924Board.org

9XX Girl! · Posted: Thu Sep 24, 2009 10:57 pm Post subject: I Can't See All My Gauges!

Hi All

l, I'm new to this forum and i don't see many women here so please go easy on me.

I have owned a 84 924 (UK) for over 12months now. I do about 17,000 miles per year and use the car daily. It is very much a rolling restoration.
It now has (among many other upgrades) 944 TURBO body panels/bumper etc. and 16" Compomotive split rim wheels. A whopping 16"x10 (255/50/16 tyres) on the rear, and 16"x8" (225/55/16 tyres) on the front. Most jobs are now done (interior now finished) and its just a case of keeping it all together and maybe getting a re-spray at some point. I do all the work myself other than i buy in the painting.

Anyway, the reason for this topic. I cant see all my gauges! The temp gauge is a real bummer cos i just cant see the important upper most bits (i have had coolant issues - solved now). It would be better to not see the fuel gauge as running out of juice is easier to solve than over heating.

These are important issues so, in order to see the temp gauge more clearly, i swapped the rev counter and fuel/temp gauge& warning light cluster, over. I.e. the rev counter is now to the left of the speedo and the fuel/temp gauge & warning light cluster is to the right of the speedo. I had to extend the wiring for the rev counter (shrink sleeve / soldering iron / crimping tool etc.) but no problemo!

Now i cannot see the upper limits of the rev counter i.e. the 5K rpm up to red line, (not that i spend much time in that range) but, i do like things just right. So the area that is now obscured is the 9 o'clock to 1 o'clock positions. To solve this i am thinking of fitting a 944 (per 1985) yellow rev counter. This tacho is zeroed in the 2 o'clock position and red lines (or yellow lines as the case may be!) in the 9 o'clock position. This will solve the vis issue.

http://cgi.ebay.co.uk/Porsche-944-Yellow-Digit-Rev-Counter-up-to-1985_W0QQitemZ220291853698QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item334a6aed82&_trksid=p3286.c0.m14

Now this clock has extra pins on the back as it also incorporates a "econometer"! (an naturally i want this to work). I can imagen the responce right now "mad woman - 924 N/A is mechanica fuel injection so can't be done!"
But i do like a chalange.

I can sort the rev counter bit.
i.e.
unmarked pin = (-) ground
pin 2 = +12v feed (ignition switched from radio relay)
pin 6 = pin 1 of coil

see... (part 4 page 2)
http://www.pelicanparts.com/944/electrical/944_electrical_diagrams.htm

It's the "econometer" marked in MPG that I need to know more about.
This appears to make its calculation via the 4 square wave pulses that come from the Hall Effect Transducer on the back of the speedo (or should i say odometer), and blend "other info" with it, to display Miles Per Gallon. Luckily my speedo (being an 84 924) has a Hall Effect Transducer on the back. Just needs connecting to pins "HG" and "H+" of tacho/econometer.

Now the "other info" bit! Some of that info will be revs (but that is done internally so no worry there!)

pin 4 of the tacho/econometer gets info from the coolent temp sensor (so no worry there, just link a wire from back of temp gauge)

pin 1 of the tacho/econometer is a different story. On thre 944 it gets a signal from pin 11 of the ECU. Considering the tacho/econometer is coping with Mathematics in an electronically jiggery pokery sort of fashion. This might be (at a guess) a +5v TTL supply???? Any info would help!

pin 5 of the tacho/econometer - this little puppy gets pulses from the injectors. OK easy on the 944 cos it has electronic fuel injection.
924 N/A has mechanical K-Jetronic (nice) so... i need to make a way of getting some "injector like" pulses up to pin 5.

Any ideas welcome. I was thinking along the lines of the way the D-Jetronic worked in the 1960s Porsche 914 "Speed-Density" Fuel Injection system.

Other D-Jetronic Cars

Early Merc. 280E
Early Merc. 300
Early Merc. 450/450E
Porsche 914E
SAAB 99 EMS
Volvo 1800E, 164E
VeeDub Types 3, early 4.

D-Jetronic uses a simple Vacuum pressure sensor to calculate correct injector pulses from the changes in inlet manifold pressure. After all, this is how the timing is avanced and retarded during acceleration at the dizzy.

I was thinking of using a "pre ignition vacuum sensor" or MAP sensor such as a 19204S found on modern cars such as
VAUXHALL / ALFA ROMEO / VOLVO / GM / CITROEN / RENAULT / KIA / HYUNDAI. These sensors can be found on eBay for only a few English Pounds. (Cheep as Chips!)

http://cgi.ebay.co.uk/RENAULT-MAP-SENSORS-GM-TYPE-BARGAINS_W0QQitemZ180407508563QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item2a01201e53&_trksid=p3286.c0.m14

It will fix to the bulkhead in the engine bay and get a vacuum feed from a "T-fitting" that i will splice into the existing pipe between the Throttle Body and the Dizzy.

The sensor listed above has three pins. (don't have pin out-data yet)
Supply Voltage 5.0 +/-0.5 VDC
Ground (-)
Output Voltage 0.25 to 4.85 VDC (5VDC at full excitation)

So any ideas and info are welcome as to how i will turn this signal into injector pulses to drive my eco-gauge.

Thanks muchley

Paula
_________________
924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

Scorpio · Posted: Thu Sep 24, 2009 11:24 pm Post subject:

have no idea, but thought ide jump in and be first to say hi to the new girl ..HIIIIII

p.s looks like a lot of work to see your gauges.. Ive just changed all my faces with white faces..then again the tacho prob wont work with ford edis...
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

Vince Ponz · Joined: 02 Nov 2002 Posts: 3581 Location: Florida

Get a two spoke steering wheel and then turn the gauges so you can see the red line spot on the top. reverse the two large gauges., put the one on the right at the left and the left on the right.
Are you a tall gal and looking at the gauges lets the steering wheel get in the way. You can lower the seats if you have the little alum risers. Remove them.

Welcome my number is 214 444 8732. Hey I could try.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

9XX Girl! · Posted: Fri Sep 25, 2009 3:22 am Post subject:

Thanx 4 the welcome.
That is just the type of answer i should have expected form the other side of the pond.

Are you aving a Giraffe???!!! Steering wheel is already a two spoke and gauges are already swopped over (if you can read the small print).
No alum risers on the seats either. Someone got there before you. I had to remove them to get the 911 seats in.
And i can't be doining with wonky gauges. No no no no no no!
This is Cornwall not New York, no road is flat, no road is straight, and single track roads have a 60mph speedlimit. There is enough wonkyness in the surroundings over here. It's all got be just right! just look at our drivin conditions.

http://www.924board.org/viewtopic.php?t=30383

No wonder the Germans didn't sell the 924 in the US after 1982 if you want to make all their gauges wonkey.

_________________
924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

Rich H · Posted: Fri Sep 25, 2009 7:16 am Post subject:

Wow you do like a challenge!

I like your thinking and I hate things wonky and not working in my car, as for the econometer wiring I suspect you might be in for a long fight to work it out. I'd get it on the bench and squirt some signals into it and see what happens.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

9XX Girl! · Posted: Fri Sep 25, 2009 7:50 am Post subject:

yer, i'm looking at single point injection systems as they usually measure vacuum and then fire one injector in the throttle body or plenum chamber.
I only need the vacuum sensor and amplifier unit. I'm sure i will think of something, but i want to keep it as small and as light as pos.

I have not yet got any of the parts together as yet, its all theory at the mo but, i could end up with a car capable of EFI but doesnt use it.

I will get the rev counter fitted and extend the terminals i want to play with out from under the dash and into the passenger foot well so i can try stuff. The problem with having it set up on a bench is, i would need a speedo running to fire the Hall Transducer input and a ign coil firing away too. Not easy on a bench!

Finding someone with a pre 85 944 so i can take some measurements would be cool!

I happen to notice from your sig you have a S1 landy. 10years ago i restored a 1956 S1 88". Funnily enough it was the 112nd 88" to come out of Solihull. Fun times! all asbestos linings and leather oil seals.

_________________
924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
924 (81) N/A 2 ltr - 3 Speed Auto - SURINAM RED (Metallic) - Near Original Spec (sticking with originality)
BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY

Rich H · Posted: Fri Sep 25, 2009 7:23 pm Post subject:

Come pay us locals a visit:
www.porsche924.co.uk