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Boosted Saturn FAQ 11-04 by Qksltwo

Tuning Your Turbo Saturn

MANAGEMENT BASICS GAY

Firstly, having the ability to tune your car is the most important aspect of tuning. The
tools that will let you control timing, fuel, and boost are the basis for a good tune.
Management for turbo vehicles tends to be complex, but you almost can’t have too
many aspects of a setup’s function to tune. Yes, some systems are “overly” complex,
but this extended tunability is likely a good thing. So something that is “overly”
complex is likely just a tuner’s lack of ability to tune. All engine management systems,
from your factory Saturn PCM to a full blown Tec III or FAST management system, are
just input/output devices. Considering a certain set of inputs, they use pre-set
calculations and algorithms to develop a certain output. Simple Example: Given a Map
Value of 200kpa, and an RPM value of 4500, “x” amount of fuel required and “y”
amount of timing. Table modifiers are different input values that the management
system will take into consideration that alter the outputs. For example, given an
increase in air temperature of 10 degrees F, timing may be pulled ¼ of one degree and
the VE (or volumetric efficiency) table may be bumped up ½ a percent across the board,
which will add more fuel and compensate for the extra heat and closer to pre-ignition
conditions. The more raw table modifiers the better, to the extent of the tuner’s
capabilities. Some systems may allow you to pull timing or add fuel in relation to
knock. Some systems have user programmable air fuel ratio charts. When the driver
goes full throttle, the management will take note of the difference between the desired
or target air fuel ratio and actual air fuel ratio. By datalogging the difference, the user
can then re-program the raw fuel curve to make the actual air fuel ratio match the
desired air fuel ratio. The factory computer has a certain set of values that it defaults
to under high throttle or high load conditions. It works well, but does not have the
capability to interpret boost. This fundamental limitation means that we must modify or
add auxiliary systems to compensate for the drastically increased airflow that comes
with boost pressure.
I’m not going to go into the different tuning solutions available. They vary greatly,
most of which are untested, and our information on these is changing every day. I don’
t want to put up information that will be outdated shortly. So be that as it may, I’ll give
a general overview to tuning your vehicle assuming that you have the proper tools to
do it. I cannot stress enough how important it is to have a management system that
you can tune thoroughly. While simpler systems will work, it takes much more stress
on the engine to create the same power and usually compromises reliability or
drivability. Considering the amount of money most of us will easily spend on a set of
played out polished lip gunmetal wheels, a solid engine management system IS NOT an
“expensive” modification, by any means! Period, no excuses! I only wish someone had
told me this when I started…

PREPERATION TURD

First thing to do when starting to tune a car is make sure it is mechanically sound.
Spark plugs are probably the most critical thing to check on the initial setup of a turbo
car. Check them often. When I first start a motor with a new setup, I check the plugs
every time I turn the car off, or on. Yes, like every two or three minutes. Start it,
monitor the gauges, listen to the motor, turn it off, check the plugs. Pull the dipstick,
pay close attention to what the oil looks like; are there bubbles of air? What about any
bits of condensation or water based liquid? Closer inspection will show you how much
exhaust crud is getting past your rings. I’m not going to tell you how much there
should be, or attempt to describe such variables. These are things that you will learn
by experience, and by experience only. Sorry, no easy way out on that stuff.
Change your oil often. Heard that before? Well, on this last setup, when starting the
car for the first time with the stand alone, I changed the oil no less than 7 times in the
first week. Why? I was running way rich, and running so rich causes the piston rings
and cylinder walls to be washed with fuel. The fuel replaces the oil, and does not have
any of the lubrication or cooling properties of oil. More turbo saturns blow due to
weakened piston rings due to washed oil rings than anything else. Second reason?
Throw a bunch of fuel in your oil, and have fun with your spun bearings!
Compression. Check your compression. It doesn’t have to be that high, it just has to
be somewhat consistent. 140psi and above is ok. I’ve had 8.5:1 motor test anywhere
between 135psi/cyl up to 190psi/cyl. It will vary, depending on the head
gasket/valves/piston manufacturer.
The head. Our lifters like to go bad, and most of the time we don’t even know it. My
guess is about half of us have stuck lifters. Pull the cams off, and take out your lifters.
Do they squish? They should move. A lot of times they don’t. There is no good way to
see if they are getting too pumped up or bleeding down too much, but a set of lifters
with minimal wear in the lifter bores and a “squishable” hydraulic center is important.
Much of the intermittent head clatter that sounds like a valve attempting to beat the
sh1t out of itself is lifter noise. You can pretty clearly hear that it repeats itself at twice
the speed of the crank.
The Block: Please let your engine get up to temperature before you hammer on it.
Forged engines take a few minutes of idling and a couple minutes of driving before
things start to seal up. You can watch your vacuum get stronger as the rings start to
seal up and everything expands to the correct tolerances. This is important to the life
of the motor. For those of us exploring the upper limits of our motors’ RPM capabilities,
ditch your ARP main studs. Build your block with your mains align-bored by your
machine shop, do not hot tank your block, and use a 2000 and newer lower girdle along
with 2000+ main studbolts. When you do this conversion, there are small key screws
that thread into the girdle itself to take up the room between the girdle and the stud.
Make sure to use the factory pieces for this! When you go order your parts from the
dealer, you’ll see what I mean. Locktite the nuts that hold down the girdle, as well.
Use clevite Tri-Metal bearings and plastigauge everything.
One common fallacy is that low oil pressure is due to extra turbo oil lines/oil cooler. As
long as you fill your oil pan to compensate for the extra volume needed for those parts,
your oil pressure will not be any lower. One common reason for low oil pressure among
turbo applications stems from a bad tune, and overly rich conditions. This allows fuel
into the oil, which thins it and ruins its ability to be a barrier lubricant. It also dries out
the cylinder walls and allows you to wash out your rings.

MONITORING YOUR BALLS
Here, I will attempt to somewhat briefly explain what you should be monitoring. You can’
t tune blindly, and you, just like your management system, are an input/output device.
This time, your car is the input, you see what it is doing, and you generate and output to
make the car do what you want it to do. Your inputs are what the car does, and you
monitor these things through three key ways: Air fuel ratio, EGT, and knock. Other
inputs are the sound, smell, feel, and driving characteristics of the motor. The gauges
you need to have are a wideband A/F ratio gauge and an EGT gauge. A knock sensor
readout is a very good idea as well, and nearly all other highly tuned turbo cars (think
DSM and supra) use knock readouts as a way to tune. Your wideband is to your fuel
tuning as your EGT gauge is to your timing tables. Your knock is an umbrella, which is
affected by both. That’s not to say that a hot EGT reading means you are running too
little timing, or visa versa. Unfortunately, it isn’t that simple.

IGNITING MAH ASS
Boost makes cylinder pressure. Cylinder pressure makes the piston move. The piston
moving makes torque. Torque makes power. Boost makes power. Fuel is just there to
allow there to be a controlled ignition of the charge (air read: boost) and spark just sets
things off before they set off on their own. Oversimplified? Horribly. True? For the most
part. So if boost is what makes power, what does timing do? Traditionally, it is thought
that 17 degrees past TDC (top dead center) is where you want peak cylinder pressure to
be. You have the most “leverage” to do maximum work with limited energy (read: intake
charge). With a steady burn rate of a naturally aspirated motor, most old almost dead
dudes have figured out that about 35 degrees of advance gets peak cylinder pressures
around 17 degrees past TDC. Let me try to explain this so more people will understand:
You want maximum “kaboom!” when the piston is 17 degrees past TDC. There, the
piston is in the part of its stroke where it will make most efficient use of the pressure in
the combustion chamber. Here, I won’t explain why this is, so just believe me or I’ll ban
your jap ass. So to get maximum “kaboom” at 17 degrees past TDS, or ATDC (after top
dead center), it is conventionally thought that 35 degrees of timing advance is best. That
means that the spark happens at 35 before… and by the time that the maximum
pressure from the expanding “kaboom” happens, the piston is at 17ATDC. Got it? The
flame front speed and maximum pressure along with the combustion chamber shape, fuel
octane, and other factors will determine how long it takes after the spark for maximum
cylinder pressure to happen, so how much advance is needed to make maximum
pressure occur at 17ATDC will vary depending on conditions. When we add forced
induction into the mix, pressures will vary, and the spark advance for peak performance
efficiency will vary wildly as well.
Of course, this is all very general engine workings… and mostly applies to V8’s non v-tak
MDM (Mexican domestic market, we don’t’ make most yank cars in the United States Of W’
s Ass any more). So be that as it may, what does this mean to us? Well, this basically
doesn’t apply. Why did I explain it to you in simple terms, then? Because you need to
understand that before you can attempt to understand how to set timing for our cars.
Most small displacement high boo…. Wait, let me say this, first. Given each and every
setup, there is a maximum allowable cylinder pressure (most heavily determined by the
map or load/boost value) that a certain cylinder can take at a certain RPM before pre-
ignition. Pre ignition just being that the mixture or intake charge “kabooms!” before it is
supposed to. Don’t know what that is, look it up. Think pink, knock, or detonation. So
there is a certain amount of pressure that the cylinder can take before it prematurely
“kabooms!”. Recall that the idealized 35 degrees of advance also gets us maximum
efficiency for each “kaboom!”. So combine maximum cylinder pressure with maximum
efficiency and you get mad 3rd gear v-tak power, right? Yes, in a perfect world.
However, we’ll never get to that point. Not in my yellow life, anyway. Small displacement
high boost cars will knock before you get to 35 degrees of advance under boost.
Generalization? Yes. So sue me, ACLU. Reality though, seriously. Point is, we’d make a
lot of power by running 35 degrees of advance and boost, but it’s unlikely our cars can
even run 35 degrees of advance with no boost on pump gas. Throw in a whole crap load
of potential energy that is boost and you have a “kaboom” that’d make Hiroshima jealous.
So what do we do? We run as much advance as we can without things going “kaboom!”
before they are supposed to. That means we get peak cylinder pressures as close to 17
degrees ATDC as possible. The effect on the power output of a motor with small timing
changes is huge, as you can imagine. As you move peak cylinder pressures closer to
optimal range, you can increase your power immensely. In fact, dropping the boost and
increasing timing is probably most overlooked way of picking up horsepower there is.
You run less peak dynamic pressures and lower your EGT’s, while picking up horsepower,
dropping your BSFC (look it up), and running a cleaner combustion process. Too good to
be true? It’s not, its just not experimented with, much. That’s how we have hugely
overboosted turbo 4 cylinders making some pretty pathetic numbers.
Setting timing. Saturns seem to like around 15 degrees at idle. Drop the idle down to
800rpm or so from 1000 and they like about 13. You can time an engine at varying RPM’s
by listening closely to the sound. It is very hard to describe, and is something that you’ll
learn with experience. When timing is too retarded, it will sound softer, with slower,
longer exhaust pulses and a “rounded” tone. The gaps between each exhaust pulse will
be longer, and it will sound lopier, or more like it has a hot cam. At the exact same RPM,
the correct timing will sound smoother, and the engine will shake less on its mounts. The
tone between each cylinder firing will change less. When you add too much timing, you’ll
hear a sharper “crack” for each firing. When you tip into the throttle, it will try to respond
quickly but misfire because the VE of the motor cannot keep up with the spark, in layman’
s terms. You want timing to slowly ramp up until the engine “clears its throat”. There,
you want to carry maximum timing until your start building significant boost, where you’ll
be forced to start backing off timing. Where you get maximum boost and torque lowest
in the RPM band, you’ll want to be most conservative with timing. As torque starts to
drop off and cylinder pressures die down due to pumping losses at high RPM (read:
restriction), you can usually add more timing. If you have you’re a/f set pretty
conservative and you are getting high EGT’s, your first step will be to drop the boost until
EGT’s come down to a reasonably level. Now, at that same boost level, advance the
timing while watching knock carefully, and ensure that you have not altered the a/f ratio
by changing the boost. Watch carefully; if there is a reduction in EGT temps by adding
timing, then you had taken out too much timing.
I’m not going to go into how exactly to set your timing, or what to set it at. Why?
Because that is for you to figure out, for your car. I have a good idea of what a timing
map for your car should probably look like. But refer to Psychological Tewning for a
discussion on why, exactly, I’m not going to tell you. All I can say is to start with the
boost low, and do everything only one step at a time. You’ll learn, but only by
experience. Think of each response you make in a rational sense: by making only one
change at a time and reviewing what that change resulted in, you’ll in no time have a
good map setup.
On the dyno. Set up your timing map conservatively, at first. Start at low boost, and get
your raw fuel work done. Pay careful attention to spool up and peak torque, and also
make sure to make runs in third and fourth gear. Why? Make sure that the changes in
load by different gear ratios and the time over load differences don’t’ exceed your fuel
delivery and heat things up. You’ll see this by high EGT’s at the top of a long pull. This is
a situation where A/F might be just fine, and you won’t even see knock, but your EGT’s
will be high and you can absolutely blow your motor. “But my a/f was fine and there was
no knock!??” I can hear it now…
If your knock resistance threshold is high enough, there won’t be any detectible knock,
but the high cylinder pressures and combustion temperatures held over a long period of
time can and will destroy your motor. Got it? Typically this is a condition you will face
using race gas, and that is why race gas is dangerous. A sense of false security lol
asscroft lol is really the problem. This is the most likely cause of failure for DSM’s, as they
have a great closed loop knock/timing circuit, but the motor cannot save itself from high
EGT’s.
Our cars seem to respond very well to a good bit of timing under boost. This has been
recently illustrated by Chris (tebriel) who just put down 311whp at 17psi on a fifty trim
turbo with no timing control whatsoever. Is timing control important? Very. How did he
do it? Good fuel tuning. Was it safe? Well, we really don’t’ know. It seemed to work
and still is, but without ignition tuning, a bad tank of gas or changed airflow by different
parts could mean the end of that motor in a short time. Despite this, running 25 degrees
of maximum timing is what held his motor together. EGT’s remained low due to the
strong timing. I’ve tuned cars before on the dyno where we’d pick up 30 plus lb/ft of
torque by just a single degree of timing. What does this mean? It means drop the boost
and add another degree, see what that does. Keep adding timing and watch your EGT’s
drop. When they level off, you’ve gone far enough. However, as you’re adding timing,
you need to watch knock very closely. See above as to why.

I’VE GOT A GAS PROBLEM, DOC
Fuel. Your narrowband is useless. A tenth of a volt can mean a full point in a/f change,
and that is not something you want to risk your motor on. Under boost, your target air
fuel ratio is 11.4 to 11.6. Again, this is pretty general, and your results may vary, but this
is considered “safe” under most conditions. If you are getting knock, resist the urge to
just dump more fuel, assuming you’re a/f ratio is already within this range, and try to
adjust timing first. Generally speaking, you are going to want your enrichments set to
where you’re a/f first dives down to a 11.0 or so for a period of .25 to .5 of a second. That
will quell any initial tip in knock and clear the fuel line. Once your initial enrichments time
out, you’ll want to have you’re a/f around 12.0 to 12.5 until boost builds. As boost builds,
you want to offset your fuel table. This means you initialize your fuel table to dump fuel
before you actually make the boost. Example: If you want the a/f to dive as boost
crosses 10psi, which comes on at 3800, go to the 10psi at 3600 table and make your
change there. You’re a/f ratio as you approach peak torque is most important, after that it
can flatten out. I typically like to dump fuel right before rev limit as well… but that is just
my style. It makes a zero advance rev limiter a bit easier on the motor.
The sound and feel of a rich or lean condition is remarkably similar, yet different. Bucking
under partial throttle is usually lean, but not always. Just with boosted saturns it is
usually due to leanness. Low RPM bucking on a stand a lone is due to the enrichments
working well for higher RPM but not compensating for the poor VE values at low RPM, and
attempting to add the same amount of extra fuel despite that. A rich misfire will sound
soft, and muted. It is almost hollow and low in tone, as one cylinder or two will misfire at
a time. As you rev the motor, it will sound like a WRX, which is, essentially, like two two
cylinders. The other time a Saturn sounds like WRX is when it has a blown motor. Don’t
ask me how I know. A lean condition will sound like a hard crack and snap as you attempt
to rev it. You will also likely hear the turbo try to spool… good but not. You’ll want to add
more TPS enrichment if you hear this.

FINAL WERDS
Basically, this whole tuning thing is a game. You change fuel, EGT’s go up. You add
timing, EGT’s drop but knock goes up. You add fuel to compensate and knock goes away
but power goes down. You bump boost, things get better, but now you are running a lot
of pressure. You drop boost and keep your fuel the same, kinda rich. Bump timing, and
holy Mexican I just picked up 38 lb/ft of torque with no knock!
All I’m saying is that there are so many variables. Some tuners call it the “Best Mean
Torque”. That is; the combination of enrichment by fuel and timing that produces
maximum power with equal “compromising” from both sides. It’s not an easy balance to
find, and you won’t necessarily know when you’ve found it. At that, its kinda like trying to
hit a moving target lol dinner sweet and sour dog lol. With the turbo 4cyl world, you’ll
want to lean towards RBT, which means Rich Best Torque. That is, you’ll sacrifice some
advance and leanness to run a safer condition. Again, it’s a balance, and there is no
“right” answer to this. Under partial throttle, you’ll want to lean (pun) more towards LBT,
or lean best torque. Under low Map values, you can run more timing and less fuel while
being ok, due to lower dynamic pressures.
I haven’t even really touched on part throttle and light throttle conditions. This is
probably the hardest part, and should be dedicated the MOST time of all. You’ll be able to
get a reasonable and safe high load chart put together pretty quickly. You’ll know that
you have a good setup when you’re a/f ratio is in the mid elevens, you are below the
knock threshold, and your EGT’s are safe. If you do a first through fourth pull, you want to
see roughly 1450 degrees F tops at the end of fourth gear. As I mentioned earlier, I like
to add 7 to 8% more fuel at the very top of the RPM band. In the lower gears, you
accelerate through them so fast that you won’t notice the deadened couple hundred RPM.
In the longer gears, this will help keep EGT’s down at the top of a long pull.
A word on corrections: Many of us don’t pay enough attention to correction factors. This
is pressure and temperature. Don’t tune for just once certain boost level. The
interpolation of engine management systems have proven over and over again that
theoretical map values do not work! SAE states that given a certain MAP number at a
certain RPM, 50 percent of that value at the same RPM has 50% of the required fuel. This
is theoretically correct, however, it does not take into consideration the variable pumping
losses and efficiency of compressors/heads/cams at such variances. Temperature is the
other variable, and every setup will require a different amount of change per degree of
temperature variation.
Transitions are the key to drivability. That means setting your RPM points to reflect
transitions in VE throughout an engine’s RPM range. You wont’ be able to do this until you
drive it. Once you have these set, try to make all changes as gradual as possible. You’ll
want the lowest enrichment values possible to ensure that your raw fuel curve can take
care of the engine function as a whole. You don’t want you’re a/f to change rapidly as
boost comes up. Some tuners will run 14:1 a/f until several pounds of boost and then
drop it like it’s hot to 12:0. This attempt to help “spool up” just gets you closer to a knock
threshold and can even go as far as to increase your EGT’s at higher rpm, as you are now
starting with a higher base EGT.
Also, your VE’s will change much more slowly under vacuum and partial throttle than
under boost. Once you are under boost, small changes in VE mean big changes in airflow,
and more drastic changes will be necessary.
Tune safe. You might lose 7-8whp on a 300whp setup going from 12.5 down to 11.8 a/f.
Worth it? Heck yeah. You are closer to RBT, and your running cooler. You might actually
pick up power by pulling timing, if you are running too much. Advance 1 degree, pick up 30
lb/ft. Advance another, pick up 12. Advance another, pick up 3 lb/ft but knock goes up.
Pull timing 1.5 degrees. Another senario: Making 300whp 22 degrees maximum timing.
Knock is kinda high. Pull a degree. 313whp at 21 degrees maximum timing and knock just
went down. Why? You had single cycle misfires due to pre-ignition. Pulling timing across
the board made each and every combustion process work, instead of some working very
well and others being beyond their limits. Watch cyl number 4!
Well, I have a lot more to go into about the dynamics of a combustion cycle, but its 1:
00am and I have work and school tomorrow, so that’s it for now guys. I bet there is some
seriously shittay grammar and spelling in the above article, but I don’t’ feel like reading
the whole 8 pages over again. I kinda just wrote whatever came to my head, so I know it
isn’t organized as well as it should be, but I will update it more in the future. Stay tuned,
and I really hope this helps! Don’t understand some of the terms, like VE or MAP?
Search!!!! -Ian