BP Automotive Explains Why Quality Matters In Wiring Harness Design

Buyer beware. It’s a sentiment that’s nearly as old as commerce itself. But in the era of online shopping, that advice that has taken on a whole new level of importance, as what you see on a web page isn’t necessarily what will arrive at your doorstep.

Cutting corners can be tempting when you’re building on a budget. But even when you have some idea of what you’re getting yourself into, the effects of trusting an inferior product aren’t always obvious at first glance. And as Bill Hillock of BP Automotive in Columbia, Kentucky explains, that’s particularly true when it comes to wiring harnesses.

“There are a lot of folks out there who say they build harnesses to GM standards, but a lot of aftermarket manufacturers are only trying to meet some of those standards rather than all of them,” he explains. “Part of the problem is that some of those standards aren’t as obvious – they tend to be the more technical elements of the design. That makes them easy to miss for the customer and, unfortunately, there are companies out there that aren’t even aware that some of those standards exist. With things like crimp height and width, we’re talking about standards that are measured in tenths or hundredths of a millimeter. When you’re buying a harness you might not know to check that, and you probably don’t want to take it apart and fool around with it anyway.”

BP Automotive's harnesses are designed, engineered, and produced here in the United States. The benefits of that go beyond simply supporting domestic businesses, though. As Hillock details in this comparison, there are fundamental design differences that can make a world of difference further down the road when it comes to durability, reliability, and the peace of mind that comes with knowing the harness you just installed isn't going to turn your cruise night into an impromptu roadside barbecue.

For more than a decade, BP Automotive has been keenly focused on developing and producing GM fuel injection harnesses to General Motors’ exacting specifications. “It goes way beyond the wire and connectors,” Hillock says. “These harnesses are designed from the ground up, and they’re built here in Kentucky from start to finish.”

To get a better understanding of how BP Automotive’s harnesses differ from the bargain bin stuff you might find on eBay or elsewhere, we’re taking a closer look at the reasons why it pays to seek out quality when selecting the wiring harness for your project, and how this race to the bottom has resulted in highly problematic cut-rate alternatives that can create more hassles than they solve.

Why Going Cheap Can End Up Costing You

When assessing a harness made by a manufacturer that is looking to turn a profit while undercutting the competition, some of the design compromises are hidden in plain sight. 

“With this customer-supplied discount harness that we recently looked at, one of the first things we noticed was that they weren’t using Delphi terminals,” Hillock tells us. “So even if someone bought one and sent it to me to quality check it, I can’t do that because those terminals are not going to work within the standards that we use. Those manufacturers don’t seem to care about things like the crimp height and width, so it’s impossible to know if something was produced to meet a standard. With a proper Delphi terminal, you have a tenth of a millimeter of tolerance to stay within the spec that GM uses.”

Here we're comparing a BP Automotive's PCM connector (top) and a customer-supplied harness from an online reseller. "The first thing you'll notice is that there's no bolt," Hillock explains. "These Delphi connectors take a special bolt with a collar on it for a lock ring. That bolt is there to provide a seal so you don't get any moisture inside this connector - when DC voltage comes in contact with water, it starts corroding almost immediately. But of even greater concern is the fact that there are open cavities on this customer provided connector. That means the connectors will eventually corrode to the terminals, and you won't be able to remove them later if you need to without risking damage."

And ignoring that standard can lead to serious issues, like circuits with high resistance.

“In that condition, a sensor might end up sending skewed information to your control module,” he says. “That can end up being a big problem for someone with a boosted application – you could actually be getting MAP sensor readings that aren’t exact, and that could cause engine damage. Your control module is only going to be as good as the information it’s getting. So if there’s extra resistance on the circuit – whether it be from the splice or the crimp where that splice ends up at the connector – you could end up with readings that are inaccurate, but don’t trigger a trouble code under certain conditions.”

If you have circuits with high resistance, a sensor might end up sending skewed information to your control module, which could lead to a big problem for someone with a boosted application. You could actually be getting MAP sensor readings that aren’t exact, and that could cause engine damage. Your control module is only going to be as good as the information it’s getting.

Other issues can stem from the materials used to build the harness. 

“Some of these guys aren’t even using TXL wires,” Hillock points out. It’s important to note that TXL is an extra-thin wall, stranded, single-conductor automotive primary wire that is popular due to its durability while being lightweight. Hillock continues, “Another thing we noticed was that all of the splices on that harness were taped – they weren’t even heat-shrunk, they were just taped together over the top of the splice. We were curious as to why they chose not to use heat shrink, so we tested the wire by just using a heat gun on it like we normally would to seal a splice. The coating on the wire immediately started to melt and turn black. That’s just from a heat gun – imagine what the temperatures in an engine bay would do to it.”

TXL wire, by contrast, is rated to SAE J-1128 standards, which specifies an operating temperature range from -59°F to 257°F.

Here you can see the difference between the crimped splices of the cheap stuff (top) and the in-house ultrasonic welding technique used by BP Automotive. The welder clamps the wires together and vibrates at a high rate, welding the copper wires together into one solid piece. “You cannot pull this apart,” Hillock notes. “You’d break the wires before you would be able to pull this apart. But the bigger problem with the crimped splice is that it wasn’t heat shrunk, it was just taped. If you tape a splice, you’re going to have problems down the road, no questions asked.”

Splices are an inevitability in a fuel injection harness – you’re not going to have a huge fuse block with a fuse for each oxygen sensor, your mass air flow, for all eight coils, and all eight injectors, and so on. But how those splices are addressed can have a significant effect on not only the harness’s overall operation, but the well-being of your vehicle, as well. 

“That’s where the Telsonic TS3 ultrasonic welder comes in,” he says. “So if we’re doing one wire to four wires, for example, we put it in this machine, hit the footswitch, and it clamps down all of these wires together and vibrates thousands of times a second to ‘weld’ them to one another. After that, you can’t pull the wires apart – it’s essentially one wire at that conjunction. And from there we seal with Delphi heat shrink – the exact same stuff you’ll find in GM fuel injection harnesses.”

There is one exception to the rule, though – and for good reason. 

“The only place where we use an aftermarket heat shrink is on our fusible link splice,” Hillock adds. “The reason we do that is because if you were to accidentally lay that against a header or something like that and it burns that fusible link, it prevents your car from burning to the ground. The cheap harnesses do not have that – they don’t have a fusible link in there, it is straight wire from there to the fuse block. So if it shorts against the header and starts to burn, nothing is stopping the rest of the car from burning up.”

Hillock explains the strategy behind fusible link design in the BP Automotive harness, an element that’s completely omitted from many cut-rate wiring harnesses on the market today. “We use an SAE-approved piece of heat shrink here — if we used a Delphi heat shrink and this needed to be repaired, it would be nearly impossible to get that heat shrink off. If anything happens — all the way back to the fuse block — the fusible link is there to burn out, so the rest of your car doesn’t.”

BP Automotive’s Design Philosophy

If there’s a golden rule to hot rodding, “Do it once, and do it right,” might be it. “Right” isn’t always the least expensive option in terms of initial investment, but it often ends up being the one that causes the fewest headaches, which can ultimately save you both time and money. That principle rings true in BP Automotive’s approach to wiring harness development.

“Many of our customers – and even folks who have bought other companies’ harnesses – make a point to tell us that we’ve designed the most well-thought-out product,” says Hillock. “When you put this harness in, you don’t have to worry about extending this and that. We’ve thought ahead – for example, the mass air flow wiring is long enough to reach to either side. Most people don’t know where they’re going to mount that air flow right off the bat. If you’ve got short mass air flow wiring, either your mounting options are limited or you have to extend the wiring yourself.”

That same attention to detail can be found in BP’s oxygen sensor wiring, as well. 

“They’re long enough, and routed in such a manner that makes them work with both shorty headers as well as long tubes,” Hillock points out. “And any part of the harness that runs by the exhaust – like the O2 sensors and the crank position sensor wiring – is covered in 1200-degree fiberglass braid to protect the harness. A lot of other companies just throw a regular loom on there and expect you to do your own heat protection. We don’t do that.”

When you put our harness in, you don’t have to worry about extending this and that. We’ve thought ahead – for example, the mass air flow wiring is long enough to reach to either side. Most people don’t know where they’re going to mount that air flow right off the bat. If you’ve got short mass air flow wiring, either your mounting options are limited or you have to extend the wiring yourself.

The fuse block design is another aspect of the harness where BP's differs substantially from the low-buck alternative. "Our fuse block has a cover over the top, and another one on the bottom," Hillock notes. "These act as splash guards to prevent moisture from getting into the terminals. On this other block the terminals are essentially exposed, which makes it very easy for moisture to get in there if this was mounted in the engine bay. It's always preferable to have anything mounted in the engine bay completely sealed."

The routing of the harness is another aspect of the design that’s easy to overlook. But by sweating the small stuff, BP Automotive’s approach can make a big difference, not only in durability but the overall aesthetic of the installation.

“The way it’s routed allows you to lay it between the injectors and the cylinder head, so it’s hardly visible at all. The harness is about 5-feet long from the passenger side of the back of the intake, so we have customers who are putting the ECM or PCM underneath the seat with a totally unmodified harness. Or you can mount underneath the dash, or pretty much wherever else you might want to put it inside the vehicle. And when you get inside the vehicle, the harness has a slidable Delphi grommet on it. That’s something you won’t find on a lot of other companies’ harnesses either – many are using cheap aftermarket alternatives which are more likely to warp and pop out over time. Anywhere that we can use a Delphi or OEM piece, that’s what we’re using. We don’t look elsewhere first.”

Here’s a look at the firewall grommet of the cheap harness as it was delivered to the customer. “This grommet is taped so you can’t move it,” Hillock explains. “And if you were to go to seal your firewall, what you’d discover is that whoever added this grommet in took the liberty of just cutting it open and then sliding the wiring through. If you left it this way, you would more than likely end up with moisture or water from the outside of the vehicle draining into the PCM connectors, and potentially damaging them.”

There’s also support to factor in, as well, which takes on several forms here. 

“Our instructions are in color and are 12 to 15 pages long, with pictures, diagrams, and anything else we think would be helpful as you’re moving through the install,” Hillock tells us. “This isn’t some photocopied thing. And then there’s our tech line – we’re there to provide expert support for our products. If you buy one of those cheap foreign-made harnesses, who knows what you’re going to get when you call in.”

BP Automotive’s YouTube channel also provides tutorials, comparisons, and other useful videos for would-be installers.

Applications

All of BP Automotive’s standalone wiring harnesses are geared toward engine swap applications, and that essentially equates to a universal fit. 

“It’s meant to work in a lot of different situations,” says Hillock. “We have customers who are using these in airboats, and pretty much anything else you can think of. Most of our standard, standalone harnesses are shelf-stock, which means you’re likely to have the harness within two business days of placing the order.”

They also offer some direct-fit options. “We have plug-and-play harnesses for S10s, fourth-gen F-bodies, and other common applications. You want to take the LT1 out of a ’94 Camaro and replace it with an LS? We can build you a brand-new replacement harness with the factory firewall grommet and everything. You put the LS in, hook up our harness, turn the key, and drive away. All the gauges are going to work – everything is going to work the way it’s supposed to.” And custom-fit harnesses are available as well. “We’ve built harnesses as long as 14-feet,” he adds. “So if you need something that’s truly one-off, we can do that too.”

Article Sources

About the author

Bradley Iger

Lover of noisy cars, noisy music, and noisy bulldogs, Brad can often be found flogging something expensive along the twisting tarmac of the Angeles Forest.
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