rotary crazy

ok, lets see if I can put this as simple as possible

the reason for mazda not making a 3 rotor rx-8 is cost and market, not a lot of people are going to buy a 35 to 38 grand mazda, at least this is what mazda belives

actually the engine its the most symple thing, the suporting parts are the most dificult and the rx-8 will have to change a lot, think of NA second gen and turbo fc

a little list of the things mazda would have to change

intake system
throtle body
ignition system
sub frame
transmition
cluht and friction plate
brakes
suspension at least the spring rate
rad

the ports on the 20b renesis will be similar than the 20b, any one that has seeng a 20 b knows the center plate its thicker than a 13b, and the the central housing its fed just like the other housins, the key is that in the center plate one housing gets the aux port, in a 13b renesis we have the 5ht and 6ht port in a 20b renesis we would have a 7ht port in the center housing, in the old 20b it is just like this only diference its that the center side housing gets one small port and one large, so it is a 6 port engine , this same logic would be use for the exhaust.

maybe I should draw somethi8ng?

nycgps

iTrader: (1)

This shows how smart you really is.

Study ?

rotary crazy

the thing is, in japan the rx-8 is categorize as a 2.0lt engine car, if you go bigger the car jumps in price acording to the japanesse way of paying taxes, and you would have to retool to make diferent rotors and housins, etc. there was a reason mazda made the 20b before

jeffe19007

If direct injection is really happening on the Renesis, then with a 3 rotor Renesis, you could cut the fuel to various faces of the rotors in some manner that keeps it balanced.

Would allow the engine to stay cooler. With a fuel free jet of air passing through the engine.

Look at it as a 'rotor' way of doing the Hemi cylinder deactivate.

More milage on cruise. Cooler running.

I like it, and I bet the Mazda folks have thought of it too.

And a 3 rotor would have a home in a halo car as we have harped on before. There are halo cars all over the the car magazines for other brands. Don't think Ford and Mazda don't notice. The RX-8 chassis can go up market as well as down market.

Vrimmick

I don't really know what is wrong with going with higher displacement genius? I am sure there definitely is a market for it. BTW you should say "this shows how smart you really are".

swoope

iTrader: (5)

sorry,

he was wrong. search, then study..

beers

tmak26b

Look at a picture of the rotary and ask the question again

Vrimmick

Bigger displacement meaning bigger everything... housing, rotor, just magnify the engine by a factor of 1.3 - is it that difficult? Or perhaps you engineers already studied that?

Footman

iTrader: (2)

When you read news like this:

http://www.edmunds.com/insideline/do...ticleId=119187

It makes you wonder what the chances of a Mazdaspeed Rx-8 is like.

Raptor2k

^I really don't see the relevance. And those quotes are vague...what rules is he referring to?

Winfree

The problem is not more rotations of the drive shaft or more powerful drive shaft turning, but converting the spin into wheel spin - the heat suggests that the transmission is wasting energy, and also in front you are still driving the generator by a belt! The generator looks like a standard piston drive generator - but you waste a lot of energy with that belt system - these are areas for engineers to reconsider - there may be more effective generator systems...

RX8Maine

That is just plain wrong. First, cutting fuel to one rotor balance the motor defeats the purpose of having it there. Second, and jet of air would not cool the engine. It would get HOTTER. Lean = HOT = BOOM = hole in said rotor. I suppose you could shut off the fuel completely, but then again, why is the rotor there?

rotary crazy

the fuel consuntion of the 20b its a myth, it was as efective as the 13b, just look at the ratings, the diference its more due to the weight of the cosmo vs the rx-7, 500lbs to 600lbs to be precise.

Im sure if you put a renesis in an rx-7 it will give the same or better millage than the 13b rew

jeffe19007

RXMaine...Ok maybe I wasn't clear.

On Hemi, and several other piston engines, at cruise, they disable a couple of pistons, through whatever mechanism is popular. This produces better mileage in cruise, because you now have a 4 cylinder.

Now with direct injection, a system where you could guarantee there was no fuel, or very little, in the combustion chamber, you could do the same with a rotary.

I believe the fuel charge from the previous combustion event of that face would be insufficient for even a lean condition.

The extra rotor would still be there and fully functional when you need it. I am just providing a method of offsetting the costs of that extra rotor when it is not needed.

I would think running plain air charge past the face might be useful in cooling too. Emissions may not be a factor in cruise.

The combustion events skipped would be done so that there would be minimal vibration and stress on the engine. If that can be done. The events skipped would be spread evenly over the nine rotor faces in the engine.

I am just dreaming this stuff up. I would love a 3 rotor. Somehow it has to be made a bit more practical too. I cannot see how a 3 rotor Renesis would not have even worse fuel mileage. If they could provide a 20 gallon tank that not might be a problem either.

rotary crazy

mazda said that they would not do this, that there where no benefict in the rotary, I dont know why but thats what they said

tmak26b

Mazda engineers already answered your question, go grab a Yamaguchi book. If it was that easy, they would just keep doing. Why do you think there are no 5 liter 4 bangers?

Icemark

No, that is wrong. The rotary engine was looked at in the 60's and early 70's as the only way many car manufactures were going to be able to sell a car in California due to its way lower emissions when comparied to piston engines of the time.

And in fact a the rotary powered cars never even had cat converters until the early 80's, while almost every piston engine had them back in 73.

If the cat converter was never developed... well all manufactures would be using a rotary engine in the majority of thier cars even this day.

And a 20B does not have any worse emissions than a badly tuned 13B.

Emissions is not a issue at all. Fuel consumption is the biggest issue followed by cooling.

swoope

iTrader: (5)

do you think a 13b could pass emissions now?

beers

tmak26b

Yes and no. Rotary engines don't put out much NO compare to a piston engine, but they put out much more in HC. Since the government decided HC is more important, therefore the tests we have today is somewhat bias against the RE. I was very surprised to see that the 8 isnt rated that high on the SMOG index. What is the # exactly on the earlier models? I believe they have changed over the years due to the different standards. I am curious tos ee where they are at. If I recall correctly, they were at 6.5?

rotary crazy

I really like to know why you say that cooling and fuel consumtion its the problem

I get 14 to 17 mpg in my 100% stock cosmo ( if I drive carefully) and this car weight 3300 lbs and have 19" wheels

it works much cooler than my fd!

RX8Maine

You are talking about multiple displacement systems, in which extra cylinders are along for the ride when cruising to allow for lower fuel consumption. When asking for full power, all cylinders are working, and they all have THE EXACT SAME FLOW characteristics.

I was pointing out that if all three rotors do not have the exact same flow characteristics, the system would be inefficient at best, and may very well produce enough internal stress on the Eshaft to be destructive under high loads. I don't think a system comparable to MDS would solve this, since it only addresses low-load/low-power situations and cuts fuel off completely to avoid detonation. That would not help under load with WOT.

Doesn't MDS also stop the valves from opening, thus eliminating air flow also?

jeffe19007

I would think that MDS would not close the valves.

For one the piston would be compressing or sucking on a sealed chamber both of which would consume power.

Icemark

Because that would tag the car into Gas Guzzler tax. And while many people would pay it, Mazda would never sell another Gas Guzzler vehicle in the states. That is what almost killed the company all together back in the mid 70's. They have said this over and over and over.

A 3000 lbs car must get better than 16 MPG to avoid gas guzzler tax.

And as far as cooling. That is one of the issues that prevented the FC from getting a 20B (there were running test bed FCs with 20B engines in them). The cooling system needs to be increased by 1/3rd over what a two rotor system would use. There are packaging issues already with the FE, what makes you think that you could cost effectivly increase the cooling capacity??

Then toss in the transmission issues- you'd be back to the R-type 5 speed tranny in order to handle the torque.

I have one that passes every two years just fine with only one monlithic Cat, so why wouldn't it??? It passes with less emissions than new and that it did stock when there was 3 cats.

And if you drive a RX-8 with a stock motor, then you drive a 13B. Go look at the castings on the housings. 13B right on the top... plain as day. Same as it has been since the 70's. Renisis is just the series name of the 13B used in the RX-8

Emissions is not some bug-a-boo science. If you could make a Ford 5.0 V8 motor pass modern emissions, you can get a cleaner burning fuel injected rotary to pass.

The problem with a MDS system on a rotary motor is that both oil and fuel act as lubricants to the rotors. So if you magically cut fuel on one rotor, you cut out half the lubricant to the apex seals leading to increased wear on the seals and housings. Even if you continue to inject (or really dribble) the oil in, then you have the issue of smoking when the oil gets dumped into the exhaust (which the cats hate).

Mazda has been playing with MDS on the rotary engine for the last 5 years with no cost effective solutions. Really the only solution is to kill only one rotor face at a time, but because of the side port design and mixture carry over, you end up with a very very lean rotor face. which must be burned before ejecting it from the motor (so not you have a valve in the intake and a valve on the exhaust that switches open and closed based on MDS and rotor face postion- leading to huge costs and control issues).

Just cutting out one rotor doesn't work, because then there is no lubrication for that rotor. That is different than on a piston engine where the lubricatant is still shot up from the crank to the piston rings even if that piston is "shut off".

rotary crazy

thats what most of the rx-8' are getting

the thing is in a lighter car with a better rear diff and todays technollogy, it can be made to 20mpg or maybe better

tmak26b

Your bi-annual emission testing is different than what NEW cars go through. They are more concern about what your car puts out during the first 10 min. than what you put out after.