how to install piggyback on 89 Iroc
04-09-2004, 03:44 PM
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Car: 1989 IROC-Z Camaro
Engine: 5.8L 355
Transmission: T-5 5-speed
how to install piggyback on 89 Iroc
I can't get any instructions on how to install a piggyback in my 89 Iroc. Can someone help me out??? Thanks
04-10-2004, 01:47 PM
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Car: 92 Form, 91 Z28, 89 GTA, 86 Z28
Engine: 5.7 TPI, LG4
Transmission: 700R4, 700R4
Axle/Gears: 3.27, 2.73
I did it with an intermediate harness so that it can be removed at any time without any splice into the stock harness. I had access to an actual ECU connector though, and bought the computer end of a harness from a 2.8L (had to rearrange the wires to match the V8 stuff). I did all the splicing into that and even rigged up some relays and switches to switch whether I was controlling the injectors, or the spark, or the IAC, vs GM. The switches control the relays, and the relays switch who is controlling the respective device. You may also want to rig a switch that disconnects the EGO from GM when the aftermarket ECU is controlling the fuel, so that the check engine light stays off.
The basic idea of a piggyback is that you can share TPS signals, MAP signals, EGO signals, REF, and Sensor Grounds. You cannot share Temperature sensor/thermistors - but there is a plug in the front of a TPI manifold perfect for another Ctemp sensor.
DO NOT wire the +5V sensor wires together from the 2 computers. Just use the stock GM +5V, and leave the aftermarket +5V open. DO wire the grounds together as close as possible. Also run a separate extra ground for the aftermarket ECU as specified. You can also use the same wire that turns the factory ECU on to turn the Aftermarket on. You can also tap into the ECU constant battery voltage wire for the aftermarket ECU.
At first, I'd highly suggest leaving the factory to control the ignition unless the aftermarket ECU has Knock Control. Also let it control IAC (idle).
With an 89 Iroc (I did an 89 GTA), you'll have to add a MAP sensor for the aftermarket ECU. I'm using the port that goes to the Fuel Pressure regulator with a T to share the vacuum.
What brand of ECU are you going to be piggybacking in? If you're just using a stupid AFC, just follow the instructions. Those are devices that lie to the stock computer and I don't recommend them at all. Actually, I'd recommend getting a Moates Autoprom, and tune the stock ECU - No wiring required, no expensive aftermarket ECU. If the changes aren't extensive, try stock first. If the changes aren't extensive and the stock isn't handling it correctly, do some diagnostics and maintenance.
Good Luck
The basic idea of a piggyback is that you can share TPS signals, MAP signals, EGO signals, REF, and Sensor Grounds. You cannot share Temperature sensor/thermistors - but there is a plug in the front of a TPI manifold perfect for another Ctemp sensor.
DO NOT wire the +5V sensor wires together from the 2 computers. Just use the stock GM +5V, and leave the aftermarket +5V open. DO wire the grounds together as close as possible. Also run a separate extra ground for the aftermarket ECU as specified. You can also use the same wire that turns the factory ECU on to turn the Aftermarket on. You can also tap into the ECU constant battery voltage wire for the aftermarket ECU.
At first, I'd highly suggest leaving the factory to control the ignition unless the aftermarket ECU has Knock Control. Also let it control IAC (idle).
With an 89 Iroc (I did an 89 GTA), you'll have to add a MAP sensor for the aftermarket ECU. I'm using the port that goes to the Fuel Pressure regulator with a T to share the vacuum.
What brand of ECU are you going to be piggybacking in? If you're just using a stupid AFC, just follow the instructions. Those are devices that lie to the stock computer and I don't recommend them at all. Actually, I'd recommend getting a Moates Autoprom, and tune the stock ECU - No wiring required, no expensive aftermarket ECU. If the changes aren't extensive, try stock first. If the changes aren't extensive and the stock isn't handling it correctly, do some diagnostics and maintenance.
Good Luck
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