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[Datsun 1200 encyclopedia]

Budget EFI

From Datsun 1200 Club

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Category: Fuel Injection

Convert your A engine to EFI. Big HP (120hp) at a small price ($635 AUD w/o tuning).

Contents

Youtube

 V I D E O  Datsun A12 EFI (click to view)
hqdefault.jpg

Manifold and Injector

Rather than fabricate a custom manifold, use the stock one that's already on your A12! The photo here show the intake unbolted from the exhaust, but you can do it while it's still together.

Build instructions

Parts needed:

  • Stock A12 intake manifold
  • #Throttle Body (40mm) from a Hyundai Excel/Accent X3 SOHC
  • #Fuel pressure regulator from a circa 1997 Misubishi Lancer
  • 3-5mm thick alloy plate for the adapter
  • Fuel Injector (365cc for stock A12)

6746_5507ae76319f2.jpgPost 464761

Injector/Regulator assembly
6746_5514bb8b3741f.jpgPost 465339

  • Buy a brass Tee 1/4"
  • Drill each end to 14mm opening for the push-in type injector and the push-in type regulator
  • leave center T threaded, and screw in a barbed line fitting (for fuel supply hose)
  • Drill the manifold PCV opening with 14mm drill bit (for push-in type injector)

Assembled
6746_5514bc43661f9.jpgPost 465339

The injector assembly can be secured to the manifold with simple copper wire tie, or positively bolted on using custom brackets (see injector mounting).
6746_5514ddb743e94.jpgPost click for topic

Pressure Regulator/Injector assembly installed
6746_551625dbea3e4.jpgPost 465339

TB vacuum taps

You can use the stock 1200 air cleaner
012-01a.png

A seal between the throttle body and air cleaner can be fabricated, maybe using rubber hose cemented to the air cleaner bottom
6746_5514bd9947552.jpgPost 465340

Throttle Body

The X3 Excel Throttle Body is dime-a-dozen and easy to adapt. The 1995-1999 Hyundai Excel X3 (Accent in USA) SOHC engine is the source. Don't forget to get the wiring harness connectors and a couple of inches of wiring for the attached TPS.

6746_5507acd79d5d3.jpgUpload click to view

From the wreckers, get the throttle body with TPS attached.

Airtex_5S5179.jpg

New TPS is as inexpensive as $22 rockauto.com. New Throttle Body (mixing body) is $183 from Hyundai, so buy a used one for $30 or so at the wreckers.

Hyundai X3 (Accent/Excel/Verna)
400px-%2796_Hyundai_Accent_Hatch.JPGWIKI go to Wikipedia

Fabricate the adapter out of aluminum sheet, using a stock gasket as a pattern
6746_5507ad73e7dee.jpgUpload click to view

6746_5507ae40672e5.jpgUpload click to view

Smooth Throttle Bore to better match the manifold. Use a round file or a rotary grinder
6746_5521ed75b1fcb.jpgUpload click to view

Drill new holes in the Throttle Body flange and bolt it on
6746_5507ae76319f2.jpgUpload click to view

Remove throttle bracket from Datsun carburetor
6746_5507e700d8441.jpgUpload click to view

After cutting, bolt to the Throttle Body
6746_5507e72b2f844.jpgUpload click to view

Fabricate throttle cable bracket from a short length of tubing and a strip of sheet metal
6746_55431eaa185a8.jpgPost 467154

Fuel Pressure Regulator

Fuel Pressure regulator from a 1997-2001 Misubishi Lancer 1.5 engine, $15 used

Search
$35 RockAuto.com 51 psi
BECK/ARNLEY 1580463 {#MD311979)
STANDARD MOTOR PRODUCTS PR247
AIRTEX / WELLS 5G1265
Denso MD 311979
BA1580463.jpg

Mitsubishi Lancer/Colt/Mirage 1997-2001
400px-1997_Mitsubishi_Lancer_%28CE%29_GLi_sedan_%282015-07-14%29_02.jpgWIKI go to Wikipedia

Sensors

With MegaSquirt you won't need the Datsun airflow meter. Instead, Megasquirt will calculate the air mass using a MAP sensor and and IAT sensor.

  • MAP sensor is built into Megasquirt. Connect vacuum hose to manifold
  • Obtain GM IAT sensor from a Chevrolet or Holden. Drill hole in your air cleaner and hot-glue the IAT in place. Or use JB-weld. Threaded bungs are available if you want to get really fancy. You can also place the sensor in a air-cleaner-to-throttle body pipe/hose. Alternatively you can drill the throttle body and tap it (3/8 NPT) to accept the sensor (see post)
* MegaManual
* GM IAT Sensor 12146312 $10 RockAuto.com
TS10075A.jpg
* GM sensor connector 12162193 $5 RockAuto.com 
HP3840.jpg

Fuel System

Use a external EFI fuel pump, connected to the stock fuel line coming from the tank. We have selected a 51-psi system, so need a pump capable of high-pressure.

* Carter P74015 $70 rockauto.com
* Airtex E8228 Universal $79 Amazon.com

Pump can be placed in engine compartment or back by the tank. If you put it up front, you can use the stock hard line from the tank.
P74015_P04_KIT.jpg

Run a regular low-pressure fuel line from the regular back to the the tank, and Tee it in to the filler hose. If you keep the tank above 1/4 full no extra baffles or surge tank are needed. If you want, add a $50 Surge Tank. Have a shop braze a 5/16" line to a length of muffler pipe the right diameter for your tank filler hose.

KATS plastic 2" hose adapter $3 (will it resist gasoline?)

Stainless marine filler hose adapter $30-$60
HDT-2212_INLINE_FUEL_RETURN_TEE.jpg

From the fuel pump output to the fuel rail, use EFI-rated fuel hose and EFI hose clamps. Best price is often at your local auto parts store in bulk (sold by the foot, $2-$3 USD/foot). Clamps can be had for less than $2 each. Best to use a hard line for the majority of the run.

Use a 280ZX-style fuel filter. 280ZX EFI fuel filter $3 RockAuto.com
BA0430165.jpg

The fuel pump is wired up with a relay -- you don't want the high current to go through your ignition switch. As cheap as $10 for a used Nissan relay.

See: Electric_Fuel_Pump#Wiring
22115.jpg

Ignition and Distributor

The ECU can take the RPM signal direct from your existing points-based distributor. It's also compatible with electronic ignition distributors.

Wiring

Wire up the MegaSquirt harness

  • 12V
  • earth/ground
  • fuel pump relay
  • injectors
  • IAT signal & ground/earth
  • Tach signal (coil negative terminal)

For full details, see http://www.megamanual.com/mtabcon.htm#wire

ECU

Buy MegaSquirt II fully assembled about $400 USD or $500 AUD off eBay.

ECU Configuration

Download at http://www.diyautotune.com/softwarelinks.htm

  • Mac
  • Windows
  • Linux

You have a choice:

  • TunerStudio free version (most popular software for MegaSquirt)
    Free version supports all MegaSquirt features
  • SuperTunix open source

In the software configure:

CONSTANTS
Required Fuel
* displacement 1171cc (A12)
* # of cyl 4
* injector flow rate 365
* desired AFR 13
Injector open time 1.0ms
batt V correction .20
PWM current limit 1000%
PWM time threshold  25.4
Fast Idle Threshold
Barometric Correction: Off
Control Algorithm: Alpha-N (TPS)
Injections per Engine Cycle: 2 squirts
Injector Staging: simultaneous
Injector Port Type: throttle body
Engine Type: even fire
VE TABLE

Generate a new table based on your peak horsepower and torque figures ('Settings/VE Table/Tools/VE Specific/Generate VETable').

ENRICHMENTS
EGO Step (%): 0
Warmup enrichment
-40F 180%
-20F 150%
 0F 140%
 20F 135%
 40F 130%
 60F 125%
 80F 118%
100F 110%
130F 103%
160F 100%

Afterstart Enrichment: between 25-45%for 100 to 250 cycles,

Software Tuning

Start your engine and let idle. Go to http://www.megamanual.com/v22manual/mtune.htm

And start tuning.

A big help in turning is to fit an Air Fuel Ratio Gauge. MegaSquirt 2 can directly read the wideband output of the wideband controller, but more importantly you can see the A/F Ratio on the gauge.

 See Main Article: Oxygen_Sensor#Air_Fuel_Ratio_Gauge

540-3824.jpg

The paid version of TunerStudio has a software auto-tuner which is supposed to be great, but it still requires some work (it's not totally automatic).

Cost

* $400 ECU with wiring
* $  0 Stock A12 intake manifold 
* $ 30 Throttle Body
* $ 15 Fuel pressure regulator
* $  5 3mm thick alloy plate
* $  7 Fuel Injector
* $ 20 new IAT Sensor & connector
* $ 79 new 60psi fuel pump
* $ 15 fuel hose & clamps (for front-mount pump)
* $  3 high-pressure fuel filter
* $ 10 Nissan relay
* $  5 fuel pump wires
* $  3 fuse
* $ 20 oil pressure safety switch
* $  6 1/8 BSPT-to-1/8 NPT adapter
* $  6 fuel filler hose Tee
* $ 10 generic air hose
------
$  632 TOTAL not including tax & shipping
Tuning:
* $181 new A/F gauge, wideband controller & sensor
or
* $?   engineer & dyno time 
¤

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