supercharger

[Carleton]

Hi
Can some explain to me in laymans terms what a supercharger does for an engine and how it difers from a blower or turbo.

Thank you
Carleton

[Cobra20646]

Carlton,

At the school I attended, a blower and a supercharger were one and the same.

- Jim -

[Horse]

I will try to put it in readable english as I understand it ok?

1. Superchargers and Blowers are two words used to describe the same thing.
2. The supercharger is usually run off of engine power (usually by a belt or similar device- sometimes gears) and changes the engine intake from a vacum to a pressurized area. There are a multitude of different types of superchargers so I wont even go into it. But the most common are the roots (twin rotor) and a centrifical (like the compressor side of the turbo).
3. The Turbo is actually called a turbo-supercharger.
4. The turbo usually runs off of the spent engine gasses (exhaust) and uses these gasses to turn a turbine. This turbine is connected by a shaft to a compressor wheel. as with the supercharger it pressurizes the intake charge to add more air to the sylinders as the intake valve opens.
5. As an internal combustion engine is only an airpump - it would zstand to reason that a pressuriozed system would work better than an atmospheric one would right? (try to run a oneumatic drill by hooking up to the air and pulling the trigger- then to a pressurized air line and do the same- obviousl result but a good comparison for a forced induction engine)

[auto10x]

A supercharger supplies air to the cylinder at a pressure above ambient.
The term blower stems from the unit that blows air into a naturally aspirated two cycle diesel. Sounds contradictory, but it's true. This blower was taken from these engines (Detroit diesels) many years ago and adopted for high performance spark ignition engines (hence the terms 4-21, 6-21, 8-21. 6-21 = 6 cylinders, 21 cubic inches each.). When they were/are used on SI engines they do indeed operate as a supercharger, supplying air to the engine at above ambient pressures.
Sorry to be technical, but the truth is the truth.
auto10x
Bill

[Jeff Frigo]

Bill:

You mean 71 not 21 right?

[niles]

I would appreciate some serious dialog on this subject.

given that 10:1 is about the limit for pump gas. How does a blower allow a 9:1 motor to have 6-8 psi boost without detonation? Is the max compression psi the detonation limiting factor? If so, then I don't understand how blowers help?

I would like to get a technical blower thread going. Can I put a "little " blower on my 10:1 or do I need to build a new motor?

The ease of bolting on an additional 100 hp is interesting; but somehow I think there must be a catch-no free lunches normally apply

gn

[Bill Wells]

niles...

there is NO ease in bolting on 100 hp via blower addition ...there ain't no bolt on kits for most blowers except for 289/302s, at least the old style ball type blowers. others i am not familiar with. . custom fitting and custom bracketry is not ease-y either.

re your 10:1 compression ratio, build a new motor between 8.5-9.0 : 1 compression...make sure your pistons are forged and not cast...and the list goes on.....

bill.

[MJN]

If you really want to understand the subject there are numerous good books out there that cover the fundamentals very well in an organised fashion and will be probably be much less confusing than the kind of disjointed info that you may get from many posts here. Corky Bell has two good books one on supercharging and one on tubocharging that are excellent for understanding the fundamentals of forced induction.

Bottom line is that an engine is an air pump, the more air in the more power out. So if you can force air in at twice atmospheric pressure (14.7 psi boost) you will double the power output. Not quite true due to pumping losses and flow restriction etc but you get the idea.

A lot of people consider forced induction cheating, but once you've tried it you'll understand how you can easily become addicted to boost.

[Excaliber]

Horse

"4. The turbo usually runs off of the spent engine gasses (exhaust) and uses these gasses to turn a turbine."

I can't think of any example of a "turbo" unit NOT being driven by the exhaust system. The term "usually" implies there is some "other" way to drive a "turbo"?

Turbo and Blower/Supercharger are TWO different animals! The turbo IS driven with exhaust (or some other fluid or gas that I'm not aware of?).

The blower/supercharger IS driven by belt, gear or some other mechanical means, other than fluid or gas.

Other than that, they do the same thing. Suck in outside air (the cooler the better here) and "compress" it into a small space (the combustion chamber)! This dramatically raises the "effective" compression ratio by at least 2 or 3 points.

7 to 1 becomes 10 to 1 with enough "pressure boost". 10 becomes 13. Some engines run 13 to 1 naturally aspirated, (NA), but thats a pretty radical race motor! At that extreme you better have your fuel/air ratio dialed in PERFECT. Your timing ON THE MONEY! And heavy duty pistons, rods, etc.

A stock mid 90's Ford 302 can EASILY handle a modest boost of 5 psi without any other "heavy duty" parts or compression ratio changes required. YOu COULD kick it up to 9 or 10, but your pushing the "envelope" of a stock motor.

More than 10 psi? FIRST thing I would do is throw out the hyeperuretic pistons. If you don't, the extra compression WILL, lol.

Ernie

[Horse]

thanks excal- I wanted to put in the info I knew for sure- so I didnt want someone coming out and saying "We have this revolutionary . . ." KNow what I mean?
well I think I remember talking to thomas one day about a superchager system that was run with the engine gasses- but I dont remember much about it- except it was all theoretical -

[Excaliber]

Know what I mean??

Sure do! I "usually" take the safe route too, 'cause you just never know who might pop up with something you never heard of,,,,,,,,,,,yet. LOL

Ernie

[750hp]

Originally posted by niles


I would appreciate some serious dialog on this subject.

given that 10:1 is about the limit for pump gas. How does a blower allow a 9:1 motor to have 6-8 psi boost without detonation? Is the max compression psi the detonation limiting factor? If so, then I don't understand how blowers help?

I would like to get a technical blower thread going. Can I put a "little " blower on my 10:1 or do I need to build a new motor?

The ease of bolting on an additional 100 hp is interesting; but somehow I think there must be a catch-no free lunches normally apply

gn

Niles,
Factors such as cylinder head combustion chamber design (quench), cylinder head material, camshaft lobe centre and duration, piston shape, supercharger design and efficiency and fuel octane rating all affect the wellbeing of your engine when running a supercharger.

Because you have a Cleveland, I'll jump to conclusions and guess that you're running open chamber 4V heads. this chamber desing is as blower friendly as you can get in an iron head. Alloy heads can dissipate heat more efficiently than iron - therefore making alloy heads the best option for combatting detonation.

A camshaft with a fair amount of duration will bleed cylinder pressure, making things safer. A bit of boosted air straight out the exhaust is no big deal! I think over 240 degrees duration would be nice.

Good quality forged pistons would be a mandatory option for any blown engine of mine.

A roots blower (B&M, Holley, Weiand, BDS, Littlefield, Kuhl, Mooneyham etc) is by far the easiest installation, and can use your carburettor on top. Downside is the extra height of the blower on top of the manifold, and the significantly lower efficiency of the blower. They use more horsepower through frictional loss, and add more heat to the compressed air. More heat = less air density (less oxygen), and greater chance of detonation. Intercoolers are also more expensive and add even more to the height of the motor.

A centrifugal blower (Vortech, ATI, Powerdyne, STA etc) is more efficient and can be packaged below the hood - anywhere in the engine bay, as long as the blower pulley still lines up with the crank pulley I've never had anything to do with carb'd centrifugal blown applications, but I'd say that there'd be a lot of sorting out to do. Otherwise, it's $$$ for the EFI conversion.

A Screw compressor (Kenne Bell, Sprintex, Whipple, Lysholm etc) is similar looking to the roots blower, but has a more advanced internal rotor design to compress the incoming air within the blower casing, rather than just displacing XXX cubic inches of air per revolution (as the roots blowers do). It is more efficient than the roots, but cannot match the centrifugal for peak horsepower.

I had a B&M 144 blower on a 302 with 10:1 KB hyper pistons, and running anywhere near the ignition timing that the motor needed to make power resulted in crank pistons - around the ring land. Forged 9:1 pistons alone stopped the carnage, but detonation was always a concern on a hotter day. Running Avgas 24/7 would have solved the problem entirely, but I wanted to use the car daily and I was too tight to spend the extra money.

My new motor is 8.5:1 compression, and I'll be running more than 20lb boost. The old theory was that you halve the boost value, and add it to your static compression ratio to give you an effective "running" compression ratio. So how does 18.5:1 compression work with 98 octane pump gas? Custom designed camshaft, 18 degrees total timing, alum heads, lots of fuel (96 lb/hr injectors), 24"x12" intercooler, JE custom pistons and careful mapping on an engine dyno.

[Junket]

This might be a site for information http://www.kuhlsuperchargers.com/p3%20tech%20help.htm had a Daycruser ski boat motor from these guys 800 hp in the late 70 and it was a handfull when you hit the loud peda.
Kenl

[PSB]

Niles,

You don't even have that Cobra on the road yet, and you're wanting more power already?

Pete

[got snake?]

Pete? Aren't you done yet?

GS

[PSB]

GS - I'm nowhere close - I was hoping to make DVSF this year, but it's not going to happen

Pete

[niles]

750 hp:

thanks for the tuitorial 101 on blowers.
I have have closed chamber, worked on 4V's that flow 300 cfm. So guess I'll just have to learn to drive the 500 +hp cleve. and leave a blower for another engine.
gn

[aumoore]

Niles
Right now my little explorer will outrun your big bad cleveland because you have not finished with the car yet. Finish the car and you might find that you have too much HP for now. After you get used to it you might want to upgrade the motor.

[ls1ac]

I have been using a Whipple on a 454 in a suburban for a tow truck for the last 9 years. Started with about 9.75/1 and about 6in at max. It could spin all four wheels on startup; my son took it to the drag strip and could better many 5lt.mustangs. After about 120,000 miles I was hauling a racecar back to Wi from Or and got some bad gas in Wy. It needed 93 to run wide open and even with the additives to the gas in Wy (when I heard the ping), It put a piston on its side. I rebuilt the engine at 9.00/1 and have been going for an other 80,000 miles. I had hoped to go to 7in of boost but could not get the pulley small enough and keep the belt alive.
The Whipple is unusual in that it is after the throttle body on top of the intake. This means that when running easy there is a high vacuum before the screw with a TBI, this gives better mix and gas mileage, if you can keep your right foot from “falling” to the floor. The other nice feature is that the parasitic’s are less than a roots while near open throttle.

[SCOBRAC]

All internal combustion engines run on three things.. fuel, air (oxygen) and spark.

Superchargers / blowers / turbos of all types all do the same thing. They take ambient pressure, barometric pressure (regardless what it is) more at sea level less at 10,000 feet and densify it with the fuel air mixture.. Literally compressing the gasses.. The more the better.. (to a point) Too much pressure and well, we have all see blowers explode.. Detonation is a problem you can't run 34 degrees with a blower.. You might only need 20.. or 25. Too much ignition will be the fastest way to a new set of pistons or worse.

As far as 10:1 with a blower.. You can't.. 8.5-9.00 is pretty standard with a small blower. It all depends on the blower. I have seen CR's as low as 6:1 with lots of blower.

The more gasses you oxidize the more efficient the engine, No2 (nitros, as wellas nito-methane for that matter) does the same thing but in a different way..


The thing is... WHY?? You can make tons of power on a 10.5:1 small block or even a big block. I see Chevy guys getting 635 hp and even the small blocks right at 500.. 500 hp in a 2500 lb car is 5 lbs per hp.. NASCAR winston cup cars are somewhere about 4.5 lbs per hp..