Best rotors for street NA 13B build?
Information Regurgitator
Joined: Feb 2001
Posts: 1,995
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From: Sparta TN. United States
They sell a nice-looking set of mounts. 13B-RE & 20B Engine Brackets (banzai-racing.com) I could probably fabricate my own but for $275 I may just buy theirs.
Edit to add: I found a picture of the other side. engine2.jpg (900×675) (banzai-racing.com)
Last edited by Dak; Aug 15, 2023 at 03:58 PM.
Old [Sch|F]ool
Joined: May 2001
Posts: 12,870
Likes: 574
From: Cleveland, Ohio, USA
Aw man, I would break the **** out of those mount brackets 
It took me a lot of work to make a right side GSL-SE-to-FC mount bracket that worked. They kept cracking.... and I'd reinforce it... then it would crack again and the cycle would continue... I think my final bracket that has been working so far has like three layers of box section with absolutely no flat open areas like that to flex.
Makes one appreciate why the FC mount is so weird. It's a big beefy three dimensional aluminum casting that is loaded properly.
It took me a lot of work to make a right side GSL-SE-to-FC mount bracket that worked. They kept cracking.... and I'd reinforce it... then it would crack again and the cycle would continue... I think my final bracket that has been working so far has like three layers of box section with absolutely no flat open areas like that to flex.
Makes one appreciate why the FC mount is so weird. It's a big beefy three dimensional aluminum casting that is loaded properly.
Sorry if this is a slight thread hijack, but what oil pan did you use? Does the FC pan work or does one have to use an FD pan. I am thinking of doing something similar to your engine by using Cosmo irons but with S5 TII rotor housings and rotating assembly. If I can salvage the S5 rotors I have. If not, and I have to buy rotors, buying a new 13B-REW may begin to make sense.
I have the banzai mount, it fits like ****. I have it heavily shimmed on the driver side to get the angle of attack right in the car otherwise the motor would point towards the driverside headlight... Cant even use the poly mounts that it came with I am using mazsdaspeed engine mounts
but the mounts are beefy, I haven't broken them yet, you probably won't either. I would (next time) weld the outside seam too, these are only welded on the inside. plenty of opportunity to weld improve them.
Supposedly the new hybrid Mazda motor has a larger rotor and housing. I had commented on a YT video about it by Scotty Kilmer that maybe it was a single rotor of the 16x design, and was checked up by a reply saying it's just another wider rotor, I have no idea which is true.
If Mazda makes the rotor, seals, and housings, the aftermarket will do the rest.
If Mazda makes the rotor, seals, and housings, the aftermarket will do the rest.
Joined: Mar 2001
Posts: 31,837
Likes: 3,234
From: https://www2.mazda.com/en/100th/
so the engineers built a 4 stroke engine and just spun it twice as fast.
and you get the RC166. a 250cc inline 6 that made 65hp at 19,000rpm, that is 260hp per liter, in 1966.
https://petrolicious.com/articles/honda-rc166
The single rotor in the new Mazda hybrid is 830 cc's, times two is 1660, I'm betting it's the 16x design. A new bigger rotary engine, all one needs is plates and e-shaft.
If I recall correctly, the 16x was more efficient do to a thinner rotor (12A width) and larger "stroke".
https://www.google.com/search?q=what...t=gws-wiz-serp
If I recall correctly, the 16x was more efficient do to a thinner rotor (12A width) and larger "stroke".
https://www.google.com/search?q=what...t=gws-wiz-serp
Old [Sch|F]ool
Joined: May 2001
Posts: 12,870
Likes: 574
From: Cleveland, Ohio, USA
The numbers don't quite add up to be anything of a 10A/12A/13B geometry unless Mazda went with a irregular rotor width. I think it would work out to 91.x mm width.
Rotaries get more thermally efficient the wider the rotors get, which is why 13Bs make more torque than 12As out of proportion to the increase in displacement. The volume increases out of proportion to the surface area, so less heat gets lost. It's the same reason why an engine of a given displacement is more efficient with fewer cylinders. Automakers have pretty much settled on a slightly undersquare 500cc/cyl as being optimal for efficiency vs. acceptable powerband shape for this reason.
I mean, it would be cool as all hell if it was the same geometry, because a larger/more efficient 2 rotor would be an eccentric shaft, tension bolts, manifolds and oil pan away.... I make it sound so simple
Rotaries get more thermally efficient the wider the rotors get, which is why 13Bs make more torque than 12As out of proportion to the increase in displacement. The volume increases out of proportion to the surface area, so less heat gets lost. It's the same reason why an engine of a given displacement is more efficient with fewer cylinders. Automakers have pretty much settled on a slightly undersquare 500cc/cyl as being optimal for efficiency vs. acceptable powerband shape for this reason.
I mean, it would be cool as all hell if it was the same geometry, because a larger/more efficient 2 rotor would be an eccentric shaft, tension bolts, manifolds and oil pan away.... I make it sound so simple
Last edited by peejay; Sep 12, 2023 at 07:31 PM.
Lol, yeah, there's more involved but, Mazda has made the really hard parts. From Wiki.
https://en.wikipedia.org/wiki/Mazda_Wankel_engine
Mazda TaikiAlso known as the Renesis II, made its first and only appearance in the Mazda Taiki concept car at the 2007 Tokyo Auto Show, but has not been seen since. It features up to 300 hp (224 kW), a lengthened stroke, reduced width rotor housing, direct injection, and aluminium side housings.[32]
The 8C is a single rotor with a radius of 120mm, a width of 76mm, using 2.5mm apex seals, and displacing 830cc making up to 75hp (55 kW) at 4700rpm and 116 Nm (85 lb-ft) at 4000 rpm.[33] It has a higher compression ratio of 11.9:1 and the first instance of Gasoline direct injection in a production rotary engine, which improves fuel economy by as much as 25%.[34]
Various other technologies have been integrated to increase the efficiency of the engine further, including exhaust gas recirculation (EGR) to reduce the combustion chamber temperatures and plasma spray coatings on the insides of the housings to reduce the friction on the rotor.[35]
Changes have also been made to decrease the weight of the unit such as using aluminium side housings, which saved 15 kg (33 lb).[36]
Wankel rotors of 13BThe 13B is the most widely produced rotary engine. It was the basis for all future Mazda Wankel engines, and was produced for over 30 years. The 13B has no relation to the 13A. Instead, it is a lengthened version of the 12A, having 80 mm (3.1 in) thick rotors. It was a two-rotor design, with each chamber displacing 654 cc (39.9 cu in) so two chambers (one per rotor) would displace 1.3 L (1,308 cc); the series name reflects this value ("13" suggesting 1.3 litres), as with the 13A of the same displacement but different proportions.
https://en.wikipedia.org/wiki/Mazda_Wankel_engine
16X[edit]
Mazda TaikiAlso known as the Renesis II, made its first and only appearance in the Mazda Taiki concept car at the 2007 Tokyo Auto Show, but has not been seen since. It features up to 300 hp (224 kW), a lengthened stroke, reduced width rotor housing, direct injection, and aluminium side housings.[32]8C[edit]
The 8C engine is used as a generator for the 2023 MX-30 e-Skyactiv R-EV plug-in hybrid.The 8C is a single rotor with a radius of 120mm, a width of 76mm, using 2.5mm apex seals, and displacing 830cc making up to 75hp (55 kW) at 4700rpm and 116 Nm (85 lb-ft) at 4000 rpm.[33] It has a higher compression ratio of 11.9:1 and the first instance of Gasoline direct injection in a production rotary engine, which improves fuel economy by as much as 25%.[34]
Various other technologies have been integrated to increase the efficiency of the engine further, including exhaust gas recirculation (EGR) to reduce the combustion chamber temperatures and plasma spray coatings on the insides of the housings to reduce the friction on the rotor.[35]
Changes have also been made to decrease the weight of the unit such as using aluminium side housings, which saved 15 kg (33 lb).[36]
12A[edit]
The 12A is an "elongated" version of the 10A: the rotor radius was the same, but the depth was increased by 10 mm (0.39 in) to 70 mm (2.8 in). It continued the two-rotor design; with the depth increase each chamber displaced 573 cc (35.0 cu in) so two chambers (one per rotor) would displace 1,146 cc (69.9 cu in); the series name continues earlier practice and reflects this value ("12" suggesting 1.2 litres). The 12A series was produced for 15 years, from May 1970 through 1985. In 1974, a 12A became the first engine built outside of western Europe or the U.S to finish the 24 hours of Le Mans (and in 1991 Mazda won the race outright with the 4-rotor R26B engine).
13B[edit]
Wankel rotors of 13BThe 13B is the most widely produced rotary engine. It was the basis for all future Mazda Wankel engines, and was produced for over 30 years. The 13B has no relation to the 13A. Instead, it is a lengthened version of the 12A, having 80 mm (3.1 in) thick rotors. It was a two-rotor design, with each chamber displacing 654 cc (39.9 cu in) so two chambers (one per rotor) would displace 1.3 L (1,308 cc); the series name reflects this value ("13" suggesting 1.3 litres), as with the 13A of the same displacement but different proportions.
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