Turbocharging "cycle of function" question

[Brocephus]

I am a small arms and artillery repair technician in the US Army. While in school, they taught us the processes, or cycles of funtion, used by most semi- and full-auto weapons. That linear cycle of function is:

Charging - This locks the hammer to the rear.Loading - This loads a round into the weapon.Chambering - This actually puts a round in the chamber.Locking - This locks the bolt closed so the round can be fired.Firing - This is where the magic happens.Unlocking - This unlocks the bolt or slide so it is free of the chamber.Extracting - This extracts the spent casing from the chamber to make room for the next round.Ejecting - This ejects the spent casing from the weapon.

This process repeats continuously until something happens and one of the steps is interrupted (ie. if the trigger, gun won't fire. If bullets run out, gun won't load.)

The same can be said for the internal combustion engine but it is a much more in-depth process to get from the air filter to the tail pipe.

I have been so involved in the design and fabrication of my build that I have had little reason to throw myself into the inner workings of a turbo charged engine. I know what MAFs, CAIs, IACs, TPSs, MAPs, O2s, EGRs, EGT, FMICs, BOVs, and FPSs do. But while I may know what these things are and what they do, I can't say I understand why they do what they do, why they're placed where they are in the chain, and I don't understand what is needed to make a turbo engine run at peak performance. All I have are bits and pieces of what I've heard and read and I'm now at the point that I just need some help putting all those pieces in order.

Would it be possible for a turbo engine guru to come up with a cycle of funtion or road map, if you will, for a typical, stock CA18DET? I'm pretty sure this road map would apply to most turbo engines, but since this is a CA18 forum and I have a CA18, why not get it engine specific?

A written explanation will be great or, if you're the diagram kinda guy, then that'd be great, too.

Many, many thanks in advance.

[sjbsuperman1425]

if you understand what they are and what they do, the "What" is pretty much the why.

and Internal combustion engines are not really that complicated. "MOST" sensors and things of that sort are on an engine for fuel economy or pollution control.

[sjbsuperman1425]

air is drawn in through the air filter and air intake pipe, the through the MAF which reads the amount of air entering the turbocharger. that air is then compressed IE turbocharger, ran past the FMIC which cools the air and passes by the throttle body. the TPS will help ECU compensate how much fuel to add along with the MAF.

the air then passes through the intake manifold into the engine past the valves, which is the INTAKE stroke. during this step, fuel is also atomized via fuel injectors which mixes into the incoming air. COMBUSTION happens, then its the POWER, then the EXHAUST.

Piston pushes exhaust gases out of the head past the valves and through the turbocharger than the O2 sensor reads the amount of oxygen in the exhaust to tell the ECU to either lean or richen the a/f mixture.

thats pretty much the basics of an Internal Combustion engine. The CA18DET does not have a MAP, EGR, EGT, or BOV. The IAC is just what it says it is and does what it is labeled as. the IAC is a air control for idle.

I hope this helps. ANYBODY that objects to anything i've posted or has anything to add feel free. i will not be affended, not that ppl on the internet care lol

[themadscientist]

If it is too basic, not trying to insult you, just disregard if it is of no use. I usually explain engine like this.

same as the ole "triangle of fire"; air, fuel, ignition source. All an engine does is pump air, suck fuel and light it off. Sure the intracacies of tuning it are complex but essentially you are just optimising the balance of those three.

Do something to increase air going into the engine, it will require the balance to be restored with increases of fuel delivery and ignition strength.

A naturally aspirated engine relies on the vacuum created by the piston going down on the intake stroke to suck air into the engine. To a certain degree this can be enhanced by port shape and cam timing to take advantage of the moving column of air. Properly done even when the piston stops moving that air wants to keep moving so a certain amount of air will push its way in past what vacuum alone could, "supercharging" the engine. If a 1.8 liter engine can be set up in a way that it can actually ingest more air than it displaces it can make more power. This concept is taken to a truly formidable level through the use superchargers and turbos.

These devices though driven differently do the same thing, create positive pressure which allows an engine to ingest quite a bit more air than it actually displaces. As suggested before this means more fuel must be put in as well as a stronger ignition source to reliably fire the denser charge. The enery comes from the fuel; the more you can effectively burn on each bang the more power you can generate.

Hope that helps

[Brocephus]

The CA18DET does not have a MAP, EGR, EGT, or BOV.

Ok, what you've written is great and much appreciated. I am intamately familiar with the four-stroke internal combustion engine, but the turbo and sensors required to make it do what it does is still an enigma to me. Your information solidified much of what I already knew, filled in a couple of holes in what I didn't know, and ultimately generated a couple of other questions.

I've heard of guys adjusting their boost and fuel pressure. The fuel pressure adjustment is pretty self-explanatory, but how would I go about adjusting my boost pressure. It would seem to me that a turbo is only capable of producing a set amount of boost at a given rpm without changing wastegate actuators. Is this what is done?

I can see an Exhaust Gas Temperature gauge or, pyrometer, being useful for knowing the temperature of your exhaust gasses, but aside from that, why would someone put one in a car? Are they more useful during tuning than anything else?

I will be installing a turbo timer in my car at some point as I'm sure everyone understands the beauty of not baking the oil in your turbo. But as far as the installation, how are they installed that they are able to keep your car running after you pull the key out? Are they wired into your ECU?

It may sound really cheesy, but there's something to be said for hearing the loud PSSHH of a BOV. If I wanted to install one, where in the chain would it go in relation to the turbo, IC piping (if so equipped), and the intake manifold? Or does it go on the exhaust side of things? I'm tellin' ya, I am a complete noob to this world and know little to nothing about it.

My mid-engine installation may not allow for the bulk of an intercooler. What are some other options to an intercooler? Is water injection a viable option? And if so, are those systems exetremely expensive or can they be fabricated at home?

Lastly, I do not wish to be lumped in with a group of car owners who have done nothing more than added heavy air dams and ground effects, tons of stickers, neon lighting, and a coffee can to their cars. If a turbocharged engine is run without a muffler, will it have an identifiable exhaust note or will it sound like a ricer fart can?

And, many thanks in advance for the time you take to answer my questions.

[meminto]

I've heard of guys adjusting their boost and fuel pressure. The fuel pressure adjustment is pretty self-explanatory, but how would I go about adjusting my boost pressure. It would seem to me that a turbo is only capable of producing a set amount of boost at a given rpm without changing wastegate actuators. Is this what is done?

The set boost pressure (compressed air pressure) although is not dictated by rpm scale, does have a symbiotic relationship with it. Boost is most commonly regarded as psi (Pounds per Square Inch) measurement and you can adjust boost pressure through chaging wastegate actuation (actuation is based on set spring rate, eg. a wastegate spring may need 8psi of pressure to open).

However, instead of changing the actuator you can "fool" the spring by using a bleed valve, manual or electronic, to reduce the pressure to the spring itself, so there needs to be more pressure for the spring to reach its predetermined wastegate actuation.

I will be installing a turbo timer in my car at some point as I'm sure everyone understands the beauty of not baking the oil in your turbo. But as far as the installation, how are they installed that they are able to keep your car running after you pull the key out? Are they wired into your ECU?

There are many different varieties of a turbo timer, but basically you wire it into your ignition switch/barrel, usually they dont tap into your ecu unless it has some extra functionality.

It may sound really cheesy, but there's something to be said for hearing the loud PSSHH of a BOV. If I wanted to install one, where in the chain would it go in relation to the turbo, IC piping (if so equipped), and the intake manifold? Or does it go on the exhaust side of things? I'm tellin' ya, I am a complete noob to this world and know little to nothing about it.

It is plumbed into the intake piping, there are many arguments as to the best location, but generally 5 or so inches in front of the throttle body is a good location.

My mid-engine installation may not allow for the bulk of an intercooler. What are some other options to an intercooler? Is water injection a viable option? And if so, are those systems exetremely expensive or can they be fabricated at home?

Have a look at some MR2 builds, you should find some ideas around..

Lastly, I do not wish to be lumped in with a group of car owners who have done nothing more than added heavy air dams and ground effects, tons of stickers, neon lighting, and a coffee can to their cars. If a turbocharged engine is run without a muffler, will it have an identifiable exhaust note or will it sound like a ricer fart can?

It will be loud, but how it actually sounds will be dependant on your exhaust sytem setup.

And, many thanks in advance for the time you take to answer my questions.

[float_6969]

I would say your first step would be to read the EF & EC section of the FSM.

The BOV can go anywhere on the piping, but as close to the TB as possible is best.

I would consider a water to air intercooler. Due to packaging constraints, it will probably be your best bet.

[Brocephus]

EF & EC section of the FSM

Huh...wha?

Are air/water ICs usually smaller than air/air?

[skunkmonkey]

well this isn't CA specific... BUT it is a great source of information about basic understanding of motors and turbo chargers.

http://auto.howstuffworks.com/turbo.htm

[Brocephus]

well this isn't CA specific... BUT it is a great source of information about basic understanding of motors and turbo chargers.

http://auto.howstuffworks.com/turbo.htm

What's ironic is that as I was writing the OP, I thought it would be a good idea to look around before I ask any really stupid questions. How Stuff Works is usually the first place I go because they usually have accurate information and plenty of diagrams to go along with it.

So you are correct about it being a great source, but I already hit it while I was writing the OP, hehe. Thanks though!

[RM12577]

here is a link talking about someone putting liquid intercooling into a 240. this site has a lot of simplifying steps for a CA as well http://www.driftopia.com/2007/...elled/

[ca18detgabby]

I would say your first step would be to read the EF & EC section of the FSM.

The BOV can go anywhere on the piping, but as close to the TB as possible is best.

I would consider a water to air intercooler. Due to packaging constraints, it will probably be your best bet.

I though the BOV was ideally on closest to the turbo? not close to the TB?

[ca18detgabby]

Huh...wha?

Are air/water ICs usually smaller than air/air?

generally they are smaller lengths of piping, as far as the size of the core....... to achive similar results the water cooled is smaller....... however, this will require addition water source, heat exchangers, pump......

[float_6969]

Huh...wha?

Are air/water ICs usually smaller than air/air?

If you don't have a copy of the FSM (Factory Service Manual) for the S13 w/CA18DET you are missing out. It's in the FAQ, but I'll save you the trouble.

It's a large file, so I hope you don't have dial up. It's also zipped, so you'll have to unzip it.

http://www.nicoclub.com/FSM/misc/CA18DE.zip

[saf]

Interesting Q, and while i could go into a lot of detail on the cycle of function of a turbo 4, say the CA, you really cant at the same time. A pistol, will work in a specified function as you say, and its a one way street.

However in a engine, data is not only being read, its being analysed and altered, then sent back to other parts. While a MAF or AFM (not the same) can read a volume of air, and its density at the ecu, the ecu then sends a signal to the injector on its next opening, "so this, for this long". However, if Mr knock sensor chimes in, the cycle of function for that one command is now altered, and it needs to send new signals, to ign and fuel systems.

As fara s some of the other q's, yes a bov at the TB region is best. The reason a BOV is used, is for safety, not perf, and what happens is the TB closes with say 120,000rpm of shaft speed at your compressor, and you get a shockwave off the TB plate, back down the system. This is enough to blow apart IC lines, and even backspin the turbo (because the EGF - ex gas flow, has fallen to almost nothing aswell) at times snapping thinner shafts.

If you place the BOV at the TB (near to) it lets go of pressure at the point of the shockwake origin. We talk about a few extra psi, but in volume, its a lot. The difference between 8 and 12 psi is 4psi on paper, and not much in the realworld ... but in a motor, thats 4 pounds extra per square inch. Now measure the displacement from the tip of the comp blade, piping, FMIC, plenum, runners, head and to piston top .... its a lot more volume.

And this is the sole reason for upping boost, not pressure, volume. Pressure doesnt make a engine go hard, its the volume of air because your compressing it, hence the pressure. A T25 at 18psi can perhaps flow 270hp for eg in a engine. In that same engine a HKS T51R SPL at 15psi can say flow 680hp.

Exhaust notes, well loose a muffler and you will get turbo whistle. It wont sound like a N/A civic (thank god) but it will be loud. The larger your turbo (exhaust side), the more engine noise.

WTA IC's are superb when designed well, and setup right. My Celica GT4 is on its OEM WTA, and it pushed out around 320hp at the flywheel, with a better system its capable of more, however so is the weight factor, and potential for items to fail.

EGT probes are cool, but in all honesty you need one in every cylinder, in the runner at a 45deg angle with the tip in the sentre of the exhaust port facing the exhaust valve. AT that point only will you see a inconsistancy in each cyl to see if head hot spotting or intake runner distribution is a problem. And even then when we have run up big turbos, the engines come online so hard and fast, a K-type (common) still doesnt react fast enough. having a EGT probe in a common collector is common, and all its good for is to get a baseline temp, and if something goes slightly off, you see a spike (if your lucky) in EGT's. In order i rate gauges as boost, then fuel pressure, oil temp, egt and water temp.

Hope that answered a couple of q's.

[PapaBurgundy]

The CA sounds excellent without a muffler, I'm running a 3 inch turbo back side exit and it sounds beautiful! My personal opinion is that any 4 cylinder with a can sounds just about the same as any other 4 cylinder with a can, the only way for it to stand out is to be straight piped. Then again I live in wisconsin where everything is straight piped, unfortunatly that includes GM v6's.