yeah ive been wondering this for a while. i mean the rotor housings are aluminum(ok chrome coated) and they have to deal with apex seals scraping over them and bear the bulk of the forces and thermal stresses of combustion.

consider how aluminum happy and wiegth conciensce the mazda engineers where when the designed our cars, why didnt they go with aluminum side housings. i mean if aluminum will cut it for rotor housings, i dont see why it wouldnt work for the side housings, plus you wouldnt have the known issues of having dissimilar metals. it could probobly reduce the frequency of cooling seal failures becuse the all aluminum engine would expand/contract at all the same rates, putting less stres on the o-rings.

it just seems kinda backward like making a boinger with an aluminum block and iron heads???????

so why is it this way???

 

yes i know that racing beat makes aluminum housings but i want to know why mazda didnt do it, or what the advantages (if any) of steel side housing are.

 

weight and heat transfer....

 

Weight isn't an advantage of steel side housings.

Would the wear risistance of steel-vs-aluminum have anything to do with it?

 

yeah i was thinking that about the wear resistance, but the rotor housings have to get more abuse and they are made out of aluminum.

 

I always wondered why they aren't aluminum. If they can make a suitable contact surface to for the apex seal on the rotor housing, then they should be able to do the same as Racing Beat did, and make a suitable contact surface on the side plates for the side seal. I'm going to email RB and ask them if they know why Mazda didn't do it.

 

Andrew I was thinking the same thing. My only guess is that the 13b is already lighter than any engine it's compared too however; if Mazda ever does decide to build a Renesis version of a 3 rotor, then they could use aluminum side plates to make that engine lighter.

Oh you may want the mods to move this to the rotary performance section because you will get alot more replys.

 

The rotor housings are not 100% aluminum.

They start life as a hoop of steel sheet. This hoop is formed into the shape of the inside of the housing, then the aluminum is cast around it. The steel is later chrome plated.

Mazda apparently felt/found that simply chroming aluminum was insufficient. Frankly I am surprised that the steel/aluminum combination works at all, given the problems of galvanic corrosion and differing heat expansion rates.

But I suspect those problems do exist, and it would be a serious bitch to try to sheet-metal coat the sides of a side housing. A hoop is one thing, but a flat plate is something else entirely, heat expansion wise.

Mazda *probably* could do it today, but there's the problem of operational inertia... you can't just use your old iron casting forms and switch to using aluminum.