Could somone tell me the bad things abour Rotarys? I really don't go into Rotarys much so if someone could name them, I'd appriciate it. ^_^

 

poor gas mileage

 

rebuilding requires pulling the engine out.

i thought our parts where expensive, but ive been talking to my nieghbor who has an '87 bmw e30 about costs of rebuilding... 100 bucks a piston!.

meh.... ill take rotary power. you can abuse rotarys longer than you can pistons.

 

Aren't Rotarys hard to work with? Not very reliable?

 

They are reliable, owners and some mechanics are not reliable.

If you do not take proper care of your car, who is to blame?

 

They seem to be reliable N/A or lightly boosted, but once you start getting power hungry (350 rwhp+ on a 13b)be prepared for an occasional rebuild imo. Tuning is key, but there are very few I would trust. When a seal does let loose it can damage the housings and turbo as well.

Gas mileage is poor when compared to piston engines with similiar output.

Rotaries are extremely loud with a free flowing exhaust, which can be good or bad depending on what you like.

Powerbands are peaky, low torque, like a honda or other small displacement 4 banger, again whatever floats your boat.

 

Besides what was already listed, they are loud, burn oil (about 1qt per 1,000 miles), not very emissions friendly, they run hot (especially the exhaust), they don't take over-heating or detonation as well as piston engines, it is difficult to find a good mechanic, higher-output rotary engines do not have as much low-rpm torque as their piston counterparts, and you can't dress them up with cool chrome valve covers.

On the good side, rotary engines have a small cross-section, low vibration, good hp-displacement ratio, light weight when compared to other iron block engines, are easily compatible with alternate fuels, have few moving parts, no valvetrain to deal with, lots of aftermarket parts available, are included in many race classes, and the power band makes them a lot of fun to drive.

As for the reliability issue, keep in mind that Mazda rotary engines dominated endurance racing until the rules were modified to lower the power levels of the rotary engines. Even so, you will still see rotary engines winning endurance races even today. An average street-legal rotary engine lasts about 100,000 to 150,000 miles before the seals (similar to piston rings) need to be replaced. While the seals are rather expensive, there are no camshafts, lifters, valves, or timing chains to replace... ever! The eccentric shaft (similar to a crankshaft) bearings rarely need replacing because there is so little lateral load on them, as opposed to the heavy lateral load of a piston engine.

 

The same would go for a comparable 4-cylinder piston engine producing 350+ rwhp.

Once again, the same applies to piston engines when a ring or valve lets loose, although the turbine wheel has a little better chance of survival. One advantage of a rotary engine in this case is that there is no worry about the timing chain failing.

 

So there are more goods than bads?

 

Definitely. Otherwise we wouldn't own them, and it wouldn't still be offered as a brand new engine. Take care of it and it will take care of you.

 

It all depends on how you personally weigh the differences.

If there were one "best" engine, everybody would use it.

 

hmm, sounds good. On another forums, they had a 3rd Gen Rx-7 VS a MKIV Supra. How would you compare them?

 

what you like to compare. Yes supra engine can build more HP ? However MK IV supra engine is much heaver compare to 3 gen RX-7(700 LB heaver, this is a lot of weight). so even with less HP RX-7 can still beat supra on straight line performance. and if you are talking about cornering. Not a single japanese FR car(Z CAR. 240SX. Supra. etc) can beat 3 GEN RX-7.

 

Apples to apples. Each car was made with similar power, handling, and marketing goals in mind. They were and still are direct competitors.

 

 

 

Easy to mod, easy to mod wrong. Very addictive when working properly.

 

what i thought the rx-7 got 4.9 sec oh wait thats the r2 or r1 models

 

That yellow thing on the previous page is an R-1.

 

Probably the lack of tuning knowledge is the worst thing about it.. Once the tuning starts to come together, all the other "bad" things start to disappear... On my own car , it averages 30 mpg highway..I have been boosting 18-20 psi on pump gas till my boost controller bit the big one last week. I have been driving it on average about 2000 km's a month or so, since early spring, with no problems except for breaking my hks transmission, replaced with the stocker for the short term..Rotary is a long term commitment, its hard to just jump into it and expect roses..
But really most of the problems are due to the supporting cast, not the engine itself..
And I saw Evil aviators disclaimer of lighter than cast iron piston engines, the rotary itself is still lighter than some aluminum blocked motors as well...A 3 rotor p-port is less than 400 lbs..Official weight of the 13brew in running form is 360 lbs.. There isnt much lighter than that among common engines..Max

 

An rx7 is like a pitbull. There are no bad pitbulls only bad owners. Tuning is key you take care of it and it will take care of you. And just like a pitbull it is not for everybody but to those who love and appreciate them, they will never trade them in for anything else.

 

Thats a funny analogy...I have both an RX-7 and a pitbull. I agree, both of them aren't for everyone, but I love 'em!

 

My carbureted RX-7 gets better fuel economy than my (lighter) EFI 1600cc Nissan.


I'd say the only downsides are intense noise, poor power/size due to thermal efficiency woes, and poor emissions.

For ease/cost of modification, and reliability, rotaries simply cannot be beat.

 

One thing that nobody has mentioned is the fact that a Wankel engine can never be as efficient as a piston engine.

Why?

The combustion chamber is square.

This is definately not ideal because as fuel/air enters the combustion chamber it cannot naturally fill an a natural (circular) motion.

Also to seal a right angle is a very difficult task... piston ring hold a nice equal seal around the cylinder wall but a ratary must seal 3 sides (4 technically).

We have discovered these issues when developing a methanol 13BPP running Gen 2 6 port rotars with added meat on the face to bump the comp. upto 10.1

We were pulling aroud 358bhp BUT it just did not have enuff pull to blow away the pushrod engines.

On paper it worked... had more power than the quickest Esslinger of the time that constanly ran top 5... but it never delivered an it was WAAAAAAAAAAY too loud. Also the weight disadvantage by carrying a bit more fuel hurt us early in the race.

Engine foumd it way into a street RX-3 and was detuned to run pump 96 octane.

I own 3 cars an 2 are powered by 13B's but I do believe that they are gas guzzlers and too loud.

But thats the appeal and thats why I adore them... fumes noise flames. Nothing matchs the experience.

 

What does a 400hp FD have in common with a 800hp MKIV?
Same quarter mile time.

Also you can snap up a good FD for 10-13K while the going rates for Turbo MKIV's have peaked at about 30K. When it comes to FD's its a buyers market right now, ill be getting one shortly.