Deck lid ground strap- why?

[Roland Kunz]

Hello

Well somewhere in an other threat someone mentioned Faraday.

Radiofrequencys are traped inside a closed metall box. If the box has some small holes the frequenzy partialy escapes.

The Bürzel is like an open Barndoor.

The grill is like an open window. Early grilles where made from aluminium and did leave only small holes.

The RS and later plastic grilles have a high graphite containing mixture. But Porsche used later shielded ignition wires so I think those grills didn´t work like they should.

A leakage will not hurt the car, maybe you will have some noise in your radio.

But it can generate problems in electronic devices and disturb receiving from usable signal bands.

Grüsse

[Superman]

I've had the experience Warren describes and can make this statement: I will never, ever touch the following items while an engine is running: ignition wires, distributor cap, spark plug connectors, coil. Never, ever.

------------------
'83 SC

[Roland Kunz]

Hello

Well I have an old VW repairbook ( A Westrup ) from the 50`s and they had a chapter about radios in beetles. They showed how to make the nearfieldsupression becourse the farfieldsupression comes stock with every beetle due to VDE rulments.
The parts to achive that had been the 4 spark plug connectors and a spider in the greasecaps. To fit a radio you had to made additional work ( Condensors on Wiper, Coil, Generator, Hoodgrounding ).

If you look close you can sometimes see the old VDE marking witch a f in circles.

I think the repair manual for the 356 has a chapter about that also Bosch had always a chapter in the ignition booklets.

My gray Bosch Handbock only says according to "StVZO § 55a", no date.


I think Porsche did know those foils, as they used them in the racecars as heat shielding.

I think they don´t trustet a adhesive in that place.
Sucked in alufoil fragments could block the oilcooler or the cylinderfins.

Domestic cars where usually not aircooled and as far I remeber those shieldings had been removed by the owners when they detoratet and saged in. ( shaker hood ? )

Also the Porsche metall inner hood stbilized the unit allowed to bolt on the light and the rear whiper. And is simplier to clean.

No it was not the Porsche way to do simple things or save wight or cost by sacrificing function or reability.

Some things do look simple but thats in the perfection to construct something simple.

YMOHO

Grüsse

[robert ellis]

Some radio frequency ground strap techno trivia.
The maximum ratio of length to width should be no greater than 7:1

This key learning came from many hours of flight test trying to determine why one of the early fuel computers for a Garett aicraft turbofan engine would command flight idle fuel flow when the pilot used the high frequency communication radio.

We also had one aircraft where the autopilot controlled bank angle could be modified by changing the tone you whistled in the mike.

Bob
90C4

[Roland Kunz]

§ 55 A electromagnetic compatibility

(1) passenger cars, force buses, truck, tractors and articulated towing vehicles with at least four wheels and one by the design determined maximum speed of more than 25 km/h - excluded country or forest-economical tractors, dump trucks, floors conveyance, trolleys and Autoschuetter - as well as their trailers must correspond to the regulations specified in the appendix to this regulation over the electromagnetic compatibility. Record 1 applies accordingly to other vehicles, which are to be equated regarding their construction features of the chassis and their electrical equipment the vehicles mentioned, as well as to components and independent technical units, which are intended for the installation in the vehicles mentioned.

(2) motor vehicles after § 30a Abs. 3 as well as independent technical units intended for the installation into these vehicles must correspond to the regulations specified in the appendix to this regulation over the electromagnetic compatibility.

http://translate.google.com/translate?hl=en&sl=de&u=http://home.t-online.de/home/bussgeld/stvzo/55a.htm&prev=/search%3Fq%3DStVZO%2B%25A7%2B55a%26num%3D30%26hl%3 Den%26lr%3Dlang_en%7 Clang_de%26safe%3Doff%26sa%3DG


Kerzenstecker

After §55 of the StVZO the ignition system at motor vehicles must be radio-screened. In addition the vehicle manufacturers have several possibilities: either by a sheet-steel jacket at the kerzenstecker also on it stamped specification, by entstoer-Widerstand a let in the inside one the plug (with specification of the resistance value) or by an ignition cable, whose structure meets the screening regulations. There are spark plugs, which usually contain a entstoer-Widerstand contained and therefore in their type designation the letter R (for Resistor = resistance) for screening also. When changing these spark plugs such must be therefore always inserted with entstoer-Widerstand. http://translate.google.com/translate?hl=en&sl=de&u=http://www.fighters-magazin.de/tuningtuev/umbauaz2.htm&prev=/search%3Fq%3DStVZO%2B%25A7%2B55a%26num%3D30%26hl%3 Den%26lr%3Dlang_e n%7Clang_de%26safe%3Doff%26sa%3DG

[acapella8]

Roland, thanks for a great thread.

Your posts are right on the money.

I have some RF issues that are related to a ground problem.

Thank you for the good reading!

[James Brown]

wow, I was reading this post as l am an aircraft mechanic and we bond everything. Even most engine wires are shielded to ground for emi emissions. (my light shorted out and l removed it that's where l found both power and ground going to the lamp). Then l saw the post from Warren "schooling" us the way only warren could! Thanks for the memories Warren-still miss him...