What do you prefer, turbo or supercharger?

djvj said:

Great info! So SCs don't need as much babysitting. I was reading that SCs produced boost at higher RPM and turbo at lower. But you say they are consistent.

Only thing I wasn't crazy about SC's were the sound, they sounded more high pitched and ramped up with RPM and sound clips seemed annoying to me. I liked clips of turbo sounds much better.

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I guess I need to clarify my statements.

SCs will indeed produce more boost at higher rpms than at lower rpms as the SC is directly linked to engine rpm by the belt(s) powering the SC. The direct relationship between rpm and boost means the SC produces a more consistent boost. This means, all other things being equal, a SC setup for the Slingshot should always produce the same outputs under the same conditions in every Slingshot the system is installed in. Because of this consistency, gauges are not considered as important for SC operation. It's probably still a good idea to at least monitor AFR, if not also boost pressure.

Turbos can produce more boost at lower rpm, but this can be a problem on the Slingshot, since the Slingshot can already spin the rear tire w/o any forced induction. Since turbos are driven by exhaust gases it is possible for them to produce varying levels of boost under the same conditions. This isn't usually a problem, but can be under certain conditions. Since boost can vary somewhat, most turbo owners run boost and AFR gauges.

Some gauges are built to monitor both and even provide feedback to shutdown boost if your system is setup for that, but do not seem to work well with existing TCs, SCs and ECU reflashes. Reportedly, some boosted owners are trying to get the issues sorted out. I bought an Innovate SCG-1 for my Hahn turbo system, but will probably only use it to monitor boost pressure and Air-Fuel ratio until someone hopefully figures things out. AEM also makes a unit that can control boost, IIRC.

Some people like turbos and others prefer SCs. Some for consistency of boost. Some for the sound.

I hope this clarifies what I tried to state above.

A supercharger is a belt-driven centrifugal compressor. At low speed the compressor is turning "quite fast" because of the belt running off the engine, and it creates boost. As the engine spins faster the belt turns the compressor faster and more airflow is created, continuing to add power to the engine. This relationship continues until at some point the compressor fan loses efficiency and spinning it "faster" creates "a little more boost," and the supercharger suffers "boost falloff." Think of a little battery-powered hand fan with a 3" blade--it cools your face, and the faster the fan blades spin the more it cools you off--up to a certain point--past that point you can spin the blades as fast as you want and they won't do anything noticeable (beyond cooling your face). You can upgrade to a box fan to cool your whole body, but the bigger fan is going to move more air at lower speeds and cool more than just your face, so there are tradeoffs, including using more energy at low speeds (called "parasitic drain" of the supercharger).

Turbochargers are superchargers, but instead of being driven by a pulley and belt off the engine, the pulley is replaced with a radial-inflow exhaust gas driven turbine (turbo). It's really a turbine driven supercharger, or turbo-supercharger, or just turbocharger. Low exhaust gas speeds don't spin the exhaust-driven fan very fast, so the compressor fan which is on the same shaft also doesn't spin very fast, and doesn't do any compressing. Now you floor it and dump all this exhaust gas into the exhaust fan and start to spin it up, which also spins up the compressor fan and starts to create boost, and that process repeats and repeats and you're waiting on it...this is "turbo lag." Turbochargers don't have power at low RPM (not true any more, but hold that thought for now). However, at higher RPM there's plenty of exhaust gas to spin the exhaust turbine, so there's no lack of compression from the compressor fan at high RPM--meaning turbos don't produce power at low RPM and produce lots of power at high RPM.

From the factory, the Slingshot has "too much" power at low speed, and not enough at high speed (where wind drag slows it down). A turbocharger is the perfect fit, power where you want it. About that lag: Modern turbos are much lighter than the older turbos, so they don't have lots of mass, meaning the lightweight fans spin up quickly. Also, If the turbo is sized correctly, the exhaust gasses at low RPM can be used to spin up the exhaust fan "early" and create boost at low RPM, eliminating lag--the down side is you can floor it at low RPM and create more boost than the engine can handle, blowing it up.

In summary, the turbocharger is perfect for the Slingshot, except you have to be careful not to blow your engine up at low RPM, and since the exhaust and therefore compressor fan doesn't match engine speed a bunch of stuff is needed to get rid of extra boost created in certain situations so your engine doesn't blow up (it's a common theme).

To make things a little more fun, the supercharger guys didn't sit around idle, they worked on compressor fan design, belt ratios, flow characteristics, and got less boost at low RPM and more boost at high RPM, without blowing up engines! Win to the SC guys! Mostly. They still have "boost falloff" up top, but it's not much. For the normal person, the supercharger is the way to go--easy to install, maintain, and won't blow up your engine. For the "I must have all the power I can wring out of this engine at all costs" group, there's still the turbocharger, and all its complexity, which will wring the power out of the top end without remorse. (And blow your engine up if you want--there's that too.)

I have a turbocharger, it's incredible fun, and makes way too much power if you want. It also failed and is under repair. (Things happen.) Squirrel loves the power, but for her we'll eventually put in a supercharger, they give almost as much fun but without all the risk, and they're much easier to maintain with no gauges to keep an eye on, just have fun!

You have to understand how they differ to understand why you might feel one is better than the other for your needs.

A supercharger runs off the motor so it is parasitic drag. You are using horsepower to make horsepower.

A turbocharger runs off the exhaust so it's free horsepower.

That right there is why I am such a proponent of turbos. Nothing beats free power.

With a smaller turbo like the Alpha Precision turbo, turbo lag is almost non-existent. The bigger the turbo, the greater the lag on building boost.

Obviously my turbo bias is apparent by the above but it depends on what you want. A supercharger is unquestionably easier to install if you are not mechanically inclined. Here in Colorado turbo's rule because of our thin air - at 13K feet in the mountains you don't want anything adding drag on your motor. You'd be amazed at how much the thin air taxes a motor.

The bottom line is neither is safer for a stock motor if you over-boost (either by changing pulleys on the SC or increasing the spring rate on a TC).

Take into account what you can afford and how your mechanical skills are and go from there. A good, complete turbo outfit like the Alpha includes everything including the intercooler. It also has the CAI put in the optimal area for cold air flow. Some of the lesser kits do not include an intercooler and the air intake sits right off the turbo. Nice and hot air there (something I do not like about the Hahn).

Without getting into the technical side of the issue, since that is not my area of expertise, I thought I would provide my observation of the economic and mass production side. Last year I bought a new car, a 2017 Ford Mustang. It has a smaller engine than my Slingshot - 2.3 liters.
It is turbocharged from the factory and provides 310 hp, using premium gas. For what it is worth, Ford engineers decided that this was the way to go for their small engine to get lots of power and still provide some fuel economy.
I find that the car goes pretty good with the 6 speed automatic transmission and can keep up with most others on the road. Passing is no problem and one time, I saw 100 mph on the speedometer with it not feeling that fast and not trying.
Why did they choose to use a turbo instead of a SC? Who knows, except those at Ford, but they made a good choice for a mass produced vehicle that would surprise many that have been passed if they knew they have been passed by a 4 banger.