Turbo FAQ
08-26-2004, 09:53 AM
#1
Turbo FAQ Starting a FAQ for this section, will try to keep it updated, PM me if you want anything added or sugestions.
Some good reading for the basics about turbochargers and understanding compressor maps
thanks to Jose (JZ 97 SS 1500) for this
http://www.forcedinductions.com/help.htm
What other things do i need when i boost my beast
You need the proper balance of fuel, air and ignition
the more air you put into your engine the more fuel you will need
so bigger injectors and bigger pump are a must., after ALOT of power increase you will have to upgrade your fuel lines and fuel rails.
Tuning, you need to have it tunned properly
the only HP limit the lsx engine see is tunning, no one tha i know of have split their block because they made to much power, but i have seen alot of times where they put a hole through their block because of poor tunning.
Drivetrain: you need to have stronger componets to handle all that extra power your now running. You need a stronger clutch, built tranny, stonger driveshaft and rear end.
Suspension: you have to put the power to the ground if you want to make use of it, so get your suspension worked out. Get a strong torque arm too, so it doesnt end up braking.
How much boost can i run
0-infinate Psi
basically you are limited to octane and timing, the more boost you use the more easily the mixture can pre-ignite (which causes knock), so you have to use a fuel that ignites on a higher temperature (aka higher octane fuel) or pull enough timing.
to give a ruff estimate most people use about 7psi on a stock compression ratio engine (10.1-10.5:1)
if you lower the compression ratio in your engine by larger combustion chamber heads, thicker gaskets or dished pistions, this will also allow you to run more boost on the given octane.
What size turbo should i use
http://www.forcedinductions.com/help.htm has alot of good information on selecting a turbo that will suite your needs.
Basically you need to start by knowing your power goals. Select a turbo that will support that power level.
next where in the RPM range it makes its power is also important. This can tuned by selecting the A/R of the exhaust housing. the smaller the AR the faster the turbo will spool and make more power, lower in the RPM range, but will choke off power in the upper RPM range. A larger AR will spool later in the RPM range, but will make more power in the Upper RPM range.
why isnt anyone running 30psi or more on an LSx engine like the imports do
psi or boost is resistance to flow
psi is irrelevlant, how much air goes through your engine is important. ALot of people give an example of two straws one really thin, one large. If you blow into the small staw it is harder as the velocity of the air increases, but not a whole lot of air is moving. Switch to the larger staw, it is easier velocity is low but your pushing alot of air through it.
these 346 cubed or larger engines flow very well. so 15psi can make around 700rwhp.
UPDATE: casper from W2W has ran a 6.866@205 with around 30-40lbs of boost. First production LS-style block in the 6's! so hows that for comparing it to import boost level.
how much power will i make if im running Xpsi or increase it xpsi?
there are alot of varibles and some other thing in contribution, but if you start out with what your engine makes NA
(0psi) you double the power at 1 atmosphere (14.7psi or 1 bar) so we can come up with a rough formula of
new power = [ ( NA power / 14.7 ) * amount of boost ] + NA power
Can i run a turbo on my high CR engine and low lsa cam
Not really, well yes but it wont do as well. WIth a higher CR then stock your going to have problems not running high enough octane, you will be fighting knock so you wont be able to use enough boost to make it worth your while.
The low lsa cam also isnt best for your turbo, it will bleed off boost and not give enough gas flow velocity till the upper part of the RPM range.
what cam should i use with my turbo set up?
There is alot of debate here but first off the stock cam does pretty well. a higher lsa seems to be more desirable 114-117. this will bring the exhasut gas velocity up faster and spool the turbo more in the rpm range and not tend to bleed off boost. It needs to be matched to your setup also when you want the power to come on, and how high you plan on spinning your motor.
for the duration it needs to be matched to your engine size, intake and exhaust manafolds. The larger the engine the higher overall the duration should be. It was explained once to me that you want the intake duration larger then the exhaust that way you have a higher exhaust velocity which helps spin the turbo better.
Other theories have said that it depends on your headers, if you have a good flowing header that the exhaust duration should be greater then the
intake, if you have an inefficiant header that the exhaust duration should be lower then the intake duration. If you have a good intake and header set up they should be equal.
Id like to see specific testing so there could be definate answers.
should i go witha twin or single
either or i dont beleive in performance that it matters. As long as the exhaust to and from the turbo chager(s) are of equal effiency both will spool the same (depending on the selection of the turbos) and make similair power if the right turbos are choosen.
if buyng a kit, choose the one that will fits your needs.
if building your own, the things that should be the desiding factor should be packaging, ease of being albe to work on it, cost, availabilty, weight.
Note alot of race classes twins are outlawed. And most of the realy heavy hitters are using a BIG single.
Most turbo companies say a twin is better for the street for good spool up, but the singles are more efficient on the top end with regards to racing.
some more reading, also talks about compond charging http://www.hotrod.com/techarticles/e...bo/index2.html
What intercooler should i go with
you have two choices in IC's Air to water or air to air
which one is right for you.
generally people use aire to air for the street and air to water for the track.
with the A2W IC you can put ice in the water box you can get the IAT down below ambiant temperature. Member testing shows that A2W ic's with just water works well on the street.
A2A is a very simple design. With a properly sized core it will work well and generally be less expensive then a A2W. It will also do a good job on the street or track if properly sized
Some good reading for the basics about turbochargers and understanding compressor maps
thanks to Jose (JZ 97 SS 1500) for this
http://www.forcedinductions.com/help.htm
What other things do i need when i boost my beast
You need the proper balance of fuel, air and ignition
the more air you put into your engine the more fuel you will need
so bigger injectors and bigger pump are a must., after ALOT of power increase you will have to upgrade your fuel lines and fuel rails.
Tuning, you need to have it tunned properly
the only HP limit the lsx engine see is tunning, no one tha i know of have split their block because they made to much power, but i have seen alot of times where they put a hole through their block because of poor tunning.
Drivetrain: you need to have stronger componets to handle all that extra power your now running. You need a stronger clutch, built tranny, stonger driveshaft and rear end.
Suspension: you have to put the power to the ground if you want to make use of it, so get your suspension worked out. Get a strong torque arm too, so it doesnt end up braking.
How much boost can i run
0-infinate Psi
basically you are limited to octane and timing, the more boost you use the more easily the mixture can pre-ignite (which causes knock), so you have to use a fuel that ignites on a higher temperature (aka higher octane fuel) or pull enough timing.
to give a ruff estimate most people use about 7psi on a stock compression ratio engine (10.1-10.5:1)
if you lower the compression ratio in your engine by larger combustion chamber heads, thicker gaskets or dished pistions, this will also allow you to run more boost on the given octane.
What size turbo should i use
http://www.forcedinductions.com/help.htm has alot of good information on selecting a turbo that will suite your needs.
Basically you need to start by knowing your power goals. Select a turbo that will support that power level.
next where in the RPM range it makes its power is also important. This can tuned by selecting the A/R of the exhaust housing. the smaller the AR the faster the turbo will spool and make more power, lower in the RPM range, but will choke off power in the upper RPM range. A larger AR will spool later in the RPM range, but will make more power in the Upper RPM range.
why isnt anyone running 30psi or more on an LSx engine like the imports do
psi or boost is resistance to flow
psi is irrelevlant, how much air goes through your engine is important. ALot of people give an example of two straws one really thin, one large. If you blow into the small staw it is harder as the velocity of the air increases, but not a whole lot of air is moving. Switch to the larger staw, it is easier velocity is low but your pushing alot of air through it.
these 346 cubed or larger engines flow very well. so 15psi can make around 700rwhp.
UPDATE: casper from W2W has ran a 6.866@205 with around 30-40lbs of boost. First production LS-style block in the 6's! so hows that for comparing it to import boost level.
how much power will i make if im running Xpsi or increase it xpsi?
there are alot of varibles and some other thing in contribution, but if you start out with what your engine makes NA
(0psi) you double the power at 1 atmosphere (14.7psi or 1 bar) so we can come up with a rough formula of
new power = [ ( NA power / 14.7 ) * amount of boost ] + NA power
Can i run a turbo on my high CR engine and low lsa cam
Not really, well yes but it wont do as well. WIth a higher CR then stock your going to have problems not running high enough octane, you will be fighting knock so you wont be able to use enough boost to make it worth your while.
The low lsa cam also isnt best for your turbo, it will bleed off boost and not give enough gas flow velocity till the upper part of the RPM range.
what cam should i use with my turbo set up?
There is alot of debate here but first off the stock cam does pretty well. a higher lsa seems to be more desirable 114-117. this will bring the exhasut gas velocity up faster and spool the turbo more in the rpm range and not tend to bleed off boost. It needs to be matched to your setup also when you want the power to come on, and how high you plan on spinning your motor.
for the duration it needs to be matched to your engine size, intake and exhaust manafolds. The larger the engine the higher overall the duration should be. It was explained once to me that you want the intake duration larger then the exhaust that way you have a higher exhaust velocity which helps spin the turbo better.
Other theories have said that it depends on your headers, if you have a good flowing header that the exhaust duration should be greater then the
intake, if you have an inefficiant header that the exhaust duration should be lower then the intake duration. If you have a good intake and header set up they should be equal.
Id like to see specific testing so there could be definate answers.
should i go witha twin or single
either or i dont beleive in performance that it matters. As long as the exhaust to and from the turbo chager(s) are of equal effiency both will spool the same (depending on the selection of the turbos) and make similair power if the right turbos are choosen.
if buyng a kit, choose the one that will fits your needs.
if building your own, the things that should be the desiding factor should be packaging, ease of being albe to work on it, cost, availabilty, weight.
Note alot of race classes twins are outlawed. And most of the realy heavy hitters are using a BIG single.
Most turbo companies say a twin is better for the street for good spool up, but the singles are more efficient on the top end with regards to racing.
some more reading, also talks about compond charging http://www.hotrod.com/techarticles/e...bo/index2.html
What intercooler should i go with
you have two choices in IC's Air to water or air to air
which one is right for you.
generally people use aire to air for the street and air to water for the track.
with the A2W IC you can put ice in the water box you can get the IAT down below ambiant temperature. Member testing shows that A2W ic's with just water works well on the street.
A2A is a very simple design. With a properly sized core it will work well and generally be less expensive then a A2W. It will also do a good job on the street or track if properly sized
Last edited by Nine Ball; 01-23-2007 at 11:09 AM. Reason: removed vendor names
01-17-2005, 02:16 PM
#2
Thanks to Term for this post
What parts make up a basic turbo kit?
Most turbo kits come with the following parts, these are talked about in further detail later in this FAQ
Hot side exhaust
Turbocharger
Wastegate (If turbo does not have a internal wastegate)
Blowoff valve
Silicone Connector pipes, tbolt clamps
Intake piping, downpipe.
Boost referenced fuel pressure regulator
Optional parts are
Intercooler & Intercooler piping
Most kits do not come with fuel components, tuning software or wideband o2 sensors, all of which are a good idea!
Whats up with methonal/alcohol/water injection?
Methonal injection is methonal (high octane fuel) and injected into the intake pipes, this helps prevent detonation when you are running on lower octane fuel and or non-intercooled applications. Methonal injection systems can be had for a few hundred dollars.
It can be mixed with water or run straight.
Alcohol is also a "high octane fuel" which helps surpress detonation like methonal, it to can be run straight or mixed with water.
Water injection cools the intake charge which alows you to run more boost with surpressed detionation.
What is "hot side exhaust"
Hot side exhaust is the exhaust piece(s) that bolt onto the heads and work their way to the turbo(s). These pieces can be
purchased from several different kits if you are making your own custom setup or if you really want, several sponsors on here
can make custom hot side exhaust to fit any application.
Parts of a turbo
Here is a basic cutaway image that shows different parts of a turbo, this image does not show the exhaust inlet which can be
seen under the Exhaust Turbine section of this FAQ
What is the downpipe?
The downpipe is a pipe that connects to the turbo on the other side of the exhaust turbine, this pipe generally connects to
the factory exhaust system.
How is boost controlled?
The amount of boost generated by a turbo is controlled by a large valve called a Wastegate. The Wastegate is mounted on a
flange that is generally welded onto the hot exhaust piece close to the turbo flange.
When boost reaches the desired level, a boost controller diverts pressure into the wastegate allowing the valve to open and
vent exhaust gas out the other side of the valve, this prevents the turbo from spooling faster than it is already going and
potentially slows it down some depending on how far the gate opens. There is a wide range of boost controllers manual and electronic available for fairly reasonable prices.
( Pictured : TiAL 46mm Wastegate )
Note : Some turbos have internal wastegates, which means the hot exhaust piece will not have a wastegate flange on it.
What is a blowoff valve?
Blowoff valves are to relieve pressure when your throttle blade closes, if your turbo is spooled up and pushing major air, and you let off the throttle without one, it can cause your turbo to backspin and cause excessive wear on the bearings. This valve is more important to cars with manual transmissions.
( Pictured : TiAL 50mm Blowoff Valve )
What is A/R?
The A/R of the exhaust is a ratio of the exhaust housinginlet area to radius. the smaller A/R will spool faster, but choke off sooner.
the higher A/R will spool later but make more power and higher in the RPM band.
What is the Exhaust Housing?
The exhaust side of the turbo is usually darker in color, this is where exhaust gas flows through the turbo to spin the compressor side. Inside the exhaust housing is a turbine, pictured in the cutaway view above.
( Pictured : Garrett GT42 Turbo )
What is the Compressor Housing?
The lighter, or polished in some caes side of the turbo, spun by the exhaust turbine this part of the turbo actually creates the pressure by spinning the compressor wheel.
When you hear people talk about the compressor turbine (or "compressor wheel") you might hear the words Inducer and Exducer size, here is a visual representation of what thoes are.
( Pictured : Compressor wheel, Inducer and Exducer labeled )
To find the trim of your turbo use the following formula
Trim = (Inducer / Exducer) ^2 * 100
( Pictured : Garrett GT42 Turbo )
Where can I tap and return oil on the LS1?
There is a number of places you can tap and return oil on the LS1, here are a few of them.
Tap Locations:
Above the oil filter, there is a blockoff plate that you can get filtered pressurized oil from.
<ADD PIC HERE>
Return Locations:
Oil returns need to be someplace oil can drain back into your oil pan freely, it must be above the oil level in your oil pan, and below your turbo, remember that if you make this line hard to flow oil through, your turbo may have problems with seals in the future.
<ADD PICS HERE>
The gravity oil drain line from a turbo should not be at any more than a 30 degree angle when leaving the turbo.
Who makes the "best" turbo kit?
Who makes the best cam? What is the best grind? Which turbo is best? None of these questions can be answered because each car has its own goals, so if your posting asking for help with kit selection do some homework instead of just asking which kit is best, and know what your goals are. Here are some things to consider while selecting a kit.
What is your horsepower goal?
Do you want to keep your A/C?
Do you have tuning software?
Are you willing to put the money into your fuel system?
Last edited by smokinHawk; 01-25-2005 at 05:57 AM.
02-07-2005, 06:18 AM
#3
thanks to Boostaholic for this
Originally Posted by Boostaholic
How do I select fuel injectors for a forced induction application?
First you need to figure out what BSFC (Brake Specific Fuel Consumption) value you will use, BSFC is the pounds of fuel the engine burns per HP per hour.
Here are some BSFC guidelines.
.45 for N/A motors
.55 for supercharged
.65 for turbo
Injector Size in LB/HR = ((Desired Flywheel HP) * BSFC) / (# of cyls * Duty Cycle % / 100)
These simplified versions can be used for V8 motors with 80% duty cycle
Turbos : LB/HR = (Desired HP * .65) / 6.4
Superchargers : LB/HR = (Desired HP * .55) / 6.4
Example
(600 * .65) / (8 * .80)
Gives me
390 / 6.4
Result : 60LB/HR
For more information on this topic, see http://www.holley.com/HiOctn/TechSer...l/Artcl07.html
First you need to figure out what BSFC (Brake Specific Fuel Consumption) value you will use, BSFC is the pounds of fuel the engine burns per HP per hour.
Here are some BSFC guidelines.
.45 for N/A motors
.55 for supercharged
.65 for turbo
Injector Size in LB/HR = ((Desired Flywheel HP) * BSFC) / (# of cyls * Duty Cycle % / 100)
These simplified versions can be used for V8 motors with 80% duty cycle
Turbos : LB/HR = (Desired HP * .65) / 6.4
Superchargers : LB/HR = (Desired HP * .55) / 6.4
Example
(600 * .65) / (8 * .80)
Gives me
390 / 6.4
Result : 60LB/HR
For more information on this topic, see http://www.holley.com/HiOctn/TechSer...l/Artcl07.html
Last edited by smokinHawk; 08-28-2007 at 07:13 AM.
10-18-2005, 05:47 AM
#4
Why did my electric superchargers, tornado air intakes, whistle tips, fake BOVS, fake turbo noise or any other fake worthless crap post get locked
This is a tech board about real FI setups, any worthless post like that that will not make power will get locked. I want to keep this section clean and not have members have to sift through worthless crap to find something good. You want to post about that stuff go to the honda boards.
Over here we want to focus about making power.
This is a tech board about real FI setups, any worthless post like that that will not make power will get locked. I want to keep this section clean and not have members have to sift through worthless crap to find something good. You want to post about that stuff go to the honda boards.
Over here we want to focus about making power.
11-16-2005, 05:51 PM
#6
Thanks to Jose (JZ 97 SS 1500) for more on theory of turbos
http://www.forcedinductions.com/helpadvanced.htm
http://www.forcedinductions.com/helpadvanced.htm
12-12-2005, 05:17 AM
#7
Thanks to V8_DSM_V8again for a good find on more turbo maps and some supercharger flow and consumption maps.
http://not2fast.com/turbo/maps/
http://not2fast.com/turbo/maps/
Trending Topics
03-24-2006, 05:15 AM
#8
Three bar map sensors
GM Style 3 Bar Pressure Sensors
Manufacturer Part Number
GM (old)* 16040749
AC Delco (old)* 213-101
GM (new)** 12223861
AC Delco (new)** 213-1562
MSD** 2313
MSD (compact)** 23131
Borg Warner** EC1678
NAPA CRB219481
Electromotive Engine Controls 71130
Holley 538-23
GM Style 3 Bar Pressure Sensors
Manufacturer Part Number
GM (old)* 16040749
AC Delco (old)* 213-101
GM (new)** 12223861
AC Delco (new)** 213-1562
MSD** 2313
MSD (compact)** 23131
Borg Warner** EC1678
NAPA CRB219481
Electromotive Engine Controls 71130
Holley 538-23
04-30-2007, 08:06 AM
#10
for info about what spark plug number this thread has alot of info
https://ls1tech.com/forums/showthrea...7&page=1&pp=40
https://ls1tech.com/forums/showthrea...7&page=1&pp=40
08-05-2008, 03:19 PM
#11
e-Boost 2 for the novice This should get anyone out and running around with one.
Wire it:
The two wires from the solenoid go to the grey and brown wire from the controller, they can be hooked up either way.
Pull out the white wire if you want the controller to turn something on with boost. This will get hooked in as the NEGATIVE on a relay to run the thing (such as a fuel pump).
Find a positive source that is on anytime the car is running. You need your boost controller working in the daytime as well as night when the instrument cluster is lit.
Plumb it:
The standard external configuration works fine 90% of the time. Connect port one of the solenoid to a ‘boost only ahead of throttle body’ area along with the ‘bottom’ wastegate port. I use the fitting at the turbo housing discharge for this. Port 3 gets vented to atmosphere but still put some hose on it to keep water out. Port 1 goes to the ‘top’ or end port of the wastegate. Hook a manifold source to the controller itself (VAC AND BOOST)
Acronyms:
BG = inside each boost group are settings for controlling a particular level of boost.
Extra boost groups are not editable until they are activated.
SP = the target max boost in any separate BG. 0 = wastegate spring pressure, 99= max boost possible with the current solenoid configuration, and turbo/engine configuration. 50 does not mean 50psi boost target. Just set the number to where it needs to be to perfect what you want in a particular group.
GP = gate pressure. The boost controller does not let any boost signal to the wastegate until this pressure is attained. This is for quickest spool time. Too high and you will get overshoot, too low and it will spool as it would without the controller. I stay 3psi or so below SP.
SN = sensitivity. Too low and you will ‘creep’ to max boost, too high and the boost curve will fluctuate after max boost is achieved. 20 is a safe bet.
OBS = overboost shutdown, kills boost if it goes too far. If your car slows down when you turned the boost up, this could be why! Put this @ 2psi over the max boost of your highest SP.
BGR = bar graph (led display under boost display on the gauge)
AL = alarm sounds not very loud at a determined boost point
NSP = how many boost groups you have activated, 1 to 6 possible
AU = Auxiliary output (white wire that goes negative) at a determined boost point
PHb = Recall of the highest boost reached since PHb was last selected
Set up:
Pushing mode and down together gets you to BG, SP, GP, SN
Pushing mode and up together gets you to OBS, BGR, AL, NSP, & AU
Push mode to edit a particular section. Push up or down to increment during editing. Hold mode to save and again to back up.
Push up or down to scroll through functions to find ones you want to edit.
Use Tips:
Every time power is cycled to the controller it will go back to BG1.
While on the live boost (default) screen every time you hit up it will move you into the next boost group depending on how many you have activated. Pressing down will come down one boost group until back to BG1.
Pressing mode repeatedly on the default screen will tell you the current BG, as well as the PHb and other stuff.
Anything with RPM in it (rON or rOFF), or cylinder settings will not be used if there is no tach signal sent to the unit, and should be left at 0. LE1,2 are lighting outputs you probably didn’t buy that option. Additional RPM based, time based, Delay switching or sequential logic is complicated enough you should go ahead and read the instructions.
Hope that is concise enough to be helpful.
Wire it:
The two wires from the solenoid go to the grey and brown wire from the controller, they can be hooked up either way.
Pull out the white wire if you want the controller to turn something on with boost. This will get hooked in as the NEGATIVE on a relay to run the thing (such as a fuel pump).
Find a positive source that is on anytime the car is running. You need your boost controller working in the daytime as well as night when the instrument cluster is lit.
Plumb it:
The standard external configuration works fine 90% of the time. Connect port one of the solenoid to a ‘boost only ahead of throttle body’ area along with the ‘bottom’ wastegate port. I use the fitting at the turbo housing discharge for this. Port 3 gets vented to atmosphere but still put some hose on it to keep water out. Port 1 goes to the ‘top’ or end port of the wastegate. Hook a manifold source to the controller itself (VAC AND BOOST)
Acronyms:
BG = inside each boost group are settings for controlling a particular level of boost.
Extra boost groups are not editable until they are activated.
SP = the target max boost in any separate BG. 0 = wastegate spring pressure, 99= max boost possible with the current solenoid configuration, and turbo/engine configuration. 50 does not mean 50psi boost target. Just set the number to where it needs to be to perfect what you want in a particular group.
GP = gate pressure. The boost controller does not let any boost signal to the wastegate until this pressure is attained. This is for quickest spool time. Too high and you will get overshoot, too low and it will spool as it would without the controller. I stay 3psi or so below SP.
SN = sensitivity. Too low and you will ‘creep’ to max boost, too high and the boost curve will fluctuate after max boost is achieved. 20 is a safe bet.
OBS = overboost shutdown, kills boost if it goes too far. If your car slows down when you turned the boost up, this could be why! Put this @ 2psi over the max boost of your highest SP.
BGR = bar graph (led display under boost display on the gauge)
AL = alarm sounds not very loud at a determined boost point
NSP = how many boost groups you have activated, 1 to 6 possible
AU = Auxiliary output (white wire that goes negative) at a determined boost point
PHb = Recall of the highest boost reached since PHb was last selected
Set up:
Pushing mode and down together gets you to BG, SP, GP, SN
Pushing mode and up together gets you to OBS, BGR, AL, NSP, & AU
Push mode to edit a particular section. Push up or down to increment during editing. Hold mode to save and again to back up.
Push up or down to scroll through functions to find ones you want to edit.
Use Tips:
Every time power is cycled to the controller it will go back to BG1.
While on the live boost (default) screen every time you hit up it will move you into the next boost group depending on how many you have activated. Pressing down will come down one boost group until back to BG1.
Pressing mode repeatedly on the default screen will tell you the current BG, as well as the PHb and other stuff.
Anything with RPM in it (rON or rOFF), or cylinder settings will not be used if there is no tach signal sent to the unit, and should be left at 0. LE1,2 are lighting outputs you probably didn’t buy that option. Additional RPM based, time based, Delay switching or sequential logic is complicated enough you should go ahead and read the instructions.
Hope that is concise enough to be helpful.
08-05-2008, 05:01 PM
#12
GP = gate pressure. The boost controller does not let any boost signal to the wastegate until this pressure is attained. This is for quickest spool time. Too high and you will get overshoot, too low and it will spool as it would without the controller. I stay 3psi or so below SP.
If you have a very fast spooling setup, and especially if you are running on stock parts, you may want to start your GP at 50-60% of your setpoint (target boost) and tweak from there. As of the weekend (last time I drove), my GP was at about 11 and the car would spike to 15.5-16.0 and settle out to 14.5-15.0 right afterward.
Nice writeup Dave.
