For turbocharged rotaries, some engine builders use a smaller “eyebrow” bridge port since air is being forced into the combustion chamber via the turbo and does not require as large of a port. This smaller port reduces overlap and the impact on idle and low RPM power. This port job is often called a “Turbo-Bridge Port” or a “Tick-Tack Port” because the small “eyebrow” looks somewhat like a Tick-Tack.
J-Ports are an extreme variant of Bridgeport where the ‘eyebrow’ port is much larger and extends past the trochoid surface (“cylinder wall”), which compromises the water seal and requires modifications to the water jackets to allow room for the port. J-ports are typically only used on naturally aspirated racing motors
Monster Ports take J-ports to an insane level, by extending significantly into the water jacket, requiring filling some of the coolant passages with epoxy like JB Weld to allow room for the port. This is a racing work-around which provides some characteristics of peripheral ports where the use of peripheral ports are prohibited in some racing classes.
PERIPHERAL PORTING
This is the most extreme type of porting, where the side ports on the engine irons are filled and a giant hole is punched into the aluminum rotor housing to allow air to enter the engine from the outer periphery. This port provides the largest gains in peak and high rpm power, was used on the LeMans-winning Mazda 787B, and is typically only used on naturally aspirated racing applications due to the significant intake and exhaust overlap that requires an extremely high idle and results in poor low rpm performance. With peripheral porting, it is possible to get 280whp naturally aspirated at 9,500rpm out of the 1.3L 13B.
20 comments
Great article and build. As a non-rotary guy, I haven’t seen any extreme power builds that are quiet. I would love to see a 4 rotor/3 rotor big build or even a 250hp NA build but actually be OEM quiet. Is it possible??
Thank you. We are shooting for over 600whp with this build while being as quiet and streetable as possible. We are going to use the largest mufflers currently on the market so stay tuned to see how quiet the setup will be.
Part of why a rotary is so loud is that there is no poppet valve to should the port so there is a lot stronger exhaust pulse coming out of the port.
ahhh that makes a lot of sense. cant wait for the rest of the build, especially the quiet part
The exhaust port also opens much quicker than a cam controlled exhaust port.
Fantastic article. I think I finally (sort of) understand all the different rotary porting types that I have read about for decades now. This engine is going to be killer!
In my opinion one of the best rotary tech references out there period.
Why wouldn’t you radius the edges of the port to enhance flow? Seems like a no-brainer to me.
Probably to avoid snagging a seal
I the young age of 14 in 1974 when USAC was using Ported Rotory engines for Competition use in their Sprint Cars .
As far as I know , I was one of VERY FEW duing this .
They were DEVASTATINGLY FAST & HAD A WORKING POWERBAND OF 7000-12000+ R.P.M.s .
The n they Outlawed them like they did with the 426 “HEMI”s
Some body talk!!! In PR we use that in the 80 and 90! En Puerto Rico nosotros usamos eso desde Los anos 1980, cuando Los motors con mas caballaje empezaron a romper Los housing en El area del pase del aceite Denison a la torcion del motor y tambien dependia de donde estaba agarrado El motor, Esto es para Los que trabajar I motors desde Los anos 1980! Pero tambien Les haciamos Algo a Los rotors que yo nunca e visto a nadie comentar!!! Que Tenga buen dia!
Translation:
“In Puerto Rico we used that since the 1980s, when the engines with more horsepower began to break the housing in the area of the Denison oil pass to the engine torque and also depended on where the engine was caught, this is for those who work I motors since the 1980s! But we also did Something to The Rotors that I’ve never seen anyone comment on!!! Have a good day!”
What did you do in the 80s and 90s? Porting?
What did you do to the rotors that you have not seen
Yes, the rear iron can crack resulting in a disastrous oil pressure loss and oil spraying all over the engine bay. There are some tricks to prevent this issue.
What did you do to the rotors that no one has commented on?
Thanks for the comment.
I had many talks involving regard’s too what port I wanted to use. No one explained it as well as this article. Half Bridge it is, I didn’t want to compromise on the lower RPM range whist still having a Brap
I’m glad to hear the article helped your understanding of different bridge ports. Just keep in mind the major takeaway of porting can vary greatly depending on who is doing the work. You can have an aggressive street port with worse low rpm performance than a mild, full bridge port. A half bridge probably be a good idea for your goals and would safeguard a little against a bad port job, but it’s worth it to have an experienced person do the porting.
The rotary engine is a breakthrough in engineering which was destroyed by pollution devices mandated by politicians normally aspirated engines are light and powerful and will last much longer then most high performance piston engines I still daily drive my 1988 RX7 which I streetported myself and enjoy the smooth idle and tork throughout the power band. This engine got a bad deal. And yes I get great mileag.
The Rotary Engine is a very unique engine
Seems like if you had some way to independently throttle an added peripheral port, you could get the best of both port styles. Has this been attempted?
Really excited to see this build evolve & article series, you’ve got a great team behind this build,
I was wondering if you considered other modern alternative to filling block water jacket for Periph. Port, people have had issues with epoxies, but is this due to incorrect choice of epoxy, prep., execution, etc.?
Here’s some info on alternatives
https://m.youtube.com/watch?v=Z9FBcSZruP8
https://m.youtube.com/watch?v=pnSdMd4XXzQ
https://m.youtube.com/watch?v=lRjCuvLCEbo
https://m.youtube.com/watch?v=SkTHNRqZDKc
https://m.youtube.com/watch?v=egU7I3V_Gv4
This is a awesome! Thanks for your guys for posting this. When I do my build I will fallow this one. I did work with CTP and WPC with the info from you guys on another project.
Hi Mike,
How much does the cryo treatment run for the rotating assembly and housings, if you don’t mind me asking? I’ve worked out a breakdown for WPC treatment costs, but didn’t consider the benefits of cryogenics.
Also, I know Turblown makes a great upper & lower intake manifold with semi P-ports for the REW, but one thing I always wondered was: what if the ports were staged, kind of what Mazda did with the Renesis 6-port? Primaries always open, secondaries opening at say 4500-ish rpm, semi p-port opening at 6000-ish rpm. Staging either with slide throttles or double roller barrel throttles ($$$ though). This would keep near stock low-rpm idle quality and drivability, while progressively extending the torque and power curves. What do you think, worth it or too complex for the gains?
I should probably ask Turblown about this, but if intake port staging is not worth it, would a tappered semi p-port runner help increase air velocity and fuel atomization at low rpm (without choking at high rpm)? And what if the primary fuel injectors were those in the semi p-ports, would that gain any type of stratified charge effect (which was experimented on in the early developpment days of the Wankel)?
Finally, I ate up the whole hour long video you did with Rob Dahm. Lots of useful information there.
There are so many ideas I would like to tinker around and test, but unfortunately I don’t have Rob’s budget haha!
Keep these articles coming!