wakeech

the oversteer in the WRC is, again, from momentum, and not power. i've been into the WRC, and it's tech, for a few years now and really, on the asphalt the only way you get oversteer is when you set the diff to throw all the torque to the rear wheels, effectively makin' it a RWD car (a la Panizzi at last year's Corsica Rally, doin' the big *** doughnut at forget-the-name-of-the-big-hairpin)...
the reason that WRC has been dominated by AWD for the last, what, 20-25 years is because it simply distributes the accelerating force to all four wheels... on a loose surface, that's surely double the amount of available acceleration in comparison to a RWD or FWD only car...
in a road race, however, often there is sufficient grip in the driven wheels that distributing that force more equally about the 4 wheels doesn't garner any significant advantage, and adds all the weight and complexity of the drive system.

anyhoo, back to the RENESIS... i completely understand now, thanks for untangling the web of "sides" "ports" and "perhiperals" you seemed to have weaved in the first post... i really had little idea what you were talkin' about.
thanks.
pertaining to that, i also have the same concerns about the possible 90mm wide rotors that are rumoured to be in a higher powered next model RENESIS... the ratio of port size to combustion chamber volume is down, and it'll be interesting to see how taht problem would be solved... supposing of course they will make wider rotor'd engines
then again, as i said earlier, the chokin' of the engine in the mid 8k rpm range may just be from inefficiencies in the induction side runner system, and may have nothing to do with the ports at all...

Buger

Good point about the exhaust port area and increased displacement SlideWRX, the exhaust port size will probably not change very much (if at all) for the proposed 15B.

Even if the exhaust port size does not increase, it should not have much of an impact on a small 10mm increase of the chamber width. Note that the 1.3L renesis already increased the exhaust port area approx 100% over the previous 13Bs and exhaust efficiency is very good.

In the long term future, I don't think Mazda will increase the width too much more. Mazda had already experimented with a 15a (15mm eccentricity, 105mm generating radius, 90mm width) in 1973 so a new 1.5L renesis will not really be breaking new ground in terms of it's dimensions. Mazda was also going to experiment with a 22a (18.2mm eccentricity, 127mm generating radius, 95mm width ? ) but the oil embargo in the early 70s killed both the 15a and planning of the 22a.

Buger

It is interesting to see how Mazda changed the intake system on the renesis from 1999 to 2003. The original design in 1999 had 3 seperate intake paths and 3 different dynamic effect lengths. The 2003 design has only 2 seperate intake paths serving the 3 different dynamic effect lengths. The press kit diagram of the intake seems to show at first that the all of the paths are interconnected. Not many people know that they are not. See below comparison of the 1999 and 2003 intakes.

Brian

SlideWRX

Buger, I think you're right - the ports are so much better that with a 10-20% change in width it shouldn't matter much. It is probably more a matter of tuning the intake/exhaust manifolds. I think I'd rather see a third lobe, just for the huge increase in power. Considering two lobes make 250 hp, three should make ~375! Aw, heck just go for four lobes!

Tom

wakeech

(lobes??)

anyhoo, i've got another idea to bring this thread back to the fore: does anyone know how exactly the 5+6th ports on the RENESIS will be actuated??? they'll again probably be (what'd they call them...??) rotational valves again, as they were in the 13B, but how will they be controlled, and by what??
in the previous 13B, they were actuated by a mechanical system which directly applied exhaust back-pressure to two small push-rods, which then rotated the valves (which are like tubes with holes cut in the side to match up with the ports they open) to open the ports... well, alright, i've never seen or touched this system all apart, this is just what i get from 'net readin', so i could be way off...

in ANY case, does anyone know if these extra ports will be operated mechanically, or electronically, governed by the ECU???? that would be pretty neat... :D

MWG

If they were electronically control you could change it with maybe a new ecu or switch. That is a good question.

Buger

It is interesting that we are hearing rumors of a 300 hp Mazdaspeed RX-8 or next gen RX-7. People are speculating whether the increased hp will come from a supercharger, turbocharger, increased displacement, etc.

We have already heard the rumors of a 10mm increase in rotor width but that alone would not seem to explain a 50 hp increase from the current renesis.

How do guys think Mazda might get the 50 extra hp?

Brian

Buger

No guesses anybody? It is possible that the compression ratio may go up to 10.3:1 or something. I believe it is pretty common for other makers to take the same engine from their other cars and up the compression for their top of the line performance cars.

Perhaps the reason why the estimated horsepower went down from the RX-Evolv's 280 is that they lowered the compression a little to erase any reliability concerns for their new engine. It is interesting that there was not a single leak about the compression ratios of the evolv or pre-production rx-8s. Hmmm...

fritts

Buger,
What they may end up doing is taking some of the linear torque band out, run a different type of intake that is only setup for high rpm running. Seems to me that you could clean up the intake track and add a few horses on the top end. Problem would be you now have a peaky engine but you get a higher horsepower. With this the redline could have been changed and then the gearing raised to give fast times. Compression ratio could also be another option. I believe rotary news said something about there could be some porting that could be done to raise RPM. Maybe a conjunction of many things to get the 300hp. I think they will not FI the engine though. Can't wait to hear the renesis at 10k or even maybe 11k. hehe

Buger

I also think that Mazda will probably tune the intake a bit to improve the high rpm breathing. The ports may be a little more aggressive unless the difference is too minor and Mazda wants to bring some costs down by using the same side housings.

If the same width rotors are used, I could see a higher redline if the intake can supply enough air. The increased weight of wider rotors would raise the rotor weight to about the same as the old 9.54 lb ones though so I don't know if the wider renesis will have a higher redline than the current one.

amgtortoise

Hmmm... intereting point in here. All, I know Mazda have not done much with their cast/forge re-tooling in their two factory where rotary parts are made to produce an all-side port rotary engine. They have just innovated their current designs due to cost. I assume their bigger displacement 13B/Renesis 2 rotor version of 10mm more per housing, will just increase their cost of producing rotaries. Since now they totally have to make new rotors, housings, eccentric shalf, plates, & R&D.etc.etc. I see this to be stewpit IMHO. I would just use the same concept of the 2 rotor-RENESIS & make a 3 rotor-RENESIS (all-motor). Since most of the tooling are already made, most of the parts are interchangeable & it's already proven that the 3-rotor works good in Japan. If they where to produce a 2 rotor that's bigger 10mm, the cost of R&D will be as much if not more to make a 3-rotor RENESIS.

A (20B) 3-rotor RENESIS w/stainless rotors (like the 2-rotor renesis) will approx. produce easily 355-400Hp@7000rpm all-motor & produce torque of arround 250-300ft.lb.@3000rpm. And, rev up to 8000-8400rpm reliably on stock Cosmo 20B eccentric. If eccentric shaft upgraded to 1 mm dia. like the Mazda 13G, 9000-10000rpm, but I'm not sure if rotor bearings riability will be good due to more component friction. Also, the 3 rotor will have the revolution speed of a 2-rotor, but with the torque of a small-block V8, thus the engine will not beg you to turn off the A/C, & other engine accessories like the 2-rotor. The 3-rotor RENESIS will seriously meet most emission standards, cost in production (the tooling it's already made!), and give the competition some serious performance competition. Since, IMHO I think this would be a worthy replacement for the Rx-7, since the whole concept of Rx-7 with sequential turbo totally failed in the US due to mechanics training & easy tampering of the engine... and now bigger displacement of just 1.4 or 1.5 liter will just be dumb .

wakeech

sorry amgtortoise, a 3 rotor just ain't happening...
it's easier to leave it 2 rotor, and simply cast wider rotors, and wider rotor housings, with slightly longer e-shafts. it's more a matter of cost than capability: Mazda doesn't need to make a 500 hp rotary motor yet. if/when they do, then they would probably step up to a three rotor.

a thought: what if, now that the EXHAUST ports are on the side, we put the a really big INSPIRATION port on the PERHIPHERAL SIDE as the main port, eh?? then with controllable secondary side ports (or maybe just one)... how about THEM apples, eh??

... i'm just surmising such a thing, as HC leakage mayn't be such a problem with a perhipheral inspiration port (now with the side exhaust ports), as it would have been in the past... i mean, the only reason Mazda moved the intake ports to the side was to try and eliminate as much overlap as possible, but couldn't move the exhaust ports 'cause the apex seals'd coke up without them there... hmmmmmmmm.... *evil laugh*

zoom44

wait wait wiat ..... say that again?!

justinm2

You can buy perhipheral intake port housings from racing beat for the current 12a, or 13b engines, but for street driving they suck, they dont make any power until about 9-12k rpm at which point they become unholy powerful. Of course these housings also have the perhipheral exhaust ports as well, maybe side exhaust, and perhipheral intake would be a different story.

wakeech

yeah, those're the racing housings...
what i mean is a wide (very wide, with those 90-100mm wide rotors) and not-very-tall perhipheral inspiration port, with auxillary computer controlled side ports... it COULD be positioned (i'm guessing) so that there'd be not too much overlap...

but yes, i am talking about an unholyly () powerful 1.5-1.7L RENESIS... for the next RX-7, eh??

Donny Boy

Buger . . . you look like a rotary nut. Congrats and thanks for a great breakdown of the rotary renesis.

amgtortoise

First of all, IMHO it's not easier to make a larger displacement 2 rotor which will involve a completely redesign of a new engine. The R&D cost will be much higher, & why would Mazda manufacturing go for "RE-TOOLING" to produce a larger displacement, the current 13B-RE & 13B RENESIS design tooling have already being PAID for, all they had to do it's to innovate, thus we got the RENESIS. I could only think of multi-rotor (3 rotor or 4 rotor) production as their next step in innovation. And, btw we are lucky for FORD executive allow Mazda to re-introduce the RX-8 Rotary engine. The RX-8 car sales will decide the fate of the rotary, otherwise they will kill the rotary engine.

wakeech

no, there would be almost no re-engineering necessary. as it stands, they would need only to add 15mm to the middle of the rotor housings, stretch the lobes on the e-shaft by 15mm each, and widen the rotors by that same amount... in all, you're only changing 3 pieces, none of which present a problem in being changed that way... it's been done before, and would be a good solution again.
the engine would then be only about 30mm longer, in reality, with very little in the way of added mass. the few hundred cc's increase in displacement would allow for a pretty big increase in power, and would be a very good candidate for a higher power rotary motor at a very low cost.

with a three rotor, however, you have to come up with new a new intermediate housing (which has two outer gears on it) that can still aspirate two rotors on either side, and a make two peice e-shafts... this adds up to more expensive components, real R+D cost, and a much much bigger engine. really, this is engine is just too expensive as a higher power alternative, not to mention too much engine for a sports car in this price range. would it rock if Mazda did someday again make a 3-rotor motor?? yeah, but i sincerely don't think it would be in their best intrests right now, especially with the considerably cheaper alternative of just making a wider twin rotor.

wakeech

whoops!! sorry, okay i'll do it again.

imagine your regular 13B, with a perhipheral exhaust port and side intake ports, but stand on your head.

now the intake is on the perhiphery, with the exhaust ports on the side... the pehiperal intake port would not be of the same shape (not so tall), and further up to try and keep overlap closer to zero... also, this would still allow for controllable side intake ports, which could come in at a certain RPM...

admittedly, this idea of a side-exhaust and side-peripheral intake is an idea that Boogdawg kinda came up with before me, but i'm thinking the ("small" by racing standards) perhipheral port would serve better as the primary port with side ports as the higher rpm auxillaries... of course, this setup would probably lend itself to a high power, rpm motor... something which would go well in an ultra-light next gen RX-7...

zoom44

ok i get what your saying although i think turning the engine over would have been easier- cause now my head hurts :p