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Written By:
Jamie Harvey
Its about time we lay out our plan of attack on the performance part of this
project. As we mentioned already, we are going with a custom made turbo kit
as our power adder of choice. We already know that we want to achieve 300hp
on this engine with only 8psi of boost so the next step is finding a turbo that is
well suited for our application. As luck would have it, I was fortunate enough to
acquire a perfect turbo for the project car for FREE! It sure is nice having
performance oriented friends around to scavenge parts from. The turbo is a
dual ball bearing Garrett GT28R which came off of a Nissan S15 Silvia engine
my friend had shipped over from Japan. He planned on upgrading the turbo
anyhow so he threw me a bone to get the project moving in the right direction.
The Garrett GT series ball bearing GT28R, that came standard on the
Japanese version of the Nissan 240SX ( known as the Silvia in Japan) which
came equipped with the SR20DET turbo engine, is everything you'd want for a
project like this. It is very efficient and spools quickly reaching full boost as early
as 2500 rpm (thanks to the dual ball bearing design), conservatively rated at
producing nearly 280-300hp (many Silvia owners have achieved over
270-280hp to the WHEELS with this turbo) and its perfectly suited for a small
displacement engine like the 420A power plant. The center housing is both oil
and water cooled which should help keep the heat from getting excessive
during those hard highway pulls. It utilizes a T25/T28 turbo mounting flange
which isn't as common as the popular T3 flange but finding any necessary
parts for this turbo are a piece of cake, especially with the growing popularity of
the drifting circuit and 240SX project cars.
An intercooler will be used to bring down the air temperatures which rise as
the air is compressed and also as it passes through the turbos compressor
housing (which absorbs heat from the exhaust system passing through the
turbine housing). If we were only going to run a small amount of boost (3-5psi)
there wouldn't be a real need for an intercooler since the added heat isn't high
enough to rob too much performance or cause detonation to become a large
factor. Since we plan on achieving the most horsepower we can out of this
setup with a maximum of 8psi of boost we will need an intercooler.
A lot of people will run a HUGE front mounted intercooler (F.M.I.C.) which does
look cool but most are simply over sized for this application. Too large of an
intercooler, as well as too large of a diameter intercooler piping can create a
great deal of air volume which the turbo may have trouble pressurizing, not to
mention a loss of boost pressure through the intercooler. If the turbo is
pumping out 8psi at the turbo's outlet and you only get 5-6psi at the intake
manifold due to a pressure drop through the intercooler, you would have to
increase the boost pressure at the turbo to compensate. This will make the
turbo have to work harder and cause more heat. That kind of defeats the
purpose of the intercoolers function huh?
We decided to go with a factory 2G turbo model side mounted intercooler
(S.M.I.C.) which will reside outside of the engine compartment behind the front
bumper on the drivers side. The factory 2G turbo SMIC can handle cooling our
air intake charge up to our 300hp goal but thats about the point where it starts
to lose efficiency. For intercooler piping we opted for a universal 2.25" piping kit
which comes with all of the rubber couplers and clamps. You also could use 2"
piping but we are planning on going a bit higher in the horsepower range later
on so the additional volume might minimize some restrictions. To help relieve
the pressure building up in the intercooler piping once the throttle plate is
slammed shut will be a factory air-bypass valve (also known as a blow-ff valve,
BOV for short) from a 1st generation turbo eclipse/talon. These are one of the
most widely used BOV's for custom turbo kits because they are very affordable
when purchased used and can hold up to roughly 19psi of pressure and can
be modified very simply to hold even higher boost pressures without fail.
The factory exhaust system can be utilized but it will cause a restriction in
airflow as we approach our 300hp mark. At the very least, a custom 2.5" or 3"
downpipe alone would reduce some of the back pressure which will help that
turbo spool up faster. For the first stages we will construct a very simple
adapter which uses a majority of the factory downpipe and exhaust system. We
really can't add a free flowing larger diameter exhaust system without it being a
little noticeable while driving behind the car. Don't worry, we have an idea to fix
that when the time comes.
The MAP sensor reads the atmospheric pressure in the intake manifold as it
enters the engine. It takes this information, along with other sensors, to
determine the proper air/fuel mixture at any given point. Once the MAP sensor
sees the air pressure inside the intake manifold become greater than 14.7
PSIa also known as one atmosphere (0 psi of boost pressure or higher) it
triggers a an engine safety feature called 'fuel cut'. The engine control unit
(ECU) starts reducing the amount of fuel being sent into the engine because
the factory fuel system cannot support the additional fuel required.
Thankfully for us our project car is a '95 model year which does not need any
type of MAP sensor bypass, because the ECU didn't come with the 'fuel cut'
feature. The factory MAP sensor can handle the additional boost pressures we
will be subjecting it to right now but as we advance beyond the 8 psi mark it
wouldn't be able to handle it reliably for a long period of time. If you have a
'96-'99 model you will need to use either an electrical device called a 'fuel cut
defender' (FCD) or an air bypass adapter. The FCD simply wires into the MAP
sensors wiring harness and doesn't allow the sensor to send its maximum
voltage to the ECU, never telling the ECU that it has exceeded 0 psi of pressure.
The air bypass adapter is simply a check valve which you place between the
intake manifold and the sensor (the most common brand used is called the
MISSING LINK). When the air pressure exceeds 0 psi, the check valve opens
and diverts the air pressure from reaching the sensor. Either of these choices
has their ups and down but they generally get the job done rather inexpensively.
Proper monitoring of the system is a must so we will be adding a boost gauge,
EGT gauge (exhaust gas temperature) and a narrowband Air/fuel ration meter.
The reason we started with these 3 particular items is it is generally what every
do-it-yourself person seems to start out with. As we build on the system we will
document where these gauges are useful and what they should (and shouldn't)
be used for. A wideband oxygen sensor and logging software system will be
replacing just about all other gauges we will have shortly afterward.
Get your notepads and calculators ready because our next article will be all
about the MOST important part of adding a turbo kit and its NOT the turbo. It's
the fuel system, period. There are several methods used for improving the fuel
needs when adding a turbo kit and in the next segment we will show you some
options you have along with the advantages and disadvantages to each
system. If you want to turbo your car, upgrade the fuel system FIRST before you
even bother purchasing any other piece for your kit. The more you focus on the
fuel system, the better your chances are of having a reliable and powerful
setup. About 90% of the blown engines that occur after adding a turbo kit or
even a nitrous kit are due to improper fuel systems which were not up to par.
'Til next time!
Jamie Harvey
Its about time we lay out our plan of attack on the performance part of this
project. As we mentioned already, we are going with a custom made turbo kit
as our power adder of choice. We already know that we want to achieve 300hp
on this engine with only 8psi of boost so the next step is finding a turbo that is
well suited for our application. As luck would have it, I was fortunate enough to
acquire a perfect turbo for the project car for FREE! It sure is nice having
performance oriented friends around to scavenge parts from. The turbo is a
dual ball bearing Garrett GT28R which came off of a Nissan S15 Silvia engine
my friend had shipped over from Japan. He planned on upgrading the turbo
anyhow so he threw me a bone to get the project moving in the right direction.
The Garrett GT series ball bearing GT28R, that came standard on the
Japanese version of the Nissan 240SX ( known as the Silvia in Japan) which
came equipped with the SR20DET turbo engine, is everything you'd want for a
project like this. It is very efficient and spools quickly reaching full boost as early
as 2500 rpm (thanks to the dual ball bearing design), conservatively rated at
producing nearly 280-300hp (many Silvia owners have achieved over
270-280hp to the WHEELS with this turbo) and its perfectly suited for a small
displacement engine like the 420A power plant. The center housing is both oil
and water cooled which should help keep the heat from getting excessive
during those hard highway pulls. It utilizes a T25/T28 turbo mounting flange
which isn't as common as the popular T3 flange but finding any necessary
parts for this turbo are a piece of cake, especially with the growing popularity of
the drifting circuit and 240SX project cars.
An intercooler will be used to bring down the air temperatures which rise as
the air is compressed and also as it passes through the turbos compressor
housing (which absorbs heat from the exhaust system passing through the
turbine housing). If we were only going to run a small amount of boost (3-5psi)
there wouldn't be a real need for an intercooler since the added heat isn't high
enough to rob too much performance or cause detonation to become a large
factor. Since we plan on achieving the most horsepower we can out of this
setup with a maximum of 8psi of boost we will need an intercooler.
A lot of people will run a HUGE front mounted intercooler (F.M.I.C.) which does
look cool but most are simply over sized for this application. Too large of an
intercooler, as well as too large of a diameter intercooler piping can create a
great deal of air volume which the turbo may have trouble pressurizing, not to
mention a loss of boost pressure through the intercooler. If the turbo is
pumping out 8psi at the turbo's outlet and you only get 5-6psi at the intake
manifold due to a pressure drop through the intercooler, you would have to
increase the boost pressure at the turbo to compensate. This will make the
turbo have to work harder and cause more heat. That kind of defeats the
purpose of the intercoolers function huh?
We decided to go with a factory 2G turbo model side mounted intercooler
(S.M.I.C.) which will reside outside of the engine compartment behind the front
bumper on the drivers side. The factory 2G turbo SMIC can handle cooling our
air intake charge up to our 300hp goal but thats about the point where it starts
to lose efficiency. For intercooler piping we opted for a universal 2.25" piping kit
which comes with all of the rubber couplers and clamps. You also could use 2"
piping but we are planning on going a bit higher in the horsepower range later
on so the additional volume might minimize some restrictions. To help relieve
the pressure building up in the intercooler piping once the throttle plate is
slammed shut will be a factory air-bypass valve (also known as a blow-ff valve,
BOV for short) from a 1st generation turbo eclipse/talon. These are one of the
most widely used BOV's for custom turbo kits because they are very affordable
when purchased used and can hold up to roughly 19psi of pressure and can
be modified very simply to hold even higher boost pressures without fail.
The factory exhaust system can be utilized but it will cause a restriction in
airflow as we approach our 300hp mark. At the very least, a custom 2.5" or 3"
downpipe alone would reduce some of the back pressure which will help that
turbo spool up faster. For the first stages we will construct a very simple
adapter which uses a majority of the factory downpipe and exhaust system. We
really can't add a free flowing larger diameter exhaust system without it being a
little noticeable while driving behind the car. Don't worry, we have an idea to fix
that when the time comes.
The MAP sensor reads the atmospheric pressure in the intake manifold as it
enters the engine. It takes this information, along with other sensors, to
determine the proper air/fuel mixture at any given point. Once the MAP sensor
sees the air pressure inside the intake manifold become greater than 14.7
PSIa also known as one atmosphere (0 psi of boost pressure or higher) it
triggers a an engine safety feature called 'fuel cut'. The engine control unit
(ECU) starts reducing the amount of fuel being sent into the engine because
the factory fuel system cannot support the additional fuel required.
Thankfully for us our project car is a '95 model year which does not need any
type of MAP sensor bypass, because the ECU didn't come with the 'fuel cut'
feature. The factory MAP sensor can handle the additional boost pressures we
will be subjecting it to right now but as we advance beyond the 8 psi mark it
wouldn't be able to handle it reliably for a long period of time. If you have a
'96-'99 model you will need to use either an electrical device called a 'fuel cut
defender' (FCD) or an air bypass adapter. The FCD simply wires into the MAP
sensors wiring harness and doesn't allow the sensor to send its maximum
voltage to the ECU, never telling the ECU that it has exceeded 0 psi of pressure.
The air bypass adapter is simply a check valve which you place between the
intake manifold and the sensor (the most common brand used is called the
MISSING LINK). When the air pressure exceeds 0 psi, the check valve opens
and diverts the air pressure from reaching the sensor. Either of these choices
has their ups and down but they generally get the job done rather inexpensively.
Proper monitoring of the system is a must so we will be adding a boost gauge,
EGT gauge (exhaust gas temperature) and a narrowband Air/fuel ration meter.
The reason we started with these 3 particular items is it is generally what every
do-it-yourself person seems to start out with. As we build on the system we will
document where these gauges are useful and what they should (and shouldn't)
be used for. A wideband oxygen sensor and logging software system will be
replacing just about all other gauges we will have shortly afterward.
Get your notepads and calculators ready because our next article will be all
about the MOST important part of adding a turbo kit and its NOT the turbo. It's
the fuel system, period. There are several methods used for improving the fuel
needs when adding a turbo kit and in the next segment we will show you some
options you have along with the advantages and disadvantages to each
system. If you want to turbo your car, upgrade the fuel system FIRST before you
even bother purchasing any other piece for your kit. The more you focus on the
fuel system, the better your chances are of having a reliable and powerful
setup. About 90% of the blown engines that occur after adding a turbo kit or
even a nitrous kit are due to improper fuel systems which were not up to par.
'Til next time!
