|
Article originally posted on
automotiveforums.com
I’m going to try and cover some of the most
popular and effective methods of ignition and fuel control for forced
induction motors, but please understand there is a huge diversity in
products out there and I might miss some of them. Also, I should say
now that I won’t be talking about carbureted setups, since I honestly
don’t have enough experience with them to pass on any knowledge. So
without further delay, let’s just jump right into it…
IGNITION SYSTEM
The all important air/fuel ratio has a big impact on how strong the
ignition system needs to be to ignite the mixture. For ignition to
most easily occur, the a/f ratio needs to be right about 11:1, with
anything richer or leaner quickly causing minimum voltage needed for
ignition to increase (and sometimes dramatically). Yet optimal power
production in FI motors will occur between 12:1- 13.5:1 a/f ratio (on
most engines), so already we are asking the ignition system to do a
tough job. In addition, the more densely packed the combustion chamber
is, the harder it becomes to ignite the mixture. So for the average
forced induction motor, the ignition system needs to be very solid
system to reliably get the job done.
Spark Plugs
Which spark plugs you choose is completely up to you, just make sure
you don’t buy too much into the idea that a specially grooved tip or
electrode shape is really going to make a difference in performance.
The only important thing to mention here is in regards to plug heat
range, and the fact that you should probably go with a plug 1 to 2
heat ranges colder than stock for forced induction use. Since there
are so many different engines and forced induction systems out there,
I recommend you speak with a knowledgeable tuner (of your car) to find
out what heat range and plug will work reliably. But as a general rule
of thumb, one heat range colder is about the average in my experience.
On heat ranges: in case you are not familiar with this term, it refers
to how easily the plug can transfer the heat absorbed from combustion
to the cylinder head. Hotter plugs either have thinner porcelain
jackets around the electrode, longer porcelain jackets, or both (when
compared to a colder plug of the same manufacturer). The thinner the
porcelain is, the less heat it can absorb and so the less heat it can
transfer from the electrode tip to the metal body of the plug, and
likewise, the longer it is the harder it becomes for heat to transfer
from the tip to the body. The more power you make from a given size
engine, the more heat you are creating from combustion, which means
that the plug is exposed to greater temperatures during engine
operation. The different heat ranges allow you to keep the spark
plug’s tip at the proper temperature for reliable operation; too much
heat and it wears excessively (and can cause pre-ignition), to little
and deposits will form that eventually prevent the plug from creating
a spark. So know that as you increase the heat of combustion, you must
move to progressively colder plugs to keep the plug tip at the right
operating temperature. More information can be given later on how to
know when a colder/hotter plug is needed.
Ignition Coil
http://www.msdignition.com/1msdcoil.htm
The coil is probably the most important thing to upgrade when it comes
to forced induction performance, because of the additional voltage
needed to jump a spark in a high pressure, high temperature combustion
chamber. MSD is an excellent maker of coils, but again, choose any you
like that fit your budget and taste. Also, in the case of external
coil ignitions (one where the coil is located away from the
distributor body), make sure you choose a coil that can be mounted
very close to the distributor. This is for best performance and lowest
resultant RF interference, so simply remember to keep the coil lead as
short as possible.
Also, when upgrading to significantly more power coils than stock,
it’s usually a good idea to upgrade plug and coil lead wires too. The
extra voltage they will be carrying, as well as the additional heat
the boots will be subjected to (this is mostly in reference domestic
V8 motors), will warrant a purchase in this area. Choose whichever
name brand manufacturer best fits your budget and taste, just make
sure they are well shielded and have, if possible, boots specifically
designed for high heat environments. Porcelain boots are best in my
opinion, but not necessary. Thicker wires generally have more
insulation and not thicker wire, which is exactly what we are looking
for. If you can get some 8.5mm wires, do so, if you can get 10mm wires
that fit everything fine (including your budget), why the hell not?
Basic Ignition Controllers
MSD
By far the most widely accepted and popular controllers are the MSD 6
family (which currently includes the 6A, 6T, 6AL, and 6BTM), and this
is for good reason. MSD stands for Multiple Spark Discharge, an
ingenious idea that helps ensure combustion through sending multiple
sparks to each plug at the outset of every power stroke. Again a good
coil is recommended with any system like this, since coil soak time
(the time it takes for the coil to build up a full charge) can limit
the ability of multiple spark technology to work well in a stock
system. Good aftermarket coils generally have shorter soak times than
stock coils.
Of particular interest to the forced induction crowd, the 6BTM
controller allows for boost dependent ignition retard as well as
multiple spark discharge. Without going into depth here, let’s just
say that boost dependent ignition timing retard is one of the best
ideas for ignition controllers EVER, and that almost any forced
induction motor can benefit from it, especially if the ECU wasn’t
tuned for forced induction use from the factory. A 6BTM additionally
has a control knob so you can set the amount of ignition retard
induced per pound of boost, where the user can select anywhere from
0-3 degrees of retard per pound of boost. Of note: the 0 setting
allows you to prevent any ignition retard during boost, meaning that
(among other things), this controller can be purchased and installed
before the s/c or turbo is installed. So if anyone is looking for an
ignition controller and is also planning on forced induction, this
might be the one for you.
Check
http://www.msdignition.com/1ignstre.htm for more details.
J&S
While MSD has taken the pro-active approach to ignition control in the
way of their BTM units, J&S’s basic controller covers the reactive
side of the equation. The J&S Safeguard uses a knock sensor (standard
on most late model ECU equipped cars) to “listen” for detonation, and
if it senses any, retards the timing in an effort to prevent engine
damage. The J&S units are very fast and sophisticated, and can even
retard timing on a per cylinder basis if you so choose. J&S
Safeguards, for their modest asking price of $450-500 dollars, should
be considered the best insurance policy for your engine money can buy,
and for a small extra outlay in cash, will show you if and when they
are pulling out timing. In essence, a J&S unit is a tuning tool and
insurance policy all-in-one, not a bad investment for less than the
cost of pistons alone.
The new kid on the block from J&S is their Ultra Safeguard, combining
boost dependent ignition retard with the welcome insurance the
standard Safeguard supplies. Although these units don’t offer the
multiple spark discharge of a 6BTM, in my opinion they offer the
absolute best setup when it comes to a single purchase system for
forced induction motors. You can essentially tune the J&S with itself;
upon seeing that the unit is pulling out timing under boost, you can
alter the retard amount to tune out detonation. And with their dual
monitor gauge, you can even see the a/f ratio the engine is running at
the time of detonation, allowing you to most accurately pinpoint the
cause of the problem. What other product costing less than $600 can
you make that claim with?
Check
http://safeguard.20m.com/ for more details.
FUEL SYSTEM
Yes, the all important fuel system. Nothing is quite as basic as this
when it comes to engine performance, and yet sometimes nothing is more
blatantly overlooked. There are 4 principle ways to increase the fuel
supply to the motor…
Fuel Injectors
There are two common types of fuel injectors, pintle and disc (Lucas
style). Pintle injectors have a superior spray pattern to disc
actuated injectors, but disc injectors are less expensive and
generally flow large amounts of fuel easily. If possible, always
choose high flow pintle style injectors, as fuel atomization at
anything other than full throttle (high velocity port flow) is
superior, leading to better drivability and economy. Below is a
picture illustrating what I mean about the spray patterns…
So when do you upgrade to larger fuel injectors? The general rule of
thumb is that anytime the injector duty cycle goes beyond 80% (meaning
the injector is open and firing over 80% of the time), you should
upgrade. Fuel injector performance can become unstable beyond this
point according to some experts, plus it doesn’t pay to have a proper
sequential fuel injection system working as a simple always open spray
nozzle (which is neither efficient or powerful). Of course upgrading
their size is only one way to add more fuel, and although a very good
idea, it works best on car’s that can be easily retuned to work with
them. In the case of MAF cars (Mass Air Flow sensor), system
recalibration is generally just a matter of changing the sensor (many
of the available larger sensors offer multiple calibrations). For
speed density fuel injection systems (the other type of airflow
sensing), its generally necessary to have an ECU capable of
recalibrating it’s fuel tables for different injector flow rates. This
is a problem mainly for the Honda people out there (all of which come
with speed density systems), in which case you should think seriously
about giving Zdyne or Hondata a call. Both offer very nice
programmable ECU systems capable of keeping a big time forced
induction motor running reliably and strong. Or, you can read on and
see a few other ways to increase fuel flow without changing injector
size.
Fuel Pressure Regulators (FPR’s)
All fuel injected motors have high line pressures when compared to the
older carburetor technology, generally somewhere in the area of 25-40
psi. Changes to the line pressure will have a direct effect on total
fuel flow from the injectors, but it’s important to realize this
pressure vs. flow relationship is NOT linear. By one estimate I have
read, to double fuel flow through an injector you must quadruple the
line pressure. However most fuel systems will not tolerate more than
60-100 psi of pressure (even with upgraded fuel pumps; more on this in
a moment), so just know that changing fuel pressure works great until
you need to add anything over about 50% more fuel, at which point you
need to do something else besides simple line pressure changes.
Most aftermarket fuel pressure regulators are simply adjustable with a
screw (where you will need a fuel pressure gauge to know how much
you’ve changed things), and are very easy to install. However in the
case of forced induction motors, what you need is not the simple
adjustable regulator. You need to find a rising rate FPR that can vary
fuel pressure according to boost levels, and most people consider
Cartech’s 2005 the best one available. It has a variable gain rate and
the ability to start increasing pressure before the onset of positive
manifold pressure (it senses that intake pressures are quickly rising
and anticipates the soon to come need for extra fuel), a big plus for
positive displacement supercharger applications, which can go from
full manifold vacuum to full boost in less than a second. These are
very useful tuning tools even if you happen to have larger injectors
or other methods of fuel control available, so don’t count them out
from any forced induction system. Check out
http://www.cartech.net/fuelaccessories.html for more info on the
2005 unit.
Fuel Pump
There are two common choices to what fuel pump setup you can choose to
run, internal and external pumps. Internal (the pump is located in the
fuel tank) pumps are quieter and sometimes easier to install than
external pumps, being that they are more like factory replacements
than add-ons. External pumps (which are located somewhere on the fuel
line, usually as close to the tank as possible) usually offer the
highest flow potential, but they can be annoyingly loud a loud buzz
emanating from somewhere under the car). Additionally, there are two
things to remember when talking about pump choice and placement.
First, pumps like to push fuel, not pull it, so always mount the pump
as close to the fuel supply as possible. Second, fuel pump flow drops
as fuel line pressure increases, and this is again not linear. Pumps
are judged not only by how much fuel they can ultimately flow (called
LPH or GPH, being Liters Per Hour and Gallons Per Hour, respectively),
but also by how much fuel they can flow at given line pressures.
Ideally, the pump to look for is an in-tank unit that has high flow
ability at high pressures (Walbro and Bosch are the primary
manufacturers). These pumps will offer quiet and stable performance
for virtually any setup, including ones using rising rate FPR’s to
jack fuel pressure up as airflow increases. It’s also somewhat
important to know that you shouldn’t just buy the biggest pump you can
find, go for the one that best fits your needs. Very large pumps can
cause capitation, and can also (in the extreme) overpower the return
lines from the regulator and potentially cause fuel leaks or overly
high line pressures. If an external pump is the best choice for you
(where a very high flow ability is needed and you aren’t too concerned
about noise), look to Vortech and Cartech for your pump.
Fuel Controllers
Fuel controllers (I use this term to describe any electronic
controller designed specifically for fuel tuning) come in a few
different forms, some modifying ECU input data, and most modifying ECU
output data. Every one’s purpose is to somehow manipulate injector
pulse width to tailor fuel delivery, and they work very well to that
end for WOT (Wide Open Throttle) tuning. What they offer is the
ability to ultimately control injector duty cycle, and hence the
ability to easily tune fuel delivery for maximum performance.
The only problem with fuel controllers is there usual lack of ability
to be tuned for anything other than WOT engine operation, but since we
like to keep the go pedal on the floor, this usually isn’t much of a
problem J. Fuel controllers let us tune the fuel delivery curve with
precision FPR’s can only dream of, and in most applications they work
so well that even solidly tuned combos will see power and mileage
gains through their use. These relatively new inventions basically
“piggy back” standard ECU tuning, letting the ECU do the fuel delivery
work until full throttle is called upon, where they step in to modify
ECU signal (in the case of controllers that modify ECU output data) or
modify the airflow signal (in the case of controllers that “lie” to
the ECU to get the desired fuel delivery from it) to let us modify
fuel delivery. This is a very good idea because all that time spent
tuning the stock ECU to work perfectly at idle and most throttle
openings and RPM (other than WOT) is left intact, with our tuning only
taking effect when things really start to stretch whatever setups the
factory had in mind. All can offer fuel delivery tuning accurate
enough for serious performance applications, and all can be very cost
effective when compared to complete engine management systems. Which
brings me to my final point…
COMPLETE ENGINE MANAGEMENT SOLUTIONS
There’s really not much to say here, since you either have a radical
enough setup to know why you want this, or are not in great need of
one in the first place. The complete and tunable ECU solutions cover a
large range in price and features, but don’t expect to see anything
for less than around $900 (without installation or tuning costs). All
attempt to get rid of as many limitations to tuning in the stock
system as possible, and all need to be professionally setup to work
properly. And please take that advice seriously, as the thing about
removing limitations to tuning is also that you remove many safeguards
in the system, so it’s a lot easier to break things than before
without proper tuning.
Having said that, nothing is as powerful as a forced induction motor
running solid custom engine management. Race ready Motec M4 setups
with tuning can cost well over $5000, but will reward with the best
possible power and reliability from the motor. For a look at the
products currently available, check these sites…
EFI Systems PMS:
http://www.efisystems.com/
Motec:
http://www.motec.com/home.htm
Haltec:
http://www.haltech.com.au/
Electromotive TEC II:
http://www.electromotive-inc.com/home.htm
Hondata:
http://www.hondata.com/
Zdyne:
http://www.zdyne.com/
MSD Digital 7:
http://www.msdignition.com/
Accel DFI:
http://www.mrgasket.com/accel.htm
|
