Limeworks' Pulse Jet Wiring System- Electrickery

If you've ever wired a project car from scratch, you'll know what it's like to feel a little panic set in when you have wires absolutely everywhere and a couple of bundles of wire about 3/4 inch in diameter that you have to run to the front and rear of the vehicle. Not only do you have to find a route to run all these wires, but you want to run them neatly and usually have to run them one at a time. It's a tedious, time-consuming task and very labor-intensive. Now imagine if you only had to run one or two wires to the front of the vehicle, the same to the rear, and then hook up the wiring to the engine. Yeah, wouldn't that be nice?

Well now you can, thanks to the same technology used in OEM vehicles. Limeworks' new Pulse Jet system employs three modules-one at the rear for the lights, turn signals, fuel pump, and whatever else you have back there, one at the front for the lights, turn signals, horn, fan relay, and whatever, and the main module in the interior-with a dedicated wire assigned the task of communicating digital messages to the modules. This means you only have to run a single wire to each end of the vehicle from the main module, plus a power feed wire to each module from the battery.

Modern OEM vehicles that use this kind of technology use one of two systems: CAN (Controller Area Network) or LIN (Local Interconnect Network). LIN is used for low-speed devices, while there are two speeds for CAN, CAN-A being medium speed and CAN-B being high speed. This allows three speeds between the two systems, the speed determining how much information can be sent in a given period of time. For instance, a video player would require a high-speed system. Limeworks' Pulse Jet is a LIN-based system, as the majority of hot rods don't use high-speed devices, mainly requiring only lights and motors to be turned on or off. The advantage of a LIN system is that the parts are relatively inexpensive, as the OEM manufacturers buy so many of them. It's recommended that you don't try to interface with old trans and engine modules with this system though, as they are higher data rate devices.

The big advantage of using the Pulse Jet over a regular wiring harness is that you'll be able to accomplish wiring a car in less than a day, rather than the week it can often take, and having wired cars from scratch in the past, we can only see that as a good thing! Wanting to see the Pulse Jet in action, so to speak, we followed along as Limeworks proprietor Steve Dennish installed the first preproduction system in his own '32 roadster, just days before the Grand National Roadster Show.

The kit is simple in the extreme,...        read full caption The kit is simple in the extreme, though of course the technology is inside the modules. The main module is shown at right, while the two black boxes with the wires are the front and rear modules. These were prototypes, the production modules being much smaller as you'll see.	Another benefit of using the...        read full caption Another benefit of using the Pulse Jet wiring system is that smaller gauge wires than usual can be used, such as 18-gauge for the power feed to the main module and the communication wires to all the modules. The power feed to the front and rear is 12-gauge, while 20- and 22-gauge wire is used for everything else. For those not familiar with wire gauges, here's 22-gauge wire compared to a quarter (the higher the number, the smaller the wire).	Here's the main module, and...        read full caption Here's the main module, and again, this is a prototype; the green connectors are shorter on production versions. This module is mounted behind the dash, or elsewhere in the interior, the power, ground, dash, ignition, and communication wires all connecting to the side nearest the camera, with the horn, fan, headlight, turn signal, and any other switches wired into the far side. Think of this module as like the fuse box in a conventional system and you're halfway there, though of course you'll need a fuse box in addition here, too.
In addition to thinner gauge...        read full caption In addition to thinner gauge wiring, this system allows you to use thinner gauge power and ground cables on the battery, which itself can be smaller than usual. This is due to the power management feature built into the Pulse Jet control. When the starter is active, the system shuts down all the other active large loads, such as headlights. This helps control the total load the electrical system has to handle. Steve used an Odyssey PC925, and you can see how much smaller it is than a normal battery by the size of the battery box. And yes, it will be secured before use, though it is a nonspill design.	Steve fabricated this aluminum...        read full caption Steve fabricated this aluminum plate to mount the main module and a small fuse panel on the inside of his firewall above the steering column. As you can see the main module is very compact, measuring 4x2x1 1/2 inches.	Still on the inside of the...        read full caption Still on the inside of the firewall, Steve opted to use braided wire for the engine harness for a period feel, wrapping it with wax cotton rather than wire ties or plastic spiral wrap for the same reason. Though not part of the Pulse Jet wiring, it's a nice touch.
As a comparison to the minimalist...        read full caption As a comparison to the minimalist wiring of the Pulse Jet system, here are the huge bundles of wire that a "normal" aftermarket wiring harness consists of. Feeding these to each end of a vehicle is time-consuming and can get confusing once they're no longer wrapped in tidy loops...	...as can be seen here. All...        read full caption ...as can be seen here. All these wires have to be routed to the front of the car for high-beam, low-beam, and parking lights, turn signals, horn, and the fan. Wouldn't one wire plus a power feed be simpler?	This is the front module on...        read full caption This is the front module on Steve's roadster, mounted under the radiator on the front crossmember, hidden behind the grille shell. The yellow wire is the single LIN wire from the main module, while the red wire is the power feed from the battery. Once these are run to the module, the remaining wires branch off from here to the lights, horn, etc.
The rear module is mounted...        read full caption The rear module is mounted on an aluminum plate in the rear of the trunk, below the latch. Again, a single yellow LIN wire and a battery feed are the only wires routed to the module. A small fuse panel is also located here, as well as a relay for the fuel pump. This is a power relay, but ground relays can also be used with the Pulse Jet.	Lights, camera, action! With...        read full caption Lights, camera, action! With the modules mounted and wires run, it's time to check the circuits. Wiring using the Pulse Jet system is much less of a chore than using a regular harness, and both ends of the car were completed in just a few hours. Oh, and if you wondered where Steve got that cool license plate light from, you'll have to ask him!	Wire Preppin' The freshly...        read full caption Wire Preppin' The freshly soldered wire, ready to be joined to the connector.
Soldered joints are more reliable...        read full caption Soldered joints are more reliable than crimped connectors, and as Steve was tackling this task, we thought we'd include it. Here he's soldering the end of a braided wire, heating it with a soldering iron and applying flux core solder to the bare wires.	Employing the same process...        read full caption Employing the same process again, the connector is slipped over the end of the tinned wire, heated with the iron, and once hot, solder is fed into the joint.	Neat, tidy, and ready for...        read full caption Neat, tidy, and ready for years of service. Unlike a crimped joint, there's minimal risk of a soldered joint working loose over time.
To protect and insulate the...        read full caption To protect and insulate the bare wire and connector, Steve applied shrink wrap to the joint. This is supplied in tube form, and heating it will cause it to shrink to fit. It can be heated with a heat gun, but passing the soldering iron over the wrap without actually touching will also cause it to shrink.