Charlie

I am putting a GPS/Navigation Radio into my 86 944. I have a few questions, not sure if anyone has the answers but never hurts to ask.

1. What color is the wire that supplies the Speed Pulse to the speedometer?
2. Does this wire go to the cruise module?
3. Does anyone have any calibration data, such as pulses per tire revolution?
Thanks

Don 944 LA

Pulses ???? On a GPS ?????
WTF ????

GPS units mainly run on NMEA or SIRF. SIRF being the fastest..
Usually they update (from the satalites) 5 - 10 times a second and provide the speed off of that.
I have at the most 5 different GPS's in my 944 and at least 2 going at all times.
Speedo, whats that ?? Mine has been broken since I have had the car.

A speed measurement from the satalites is much much more accurate than ANY speedometer could be. Most of the ones I have seen are 15% off (+) below 35mph and 10% off (-) above 70mph.

Don

Charlie

I did not design the unit but according to Becker it will not work without a DC pulse from the speed sensor. Therefore I need the information above.

Here are a couple of explanations I have found for the sensor, I have no idea how accurate they are. I guess Becker could better explain their design.

First explanation
The speed sensor wire allows the Nav system to be MUCH more accurate and up to date as to its location as you drive. If you are using only the GPS to locate, the update rate is only like once very 7 or 15 seconds. With the Dead Reconning (sp) via compass and speed sensor the unit will kepp you up to the moment and then verufy via the GPS data.

Here is another explanation

I believe the speed sensor (and a built in compass) is used when GPS is out of range so that the unit can continue to track.

For example, my nav continues to track even though I'm in an underground parking lot. It does so by reading the speed of my vehicle and the compass setting. Once out in the open, it re-trains with the GPS to get an actual fix on where I am.

Matt H

Speed sensor on a 944 will not be in pulses per tire revolution, that would be the speed sensor for an ABS unit, the only speed sensor on an 86NA is going to be the one at the back of the bellhousing, if I understand your question correctly.
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Charlie

Matt,
You are correct in that the sensor is on the tranny but evidently there is a relation between pulses and speed and that is how the speedometer works.

In reading the manual it looks like if I can find the correct wire then it has a self calibration mode where I input the tire size then of all things I enter the approximate tread depth. I then do a calibration ride. I will have to play with it in the next couple of weeks and see if I can get it to work.

If anyone has knowledge please post.

Thanks

Matt H

If you will search posts on the AVC-R you will find your answer
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Charlie

I just talked to Kevin at North Hollywood Speedometer and he said that there are 6673 pulses per mile. There should be approximately 800 revolutions per mile.

Charlie

Thanks Matt, it looks like a dark blue with red wire. Kevin at North Hollywood did not know the color but said it would be the 4th pin up on the vertical plug. Also he said go with the 6673 pulses and if that did not calculate correctly with the traffic pro try 6411 or 6140 which I assume are different trannys or speedometers that the 944 had in 86.

Don 944 LA

You have got to be kidding !!!!
I seriously hope that is a typo ..
do you realize how many maneuvers your vehicle can do in 15 seconds ??
They should call that Nav system " a shot in the dark "

I'd be getting my money back if I were you, but thats just my opinion..

Don

Charlie

The seven second comment was buy a Rennlister in I believe the 911 forum. He may not no any more than I do.

I have a couple of friends that have them in their 911's. They like them very much, they are a din sized radio and cd player. I believe the people that designed them probably knew what they were doing. At the price I paid for this the radio and cd player would cost more. It is the same radio and cd player as the Porsche CDR 220, which I currently have in the 944.

sm

What model is this navigation unit? Got pics? Becker has some nice units, like the Mexico and Indianapolis.

Charlie

This may explain the speed sensor.

Some models have a feature called "dead reckoning." This means that the unit will attempt to maintain routing directions in the event of loss of satellite lock. Dead reckoning works by using a compass or gyroscope. Because it's tied in with your reverse lights and speedometer it must be permanently installed. The models with dead reckoning are considerably more expensive and unless you are doing a lot of big-city driving where tall buildings will block the signal, the extra cost is not justified.

I have a couple of the Becker pictures I can post. It is a model 4773.

Don 944 LA

How do you type in an address with that . ???? does it go on voice recognition or something.

whats the traffic link.. Will it interface with Caltrans or ( insert state traffic authority here ) ???

also, does it give voice directions ??

I like the 1-Din size.. what else does it do ???

Don

Here's mine .....

Matt H

Hope that helped, that is one of the few items that calls for a speedo or tach reference (because the ACV-R will run as a speedo and tach). I was rushing out of the office so I didnt have time to refer you to them directly.
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Don 944 LA

does this help ??