Just wondering, what exactly makes the Renesis engine make more than 100HP more than my GSL-SE?

 

The major difference is the exhaust ports. The exhaust ports are located in the plates, apposed to the housings.

 

20 years more advancment,EFI thats 100 times better/faster,more compression,different port configuration,higher redline,ect,ect.

The HP might be significantly higher,but its all made at the topend.The Renesis' torque output is still down around where N/A 2 rotors were in the 80's, since its still a relatively small engine. And there still isnt another N/A 2 rotor out there with the SE's low,broad torque output. All N/A engines since have emphisized midrange/topend power delivery.

 

I'm attempting to replicate the SE's low, broad torque output using parts from the '70s with similar port timing and flow characteristics. I could have built an SE motor but decided to carb it for simplicity and the challenge of such an undertaking.

Hey Steve, do you think the new 1600cc rotary will have SE-like torque?

 

What is the limiting factor in RPM for the rotary engine itself?

Mazda should capitalize on the RPM capability.

Why can't they do an 8-port rotary that spins to 10K, while keeping good low-end?

 

I believe that due to the successful nature of the Rotary Engine's dynamics; i.e. unlike a four stroke engine there are no pistons to stop then go up, stop and go down, ect. The engine is constantly rotating at faster and faster speeds; creating more and more friction and friction gerated heat.

Even though you can make teh cooling system heavy duty and the cold air going in even cooler, there's only so much friction that the seals can take before generating too much heat. Also as far as I know, all the roary engine housings were made of aluminium, which has the wonderful charactiristic of one moment being solid, then one degree over its melting temp being liquid with no warning.

at least thats how someone explained it to me.

 

I suppose though, that the Rx7s Achilles heel then (Aluminum) is actually one of its strongest benefits. That metal weighs almost nothing, so I suppose its a trade off?

 

Yeah, its a very good metal to use in terms of heat retention and weight savings... the problem is that once aluminium reaches its melting temperature it doesn't soften like steel or iron, it simply goes from hot aluminium to loquid aluminium... its hell acrazy to watch when you're melting aluminium in a crucible.

 

Aluminum does not retain heat. It is known for heat transference. :-)

 

Thank you for the catch Doc ^.^ Iwas thinking of transference! I Swear! :LoL:

 

Aren't the housings heavy cast iron?

Are the aluminum on the Renesis?

 

The main thing that prevents high rpm operations isn't that your apex seals are in danger of melting, but rather the fact that even the slightest imbalance or loss of lubrication at those speeds warrants a catastrophic failure. Having the edge or corner of a rotor come into contact with a rotor housing or side housing is *bad*.

So as time went on, they found ways to
- make the e-shaft less likely to bend (which would cause the tip of your rotor to contact the side housing)
- clearance and balance the rotor better so that it doesn't contact your front/intermediate/rear housings (stronger corner seal springs help this as well
- reduce friction and wear on parts through small upgrades to the chrome coating and nidride layer as well as the composition of apex seals
- Keep the rotor following its path using hardened stationary gears
- Keep the bearings lubricated by increasing the size of the oil pump, the oil pressure in the system, and carving larger grooves in the rotor and e-shaft bearings
- increase cooling of both coolant and oil through larger / more efficient radiator and FMOC

etc.. etc..

You can see alot of these changes available as upgraded parts through places like racingbeat and mazdatrix. Over the years, these changes have been incorporated into the production engine. They still don't do the most accurate individual clearancing/balancing of the rotors, but their casting process has led to less imbalance.

The Rx8 can rev to 9k rpm without any problems on a stock engine because of these sorts of upgrades.

But the 9krpm redline does *not* explain the major increase in power. There you have to look at the increased efficiency of fuel injection as computers have gotten more sophisticated and technology has advanced. Also, as someone already mentioned, moving the exhaust ports to the side has eliminated overlap between the intake cycle and exhaust cycle. There's actually an extremely small period of "lull" there, something not found in other engines. The port shape/location was a trade-off. Peripheral ports (both for intake and exhaust) have a much more direct path, so they flow much more. They don't have the 90* bend at the end/beginning to deal with. But Peripheral ports have timing characteristics that make them better suited for engines that don't need to meet emissions standards. Slightly less efficient burn for much more flow. You could get the same horsepower as an Rx8 from a well built Peri Port race enigne, in fact you could get even more, but it sure as hell wouldn't pass emissions and wouldn't get the gas mileage the rx8 does.

And of course, the lack of overlap between exhaust and intake was very well complimented by 10:1 compression rotors. The highest compression 13b rotors ever put into a mazda 13b.

Oh, and I forgot to throw in there somewhere that catalytic converter technology has also advanced so that they flow better. Still not perfect, but from 1985 to 2005 there was a lot of time spent trying to make cleaner and better flowing emissions equipment.

So 10:1 comp rotors
+ Mods for better balance/clearance
+ mods for better lubrication/cooling
+ port re-design
+ improved friction surfaces
+ better fuel injection and fuel delivery system
+ better flowing emissions technology

= the reason that the RENESIS has power way above and beyond your GSL-SE 13b.


Jon

 

I forgot to mention better sealing to prevent compressed air/fuel from escaping the main part of the combustion chamber.

The side seals on Renesis rotors are designed quite differently from previous models to increase the sealing between the sides of the rotors and the side housings. Any increase in sealing that happens at the apex seals, corner seals, or side seals would help raise compression. It may in fact be the reason we haven't seen 10:1 comp rotors before now - they hadn't figured out how to raise the compression that high and not have it leak out the side seals/corner seals/apex seals.

Jon

 

not sure why nobody mentioned a very very very tricky and efficient intake design. That probably gave the renesis its new found power

 

Cool. Any idea what we can expect from the 1600cc engine?

 

Hearing of the 16X has gotten me more excited about the rotary since I discovered ceramics. I just hope they dont pull the plug before production. Or just as likely it never makes it to the US due to emissions issues.

 

I think they decided to call it a 16C XD just a guess that you're talking about the same engine from the new gen RX7 concept.

 

the intake manifold is crucial in the power of the Renesis

 

Turbocharged engines have been seeing peak combustion chamber pressures far greater than the Renesis for a long time now. In fact it's beneficial to have slightly larger clearances on race engines as the combustion pressure actually gets behind the seal and pushes it harder against the housing. The springs are really only there to hold things in place until things get going.

The change in side seals on the Renesis is mainly due to the side exhaust ports as far as I know.

 

This is one of the most ill-informed posts I've read for sometime. Demon, I've been reading your posts lately and am very disappointed in your lack of facts/understanding yet you continue to post bs such as above. If you are relying on someone else for the above information, find a new source. Better yet, spend more time reading and learning the facts and less time posting bad information.

The quoted post shows a lack of basic understanding of cooling systems, friction and heat mediation and metallurgy.

 

+1 for trochoid.
I missed that the first time I read it.

 

The thing that bothered me the most about DemonSpawn67 was his use of XD in every other post. It's not even a real emoticon. Is it supposed to be a South Park reference or something? Please stop.

 

That's why these Honda's are fast. What if we could have 14:1 compression...

-Ryan

 

dp

 

Lots of things make the Renesis more powerful but the key is in the exhaust ports. There is more to power than just pure flow although it is very important. Port timing plays a huge role in how much power you make and where. The Renesis exhaust port timing is much better suited to making good power. The conventional peripheral exhaust ports have too much timing in relation to the amount of intake timing that the side intake ports give. On a full peripheral port engine this isn't an issue. There comes a certain point when increasing duration on timing starts making less power.

Intake manifold is better and helps but it isn't responsible for the much greater power of the Renesis. The higher compression ratio also didn't do very much. There really isn't much more power to be had going higher in compression ratio on a rotary. More doesn't keep making more power. We aren't just compressing air inside the engine. We are also flowing it. A smaller combustion recess in the rotors means air moving from one side of the engine to the other and minimum chamber size gets to be mroe difficult. It would be different if we were just compressing it in one place as piston engines do. The intake ports are larger as well. Lots of things contribute but the biggest leap in power is due to the exhaust port location.