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I Can't See All My Gauges!
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Rich H  



Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK

PostPosted: Sun Oct 25, 2009 4:21 am    Post subject: Reply with quote

Gauge is converted, but not started on the electrics yet. The internals are almost standard, just pulled the mpg gauge unit forward on it's pins a little and screwed it to the face. The face looks terrible but that's just the flash picking up the eidted voltage gauge face.

Electrics to follow....
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
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Rich H  



Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK

PostPosted: Sun Oct 25, 2009 6:11 am    Post subject: Reply with quote

OK gauge wiring, I have found that if I put +5v onto the central pin (pin 3) then put a trimpot with the end connections to the 2 other pins and the slider to ground. it then points to mid adn the trim pot allow fine control of the needle.

Just need to work out how to apply it now...
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Rich H  



Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK

PostPosted: Sun Oct 25, 2009 6:29 am    Post subject: Reply with quote

OK revise that, 2 trim pots grnd to the other pins and +5 on the central pin gives good control. Going to buy a pressure sender tomorrow.
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9XX Girl!  



Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England

PostPosted: Sun Oct 25, 2009 9:20 am    Post subject: Reply with quote

Rich H wrote:
OK revise that, 2 trim pots grnd to the other pins and +5 on the central pin gives good control. Going to buy a pressure sender tomorrow.


OK, what value trim pots and when you say "pin 3", i amuse you are referring to the revcounter pins?
Problem i was thinking here is that may change when the rev counter is running as the electronics inside the gauge uses input from the revcounter and the hall effect transducer too calculate MPG
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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
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Rich H  



Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK

PostPosted: Sun Oct 25, 2009 6:35 pm    Post subject: Reply with quote

Nope the case pin 3 feeds the central pin direct
The trimpots don't matter, infact I have just fitted a 200 ohm resistor in place of one trimpot and a 2k trim in the other line and that gives good control. It's all about balancing the coil voltages. Pin 3 must be +ve to the other 2 pins as otherwise the gauge seems to run upside down, maybe it needs turning over....

I'm going to bring all the pins to the outer connector as most of them aren't needed in this setup and there I don't think there is enough room in the case for the pressure sender

Rich
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9XX Girl!  



Joined: 20 Sep 2009
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PostPosted: Wed Nov 11, 2009 4:00 am    Post subject: Reply with quote

Bad photos as usual but it works on the bench
If i suck like hell on the vac tube i can get the needle to move a bit.




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924 (84) N/A 2 ltr - 5 Speed - BLACK - Project (looking for 200BHP, any ideas!)
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BOTH ON THE ROAD, BOTH USED EVERY-OTHER DAY
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Rich H  



Joined: 10 Jun 2007
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Location: Preston, Lancs, UK

PostPosted: Wed Nov 11, 2009 4:10 am    Post subject: Reply with quote

now get it fitted!
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9XX Girl!  



Joined: 20 Sep 2009
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PostPosted: Wed Nov 11, 2009 8:25 am    Post subject: Reply with quote

It was dark by the time i finished bench testing it.

I only got the needle to move a bit but i have sucked on vacuum gauges before and know i can only deflect a couple of inches of mercury.

I will be road testing it tomorrow (weather permitting) as i have a day off.

Watch this space
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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
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Rich H  



Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK

PostPosted: Wed Nov 11, 2009 8:35 am    Post subject: Reply with quote

Eyes peeled
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Vince Ponz  



Joined: 02 Nov 2002
Posts: 3581
Location: Florida

PostPosted: Wed Nov 11, 2009 10:19 pm    Post subject: Reply with quote

Kinky.......
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9XX Girl!  



Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England

PostPosted: Thu Nov 12, 2009 3:44 am    Post subject: Reply with quote

Hmmm.... Hooked up the gauge and Map sensor and turned the engine over.

I haven't driven it yet as i have spent today working on my Vespa. Gauge seems very sensitive, i.e. either FSD or zero. when you turn the ignition on the gauge goes FSD, (0 MPG). When the engine is started the needle goes over to its rest position (80 MPG) As i rev it moves to half scale deflection (about 30 MPG) but stays there for quite a while before it returns back to the rest position (80 MPG).

The gauge is not fitted yet, it was just resting under the bonnet. i did manage to fit the MAP sensor to the bulkhead and plumb it to the TB but lost interest as i got the Vespa fired up (first time since buying it). runs like a dream. I took it for a spin around the compound (not yet on the road)
after i shut it of i could smell petrol! It has a vacuum powered fuel valve that doesn't seem to be shunting off and the float chamber on the carb overflows when it is not running. I have had the carb open once as it was mingging. Got the carb off (again) and am gona have a look at that this evening after tea. I'm not at work until tomorrow eve so i will see what the weather is like tomorrow. if its dry i'll fit the carb, if it rains i will sit in the car and fit my gauge. I have a early 944 speedo and temp thingey to fit too.


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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
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RC  



Joined: 25 Mar 2007
Posts: 2636
Location: Australia

PostPosted: Thu Nov 12, 2009 12:48 pm    Post subject: Reply with quote

Thats cool, and a great effort.

Accurate adjustment will be quite fine and critical. See how things are with the 5K pot. Its all experimental. Kudos for going where no man before has been willing to explore.
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9XX Girl!  



Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England

PostPosted: Thu Nov 12, 2009 1:14 pm    Post subject: Reply with quote

Thanks RC, I will keep you all updated st to how the tuning goes.
once its fitted and tuned, i will do a How-to
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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
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Rich H  



Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK

PostPosted: Thu Nov 12, 2009 6:19 pm    Post subject: Reply with quote

Nice work
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1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec
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9XX Girl!  



Joined: 20 Sep 2009
Posts: 1617
Location: Cornish Riviera SW England

PostPosted: Tue Dec 08, 2009 7:09 am    Post subject: Reply with quote

Well the MPG gauge is fitted and working. It responds quickly to changes in throttle position in all gears, (a little too quickly) and is more of a vacuum gauge than an econometer. . While cursing it is possible to keep the needle of the gauge at 30 MPG but it only takes a blip of the throttle to take the needle over to infinity, or to come off the gas and overrun snatches the needle into the 80 MPG range. It would however benefit from a little dampening although not to sure where and how.

I could put a capacitor in parallel with either the gauge our the Map sensor but that would smooth out the lows, but would cause the highs to last longer. Maybe a choke / inductor in series would sort that but have no idea on values. Also where? at the MAP sensor or gauge?

Alternatively, some kind of receiver between the MAP sensor and the inlet manifold like a paint sprayers compressor has in order to cope with maximum demand. Some kind of vessel that would withstand a couple of Atmospheres of vacuum but who knows what volume or what i could use? Large type fuel filter may be?

I have not yet tried sensing at different points in the line. I am sensing after the butterfly at the moment as there is a spear port but may try teeing off the advance/retard for the dizzy as this is plumbed before the butterfly. Also there is a port over the other side of the TB buy the bigger of the two butterfly. Maybe there is somewhere in the line where vacuum changes are less dramatic. but i don't want to go drilling and plugging holes in order to find one


Any of you guys into the physical sciences got any cool ideas???


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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
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