Originally Posted by PercentSevenC
Interesting exhaust sleeves. I'm very curious how that will turn out. Also, I see GSL-SE/RESI rotor housings. Any particular reason for using those rather than the more readily available later style housings?
Can't wait to see how you do the center stationary gears.
Edit: I just noticed the slide throttle. I've been wondering how a slide throttle right up close to the ports like that would work out. Are you going to use round holes or teardrop ones?
These are S4 N/A housings. I wasn't sure if I could succesfully modify the housings without warping them or anything so I took the cheapest and best available housings there are, S4 N/A housings. They are used, but still have a lot of life left in them. I might replace them with better ones when the engine is running and dialed in and has done some miles, but I'm a very very very long way from that.
The slide throttles will have round holes (or, well with a small cutout), because the peripheral port inserts in the rotor housings are round, and the intake manifold is also round. I'm going for uninterrupted laminar smooth flow here.
Originally Posted by Aaron Cake
Very nice. It must be wonderful to have a machine shop at your disposal.
I'm wondering why you chose that design for the exhaust sleeves? Mazda created them in the shape they did so that the gasses could rapidly expand once they exited the port. I'd expect a smaller design would be a fair restriction at higher flow levels. About the only engines that Mazda had such narrow sleeves on are the 20B and 13B-RE, which are designed as low/midrange engines.
Well, It's something I wanted to test for a while. I did a lot of flow simulation's, and I found that this sort of port doesn't increase backpressure like you would think. It does improve gas velocity however which should be good. I actually wonder if the expanding shape has something to do with the air injection system. The flow is very turbulent when it exits the rotor housing, I tried to make a straight uniform shape which should convert the turbulent flow to a laminar flow very quickly. This shape also makes it easy to create an anti reversion lip.
I think it will be fine, there is another topic about it here:
custom exhaust sleeves explained
I also looked at the 26B exhaust inserts, they also aren't as large as you would think. This is not a turbo where you need to cram a lot of energy through the exhaust channels.