I'm halfway through building a wiring harness for a Haltech Elite 1500 in my NA FB and I'm wondering if I'm doing the grounds correctly. The haltech premium harness includes a single black cable for the battery negative terminal, but nothing labelled as a chassis or engine ground. Do I need to add any grounds to this harness? Maybe ground one of the 5v sensor ground wires to the block? I read a lot of posts about older Haltech's including both a chassis and battery ground cable but it seems the Elite series doesn't.

Here's a crude drawing of what I plan to do, utilizing a junction post next to the battery so I don't have too many things directly attached to the battery:


This excludes the non-battery grounds required by the AEM ignition coils, which mostly follow a diagram like this one: https://www.rx7club.com/haltech-foru...dback-1148832/

Is this correct? Do I need to add a ground between the battery and the engine block through this junction post? And do I need to ground a 5v sensor ground wire somewhere on the block or chassis also?

 

I would keep the ecu ground and the coil ground separate.

 

The AEM coils require 3 separate types of grounds. One to the housing, one to the battery, and one to the ECM. So it seems each coil will have one wire running to this junction post in addition to the other two types

 

the high current ground its a dirty ground,i would ground that one straight to the battery

 

Ok, looks like others recommend the same although I don't know enough about wiring to understand how that's different than using the ground post a couple inches away that's tied directly to the battery.

Updated diagram:

 

What you have listed there as "Alternator Ground"... what wire is that? If you're referring to the (admittedly confusingly colored) large gauge black wire that comes off the main alternator stud, that is a positive feed, not a ground. If you connect that big black wire off the alternator to ground, you're gonna have a bad time. Sensor grounds all end up using the main ECU ground internally, which is how they all maintain accurate reference. You don't want to ground a sensor ground wire to chassis, that just creates alternate ground paths and will skew sensor readings.

 

Looks like my GSLSE alternator has a positive stud (top) and negative stud (bottom) in addition to the two pin connector in the middle. That ground wire used to run straight to the strut tower and terminated there.

 

Haltech battery ground goes directly to the battery negative terminal. Power ground for the coils goes directly to the battery negative terminal. DO NOT connect anything else from the Haltech to ground. Terminals B and C of the coils should both be connected to engine ground.

The alternator grounds through its case to the engine. Someone added that other wire and it should be removed.

Ideally, the negative terminal of the battery will also be connected with something around 2g wire to the engine block. From the engine block you bring a ground strap to the chassis. More connections are not necessarily a good thing. If you have issues putting it together the way I describe it, you’ve done something wrong.

 

The AEM instructions specifically say B should go to the sensor ground, so I ran sensor ground wires from the Haltech to these pins on the coils. Is there a reason B should go to the engine instead of the sensor ground?

Also, with this setup I'll be running a lot of wires directly to the battery. Is it not OK to put a stud right next to the battery with a single large gauge wire connecting the stud to the negative terminal, or do all these wires (coils, haltech ground, engine ground strap, etc) need to go directly to the terminal?

 

Here's an updated diagram. My question is whether I can use a post to avoid 5+ connections at the negative battery terminal

 

AEM shows ECU reference ground as that’s what the OE application for the coil uses. However, that is used for misfire detection that none of the aftermarket ECUs support. Therefore there is no benefit to using the reference ground and the possibility of a large current draw through that circuit in the even of a coil failure that could wipe out the ECU. Ground pin B to the engine.

The primary ECU ground should go to the battery post along with all sensitive devices such as loggers for two reasons. One, the negative post is the only true 0v location in the car. Two, the battery acts as a capacitor and dampens spikes and flyback voltage. Coils, fans, pumps, and other dirty devices can be ganged together but you need to be mindful of creating ground loops with multiple ground locations. I’ll post a useful diagram later.

 

Credit to Scott Clark for producing the image.

 

I'm very glad I started this thread, this is all very helpful.

I assume that pin B on my coils going to engine ground means pins B and C need to go to the same place (each respective rotor housing)? So hypothetically if I have already wired the coils I could just cut wire B behind the connect and splice it into wire C right next to it? Or do these need a separate wire to the same spot where the single large battery-to-engine wire runs?

 

From the connector at the coil I use 22g for B and C and splice four of those together for each pair of coils per rotor. I tie those 4 together to a single 18g that runs to the rotor housing each coil discharges into. I’ve done a single ground point for all coils with good results as well.