m73m95

So, I was getting gas lastnight, and during my usuall oil/coolant check, I decided to put my spare DME relay in. I don't really remember why it went through my mind to change it, but it did.

I started my car up after my fuel up and WOW!! I don't know if I'm dreaming, but my car feels like it started faster, and now has more power. There's a change in the pavement (old pavement to new, darker pavement) a few hundred after a stop sign in my town, and usually I hit 60 just after the line. I tried it again today after work, and I hit 60 30 or 40 feet before the line.

How could this be? I thought a relay either worked or it didn't. I had no trouble at all with my old relay, or so I thought.... Would a relay fade without going out? Could one part be out, and the rest work fine? Or am I high? lol

Thanks for the input,

krazykarl

You wouldn't think changing the relay would have an effect unless it wasn't working at all. The only thing I can come up with is maybe it wasn't carrying the proper amount of current due to age and that had an effect on the DME. Could always put the old one back in and see if the car goes back to how it felt before the switch

Whisper

<computer engineer>
Digital hardware tends to fail in one of two ways.

It either becomes a brick, or it becomes erratic and behaves unpredictably.

Consistent misbehaviour such as you are experiencing suggests that the problem is not really with the circuit at all.

The DME must, however, receive airflow information, and send signals to the fuel pump, and injectors. These are analog signals, so they're most likely going through potentiometer, undergoing A/DC, etc.

If the analog reading coming in or out is off, you could be running rich or lean as a consequence.

</computer engineer>

teamking

I'm with Karl-- put the old one back in and test (and then the new one again, and repeat).

My guess is the the change is from changing gas, or air temperature, or just in your head.

But that would be great (in that it would be really really interesting to find out why) if I'm wrong.

Let us know.

Dougs951

Just by chance did you put a different grade of fuel in by accident?

Judson951

Where can I get one of them DME's? The **** added like 50 horsepowers.

m73m95

I am more likely to agree that its all in my head, but I drove 550 miles last night and used less gas than usuall on my trip...by about an 1/8 of a tank (Just going by the needle on my gauge) (I will, of course, check my mileage when I do fuel up again. I can usually go 600ish miles on a tank. We'll see how far I can go this time)

See, I have my routine down for my trip. I drive between Springerville AZ and Las Vegas once every 2 or 3 weeks. I get gas at the same station, and even the same pump (I keep a close eye on my mileage). I always use premium. With the MaxHP chip, my car runs like **** unless I use the champagne of gas.

When I finally get to Las Vegas, my gas needle is about a needles width above the red E line. This time when I got home, the needle is a hair below the 1/4 line. I even sat in traffic, waiting for a wreck to get cleared, for almost 30min.

The only thing I can figure is the resistance in my relay is different. Age and a little corrosion I think is skewing the signal to my DME. Also, when I floor my car, it usually has some slight black some, so at WOT it runs rich....but I didn't notice it on the new relay. I obviously cannot see my exhaust when I drive, but with the split in my hatch gasket, I could smell the exhaust at WOT, and now its nearly gone.

I will switch back to my old relay and make sure I'm not insane, but I thought I would share this with everyone. I'll update again after the switch...and when I switch back again.

Mike C.

A relay is just an on/off switch... I can't imagine it could 'partially' work...

toddk911

Thats what I was taught in electronics but damn if there havn't been plenty of electrical issues that were "sort of bad".

Usually it is connections. Like he said, maybe there was some corrosion in the old one at the terminals or inside. Or putting in the new one made a better connection than the old one.

m73m95

Ok, I just bought a Beltronics Vector FX2 Performance Computer on Ebay. As soon as I get it, I'll switch out the relays and make some runs.

I don't know how accurate those performance computers are but it should show a difference in the relays, if there is one.

Jfrahm

It'd be better to get a friend to put the relays in so you don't know which one is in there and do not unconsciously skew the results.

-Joel.