In both S4 and S5, the N/A coupes and convertibles (North America) had different ECUs. Yet, they were both normally aspirated with the same engines. Does anyone know the reasoning and specific differences (other than the numbers)?

JP

 

Reasoning, in other countries, the very came in a turbo model. I guess they used the ECU from those, in the US verts... The US is so lame, always having shitty cars, and the good cars nerfed.

 

Thanks, but that's not the point of the question. I don't have information on the comparsion of turbo coupes to turbo convertibles ECUs, so I can't comment on any differences (if any). My questions remains, if the North American Coupe and Convertible were both NA, (S4 &S 5) then why the difference in the ECUs and what are the differences?

JP

 

US-spec 1988 convertible ECU (N338) runs both NA and turbo code in it.
I think it's the only one that can.

US-spec 1989-1991 convertibles all run NA code only.


-Ted

 

Thats gay, why the hell did they do it that way.. Mazda pisses me off sometimes.

 

all US coupes arent NA..

 

I think what "jpd3253" is trying to say is what is the difference between

'89 California N350
'89 Federal (non-California) N351
'89 California, Convertible N352
'89 Federal, Convertible N353

We know that the "California" is because of emission, but what about the N351 and the N353. What is the difference?

 

That's the gist of the question...What is the difference and why?

JP

 

actually to re re re-sum up the question is why the hell does having a cloth top mean you need a different computer

 

because gearing and fuel mileage setups are different.

 

So if you got a different wiring harness for the 88 and threw in a 13-bt engine you wouldn't have to swap out the ecu?

 

Yep... I did that exact thing when I had a 13BT in my 88 vert

 

That is correct.

In fact, the engine harness difference is just a matter of two pins.
One is for the knock sensor, and the other is for the 2-stage fuel pump voltage system.
Both can be ignored, and you can just de-pin the NA engine harness to make it still work.

Oh, you also need the "2-bar" turbo boost sensor also.


-Ted

 

damn that's pretty damn neato. I couldn't afford to do that, nor do i have an 88 vert. but that's really neat.

you guys rock. i wish i were you sometimes so i had a 7 that ran. but whatever i'll get her going this weekend. (hopefully)

Nite nite,
Matt

 

mark, do you know what the differences between the 91 vert ecu and a 91 coupe ecu are... because i was under the impression that they have the same gear ratio?

 

bumpity

 

Yes the gearing in the manual tranny coupes are the same as the verts (I was think on how different the auto trannys are since it seems more S5 verts are auto tranny), however I am guessing that the gas mileage map is not. The verts skated the fine line of gas guzzler tax, because of the weight.

 

hrm... if thats the case, would there be performance gains to switching out a vert ecu for the coupe ecu in a 91?

 

I'm actually sending my N338 ECU to Henrik to open and give us the answer once and for all. I don't think there is ANY turbo "map" in the N338 - there is no fuel cut w/ this ECU on my car, so I stopped boosting until I got an N332 (w/ henrik's 1.5 chip).

He will let us know after some datalogging...

 

I thought he already confirmed this?


-Ted

 

bump

 

I am guessing that the vert ECU would probably give you slight performance gains in a coupe.

 

The preceding assumptions (gas guzzler tax and gearing) would suggest this as a logical conclusion. However, it raises another question. If the vert ECU could provide better gas mileage and performance in a coupe, then why didn't Mazda just use the vert ECUs in the coupes? Which goes back to my original question, what are the differences? Do the vert ECUs control something specific to the convertible that is not engine related?

JP

 

I try and stay away from S5 RX-7s in general, so again without wasting my time diggting through manuals and compairing wiring, it would be hard to say. It could be an cost issue... simular to the N338 on the 88, or the board layouts may be different...

I know I have seen on several early 88 model Cali spec verts, they used the same two stage fuel pump setup as the Turbos, so it could be something as simple as that...

But again I try and stay as far away from S5 models as I can. They were the bastard children of the whole RX-7 Line.

 

oh come on mark... thats not fair... and arent you using an s5 intake on your car