EDITOR’S NOTE

TURBOCHARGING

The diesel world is constantly changing. In drag racing, up until maybe the 2016/2017 season, two-turbo compounds were the hottest way to go. All the big dogs were running them, and everyone else wished they were. Then we started seeing a lot more triples, still a compound design but with three turbos instead of two. Those made great power, just like their two-turbo brethren did. But lately it seems a different trend in the big horsepower trucks is dominating, singles. One turbo. Just like what comes stock on your truck. Nothing fancy. But they’re making huge and reliable power with them. Recently I’ve had a few people ask me how this is possible and why it makes sense to run a single, it’s simple, I’ll explain why.

HIGH RPM SAVES PARTS

To understand part of why a single makes sense you need to know this: assuming you have the correct supporting mods (upgraded valve springs being a perfect example) high RPM saves parts. There’s more to it than this but think about water skiing, you need some speed to skip across the water and without that speed the water will “grab” you and you’ll fall/sink. Same sorta idea with engines, transmissions, transfer cases, etc., at higher RPM the parts don’t see the stress they do at low RPM. Parts skip off each other better instead of digging into one another, causing damage. Plus at high RPM the parts already have momentum, adding more power up top will be kinder to the rods compared to adding power down low.

COMPOUNDS

Many people call two-turbo compound turbo systems “twins.” While we all know what this means, it is not the correct name. “Twins” are two identical turbos feeding the engine on their own. Another correct phrase for this setup would be “Parallel Turbos.” Compounds are one turbo blowing into another. So you get the first stage of compression via the large turbo (AKA. the Atmospheric Turbo), then that pressurized air is fed into the smaller turbo (AKA. the High Pressure

Turbo) for its second round of compression before it’s pumped into the engine. So this system essentially compounds the air charge, hence the name. Traditional triples are three of the same or roughly the same size turbos, two blowing into the third. Multiple reasons behind this technology, more air obviously but a big part has to do with the cost. Buying three small frame turbos is generally cheaper than buying one large and one small frame turbo. With a compound system the benefit is you get power down low in the RPM as well as up top. Turbo lag is extremely minimal for smaller systems, when setup correctly.

SINGLE TURBO

A single turbo setup is fairly selfexplanatory. One turbo feeding the engine, only one stage of compression. For most of this a small single turbo for our daily drivers is all we need. Sure standard non-vgt turbos have some lag, but if the turbo is kept small enough it’s minimal and doesn’t affect drivability. On the flip side larger turbos will have more lag and take longer to create boost. So when running a single fixed AR turbo the charger really needs to be matched to how the truck is going to be used. Today’s Variable Geometry Turbos (VGT) offer the best of both worlds. They spool almost instantly but also open up for high RPM power. The negative here is they are known to create a bunch of backpressure and they have a limited lifespan compared to non-vgt’s.

SO WHY SINGLES NOW?

Well, they’re simple, reliable and for most of the race applications they help keep parts alive. Less moving parts to tune and deal with plus, remember the RPM discussion earlier? Using one massive turbo means the engine needs to be high in it’s RPM range to spool the turbo, which means it’s not making significant power until the engine is really spinning. So that means a significantly lower chance for damage to internal parts. That and nitrous. The use of nitrous can provide all the air an engine needs and systems controlling the injection have become much easier to use. Adam