This guide is meant to help people understand how each part of a turbocharger system functions and how it’s meant to function. DO NOT argue about anything in this thread, well feel free to add anything you might find helpful but don’t be an ********************* in this thread. Hopefully this thread brings a greater understanding to people who are curious about turbochargers and forced induction in general. I hope many questions are asked and that people will walk away from their computers with a greater understanding of forced induction.
There will be many updates to this thread as it goes on, different topics will be covered, etc.
Selecting the proper turbocharger.
When selecting the turbocharger that will suit your needs and the performance gains you want there is a lot to take into consideration. A turbocharger’s general purpose is to improve the efficiency of an engine. While increasing the efficiency power is also increased. A turbocharger compresses and forces air into engine cylinders which provides the environment for more fuel to be burned. The compressed air does not and I repeat DOES NOT make power, it’s the extra air allowing more fuel to be added and burned that gives you that throws you back in the seat.
Now, when selecting the proper turbocharger for your application you have to consider how much power you want and where you want it. A smaller framed turbo will spool quickly, giving a flat torque curve and broadening the powerband till mid to high RPM then there will be a gradual decline in power. This happens because the turbocharger is retaining heat caused by excessive backpressure and excessive RPM of the turbine shaft and is no longer within It’s efficiency range and basically blows hot air. The small size of the turbocharger exhaust housing can’t keep up with how much exhaust gas is being fed into it from the head and can’t get rid of it quickly enough because of it's small size and cast iron absorbs heat quickly with a slow dissipation rate.
A larger size turbocharger will take longer to spool up but will make power all the way to redline because it’s not working nearly as hard as the smaller turbo. The less work the turbocharger has to do the cooler it stays, with it’s large size it can easily get rid of the exhaust gasses entering the hot side which also aids in keeping the turbocharger cooler and the turbine encounters less resistance. The larger size of the compressor wheel pushes more LB/MIN of air than the smaller turbocharger at a lower RPM, this is the less amount of work I was talking about. Less RPM equals less heat.
Quote:
Originally Posted by astroboy View Post
One of the major causes of the heat that is produced is from the act of compressing the air via the compressor wheel (from the molecules being accelerated and forced into a small area ie. intercooler and associated pipes).
PLEASE DRILL THIS INTO YOUR HEADS: HOW MUCH POWER A TURBOCHARGER MAKES IS NOT SOLEY DERTIMINED BY IT’S SIZE. IT’S NOT HOW MANY CFM’S THE TURBOCHARGER CAN FLOW, IT’S ABOUT HOW MANY LB/MIN THE TURBO CAN FLOW. COLD AIR IS MORE DENSE THAN HOT AIR. THE MORE DENSE THE AIR IS THE MORE MOLECULES ARE PRESENT PER CUBIC FOOT. THE MORE MOLECULES THERE ARE PER CUBIC FOOT THE MORE POWER YOU WILL MAKE PER PSI. THE LESS HEAT AND BACKPRESSURE A TURBOCHARGER HAS TO HANDLE THE COOLER THE PRESSURIZED AIR STAYS, THE MORE POWER IS MADE.
Selecting a turbo manifold.
When choosing a turbo manifold the thing to keep in mind is quality and exactly what you plan on doing with the car. For most street applications a short runner cast iron manifold will work fine. The iron casting is strong and isn’t prone to cracking while the short runners improve spool time of the turbocharger. Cast manifolds are the perfect choice for a typical street car but tend to show their downside after 400-500 horsepower because backpressure and heat start to kill power. Tubular manifolds a great for high revving, high power cars with an upper RPM power band. The equal length design keeps air flow consistent and improves spool response with larger frame turbochargers. Backpressure is also decreased with longer, smoother runners, when mated with a properly sized down pipe. By lowering backpressure there is less air resistance and less heat absorption in the turbocharger with the benefits being more power and increased efficiency.
Selecting a wastegate.
A wastegate is a device used to vent excess exhaust gases out of the turbocharger system to maintain a specific level of boost pressure by maintaining the speed of the turbine in the exhaust housing of the turbocharger. Selecting a wastegate is a pretty easy affair as they all operate relatively the same and are manufactured in relative sizes from company to company.
Having too large of a wastegate within the turbo system can cause excessive turbo lag as too much of the needed exhaust gas is being vented out of the system. Having too small of a wastegate has the opposite effect and can’t successfully purge all the exhaust gases that it has to and you’ll encounter boost creep or boost spike which can potentially destroy your engine. Usually a 38mm - 44mm wastegate is the correct choice for a typical 400hp street car that has a midsize framed turbocharger. The choice is all up to you as to which you may want as it has as simple function and is usually noted as a “bling” accessory.
Side note, split scroll manifolds require two wastegates to properly vent exhaust gasses. If only one wastegate is used on one side of the split manifold collector only half of the exhaust is being vented. When using dual wastegates they tend to be a smaller diameter to avoid the lag problem mentioned above.
Selecting a blow off valve.
A blow off valve dissipates pressurized air in the intercooler piping when the throttle plate is closed quickly and efficiently to get rid of or at the least reduce harmful compressor surge (the impeller hits resistance caused by the pressurized air) that can reduce the life of the turbocharger.
A blow off valve is a simple device and all function similar across manufacturers. An Ebay knock off Tial blow off valve will function the same as a legit one. The difference is in the quality of the parts used in the assembly. They come in many different shapes, sizes, pretty colors and make different cool noises but at the end of the day it’s a simple vacuum actuated valve. So the choice is really up to the individual as to which one they want to use.
On a side note, cars with MAF sensors will spike a rich air/fuel ratio with atmospheric blow off valves and may either backfire or even stall. It’s smart to buy a reticulating blow off valve for these applications unless in one form or another the rich spike can be corrected.
Selecting an intercooler.
An intercooler in technical terms is a simple heat exchanger. As the forced air passes through the intercooler the incoming air is cooled and the aluminum of the intercooler absorbs the heat. There is more to selecting the right one than having the biggest one in the parking lot and it’s just advertising your investment to thieves.
Just the same as blow off valves intercoolers are a simple device that have been around for over a hundred years serving different purposes. There is negligible difference between an Ebay intercooler and a 700$ Trust intercooler. There may be slight differences in flow but it’s all about what you feel like paying (and you’re paying for a name).
There is usually a .5 to 1 PSI drop in any intercooler just because of the slight restriction the air. A smaller intercooler will heat soak quicker than a larger one (remember the aluminum of the intercooler absorbs the heat from the compressed air) and a larger intercooler will reach higher temperatures than a smaller one due to a larger surface area while taking longer too cool down than a smaller one.
Intercooler piping.
There isn’t much to intercooler piping other than different types of metals have different rates of heat absorption and dissipation. Aluminum is generally used because of it’s quick heat transfer rate. Also the longer the system of piping the more heat is absorbed which means increased intake temperatures which means less power (hot air is less dense than cold air, less molecules to be burned).
Quote:
Originally Posted by astroboy View Post
As far as I understand the less intercooler piping (and proper size) the better response because the turbo has less area to pressurize so short intercooler pipes that are only the size you need are beneficial. The downside to that is the throttle control is not as smooth due to the volume of air that is compressed. From what I have read on intercoolers they are not needed (but are adventageous) at about 7 psi and less. These systems would be able to be piped from turbo to intake manifold straight shot.
Exhaust systems.
From: Astroboy
So here's what I know about exhaust...the general rule is the golden one: the less backpressure the better. The best way to achieve this is to have no (or very little) exhaust after the turbo but it is also the best way to get pulled over and ticketed. The next best thing to do it to have a decent diamater exhaust (above 2" but in general over 3" is overkill unless it is a turbo 6L) with a high flow cat and a free flowing muffler.
The high flow cat's will net you about 1 less wheel hp which is negatable, you won't get any tickets, it will act as a resinator helping to keep the volume down and the tone sounding nice, and lastly will make sure you keep passing emissions and keep you from getting tickets. For a muffler it is personal preferance but the straight thru design net's the least amount of backpressure (good) but most amount of noise (bad). But there is a plus to having a turbine up stream of the muffler...it helps to reduce noise by about 1/3 except when the wastegate is open. I have read that magnaflow works best for quieting and low backpressure. You can go with a singal chamber muffler to cut noise down and take a slight performance hit.
When having an external wastegate the exhaust should be plumbed back into the exhaust system after the turbo at the lowest ange as possible (you could have a seperate exhaust system or vent to atmosphere but it is not that much more beneficial imo). The O2 sensor should be downstream of that to facilitate good mixture of exhaust gasses before the O2 sensor sees/reads it. When buying/building an exhaust system you want to use manderal bent pipes (smooth inner diamater vs crinkley crush bends) and low bend radius' to have the smoothest flow. I think of exhaust flow like water kinds where large bends would create edy's and crush bent pipes would create turbulance (kinda like rapids in a river). That's about it!
Quote:
Originally Posted by YatesTunes View Post
I would like to add that when determining the proper size for your exhaust system you want high velocity and low backpressue. If you have too small of an exhaust there will be too much backpressure and the exhaust turbine in the turbocharger will hit resistance and you will lose power. If you have too large of an exhaust velocity is reduced which causes exhaust bottle necking which is erratic changes in exhaust scavenging and volumetric efficiency. Think of it in terms of water, with little to no pressure barley pushes the water through the pipe it might just sit there and puddle. Add a little pressure behind it and the water travels with more force.
Selecting proper injectors.
Injectors are generally a universal item meaning they’re usable across a broad spectrum of makes and models. Certain styles fit certain manifolds, some respond better to different voltages than others. When selecting injectors for your car you want to leave yourself headroom incase you plan on upping the boost also if you install larger injectors than needed the injector rate can be easily regulated without concern and will run at a lower duty cycle which has it’s little benefits. 450cc or 42lb/hr injectors can roughly support 100hp per cylinder, more like 80hp in given circumstances such as age, wear, voltage and resistance. Injectors sized from around 800cc and up tend to have idle issues as they can’t open and close quickly enough and inject too much fuel, this can usually be somewhat corrected by tuning but the car might never idle stoich, usually on the rich side.
WARNING: DO NOT INSTALL LARGER INJECTORS IN YOUR CAR WITHOUT PROPER ENGINE MANAGEMENT. IF YOU DO YOU CAN POTENTIALLY DESTROY YOUR ENGINE.
Selecting an engine management system.
There are many different options to choose from when deciding what management system to use. The right choice is what is what works for you and how much you want to pay. If the person you planned on having your vehicle tuned by doesn’t know how to use a certain system go somewhere else, you shouldn’t have to cater to the person you’re hiring. Don’t listen to forum nonsense about this system sucks or that system’s garbage because it’s bullshit. Either that person has no experience with that system what so ever or they’re just not properly educated with it. Every option has it’s trade off with price and availability, features and options, simplicity and ease of installation, and user to user compatibility.
By far the easiest, cheapest, and simplest way to tune an OBD1 Honda is by chipping the stock ECU and running software such as CROME or ECTune. There's a tremendous amount of community support behind these two programs and if your "tuner" doesn't know how to tune these programs or says they are inferior trash ask for your deposit back and walk away. A Chip kit from www.xenocron.com is roughly 30$ and can be installed at your home with simple soldering tools in under an hour.
For now I’ll leave it at that and I’ll update this section later with somewhat of a “tuning tutorial”.
Crankcase ventilation and why it's so important.
Every engine that currently sits inside any given engine bay has a system devoted to removing blow-by gasses from the crankcase. Blow-by gasses are nothing more than a little bit of air and fuel that are forced through the tiny gaps in the piston rings from the immense pressure from combustion but that little amount of blow-by becomes a lot of blow-by when your engine is singing at 8,000RPM. If this issue is not taken care of the crankcase will continue to pressurize itself until various engine seals blow out or the pressure tries going back through the piston rings and eventually destroys them.
The typical factory system (including Honda) has a breather tube coming from the valve cover to the intake bellows before the intake manifold. The best way to keep pressure out of the crankcase is to keep it under vacuum. The vacuum of the engine draws the pressure from the crankcase and reintroduces it into the cylinder to be combusted which aids in lowering emissions.
When turbocharging a vehicle blow-by is increased about 40% give or take on a healthy engine. This pressure needs to be dispersed without being reintroduced into the combustion cycle because in effect blow-by gasses can lower the octane of the fuel being used and also increase intake temperatures by 10%. This is why everyone vents the crankcase to open atmosphere with the use of a catch can. How much ventilation is necessary is debatable. My philosophy is the more the better and some is better than none. I know many people who run something like six sources of ventilation and I know a bunch who just vent from the existing hole in the valve cover.
To sum everything up, make sure you properly vent the crankcase when going forced induction or you will ************ your shit up.
There will be many updates to this thread as it goes on, different topics will be covered, etc.
Selecting the proper turbocharger.
When selecting the turbocharger that will suit your needs and the performance gains you want there is a lot to take into consideration. A turbocharger’s general purpose is to improve the efficiency of an engine. While increasing the efficiency power is also increased. A turbocharger compresses and forces air into engine cylinders which provides the environment for more fuel to be burned. The compressed air does not and I repeat DOES NOT make power, it’s the extra air allowing more fuel to be added and burned that gives you that throws you back in the seat.
Now, when selecting the proper turbocharger for your application you have to consider how much power you want and where you want it. A smaller framed turbo will spool quickly, giving a flat torque curve and broadening the powerband till mid to high RPM then there will be a gradual decline in power. This happens because the turbocharger is retaining heat caused by excessive backpressure and excessive RPM of the turbine shaft and is no longer within It’s efficiency range and basically blows hot air. The small size of the turbocharger exhaust housing can’t keep up with how much exhaust gas is being fed into it from the head and can’t get rid of it quickly enough because of it's small size and cast iron absorbs heat quickly with a slow dissipation rate.
A larger size turbocharger will take longer to spool up but will make power all the way to redline because it’s not working nearly as hard as the smaller turbo. The less work the turbocharger has to do the cooler it stays, with it’s large size it can easily get rid of the exhaust gasses entering the hot side which also aids in keeping the turbocharger cooler and the turbine encounters less resistance. The larger size of the compressor wheel pushes more LB/MIN of air than the smaller turbocharger at a lower RPM, this is the less amount of work I was talking about. Less RPM equals less heat.
Quote:
Originally Posted by astroboy View Post
One of the major causes of the heat that is produced is from the act of compressing the air via the compressor wheel (from the molecules being accelerated and forced into a small area ie. intercooler and associated pipes).
PLEASE DRILL THIS INTO YOUR HEADS: HOW MUCH POWER A TURBOCHARGER MAKES IS NOT SOLEY DERTIMINED BY IT’S SIZE. IT’S NOT HOW MANY CFM’S THE TURBOCHARGER CAN FLOW, IT’S ABOUT HOW MANY LB/MIN THE TURBO CAN FLOW. COLD AIR IS MORE DENSE THAN HOT AIR. THE MORE DENSE THE AIR IS THE MORE MOLECULES ARE PRESENT PER CUBIC FOOT. THE MORE MOLECULES THERE ARE PER CUBIC FOOT THE MORE POWER YOU WILL MAKE PER PSI. THE LESS HEAT AND BACKPRESSURE A TURBOCHARGER HAS TO HANDLE THE COOLER THE PRESSURIZED AIR STAYS, THE MORE POWER IS MADE.
Selecting a turbo manifold.
When choosing a turbo manifold the thing to keep in mind is quality and exactly what you plan on doing with the car. For most street applications a short runner cast iron manifold will work fine. The iron casting is strong and isn’t prone to cracking while the short runners improve spool time of the turbocharger. Cast manifolds are the perfect choice for a typical street car but tend to show their downside after 400-500 horsepower because backpressure and heat start to kill power. Tubular manifolds a great for high revving, high power cars with an upper RPM power band. The equal length design keeps air flow consistent and improves spool response with larger frame turbochargers. Backpressure is also decreased with longer, smoother runners, when mated with a properly sized down pipe. By lowering backpressure there is less air resistance and less heat absorption in the turbocharger with the benefits being more power and increased efficiency.
Selecting a wastegate.
A wastegate is a device used to vent excess exhaust gases out of the turbocharger system to maintain a specific level of boost pressure by maintaining the speed of the turbine in the exhaust housing of the turbocharger. Selecting a wastegate is a pretty easy affair as they all operate relatively the same and are manufactured in relative sizes from company to company.
Having too large of a wastegate within the turbo system can cause excessive turbo lag as too much of the needed exhaust gas is being vented out of the system. Having too small of a wastegate has the opposite effect and can’t successfully purge all the exhaust gases that it has to and you’ll encounter boost creep or boost spike which can potentially destroy your engine. Usually a 38mm - 44mm wastegate is the correct choice for a typical 400hp street car that has a midsize framed turbocharger. The choice is all up to you as to which you may want as it has as simple function and is usually noted as a “bling” accessory.
Side note, split scroll manifolds require two wastegates to properly vent exhaust gasses. If only one wastegate is used on one side of the split manifold collector only half of the exhaust is being vented. When using dual wastegates they tend to be a smaller diameter to avoid the lag problem mentioned above.
Selecting a blow off valve.
A blow off valve dissipates pressurized air in the intercooler piping when the throttle plate is closed quickly and efficiently to get rid of or at the least reduce harmful compressor surge (the impeller hits resistance caused by the pressurized air) that can reduce the life of the turbocharger.
A blow off valve is a simple device and all function similar across manufacturers. An Ebay knock off Tial blow off valve will function the same as a legit one. The difference is in the quality of the parts used in the assembly. They come in many different shapes, sizes, pretty colors and make different cool noises but at the end of the day it’s a simple vacuum actuated valve. So the choice is really up to the individual as to which one they want to use.
On a side note, cars with MAF sensors will spike a rich air/fuel ratio with atmospheric blow off valves and may either backfire or even stall. It’s smart to buy a reticulating blow off valve for these applications unless in one form or another the rich spike can be corrected.
Selecting an intercooler.
An intercooler in technical terms is a simple heat exchanger. As the forced air passes through the intercooler the incoming air is cooled and the aluminum of the intercooler absorbs the heat. There is more to selecting the right one than having the biggest one in the parking lot and it’s just advertising your investment to thieves.
Just the same as blow off valves intercoolers are a simple device that have been around for over a hundred years serving different purposes. There is negligible difference between an Ebay intercooler and a 700$ Trust intercooler. There may be slight differences in flow but it’s all about what you feel like paying (and you’re paying for a name).
There is usually a .5 to 1 PSI drop in any intercooler just because of the slight restriction the air. A smaller intercooler will heat soak quicker than a larger one (remember the aluminum of the intercooler absorbs the heat from the compressed air) and a larger intercooler will reach higher temperatures than a smaller one due to a larger surface area while taking longer too cool down than a smaller one.
Intercooler piping.
There isn’t much to intercooler piping other than different types of metals have different rates of heat absorption and dissipation. Aluminum is generally used because of it’s quick heat transfer rate. Also the longer the system of piping the more heat is absorbed which means increased intake temperatures which means less power (hot air is less dense than cold air, less molecules to be burned).
Quote:
Originally Posted by astroboy View Post
As far as I understand the less intercooler piping (and proper size) the better response because the turbo has less area to pressurize so short intercooler pipes that are only the size you need are beneficial. The downside to that is the throttle control is not as smooth due to the volume of air that is compressed. From what I have read on intercoolers they are not needed (but are adventageous) at about 7 psi and less. These systems would be able to be piped from turbo to intake manifold straight shot.
Exhaust systems.
From: Astroboy
So here's what I know about exhaust...the general rule is the golden one: the less backpressure the better. The best way to achieve this is to have no (or very little) exhaust after the turbo but it is also the best way to get pulled over and ticketed. The next best thing to do it to have a decent diamater exhaust (above 2" but in general over 3" is overkill unless it is a turbo 6L) with a high flow cat and a free flowing muffler.
The high flow cat's will net you about 1 less wheel hp which is negatable, you won't get any tickets, it will act as a resinator helping to keep the volume down and the tone sounding nice, and lastly will make sure you keep passing emissions and keep you from getting tickets. For a muffler it is personal preferance but the straight thru design net's the least amount of backpressure (good) but most amount of noise (bad). But there is a plus to having a turbine up stream of the muffler...it helps to reduce noise by about 1/3 except when the wastegate is open. I have read that magnaflow works best for quieting and low backpressure. You can go with a singal chamber muffler to cut noise down and take a slight performance hit.
When having an external wastegate the exhaust should be plumbed back into the exhaust system after the turbo at the lowest ange as possible (you could have a seperate exhaust system or vent to atmosphere but it is not that much more beneficial imo). The O2 sensor should be downstream of that to facilitate good mixture of exhaust gasses before the O2 sensor sees/reads it. When buying/building an exhaust system you want to use manderal bent pipes (smooth inner diamater vs crinkley crush bends) and low bend radius' to have the smoothest flow. I think of exhaust flow like water kinds where large bends would create edy's and crush bent pipes would create turbulance (kinda like rapids in a river). That's about it!
Quote:
Originally Posted by YatesTunes View Post
I would like to add that when determining the proper size for your exhaust system you want high velocity and low backpressue. If you have too small of an exhaust there will be too much backpressure and the exhaust turbine in the turbocharger will hit resistance and you will lose power. If you have too large of an exhaust velocity is reduced which causes exhaust bottle necking which is erratic changes in exhaust scavenging and volumetric efficiency. Think of it in terms of water, with little to no pressure barley pushes the water through the pipe it might just sit there and puddle. Add a little pressure behind it and the water travels with more force.
Selecting proper injectors.
Injectors are generally a universal item meaning they’re usable across a broad spectrum of makes and models. Certain styles fit certain manifolds, some respond better to different voltages than others. When selecting injectors for your car you want to leave yourself headroom incase you plan on upping the boost also if you install larger injectors than needed the injector rate can be easily regulated without concern and will run at a lower duty cycle which has it’s little benefits. 450cc or 42lb/hr injectors can roughly support 100hp per cylinder, more like 80hp in given circumstances such as age, wear, voltage and resistance. Injectors sized from around 800cc and up tend to have idle issues as they can’t open and close quickly enough and inject too much fuel, this can usually be somewhat corrected by tuning but the car might never idle stoich, usually on the rich side.
WARNING: DO NOT INSTALL LARGER INJECTORS IN YOUR CAR WITHOUT PROPER ENGINE MANAGEMENT. IF YOU DO YOU CAN POTENTIALLY DESTROY YOUR ENGINE.
Selecting an engine management system.
There are many different options to choose from when deciding what management system to use. The right choice is what is what works for you and how much you want to pay. If the person you planned on having your vehicle tuned by doesn’t know how to use a certain system go somewhere else, you shouldn’t have to cater to the person you’re hiring. Don’t listen to forum nonsense about this system sucks or that system’s garbage because it’s bullshit. Either that person has no experience with that system what so ever or they’re just not properly educated with it. Every option has it’s trade off with price and availability, features and options, simplicity and ease of installation, and user to user compatibility.
By far the easiest, cheapest, and simplest way to tune an OBD1 Honda is by chipping the stock ECU and running software such as CROME or ECTune. There's a tremendous amount of community support behind these two programs and if your "tuner" doesn't know how to tune these programs or says they are inferior trash ask for your deposit back and walk away. A Chip kit from www.xenocron.com is roughly 30$ and can be installed at your home with simple soldering tools in under an hour.
For now I’ll leave it at that and I’ll update this section later with somewhat of a “tuning tutorial”.
Crankcase ventilation and why it's so important.
Every engine that currently sits inside any given engine bay has a system devoted to removing blow-by gasses from the crankcase. Blow-by gasses are nothing more than a little bit of air and fuel that are forced through the tiny gaps in the piston rings from the immense pressure from combustion but that little amount of blow-by becomes a lot of blow-by when your engine is singing at 8,000RPM. If this issue is not taken care of the crankcase will continue to pressurize itself until various engine seals blow out or the pressure tries going back through the piston rings and eventually destroys them.
The typical factory system (including Honda) has a breather tube coming from the valve cover to the intake bellows before the intake manifold. The best way to keep pressure out of the crankcase is to keep it under vacuum. The vacuum of the engine draws the pressure from the crankcase and reintroduces it into the cylinder to be combusted which aids in lowering emissions.
When turbocharging a vehicle blow-by is increased about 40% give or take on a healthy engine. This pressure needs to be dispersed without being reintroduced into the combustion cycle because in effect blow-by gasses can lower the octane of the fuel being used and also increase intake temperatures by 10%. This is why everyone vents the crankcase to open atmosphere with the use of a catch can. How much ventilation is necessary is debatable. My philosophy is the more the better and some is better than none. I know many people who run something like six sources of ventilation and I know a bunch who just vent from the existing hole in the valve cover.
To sum everything up, make sure you properly vent the crankcase when going forced induction or you will ************ your shit up.
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