That reminds me of the newer Mazda turbo rotary patent where they have small peripheral exhaust ports and valves to shut and open them, and side exhaust ports are still present.

Pretty sure Mazda wanted the exhaust flow to be somewhat restricted in the sense that it helps reduce emissions so they can get the car on the road. Also given the price point of the RX-8, they never considered turbocharging as an option when they designed it. I would expect major rework on the engine if one wants a lot of power out of turbocharging.

Agreed.... the point of implementing side exhaust ports was to eliminate overlap and thereby improve emissions.........at the cost of trading power potential. But emissions is clearlyNOT our concern in the aftermarket... else we'd be driving a Tesla or hybrid. Neither is a cost the primary driver for those of us who've gone FI ...as there are certainly other cars that return a better HP/ $$.

I do believe that there is a ceiling on the engine output which we have to respect. But...heck...if one can raise that ceiling and maintain some level of reliability..., it m/b worth it ....to some. Perhaps even changing the calculus on taking on an engine swap.

Basically just saying...seems there w/b greater value on a FI application....IFF it works.

I do think these ports would improve the potential output of a FI Renesis ....however ...remember I had to remove one throughbolt to achieve this . That seems to be ok on an N/A but with more than double the power ??????? I thought about doing it but decided it was going to be too risky and like i've said before ...the engine still wouldn't be as good as an REW.

Gotcha. :icon_tup:

All,

Seriously, I would donate some money for these kind of investigations. If 50 persons donate 100NZ, that would be a bit help, and its the fraction of the cost of a cheap night out.

Even if I kind of "shelved" my RX8 now, I love to see the progress that Brett does, but he takes all the financial risk for the benefit of all, and honestly I do not think its fair when he is sharing to the degree he does. If we all contribute with some pennies, it should be possible to keep innovation, even if our car is a small volume production car.

Thanks AAaF. Appreciate the sentiment :) Don't think It's a project I'd want to take on though.

Update :
A few months ago i had the opportunity to test my car against another strong rx8 (tuned/catless/catback exhaust) through most of 2nd and all of 3rd gear . I decided I needed to do this again to comfirm what we found on the dyno and erase any doubts I had.So I drove 40mins down country to meet up with Arbi in Putaruru (thanks again Arbi).

Result from 3 seperate runs:
Slightly less go in 4000-5500 range
Equal from 5500 to 9000 ...no difference whatsoever.

So at this stage .............. in a drag race scenario, it's just the same as any other well tuned and sorted rx8.

HOLD THE COTTON PICKIN' PHONE !!!!! Pretty sure I just found the power I thought I should have with all that extra airflow it has. Been scratching my head over this one ....how can the engine flow so much air yet make the same power. My initial thought was ...maybe the air is bypassing combustion and going straight out the exhaust . But the more I look at it the less likely that seems.
Red line PP airflow
blue line stock airflow
https://cimg6.ibsrv.net/gimg/www.rx8...28c183c6f7.png


Found a couple of loose spark plug leads and things just took a turn for the better . More to come !

Woohoo! :ylsuper:

I'm having trouble understanding. If you're getting more intake flow, the power is the same, and the AFR isn't lean, then where else would the additional air be going if not out the exhaust?
Assuming everything you're showing is accurate, good job on creating some scavenging! Nice to see new ideas being tested even if they don't work out.

I think he's saying that it might not be a "same power issue". The power just may have been down because of an ignition problem. The car could have been ingesting more air and not burning it properly (i.e misfiring, retarded timing from lack of leading plugs firing, etc)...

Yeah , that's what I'm hoping. Although the nuances are too small to see accurately via VD, I did see a def. improvement. So really need to get back on a real dyno and try some different timing. If I can get the same increase in power as there is in airflow .... I'd be very happy !

Seeing as I'm a bit coronafied ATM I decided to paint the UIM .
High high temp engine enamel and ceramic clear coat , should have done this years ago. Makes the engine bay look way better.

https://cimg3.ibsrv.net/gimg/www.rx8...020be816c1.jpg
https://cimg9.ibsrv.net/gimg/www.rx8...ec015826d3.jpg

Looks good
 

Keenly waiting for further progress on your build. I am planning to have a similar exhaust manifold (thanks TEAM and BRETTUS) made for my 8 and get a BHR midpipe. And once the time comes for a new motor.......

No bluster intended, because after all these years you still don’t understand the siamese exhaust port conundrum, not just relative to this experiment, but more so to your 450 hp limit theory. The worst case scenario is removing the divider plate, as you found put the hard way. FI makes it way worse. I would reference you to the latest patent thread, which is likely where you came up with this idea. They got rid of it on purpose.


.

I think you will have to spell that out a bit better for me Team ...what is it you are saying is happening with the siamese? If you think there is massive cross contamination between the rotors ...you really need to rethink that...I've experimented a lot and seen no evidence that this is a major issue.

Yes they got rid of it in their patent ... but I'd bet it's not for the reasons you seem to be suggesting.

I believe in the patent there is only one side exhaust port per rotor.Placed on opposite side of intake ports So the exhaust port in centre plate is no longer shared,so no divider In this configuration no cut off seal required

what's the point you are making ?

here is the thread on it for reference : https://www.rx8club.com/general-auto...-mazda-269734/

Hi BRETTUS I was agreeing with you when you said [ Yes they got rid of it in their patent . but I'd bet it's not for the reasons you seem to be suggesting.] so I think you are saying the exhaust in centre plate is not divided, I was saying its no longer divided because its only getting exhaust from one rotor There have being a lot of patents recently all configured differently .I may be mistaken

Gotya slowred...
My comment was basically saying to Team: ... even though the Siamese is a shared port with only a short divider to separate the flow from either side ..... that isn't the reason the Renesis struggles to make over 400whp with FI and I doubt it's causing any issue in the N/A engine on this thread either.

I know this because I have experimented with the siamese sleeve extensively in the (false) belief that it actually was a problem ..... everything from having virtually no divider there to the divider just covering the port to stock with several other iterations in between .... I even tried completely sealing the sleeve so there was zero chance of crossflow . I also made a high flow sleeve (with a divider) that did a good job of increasing the flow through those ports.
NONE of these experiments gave any indication whatsoever that crossflowing between the rotors is any kind of issue for the Renesis with a stock divider.

However there are still several reasons why you really don't want a siamese port like the Renesis has :
The sleeve tends to fall to bits before the engine does
The design is very inefficient due to the right angle bend and small x sectional area of the port sleeve.
Three doesn't go into two for twin scroll turbochargers so it's not so great for a turbo with a twin scroll housing like Mazda would want to use as shown in the patent.

So you mentioned that you wouldn't want to turbo this setup since going through the tension bolt weakened the engine. Ideally wouldn't adding a peripheral port enable you to get around that 400hp+ range limitation with a turbo setup if it can be strong enough? Have you looked into using GSL-SE housings? They have the coolant seals in the housings like the renesis. I believe they only have one oil injector slot and also an additional tension bolt slot near the intake. The port timing is a lot sooner than what your modified housings are, but this way you could keep that tension bolt in place at the exhaust for strength. Using these housings I believe you would have to machine the rotors to fit stronger apex seals to deal with going over the ports, especially with a turbo setup.

I'm still somewhat new to messing with the internals of a rotary, doing my second renesis rebuild currently. I was looking at doing a rew swap while I run the current engine being rebuilt, but now I am curious if I could stick with all of the engineering that mazda put in to designing the intake for the renesis. From my understanding the renesis intake design worked well for getting more torque out of different rpm ranges. The variable exhaust ports idea would be really interesting to see someone put that together, especially with a turbo setup, potentially something similar with what mazda did with the variable intake could be achieved here. I imagine if it was done right you could get close to a stock renesis motor in the low end, and then open up the peripheral in the top end to avoid the issues you talked about when going past 400hp+. I might eventually try these gslse housings with my other set of irons instead of doing a rew.

What I am unsure about is whether having all the side ports and the GSL-SE port open at the same time would cause any issues with crossflow or low end drive-ability. I have heard of others who used these housings, but then blocked the renesis side ports because of crossflow. You are saying that crossflow does not seem to be an issue, but in a turbo setup couldn't it become a greater problem or have you experimented with that? Again I would come back to trying to design a variable exhaust system to try to keep the low end drive-ability similar to the stock renesis. I want to say that in the top rpm ranges having the larger exhaust would definitely be beneficial. Maybe it would be possible to make an ssv like design that would swap between the renesis ports in the low end and the gslse ports in the high end. The greatest challenge at that point would be to make the design reliable while taking the abuse of being on the exhaust side of things.

Sure I'v looked into the GLSE housings. I discounted that idea because it's already been done and didn't really light the world on fire. Sure it resolves the 400whp issues but at the same time it removes any possibility of getting decent response. That's because getting good response from a turbo is about maintaining the energy of the exhaust pulse. Having five exhaust ports totally destroys any chance of that. BTW ...I didn't mention it above but all those siamese experiments were done on a turbocharged engine (see Brettus turbo 111 thread)

Do you have pictures of your housings before the engine got put back together. How was the tension bolt slot plugged?

No sorry . I taped the hole and used 1/2" unf plugs .

So .............
I believe I have figured out the reason this hasn't worked as well as I had hoped.
The engine is obviously flowing more air than a stock Renesis but still making the same power. For this to be happening there HAS to be some scavenging of the exhaust gas as the intake ports are opening. Meaning some of the carryover exhaust (around 10% according to Mazda Renesis paper) that would normally be carried around to the combustion phase is being pushed out the peripheral exhaust with the incoming air. This is what i had hoped would give it more power.
However , it's not making more ............. WHY ?
The answer I believe , is to do with the bridgeport . I believe the BP is allowing a lot of exhaust gas to be pushed back up the into the intake as it opens prior to top dead center. This means the air coming back into the chamber AFTER TDC is contaminated and even though much of it is pushing out through the peripheral exhaust , the net effect is that the amount of FRESH air going to the combustion phase is no more than stock.
I think that the idea would work better without the bridgeport.

I have an idea to test if this theory holds any water but can't do that right now due to lockdown.