learn me superchargers

I consider myself to be well versed (enough) in turbocharger theory, but I'm completely in the dark when it comes to superchargers.

Does anyone know any links that do a good job of quickly teaching a turbo savvy-ish person about superchargers?

It seems to me a lot of people are running supercharger setups without an intercooler. I thought superchargers blew hotter air? I could be wrong here.

And what about the different types of superchargers. Roots, eaton, centrifugal?

And finally the basic question.. under low load cruise will a supercharger drag enough to effect gas mileage?

which reminds me

k20 + m62 + bolt ons

Any time you compress air it gets hotter. Not running an IC is just a function of either cost or packaging, but either way, I don't recommend it.

Roots and Eaton blowers are the same thing. They make great hp at lower RPM levels, but they're not efficient at higher RPM. That's the point at which centrifugals and twin-screws like Whipples and Lyscholms make great power.

If you have a bypass valve, gas mileage won't be affected at all with a blower.

other than overall packaging, what would be the strengths of using an m62 over an m90? usually with turbos you size them properly so they spool at the rpm range you need them most, but my (limited) understanding of roots blowers is that there is no "spooling". They are spinning as fast as they are going to spin at a given engine RPM all the time.

so do you increase boost pressure by going with a larger supercharger?

is there an increased amount of drag when cruising with a larger supercharger?

everywhere i read, turbos on paper are better than superchargers. more efficient at moving air, lower charge temps, ability to easily vary boost levels, less drag on the engine at cruise... yet there has to be a reason why superchargers are used. 'turbo lag' and low end torque?

Taiden wrote: everywhere i read, turbos on paper are better than superchargers. more efficient at moving air, lower charge temps, ability to easily vary boost levels, less drag on the engine at cruise... yet there has to be a reason why superchargers are used. 'turbo lag' and low end torque?

Don't forget packaging, cost and ease of installation and removal.

Taiden wrote: so do you increase boost pressure by going with a larger supercharger? is there an increased amount of drag when cruising with a larger supercharger?

By changing the pulley on the supercharger, you control how fast it spins and how much boost it will produce.

I'm not as familiar with screw-type and such, but Centrifugal superchargers build boost with RPM, in a linear type fashion.

Someone please correct if I am mistaken.

Taiden wrote: other than overall packaging, what would be the strengths of using an m62 over an m90? usually with turbos you size them properly so they spool at the rpm range you need them most, but my (limited) understanding of roots blowers is that there is no "spooling". They are spinning as fast as they are going to spin at a given engine RPM all the time. so do you increase boost pressure by going with a larger supercharger? is there an increased amount of drag when cruising with a larger supercharger?

Other than packaging, the larger M90 is going to have higher intertia due to it's parts being larger and weighing more. I don't know if it would be enough of a difference to be noticeable.

You can increase boost by going with a larger supercharger or by spinning the supercharger faster (instead of 1.8 supercharger revolutions per engine revolution you change the pulleys and make it 2.1 supercharger revs per engine revs - note, these numbers were pulled out the air). There are limits to how quickly the supercharger can spin. You can spin it so quickly it breaks, though this is unlikely. The likely thing is that you spin it so fast that it can't efficiently compress the air, so you end up with really hot air or you lose boost. Likewise, spinning it too slowly won't put it in it's max efficiency area, so you might need to go with a smaller supercharger instead of the bigger one. If you're familiar with turbo compressor maps, a supercharger compressor map will make sense to you. Eaton posts their's on their website.

Eaton Supercharger Site

Bob

I believe a smaller blower pulley will make more boost, not a larger one.

A larger supercharger will not make more boost pressure, but it will move more air with each rotation, requiring less boost to move the same volume of air, thus producing less heat.

Read the Forced Induction chapter of How To Build a High Performance Miata.

The reason you don't see intercoolers on superchargers as much is that it's harder to do right. Superchargers put the throttle body before the charger, so you've got greater throttled volume. Throw in some drag from the blower and now you're starting to have some hassles dealing with idle control. Air/air intercoolers add to this throttled volume, making things worse. So a lot of aftermarket supercharger manufacturers just close their eyes and ignore it. In fact, superchargers are less efficient than turbos at compressing air so they actually need the intercooler more.

I'm only talking about positive displacement superchargers here - Eaton, Roots, Whipple, twin screw, etc. Centrifugals act more like a turbo, but without that pesky boost down low Centrifugals need bypass valves, keep the throttle body in the stock location, etc.

Superchargers do affect gas mileage slightly. The bypass is a good step, but it doesn't completely compensate for the fact that you're spinning a mechanism around. We usually see about a 1-2 mpg drop in fuel efficiency with supercharged Miatas and a 1-2 mpg gain with the turbos.

Keith could you speak towards the differences you find in comparable supercharger and turbocharger setups on those 1.8L miatas.

I feel like a lot of people start out with the idea of going with a supercharger, and then scrap it for a small turbo setup.

I figure you're the person with the most experience doing something similar to what i'm aiming for. (Low end torque on a 1.8L 4 cylinder using forced induction on a nothing special motor (no VVT or VVL etc)

The biggest difference is usually in the implementation. You've got to choose the right hardware - size of the blower/compressor - and mount it right. Get the right turbo and it'll have low end torque. Get the right supercharger and it'll keep pulling hard to redline.

It's actually harder to do a good supercharger system in a lot of ways, as you've got to get your belt alignment juuuust right and manage to transfer a fair bit of torque through the belt without resorting to massive tension. An MP62 spinning fast enough to make 10 psi of boost on a Miata eats up 36 hp - and that's all run through the belt. Then you have to deal with the driveability problems due to the big throttled volume, and now we get into intercooling. It's a lot easier to put together (or buy) a turbo manifold and downpipe.

However, superchargers are a bit easier to tune off-idle because they're quite linear. x rpm * y throttle = z boost, every time. They're also more resistant to detonation thanks to the low backpressure, which does help make up for the lack of intercooling somewhat.

Generally speaking, I like turbos better. They're just better mannered, with less vibration and noise when you're not on it. The shriek and instant hit of a super is a lot of fun, though. There's a hard edge to a supercharged car that you just don't get on turbos unless you're romping around at high rpm.

Here's a comparison you might enjoy. The Janel in the story is my wife. Yes, it's being used to sell FM turbos. But she's convinced, and don't you even think about taking her turbo away from her.
http://www.flyinmiata.com/turbos/janel.php

Also check out the Eaton supercharger site, has some tech info, maps, etc. Compared to a turbine compressor (turbo, centrifugal), most superchargers are less energy efficicient. Much of the extra energy winds up heating the air. So yes, an IC is highly recommended. But the boost level is largely independent of RPM, ie 7 psi from 500 RPM - 8,000 RPM. For part-throttle cruise efficiency, many setups offer a vac controlled bypass system that recirculates air around the compressor. And technical advances in manufacturing and materials have reduced the friction and sealing losses dramatically. So it all depends on what your goals and application are.

I created tho spreadsheet to let me play with various configurations of pulleys and supperchargers an various motors. Down at the bottom I was messing with air flow to see how pipe diameter would effect the air flow. It is far from perfect but fun to play with.

http://www.ehadesign.com/~dsmith/ENGINE_AIRFLOW.htm

Oh, look: a Chinese zombie paddling a canoe. That's something you don't see every day.

Well even though this thread is old, I give you an Audi (Eaton) factory supercharger with intercoolers. Water I'm guessing? It's the two black hoses and the two straight parts that run the length of it.

Will wrote: If you have a bypass valve, gas mileage won't be affected at all with a blower.

I'm going to go ahead and disagree with that. The Manic Miata has an intercooled twin-screw Whipple with a bypass valve. To support that it is running a high pressure fuel pump and oversized injectors driven by an ancient but pretty well tuned Link ECU. It will not break 20 mpg, certainly not when driven in anger.

I have a boost gauge on it so I can see when I'm in and out of real boost. If you babied it all the time, it might get better economy... but then what would be the point of the blower?

[edit] Wups. Date check fail.

Superchargers have rpm limits (fairly easy to find for common roots stuff like m62 and m90). Boost level is 'controlled' by the pulley ratio between crank and SC pulley sizes. Your pulley ratio is limited by what the supercharger RPM will be at your max engine rpm. Whatever boost you get at that pulley ratio is what you get. To raise boost beyond that point you would have to move to a higher displacement blower. Non-intercooled factory setups are running low boost, so they can more or less get away with it. Non-intercooled race setups are using cooler-burning and higher octane fuels vs street cars. Some higher performance factory SC setups use an intercooler sandwiched underneath the charger that resembles a heater core or ac evaporator.

Even with a bypass valve open, SCs drop mpg. The rotating pieces weigh a lot!

That Audi supercharger is an air/water. I'm having trouble coming up with a relatively modern supercharged production car that uses an air/air, actually.

We're using an air/water IC in our supercharger kits for the NC Miata. That engine suits the blower well, and the packaging is a lot better. Doesn't have the personality of a turbo would, but I've never felt that engine had any personality anyhow.

We used to offer a high performance supercharger setup for the NA/NB Miata. It was a twin screw, and we found it had a pretty narrow operating range. Twin screws are less efficient at lower speeds than Roots-types, so you've got to spin it pretty quick to get good airflow. We found ourselves flirting with the blower redline, it was a really delicate balance. But boy howdy, were they fun when they were working with an amazing shriek.

Keith Tanner wrote: But boy howdy, were they fun when they were working with an amazing shriek.

Mine is still not fully off the sidelines, but:

I have an A&A Superchargers Vortech V3Si Kit on my C5 Corvette, so I am pretty familiar with them.

1. They hurt fuel economy. Went from 28-30 MPG cruise to 25 or so average. Of course, I installed larger injectors, switched to speed density, and raised the fuel pressure during the install, so sort of expected this.
2. They make numbers. 535 horse on a Dynojet on pump gas, stock the car should dyno low 300s. 495 torque, over 300 ft/lbs from 2000 RPM and over 400 from 3500 RPM. Stock LS1 with longtubes, no internal work.
3. It drives like a stock car. This was actually disappointing, I had a bunch of big turbo DSMs and liked the way they felt when they pulled. The Corvette is way faster but has a lot less drama. Power comes on a very linearly without the big surge of a turbo car.
4. The quality of the kit makes a big difference. The A&A kit is really nice and they are great with info and service parts. I bought this kit used and had to source a few items and they hooked me up fast and cheap.
5. Its addicting. The next step will be do to a cam, then heads/big inch forged bottom end, then a bigger blower, with either a flip drive or a cog belt. The car feels slow now.
6. It makes sense from a packaging sense. On the C5, there is not a lot of room for turbos, and most turbo kits are limited in some way. Rear mounted has limitations, twins off the manifold is limited in compressor size and tough to pipe, big singles up front are doable but very tough to maintain creature comforts like air conditioning and a stock routed/exiting exhaust.

What type of setup are you looking for? Or are you just looking for theory?

I have a PowerWorks air to water intercooled supercharger on my Focus. The kit was designed and manufactured by PowerWorks which was at the time a division of Cosworth. The kit uses an Eaton M62 supercharger. Part of the attraction of the kit was that it is CARB certified. The other main factor is that the kit came in two boxes with every last nut, bolt, and piece of wire needed. There was also an envelope to overnight your ECU back to them to be reflashed.

Their tune took my car from 108WHP to 223WHP. Gas mileage in city driving dropped a bit, but I can still get 33MPG on the highway with the cruise control on.

Retuning could get me a little more but I am quite satisfied with this chart.

Interesting note: Cosworth came out with a supercharger for the NC Miata. Made a big fuss about it, check out the cool Cosworth name, we've won F1, rah rah rah.

Turns out they didn't do the hardware engineering at all. It was done by Magnusson, all of it, and Magnusson did a very good job. Cosworth just wrote the check. A third party did the engine management, blew up a bunch of engines and Cosworth walked away. Magnusson was stuck with a whole bunch of superchargers. And now they're the Flyin' Miata supercharger

Keith Tanner wrote: ...I'm having trouble coming up with a relatively modern supercharged production car that uses an air/air, actually.

R53/R52 MINI Cooper S

Eaton M45 with A2A

God I want something supercharged, maybe when the NC prices drop I'll pick one up and give Keith a call.

Now this is another rabbit hole but I would love to know, it seems almost perfect for a supercharged rotary vehicle but it is rarely done (peddit racing had a kit for the rx8 but the renesis was too high compression for boost) anyone know why aside from tuning issues?