EDITOR’S NOTE
N2O: THE BEST OF BOTH WORLDS?
For some reason I’ve been getting asked a lot lately why I still have a 38R turbo on my 7.3L when they know I have everything the engine needs for much more power than that little turbo would ever be able to support. With my 700 rear-wheel horsepower goal in mind before the end of 2017, they know the 38R’s 500 rear-wheel limit is really holding me back. It simply won’t flow enough air to make much more than 500 horsepower. Now I’ll tell you, I never intended on keeping the little guy on there and always planned on going to a larger S300-framed turbo at some point. Well, until the bottom end gets built I’m on the fence. I still drive my truck to work every day and the 38R is great for that. Rarely do I need more than 500 hp for my 12-mile commute. But when I drag race with the truck, 500 isn’t nearly enough. But overall my current setup works pretty well, and it might for you too. Before I get into my setup, a little more info: Nitrous is known as a turbo in a bottle, meaning it adds a bunch of oxygen (like a spooled-up turbo does via compressed air) to help burn the fuel the injectors are throwing in the combustion chamber. Remember that nitrous can be much safer when used on a diesel than on a gas engine. That’s because leaning out a diesel simply means it makes less power. So unless you’re running an extremely smoky, fuel-rich tune, a small or even large shot of N2O could be pretty safe. If it’s done correctly.
Well it’s that bottle that gives me the best of both worlds. On the street the bottle is never used and the wastegate on the turbo is set to open fairly high around 45 psi for great street manners. It’s got a decently tight AR (ratio of turbine to exhaust housing size) so it spools quick and the power comes on at low rpm. Because of that tight AR, if I spray the engine without changing the wastegate setting the turbo will overspool instantly at the push of the go button. Leading to a damaged or even grenaded turbo. So on the track with nitrous I set the wastegate to open around 20 psi, getting it out of the way early, and rely more on the nitrous to get the fuel burning.
So with this setup I’m getting the aforementioned 500 hp on the street, and a healthier 600 hp for the track. Changing the wastegate setting takes only a couple minutes so it’s an easy change I can make at the pits with only two wrenches. The setup has been working so well I’m toying with adding a second kit to get to that 700 number and just keeping the 38R on there. I’m still not sure what I want to do yet.
All that being said, yes nitrous can be used on your daily, and yes it can be safe. Here’s a couple tips that have worked well for me (famous last words, I know). First, never spray at low rpm with no boost. I try to make sure the engine is over 2,200 rpm and not heavily loaded before hitting the button. In other words, don’t spray it with the converter locked and the engine bogged down. Make sure the engine can spin up so the power has somewhere to go instead of just using it to break a rod. Get off the spray before getting off the throttle, else you risk a nasty backfire. Don’t overspool your turbo; wastegates are a must, or at least get yourself a very loose AR exhaust housing and keep an eye on your boost pressure. Head studs are always a good idea. If you’re extremely over-fueled you’re putting your engine at risk no matter what. Overall, be smart, don’t overdo it, and keep in mind what your pistons and rods can handle power-wise (a quick search on Dieselworldmag.com can tell you that). If you keep it near or below that number you should be fine.