DME Relay does it again!

[R22tech]

Blah, Blah, Blah...so I bought one. Car idles smoother and has better low RPM performance. Actually, make that better 1/2-3/4 throttle performance. In other words, no difference in high performance, pedal to the metal driving; but "normal" driving is more "alive" and "consistently peppy" and without sputtering in 1st gear while coasting at 1000 rpms.

[ebradway]

I think we need to have a 'double-blind' test on the DME relay thing. I say we take three relays - an old, worn one, a brand new one, and an old, cleaned up one and have someone else install each in our cars and each of us give our impressions without knowing which relay is in the car.

BTW, are you talking about the DME relay or red fuel pump relay?

Also, I've got the engine out of my car and on my Father's garage floor. I spent some time looking at the throttle assembly, trying to surmise how adjusting the slack out of the cruise control cable can affect throttle response. Here is my hypotesis:

1. The cruise control, by design, should have noticeable play in the cable to prevent interfering with normal throttle action. By taking the play out, you basically forced the throttle to, say, a 5% engaged position.

2. To compensate, you adjusted your idle so that, sitting in neutral, your car runs at 800rpm with the throttle at 5% engaged.

3. Your accelerator pedal now has 5% play in it, but you don't notice it because the weight of the pedal is taking the play out.

4. Even though your idle is adjusted to run at 800rpm with a 5% engaged throttle, your DME picks up the change in accelerator postion when you give it gas and thinks 'the driver wants 10% throttle' when you press 5% of the way down - and gives you a 10% kick for 5% of throttle activity.

But this is coming from a layman who has only dropped his engine half a time (it's not back in yet).

[DANNOV]

Originally posted by R22tech
Blah, Blah, Blah...so I bought one. Car idles smoother and has better low RPM performance. Actually, make that better 1/2-3/4 throttle performance. In other words, no difference in high performance, pedal to the metal driving; but "normal" driving is more "alive" and "consistently peppy" and without sputtering in 1st gear while coasting at 1000 rpms.

I told you so, are you now a believer? It makes a difference. I also did the 1st gear test and it made a difference for me. Unfortunately DME relays are on 90 day backorder so the rest of you people will just have to wait. I'm just kidding, but I suspect that a lot of new relays are about to be ordered and that is good because a lot of these old Carrera's need a little boost.

[68_912cbb]

what is this DME relay ???

I just picked up a 1986 911, will it help ?

[DANNOV]

Originally posted by 68_912cbb
what is this DME relay ???

I just picked up a 1986 911, will it help ?

Cecil
Check the thread dated 11-16-2001 "Replaced DME Relay". If your DME relay is as old as your car it may certainly help. These old relays are are trouble and the first symptom is deteriorating performance, it creeps up on you and before you know it your car runs like crap!

[mwbaum]

OK...I didnt have a spare.....and I think my 85 runs decent the way it is....so I bought a new DME relay for a spare....I will install it as soon as the rain quits and see if it improves things at all.

[R22tech]

Some answers:
1) car is 85 carrera--DME Relay has 8/15/89 stamp, so it had been changed before.
2) I pulled the cover to inspect old relay: It looked perfect-no dirt or burn marks and the contacts were "like new".
3) Only reason I changed it was for "good measure". My car evry once in a while won't start when warm. It cranks, but like is out of gas. When this happens(3 times a year) I have to pull out the key and retry, then it works. Due to this problem, I wanted to carry a spare DME relay just-in-case.

Once again, replacing this relay didn't give me more power at full throttle-it felt the same or even SLOWER! Why? Because before I replaced the DME relay there was a lack of low rpm pull, maybe you could call it a hesitation, and then from 4000rpm+ it really pulled hard. Now, with the new DME relay, it is a more consistant pull from 2500rpm-redline.

I feel the biggest positive difference while driving normally, which is less than full throttle. The car just is more well-mannered, smoother: it's got to be in the fuel delivery, which I believe is controlled by the DME/and/orDME relay.

[Joeaksa]

I am having absolutely no problems at all with my 85 car but am positive that it has the orginal relay still installed.

I, like most of the rest of you guys, have an extra new relay in the car for emergency. Now after all of this I am going to have to switch it out with the new one to see if there is a difference. The old one will remain in the car as a spare for emergencies.

Cannot believe that it would make a difference, but if it does, (like everyone else is finding) we all owe Dannov a beer someday!

JA

[falcon]

guys, can you throw me a bone here. I've checked the threads, but no clue to what this DME relay looks like, where its located on the car or where one can be purchased. The only clue I have is in the Bentleys manual showing me the pinouts.

Thanks in advance

[Early_S_Man]

It is under your seat ... right next to the DME unit, and it should be bolted down, but may be loose if the last person to look at it was careless/sloppy! It is rectangular, like a two-stage degogger relay!

[R22tech]

Falcon- The DME Unit is located under the driver's seat on my 85 Carrera. It looks like a 4"x6"x2" grey metal box. Next to it, closest to the door, you will see a black 2"x2"x3" relay with a harness attached. Just unplug the harness from the backside of the seat, then move the seat all the way back and up to remove the 1 screw that holds the relay in place. This is the DME relay.

[5axis]

last.
I am pretty sure Wayne would prefer it if you bought your spare from him right here at Pelican.

[R22tech]

Speaking of that- I did buy mine from Pelican. The old one said "made in Germany" on it, and the new one said "made in Hungary". What's up with that?

[Decolliber]

Originally posted by ebradway

... By taking the play out, you basically forced the throttle to, say, a 5% engaged position.

2. To compensate, you adjusted your idle so that, sitting in neutral, your car runs at 800rpm with the throttle at 5% engaged.
...

To which I would add: and your idle switch may be permanently open, because with the drag arm adjusted to its normal position, it should only need to move 1 mm to open the idle switch.

[falcon]

thanks guys for the description. I rechecked bentleys and there is a error which did confused me. On page 200-1 it shows the DME main/fuel pump relay as item "A" and the altitude correction switch as item "B" which is clear. Except, when one looks at page 200-7, picture is titled altitude corrections switch but its pointing to the DME relay.

Now that I'm straight on the which one is the relay and where its located, I can proceed with purchasing the "right part."

Wayne, an order is coming down the pipe!

I hope I'm not on the waiting list very long, but it will be worth the wait.