Quick Turbo Saturn FAQ:
Recommended Spark Plugs
NGK BKR7E(s-11) (DOHC and SOHC)
Stock No. 6097
or
NGK BCPR7ES (DOHC and SOHC)
Stock No. 3330
You can go with a ?6? heat range plug, which is ?hotter? and more prone to detonation. The stock
heat range is a ?5?. ?7? has been optimal for boost ranging from 4 to 20 pounds, among our
communities experience. Start your gap at .025 or so and work your way up until the boost blows
out the spark. The car may idle differently on cold mornings, with a slight misfire. The MSD DIS-2
will take care of most of this. Otherwise, it?s fine once you are on the road.
Recommended Fuel Pump
Walbro 255lph (also the same as the BBK and Holley fuel pump).
Model Number BP-WLB-32026
This fuel pump WILL fit the Saturn, however, it WILL also require custom modification. The Walbro
is a reputable brand with very reasonably priced fuel pumps, which flow more volume than the
stock pump. It is not a pressure based pump, though. If you plan on running a RRFPR or high fuel
pressure, add an MSD inline pump for extra pressure potential. Simply adding an MSD inline to the
stock system will not give you more volume. It is highly recommended that you re-wire the pump
with thicker gauge wire, though, and double ground it out, if necessary. When I complete this
modification, I?ll have detailed info and pics. Until then, we at least know there is an option that
works, even if it isn?t bolt in. Plus, every time I see the word, Walbro, I think of a walrus, and I
don?t know why, but its funnay.
Recommended Clutches
ACT Street clutch for up to 12 psi. Anything after that and go with the 6 puck. Better safe than
sorry with the clutch. The 6 puck WILL chatter, but generally is not too bad once broken in. The
ACT street clutch is smooth as butter, and is the only aftermarket clutch right now that uses a
pressure plate that is not a modified factory unit. The centerforce, in my experience, will last all of
30 minutes under boost. The Clutch Masters wears out extremely fast. The SPEC will induce
serious amounts of crankwalk? by experience not a misunderstimated strategery guestimation!
Recommended Gauges to get when boosting
Boost Gauge
A/F Gauge
Oil Pressure Gauge
Fuel Pressure Gauge
Another recommended item that I would get is a shift light. Even though it?s not really a gauge but
a simple small shift light can help you be more consistent as well as prevent you from hitting the rev
limiter, which could save you from an expensive mess. Hitting the rev limiter in a vehicle that cuts
fuel while under full boost will be disastrous! Stay AWAY from the rev limiter!
What size socket do I need to remove the stock oil galley plug?
8mm allen socket. This is accessible by using a ½ inch drive, 8mm allen socket, a universal joint,
and a long extention running up between the number 2 and 3 intake manifold runners. Put a
breaker bar on top and break it loose from above the motor. It will make a nasty farting/cracking
noise and you?ll think you had broken something, but you didn?t. The top picture here,
http://qksltwo.com/part2.html shows exactly where to source the oil feed. The size adapter you?ll
need is an M16 x 1.5 to a ?4AN fitting. These are available for JEGS or Summit and whatnot?.
Thanks to Rob, we now know that the 01?s use a smaller fitting. We?re waiting to hear from him
exactly what size. For the return line, you?ll want to use a ?10an or larger stainless braided line.
It?s very important that it?s downhill all the way to the pan. It needs to enter the pan ABOVE the oil
lever. You?ll need to pull the oil pan, and have another fitting welded on. The oil pan?s new from
Saturn are only $65.
Where do I tap my manifold for an EGT gauge?
The best place is the number 3 cylinder runner on the manifold. If you are looking straight on at
your engine bay, moving from left to the right , it?s the third runner from the left. The probe should
be placed 1-2" from the flange where the manifold/header meets the head.
Typical EGT (in Fahrenheit) readings at 7psi on a DOHC w/ SDS EIC.
Idle..................................................750
40mph cruising in 5th gear.........900
75mph cruising in 5th gear.........1200
WOT in 5th gear at 75mph..........1345
Readings will vary based on gearing, mph, temperature outside as well as your a/f mixture. You do
not want to exceed 1400 degrees Fahrenheit with a stock motor. This was tuned very rich? A car
with 24# injectors and an FMU ran substantially hotter? scary.
Turbo Fundamentals. Putting The Flying of Antelope Poop To rest.
How Turbos Work:
Ok, to begin? first a little physics - The Ideal Gas Law. Temperature, pressure, and volume are all
directly related. If you take a certain amount of gas, and compress it, both temperature and
pressure go up(this is why you MUST use an intercooler, but more on that later) If you give it
space to expand, pressure and temperature go down, equally oposite. Increase the temperature,
and the pressure goes up (in an enclosed space), or the volume goes up (it expands). Lastly,
gasses always want to flow from where there is higher pressures to where there is lower pressure.
Gasses get stressed out too, basically, like you know, the week of finals, when your girlfriend is
mad and all that jaz?
The way our inefficient piston engines do ?work? (if you can call it that by our underachieving
motors lol!) is by making gas expand in the encloses space (the combustion chamber; apparently
Saturn hired a bunch of 6 year olds, gave the coloring books and crayons, and said, ?make a
combustion chamber!?) which pushes the piston down so long as you don?t throw a rod and turns
the crank. In short, kaboom, piston pushes down, turns the crank? next detonation revolution
follows. A lot of heat is created in this process, but typically that is all wasted out through the
exhaust. Remember, heat is energy in its own form, we aren?t racist here. It's just not in the
cylinder long enough to transfer all that heat into mechanical energy, and it's not practical to make
cylinders "tall" enough to extract every last bit of work from that hot expanding gas.
So you wanna use that energy, eh?.
Ah? the turbocharger. This lil munchkin uses that hot exhaust energy that would otherwise go
unused and wasted in a n/a (not applicable) setup to turn a turbine. This turbine is connected to a
compressor section which compresses air. Air has a certain specific energy per volume. With
boost, you can fundamentally fit an enormous volume of air into the same size area; thus, you have
all the potential energy of the huge volume of air going in at the same speed and efficiency as a
like volume of air with less than half the energy(that?s the technical way of explaining it, Leyva!).
Now, here comes the whining of the supercharged/naturally aspirated/and others who don?t have a
turbo. ?But the turbo heats up the air because it?s connected to the exhaust.? Bah! No it
doesn?t. It heats up because it?s because its being compressed, just like a supercharger, or any
other compressed air. How much it gets heated up is much a factor of the compressor?s
efficiency, and turbos have the highest efficiency of any type of forced induction, and by a strong
margin. This is why we intercool these setups, as no matter how efficient your turbo is, boosting is
heating. Now, it is NOT heating up in any significant manner due to heat transfer from the exhaust.
Air chopping by a T-Too-Small (T25) would heat the air (by overspinning) 100x?s more than the
heat ?transfer? from the hot turbine section.
This is the closest thing to a "free lunch" that you will find in engineering, because you are taking
heat (energy) that would otherwise be wasted and getting usable work out of it, with almost no
tradeoffs. You gain a little complexity, and added manufacturing costs, but there is no real
performance hit from adding a turbo. Basically, it?s a headache, and don?t even think about it
unless you plan on getting under the car and wrenching yourself.
Lag. Lag? What?s that? http://www.geocities.com/turbosc2/sc2_hp.html A turbo car clears it?s
throat by 2000 rpm, and is making more torque by 2200 than a factory car. Below that it is exactly
the same as n/a. With a T3 sized turbo, you get a strong onset of boost by the mid 2000 rpm
range, and by 3000 you get more torque than a n/a Saturn makes anywhere in the powerband. Up
top, you simply get double the power, around 5-6 lbs of boost. Two engines, same weight. But a
MUCH wider powerband than a factory motor. Yes, despite what all the old 2-valvers say, a turbo
gives you the most versatile powerband short of a twin screw style positive displacement blower.
You?ll never have to downshift again.
"But doesn't the turbo increase exhaust backpressure?" Under boost conditions, no. Here's why:
When the exhaust valve opens, the pressure inside the cylinder is much much higher than the
pressure at the turbo inlet. That cylinder pressure "blows down" very quickly, but we're on the
exhaust stroke - the cylinder volume is decreasing very rapidly, and from the Ideal Gas Law, that
tends to keep the cylinder pressure higher than the turbo inlet pressure. Finally, when the exhaust
stroke is nearly done, and the pressures are nearly equal, the intake valve opens, the intake
pressure (we're under boost here!) "blows down" into the cylinder, and presto! We have a higher
cylinder pressure once again. Cylinder pressure make torque, torque at RPM (where the right
sized turbo gets jiggy wid it) makes power. Power makes speed. Yay!
Stuff I?m gonna Cover Later:
The Turbine, the Compressor, Building a Turbo
Where do I tap in to wire up my {insert any name turbo timer here) turbo timer?
Mike did a great turbo timer install article. Please look here:
http://www.turbosaturns.net/articles/turbo_timer_install.html
Will The AFC Work Well For Fuel Control?
Yes and No. It works great with Hondas. Here?s what they do: Use an AFC, double the size of
their injectors to 440?s, use a 2 bar map, and do the TPS to MAP sensor trick. Basically, instead
of the AFC using the TPS to determine how much fuel to add or subtract, you run that off a boost
reference, which obviously works much better for correct VE tables. Here?s the problem with doing
that on a Saturn that nobody is talking about: The PCM uses the MAP sensor as an input for a
delta table that controls timing. When you put in a 2 bar, you decrease the resolution, so when it
may be at 0 vac or even in boost, the computer still sees a strong vacuum, meaning part throttle. It
then advances the timing A LOT, according to a data logger. This is very bad for boost, naturally.
Using an afc with stock sized injectors is ok, because you won?t need to modify the signal to show
vacuum. But then you have defeated the purpose of it in the beginning?
Should I get a wastegate or a blow off valve?
Well a wastegate and blow off valve are two different things. A wastegate is on every turbo charged
vehicle, whether it is internal or external they all have ?em. Wastegates are what regulate the
amount of boost that your turbo puts out. When a certain pressure or psi is met it bleeds the air off
and doesn?t allow it to go into the charge pipe. Basically air bypasses the turbine wheel to
regulate the speed, which regulates the boost. I?m amazed at how precise they are at doing so, all
things considered. I have a dremel.
A blow off valve diverts excess air from going back to the turbo charger and causing compressor
surge. When you are at WOT and you are boosting you have ?x? amount of psi of air in your
charge pipe, when your TB closes that air has no where to go but back to turbo. So to prevent this
surge of air, you put a BOV on and let it vent out of the piping. The turbo can keep spinning this
way? that?s great for power, er, wheelspin into the next gear.
Do I need a blow off valve?
Yes. Go on ebay. They are cheap. Turbo XS makes good ones, Greedy(haha), HKS, and Blitz all
have nice, more expensive ones as well. The best, of course, are the turbosmart ones?
Do I need a 3" exhaust?
Again, depending on boost level you may gain little more than noise with a larger exhaust. A 3"
straight through exhaust is ideal for making more boost faster but if you are limiting boost to under
10psi a 3" turbo exhaust isn?t necessary. You can easily run a standard straight through cat-back
exhaust at 8psi without too much losses and it will be considerably quieter. This applies to
supercharged cars as well but supercharged cars can run even higher boost with less losses on a
standard cat-back exhaust. Mostly because supercharged cars will sound like ass if you go too big
on the exhaust. Turbo cars will sounds great, as the turbine wheel smoothes out the exhaust a lot.
Ignition
The MSD DIS-2 is optional, works fine on OBD-I cars (up to 95). Contact MSD for OBD-II cars.
MSD wires and the aforementioned plugs and you?re set.
How to select a compressor size to your application.
First you need to know how much air it will need to flow to reach your target horsepower. to figure
that, you would use the following formula:
(CID x RPM) / 3456 = CFM
Here's an example of an LLO:
(116Ci x 7000) / 3456 = 234CFM
Of course, if your engine is bored or stroked, you will have to compensate the CID.
The engine will flow 234CFM at 100% volumetric effeciency (VE). great, in a perfect world. actually
VE is about 80-90%. so you'll need to adjust to the VE. 85% is a good number to work with. so
addjust your CFM to 196CFM
Next up is the pressure ratio. The pressure ratio is basically the pressure of the air going into the
turbo in comparison to the pressure coming out. Unless you are running sequential turbos, the inlet
pressure will be the atmospheric pressure, which is an average of 14.7. So if you want 12psi,
here's the formula:
(12 + 14.7) / 14.7 = 1.82:1
Now you need the temperature rise. As the compressor compresses the air, it will raise the
temperature. There is a formula to figure that rise! There is an ideal temperature rise to where the
rise is equivalent to the amount of work it takes to compress the air. Here's the formula!
T2 = T1 (P2 ÷ P1)0.283
Confused yet? Of course not! But lets break it down with some back spins and stuff.
T2 = Outlet Temperature in °R
T1 = Inlet Temperature in °R
°R = °F + 460
P1 = Inlet Pressure Absolute
P2 = Outlet Pressure Absolute
Easier now huh?
Assuming it's 80º outside and we're shooting for 12psi, your inlet temperature (T1) = 80º + 460 =
540ºR
The P1 inlet pressure will be atmospheric in our case and the P2 outlet pressure will be 12psi.
atmospheric pressure is about 14.7 psi (as mentioned earlier), so the inlet pressure will be 14.7
psi, to figure the outlet pressure add the boost pressure to the inlet pressure.
P2 = 14.7 + 12 = 26.7 psi
We now have everything we need to figure out the ideal outlet temperature. Now take this info into
our original formula ( T2 = T1 (P2 ÷ P1)0.283 ) to figure out T2:
T2 = 540ºR(26.7 ÷ 14.7)0.283 = 676ºR
676ºR = 216ºF = ideal outlet temperature. That's a 136º temperature rise.
Once again, in a perfect world, these formulas work great. Unfortunately, there's our old friend
adiabatic efficiency (AE). a 136ºF temperature rise is at 100% AE. AE of the compressor is usually
65-75%. so you would use 70% for average. so to figure out the actual temperature rise from the
ideal temperature rise, you can use this:
Ideal Outlet Temperature Rise ÷ AE = Actual Outlet Temperature Rise
So, 136º ÷ .7 = 194º
Then you add the actual temperature rise to the intake temperature (80º) = 274º
Now you can figure out your density ratio! As the air is heated, it expands and increases the
volume and flow. To compare the inlet and outlet flow, you must know the density ratio. The formula
for that is:
(Inlet °R ÷ Outlet °R) × (Outlet Pressure ÷ Inlet Pressure) = Density Ratio
Ok, so our example formula would be:
(540ºR ÷ 676ºR) × (26.7 ÷ 14.7) = 1.46 Density Ratio
With all this crap, you can figure out what the actual inlet flow is in CFM. To do this, use this:
Outlet CFM × Density Ratio = Actual Inlet CFM
So!
234CFM × 1.46 = 341.64CFM
That's a 31% increase in CFM, which is a potential for 31% increase in power.
Size a turbo and multiply CFM by .069 to get lb/hr.
When looking at a compressor map, you match the corrected air flow (22.7lbs/min in our case) to
the pressure ratio (1.82:1 in our case). What you are looking to do is plot your graph where it
would be most efficient for the turbo. Anywhere below 60%, your turbo will spin entirely too fast of a
shaft speed rpm and burn itself up.
Ok?. I can?t type any more. I?ll go over more detail stuff at a later date.
Disclaimer. I wouldn?t believe much of anything I say. I didn?t come up with, or discover any of
this information, so most of it should be ?cleared for use?. That being said, I hope this helps.
Sorry for the lack of organization and such, but I don?t get paid for this so ah well!
Recommended Spark Plugs
NGK BKR7E(s-11) (DOHC and SOHC)
Stock No. 6097
or
NGK BCPR7ES (DOHC and SOHC)
Stock No. 3330
You can go with a ?6? heat range plug, which is ?hotter? and more prone to detonation. The stock
heat range is a ?5?. ?7? has been optimal for boost ranging from 4 to 20 pounds, among our
communities experience. Start your gap at .025 or so and work your way up until the boost blows
out the spark. The car may idle differently on cold mornings, with a slight misfire. The MSD DIS-2
will take care of most of this. Otherwise, it?s fine once you are on the road.
Recommended Fuel Pump
Walbro 255lph (also the same as the BBK and Holley fuel pump).
Model Number BP-WLB-32026
This fuel pump WILL fit the Saturn, however, it WILL also require custom modification. The Walbro
is a reputable brand with very reasonably priced fuel pumps, which flow more volume than the
stock pump. It is not a pressure based pump, though. If you plan on running a RRFPR or high fuel
pressure, add an MSD inline pump for extra pressure potential. Simply adding an MSD inline to the
stock system will not give you more volume. It is highly recommended that you re-wire the pump
with thicker gauge wire, though, and double ground it out, if necessary. When I complete this
modification, I?ll have detailed info and pics. Until then, we at least know there is an option that
works, even if it isn?t bolt in. Plus, every time I see the word, Walbro, I think of a walrus, and I
don?t know why, but its funnay.
Recommended Clutches
ACT Street clutch for up to 12 psi. Anything after that and go with the 6 puck. Better safe than
sorry with the clutch. The 6 puck WILL chatter, but generally is not too bad once broken in. The
ACT street clutch is smooth as butter, and is the only aftermarket clutch right now that uses a
pressure plate that is not a modified factory unit. The centerforce, in my experience, will last all of
30 minutes under boost. The Clutch Masters wears out extremely fast. The SPEC will induce
serious amounts of crankwalk? by experience not a misunderstimated strategery guestimation!
Recommended Gauges to get when boosting
Boost Gauge
A/F Gauge
Oil Pressure Gauge
Fuel Pressure Gauge
Another recommended item that I would get is a shift light. Even though it?s not really a gauge but
a simple small shift light can help you be more consistent as well as prevent you from hitting the rev
limiter, which could save you from an expensive mess. Hitting the rev limiter in a vehicle that cuts
fuel while under full boost will be disastrous! Stay AWAY from the rev limiter!
What size socket do I need to remove the stock oil galley plug?
8mm allen socket. This is accessible by using a ½ inch drive, 8mm allen socket, a universal joint,
and a long extention running up between the number 2 and 3 intake manifold runners. Put a
breaker bar on top and break it loose from above the motor. It will make a nasty farting/cracking
noise and you?ll think you had broken something, but you didn?t. The top picture here,
http://qksltwo.com/part2.html shows exactly where to source the oil feed. The size adapter you?ll
need is an M16 x 1.5 to a ?4AN fitting. These are available for JEGS or Summit and whatnot?.
Thanks to Rob, we now know that the 01?s use a smaller fitting. We?re waiting to hear from him
exactly what size. For the return line, you?ll want to use a ?10an or larger stainless braided line.
It?s very important that it?s downhill all the way to the pan. It needs to enter the pan ABOVE the oil
lever. You?ll need to pull the oil pan, and have another fitting welded on. The oil pan?s new from
Saturn are only $65.
Where do I tap my manifold for an EGT gauge?
The best place is the number 3 cylinder runner on the manifold. If you are looking straight on at
your engine bay, moving from left to the right , it?s the third runner from the left. The probe should
be placed 1-2" from the flange where the manifold/header meets the head.
Typical EGT (in Fahrenheit) readings at 7psi on a DOHC w/ SDS EIC.
Idle..................................................750
40mph cruising in 5th gear.........900
75mph cruising in 5th gear.........1200
WOT in 5th gear at 75mph..........1345
Readings will vary based on gearing, mph, temperature outside as well as your a/f mixture. You do
not want to exceed 1400 degrees Fahrenheit with a stock motor. This was tuned very rich? A car
with 24# injectors and an FMU ran substantially hotter? scary.
Turbo Fundamentals. Putting The Flying of Antelope Poop To rest.
How Turbos Work:
Ok, to begin? first a little physics - The Ideal Gas Law. Temperature, pressure, and volume are all
directly related. If you take a certain amount of gas, and compress it, both temperature and
pressure go up(this is why you MUST use an intercooler, but more on that later) If you give it
space to expand, pressure and temperature go down, equally oposite. Increase the temperature,
and the pressure goes up (in an enclosed space), or the volume goes up (it expands). Lastly,
gasses always want to flow from where there is higher pressures to where there is lower pressure.
Gasses get stressed out too, basically, like you know, the week of finals, when your girlfriend is
mad and all that jaz?
The way our inefficient piston engines do ?work? (if you can call it that by our underachieving
motors lol!) is by making gas expand in the encloses space (the combustion chamber; apparently
Saturn hired a bunch of 6 year olds, gave the coloring books and crayons, and said, ?make a
combustion chamber!?) which pushes the piston down so long as you don?t throw a rod and turns
the crank. In short, kaboom, piston pushes down, turns the crank? next detonation revolution
follows. A lot of heat is created in this process, but typically that is all wasted out through the
exhaust. Remember, heat is energy in its own form, we aren?t racist here. It's just not in the
cylinder long enough to transfer all that heat into mechanical energy, and it's not practical to make
cylinders "tall" enough to extract every last bit of work from that hot expanding gas.
So you wanna use that energy, eh?.
Ah? the turbocharger. This lil munchkin uses that hot exhaust energy that would otherwise go
unused and wasted in a n/a (not applicable) setup to turn a turbine. This turbine is connected to a
compressor section which compresses air. Air has a certain specific energy per volume. With
boost, you can fundamentally fit an enormous volume of air into the same size area; thus, you have
all the potential energy of the huge volume of air going in at the same speed and efficiency as a
like volume of air with less than half the energy(that?s the technical way of explaining it, Leyva!).
Now, here comes the whining of the supercharged/naturally aspirated/and others who don?t have a
turbo. ?But the turbo heats up the air because it?s connected to the exhaust.? Bah! No it
doesn?t. It heats up because it?s because its being compressed, just like a supercharger, or any
other compressed air. How much it gets heated up is much a factor of the compressor?s
efficiency, and turbos have the highest efficiency of any type of forced induction, and by a strong
margin. This is why we intercool these setups, as no matter how efficient your turbo is, boosting is
heating. Now, it is NOT heating up in any significant manner due to heat transfer from the exhaust.
Air chopping by a T-Too-Small (T25) would heat the air (by overspinning) 100x?s more than the
heat ?transfer? from the hot turbine section.
This is the closest thing to a "free lunch" that you will find in engineering, because you are taking
heat (energy) that would otherwise be wasted and getting usable work out of it, with almost no
tradeoffs. You gain a little complexity, and added manufacturing costs, but there is no real
performance hit from adding a turbo. Basically, it?s a headache, and don?t even think about it
unless you plan on getting under the car and wrenching yourself.
Lag. Lag? What?s that? http://www.geocities.com/turbosc2/sc2_hp.html A turbo car clears it?s
throat by 2000 rpm, and is making more torque by 2200 than a factory car. Below that it is exactly
the same as n/a. With a T3 sized turbo, you get a strong onset of boost by the mid 2000 rpm
range, and by 3000 you get more torque than a n/a Saturn makes anywhere in the powerband. Up
top, you simply get double the power, around 5-6 lbs of boost. Two engines, same weight. But a
MUCH wider powerband than a factory motor. Yes, despite what all the old 2-valvers say, a turbo
gives you the most versatile powerband short of a twin screw style positive displacement blower.
You?ll never have to downshift again.
"But doesn't the turbo increase exhaust backpressure?" Under boost conditions, no. Here's why:
When the exhaust valve opens, the pressure inside the cylinder is much much higher than the
pressure at the turbo inlet. That cylinder pressure "blows down" very quickly, but we're on the
exhaust stroke - the cylinder volume is decreasing very rapidly, and from the Ideal Gas Law, that
tends to keep the cylinder pressure higher than the turbo inlet pressure. Finally, when the exhaust
stroke is nearly done, and the pressures are nearly equal, the intake valve opens, the intake
pressure (we're under boost here!) "blows down" into the cylinder, and presto! We have a higher
cylinder pressure once again. Cylinder pressure make torque, torque at RPM (where the right
sized turbo gets jiggy wid it) makes power. Power makes speed. Yay!
Stuff I?m gonna Cover Later:
The Turbine, the Compressor, Building a Turbo
Where do I tap in to wire up my {insert any name turbo timer here) turbo timer?
Mike did a great turbo timer install article. Please look here:
http://www.turbosaturns.net/articles/turbo_timer_install.html
Will The AFC Work Well For Fuel Control?
Yes and No. It works great with Hondas. Here?s what they do: Use an AFC, double the size of
their injectors to 440?s, use a 2 bar map, and do the TPS to MAP sensor trick. Basically, instead
of the AFC using the TPS to determine how much fuel to add or subtract, you run that off a boost
reference, which obviously works much better for correct VE tables. Here?s the problem with doing
that on a Saturn that nobody is talking about: The PCM uses the MAP sensor as an input for a
delta table that controls timing. When you put in a 2 bar, you decrease the resolution, so when it
may be at 0 vac or even in boost, the computer still sees a strong vacuum, meaning part throttle. It
then advances the timing A LOT, according to a data logger. This is very bad for boost, naturally.
Using an afc with stock sized injectors is ok, because you won?t need to modify the signal to show
vacuum. But then you have defeated the purpose of it in the beginning?
Should I get a wastegate or a blow off valve?
Well a wastegate and blow off valve are two different things. A wastegate is on every turbo charged
vehicle, whether it is internal or external they all have ?em. Wastegates are what regulate the
amount of boost that your turbo puts out. When a certain pressure or psi is met it bleeds the air off
and doesn?t allow it to go into the charge pipe. Basically air bypasses the turbine wheel to
regulate the speed, which regulates the boost. I?m amazed at how precise they are at doing so, all
things considered. I have a dremel.
A blow off valve diverts excess air from going back to the turbo charger and causing compressor
surge. When you are at WOT and you are boosting you have ?x? amount of psi of air in your
charge pipe, when your TB closes that air has no where to go but back to turbo. So to prevent this
surge of air, you put a BOV on and let it vent out of the piping. The turbo can keep spinning this
way? that?s great for power, er, wheelspin into the next gear.
Do I need a blow off valve?
Yes. Go on ebay. They are cheap. Turbo XS makes good ones, Greedy(haha), HKS, and Blitz all
have nice, more expensive ones as well. The best, of course, are the turbosmart ones?
Do I need a 3" exhaust?
Again, depending on boost level you may gain little more than noise with a larger exhaust. A 3"
straight through exhaust is ideal for making more boost faster but if you are limiting boost to under
10psi a 3" turbo exhaust isn?t necessary. You can easily run a standard straight through cat-back
exhaust at 8psi without too much losses and it will be considerably quieter. This applies to
supercharged cars as well but supercharged cars can run even higher boost with less losses on a
standard cat-back exhaust. Mostly because supercharged cars will sound like ass if you go too big
on the exhaust. Turbo cars will sounds great, as the turbine wheel smoothes out the exhaust a lot.
Ignition
The MSD DIS-2 is optional, works fine on OBD-I cars (up to 95). Contact MSD for OBD-II cars.
MSD wires and the aforementioned plugs and you?re set.
How to select a compressor size to your application.
First you need to know how much air it will need to flow to reach your target horsepower. to figure
that, you would use the following formula:
(CID x RPM) / 3456 = CFM
Here's an example of an LLO:
(116Ci x 7000) / 3456 = 234CFM
Of course, if your engine is bored or stroked, you will have to compensate the CID.
The engine will flow 234CFM at 100% volumetric effeciency (VE). great, in a perfect world. actually
VE is about 80-90%. so you'll need to adjust to the VE. 85% is a good number to work with. so
addjust your CFM to 196CFM
Next up is the pressure ratio. The pressure ratio is basically the pressure of the air going into the
turbo in comparison to the pressure coming out. Unless you are running sequential turbos, the inlet
pressure will be the atmospheric pressure, which is an average of 14.7. So if you want 12psi,
here's the formula:
(12 + 14.7) / 14.7 = 1.82:1
Now you need the temperature rise. As the compressor compresses the air, it will raise the
temperature. There is a formula to figure that rise! There is an ideal temperature rise to where the
rise is equivalent to the amount of work it takes to compress the air. Here's the formula!
T2 = T1 (P2 ÷ P1)0.283
Confused yet? Of course not! But lets break it down with some back spins and stuff.
T2 = Outlet Temperature in °R
T1 = Inlet Temperature in °R
°R = °F + 460
P1 = Inlet Pressure Absolute
P2 = Outlet Pressure Absolute
Easier now huh?
Assuming it's 80º outside and we're shooting for 12psi, your inlet temperature (T1) = 80º + 460 =
540ºR
The P1 inlet pressure will be atmospheric in our case and the P2 outlet pressure will be 12psi.
atmospheric pressure is about 14.7 psi (as mentioned earlier), so the inlet pressure will be 14.7
psi, to figure the outlet pressure add the boost pressure to the inlet pressure.
P2 = 14.7 + 12 = 26.7 psi
We now have everything we need to figure out the ideal outlet temperature. Now take this info into
our original formula ( T2 = T1 (P2 ÷ P1)0.283 ) to figure out T2:
T2 = 540ºR(26.7 ÷ 14.7)0.283 = 676ºR
676ºR = 216ºF = ideal outlet temperature. That's a 136º temperature rise.
Once again, in a perfect world, these formulas work great. Unfortunately, there's our old friend
adiabatic efficiency (AE). a 136ºF temperature rise is at 100% AE. AE of the compressor is usually
65-75%. so you would use 70% for average. so to figure out the actual temperature rise from the
ideal temperature rise, you can use this:
Ideal Outlet Temperature Rise ÷ AE = Actual Outlet Temperature Rise
So, 136º ÷ .7 = 194º
Then you add the actual temperature rise to the intake temperature (80º) = 274º
Now you can figure out your density ratio! As the air is heated, it expands and increases the
volume and flow. To compare the inlet and outlet flow, you must know the density ratio. The formula
for that is:
(Inlet °R ÷ Outlet °R) × (Outlet Pressure ÷ Inlet Pressure) = Density Ratio
Ok, so our example formula would be:
(540ºR ÷ 676ºR) × (26.7 ÷ 14.7) = 1.46 Density Ratio
With all this crap, you can figure out what the actual inlet flow is in CFM. To do this, use this:
Outlet CFM × Density Ratio = Actual Inlet CFM
So!
234CFM × 1.46 = 341.64CFM
That's a 31% increase in CFM, which is a potential for 31% increase in power.
Size a turbo and multiply CFM by .069 to get lb/hr.
When looking at a compressor map, you match the corrected air flow (22.7lbs/min in our case) to
the pressure ratio (1.82:1 in our case). What you are looking to do is plot your graph where it
would be most efficient for the turbo. Anywhere below 60%, your turbo will spin entirely too fast of a
shaft speed rpm and burn itself up.
Ok?. I can?t type any more. I?ll go over more detail stuff at a later date.
Disclaimer. I wouldn?t believe much of anything I say. I didn?t come up with, or discover any of
this information, so most of it should be ?cleared for use?. That being said, I hope this helps.
Sorry for the lack of organization and such, but I don?t get paid for this so ah well!