MRWEST's 73 RX3 Coupe Discussion Yarns

[anglia4]

OK forgive me for not knowing anything at all about rotaries...

What holds the layers of housings together? Surely there's not huge big long bolts from one end to the other?

[Raizer]

4 hours ago, anglia4 said:

OK forgive me for not knowing anything at all about rotaries...

What holds the layers of housings together? Surely there's not huge big long bolts from one end to the other?

There is indeed huge big long bolts from one end to the other!

[MRWEST]

19 hours ago, oldrx7 said:

Didn't realise the 'fat' plate of a 20b is the same width as a housing.  I learnt something new today.

Neither did i till recently haha, needed some work done to it so left it out for now.

[MRWEST]

18 hours ago, anglia4 said:

OK forgive me for not knowing anything at all about rotaries...

What holds the layers of housings together? Surely there's not huge big long bolts from one end to the other?

Yeah what @Raizer said haha. Pretty buzzy alright!

[440bbm]

14 hours ago, Raizer said:

There is indeed huge big long bolts from one end to the other!

yes, and also on decent builds there are equally extra long larger dowels to hold everything rotationally in line and not twisting. So the bolts just clamp them all together, and dowels take the strength. 4/6 dowels for 400+ and all dowels for responsible builders that just want it all haha.

[oldrx7]

19 hours ago, anglia4 said:

OK forgive me for not knowing anything at all about rotaries...

What holds the layers of housings together? Surely there's not huge big long bolts from one end to the other?

Good video of a 13B assembly - fast forward to 9.45 to see the huge big long bolts from one end to the other going in.

 

[dabuzz]

Those MFR air boxes are dope - get a few HP gains too  

[MRWEST]

1 hour ago, dabuzz said:

Those MFR air boxes are dope - get a few HP gains too  

Yeah man i reckon! actually really well made too was impressed.

The whole rotary air intake over top of hot exhaust never really made much sense from the perspective haha. 

[shizzl]

Where do you source the mfr stuff from?

ivd googled it but it comes up with lots of random other crap.

 

it looks awesome 

[dabuzz]

[MRWEST]

Yeah there! 

 

He makes factory style parcel trays for rx3 as well, and the airboxs to suit 13b or 20b as well as a few other things like 10a front chin spoilers.

very impressed with the quality, Julian is a good rooster (ex kiwi that lives in auz) and turned the order round quick as !

[anglia4]

Again, excuse my rotary ignorance…

What is the second housing back for?

[Rookie]

@anglia4 Pretty sure it is a place holder for the 20b's thicker centre plate. They are rare and expensive so not having one in a mock up motor makes sense I guess.

[xsspeed]

Also rotarily ignorant and I was gunna ask same thing, is that a factory 20b thing? (im sure ive seen other 3+ rotors with slimmer/same sized plates but no idea if those are factory plates or specifically built)

[440bbm]

yeah the 20b fat plate is same thickness as 13b housing so it does work for mocking up and no tempting to get stolen etc. 

 

the newer short crank/shaft motors have the middle plate in there instead due to as above comment that the fat plate has been so hard and rare to find. = $$. 

the short blocks are all aftermarket cranks. there is 'no' factory short setup.

it used to be that short crank motors are awesome NA blocks and the fat plate for turbo HP numbers but now they have got cranks developed so good, you can make the short crank setups push massive HP.  

[oldrx7]

On 17/09/2024 at 14:18, oldrx7 said:

Didn't realise the 'fat' plate of a 20b is the same width as a housing.  I learnt something new today.

Just over on page 3.

Pics kinda show the difference - blue rx3 coupe has the fat plate and orange 808 has the smaller plate.

[oldrx]

Is the 50mm tunnel raise for the TKX box due to being 20b/angles? Or just to get it proper low?

[MRWEST]

Yep as per all of the above. Fat plate is same as housing and had it out for other reasons.

14 hours ago, oldrx said:

Is the 50mm tunnel raise for the TKX box due to being 20b/angles? Or just to get it proper low?

Yes to get the angles right for the box and motor, i believe it fits fine with 13b without cutting but cause 20b is longer and motor sitting further back the angles werent right.

So once we raised that and clearenced for the diff head which we had to do anyway figured we might as well notch the rear rails and mod the tubs so can lower it a bit more so worked out well in the end.

[oldrx]

Any chance you could post some photos of the metal work on the at the rear/boot area for diff head clearance?

[MRWEST]

On 07/05/2025 at 15:00, oldrx said:

Any chance you could post some photos of the metal work on the at the rear/boot area for diff head clearance?

Hey mate,

Photos below of what we did with diff head and rear chassis rails notch the bottom photo the rails basically went straight across at the base so weve notched it up for diff tube clearance.