3.9 efi wirimg

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Lmy78k
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3.9 efi wirimg

Post by Lmy78k » Sat Aug 04, 2018 9:55 am

Hi
This is my first post I am converting my holley powerd
3.5 sd1-engined stag to a 3.9 efi discovery I have completed most issues outstanding issues as follows
1 tune resistor is uk cat I have removed the cats do I need to change the resistor ?
2 speed sensor / tranducer at the moment I have the speed sensor wire back to ecu just hanging in the engine
Bay near the speedo cable seen on ebay a speed sensor that raps around the speedo cable and sends pulse back to ecu via the speed sensor cable will this work ?
3 when I bought the discovery donar car I didn't get the skt so were is the best place to source one and a reasonable priced code reader
Thx



DaveEFI
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Re: 3.9 efi wirimg

Post by DaveEFI » Sat Aug 04, 2018 10:08 am

Interesting. Can't think how you'd get a speed signal from the speedo cable itself. Have you looked for a pulse generator that fits between the cable and speedo or drive?
Dave
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Lmy78k
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Re: 3.9 efi wirimg

Post by Lmy78k » Sat Aug 04, 2018 10:56 am

Hi
Thx for that no tell me more

DaveEFI
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Re: 3.9 efi wirimg

Post by DaveEFI » Sat Aug 04, 2018 11:23 am

Don't really know the hotwire system. Went from flapper to MegaSquirt here. But I'm sure it has been discussed on here - not sure you must have the road speed signal.
Dave
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Lmy78k
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Re: 3.9 efi wirimg

Post by Lmy78k » Sat Aug 04, 2018 11:23 am

Just been back on ebay its a brantz speedo cable sensor you drop it over the speedo cable and it sends a pulse used for electronic speedometer,s and rally trip comuters it has 4 different options for different cars ?

DaveEFI
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Re: 3.9 efi wirimg

Post by DaveEFI » Sat Aug 04, 2018 1:13 pm

Ah - right. Think it doesn't actually fit over the cable, but has to be inserted in the outer. But never used one so just guessing by the description.
Dave
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GDCobra
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Re: 3.9 efi wirimg

Post by GDCobra » Sat Aug 18, 2018 9:45 pm

When I put the Hot wire system on mine I used a pulse generator which I spliced into the speedo cable. This effectively means I have 2 cables which join together at the pulse generator.
Just in case you don't know, the ECU needs a speed input for a couple of reasons:
1) Some tunes have a speed limit built in so need to 'know' road speed. Best to get a tune which does not have this.
2) the system gives an elevated "moving idle" which keeps engine speed at about 1200RPM while the car is moving, it then settles to about 7-900 depending on the tune when the car stops, of more accurately drops below a certain threshold, About 3MPH
The pulse generator I have is not quite the same as the native device as when I use Rover Gauge the road speed reported is not quite right, but it's close enough.
Before I put the pulse generator in my car would sometimes stall when coming to a halt.


You will want a green tune resistor to run without cats, or any resistor of the correct value.

You can get a cable for the diagnostic port on e-bay to plug into your computer and use the free Rover Gauge application

jenand40
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Re: 3.9 efi wirimg

Post by jenand40 » Sun Aug 19, 2018 9:19 am

When i did mine i used an original Rover speed sensor, part number PRC5956 (now AMR3386P on Rimmers website) and a set of speedo cables from S&S, now on eBay, item no. 113197914155. I had to send one of the cables off to Speedy Cables to have an end changed. All works perfectly.
If you are stuck for a sensor i have a used one available if you need it.
Hope this is of helps.

GDCobra
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Re: 3.9 efi wirimg

Post by GDCobra » Sun Aug 19, 2018 9:52 am

Have a look at this site:
http://www.remap-14cux.uk
For some information about Hot wire and links to Rover Gauge and diagnostic cables.

I think I paid £35 for mind from Mark at Blitz racing via e-eBay. He does give instructions on how to make one but given the amount of work these guys have put in and what theyll give freely I figure they deserve to make some pocket money. Wouldn't be without it now.

You may not be interested in modifying your tune but RG is handy for seeing what values the sensors are giving, checking the behaviour of the idle stepper and getting the fuel pump to run constantly amongst other things

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