looks like that. Nod bad IMHO.



Wanted to do some bench testing today, but my lab power supply died and I don't have the parts to repair it.

Just managed to see what drives the boost (econo) hand. There are 2 coils, each works the opposite direction. Providing some voltage to any moved the hand (like an oldschool voltmeter). Both directions (polarity) and both coils.

So this seems to be operating same way as 3-wire IAV that is PWM driven.

Need to hook that to my function generator, but first need to repair my lab gear.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Tue Nov 22, 2022 1:56 pm    Post subject: Reply with quote

Well I thought it will be easier, no solution yet, so few notes:

Pin 4 is GND
Pin 5 is VCC (+12V)
Pin 6 is Tacho Signal (48Hz = 1000RPM / 82Hz = 2000RPM / 120Hz = 3000 RPM / 150Hz=4000RPM / 180Hz=5000RPM / 210Hz=6000RPM) - hey it's not linear, at least in lower RPM range.

Pin HG kinda allows to control the "boost" gauge. With frequency getting higher boost goes lower (which makes sense, as it means the faster you drive with same fuel usage, the lower is the fuel usage).

Pin1 kinda allows to control the "boost" gauge, but in much less range than HG. This is odd, as I'd expect this pin (signal from injector opening) would mostly influence the hand of the clock to move, especially when stationary (litres per hour in theory).

The problem with these "kinda" is that the "boost" hand is not that much getting back to a position with boost value at same frequency when changing the signal at generator up and down. it means that "boost" grows i.e. to 1bar at certain frequency, then the frequency drops, but the hand stays same place. it will move in the end, but the frequency needs to be altered more that I'd expect.

Not sure what to do about it yet. Would be easier if I could point two PWM signals at same time to PIN 1 and HG, but that's not possible with my generator.

Not sure, maybe my Econo gauge is faulty (read people had issues with these).

Leaving that for later, unless you have any thoughts?
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Thu Nov 24, 2022 9:06 pm    Post subject: Reply with quote

Well it seems my Econo gauge is faulty. Tried to search the web for a Solution, but usually the answer is „it’s a crap, delete it”
Talked to a friend that is electronics guru and decided to convert the econo gauge to accept a „stock” map sensor from something popular, leaving the factory econo electronics alone. That „stock” map sensor (maybe VW/Audi one by Bosch) will drive the econo gauge hand according to the readings from the Map sensor (adjusted and calibrated).
Therefore I should be able to have a „standalone” MAP driven boost module for those tachos that would easily convert the Econo Gauge to Boost Gauge
Well, that’s the plan.
Need to buy a spare MAP sensor with 0-5V output and measure it properly.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
morghen  



Joined: 21 Jan 2005
Posts: 8696
Location: Romania

PostPosted: Thu Nov 24, 2022 11:00 pm    Post subject: Reply with quote

There are those small diameter pressure gauges, i've only found 10bar ones but there must be one thats small enough to be fitted inside the 924 dial and has a 2bar range.
That would make things so much easier...no electronics, just a vacuum hose.

EDIT:

Scratch that, here it is, just fit this in the box and be done with it.






https://www.ebay.com/itm/254762539941
_________________
https://www.the924.com
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Fri Nov 25, 2022 9:40 am    Post subject: Reply with quote

I want to do it the proper way Ciprian
The gauge hand won't look as it should
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Thu Dec 08, 2022 8:37 pm    Post subject: Reply with quote

Due lack of time I'm far behind where I would like to be, but...

The plan is as this.
- I will use external MAP sensor (Bosch 0261230120) that is easily available. It has linear characteristic for 0-3 bar (so max 2 bar of boost)
- The gauge will show only boost, so anything above atmosphere pressure, but in theory this could be scaled both for vacuum and boost (different gauge face needed though).
- I will not use the internal circuit that drives the econo gauge, only the two coils in the gauge alone.
- The coils have common positive terminal and work against each other with current around 3mA maxing out the hand in each direction.

This basically means it will be a "standalone" gauge and easy to install.

That's the plan
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
kondzi  



Joined: 02 Jul 2018
Posts: 384
Location: Poland/EU

PostPosted: Thu Dec 15, 2022 1:52 am    Post subject: Reply with quote

OK, found some time in the evening and did a bit more measurements.

I managed to get the gauge operating and in full scale both ways:
- Using PWM (frequency) driven inputs on PIN 1 (aka injector PWM signal) and PIN HG (Hall Ground - speedometer signal).
- Using Voltage applied to both coils.

So the pinout that worked in the frequency based test is:
PIN 1 - (88Hz with 60% DC square PWM wave 0-12V)
PIN 2 - not used
PIN 3 - Batt (+12V - always hot)
PIN 4 - Ground
PIN 5 - IGN (+12V)
PIN 6 - RPM signal (88Hz with 60% DC square PWM wave 0-12V)
PIN HG - 12Hz up to 135Hz for full gauge travel, 50% DC square PWM wave 0-12V)
PIN H+ - bridged internally to PIN 5 (+12V)

With PIN 1 being constant 88Hz and PIN HG at:
- 12Hz the hand was at 0 bar (min)
- 43Hz the hand was pointing up (middle)
- 135Hz the hand was at 1.5bar (max)

I tried different frequencies and it seems only the ones from certain range made the gauge work in predictive and repeatable way. Higher / lower frequencies or so resulted either on gauge maxing out (usually) or misbehaving (like shaking of the hand).

The other important thing is that the two coils are connected to a RED wire that is directly connected to PIN 3 (to be checked, it was late) and when this ONLY is hot, the gauge is maxing out. the other 2 wires that go to coils (green and white) needs to be negative in terms to red wire. So the potential difference in general between red and white/green is within 1.6-11V with the +12V at the red wire constant. The electronics on the circuit board provide negative voltage to both coils via green and white wires that work against each other.

Polarity is IMPORTANT as trying to drive the coils with common ground (red wire) resulted in the gauge hand maxing out to either direction, but not being able to settle in the middle (operating range). Switching to common positive on red wire made the and super stiff (won't jump when hitting a bump with a car) and pointing within the range.

There is a need for RPM signal (coil) and HG signal for the gauge hand to settle within gauge range and be driven to desired value.

For the direct coil drive the following voltage worked out:

0 BAR: 7V on the White --> Red coil wires / 11V on the Green --> Red coil wires
0.5 BAR: 8.3V W-->R / 7.9V G-->R
1.0 BAR: 9.7V W-->R / 5.6V G-->R
1.5 BAR: 11.0V W-->R / 3.6V G -->R

More to come when I find more time to play with it.
_________________
---
Konrad
'89 951 US
'88 Mustang 5.0 LX Convertible (factory specs)
'84 911 Carrera 3.2 RoW (factory specs)
'81 931 RoW (TBD)
'81 Ford Capri 2.8i (factory specs)
'79 Ford Capri 2.9 (heavily modded)
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> Body and Interior All times are GMT + 11 Hours
Goto page Previous  1, 2, 3
Page 3 of 3

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group