Nope, in fact they don't even provide that unless you drag it out of them.

 

Yes, it's a digital signal from the ECM to the gauge. I agree it doesn't make much sense, but that's the way Honda did it.

Looks like 5v pulses, 30ms wide, with a variable spacing relative to the temperature. 3 bars is about a 1 second spacing between pulses, longer when colder, but the difference in spacing is minimal. A 2 bar reading was 1097ms, 3 bars was 1043ms. I need to do more measurements and compare them to the OBD temp readings to get a better feel for it.

If doing this project it would be worth adding an alarm feature so you can set a temperature threshold, that if exceeded, would provide an output for a light or sounder or something other than just lighting up the 4th bar on the gauge. One more bar on the dash isn't going to get your attention.

The other issue is where the delay exists in the system. I know it takes over a minute for the gauge to go from 1 bar to 3, even if the temp sensor changes instantly. If that delay is in the ECM, an outboard gauge driver circuit could be made to operate faster. If the delay is in the gauge itself, you'll be stuck with a slow-responding gauge.

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Nice work!

And alarm would be great. Not too concerned about the delay if it's a gauge issue, but if it's an ECM issue and we can overcome it even better.

 

Not sure if an alarm is necessary. You could just use the AEM to produce an alarm to a buzzer using an ECM output. I do that already for a shift "light". I just care to have the display work.

 

Now for the big question - what are you guys willing to pay for this thing?

I'm sure it will only be a few dollars in parts, but somebody (I wonder who) has to do the software, build a PC board, test the thing in a real car, etc. If I am the someone, I'll probably spend 50 hours on it before I have the first one ready to sell.

So how many are we talking about and what's the pain threshold? $10? $50? $100?

 

I'd be in. I just spent $1600 on an EMS(with wideband) and about $150 on a 6' wire extension harness. I don't think anyone would complain too much about the price of this.

Tim

 

I know two of us that would pay around $50 for one.

 

I'd say a minimum of $50 and a max of probably $150. I would suggest a production run of 10 to start of and see how quick they sell.

Should you decide to proceed I suggest we show commitment by paying half the cost up front. I for one would be happy to do that.

 

One more thing to think about - since we'll be reading the ECT voltage, processing that info with custom software, and driving the gauge with a digital signal we create, we have the option to change the "scale" of the gauge and make it more useful. Right now we essentially have a "OK" & "Not OK" gauge, where 3 bars is normal and 4 bars never comes on unless there's a serious problem. (I assume very few people ever see 4 bars, I have a Comptech SC and a stock cooling system and have never seen 4 bars, even when track driving in Savannah GA in hot weather.)

What if we changed it so the first bar came on at 120

 

I like the idea but it might confuse things. Would it be possible to use a dip switch to swap between factory and 'modifried'?