MX-5 NC with RX-8 231 Engine

[Paul_13]

Holy (censored)ing shit, this thing is on point again. Almost feels like the ecu was in limp mode with the 5 speed box. I'm getting 48 mph instead of 55mph in 1st and 78 mph instead of 88mph in 2nd.

I changed the back box to the stainless steel toyosport one I had lying about, scared the living day lights out of some lads in a micra.
The whole road lit up behind me like a speed camera had flashed the flame was that big.

Happy with this again



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[boosted]

Just imagine a 4.4 then lol 

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[Paul_13]

I have been doing a bit of thinking...
The engine is in an mx5 which is lighter than a rx8, I'm running 17" wheels instead of 18".
Smaller /thinner disc brakes all round...
I think a 4.1 should do.
I'm really struggling to find anything other than the standard ratios for the nc. I'm going to pull the 1.8 open diff apart and do some measurements.

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[clive]

4.1 on 17's should work ok, with out working it out, this would  probably be like an RX-8 with a 4.3 .

Interesting you say the boinger weighs more, Rotary is 106 Kilo , any idea how much your removed engine weighed in at ? 

[Paul_13]

Sorry it should of read that the mx5 is lighter than the rx8.

Mx5 is 1110kg standard
Rx8 1373kg standard

Engine weight I'm struggling to find figures

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[clive]

Sorry it should of read that the mx5 is lighter than the rx8.

Mx5 is 1110kg standard
Rx8 1373kg standard

Engine weight I'm struggling to find figures

OK, still curious about how much the engine weights, any ideas 

[Paul_13]

Bare mzr block weights 76kg apparently. Then probably 30kg for AC comp/alternator etc

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[Jamie R]

Rotary is 106 Kilo , any idea how much your removed engine weighed in at ?

Seems a lot for a tiny lump, is that all in?

I remember pintos we’re around 130kgs

[re japi]

I reckon that abit + 100kg is near. Modern 2 litre four bangers are abit less.. .

Pinto engine is very very heavy lump. Even similar Volvo engines are much lighter

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[Jamie R]

I wouldn't disagree, I've never carried one, only dragged renesis + sub frame + gearbox, across gravel from under the RX8.

I know its HEAVY. I assumed the 6 speed gearbox was heavier than the engine.

I'll find out soon enough on tear down lol

[Paul_13]

Just a thought....
My throttle blip at 5k ish... It only happens when it's warm.
Would the circuit wiring be falling under heat from the coolant loop through the body?
Might bypass it

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[Paul_13]

I by passed the throttle body and seemed to of helped so far.
Also picked up a decat pipe from a rx8oc member. Got it home and it measured at 76mm on the centre section, bonus.
Going to cut the reducer off and weld the flange straight on

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[Paul_13]

Also started to monitor afr's as the engine was getting a bit warm under light throttle 4-5k. Turned out it was leaning out to 17:1.very worrying.
So far I've forced the car to run in open loop and dropped the afr target around this rpm and it's gone back down to 14.7:1 and below.
I've managed to get another maf screen to e if that helps

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[Jamie R]

Sounds like progress Paul

[Paul_13]

Sounds like progress Paul

Getting there. Spent the last week doing all the rear suspension bushes on the wifes bmw e46 touring. Not a fun job. 12 hours solid on one of the days.

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