Boosted2k2

iTrader: (3)

The Big Bad Turbo FAQ

A lot of credit for this FAQ goes to the “DIY King” Grey. I wrote this and sent it to him and he edited it for me. I PM’d him a million times and he came through 110%. A lot of the information comes from general knowledge, questions I’ve asked myself, and random information from around the internet. If you see any errors or think there should be any additions, PM me and let me know. I will continue to add and edit this, so keep and eye out.

What is this turbocharger junk all about?

Turbocharging is just another type of forced induction. That is, forcing more air into the engine, allowing more air for fuel to mix with for greater combustion. The same applies to superchargers and spraying nitrous oxide. They all just do it by different methods. Nitrous oxide has a higher percentage of oxygen than air, so basically you are spraying more oxygen into the engine than the normal intake would take in. A turbocharger or a supercharger adds air under pressure which increases the amount of oxygen per volume amount. Just to throw some science around: PV=nRT if volume (V) and temperature(T) are constant, than an increase in pressure(P) leads to an increase in amount of oxygen (n). That also goes to show you how temperature can add or reduce performance.

On another note: Frequently you see people designate the boost setting in lbs., psi, and Bar. This is the pressure above the standard atmospheric pressure of 14.7psi (sealevel). For conversion purposes:
1 Bar (barometric pressure) = 14.5psi
1 lb = 1 psi (lb/inch2)

So, if some one says they’re running 0.8bar:
0.8bar*14.5 = 11.6psi.

How does a turbocharger work?

Due to combustion, we get exhaust gases. These exhaust gases flow out of the combustion chambers into the exhaust manifold. The turbocharger has two sides, a turbine housing (also known as the hot end) and a compressor housing (also known as the cool end). The turbine is placed in the direct flow of the exhaust gases which causes it to spin. This in turn spins the compressor which sucks in air (like an intake) and sends it toward the engine creating a certain pressure commonly measured in Bars or PSI. This is a simplistic explanation however. There are other optional mechanisms that can take part. They are provided later on in this FAQ.

What are the most basic parts I will need?

The most basic parts to a turbo set-up are:
1. Turbocharger
2. Turbo Exhaust Manifold
3. 2 Oil lines: from oil source (by the pressure sender), and one from the turbo to the oil pan
4. Charge pipes (to bring air from the turbocharger to the intake manifold)
5. Wastegate (to prevent too much boost)
6. Blow off valve (to relieve boost buildup in the charge pipe when the throttle body disc is closed)
7. Modification to the fuel system (dependent on use, explained later on)

How do I choose a turbocharger?

You are better off talking to a professional on choosing a turbocharger because it is pretty dependent on what you are trying to achieve, how you plan to use the vehicle, and the specifications of the engine. Because we are interested in a small displacement engine ~100CID (1668cc), we would want to choose a smaller sized turbo. We want a smaller size because we only have a small amount of exhaust gas to spin the turbine. The smaller the turbine = lighter turbine wheel = less flow to make it spin faster. A T3, T25, or T3/T04 hybrid are three good choices in my opinion. There are other sizes as well. The T28 is placed size-wise between the T25 and T3. And larger than the T3 is the T4. The T25 is good but can get hot really fast and is usually only able to handle up to 14psi. The T3 and T3/04 hybrid are good because they can handle the low displacement, and a higher boost setting should you want to upgrade your setup sometime. T3 and T3/04 hybrids are among the most common turbochargers used. When talking about hybrids, it means that it has different parts put together from different families of turbos. A T3/T04 uses a T3 hot end and a T4 compressor. There are other hybrids such as the T25/28 and the T25/T3. The limits are really endless to build a hybrid. Another thing that has to be looked at is the A/R ratio. A smaller number generally is better for low end power, and a higher number is better for high end. For a mostly street and occasional race application I would suggest somewhere around a .48. For more high-end power, maybe a .63.

Some turbochargers have a water-cooling option. This prevents the oil from “coking” and the turbo from overheating. Plus, you don’t have to change the oil as often (~2000 miles regular, ~3000 miles with a water-cooled turbocharger).

Some turbochargers are Variable Nozzle Turbos (VNT). This is an awesome idea whoever came up with the idea. Just to put it simply, there are blades on the inside of the turbine housing. When the turbo starts spooling they are closed which decreases the volume of the housing and allows the turbo to spool faster. When it has spooled and the turbine gets fast enough, the blades open up, increasing volume, and allowing more flow for more power.

Another thing helpful in choosing a turbocharger, is using compressor maps. These are readily available from such manufacturers as Turbonetics Inc. This works like this:

You need to calculate your engine’s airflow at your target boost setting:
Airflow (lb/min) = .2219 (RPM/HP)(1+Bar)

RPM = operating engine RPM This is where you want the power laid down
HP= Naturally aspirated HP
1+Bar = The amount of boost (in bar) you plan on running + 1.

Plot Airflow on the x-axis (bottom for you special people) and 1+Bar on the y-axis (left side). Hopefully the lines intersect in the 60-70% efficiency region. If not, it probably isn’t the right turbocharger for you, so move on to a different one.

What is a wastegate? Internal or external?

A wastegate allows excess exhaust gasses to bypass the turbochargers turbines so boost doesn’t “creep”. It allows the compressor to maintain a stable boost. Without the wastegate, the turbine could spin faster and faster with more exhaust gas flow, creating too much boost. Basically, when a certain pressure is reached, the wastegate vents off the excess pressure that builds up. The wastegate is also what is used together with a boost controller to limit boost.

On our engines, we don’t need an external wastegate. They are mostly used for engines in excess of 350-400hp. An internal one would do us just fine. However, an external will still work, it’s just not necessary. I personally like the look of an external one. If you are going to get an external one, a small size such as TiAL’s 35mm would be just fine.

Sometimes an internal wastegate will work better than an external type. The issue is kind of complex. For example, if you position an external wastegate on the turbo manifold such that it’s closer to one of the exhaust ports than it is to the others, then it will flow badly. It’s all about flow. If you put the exhaust gas vent from the wastegate right after the turbine (on the downpipe), then it’s bad for the turbo since it creates turbulence and it will increase turbo spool up time after wastegate activation. An internal wastegate can actually be better than an external model if done properly. You would want the inlet to the wastegate to be symmetrical as the turbo inlet so that when the wastegate opens the exhaust gases can find the path through the wastegate easily. Then you want the exhaust gases going out of the wastegate to be placed as far away from the turbine exhaust (main exhaust) as possible. Sometimes a separate exhaust pipe for the wastegate is used.

What is a BOV?

BOV stands for blow off valve. When the throttle plate closes the engine still supplies a few extra pulses of exhaust gas to the turbo and the turbo still spins because of that and the inertial force of the turbine and compressor. This causes the turbo to compress the air in the charge pipes, but since the throttle plate is closed, this air has nowhere to go. The BOV opens up at a set pressure to ventilate this air to the atmosphere. The ventilated air can be routed back into the intake (before the turbo) to pre-spool the turbo after the throttle plate is closed and opened up again. This gives you a slight performance boost when shifting and letting off the gas between shifts.

Why do I need a different exhaust manifold?

Because a regular manifold doesn’t provide the correct flow that is needed to spin the turbine. More importantly, you can’t generally just fit a turbocharger on a regular manifold. A turbo manifold is about half the length of a regular manifold and it ends with a flange made to fit a turbo. Also, equal length exhaust pipes on the turbo manifold and smooth mandrel bends make for good flow so that you don’t get any hot spots and lose heat inside the turbo header. You want to exhaust as much of the heat from inside of the combustion chamber as you can to drive the turbo. You can also wrap the turbo manifold with header wrap to keep the heat within it. Then there are issues such as keeping the surface area of the turbo manifold as small as possible to preserve the heat within it until it reaches the turbo; the thickness of the pipes is also important. The thinner the gauge, the less heat it soaks up and therefore the less heat it looses. Then there are certain issues with turbo manifold materials; stainless steel holds heat better than plain old steel for example. Ceramic coating a steel manifold is a good cheap option though. Then there are separate issues with heat damaging the turbo manifold material itself, so you have to compromise between manifold integrity and heat retention. Bleh.

But I drive an LX/DX not an EX!?

It doesn’t matter. A D17 is a D17. They all share the same manifold bolt pattern. The only difference is that you need to relocate a catalytic converter after the down pipe for the LX/DX/HX. Basically, convert your car to an EX exhaust system.

What about the returnless fuel system?

The fuel pressure regulator and fuel pump are combined to a single unit located in the fuel tank. This means that they aren’t easily upgraded. Let me explain a returnable system first. A returnable fuel system pumps out a certain pressure. The fuel is brought to the fuel rail and the injectors allow what volume and pressure is needed based on the signal from the MAF or MAP sensor. The unused fuel is sent back to the tank through a return line. So, the extra fuel makes it to the rail and is readily available for the taking. A returnless fuel system pumps a constant pressure and is adjusted by the fuel pressure regulator only to allow what is needed. So a small amount of fuel reaches the fuel rail and it all gets used. In order to get the fuel needed to maintain a proper air-fuel mixture, there are a few things we could do. We could convert the system to a returnable fuel system which is expensive and time consuming. It will require a stand-alone fuel management system too. The most common and economical way of taking care of the fuel is to get a “piggyback” fuel manager like the GReddy E-manage, Haltech F5, Motec, etc. to intercept the signals from the various sensors and up the fuel delivery, and add the control of extra injectors if need be. The fuel injectors atomize the fuel and that optimum atomization is variable and depends mainly on the fuel pressure entering the injector and the time for which the injector opens. The ECU varies the fuel pressure and the injector pulse width (time for which it opens) based on the MAP sensor. Better atomization means a more complete burn of the fuel for more power and fuel economy and reduced emissions.

Why do I have to upgrade my injectors

If you are adding more air into the engine, you need to compensate that with enough fuel so you aren't running lean. I don't know what the stock fuel system can handle, but when you are using a fuel controller, you are basically changing the duty cycle of your injectors. To get more fuel into the engine, you make the injectors work harder. It puts more wear on the injectors. Plus, the stock injectors might have to work above 90% duty, in which case they will just burn out. Getting larger injectors or adding extra injectors takes the stress off of the system. Injectors like 440cc, 550 cc, 650cc, 720cc... have the ability to flow more fuel at a lower cycle.

What’s a good boost setting for my vehicle?

For an EX, most commonly people have been running 5-8 psi. The LX and DX have a lower compression so they might be able to handle a little higher. At 10psi our head gaskets blow out. Therefore head studs and a better head gasket might allow you to run even higher boost on stock internals with a good intercooler.

What about a boost controller?

There are different types of boost controllers. Electronic boost controllers control the actuator on the wastegate by a solenoid. There are also manual boost controllers. These work by turning a screw that allows a certain amount of pressure to the wastegate. The wastegate activates based on how much boost pressure the turbo is producing. There’s usually a little tube running from right after the compressor housing to the wastegate. There’s a spring in the wastegate which holds the wastegate valve closed until a certain pressure. The manual boost controllers are placed in between the turbo and the wastegate and the wastegate spring is made as small as possible to allow the boost controller the largest possible adjustment of boost. Boost creep is a condition where the wastegate valve cracks open before the onset of full boost. This bleeds off exhaust gases that the turbo could use to spool up, so it takes a longer time for the turbo to spool up. This boost creep can be controlled with a pressure regulator valve and a pressure relief valve. The downside to a manual boost controller is that you have to get out of the car, open the hood, and turn the **** if you want to adjust the boost. An electronic controller allows you to do this in the car and most offer a fine adjust ****. All in all, I think it depends on laziness. I’m lazy… I’ll take an electronic one. Thanks.

What if I want to go further? What do I need?

By going further, I mean building up your turbo setup. Obviously you want to get the best flow possible. A good “cat-back” exhaust (2.25-3”) is a good idea if you don’t have one already. An intercooler would be a good idea. Gauges are especially good for monitoring your setup. A turbo timer is good if you are lazy like me, or generally in a hurry. An aftermarket clutch like ACT is good. Some internals will help you support higher boost settings without killing your engine.

What kinds of gauges?

An air/fuel gauge is good to keep an eye on your fuel system and make sure it is delivering the correct amount of fuel for the air that is inducted. An oil temperature gauge is important so you know that you aren’t running your turbo or engine too hot. A boost gauge is almost a necessity so you know how much boost you are actually running and making sure it corresponds with what the boost controller says. You could also go with a pyrometer (EGT gauge) to monitor the exhaust temperature. This usually helps you monitor if there is something wrong with air/fuel mixture.

What about a turbo timer?

It just allows you to take the key out of the ignition and let your car idle for an allotted amount of time. It does it so the turbo gets a chance to circulate oil as it cools down so it doesn’t have an instant “shock” from hot to cold, which lowers the life of the turbocharger. I would recommend one. They are relatively cheap ($100). The GReddy Full Auto Turbo Timer is good. It offers a speedometer, voltage meter, lap timer, and more. It also recommends a countdown based on how much you have driven, voltage, etc. It also has a safety feature so that if it is in countdown and the engine RPM’s go up, the engine will shut off.

What about an intercooler?

An intercooler isn’t always necessary, but highly recommended. It adds power by cooling the air and prevents detonation. It cools down the hot air from the turbo in the intercooler, and sends it to the charge pipes. This allows you to run a higher boost setting because the charge is cooler and gives a less chance of detonation. It works exactly how a radiator works: convection. There are air-air and air-water intercoolers. On our cars, air to air intercooler piping is hard to route due to space, but it still can be done. Air to air intercoolers work by passing cool outside air through the intercooler, while the hot gasses are inside. The air cools the metal which in turns cools the charge. An air to water intercooler uses a “water jacket” to store the liquid. The air passes through the jacket cooling the liquid which cools the aluminum which cools the charge. It will require a separate pump to flow the water through. Water can stand, but there would be little or no benefit.
FYI: TMIC stands for Top Mount Intercooler and FMIC stands for Front Mount Intercooler.


Do I really need an aftermarket clutch?

Under a higher boost setting, more pressure is put on your transmission to deliver more power than it was originally manufactured for. This causes it to heat up and wear out fast. Also, the stock clutch simply won’t lock together past a certain torque setting. It’ll just spin and you won’t be able to accelerate. Basically, your torque output will be limited by your clutch’s torque holding capacity. You’ll want to estimate how much power you’ll produce with your turbo and buy a clutch that can hold at least that much power. ACT offers a clutch kit for the D17 engines. You probably want to stick with a street application for drivability purposes. As far as I know, the Xtreme is the best for this application. The part number is HC5-XTOO. OO means you are using your factory flywheel. You could also swap that out if you want.


What kind of internals will allow me to run X lbs of boost?

It depends how high you want to go. You could lower your compression with different pistons. Arias offers custom fabrication. Some companies have them for out cars. You can upgrade your intake manifold to handle more pressure. You could get a block guard made for turbo applications. KMS offers the manifold and block guard for the D17. You could change the connecting rods. Valve springs, valves, head gasket… The possibilities are endless. But before you say that you want to run this incredibly high boost setting, you have to make sure you have a fuel system that is going to support it.

Compression Ratios: Higher, Lower... What's the difference?

C/O Catalyst
The trade off for 9:1 (higher) vs 8.5:1 (lower) are as follows:
-8.5:1 More Boost, less umpf before boost
-9.0:1 Little less boost, more umpf before boost, more power/PSI gained

All around, the best for our cars depends on the level that you know how to tune your car. If you cant tune worth a crap and want to make more power, go with the 8.5:1 pistons.
-If you know how to tune your car, use the 9.0:1
-The 9.0 will be better around town because you dont lose all of your bottom end, and you still have a good top end without having to run 20 psi.
-The 8.5:1 will let you run more boost for the octane gas you have, but as i said before, you sacrifice the bottom end power.
-With the 9.0:1, your car will be slower than stock before you make boost... BUT the 8.5:1 will be even worse before boost. So when you choose to buy pistons, just take the following into consideration:
-Driving habits (are you putting around town or Racing?)
-Tuning abilities
-Amount of boost you want to run
-The Octane of your fuel

I have a turbo setup… now what?

HAVE FUN!

BoYrAcEr

thanks for the info

MadWheel

iTrader: (11)

nice post.

Drgkainz2

very nice i am glad someone took the time to understand how it all works

Derek-CEO

iTrader: (27)

added this to the FAQ section

Connie

iTrader: (3)

wondering if you could try and find some dyno's or if you came accross any that would support how much HP is actually gained from a Turbo....

Drgkainz2

that all depends on the size of the turbo, and the CFM of it, how much boost. a lot of determinging factors its not just a flat out number

iamboo

iTrader: (4)

there are several variables that determine how much you gain with the amount of boost you apply.... i could tell you that t3 turbo kits are good up to 300 hp but that doesn't necessarily mean that you'll be making that much power....

Boosted2k2

iTrader: (3)

Like iamboo said, there are a lot of factors involved. The general rule is that the average most cars (including ours) get from boost is 10whp/psi. That is considered a good number.

trashguy

The average HP gain you get from a turbo is about a %50 increase.

iamboo

iTrader: (4)

well... typically on our civics with a basic turbo kit this is tru... if you put turbo on some other cars, usually its significantly less and also significantly less.... depends on the engine that you're turbo charging...

enzymes

1 bar doesnt equal 14.7psi. 1 bar equals 100 kPa (kilo pascals). 14.7psi is equal to 101.3 kPa. Just so you know.

Boosted2k2

iTrader: (3)

It's an estimation... you know that's not even a difference of 0.2 PSI right? Give me a break.

iamboo

iTrader: (4)

that's true... 14.5 psi = 1 bar = 100 kPa = 750.1 mmHg

enzymes

So why didn't you say atmospheric pressure is 15psi since tenths don't matter.

Also, when you said:

"So, if some one says they’re running 0.8bar:
0.8bar*14.7 = 11.76psi."

Why did you feel the need for hundredths? That's not even proper significant figures.

Boosted2k2

iTrader: (3)

I'm gonna be a man here and agree with you. I was getting defensive before because I was pissed off at other things. The more I thought about it, the more I questioned why I wouldn't agree with you. I changed it though. Thanks for the correction, as I asked in the FAQ for any corrections. Didn't mean to be a bitch

tekgnosis

Another FAQ might be "Do I need to upgrade my injectors"?

I want to run about 4/5lbs of boost MAX, and I can't see why I would need a whole lot more fuel.

Another question: What are ALL the parts that would be NEEDED to run a simple 1/3bar (roughly) turbo?
(Piping, turbo, everyone loves intercoolers, BOV, manifold, anything else?)

Boosted2k2

iTrader: (3)

I'll add the injector thing to the FAQ, but the parts you need for the most basic turbo setup is already listed in the FAQ.

tekgnosis

Thanks

I saw the basic stuff needed, but is the fuel system absolutely needed?

I'm just trying to macguyver something together, that's all.

Great FAQ, btw!

Boosted2k2

iTrader: (3)

You won't be able to get by without something done to the fuel system. I don't think that our MAP sensor can handle much boost, and I think our ECU runs on it's own set of fuel maps. That's why a fuel controller overrides that part of the ECU by accepting the signal before the ECU.

Example: The GReddy E-manage changes the voltage output of the MAP sensor and "hides" it from the ECU. Then I think what happens is that the voltage through the injector wires goes out as normal from the ECU, gets accepted by the E-manage which boosts the voltage and duty according to the fuel map you tuned and delivers the correct amount of fuel.

We wouldn't have to do a lot to the fuel system if it were a return system: for low boost, maybe injectors might alone do it. That's how GReddy kits are setup, with 4 550cc injectors to handle the fuel. But our systems are different than previous generation Civics.

SF has his own fuel setup that's different from all of this, but I have no idea how it really works. To hide boost from the MAP sensor, he uses a "bleeder" valve I think. It only lets a certain amount of air reach the sensor. As far as delivering fuel, I don't really know how that thing works. I think that when it sees the pressure from boost, it boosts the fuel pressure to a certain scale. (Example: not real numbers for every PSI of pressure, it would boost the fuel pressure up 6PSI.) But don't quote me, because I don't understand his.

Bottom line, I don't think that you can just through a turbo on, run 1/3BAR, and not have to do anything to the fuel system. The ECU probably wouldn't even recognize anything after a certain amount and you could just end up blowing up the engine by running too lean.

tekgnosis

that's what i was afraid of

It makes sense...I just wish I could get away with not having to screw around with it, or get away with not having to buy a whole kit.

if I'm going to buy a kit, I'd want to rebuild internals so that I could get a decent amount of boost out of it...but doing all that takes way too much cash. I can't justify it

I might as well save for an engine swap instead, or a new car for that matter


Thanks again for the info, Smokie2k2LX!