Aftermarket engine management and injectors

[benjamin]

In the near future I will be looking at getting aftermarket engine management and therefore will need to decide whether to use high or low impedance injectors. Does one type have any benefit over the other?

It seems that the injectors with super high flow rates (ie 1000cc) are all low impedance.

The flow range of the injectors I would most likely go for (500-550cc) are available in both low and high impedance. I have looked at wiring diagrams for programmable computers and it looks like they just put a resistor in line with low imp. injectors.

Anyway I just thought this might be an interesting topic? And maybe help me decide which way to go...

[mrshin]

If you've got an ECU that can properly control peak+hold current, low impedance injectors are the way to go, especially in the bigger sizes, provided you have enough injector channels to manage the current flow. With any semi-decent ECU with 4, 6 or 8 cylinder engines, this shouldn't be too much of a problem, however finding an ECU that'll run 12 low impedance injectors is rather hard!

[limbo]

Also i hope you've though of the fuel pump to run such large flows.
BOth ECU & injectors are not going to be able to be sustained with out more fuel pressure. At those levels an adjustable fuel regulator would also be of help.

[Cameron_Datto]

Impedance
Injector impedance describes the electrical resistance of the solenoid windings. These are usually grouped in two categories:
Low- 1.7 to 3.0 ohms (Peak and Hold Driver/Injectors) High- 10 to 16 ohms (Saturated Circuit Drivers/Injectors)
These type of injectors and drivers may also be called current sensing or current limiting. They are more expensive and complex than saturated circuit drivers, and are not generally used with domestic production ECUs. They are primarily used in aftermarket high performance systems. Most high flow injectors are low resistance (2-5 ohms) and use a peak and hold driver to activate them. The Peak current is the amount required to quickly jolt the injector open, and then the lower Hold current rating is used to keep it open for as long as the ECU commands. These require the extra kick from the higher current to keep the opening and closing time of the injector stable at the higher fuel flow rate. With this type of driver, 12 volts is still delivered to the injector, but due to the its low resistance, the current in the driver circuit is high. How high? Using Ohms’s Law we can calculate the current rating (12v/2 ohms = 6 amps). This is substantial current flow and a Saturated Injector cannot handle it. The drivers also come in two values; 4 amp peak/1 amp hold, and 2 amp peak/0.5 amp hold.. Even though 6 amps may be available to operate the injector, the maximum it is allowed to reach is 2 or 4 amps, depending on the driver’s current limit. Most domestic OE production EFI systems use an ECU with 12 volt Saturated Circuit drivers. These are very inexpensive, simple, and reliable. This type of driver works by supplying 12 volts to the injectors and the ECU turns it on and off to establish a fuel injector pulse. In general, if an injector has a high resistance specification (12-16 ohms) the ECU uses a 12 volt saturated circuit driver to control it. This means that the current flow in the driver and injector circuit stays low keeping the components nice and cool for long life. Conversely, a downfall of a Saturated Circuit driver is that it has a slower response time (and closing time) than a peak and hold type. This slower time can somewhat decrease the usable operating range of the injector energized by this driver. An injector operating on a saturated circuit driver typically has a reaction time of 2 milliseconds while a peak and hold driver typically responds in 1.5 ms.
There are some exceptions to this, notably the Bosch 803 injector used on the Porsche 944 turbo which is 4.7 ohms. Most manufacturers have used both types at one time or another. The trend lately is to use high impedance types in most production cars. The best way to determine impedance is to put a digital ohmmeter across the two electrical connections and see what it reads. The primary advantage of low impedance injectors is a shorter triggering time. When large injectors are fitted to high output engines, low impedance injectors will often give a better idle quality because of this fact. The primary advantage of high impedance injectors is the fact that less heat is generated in the drive circuit and often no external resistors

[Cameron_Datto]

This is Also a good site to look at
http://www.injec.com/techdata/tag-In...cteristics.pdf

[Cameron_Datto]

General Fuel Injection Information: Tony Garcia

Got this from an article on "Need for Speed" off the net.

Please let me shed some light on the injector subject also, or should I say, let me turn on the
lights for you. Injectors do in fact come with different internal resistance. (Impedance). High
resistance, called "Saturated", and low resistance, called "Peak and Hold", are the two types
commonly used today. At this time, - 90% - of all automobiles, including the Japanese, are
using Saturated - 12 to 16 Ohm Injectors. Toyota uses Sat. injectors in all but the Turbo
Models. Earlier models used a mix of the two. The, electro-magnetic solenoid, fuel injectors
used in all automobiles today are all grandchildren of the Bendix company. Bendix is a
subsidiary of the Chrysler Corp. and was the founder of the electronic fuel injection system
that we use today. It was called "The Electrojector" System and it was vacuum tube
operated. Patent rights were reportedly sold to Bosch in the late fifties. An interesting bit of
trivia.

Injectors come in many different shapes and sizes also, -hose end, top/rail feed with both,
American and Japanese size "o" rings, galley/side feed -and dual hose feed. Injectors are also
manufactured with many different wire clip configurations, Type C,D(2types),E,F, 10 and an
ever increasing number of Specialty Types. Toyota uses (c, d,e,f) to differentiate between P&H
and Sat. Units. This is to prevent mix-ups in the service dept. Type C & E are P&H and Type
D&F are Sat. Many of these injectors look exactly alike except for part #s. Three types of
top "O" rings are used and a multitude of lower cushions are in use. When changing injectors
all of these problems must be addressed. Injectors should always be tested with a volt/ohm
meter before using to determine type. Be careful, Injector types should never be mixed. Sat.
Injectors can be used in P&H systems, but not the other way around. More on this later.

Tomco does not make injectors, they sell Rochester, Lucas and Nippon-Denso brand, to
name a few. The only injectors that they sell with plastic caps are Nippon -Denso - Many
early Toyotas used plastic pintle caps, along with most of the other Japanese cars in
existence today. Bosch also uses plastic on 95% of its models. Lucas, no plastic pintle caps
at all. NOTE: all injectors use a molded plastic top. The Tomco part # for the 7M-GTE Injector
is 15530 and guess what, -- its a Toyota/ OEM Nippon Denso, Made in Japan, injector.

SIZE / RATINGS ---- ALL INJECTOR MANUFACTURES USE CC PER./MIN. OR LBS.
PER/HR. TO RATE AND CATALOGUE THEIR PARTS. ---{CC /MIN. DIVIDED BY 10.50 =
LBS. PER/HR.} This is the commonly used formula for pump gasoline, using a specific gravity
of .73-. 74 and differs when temperature change and viscosity of the medium is altered. Let
me repeat, ALL manufacturers use the same basic method of sizing, regardless of Country of
Origin, cc/Min. or Lbs./Hr.

Professional Racers always order injectors by the Static flow rate, (wide open) and will state
System Pressure used.- (720cc @ 51 PSI) -- They calculate Brake Specific Fuel Consumption
first and then use this formula. (HP req. Per cylinder - X - B.S.F.C.) / Duty Cycle = Static
injector flow rate required. ----- (100 HP per. cyl.) X (B.S.F.C. of .55 lbs. fuel/HP /Hr) = (55
lbs./Hr or 577cc /Min) -divided by -.80 - (Duty Cycle) = 721cc /Min. This will be the required
flow rate if running at @ 80% Duty Cycle. This formula provides you with the required amount
of fuel that each injector, at wide open, (100% Duty Cycle) will have to supply in order to
support the target horsepower. System pressure used will determine the actual injector
needed. This number only indicates the amount of fuel required, not the injector size. Some
Drag Race cars, do in fact, run at 100% Duty Cycle. This is not an encouraged practice. A
larger than necessary injector run at 70% duty cycle, will provide more controllable
performance than an injector that is being pushed to 90%-95% limits.

TEST EQUIPMENT The available Injector testing equipment, on the market today consists of
The New Age and the ASNU machines. Both of these machines are fine products and they
perform as advertised. These units are designed with a capacity (Measuring device) of 100-cc
per-tube, and only 90% of this is usable for testing. What this means is that these machines
will only measure 90 cc /Min at full flow. At 80% Duty Cycle they are limited to 112 cc/Min. If
you test a 550-cc injector in this machine it can only run for 9.8 Seconds without overflowing
the test tube. As you can see testing at 60 Sec. will be 6 times more accurate than a 10-Sec.
Test. The Margin of error increases dramatically with a decrease in test time. If you use one
of these machines you must test at very low speeds and for a very short period of time, you
don't have any choice. In a test at 8000 rpm @ 80% Duty Cycle you would be limited to only
12 Sec. of test time, with a 550 cc Inj. I'm sure that these machines are quite adequate for
most tune up applications and repair stations but they have their limits. That limit is a, 6Ms at
Fast Idle, test result. We don't feel that this is a very conclusive evaluation when testing high
performance injectors. Time is money, but "In the Race for quality and perfection, there is no
Finish Line," or Time Slip waiting for you.

All currently used injectors are designed to operate between 2.5 Bar/36.25 P.S.I. and 3
Bar/43.5 P.S.I. Chrysler some times uses 3.7 Bar/55 P.S.I. as does Porsche. There are some
rare exceptions to these standards, but they are rare. By using 3 Bar as a standard, we can
easily compare an injector, rated at 252cc @ 2.5 Bar (36.25 P.S.I.), to an injector that is
rated at 2.7 Bar, 3 Bar or 4 Bar. (See Pressure later)

Minimum cycle time for most pintle types is 2.0 Ms. for P&H and 2.5 for Saturated units. The
Disc will cycle as low as 1.0 Ms., pulse width, in P&H and .2.0 Ms. for the Sat. Unit. (The
Lucas Disc weighs only .4 Grams. and the Bosch / Nippon -Denso pintle is at 3.9 to 4 Grams.
--- Ten times heavier) The reduced inertial loading of the disc, allows the Disc to overcome the
hydro- static load at excitation quicker and return to it's seat faster, providing quicker response
times and more consistent cycle-to-cycle values.

Most pintle type injectors fail at 86%/88% and the Disc will usually go to 92% +, depending on
system pressure. All must cycle smoothly up to 85% to Pass. Bad injectors will sometimes
go "static" at 70% or so and are discarded. NOTE: Most pintle injectors will increase flow
rates up to 88%, 92% with Disc injectors, and then go "semi-static", half open-half closed, just
before going full static. This time-out event occurs at different time/pulse width durations, in
different injectors, but always produces a 50% or so Duty Cycle flow rate. This extremely
dangerous situation will usually occur at the worst of times, full throttle-max boost-high RPM-
just when you need 100% fuel delivery you get 50% and go dead lean. BANG!!! This problem
seems to amplify a bit at higher pressures.

PRESSURE AND FLOW CHANGES Fuel pressure changes will alter flow rates as follows -
To find a new Flow Rate from a PSI change, Divide the new Pressure by the rated or old
pressure. Find the square root of this number and multiply it by the old or rated flow rate.
Example: Injector rated at 430 cc/Min at 43.5 PSI. If you raise the pressure to 49 PSI - Divide
(49 / 43.5) = 1.1264 --- The Sq.Root of 1.1264 = 1.0613 --- Multiply 430cc X 1.0613 and you
get 456.37cc/Min. This will be your new flow rate. The injector size will still be listed at
430cc/Min @ 43 PSI.

To find the Pressure required, to produce a Desired Flow Rate, use this Formula. Divide
desired flow rate by test flow rate, Square this number, and multiply it by the test PSI. The
answer is the PSI required to produce the desired flow rate. To increase a 720cc/Min. injector
rated @ 43.5 PSI to 800 cc/Min. --(800cc per/Min) / (720cc per/Min.)= 1.111 X 1.111 = 1.234
(1.234 X 43.5 PSI)= 53.7 PSI. New pressure of 53.7 PSI will yield 800cc/Min. from a
720cc/Min. rated injector. Caution: Up-graded fuel pumps will be required in many cases
when significant injectors or pressure changes are made.

PATTERNS Of the 6 Basic metering devices used today -- Pintle (Bosch / Nippon -Denso
type), Ball and socket (Rochester), Radius Rod (Siemens), Swirl plate (some Mitsubishi),
Diffuser/Pintle Type (Toyota - and some models of all makes) Air feed Atomizers (many
makes for emissions reasons) and the Disc Type used exclusively by Lucas. The atomization
and pattern width will increase on single discharge pintle type injectors at, higher pressures.
The Lucas Disc type does not deviate as severely. Dual discharge, diffuser type, pintle
injectors don't change atomization quality, at higher pressures, like the single pintle discharge
injectors. Dual discharge injectors target the fuel toward the valve stem and reduce wall
wetting, (puddling) behind the valve. These injectors are not high atomizers but targeted
delivery types.

The Lucas injector maintains its pattern, cycle to cycle, the best under varying pressures and
pulse widths. Diffuser/Pintle injectors have a rather tight, wetter pattern (more coalescence)
than single discharge injectors. This is evidently caused by the impact of fuel on the diffuser
surface causing the fuel to partially recollect. This provides a more concentrated liquid volume
flux at the center of the cone, a tighter pattern angle, and a more accurate targeting capability.
Cross sectional area of the port and distance to the valve is crucial with this type of injector.

At 8000 RPM the intake valve is opening and closing at 66 times a sec. and is only open for
an average of 9 Mil/Sec. At this cyclic rate the transient time to complete the delivery of fuel,
from injector to valve, is critical. This is why; Indy car injectors are very precisely targeted and
timed to provide a solid stream of fuel with non-existent atomization, LBDS, "Laser Beam
Delivery System". In these engines the injectors can discharge fuel, at a "just prior to valve
-open position", and get it all down the hole. As the fuel impinges the hot intake valve it
virtually vaporizes and mixes quite well with the incoming air forming a very homogenous
charge. This is one of the most extreme situations but it's a real interesting one. As an added
benefit, the latent heat of fuel vaporized in the chamber also provides charge cooling that
makes the mixture denser. A denser, heavier mixture (cold and thick) will produce more power
then a thin (hot and light) charge. This is why Turbo intercoolers are so effective. Injector
timing, phase angle, is altered by the ECU according to RPM in these systems and can
control the delivery impact time precisely. In a, Steady State pressure, Fuel System the
injector pulse is always moving at the same speed, regardless of engine speed changes. The
velocity of discharged fuel is relevant to the area of the discharge port and the net operating
pressure. Pressure changes activated by boost, at a 1:1 ratio, only compensate for port
pressure and don't change the static pressure, flow rate or velocity. RPM adjusted fuel timing
is utilized for this reason, it advances the injector timing based on engine speed, and
maintains perfect impingement timing at all speeds.

[Cameron_Datto]

ATOMIZATION High atomizing injectors are usually used in Throttle body applications only,
and have a rather wide spray pattern. A wide, finely atomized pattern is wonderful for
emissions and economy but can cause problems in higher performance engines. At low
RPMs, with a low air flow rate, the slow moving finely atomized fuel has enough time to get
past the valve and create a close to stoichiometric mixture. (Air/Fuel mixture of 14.70 -
Chemically ideal) As RPMs increase this mass can't keep up, with valve open time, and
many of the fuel droplets impinge the port wall and condense. Atomized fuel can only travel at
port "air speed" and in large quantities it can actually displace air in the port. With a highly
atomized mix in the port, at intake valve opening, the lighter droplets of fuel will be partly blown
back up the port. This is caused by the residual exhaust pressure still resident in the
combustion chamber. Some of this reverted mixture will adhere to port walls and condense.
This puddling fuel may find its way home, on the next intake cycle, but it will cause
cycle-to-cycle air/fuel ratio variances. The higher inertia of the more condensed fuel will carry it
to its target. "The liquid film that wets the walls represents a capacitance that greatly reduces
the transient response of the engine." (SAE 950506) This problem is compounded in Gang fire
and Semi-gang fire systems, but is not as troublesome in sequential fire systems. Gang fire
systems fire all injectors, every rotation, at the same time, discharging half of the required fuel
at each event. Semi-gang fire systems fire groups of injectors in the same fashion,
half-and-half, each rotation. Sequential systems fire each injector at a pre-determined time and
discharge all required fuel in one event, prior to intake valve opening. In either of the gang fire
systems there is no timing-of-event technology in operation, and as you can see it's a rather
simple system. NOTE: 7M-GTE fuel systems are semi-gang fire, as is the ignition system,
and the injectors are fired in the same order, 1&6-5&2-3&4, as the spark plugs. 2JZ/GTE
systems are true sequential operations, 6 coils, 6 injectors, and 12 separate events---- A state
of the art well formatted system.

It's a known fact that you can't burn fuel until it's atomized. It's also known that you can't burn
fuel without air. The most important, of all known facts is that you can't burn anything, if it's not
in the combustion chamber. The secret is to provide adequately atomized fuel with as much
air as possible. Adequately atomized is the Secret Word of the day. Fuel does not have to be
completely atomized at the injector tip (SMD of 10um - 20um) but it does have to get past the
valve to do us any good. The more condensed the fuel delivery is the faster it will travel,
(regulated by discharge area and pressure) and the more accurately it can be targeted. Resent
(S.A.E.) "Injector Atomizing and Targeting" studies have provided us with one of the most
prominent advances in High Performance Engine Management. These test programs have
concluded that "accurate impingement onto the center of the valve head is vital for good
vaporization" and "The targeting orientation of the injected fuel spray is a critical parameter in
fuel evaporation" also that " Fuel injected directly onto the intake valve yields a significantly
better engine response" (SAE950506) What all this means is, different engine designs require
a different type of injector to operate efficiently and that 100% atomization is not always
required or desired. In racing situations we usually have to do the best we can with what we
have, or what's available. The goal, is of course, is to do the best in all cases, and in all
situations. The best injector for your engine is the one that will yield an optimal fuel-air mixture
and provide the required power output consistent with smooth and reliable operation.

[Cameron_Datto]

INJECTOR TYPES:
Peak and hold injectors are fired at 4 to 6 Amps, through a ballast resistor, and then fold back
to 1 - 2 Amps for the duration of the injection event. They are also known as "fold back"
Injectors. Peak and hold injectors are faster responding than Saturated injectors by as much
as 1 to 1.5 Ms. They are activated with more power at opening than the saturated types (4-6
Amps vs. .75 -1 Amp.). Peak and hold injectors will maintain injection delivery, cycle to cycle,
continuity more accurately than the saturated type. This is particularly true and even more
important in high-pressure (75 - 100+ PSI) systems. The higher Hydrostatic loading at
excitation requires more amperage to initially activate the injector solenoid and properly
maintain complete opening. Peak and hold systems are more expensive to manufacture
because they require one computer "injector driver" per injector in most applications. This is a
design requirement in Sequential Fire Systems where each injector is fired at a very precise,
pre determined, time in the 720 degree 4 stroke processes. P&H injectors are also wound with
copper wire instead of brass wire. Early 7M-GTE used Type E - P&H rail feed style up through
1992 and then changed to Type E, galley Feed units for the 2JZ/GTE Toyota lists and rates all
of their injectors in cc/Per Minute at different pressures, 36.4 PSI. & 41.2. PSI.---- 7M-GTE
injectors are listed at 430 cc Per/Min. at 42.1 PSI. and the 2JZ/GTE are rated at 540 cc/Min.

Saturated injectors are used in almost all-standard production, 1998, engines because of the
system cost and simplicity. Saturated based systems usually fire all injectors at the same
time, once every rotation discharging half of the required fuel per cycle at each event. Some
systems fire half of the injectors at one time and the other half at a different time. These
systems are called "Batch Fire" and "Semi-Batch Fire " respectively. This system is used in
90 % of all general production engines (cost and simplicity). In almost every case
Manufactures will only use Peak and hold injectors in High Performance applications or in
Turbo applications. This is true in the Ford/Mazda family, Chrysler/Mitsubishi family, Nissan
Group and the Honda/Acura folks as of 1997. General Motors/Toyota cars are also in this
same family. OEM APPLICATIONS GM uses Saturated Rochester injectors in everything but
some of the High performance cars, hear they use Lucas Injectors, and in the turbo trucks
they use Bosch. Toyota uses saturated injectors in everything but its turbo models - all
Nippon-Denso. Honda, last year changed all but the NSX to saturated, most all of Keihin make
with some IPT. Nissan uses saturated units only, as of this year, Jecs or Hitachi
manufactures. Chrysler/Mitsubishi - same deal - all but the turbos are saturated, Siemens or
Bendix make. Ford uses Bosch or Nippon-Denso depending on the Model. All are Sat. except
Turbo Models. Bosch and Lucas injectors are used in VWs.. BMW , Bosch up until this year,
now Lucas --- European cars use an assortment of injectors including Weber, Bosch and
Lucas.

[camrygt?]

Also i hope you've though of the fuel pump to run such large flows.
BOth ECU & injectors are not going to be able to be sustained with out more fuel pressure. At those levels an adjustable fuel regulator would also be of help.

not necesarily true. A bigger injector will flow more fuel with the same duty cycle and fuel pressure compared to a smaller injector.
Higher fuel pressure is generally something to do only when you need to get a few percent more from your injectors as the fuel pump then has to deliver high pressure and high volume which needs a much more powerful pump.
Most fuel pumps will delivery a much larger volume of fuel at say 30psi than they can at say 60psi so for example 800cc injectors and standard fuel pressure will be a better fuel system than say 600cc injectors and 60psi of fuel pressure.
Also a bit safer less chance of leaks at lower pressures.

A far as choosing an ecu if you are getting big injectors probably over about 800cc then an ecu that can drive low impedance in a peak and Hold arangement would be better, The cheapest ecu I am aware of that can do this is the Adaptronic.
I don't believe Microtechs can but I have seen cars with 1000cc injectors that idle well with Microtechs

[CrUZida]

I haven't seen any Microtech's that are controlling two 1000cc injectors per channel, but seen many controlling one per channel.

Are you saying the Adaptronic will happily control two 1000cc injectors per channel (I assume yes since it only has 3 (4?) inj drivers).

[camrygt?]

I'm not sure where the 2 1000cc injectors bit comes from are we talking about a 4AGZE or some other motor in this thread?

Anyway Adaptronic will drive two injectors per channel with up to 4 channels, high impedance in parallel and low impedance in series, with the options for 0.5A, 0.9A,1.5A, 1.9A constant current or peak hold.

[benjamin]

Cameron Datto: Thank you heaps that info was exactly what I was after. +ve rep

The computer I want to get for my car is the Adaptronic. It looks the best option for my budget and seems to be a far superior computer in comparison to a Microtech and other standalone ones in a similar price range.

[Cameron_Datto]

Thanks for the positive feeback on my Reputation ,:>)

[Cameron_Datto]

This place seams to be the cheapest place to buy injectors in Australia, i have found so far ,,

http://www.injectorsonline.com/

[oldcorollas]

some of the copied info above is correct and some not

in OEM applications, for toyota as well as other makers, both high and low are used, hoever, often a resistor pack is used with the low impedance to increase their resistace, allowing it to be used for a constant current driver.

peak n hold, when driven correctly, will flow a smaller amount of fuel during the opening and closing movements, adn this is where they excel over high impedance. it means that your minimum amount of fuel injected is smaller, so that when you make adjustments around idle, they actually mean something

sure some people get 1000C injectors to idle well on rotaries.... relatively

the cheapest ECU that does peak and hold is the MEGASQUIRT. i can't remember how many channels of it it does...

the main benefit of peak n hold in reality is when using large injectors on a small capacity forced induction motor. so that you can still get decent idle and offboost mixtures.

the other way to go (tho for you with 500cc inj, not really needed) is to stage the injectors in two seperate banks and bring the second set in on a different map. The Megasquirt also does this

Ben, what it comes down to for your choice is... how much or litle fuel is needed at idle, and is this amount smaller than will be provided by a high impedance injector at it's minimum pulse width.