Solid State DME Relay being developed
07-03-2015, 08:35 PM
#1
Rennlist Member
Thread Starter
Solid State DME Relay being developed
No affiliation...Posted over on Pelican...Pretty interesting: http://forums.pelicanparts.com/porsc...rs-wanted.html
Last edited by TMc993; 07-04-2015 at 09:08 AM.
07-04-2015, 12:42 PM
#4
RL Community Team
Rennlist Member
Rennlist Member
If it ends up costing more than the price for a couple of standard relays I would just stick with the electro-mechanical ones. As one in the car and one in the glove box provides good coverage and a malfunctioning one can be resoldered and put back in the car. Also the relay exists in the first place to protect the Motronic Computer where the relay fails rather than the computer becoming fried. I wonder if this role is retained with a solid state relay?
07-04-2015, 12:46 PM
#5
Terry,
Thanks for sharing and the link!
Andy,
If the relay exists for the basic functionality/purpose stated; would it not be pointless to create a SSR that does NOT protect the ECM?
Thanks for sharing and the link!
Also the relay exists in the first place to protect the Motronic Computer where the relay fails rather than the computer becoming fried. I wonder if this role is retained with a solid state relay?
If the relay exists for the basic functionality/purpose stated; would it not be pointless to create a SSR that does NOT protect the ECM?
07-04-2015, 06:31 PM
#7
Three Wheelin'
Compare the circuit of a Porsche DME relay with a Mercedes OVP relay. Pretty different animals, with the later clearly designed to protect the car's computer.
Anyway, I may be wrong. Maybe an EE can chime in.
Trending Topics
07-04-2015, 06:56 PM
#8
RL Technical Advisor
Are you sure about that? I'm far from an electronics expert, but to me, it seems the relay is just a switch, like any other automotive relay. 12v from the ignition will switch on power to both the DME and the fuel pump so the car will run. 30 to 87 with nothing in between. Certainly nothing that would warrant protection to be its primary purpose.
Compare the circuit of a Porsche DME relay with a Mercedes OVP relay. Pretty different animals, with the later clearly designed to protect the car's computer.
Anyway, I may be wrong. Maybe an EE can chime in.
Compare the circuit of a Porsche DME relay with a Mercedes OVP relay. Pretty different animals, with the later clearly designed to protect the car's computer.
Anyway, I may be wrong. Maybe an EE can chime in.
I'm certainly not an EE, but I've spent some time poring over these car's current flow diagrams and have to agree; the DME relay is simply a switch, providing the high current loads to the fuel pump and DME.
If you improperly connect a (cheap) battery charger or jump-start the car with reversed polarization, its possible to fry the alternator, VR & DME.
07-05-2015, 04:24 PM
#10
reverse polarity of the battery, i.e. the DME relay won't activate with reverse polarity.
The relay won't, though, protect against an over-voltage condition.
07-06-2015, 01:49 PM
#11
Drifting
Join Date: Apr 2003
Location: la la land | comin' back soon nyc
Posts: 3,351
Likes: 0
Received 2 Likes
on
2 Posts
No affiliation...Posted over on Pelican...Pretty interesting: http://forums.pelicanparts.com/porsc...rs-wanted.html
07-07-2015, 04:55 AM
#13
Rennlist Member
Although I believe in SS relays for certain applications, I do not see a need here since my original relay worked for over 15 years and after having re soldered all the joints, it is unlikely to ever fail again. Note that the relay contacts were still as new as day-one.
A SS relay not properly designed or manufactured with poor solder joints or non automotive spec components is no more reliable.
A SS relay not properly designed or manufactured with poor solder joints or non automotive spec components is no more reliable.
07-07-2015, 09:25 AM
#14
Rennlist Member
Thread Starter
I'm thinking that if he comes up with a solid and reliable solution, maybe we could convince him that his next project should be a plug-in device to completely disable/bypass the immobilizer. 
