i encourage you guys to look at this thread, https://www.rx8club.com/tech-garage-...-build-244370/

he's not done yet, but its interesting to compare the wear of the stock engine vs the turbo engine.

 

whats the ratio?

 

interesting--so how much does the premix affect the heat and maybe the octane?

 

In a minarelli i found with the same heat plug a temp rise of twenty degrees for just going from 50:1 to 40:1. For the rotory you need to add the omp injection oil amount and the two stroke you throw in.
There are a lot of variables to consider as well.but for a mix of 200:1 10.4 ounces ofoil with a fuel tank to be mixed followed by the amount the omp throws when at wot as well.
And you can find out the ratio of mix that is getting burned.

 

i did that once--formulated the total--during a track session and it came to about 50:1. I premixed 1 oz per gallon for that event.

Again interesting.

 

There are a couple of original high mileage NA engine tear downs documented here, it is interesting to see the differences.

 

no, that's an incorrect assumption

there are many reasons why this might occur, but saying that it flows more as a result is just (to put it nicely) a hail mary ....

 

has anyone studied the centerport flow? There are backspaces and sharps edges all around. votexs and such are probably occurring? Dont tell me Mazda did exhaustive study on centerport flow---they probably did on the positioning and shape--but the port itself looks like it could be massaged some?
Who are the airflow experts out there?

 

What are these "many reasons" ?

 

Team is taking a bit of a time out Brett.

Not sure if he'll ever respond

 

Hahahaha

 

i've collected every rotary SAE paper from NSU to the Rx8, and its a bit puzzling, with the exception of the paper about the FC NA exhaust inserts, the exhaust system is barely mentioned at all*

the exhaust is barely mentioned, even on the SAE papers about the racing engines, of which there are 3-4, the competition prep manuals only mention the exhaust in an "you should have one, here is the part number" way.

even the R26B paper, fails to mention the exhaust.

why?

well there are two conclusions that spring to mind.

1. it doesn't matter much.
2. the R26B has some secret magic, you need a cape and appropriate hat to view

to go one step further (out on a limb, and then out in mid air...) i think most of the rotaries fall into the 1st group, it doesn't matter.

even the R26B has a pretty pedestrian exhaust, its just a 4-1 header into a small straight thru muffler, using ~4" piping, my fist doesn't quite fit...

so the Rx8 center port? they probably added the baffle, because it didn't work without, and then went to lunch...

speculation of course, it could be like the NA FC, where you **** up the whole thing by bolting a header on it.


*there actually are a couple of primary pipe length vs VE graphs

 

thanks for the info--this engine is different......with no overlap ( intake port/exhaust port) and internal EGR, getting the exhaust OUT gets to be very important for us boosted guys.

Searching some very old threads--it seems GuitarJunkie did some work on this before he left us for a better place.?
It probably would not result in much, if any, improvement but 1%-2% here and 1-2% there does add up.
What do you think Brett?

 

Well my experience is lots of work for dick all result so maybe i'm biased on that

 

Lol---understand.
I think the divider does need to be there Appreciate your hard work contribution.
Because of this thread--i got to thinking about the centerport ( I know--oh no OD is thinking again)--and I started studying it more closely.

I think I may have hit on a discussion point concerning this port and its contribution to the heat the side seal is exposed too.
Its called "vena contracture" and the vortexs that develope because of it.
I believe the centerport developes these vortexs within the 7 mm backspace directly outside the port. These vortexs could trap heat( very little airflow) in that particular area--which could affect the corner/side seals also? This is also a space that appears to be mostly cooled by the oil?
Interesting to me.

 

Here is the exhaust port work we did, I don't have a close up of the intermediate housing. But doing this actually opens up the port quite a bit without drawing it out more.

As you can see below the racing beat template calls for the lip of the port to be ground out at a 90* angle. That's all I did on my first build but I knew more could be removed.

So on this build we took it a step further and opened up the inside of the port and smoothed it out. We blended the sleeve in as well, its really hard to see, sorry for the crappy pics.

Racing beat template:



Opening up the inside more:



Inside:

 

Here is the inside of the port with just the RB template.

 

I moved the entire sleeve forward by about 6mm to align the radius on the back on the sleeve with the port . I also cut out approx. 25% of the divider area directly below the port (yes you could seee the other chamber) . I thought this would make it flow much better . But i think anything i gained in getting better flow was counteracted by the crossflow into the other chamber.

 

thanks for the pics Shady---you can see the recession pretty good in the last pic.
Maybe pulling the sleeve forward is a good thing to do( filling in the back space), just keep the spacer?

A port doesnt want any sharp edges or any back spacing ( almost like a reversion thingy--but not).
No doubt in my mind that this port could be massaged to function a little better.
Maybe this is contributing to the port retaining heat also?
Who will be the first to do this?
In my book if I ever need another engine....

 

i agree completely. IMO anything you can do to help the exhaust port flow is good.

i'm just saying that the engineers seem to treat the exhaust as something really simple.

actually i looked at MGB headers and they do a 2-1+1 header. the siamese ports get a header tube that is separate from the other two, and maybe this works on the Rx8 engine too.

the outer ports get a tuned length header, the center ports don't

 

Fixed that for ya!

 

Nooooooooooooooo!!!!!!!!!!!!!

 

ohhhhh the inevitable rotary rebuild... lol
TBH, I'm surprised the bridge port hasn't given up on me yet...I'll be at 40k miles by deals gap...

 

i think we are learning more about this engines particulars--seems to be more success now.
I may have just jinxed myself!

 

Minor thread jack but how's your bridged Renny doing btw?