LS Conversion Questions - Wiring
Thread Starter
Drifting
Joined: Jan 2008
Posts: 1,517
Likes: 37
From: The Woodlands Texas
LS Conversion Questions - Wiring
Guys,
Please educate me. I'm getting close to the electrical side of my LS swap and I have a few questions. My build includes DD VHX gauges, LS3 Crate Motor with GM Hot Rod wiring harness, Keisler RS500 5 spd.
Here are my questions:
1) What additional sensors will I need to buy? I'm assuming 2 WB O2 sensors (one each side for factory exhaust manifold...not going headers). What else?
2) How do I handle the speedo? The wiring harness has a speedo output. The DD gauges has an electronic input. The tranny has a speedo cable..... I'm lost.
3) How do I wire in the electric radiator fans? Do I just get a temp control switch and keep it isolated from the wiring harness / ECU or do I integrate it?
4) What else do I need to know?
Please educate me. I'm getting close to the electrical side of my LS swap and I have a few questions. My build includes DD VHX gauges, LS3 Crate Motor with GM Hot Rod wiring harness, Keisler RS500 5 spd.
Here are my questions:
1) What additional sensors will I need to buy? I'm assuming 2 WB O2 sensors (one each side for factory exhaust manifold...not going headers). What else?
2) How do I handle the speedo? The wiring harness has a speedo output. The DD gauges has an electronic input. The tranny has a speedo cable..... I'm lost.
3) How do I wire in the electric radiator fans? Do I just get a temp control switch and keep it isolated from the wiring harness / ECU or do I integrate it?
4) What else do I need to know?
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
1. If you're not modifying the engine between the throttle body and the manifold pipe connection then you really don't need WB O2 sensors because the engine won't need any tuning. Just run the computer with the changes necessary to eliminate the codes and security.
2. You should convert the trans to an encoder. You could feed the computer and then feed the speedo output to the DD module. I would ask Keisler about this.
3. Wire relays to the fan controls in the PCM. You'll need 3 relays. Google "3-relay 2-speed electric fan wiring diagram" to find wiring examples.
3. Not sure. You'll need to have the PCM programmed for the changes you're making but that shouldn't be a big deal. If you put a sensor in it you need to know the number of pulses per driveshaft rotation. Then get the wheel size and rear gear ratio to the tuner and the PCM can be set up to know the vehicle speed.
2. You should convert the trans to an encoder. You could feed the computer and then feed the speedo output to the DD module. I would ask Keisler about this.
3. Wire relays to the fan controls in the PCM. You'll need 3 relays. Google "3-relay 2-speed electric fan wiring diagram" to find wiring examples.
3. Not sure. You'll need to have the PCM programmed for the changes you're making but that shouldn't be a big deal. If you put a sensor in it you need to know the number of pulses per driveshaft rotation. Then get the wheel size and rear gear ratio to the tuner and the PCM can be set up to know the vehicle speed.
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
1 Guessing the GM harness came with all sensors, MAF, O2s. The ecu doesnt use wide band O2s.
2. The ecu puts out a square wave signal. A VSS puts out sine wave. You'll need to find out which your gauge needs. The DD speedo gauge probably works off of their sender. Call DD, they have a VSS that connects to the trans speedo output. The ecu will also need a VSS input.
3. ECU control the fans
2. The ecu puts out a square wave signal. A VSS puts out sine wave. You'll need to find out which your gauge needs. The DD speedo gauge probably works off of their sender. Call DD, they have a VSS that connects to the trans speedo output. The ecu will also need a VSS input.
3. ECU control the fans
Burning Brakes
Joined: Oct 2010
Posts: 1,192
Likes: 7
From: Wentzville MO
Burning Brakes
Joined: Oct 2010
Posts: 1,192
Likes: 7
From: Wentzville MO
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
I'm doing a VHX setup in my Impala. The DD VHX setup will work off the PCM output so you can put a sender on the trans and wire it to the PCM and then use the output of the PCM to drive the VHX module. I believe my PCM does 2000 pulses per mile so I'll learn the VHX system to 2000 pulses (instead of driving a mile) and then adjust the speed ratio in the PCM so they are both correct and match.
I guess that works but you either have both fans full-on or no cooling. The best way to wire dual fans is the 3-relay method. That way, they first run in low speed first and then kick to high speed if it's still not cooling. All the GM vehicles with dual fans have used that method since the mid 90's so the PCM has the relay drivers and code build-in. It keeps the fans quieter most of the time.
I guess that works but you either have both fans full-on or no cooling. The best way to wire dual fans is the 3-relay method. That way, they first run in low speed first and then kick to high speed if it's still not cooling. All the GM vehicles with dual fans have used that method since the mid 90's so the PCM has the relay drivers and code build-in. It keeps the fans quieter most of the time.
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
One other note on fans. I was considering the 3 relay, 2 speed dual fans. But I wanted to control the fans with aftermarket AC, through a trinary switch. Normally the ecu looks at AC pressures and controls fans with AC enabled.
I ended up with 1 fan controlled by the ecu, single speed. The other is set to a higher temp and/or the AC trinary switch, also single speed.
Works great and fans only run when needed.
I ended up with 1 fan controlled by the ecu, single speed. The other is set to a higher temp and/or the AC trinary switch, also single speed.
Works great and fans only run when needed.
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Thread Starter
Drifting
Joined: Jan 2008
Posts: 1,517
Likes: 37
From: The Woodlands Texas
Gary,
I saw on another thread that you installed Cruise Control. Did you use the setup that came with your engine or did you buy an aftermarket type. I want to add it to my crate motor.......
I saw on another thread that you installed Cruise Control. Did you use the setup that came with your engine or did you buy an aftermarket type. I want to add it to my crate motor.......
Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
I'm running a Gen III LQ9 with DBW. Cruise is built in. The Gen IV LS3 typically requires the BCM for CC to work. The company in the link sells a package to eliminat that issue.