4 stroke cycle

Suck, Squish, Bang, Blow - Part 1: Everything You Ever Wanted To Know About Engines
(But Were Afraid To Ask)

By Mike Kojima

Have you ever gotten soundly beaten at the strip by a lesser car that you should have smoked?  Does your buddy with his almost stock identical car pull away from you in a roll-on consistently even though you supposedly have all the best bolt ons?  Tired of losing in front of the crowds at events?  Does the local “Guru” who works at your friendly neighborhood speed shop intimidate you with quasi-scientific BS when you try to buy something?  How do you know if the mail order house phone salesman is giving you the straight scoop on that camshaft he is recommending?  Which of many turbos on the market should you get for your car? If these questions seem familiar, then this series that we are launching is something you should read!

In the coming months we will explain all of the basics of how to extract more power from that noisy chunk of metal connected to the wheels.  Your new knowledge can be put to good use when selecting hop up parts for your ride, helping you make good solid choices of where best to spend your hard earned money. With knowledge you will be able to make informed choices when buying parts and will be less likely to get punked by unscrupulous mechanics. In this series we will explain how all the popular hop up parts work, how to understand there specifications and how to pick the right parts to best fit your needs.

To understand how the latest in speed parts work, you first need to understand how an engine works! Let’s get down to it and see what makes a basic automobile engine tick.  We will break this down into its most simple basic elements because we need to make sure all of you readers are on the same page.  If you are an advanced guy, you might not need to read this but let's not make any assumptions about anyone's abilities.  We will be getting into the most advanced concepts of engines soon enough as we all progress in our base of knowledge.

Cars are, for the most part with the exception being the Wankle cycle rotary Mazda, powered by what is called a 4-Stroke engine.  A 4-Stroke refers to the 4 strokes in the power cycle, the intake stroke, the compression stroke, the power stroke and the exhaust stroke.  We will explain those in a minute.  The 4 stroke cycle is how an explosion of gasoline and air can be smoothly transferred into useable power to hurl you down the quarter mile or take you to work.  Technically, engine is the correct term to use for a cars power plant because the other common term motor, really applies to electric motors.

An engine also has some major parts, the block, the crank, the rods, the pistons, the head, the valves, the cams, the intake and exhaust systems and the ignition system.  These parts work in close harmony in an exacting manner to harness the chemical energy in gasoline, converting many small explosions of air and fuel into a rotary motion to spin your wheels and hurl you down the track.

Lets start with the main parts first:


The block is the main part of the engine that contains the reciprocating components that harnesses the explosive power of gasoline.  The block has bores, cylindrical holes that the pistons slide up and down in.  The number of bores equates to the number of cylinders.  A four cylinder will have 4 bores and 4 pistons, a six cylinder will have 6 bores and six pistons, an eight cylinder will have 8 bores and 8 pistons and so on.  The block also contains passages for cooling water and lubricating oil.  Blocks are typically made of cast iron or lightweight aluminum. 

4 cylinder block Nissan SR20DE
The block is a large casting, aluminum in this case.  The round bores are called cylinders that contain the pistons.  The cylinder head bolts to this side of the block.
bottom of the block SR20DE Nissan
The bottom part of the block holds the crank which rests in these round saddles contained by caps that bolt to the top of the saddles.


JE Forged pistons
Pistons are aluminum slugs that slide up and down in the bores.  They are connected to the rods by the pins shown here.  These are forged JE racing pistons.
JE Forged piston
In this side view of the JE forged piston, the rings fit in the grooves machined around the top of the piston.
piston rings
These are piston rings, they fit into the grooves in the pistons and help seal combustion pressure in the cylinder and combustion chamber.

Pistons are cylinders of aluminum that slide up and down in the bores of the block, the top of the bores being closed off by the cylinder head (we will talk about the head later).  To make driving power, a flammable charge of compressed gasoline and air contained within the cylinder is ignited, and the piston is forced down the length of the bore toward the open end of the cylinder, away from the cylinder head with great pressure.  This is the basic premise on how an engine works.  The piston has rings, which are thin, circular, springy metal seals that fit in grooves around the top of the piston.  The rings job is to help seal combustion pressure from blowing past the piston, loosing much of the power producing pressure.  The rings also help scrape lubricating oil off of the cylinder walls so it does not get burned up by the combustion going on in the cylinder.  If an engine had no rings it would not be able to develop enough working pressure or compression to run. It would burn up all of its lubricating oil in just a few minutes of running as well.

block with pistons
The pistons fit into the bores.


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Thursday, January 14, 2010 3:16 AM
does a rotary have its own cycle? from what i've read it follows a four stroke cycle, just does it a little differently
Mike Kojima
Mike Kojimalink
Thursday, January 14, 2010 4:57 AM
Its more like a two stroke.
Thursday, January 14, 2010 7:48 AM
Sounds like your neighbors like Acuras and need to pop the hood from time to time.
Thursday, January 14, 2010 8:07 AM
Is this the original series from SCC or is it re-written for this site? Glad to see it back, I only have a few of the original parts and would access to the whole archive!
Mike Kojima
Mike Kojimalink
Thursday, January 14, 2010 8:13 AM
I am the original writer of the series and I am updating it and re writing it for whats up now days. I took a lot of the original references to street racing and stuff out and am using newer more modern parts and will be explaining some of the newer technology and thinking in later parts.

Currently its at a simplistic level but I need to start with the basics.
Thursday, January 14, 2010 8:22 AM
To elaborate, a piston reaches TDC twice for every power stroke: Once to compress the A/F mixture for combustion and a second time to push the spent gasses out the exhaust port. In a Wankle, power is produced every time a face of the rotor reaches "TDC." After combustion, the spent gasses are carried to the opposite side of the rotor housing where it is extracted, so that face of the rotor can repeat the compression/combustion every time around essentially replicating a two-stroke cycle.
Thursday, January 14, 2010 1:34 PM
....that's why is not very EPA frendly...lol.....but super efficent.
I wish they were more reliably (those apex don't seem to last long) and from what I read, they have to be replaced every 50K or so. (I don't know if that's true or not)....
I also read somewhere that RE Amemiya (or R Magic) came out with some carbon fiber seals/ apex, that way they last a lot longer....again, I'm not a Wankel expert, just going by what's out on the internet.
Anyway, I'd like to see more content about forged pistons Mike....more about the differences between high silicon content, which keeps it quiet and tend to expand more), and the one with less silicon content, which tend to "slap" more, be more noisy but be a big more durable.
Whenever you have a chance.
Thanks again for posting informative stuff.
Eric Hsu
Eric Hsulink
Thursday, January 14, 2010 2:53 PM
A rotary has the four cycles but completes them in 360 degrees.

Mike perhaps you knew this when creating it but the title of the article has a sexual connotation to it. Three of the four words words are things that can happen during and the fourth can happen with three people.
Dave Coleman
Dave Colemanlink
Thursday, January 14, 2010 2:54 PM
Look at a rotary as a black box and its like a 2-stroke. Both have one power stroke per revolution, both burn oil, both tend to be loud as fuck, both have unusual power density, both have weak torque and both like to rev.

Look inside a rotary and they have nothing in common with two strokes. Oil is burned for a completely different reason (to lube apex seals instead of crank bearings) and the actual combustion cycle is four separate suck-squish-bang-blow operations. While a single unit of air/fuel has to get through a whole 2-stroke cycle in one revolution, that same unit of air/fuel has 3 revolutions to get its business done in a rotary.

Just like a 2-stroke/nothing at all like a 2-stroke.

Mike Kojima
Mike Kojimalink
Thursday, January 14, 2010 5:41 PM
Dunno, Dave made up the title.
Dave Coleman
Dave Colemanlink
Friday, January 15, 2010 7:48 AM
Its called a double entendre. Its French, you wouldn't understand.

Eric Hsu
Eric Hsulink
Saturday, January 16, 2010 8:09 PM
Hahah good one: http://en.wikipedia.org/wiki/Double_entendre
Saturday, January 23, 2010 12:35 PM
I learned it as suck, squeeze, bang, blow. A bit easier to say than intake, compression, ignition, exhaust. It also doesn't alienate the uninitiated quite as readily when asked "how does an engine work?". Sexual innuendos break down the "engineer talk" barrier and are really easy to visualize (however inaccurate the visualization might be). Heck, tongue in groove explains itself...
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