Why turbos?

In a nut shell "FREE POWER", the super charger takes power from the engine to make power. The turbo on the other hand merely utilizes the exiting thrust of the spent fuel to spin its impeller, non-parasitic.

Jerry Randolph '90 Red

They don't. There are quite a few belt-driven superchargers as factory options. Chrysler offered one on the Sebring, didn't they? I know Ford offered a supercharger on trucks and I think on some of the small V8s.

More boost.

A SC is not really less complicated. A SC needs to be belt driven, which means finding space and making the appropriate brackets and pulleys to get power to the SC. A turbo needs to be near the exhaust and then have the intake plumbed to it. After that, the two systems are similar. They will both require fuel system upgrades and it would be good idea to also had an intercooler. One good thing about a turbo is that power potential is higher than with a SC. You are also energy that would usually just go out the tailpipe, so it can be more efficient.

------------- Alex

Ford did the Super Coupe Thunderbird a while back.

more boost = more power. :)

-------------- Alex

Why look at old offerings?! Doesn't Mercedes offer supercharged C and SLK right now?

-- Marcio Watanabe

Despite the correct other responses, it is not clear to me either. A turbo is however clearly more efficient by the numbers.

Sure, a belt supercharger is much more driveable, without the finite time lags of the turbo, and sounds much better. But neither of these are easily put into numbers that bean counters, (read: many potential buyers,) can use.

Returning to the issue at hand, the JR aftermarket SC for the Miata has lots of lag too due to the time needed to fill all its intake piping. And it uses various compromises to trick the engine controls to get the fuel it needs from an engine system not designed for it.

So a factory turbo does sound like a very interesting idea to me.

Leon

A good primer on SCs is a three-part series found here:

SCs are a parasitic power generator, but can be more effifient and effective than many other power adders.

Turbos do generate boost from the exhaust (waste) cycle, but are not "FREE" energy. There are complicated plumbing issues that need to be engineered and turbos tend to have heat issues associated with them as well.

Currently, automakers use a near even balance of SCs and turbos in production vehicles. -- It all depends on the application. Which is what the root of the problem boils down to; "What are you going to do with the vehicle, and how much are you willing to pay to play?"

- L

"Oh bother," said Pooh Bear when he saw the mushroom cloud...

// Change TEJAS to TX to reply via eMail //

Very true. I haven't done a survey, but I'd guess that the Roots-type SC is used mainly in low-boost, non-intercooled applications. Air-to-air intercoolers cause significant pressure drop with positive-displacement blowers, and matching the engine, compressor, and intercooler is critical. Throttled volume is the enemy, and most applications involve moving the throttle to the upstream end, the worst-case scenario in a Miata. SCs tend to be used on engines that don't need much extra power, or couldn't survive it.

It's much simpler to stuff the extra volume of an A-A intercooler using a centrifugal compressor. Pressure is limited by a valve, not by the blower displacement and rpm, so there's plenty of air to play with once the snail spools up, and the throttle can be downstream, at the manifold.

I suspect space considerations are a decision factor in some cases, too. Some engine bays can accommodate one but not the other.

focus svt mini cooper s

4 runner xterra and so on...

all supercharged

dookie

Gee, there is a car in the list.

Leon

Holden in Australia offers a supercharged V6 option on its standard sedan. In the past I know this was severely detuned so as not to outperform the V8 (non-supercharged) version.

eh? your point?

mine was that superchargers are not uncommon as OEM additions to all sorts of vehicles.

dookie