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How to MegaSquirt your Volvo
240, 740, or 940
Updated 10/09/2008
Overview
The Volvo 240 and its relatives have a well balanced rear wheel drive chassis
and a solidly built engine, but when you start adding boost the stock engine
management system
can have problems accounting for the extra air flow. Fitting a MegaSquirt to these
cars allows you to properly tune the engine for anything from a mildy modified car to
an all out turbo drag buildup or IT racer. While there's a lot of similarities between the 240, 740,
and 940 chassis, Volvo used several different fuel and ignition control systems
over the years. They did not always keep the electronics the same across all
three models, or from naturally aspirated to turbo motors.
Note that our tech 'Install Articles' typically focus on the most confusing
part of the install process for the end user, and that's taking control of the
ignition system. This is the part of the process that's different from car
to car and hence we chime in with specifics to help where we can. For the
rest of the details, the parts that are the same on every car like the coolant,
intake, TPS, and o2 sensors, see the
wiring
section of the MegaManual.
Applications covered by this
article:
This article covers 1985-1989 Volvo 240's, 740's, and 940's with the Bosch
LH2.2 Ignition/Fuel control system, as well as other years which have been
fitted with the distributor and ignition module this car used. The Bosch Hall effect distributors let you use almost any
MegaSquirt variant
out there.
The Bosch LH2.2 system kept the
ignition control separate from the fuel control (two separate computers), and these used a Hall effect
sensor in the distributor that reads a rotor with four vanes on it. This
ignition system is
pretty easy to take control of. One way to spot the Bosch LH2.2 system in your
Volvo is it used an external
ignition module (ignitor box). These engines did not have a crank trigger.
Bosch built several different ignitor boxes during this time period. Most of
the ignitors installed in Volvos appear to have left dwell control up to the ECU.
If you have an L-Jetronic or LH-Jetronic EFI
system, you can simply wire the injector wires that led to the ECU to the
MegaSquirt instead. With a K-Jetronic mechanical fuel injection system, you will also need to swap your fuel
system over to EFI.
Applications this article does NOT cover:
Many non-turbo 240s used a Chrysler
ignition through 1988, with a Bosch fuel injection system. That means a Chrysler
Ignition Computer, and a Bosch Fuel Computer, working mostly independently of
one another to meet the engine's needs. We have confirmed
that this system was used as far back as 1982. You can spot a Chrysler
Ignition system by
its lack of an external power stage module (aka ignitor) - with the Chrysler
ignition system the coil is wired straight to the
Ignition ECU (remember these cars will have a separate computer for ignition and
for fuel). It is not clear if the Chrysler distributor works in the same
way as the Bosch distributor or not.
Later engines, starting around 1989, used a 60-2 crank trigger. As with the
Chrysler distributor, the settings for this one are not as well documented,
although MegaSquirt can control this too, the details just aren't in this
article. Ask us if you'd like help. At
the moment, this article covers the Bosch LH2.2 distributor. Information on the
Chrysler and crank triggered setups will be added as it becomes available.
Using
the MegaSquirt-I (MSnS-E) with the Bosch ignition module
Since there is no need for a VR conditioner or
onboard coil driver, you can use the V2.2, V3.0, or V3.57 board.
MegaSquirt-I
PCBv2.2 Mods
Required:
- Remove D5, D8, and R10. Also remove the
jumper between XG1 and XG2.
- Replace D8 with a 1K resistor.
- Run a length of wire from XG1 to the right
hole of D5.
- Run a wire from the bottom hole of R10 to
the top of R11.
- Run a 750 ohm to 1K, 1/4 watt resistor
from the right (5v) side of R23 to the negative (top) leg of D17.
- Run a wire from the negative leg of D17 to
X11.
- That's it!
MegaSquirt-I PCBv3.0
Mods Required:
- Build the Hall
effect input
conditioner circuit, as described in Step 50A of the MegaManual. All
our preassembled MegaSquirts with the V3.0 board come with this
circuit installed. However, the jumpers are a bit different:
- Get a 1K 1/4w
resistor and cut the leads down to about 1/2" at each end. Maybe a
bit less.
- Tin each end of the
resistor with a bit of solder.
- Cut a 5" piece of
hookup wire (22ga is fine) and strip just a 1/8" or so. Tin the
stripped wire with solder.
- Melt the tinned
wire tip to one end of the tinned 1K resistor tip and let it
cool.
- Heatshrink wrap
this wire/resistor assembly.
- Use this
wire/resistor combo to connect OptoIn to one of the 5 volt holes in
the proto area.
- Jumper TachSelect
to XG1.
- Jumper TSEL to
OptoOut.
- Solder a 750 ohm to
1K, 1/4 watt resistor from the right (5 volt) leg of R24 to the top
(negative) leg of D14.
- Run a wire from the
top leg of D14 to IGN.
That's it!
MegaSquirt-I PCBv3.57
Mods Required:
- For this one,
you'll remove the jumpers on XG1 and JP1. Put the jumper on J1 in
the 1-2 position for optical output.
- Get a 1K 1/4w
resistor and cut the leads down to about 1/2" at each end. Maybe a
bit less.
- Tin each end of the
resistor with a bit of solder.
- Cut a 5" piece of
hookup wire (22ga is fine) and strip just a 1/8" or so. Tin the
stripped wire with solder.
- Melt the tinned
wire tip to one end of the tinned 1K resistor tip and let it
cool.
- Heatshrink wrap
this wire/resistor assembly.
- Use this
wire/resistor combo to connect pin 3 of the JP1 jumper to one of the
5 volt holes in the proto area.
- Solder a wire from
XG1 to pin 2 of the JP1 jumper.
- Run a wire from
PAD1 to the center hole of Q16.
That's it!
External Ignition Wiring
- Connect the signal wire from the Hall
effect
sensor on the distributor to pin 24 (Tach on the relay board, if
used). See
notes at the bottom of this article for the wiring colors on various
distributors.
- Connect the #5 pin of the Bosch ignition
module (for a 124 type module) or #6 pin (for a 139 type module) to
the MegaSquirt's spark output pin. On a V3.0 or V3.57, this is pin
36. On a V2.2, this is pin 25.
MSnS-E
Ignition Configuration
- Configured for MSnS
Spark Output using LED 17 (D14).
-
In MegaTune, you must
set Spark Output Inverted to No.
-
Set the Dwell Control
mode to Fixed Duty with a 50% duty cycle if you have a 139 type
module. If you have the 124 type module (Volvo P/N 1 332 584), you
will need to use dwell control instead.
-
The Trigger Angle
setting will depend on the physical location of the trigger pickup.
Often, an angle of 60 degrees will get you in the ballpark. To set the timing with MSnS-E,
go to the Spark Settings menu and set Fixed Angle to 10 degrees. You
can then set the ignition timing to 10 degrees with the engine
running, using a timing light. Once you have set the base timing,
set Fixed Angle to -10. This will tell MSnS-E to use the timing map.
See
the
MS1/Extra manual on Bosch 139 modules for more information. |
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Using
the MegaSquirt-II PCBv3 or v3.57 with the Bosch ignition module
Note: This version does not work with the Bosch
139 module.
MegaSquirt-II PCBv3.0
Mods Required:
- Build the Hall
effect input
conditioner circuit, as described in Step 50A of the MegaManual. All
our preassembled MegaSquirts with the V3.0 board come with this
circuit installed.
- Jumper TachSelect
to OptoIn.
- Jumper TSEL to
OptoOut.
- Jumper XG1 to XG2.
- You'll need a 1K
pull-up resistor from the 5 volts in the proto area to TachSelect.
- Jumper JS10 to IGN.
That's it!
MegaSquirt-II PCBv3.57
Mods Required:
- Put the XG1 to XG2
jumper in place across both pins.
- Put JP1 in the 2-3
position and J1 in the 1-2 position.
- Solder a 1K resisor
across the R57 pads.
- Run a wire from
JS10 to the center hole of Q16. (This is normally installed by
default.)
That's it!
External Ignition Wiring
- Connect the signal wire from the Hall
effect
sensor on the distributor to pin 24 (Tach on the relay board, if
used). See
notes at the bottom of this article for the wiring colors on various
distributors.
- Connect the #5 pin of the Bosch ignition
module to the MegaSquirt's pin 36.
Megatune Ignition
Configuration:
- Trigger
offset = 60°
(this will vary, depending on the distributor orientation, see notes
at the end of the article)
- Ignition
Input Capture to 'Rising Edge'
- Cranking
Trigger to 'Trigger Return'
- Coil
Charging Scheme to 'Standard Coil
Charging'
- Spark
Output to 'Going High (Inverted)'
See the
Bosch 124 page
for more information.
More information on
setting Trigger Offset:
You must also set the
initial position of the trigger (called the 'trigger offset'), then
check it using the Trigger Wizard in MegaTune (Tools Menu). The
trigger offset setting will vary according to your distributor position
(where it is in rotation) but you'll need to set it properly...
Basically you use the Trigger Wizard and adjust the 'trigger offset'
and/or twist your distributor until the advance number in the Trigger
Wizard matches what you're reading with your timing light. The +/-
buttons on the trigger wizard will adjust your trigger offset. You'll
need to use these buttons and a timing light to make the number on your
light, and the big number on the left in the Trigger Wizard, match up.
Here's the information
on this direct from the MegaTune Manual:
Before tuning your
advance table, be sure to use a timing light to verify that your 'trigger
offset' is calibrated. Changing the Trigger Offset in MegaTune will
not change the displayed advance, instead, it changes the actual advance
as seen with a timing light. Your goal is to make these two match.
To do this, get your
engine warmed-up (otherwise the timing moves as the temperature
increases) and idling, then use a timing light to verify to be certain
your actual advance as shown by a timing light equals your the advance
display on the advance gauge in MegaTune. (8° in this case). (Note that
positive numbers denote BTDC, and negative numbers denote after TDC.)
Image courtesy
of Bowling and Grippo
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IAC Valves
It appears that earlier models may have used a thermal auxiliary air valve
for idle control. Later ones used a pulse width modulated idle air control
valve. V3.57 boards need no
modifications to control the PWM valve, while V2.2 and V3.0 boards will need a
TIP120 transistor, like the one included in our MK-PWMIAC mod kit.
Suggested parts
These car can use just about anything in the Megasquirt family, although the
V2.2 can limit your injector options unless you use the flyback board. The Megasquirt-I V3.0 (or V3.57) will
work well for a good basic system. The Megasquirt-II can provide a better idle
if you are running very large injectors, so it can be useful on high boost
buildups but not required. You will be able
to use your existing sensors except for the MAP sensor which is built into the Megasquirt.
ECU options:
Mod kits discussed in this article:
Other recommended parts
If you are looking for an assembled unit with the mods in this article
already installed, please
contact us
directly. |
