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Rich H
Joined: 10 Jun 2007 Posts: 2665 Location: Preston, Lancs, UK
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Posted: Tue Dec 08, 2009 7:36 pm Post subject: |
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Put a cheap fuel filter in the vacuum line. This will provide a reasonable amout of damping as the filter paper will resist the pressure changes slightly.
Also a capacitor to ground at each of the gauge terminals will provide a degree of damping. Start low value and then go up. Maybe an adjustable slidign plate jobbie one like DIY radio kits would be an idea? _________________ 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 |
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!tom
Joined: 28 Aug 2006 Posts: 1930 Location: Victoria, BC Canada
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Posted: Wed Dec 09, 2009 2:14 am Post subject: |
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Or a calibrated leak. Put a restriction in the line with a teeny tiney pin hole in it. That would be the same idea as the fuel filter, but may allow more control. _________________ 78 924 NA
5-lug |
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9XX Girl!
Joined: 20 Sep 2009 Posts: 1617 Location: Cornish Riviera SW England
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Posted: Wed Dec 09, 2009 8:14 am Post subject: |
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Cool ideas guys, here's me thinking this thread was getting a little lonely. But it certainly has had me thinking.
I have been looking around work for something to do the job. My boss thinks im loosing it cos i keep opening sterile surgical packs of differing equipments and blowing through "things". Even blowing up surgical gloves and attaching "things" to them to see how long they take to deflate. don't usually get out of breath at work!
Drooper holds Breath http://www.youtube.com/watch?v=2lAtefIJalI&feature=related
I now have a cunning plan with the nossal from a tube of cyanoacrylate. It's used in wound closure (Tissue adhesive or skin glue to use layman terms).
It has the tinny weenyest hole in it that you ever did see and, the nossal is tapered. I intend cut the nossal off the dispenser and insert it into some silicon hose to work as a restricter.
cyanoacrylate has a lower viscosity than water and these dispensers take some force to operate so should work.
Then i will be driving on lightest of throttle with the gauge as visual reference to help do me bit for the environment and my pocket
thrifty???? http://www.youtube.com/watch?v=z1kzBRlPfcM _________________ 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
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Posted: Wed Dec 09, 2009 9:19 am Post subject: |
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9XX Girl! wrote: | 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. |
Probably because it is a vacuum gauge rather than an econometer.
MAP changes occur very fast and even a constant cruise will fluctuate up/down at fast cycles. Can post a datalog if you`re interested in seeing what the sensor reads. A mechanical vac gauge is inherently internally dampened mechanically due to the slow responding bourdon tube.
See how you go with the mechanical dampener & restrictor idea. Damping can also be achieved rather simply electronically if that doesn`t prove effective.
Here`s an interesting article on fuel economy I came across recently, not so much the device but the theory and driving practice.
http://www.autospeed.com/cms/A_111510/article.html?popularArticle
9XX Girl! wrote: | While cursing it is possible to keep the needle of the gauge at 30 MPG |
Oh yes, swearing sometimes does make a difference. |
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9XX Girl!
Joined: 20 Sep 2009 Posts: 1617 Location: Cornish Riviera SW England
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Posted: Wed Dec 09, 2009 9:42 am Post subject: |
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RC wrote: |
9XX Girl! wrote: | While cursing it is possible to keep the needle of the gauge at 30 MPG |
Oh yes, swearing sometimes does make a difference. |
Ha har glad someone is taking note of my waffle. er i really should read what i type sometimes. Anyway, gon't go shattering my dreams (dilutions). Just trying to make my pointless car more obscure. I pity the next owner. The guy that did my MOT test couldn't stop laughing.
anyway, thanx 4 the reading, (anyone would think i have nothing better to do)
one thing i like about economic driving is.... when i do go fruit loop and boot it,... the whole car changes its personality and reminds me I'm driving a Porsche. A bit like when Kurt Cobain's Nirvana goes from a verse into a chorus "dynamics!"
Anyway, i consider myself told "not enough swearing" _________________ 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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9XX Girl!
Joined: 20 Sep 2009 Posts: 1617 Location: Cornish Riviera SW England
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Posted: Thu Dec 10, 2009 9:51 am Post subject: |
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Thats the puppy
Seems to work sweet as dampening. I never get a reading of more than 60 MPG even on overrun but thats not a great prob. It seem to display mean manifold vacuum nicely _________________ 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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emoore924
Joined: 13 Apr 2004 Posts: 2815
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Posted: Thu Dec 10, 2009 10:56 am Post subject: |
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Here in the states I think we call that cyanoacrylic "grazy glue".
Sticks skin instantly. |
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ZODIAC
Joined: 08 Apr 2009 Posts: 342 Location: West Haven, Ct
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Posted: Fri Dec 11, 2009 3:07 pm Post subject: |
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emoore924 wrote: | Here in the states I think we call that cyanoacrylic "grazy glue".
Sticks skin instantly. |
as a member of the "hand to model car club"...^+1... _________________ "Kraut cars, they know how to build 'em".
1977 924 N/A - Red with waterdamage interior
yes...waterdamage is now a color... |
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9XX Girl!
Joined: 20 Sep 2009 Posts: 1617 Location: Cornish Riviera SW England
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Posted: Tue Dec 15, 2009 5:57 am Post subject: |
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OK - yet another refinement to the PCB
Although the damping works well, i have discovered that the gauge is thrown out by the varying 12v supply, mainly because i am using the +12 supply voltage as a reference (via a cap) to stabilize the gauge. all is ok until you start using high current devices like cooling fan. heated rear window, heater, wipers etc. This causes the vehicle voltage to drop slightly. the 7805 compensates for this on the 5v rail but there is no regulation for the 12v.
Therefore, as you will see below i have added a 12v reg ic. i used a LM2904 because of its suitability to automotive applications. Road testing will begin tomorrow.
_________________ 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
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Posted: Tue Dec 15, 2009 6:00 am Post subject: |
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_________________ 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 |
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Raceboy
Joined: 01 Mar 2004 Posts: 2326 Location: Estonia, Europe
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Posted: Sat May 14, 2016 10:12 pm Post subject: |
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Bumping this topic, the circuitry posted above does control the MPG gauge directly without original electronics?
Also, was the MAP sensor used regular 0-5v unit? Just trying to figure out the suitable signal I need from VEMS unit to drive the gauge and save some time and effort. _________________ '83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche |
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