The e-shaft and housing would need to be modified.
At least as far as I know Mazda hasn't changed that basic shape for almost 40 years. And even the width hasn't changed anymore for about 20 years now. It appears as this is some holy size/shape that has been optimized at some point and they're happy with it and even if they wanted to change it there's not much room to play with as there would be with a piston engine anyway.
If Mazda wanted to increase torque they would either add forced induction or add another rotor.

 

i heard rumors of a 1.6 for the new rx7 that might come out. i was discussing this possible engine growth with a friend and also wondered if increasing the size of the engine would lower the rpm range. we thought also if you increase the size/weight of the rotors then that would be more energy spinning creating more ft lbs. i agree with f/i to increase torque on the current engine. how much torque does the 20b have?

 

Well if you increase displacement you automatically increase torque and power as well. (It doesn't have anything to do with weight. When you increase the effective area of a piston or rotor you generate more force assuming pressure is the same. More force = more torque = more power.) And if Mazda just increases the width of the rotors that shouldn't affect the rpm range.

 

Wow, what can I add to this very good discussion? Thanks rg and everyone else for shareing your wisdom...it only makes us new rotary people smarter.

Well, I can't add anything really...it's best just to listen at this point and keep my rotary dipers on.

If I never came to this website I would have never gotten the RX8...the rotary would have been too exotic for me to take a $25K risk on. Mazda should give some of you guys some commission on my sale.

After reading EVERYTHING and learning more about the rotary I see the honest problems with the rotary while still being amazed at it's uniqueness in automotive history. It will probably never replace the good old piston engine but I'm going to enjoy her for as long as I can.

I have said before (sorry kinda off topic here) that if the rotary ever died I would stick the chevy V8 in it but I understand now that it would really change the car's character. To match some of the good things of a rotary it probably would be best to go with a F-6 but those are rare so I'd probably just stick performance built rotary in the future.

Heck by that time I might have to give up gas and find a hydro-electric sports car that can do most of not all that the RX8 can. (Yes I know there is a Hydro 8 in the works but at 120-140HP I think I would pass on that)

Thanks again everyone for teaching me some more!

 

Dear rotarygod,

Sorry to stoke this up, I only just read your first post on this today. I do not fully understand your reason for calling the rotary a 6 stroke. If you consider the number of combustion per stroke I thought it's more like a 2 stroker. Here's a cut and paste of your chart with the number of combustion taken into consideration :

2 stroke engine (up,down) - 1 complete crankshaft revolution : 1 combustion

4 stroke engine (up, down, up, down) - 2 complete crankshaft revolutions : 1 combustion

6 stroke (rotary) engine (up, down, up, down, up, down) - 3 complete crankshaft (eccentric shaft) revolutions : 3 combustions

Therefore in the rotary, for every 3 up/downs we get 3 combustions or equivalent to 1 up/down for 1 combustion i.e. similar to a 2 stroke engine.

I also feel it is justifiable to label it 1.3L in the same way as an 80cc 2-stroke engine. 1.3L or 80cc is the size of the combustion chamber(s) of the respective engine no matter how many times we make use of it (as in combusting multiple number of times per up/down).

In terms of an equivalence. I guess if an 80cc 2-stroker can be considered 160cc (80x2) then a 1.3L rotary if you accept my 2-stroke label, then it's equivalent to a 2.6L, drinks like a 2.6L and performs like a 2.6L, roughly. That's based on combusting twice as often as a same capacity 4-stroker. I believe this is how FIA considers rotary as 2x engine capacity.

Sorry didn't mean to challenge the god but please correct this impertinent layman if I am wrong. Thanks.

-Ringer-

 

That is a typo. It takes a 2 stroke motor 1 compete revolution of the crankshaft to fully complete the combustion cycle (suck, squish, bang, blow). It takes a 4 stroke engine 2 complete revolutions of the crankshaft to do the same 4 cycles. It takes a rotary 3 complete revolutions to do the same 4 cycles. Each complete revolution of the crankshaft is 2 strokes.

 

I think you mean "It takes a rotary 3 complete revolutions to do 3 of those 4 combustion cycles. Each complete revolution of the crankshaft is 2 strokes".

I think each face of the rotor when it comes to the plugs will combust having completed the 4 cycles as it rounded the rotor housing. Each of these complete 4 cycle combustion cycle makes 1 cranksahft revolution or 2 strokes. You get 3 of these or 3 crankshaft revolutions for every 1 revolution of the rotor round the housing.

On reflection I think I understand why you call it a 6 stroker afterall. Thanks for your explanations.

-Ringer-

 

I said it just how I meant it. You need to think of each piston engine in the comparison as only 1 piston and only 1 face of 1 rotor rather than the entire rotor. This is because each face does the work of only 1 piston. For the intake to occur and have it move around to compression, ignition, and exhaust, the eccentric shaft will have rotated 3 complete times to get that 1 face completely through all of it's cycles.

 

Got it. That's with reference to 1 face of the rotor. And that is consistent with your 6 stroke label. Thanks, rotarygod.

-Ringer-

 

Can I ask a question here and I apologise if its been answered, but here goes.

As I understand, one engine revolution in a rotary engine is one rotation of the eccentric shaft. Also, the 1.3L capacity is based on one rotor face being 650cc and there being 2 rotors. Lastly, in piston terms, an engines "capacity" is based on the cubic size of each piston that undergoes the full 4 strokes in one engine revolution.

Now what I haven't been able to figure is, for each eccentric shaft rotation, how many rotor faces go through the full 4 strokes in one?

Andrew