The beauty of this site is the ocean of knowledge that pours in uncontrollably. However, I searched my *** of, and found a bunch of conflicting answers.

https://www.rx7club.com/forum/showthread.php?t=704745

https://www.rx7club.com/forum/showthread.php?t=713660

https://www.rx7club.com/forum/showthread.php?t=733710

https://www.rx7club.com/forum/showthread.php?t=714306


All good info, but nothing's very clear.

Here's my simple question, to which I HOPE to get a simple answer.



I'm doing a TII swap into an 88 convertible. The engine is from an 87 TII. The TII injectors are low impedance. My convertible ecu is low impedance. I apparently can run my convertible ecu with the TII engine, as shown here:

https://www.rx7club.com/forum/showthread.php?t=698632

So. I assume I'll be wiring in some resistors in SERIES with the injector wires.

What is the definitive resistance I'll be wiring in? Is it 6, 6.8, 8, 10, 12, or 8437590 ohms? Should I just get some variable resistors and wire them in to tweak the perfect resistance? I'm really confused right about now, and all this searching is making me fall asleep at the computer.

 

You need to install one six ohm resistor in each circuit of each injector. That's the bottom line.

Ignore the words below if you want. Typing.

Cars that have LOW impedence injectors i.e. early 87, have injectors of 2-3ohms AND something called a Solenoid Resistor Package that the power wire for the injector passes thru on the way to the injectors. It has four SIX ohm resistors inside it. So what you'd have, is an injector of 2-3 ohm plus a resistor of 6ohms in the power line. Comes to approx 8-9 ohms total prior to the ECU.

On a later than June 88 you have a injector of approx 12 ohms and NO six ohm resistor in line prior to the ECU (no Solenoid Resistor Package).

A picture of the solenoid resistor package is attached along with how it was used in the early 87 cars. Ignore the part of the picture that is enclosed in RED.

I would have used a N333 or N332 ECU. How the convertible ECU can work with a turbo engine is something I don't understand. You also should need a turbo afm and especially a turbo boost sensor to replave the non turbo pressure sensor.

So it's NOT the ECU that is low or high impedence, it's the value of the resistance prior to the ECU that counts. NO 88 had low impedence injectors.

 

Thanks Hailers, you just saved me a massive headache. I've already got the pressure sensor, AFM, and the variable resistor, but the 2 things that the guy did not have were the ECU and 1/2 of the harness, since he cut it.

I know the ECU doesn't make it high/low impedance. However, the injector driver for a high impedance circuit (which is inside the ECU) will burn up if I don't do something about the high current flowing through it due to resistance being much lower.

 

Hmm... where do you find 6 ohm resistors that have the right power rating. Correct me if I'm wrong, but assuming 14.4 volts, and 3+6ohms=9ohms. Therefore, the amperage is V/R, so 14.4/ 9 ohms = 1.6 amps. And since Power = Current X Voltage, it's 1.6A X 14.4V = 23watts.

23 watts!?? All the places I've looked for resitors have at the largest, 1W resistors! Any suggestions?

 

https://www.rx7club.com/showthread.p...ighlight=watts

https://www.rx7club.com/showthread.p...0+ohm+resistor

 

AGreen,

These are the ones I ordered.

Resistor, Wirewound; 6 Ohms; AL Hsd; Solder; 25 W; +/-1%; 0.438 In.; +/- 50 ppm/degC; 10 $3.07 (Each)

25W with heatsinks. Here Aaron Cake says that they'd use 17watts at full duty cycle which of course doesnt happen.

I built and painted a mounting plate for mine today and soldered and shrink wrapped leads to the terminals. Tomorrow I'll pull the 10ohmers and we'll see if my hesitation goes away.

Good luck,

Jim

PS, price with shipping, TX tax and "handling" was $24.33