2nd Gen RX7 ECU and Wiring Harness Question

[waynehussey]

Thanks Guys. Based on my reading of the GCR, I agree that we can use any ECU but still must keep the AFM.

Can anyone from the ITAC confirm Steve's undertanding of the replacing of the engine wiring harness rule. Based on ITCS rule D(1)(a)(6) &(7), you can modify or replace wires and connectors in the engine wiring harness and for any changes to the MAP and TPS. In addition, other existing sensors (other than AFM) may be subbed for equivlant unit. So what if I modify and replace all of the wires in the engine harness....is this still legal? Just want to be clear on the rule before I make any purchases. Based on the literal reading of the rule, if I replace the engine wiring harness as one unit with connectors, it seems to be the same as if I replaced each wire seperately in the engine wiring harness with connectors.

Just seems odd that they would allow us to us any ECU system that we want, but could not use the recommended wiring harness with the stock sensors to run the upgraded ECU system.


Thanks again.

[JeffYoung]

Wayne, Steve is my mentor, the light and the way, and the High Priest of Racing -- tongue only sorta in check, the guy knows his shit -- but I think you are right. "Modify or replace sensors and wire" means, to me, you can use the harness that comes with the ECU and use it to replace the stock engine harness (consisting of wires and sensor).

Thanks Guys. Based on my reading of the GCR, I agree that we can use any ECU but still must keep the AFM.

Can anyone from the ITAC confirm Steve's undertanding of the replacing of the engine wiring harness rule. Based on ITCS rule D(1)(a)(6) &(7), you can modify or replace wires and connectors in the engine wiring harness and for any changes to the MAP and TPS. In addition, other existing sensors (other than AFM) may be subbed for equivlant unit. So what if I modify and replace all of the wires in the engine harness....is this still legal? Just want to be clear on the rule before I make any purchases. Based on the literal reading of the rule, if I replace the engine wiring harness as one unit with connectors, it seems to be the same as if I replaced each wire seperately in the engine wiring harness with connectors.

Just seems odd that they would allow us to us any ECU system that we want, but could not use the recommended wiring harness with the stock sensors to run the upgraded ECU system.


Thanks again.

[seckerich]

You go Jeff!!

Just show me the word "remove" in the rule and I am with you. All I see is modify and replace. I like your read better.

[JeffYoung]

To me, it is the replacement of an assembly - the engine wiring harness. You are taking the old one out and replacing it with a new one.

Yes, I am focusing on the word replace, but I think that was the intent of the rule. It makes no sense to be able to replace the old harness but have to leave it in there.

[seckerich]

Back to Waynes question: Remember that the engine harness also contains other circuits through the connectors under the dash. Wiper motor, coils, etc. Can't just replace it. Through the firewall you need:
AFM
Water temp
Ambient Air Temp
TPS
MAP
Injector leads

86-88 has a on/off switch for a TPS and a resistor to drop the injector voltage down. Most aftermarket systems need the 89-91 components to work right unless you do a load based map.

[waynehussey]

Thanks Steve.

[Eagle7]

Back to Waynes question: Remember that the engine harness also contains other circuits through the connectors under the dash. Wiper motor, coils, etc. Can't just replace it. Through the firewall you need:
AFM
Water temp
Ambient Air Temp
TPS
MAP
Injector leads

86-88 has a on/off switch for a TPS and a resistor to drop the injector voltage down. Most aftermarket systems need the 89-91 components to work right unless you do a load based map.

The 86-88 has a limited range TPS. The 89-91 has both the limited range TPS and a full range TPS. Either configuration may be replaced per the ITCS.

I believe the 86-88.5 low-impedence injectors with resistor pack work just as well as the 88.5-91 high-impedence injectors without resistor pack.

My experience is limited to Megasquirt, which is MAP-based (speed density).

• A CAS signal to the ECU is required.
• Ignition signals from the ECU to the ignitors are required.
• Electrical connection to AFM is not required for 89-91 harness. The fuel pump signal is sourced from the AFM in the 86-88 harness.
• A signal from the ECU to control the fuel pump is required for the 88-91 harness.
• BAC (idle control valve) control from the ECU makes life in the paddock much more pleasant.
• TPS is not really necessary. Acceleration enrichment based on the MAP signal is workable.
• Ambient air temp should be clarified as intake air temp.
• MAP can be an electrical signal or a vacuum hose.

[tbtapper]

I have been pretty happy with the unit that Chris Ludwig pioneered. That unit IS a modified stock ECU so it required no modification to the stock harness.

After I stopped "fixing" things I knew nothing about and just relied on the tuning parameters of the ECU my car started to run way better and much more reliably.

The ECU can modify virtually all the control parameters that the tune the car as well as logging them for subsequent analysis. I have connected my Innovate LM1 AFR unit to input into the logging channel so that I can review AFR/rpm/pulse width/temp.

I have finally managed to get the exact AFR I was hunting to hold steady all the way down the RA back straight. It has made a big difference to how my car performs.

Early on I sadly realized that I was not an intellectual candidate for the more exotic ECU systems nor did I have the financial resources to make an installation a success.

Now if only I had a 5.12 and could afford new Hoosies for every race . . . .

Travers
ITS19

[wrankin]

To me, it is the replacement of an assembly - the engine wiring harness. You are taking the old one out and replacing it with a new one.

Yes, I am focusing on the word replace, but I think that was the intent of the rule. It makes no sense to be able to replace the old harness but have to leave it in there.

Pardon the rehash, but what is the common practice/enforcement here? I tend to agree with Jeff, but for a different reason. Replacement, without specifying a what constitutes a valid substitute part, implies that deletion is acceptable.

E.g.: "I am replacing certain wires and connectors in my harness with very very thin wires", or alternately "I am replacing them with air".

Thoughts?

-bill

[JoshS]

Pardon the rehash, but what is the common practice/enforcement here? I tend to agree with Jeff, but for a different reason. Replacement, without specifying a what constitutes a valid substitute part, implies that deletion is acceptable.

E.g.: "I am replacing certain wires and connectors in my harness with very very thin wires", or alternately "I am replacing them with air".

Thoughts?

-bill

You can't replace with air. So asssuming that the original harness has 50 wires in it, but your new one has only 25, you will be losing 25 wires. You can't do that.

The philosophy is that you can:
A) Add or replace both the TPS and its wiring
B) Add or replace both the MAP sensor and its wiring
C) Substitute worn, abraded, or otherwise undesirable wires and connectors in the original harness with new ones so that they are more desireable.

That's it. You can't gut the harness is the point. That also means that you can't remove the entire old harness and replace it with a new one unless all of the same wires going to all of the same places are in it.

[JeffYoung]

It's been an accepted "interpretation" for a long time that you can replace bushings with air.