shams42

Any new information on the issue?

Hymee

iTrader: (1)

Nice post Richard!

shams - the newest news I see (I was offline for a while) is that this tread now has a more pallatable title!

Cheers,
Hymee.

Aoshi Shinomori

Been a while since this post has been up at the top, so I may as well attempt to get it going again. Mr. P and P had great results through porting and polishing. I am aware that Acosta Racing has done porting and polishing but I don't recall them getting numbers like this. Did P and P do something different in the way of porting his engine( I don't remember if this was talked about, and I don't have time to look through 19 pages right now) If he did mention that, have any other companies or people looked into porting with similar outcomes to P and P?

devious12

Ok great thread...now I think my brain is going to explode!

Question for anyone with the knowledge:
I understand that I will get gains from porting and polishing the engine, but what are the negative effects of having this mod done?

Thanks

G8rboy

Taking your engine out and voiding your warranty

devious12

I'm not that concerned with the warranty if my engine will perform to it's full potential. I want the most out of the engine regardless of the warranty. I plan on keeping the car well after the warranty expires. Maybe Rotarygod or someone just as knowledgable could answer this question.

Ajax

Doing it wrong could possibly increase wear on the side or corner seals if they are at any time unsupported.
It's also going to be very expensive...
If you go too large, you'll get overlap..

devious12

thanks for the quick response. I'm ignorant to the term "overlap" does that mean overlapping the time that the exhaust and intake ports are open (both being open at the same time?)

Ajax

Yes.

rotarygod

The only way to get port overlap on a Renesis is to bridgeport it.

Ajax

Isnt that untrue if you were to extend the exhaust ports to the point where they're still open when the intake is openning?

I mean, it's not the ONLY way, is it?

devious12

is that why some rotary engines have a extensive burble sound to them?

Ajax

The "wah wahs" or "brap braps" or whatever you call em.. yea.. that's port overlap..

rotarygod

Yes that's true but you have to remember that on the Renesis, if you open the intake ports any earlier or close the exhaust ports any later, the corner seals will fall into the port. This would be bad. That is why it is only possible to get overlap with a bridgeport on the Renesis. You need something for the corner seal to ride on.

devious12

thanks for taking out the time to explain things. this is my first rotary and I can't stop studying the way it works, it's extremely addicting, wish I could build them for a living!

Ajax

Gotcha. I didn't realize the timing was that tight already. So I guess as far as porting goes, the best way to go in this case is to make the intake larger while making it close later and then possibly pull an ito and bridgeport the tertiary ports after you clean up the exhaust of what we saw at SS7.

Sound about right to you?

G8rboy

I'm with you- it's such a departure from looking at the engineering of piston engines that I can't stop reading about rotaries. BTW, I hadn't looked at my RX8 book by Jack Yamaguchi (the one people got free for pre-ordering) in a while- there's some great comparisons of the various parts of the 13B-REW and 13B-MSP, including all the seals and their dimensions. I completely forgot about that section, and when I came across it again it made me think of this thread. Anyway, it's a great book about the RX8 as well as the history of MAzda's rotary development... worth getting if you can find it on Ebay or somewhere.

rotarygod

I wouldn't do a whole lot to the intake side other than just cleaning the ports up a little bit. They realy can't go any usably bigger. There are people that will make that auxillary port really large but as with the 2nd gen RX-7 6 port engine, going too big won't help. Too big can hurt power. They are already larger than my 6 port RX-7 streetports. People complain that they can't be made any larger but fail to realize how large they are already.

The exhaust leaves alot to be desired. I'd feed my die grinder on those ports for a long time. There is going to be alot of flow to unlock from them. If we port the exhaust, low end will decrease somewhat but mid to top end should greatly improve.

The intake ports could receive a small bridge. When this is done though, the powerband will really shift around because the intake manifold isn't designed for this port timing. The power peak should actually go down rather than up based on port timing and runner length. If you look at Ito's dyno, his power peaked earlier than stock. I would not bridge the exhaust. Too much heat on such a small bridge may weaken it over time.

Aoshi Shinomori

Good post, but I've got another one for you to answer. What is the reason for that huge spike in Ito's dyno. I've seen v-tec dynos for my brother's rsx-s. The jump at v-tec is around 25hp at the most, and after mods it decreases and smoothes it all out. If I remember correctly, Ito's dyno jumped about 60hp or more!! I don't understand how opening up the exhaust ports will cause that big of a jump. And I also think I remember that the rest of the dyno resembled a stock dyno, the rest of the curve seemed pretty normal. An explanation would be great.

Ajax

Well, pull the edges off the intakes and get rid of that corner blockage on the primary and maybe expand by just a little and that's all you can probably do. The 4 port engines appear to open slightly larger towards the eccentric shaft than the 6 port engines so there might be some flow to be had at like 180 ATDC, or can you not go that way?

We all saw the work the exhaust needs done at SS7. It was pretty obvious even to a newb like me.

If you bridged just the tertiary though, you'd see more top end power w/o changing the intake manifold and runners too much, wouldn't you? Or is assuming that the intake is capable of flowing more air than the engine is using too lofty of an assumption?

Ajax

I keep calling the Aux ports tertiary ports and maybe that's not the right term. I'm talking bridging the auxiliary ports on the motor, the ports that open at like 6250 RPM.

rotarygod

Look at all of his dyno runs. They all do the same thing. If he only bridgeported the auxillary ports then this might happen but I suspect he just doesn't actually go to full throttle until about 6000 rpm. He also only quotes peak horsepower numbers which is crap. All of his dyno's for some reason spike several horsepower in one small spot. He then reports this number when the average may be 5 to 10 hp lower. Peak horsepower sells product but average horsepower wins races. Remember that he owns a business.

Aoshi Shinomori

I guess that's true, are there options on a dyno to test throttle position at certain points? i.e. it might show 65% throttle on the graph, or maybe a range of like 75-90 for this section of the graph or something like that to let us know our average numbers a little bit better? I know it sounds complicated the way I'm explaining it, but I really don't know any other way. Any answers would be greatly appreciated.

zoom44

Tertiary is the correct nomenclature here!! it's mazda and the long time rotorheads that have it wrong. except one guy at mazda. in an interview one guy at mazda called them Tertiary. i made a point of making sure Wakeech saw it. i could probably find it or maybe wakeech can dig it up.

Ajax

Lol, whatever. As long as we know we're talking about the same thing, it's all good.