kento1

Not sure if this should be in another section of the forum, but I wasn't sure where else it might apply, and I own an FD; plus, the turbocharging question would apply to FD owners. However, if the moderators feel it should be moved, relocate at will...

I spoke with Barry Winfield yesterday, who got to drive the RX-8 in Japan for C&D magazine. He stated that the Mazda engineers told him that turbocharging the Renesis engine would be difficult, due to the low exhaust temperatures from a turbo rotary having problems heating the cat con properly for emissions. I realize that the turbos will probably take a lot of the heat before it reaches the cat con, but the rotary's exhaust temps are far higher than any piston engine due to the higher number of power cycles per "crankshaft" revolution. And either the turbocharged FC or the FD are proof that it works. Why would the Mazda engineers say this?

Nonetheless, he said the car was extremely fun to drive, although it lacked low-end torque, especially compared to the FD (naturally.....aspirated?
.....sorry.) What got my attention, though, was the fact that he said Mazda will be introducing a new RX-7 in the near future....

DaedelGT

I don't get this low heat crap at all...

BoostCrzy

bring on the 4th gen!!

artguy

cheers to boostcrzy

bring it on!

RX7Elmo

I shall wait for the 4th gen RX-7

My question is would the new rx7 be turbocharged? it seems that a lot of japanese supercars are straying away from the turbocharging concept and to N/A power. Probally because of emissions etc...

Danny

bureau_c

Anyone know how the exhaust temperatures of a side-port rotary compare (at least in theory) to the previous generation of motors? I remember when the MSPRE was first introduced in the RX-01, there was some discussion of the possibility of turbocharging it, and some were of the opinion that for one reason or another, the side exhaust ports were less "turbochargable." However, others have refuted that. It would be a shame if they didn't put on a turbo simply because they would have trouble making the cats work right...don't they know most of us will just yank 'em off anyway? :-D

jds

bajaman

Well, evidently from all we are reading and being told is that the exhaust gasses from the Renesis are much, much cooler than the 13BREW. And heat DOES play a part in turbocharging. Look at big diesel rigs, they have EGT gauges and have to make sure the exhaust gas temperatures remain high, I have always been under the impression it makes their turbos work better (?).
Maybe there is some related deal here.

Okay then, so scrap the turbo and put a blower on.
A supercharger, while sapping a lot of hp, is THE ticket for increasing low end torque. And of course once boost is being made, the hp loss is a non-factor.

I still think the ticket for the 4th gen is a NA 3 rotor tuned to deliver about 350 hp. Keep the weight down on the car, keep it under 3000 lbs. and it would be a rocket, without all the problems associated with turbocharging.
Let's face it....GM, who spends billions on R&D and all that ****, just doesn't go the turbo route very often, and not for long when they do. The bean counters have studied this ad infinitum and the end result is it is better to make NA hp from an engine longevity/warranty cost point of view.

For that matter, what is the possibility of a Renesis technology 3 rotor?

BoostCrzy

3rotor renesis??...hmmmm....yea....id ride it!....although the mystique of the turbo has unparalleled qualities....i think a new way of reducing the emissions "pre-cat" would be a better idea than working around 30 year old technology.....catalytic converters are played out!

nrolfes1

i think mazda got bit too hard on warranty and reliability with the fd twin turbo i don't think they will go that way again anytime soon.

and the engineers comment makes perfect sense. today powertrain developments first priority is emissions and engine power will hereafter always fall on the wayside. theree are just too many government and california regulations to make it otherwise.

could they do a turbo, yes , but it would be risky and the FD is the last vehicle that will ever be designed for the enthusiast who is willing to maintain and repair his vehicle at the cost of decreased reliability and the benefit of unparallelled bang for your buck.

mark57

...from what I've seen. The FD's sequential turbos are just too damned complex, power sapping, and breaking the motors....look at the all the vacuum lines, air solenoids, and not to mention the stock intake, I/C, and exhaust. Yeah, our 13BREWs are environmentally dirty and fuel inefficient - that's how we make power w/o breaking. I think Mazda is onto something w/ the Renesis and it will get turbo'ed or blown by the factory or in the aftermarket. I want to see an FE. Oh happy day for those who will obtain them. Doubt I'll buy one; got way too much $$$ tied up in my '93 making it the way it should've been made........

peejay

You need to understand the problem.

Turbos suck heat away from the exhaust. This is bad for emissions, because modern engines run "cleaner than ambient air" once the cat is warmed up, so the only place to reduce emissions is on a cold start, and you do that my making sure the cat lights off right away. This is why Subaru's new WRX has a converter before the turbo, and almost all new cars have the converter bolted directly to very tiny stubby exhaust manifolds.

The side port rotary is much more thermally efficient than a peripheral-exhaust port rotary. It's practically like a piston engine. That is to say, the side port rotary doesn't have the super hard, super hot exhaust. The hard/hot exhaust of a peripheral exhaust rotary has nothing to do with the number of cycles, but the fact that the port opens pretty early, while the charge is still burning (the rotary's slow-burning characteristics due to the poor chamber shape make things worse) and the placement of the port is conducive to burning/unburned mix blowing out and continuing to burn in the exhaust. This is also why the peripheral exhaust engine is so hard to clean up emissions-wise.

Putting a turbocharger on a side port exhaust rotary should be very similar to doing a piston engine, ie you'd require a much smaller exhaust side since the side port removes the one advantage rotarys have traditionally had for turbocharging - a surplus of exhaust energy. For an OEM, turbocharging any engine is extremely difficult because of the emissions hurdles involved. Aftermarket installations are by no means impossible.

A 3-rotor is probably also out of the question, as it automatically makes 50% more pollution. Emissions standards on the OEM level are total emissions, not a percentage, so larger engines have to be much cleaner relatively speaking in order to pass.

madaz07

i saw in a magazine that they were making a turbo version but a limited amount though

added bit: oh yeah BRING ON THE 4TH GEN

Wargasm

Emissions laws are tough and if they want to sell the cars they have to first meet the requirements.

BUT

They aren't selling one to ME unless it makes the power I want. I think that there will be a few more buyers of the RX-8 if someone figures out how to put a turbo on that bad boy in the aftermarket.

I would plunk down the cash on an RX-7 replacement right away if it came with a 3 rotor, but I don't think Mazda has the ***** to do that.

B

Project84

This would go to the Other Rotary forum if they move it.

A turbo Renesis would kick ***. The car is ugly, but they are shooting for 255hp on the stock configuration. I think if you give it a little time, people will figure out how to manufacture better after market stuff like exhuast systems. We should start seeing the same type of performance upgrades that we have for 13Bs. It wouldn't be too difficult to make a turbo exhaust manifold and plumb in a turbocharger and intercooler. it may take a bit longer to determine whether or not there could be a better port configuration, but most of the same basics will apply. More air needs more fuel that results in more power. Less weight, and less resistance will equal more efficient power sent to the rear wheels.

peejay

You're right. A 3 rotor of the same rotor size would automatically pollute 50% more, generally speaking.

Mazda also has said that they'd never again allow one of their cars to be branded a "gas guzzler". While the side port exhaust does remarkable things for thermal efficiency, the Wankel is still way behind piston engines due to surface/volume and adding more rotors is not the way to go. However, if they were to make the rotors wider, like with the stillborn 15A engine from the mid-70's (90mm rotor width) or if they went to something even longer (100mm / 16A (1635cc rotary) perhaps?) the S/V ratio would get even better. Making a longer 2-rotor makes much more sense, engineering-wise, than a 3-rotor.

Probably wouldn't make much more HP, that is limited by port size/shape/placement although the RX-8 engine may be RPM constrained before the ports reach their limit, in which case more displacement would mean more power. But mainly you'd have more torque for blasting through the apex and down the straight

Engberg

Turbos are simply a trubine as you all know. Turbines are spun by the kinetic energy of the gas. The higher temperature the higher the energy. Basically, what goes in, comes out cooler on the other side as it has to to conserve energy. The hotter the gas the more KE and the more you'll spin the turbine (with-in limits of the materials that the turbo is made of) So if you put turbos on a car that makes just enough heat in a N/A setup you'll never have enough heat to light off the cats w/ the turbo in place. Just my thoughts on the heat/turbo debate. (my first post )

m477

Why was the 15A project in the 70s abandoned?

When the FD was under development, they originally wanted to give the car a bigger NA engine, so why didn't they use a bigger 2-rotor then?

A longer 2-rotor sounds like a good idea so far, so why wasn't it pursued in the past, and what makes it more viable today?

Also, would placing a cat before the turbo like the WRX be a practical option for the RENESIS?

peejay

They killed the project because of the first Arab oil embargo. Rotaries were heavily fuel inefficient back then due to many factors, not least of which was the fairly primitive emissions systems of the time.

Just like the killed the 21A/22A... they were "big block" rotaries meant for a super sportscar that was meant to go head to head with the 240Z. That got nixed, so instead they made a smaller, lighter car based on the RX-3 and its 12A engine, we call it the RX-7.

m477

But it still worked out okay for Mazda, since the RX-7 was so small and light, that even without a huge engine it produced similar performance numbers to the 240Z. If only more automakers would realize this nowadays.

Oh wait, then they would lose the lucrative baby boomer market by making a car that's too sporty. Nissan's gotta move those 30,000 Zs they're making each year somehow...

Rota_Motor

just a couple of things, the 15A was abandoned because of the oil crisis crap, 13B's really only just survived.

but these days it would be more successful, because there is now a very big relaltively % of rotor lovers out there.

I mean look at this forum, and many other, people are straining to be the first to see/drive/own the RX-8s, or any new rotarys.

peejay

I don't want any cars with airbags or motorized seatbelts.

Even my '85 is suspect because it has a "too modern" feel to the interior. Blech.

Whatever happened to simple gauges, *****, and metal dashboards anyway?

- pj (born 40 years too late)

HeatTreated

FYI: the new issue of SCC has a quick Technobabble write up on how and why gas mileage has improved on the new Renesis side port design.

peejay

Is it just a recycled article that they ran 2 years ago?

Bridgeported

I like the rumour of a 14C (or 14B would make more sence I would think) Renesis engine for a 4th gen Rx-7.

I would love to see an NA Renesis based 3rotor. You can always add a turbo, but you can't always add on more rotors quite as easily. As you guys have said though, that's 50% more emisssions, plus more development that would need done.

Second choice for 4th gen engine would be a 14C (?) single turbo @ 8psi.

peejay

If they made an engine with 85mm rotors (see no reason why to bother...) it would be a 1389cc engine and therefore a 14A. Mazda never made a "1.4l" rotary and therefore it would be a 14A, not a 14B or 14C.

The 13B is called a 13B because there was a previous 1.3l engine in the R-130 Luce called the 13A. The 13A chares no relation to the 10A and 12A, while the 13B is simply a stretched 10A/12A. There are no rotary engine families, the letter is simply there to distinguish the engine from different previous engines of similar displacement.

If they made an engine with 90mm wide rotors, it would be 1472cc or 1.5l, making it a 15A. However, since they already did make a 15A in the 70's on an exploratory basis, they might call a new engine a 15B.