sen2two

so i know its been done. but i cant find info about it. it seems to be a secret.



ok, if someone was to take a stock mazda rotor. fill it combustion divits with either devcon, some other metal epoxy, or even weld/braze in some metal. this would raise the compression and change the complete combustion cycle dynamics.



but, what to use??? what shape would you form the combustion chamber?



what about the longevity of the rotors? 2,3,4 runs down the track? (quartermile) or maybe same life it done right.



would the extra weight on the rotors break the e-shaft, gears, bearings? (obviuosly they would be balanced.





im no scientist. but i read something a while back about a scientist who made a scale rotory motor and had an X in the cumbustion divits and it created much more power (in scale) and burned cleaner emissions. i relate this to the "swirl" in the combustion chamber of the piston engine. changing the swirl changes everything.



discuss...

Lynn E. Hanover

The several problems built into the rotary Are: Combustion chamber too long. Combustion chamber too cold. Combustion chamber has no squish areas. Combustion chamber has close head space areas that quench the flame out. There are other problems but all else is the outcome of those mentioned.



So, where to start? Felix collected thousands of engine and compressor patent drawings and cataloged them by the types of motion used to create the max and min volumes of each chamber. All was lost in WWII and he started over again after the war. He was an engineer who was good with sliding seals. (like a side seal) . He had a helper who’s name I have forgotten who made carboard models of the most interesting of those drawings.

He was interested in an engine with pure rotary motion. He came up with the shape you would recognize but not the engine you know. He sold interests in this proposed engine in blocks that amounted to over 100% to a number of companies. NSU the Moped people, were the one company you would know about. The company engineers struggled with Wankle’s design but made only three examples (Moped sized) engines. The best was a 13CC screamer with 26 HP at 25,000 RPM. The design had the outside of the engine spinning at 2/3 rotor speed, and there was great concern about how to make this practical. The short story is that they could not. NSU engineers drew up the engine you know today and went with that. Wankle was pissed and wouldn’t help NSU with anything. NSU tried to patent the shapes involved and found that a patent had been granted to a compressor engineer who worked for a truck manufacturer. The man who had the patent gifted NSU with the patent. No charge.



So the rotary is the wrong engine, selected for the wrong reasons, clearly stolen from somebody else who should have had a lawyer. NSU made two cars with the (nonWankle) rotary engine and both had dreadfull problems. NSU no longer exists. Mazda had a license to build the engine, and eventually got them to last long enough to use in a car.



Compared to a piston engine, the rotary has a huge piston and a tiny short stroke. In piston terminology it is way over square. Square is the piston diameter (use area instead) and the stroke is the same. So in its best form it has **** poor torque. The whole rotor face is the combustion chamber and it is moving the mixture passed the plugs at a high rate of speed. The other side of the chamber is fixed and cold compared to a piston engine. So the mixture that should be getting additional energy packed into it from being compressed, is giving up energy to the housing and coolant. So each combustion event is less energetic than it should be. The mixture also, (for lack of energy) condenses out as droplets of fuel, and is difficult to light. So the addition of a very high energy ignition is a must for racing. The flame front is slow, and has a long way to travel. The flame goes out near each apex seal where too much heat is removed to support it and the head space is too close and kills the flame. More advance helps this out up to a point. The shape of the combustion chamber in the rotor face is there to provide a deep enough groove to connect the two flames from the two plugs. Filling in the groove to aid compression ratio reduces flame travel and power.



But I run on as usual….Now you discuss….



Lynn E. Hanover,

BLUE TII

You can look at what Mazda has done with the rotor recess throughout its range of compression ratios (7.5:1 in in 13G turbo to 10:1 in the Renisis.)



Basically, I believe they very similar shape on all but one motor.



The 78-80 12A had a LDR (leading deep recess) instead of usual MDR rotor. LDR rotor for faster flame propagation from increased squish effect while using just leading spark plug for part throttle. This was done for better fuel economy and higher exhaust heat for thermal reactor emissions system.



I believe the Renisis has tried to get a similar effect with the MDR rotor (that is better all around compromise shape) by firing the trailing plugs first under part throttle to increase the squish effect for the leading plugs (negative split).



Mazda will hopefully release the 16x which has more stroke than the current 13B for ~20% more torque.



I wish they would look into Felix Wankel's DKM rotary again as the main problem was it had to be disassembled to change the spark plugs, but with current spark plug technology (and life) this would be much more acceptable and there is probably an even better spark plug alternative.

j9fd3s

just to clarify its the 76-85 12a rotors that are LDR, they come in 2 flavors the 83-85 ones are slightly lighter. i'm getting old i had to look that up

Lynn E. Hanover

I think the whole engine spinning would be the big problem in a engine big enough for a car. If you can overcome that I will fix the "spark plugs inside the rotor problem".



Lynn E. Hanover

j9fd3s

that would be a nice gyro....



actually had a customer who had all kinda of stories, one of em was how overhead cam engines weren't as good for road racing, as in say a dohc v-8 theres about 100lbs of mass spinning away up high, compared to say a small block chivvy, which has the cam down low.



the other neat example was about the JGTC skylines, the straight 6 RB engine that nissan makes, is so heavy, they machined 66kg off the block, and it was STILL a porker. 66kg is enough iron to cast said small block chevy. thats a LOT of extra material.

heretic

Actually 66kg is a small block Ford. Small block Chevys are made with very low nickel content iron and they use a lot of material to compensate, so they're quite heavy. Thanks to effective marketing, though, the bowtie motor is the one that people liked to modify until the 5.0 Mustang revolution.



NSU does still exist. They're one of Audi's rings. One of the last engine designs they did was what was turned into the Volkswagen watercooled four, the basic architecture of which has been folded spindled and mutilated into fives, V6s, and V8s, as well as several different flavors of fours. They're still in production today...

sen2two

i have done more searching. and what i found corresponds to what has been said. anything over 10 compression seems to lose power.



so instead of filling to raise compression, do it to change the swirl. i know theres no real way to detect the swirl. since every way of sencing/viewing it effects it. so test and tune is the way to go.



what would be used to do this if i were to try it???

mazdaspeed7

Porting. Its common practice in honda engines(and im sure other makes as well) to have slightly different cam lobes for the 2 intake valves on each cylinder. It biases flow to one of the valves, which introduces a swirl in the chamber. Some of the honda motorcycles had a version of vtec that only used one intake valve at low rpm, and then the other one opened at higher rpm.

Lynn E. Hanover

In the 12A engines the primary and secondary ports were the same size. In later engines the primaries are much smaller than the secondaries. Why? To maintain high energy flow at lower speeds, to improve milage and response.



Lynn E. Hanover