chpmnsws6

iTrader: (12)

Subscribing to this thread. Its of extreme interest.

lazzer408

iTrader: (1)

The stand-alone got me. I was showing off. Moral of the story, don't apply 15psi at 2000rpm.

The RX-8 ECU is in the engine bay. Various Isuzus (Vehicross, Trooper, Rodeo, Amigo, Honda Passport) have the ECU in varying locations. I'll be using a '99 Amigo ECU (cable throttle) that was normally located behind the center console. I cut ~2 feet of the harness to go with it. If it fits in the RX-8 ECU box, great. If not I'll make a box for it and keep it under the hood.

As for the connections. The RX8 uses a CANBUS interface for the cluster but I'll get to that in a moment. The 8's harness at the ECU box contains the power, grounds, and relay triggers necessary to allow the Amigo ECU to function. The connections between the Amigo ECU and the v6 engine will be the same as an OEM Amigo. My particular v6 engine came from a 2000 Passport and it's ECU was under the hood. I will be splicing the 2000 Passport harness into the '99 Amigo harness but could just as easily used the Amigo engine harness. They crushed the Amigo before I could grab the engine side of the harness so I'll have to splice it into what I have. At least it'll run.

As for the CANBUS. I have a background in electronics and diving into an instrument cluster doesn't scare me. For the most part I'll be gutting the 8's cluster's electronics. The indicator lamps are signaled by an IC operating on the CANBUS. By removing this IC, or disconnecting just the lamps I need, I'll be able to control the lamps however I want. Usually the lamps all have 12v to them and the IC simply grounds the lamp to illuminate it.

The tach is a DC analog meter (like any other electronic needle tach) driven by an IC that's also operating on the CANBUS. I'll remove the meter's connection from the IC and drive it with the electronics from any generic tachometer like a Sun mini tach. If the voltages are higher or lower then what's needed, I can level-shift it using an op-amp. It will take some experimenting with the Sun tach to see what voltage it's gauge operates at. It could be something like 0v=0rpm and 5v=8000rpm. The fuel gauge works on it's own. The RX8's oil pressure "gauge" will be turned into a functional gauge by means similar to the tach.

The HVAC (heater/AC), keyless-entry/security, radio, and center display all function without the RX8's ECU. The only thing I'm not sure about is the ABS. I don't know if it has it's own dedicated computer or if it requires the ECU to function.

The (#!@$%#$) electronic steering rack and control module were removed and replaced of a Mustang hydraulic rack. No more of that crap.

lazzer408

iTrader: (1)

Well apparently I dreamt the VSS was wired into the cluster because it's not. It's wired to the ECU. The 8 has a digital readout for the speedometer so I'll be retaining the factory ECU to drive the cluster (speedo and tach), cruise control, drive-by-wire, ABS, and maybe traction control but I'm not sure if that'll work without the electric steering rack in place. All I have to do is keep the 8's ECU out of limp mode and I'll be fine. The Isuzu ECU will be wired to the OBDII port for emissions. I guess I'll have to put the original throttle pedal back in. I'll have to put a trigger wheel on the crank because the 8's ECU will control the Isuzu's idle. I'm not sure if the Isuzu ECU will like that or not.

I sand blasted the block today. I'm not sure if I'll paint it or not. Maybe silver? Red?

viperormiata

iTrader: (24)

Silver. Easier to spot leaks.

also, +1 super thread

18psi

iTrader: (76)

This has potential for win but likely to fail hard.

There isn't a more simple method to do thsi?

lazzer408

iTrader: (1)

Not until someone makes a universal CANBUS interface for driving the cluster. (Hurry up AEM!)

The only other option I have for the speedo is finding an aftermarket digital gauge and mounting it in my cluster. Then I still have all the other lights and gauges that will have to be wired into 3rd party electronics. Like using a Sun tach to drive the RX8's needle motor.

I want to keep the cruise control and I did find another cruise (Nissan Xterra) that would work with the 8's steering wheel controls but uses a cable actuator that would function with the Isuzu throttle body.

All things considered, there's less wiring if I retain the 8's ECU. They won't be fighting for control. Think of it like the 8's ECU controls the body but the Isuzu ECU controls the engine. The only complication I can think of is which ECU controls the idle. The 8's fly-by-wire throttle body serves as the IAC and cruise control. As long as the 8's trigger wheel is working it'll idle the v6 at w/e rpm the 13b idled at. That's fine but I may need to keep the 8's ECU from going into limp mode by faking other sensors. Not too big a deal.

With the Isuzu ECU in control of the idle, the 8's ECU might simply throw a code for a bad throttle body but, as critical a component as it is, it may not function without it plus I'd loose the cruise and traction control.

My best bet is figuring out how to keep the Isuzu ECU from throwing a code for a bad IAC motor. If I can do that I should be ok. I've seen many cars with vacuum leaks causing high idle conditions and they didn't throw an IAC code. The Isuzu IAC has no positional feedback. The only "feedback" for position is the engine's RPM and if it's only off ~100 rpm I may be ok.

This swap would be SO much easier in a Miata!

Pen2_the_penguin

iTrader: (4)

if its completely thoroughly cleaned and sanded, might as well just put some protective clear coat and call it good.

Ondrej

Have you looked into Honda v6 engines there is huge aftermarket support and they are prety robust motors made of all aluminum and now days you can find them in a junk yard just a thought.

concealer404

iTrader: (3)

Wow!

I bet nobody has ever thought of that before.

thenuge26

iTrader: (2)

This is what happens when you post after only reading the thread title and not the contents.

lazzer408

iTrader: (1)

It is a Honda engine. Except this one was sold as an Isuzu and has a ton of RWD transmission options. Interestingly it looks a lot like the NSX engine except for the cylinder angle. This is 75deg and the NSX is 90deg. I thought I had a source for a forged crank until I discovered that.

Impuls

iTrader: (1)

If v6, VR38DETT or go home :P
Love the thread though. I like the non cookie cutter miata swaps.

lazzer408

iTrader: (1)

Didn't fit.

Impuls

iTrader: (1)

Didn't cut enough.

lazzer408

iTrader: (1)

I'd have to build a new sub-frame. Too much work. I'm happy with this engine. It fits the car quite nicely.

chpmnsws6

iTrader: (12)

^ must own a V8 miata...

lazzer408

iTrader: (1)

That would be like a turbo GSXR. Toooo much torque too little car.

chpmnsws6

iTrader: (12)

"Just right"

lazzer408

iTrader: (1)

I got my electronics sorted out. It'll do what I need (throttle control) with just about every relay/switch/sensor/solenoid removed. The 8's ECU only needed the oil pump plugged in to keep it out of limp mode. I'll have drivability anyways.

You can apply my methods to just about any canbus-based vehicle getting an engine swap.

18psi

iTrader: (76)

thats great