DL1 Inputs State When Powered Off

[Steve Wynveen]

I have a DL1 to which I have a low level tach signal tied in. This is a 1 pulse/ignition event signal that also runs the factory dashboard display in my Honda S2000.

When the DL1 is not powered up, the tach input apparently goes to ground, or at least has very low impedence, as my dash tach will show zero. I have dealt with that by powering the DL1 off of switched power in the car, so when ever the car is on, the DL1 is on.

The problem I have is that the DL1 seems very sensitive to electrical power noise/spikes. For example, when I start the car cold, a few seconds after it fires up an electically powered air pump (emssions) fires up. When the air pump starts, the tach goes to zero and then recovers. After an autocross run, I usually turn on the AC to force the cooling fans to run and help keep the engine cool. Occasionally (prob <10%) this will also cause the tach to bounce up and down or even show zero. I've checked the DL1 status lights and it still has satellites, so it indicates to me that it has not completely lost power and rebooted.

I'd like to tie in some engine sensors like TPS and MAP, but this inconsistent signal loading by the DL1 scares me from doing that. There will definitely be engine run quality problems if the DL1 were to suddenly ground out the TPS or MAP signal.

Any thoughts on how to attack this? I don't want to put in a seperate battery to power the DL1 because the headaches in maintaining a battery (and I'll forget to charge it up), and I don't want to run a wire directly to the car's battery because I know I'll forget to swtich it off and run the battery down. Perhaps a capacitor with a diode on the power input line to provide some filtering and reserve power during voltage sags?

Thanks,
Steve

[jlucas]

Steve, Just so you know, I'm looking into this as well for Rylan.
BTW, when was your DL1 initially purchased?

[Steve Wynveen]

I bought mine in the big group buy before last Christmas. I think it was built in the Jan/Feb timeframe of this year. It is serial number 1148.

Steve

[RTUSA]

We are currently working on a fix for this class of problem. Please contact RT if you are having this sort of issue. It only happens in some types of cars, others have no such issues apparently.

[Steve Wynveen]

So, should I just forward my original post to support@race-technology.com, or does support still monitor this board?

Thanks,
Steve

[RTUSA]

Steve:

Your situation has been noted, and I'll post here when we announce the fix.

I wanted to solicit the details of other users' problems to make sure that we have a complete picture as we engineer the fix.

Thanks,

[Steve Wynveen]

Any updates on this one? It has been 2 months since any activity on this thread.

Thanks,
Steve

[jlucas]

Steve, it's not forgotten. As Al can attest, I bug him about it on a regular basis. Al is having a test circuit built now that R-T guys hope will fix the problem. One of the Spec Miata guys was able to fix a similar tach issue with an inline resistor, we are trying to get him to look at what value it was to see if it helps with the S2k problem.

[GrahamB]

Still no progress?

Would it be possible to at least answer the original question, viz: does the input impedance change at power down, or does it have a guaranteed minimum due to an internal resistor?

[disquek]

I think I'm the Spec Miata guy that you're refering to. I worked with RT on this last year.

The symptom I saw was that, when the DL1 was installed, the factory tach would "max out" at around 4-5k RPM. Over that RPM, the factory tach would hover at 4-5k.

I was told that the issue was that some of the DL1s were built with the wrong resistor (too small) in the RPM circuit. That the problem was a manufacturing error that was the result of the specified component becoming obsolete.

I tried building a circuit (transistor, etc) provided by RT, but it caused other problems.

I tried various resistors in between the ECU and and DL1. A single 1/2 watt 3.3k ohm resistor seemed to fix the issue. I got the resistor from Radio Shack.

I hope this helps.

-Kyle Disque

[jlucas]

Kyle, Call Al. He needs a Miata guy to test an isolator circuit. Steve W has tested is successfully for the 2.0L S2000 (the 2.2L doesn't have the issue). Those are the only 2 models that I've heard of any issues with the stock tachometer; if someone is aware of another model, please let Al know.

[disquek]

The fix that's in my car now works. I'm going to use the DL1/Dash1 to go faster.

Thanks.

-Kyle