Welcome to Top Tech Questions. Oftentimes, readers contact us with questions about articles, or to praise us on what a good job we are doing. But our favorite form of reader communication is tech questions. Our Top Tech section is a place where you ask what’s on your mind, and we answer it. Got a trouble code? Wondering how to get your engine to make more power? Send us an email at jason.sands@sorc.com and we’ll do our best to answer it.
Injectors and Timing
Question: I have a ’97 Dodge with the Cummins engine in it, and I have a question about injectors and timing. I recently purchased a set of injectors that were supposed to add power and increase fuel economy, and they did neither of those—they just smoked more. The shop that did the work says I need more timing to take advantage of the injectors. Is this true?
Lewis Munger
Monticello, Utah
| With larger injectors installed on out 1995 Dodge, we bumped up the timing from a factory setting of 12.5 degrees to 20 degrees to take full advantage of the extra fuel.
Answer: Injection timing does have a big role in the performance of a truck, and even with the older mechanical engines, it is a very important factor. Larger injectors will add more fuel, but it’s the timing that controls how the engine reacts to that fuel. For instance, changing from 5x0.014-inch injector tips to 6x0.016-inch units on our ’89 Dodge barely picked up any power—and made the truck about five times as smoky. The problem lay in the fact that we hadn’t advanced the injection timing, which meant all that extra fuel was just going out the exhaust. We figured this out when the boost jumped from 36 psi to nearly 50 psi, which proved we were just using the extra exhaust energy to spin the turbocharger harder. After the timing was advanced 10 degrees, the truck picked up about 50 hp. Our exhaust gas temperature went down, since we were putting more heat into the piston (and hence more cylinder pressure, and more power) rather than shooting it out the exhaust. The engine’s boost also dropped slightly.
Another important aspect of injector performance is pop pressure, which is the pressure in the injector that lifts the needle off the seat. A higher pop pressure means the injector will open later, so more timing can be run. There are limits to these factors, however, as too low of a pop pressure will cause poor atomization, and too high of a pop pressure can cause injector damage. Timing is also in a fixed range, usually between about 10 and 30 degrees. We’ve seen trucks trying to run too much timing blow head gaskets, even at stock power levels.
Since you have more smoke, we would say the injectors are working and that your timing does need to be advanced. If that still doesn’t wake the truck up, we’d say the pop pressure would need to be checked. Oftentimes, larger injectors themselves will make power, so shops usually do the easy part first, as changing the timing involves the front cover coming off, and special tools.
Big-Horsepower 6.0L Power Stroke Question: I just bought my first diesel—an ’04 Ford F-250 with the 6.0L engine, a 6-inch lift, an intake, exhaust, and chip—and now I’m at somewhat of a loss for what to do next. My goal is for this truck to pump about 650 hp by the time I’m done with it, so what is my next step? I am on a budget, so I can’t do everything at once, but that doesn’t mean I won’t pay for the best product.
Wes Alaniz Klamath Falls, Oregon
| Maryland Performance Diesel has built a 6.0L Ford that made more than 800 hp on diesel fuel, and 1,100 hp with nitrous. Expect to sink at least $30,000 into an engine to reach these pinnacle power levels.
Answer: We get so caught up in trying to help people fix their failing 6.0L Fords that we forget people are still making power with them as well. Fortunately, most of the upgrades you’ll need for 650 rwhp will also help fix the 6.0L’s trouble areas. First on your list should be a Bullet Proof Diesel EGR cooler, ARP head studs, and a tuned FICM (fuel injection control module). This will keep your head gaskets from blowing, your EGR from leaking coolant and taking out your injectors, and prevent tuning issues due to a weak FICM. After that, you’ll need a set of 225cc injectors, a stronger lift pump, regulated-return fuel system, 68mm turbo, and some good tuning. Keep in mind that there’s 30-plus hours worth of labor involved in installing all these parts, which means you may be giving a shop several thousand dollars to do the build, depending on how much of the work you can perform yourself. When all is said and done, don’t be surprised if you have about $10,000 in the engine, and that’s not counting the other $5,000 it will take to get a transmission built to hold that kind of power.
We’re not trying to rain on your parade, we’re just trying to let you know what it really takes. In reality, a hot 6.0L Power Stroke with an intake, exhaust, and a tune should make more than 400 rwhp, so you have to ask yourself how much you really want that extra 250 hp. Another option would be to just drive the truck for a bit and save some money to trade up to an ’08 to ’10 6.4L Ford, which can make nearly 600 hp with just a tune.
What Is The Best Diesel Vehicle For Me? Question: I have a ’10 Chevy Traverse, which I love! But I live down four miles of gravel road, and I really miss having a truck frame and truck tires under me, as we do get snow in winter. My son wants me to convert to a diesel vehicle, but I’m looking for opinions on what would be good for me. I like sporty, but I want some nice features for the interior, too. I won’t be towing anything, and my price range is about $25,000.
Donna Boeving Poplar Bluff, Missouri
| For about $2,000, Firestone makes a complete air-spring suspension for Chevy and GMC diesels that will make them ride like a cloud, while still supplying the needed support when loaded.
Answer: There are many folks out there looking for diesel mileage and reliability who don’t need to tow 20,000 pounds. Until the diesel ½-tons come out, we have two recommendations for daily driven trucks and SUVs for folks looking for a good ride, comfort, and fuel economy. Our first recommendation would be a later-model GMC or Chevrolet (’05-and-newer) with the 6.6L Duramax diesel engine. The powertrain is proven, and these trucks get up to 20 mpg empty, depending on how frugal the driver is with the throttle. Power is also very respectable, and the ride with the independent front suspension is superior to the offerings from Ford and Dodge. If you really want to kick things up a notch, adding a rear air-ride suspension in place of the factory leaf springs will give the vehicle a Cadillac ride on all four corners, but with the reliability and capability to handle any terrain.
Our second suggestion would be for someone who is looking for a diesel SUV, and that would be a Jeep Liberty. While not as tough as trucks, they do get better fuel economy (up to 30 mpg) and are usually a little less expensive to buy. Our own staffer Michael McGlothlin has one that he tools around in and has found it to be comfortable, reliable, and even quick for spirited driving. In our opinion, you can’t go wrong with either one of these vehicles.
