LS7 loom vs std Ult loom confusion - need help!
Discussion
Jeez, am I frustrated! 
Having failed to locate a good Auto-electrician (with LS7 experience)in my neck of the woods (Cheltenham/ Evesham area), I have been going it alone trying to fathom the wiring in the engine bay.
Any one out there that can help resolve my confusion over what links to where?
1. The LS7 loom is pre-factory and thus is different from the factory on. It appears to have a speedo feed and a tacho feed, yet so does the main loom (from the engine bay back to the instruments). Just to confuse the issue still further, I have an SPA dash system, and this also has a speedo (hall effect) wire and a tacho wire. Can anyone tell me what I should be doing without being rude?
2. The SPA dash has two pressure and two temprature sensor wires + sensors. What is the best usage/ connections for the LS7?
3. I was advised to beef up the +ve wire to the LS7 Alternator post since I was told that this unit pushes 55 amps. The original Ultima loom has one dark brown 17amp + one light brown 27amp wire strapped together for this post, and I have run another 27amp wire back to the front of the car - I presume this is correct?
...but I have no idea where the 27amp brown wire is connected at the front as I can't see it at all?
any nuggets of advice would be gratefully received.
cheers
Keith
Having failed to locate a good Auto-electrician (with LS7 experience)in my neck of the woods (Cheltenham/ Evesham area), I have been going it alone trying to fathom the wiring in the engine bay.
Any one out there that can help resolve my confusion over what links to where?
1. The LS7 loom is pre-factory and thus is different from the factory on. It appears to have a speedo feed and a tacho feed, yet so does the main loom (from the engine bay back to the instruments). Just to confuse the issue still further, I have an SPA dash system, and this also has a speedo (hall effect) wire and a tacho wire. Can anyone tell me what I should be doing without being rude?
2. The SPA dash has two pressure and two temprature sensor wires + sensors. What is the best usage/ connections for the LS7?
3. I was advised to beef up the +ve wire to the LS7 Alternator post since I was told that this unit pushes 55 amps. The original Ultima loom has one dark brown 17amp + one light brown 27amp wire strapped together for this post, and I have run another 27amp wire back to the front of the car - I presume this is correct?
...but I have no idea where the 27amp brown wire is connected at the front as I can't see it at all?
any nuggets of advice would be gratefully received.
cheers
Keith
Hi Keith,
I'm not too clever with wiring and mine is an LS3 loom, whether it's the same I don't know, but the way I looked at it was;
1. I have a DigiDash and use the speed senders that came with the dash to work the speedo, the rev counter I'm trying to hook up with the bulkhead plug within the engine loom.
2. The senders/sensors that came with the loom/engine I'm using to feed the ECU with info (ie. oil pressure/temp, water temp), and I have also connected the sender/sensors that came with the dash by means of top hose water temp adaptor, oil temp sender in the oil filter head, oil pressure sender connected to the adaptor on the engine (if that makes sense!)
3. No idea, I'm also stuck on the wires going to the alt.
So what I have are two systems, one system that the ECU needs to operate but I can't see the readings, and one system that I need to feed the dash and these readings I can see.......
I hope that helps a bit
Graham
I'm not too clever with wiring and mine is an LS3 loom, whether it's the same I don't know, but the way I looked at it was;
1. I have a DigiDash and use the speed senders that came with the dash to work the speedo, the rev counter I'm trying to hook up with the bulkhead plug within the engine loom.
2. The senders/sensors that came with the loom/engine I'm using to feed the ECU with info (ie. oil pressure/temp, water temp), and I have also connected the sender/sensors that came with the dash by means of top hose water temp adaptor, oil temp sender in the oil filter head, oil pressure sender connected to the adaptor on the engine (if that makes sense!)
3. No idea, I'm also stuck on the wires going to the alt.
So what I have are two systems, one system that the ECU needs to operate but I can't see the readings, and one system that I need to feed the dash and these readings I can see.......
I hope that helps a bit
Graham
Dear Keith,
from your post I would advice to get someone to help you out. The LS7 engine requires some additional wiring, as it runs a ECU, high pressure pump and
some other additional wiring. The sensors of your SPA Dash can go anywhere you like them to be in your system, and you can use the factory wires. I used the speedo wire that came with my dash, only to make sure not to have any issues with poor shielding of the factory wire. You will need also a relay for the fuel pumps as they are controlled by the ECU. I also have a relay for the ECU itself as it is quite hungry and I did not want to go too much current over the key switch.
from your post I would advice to get someone to help you out. The LS7 engine requires some additional wiring, as it runs a ECU, high pressure pump and
some other additional wiring. The sensors of your SPA Dash can go anywhere you like them to be in your system, and you can use the factory wires. I used the speedo wire that came with my dash, only to make sure not to have any issues with poor shielding of the factory wire. You will need also a relay for the fuel pumps as they are controlled by the ECU. I also have a relay for the ECU itself as it is quite hungry and I did not want to go too much current over the key switch.
Keith
For the SPA dash use 'its' wiring for the speedo with the magnet attached to the drive shaft hub and the sensor mounted nearby. You will have to make a bracket for this.
Please note the magnet has a + and - side to it and it must be attached the right way up. The instructions explain this.
The rev counter needs to be set in the SPA as four cylinder (i think) - i will check this and the connection for the SPA wiring will need to join into the ls loom on the obd II plug by the ecu with a resistor. i will check these connections for you to.
dave
For the SPA dash use 'its' wiring for the speedo with the magnet attached to the drive shaft hub and the sensor mounted nearby. You will have to make a bracket for this.
Please note the magnet has a + and - side to it and it must be attached the right way up. The instructions explain this.
The rev counter needs to be set in the SPA as four cylinder (i think) - i will check this and the connection for the SPA wiring will need to join into the ls loom on the obd II plug by the ecu with a resistor. i will check these connections for you to.
dave
OK,
so I have found out that the tacho feed for the SPA dash only requires a resistor if a magneto type ignition system, but will easily take short CDI type pulses up to 500v.
So...does anyone know what type of output is made by the LS& tacho wire?
If magneto, what resistor will be required?
cheers
Keith
so I have found out that the tacho feed for the SPA dash only requires a resistor if a magneto type ignition system, but will easily take short CDI type pulses up to 500v.
So...does anyone know what type of output is made by the LS& tacho wire?
If magneto, what resistor will be required?
cheers
Keith
ta!
So how (where) can I double-check that the output would be suitable? Are there any spec/docs that describe the output from the ECU for the tacho?
I notice that the LS7 supplied loom seems to have a speedo output as well, but I cannot fathom where it gets that info from and what it is for. It is academic I know as I will not be using it - just curious!
cheers
Keith
So how (where) can I double-check that the output would be suitable? Are there any spec/docs that describe the output from the ECU for the tacho?
I notice that the LS7 supplied loom seems to have a speedo output as well, but I cannot fathom where it gets that info from and what it is for. It is academic I know as I will not be using it - just curious!
cheers
Keith
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