4 rotor vs dual engine
 

Hypothetical/fanatasy question. I have no idea where to put this....

All the talk of 3 and 4 rotor sounds like a heck of a lot of development is required. Especially 4 rotor.

What would be the pros and cons of sitting two Renesis motors side by side or front to back and hooking them both up to a gearing system linking the shafts? Would the mechanical linkage be enough? Or would you need an uber ECU to control both motors as one?

The cons I can think of are (1) weight (2) Space and (3) tuning.

The biggest pros I can think of are reduced development time & cost.

Nothing comes to mind, but I'm pretty sure I've read about dual engine sports cars. Generally curiosities or someone's incarnation of a Hot Wheels toy. But I've never read or heard that there are significant problems that have to be overcome.

I suspect you wouldn't want to put the two engines on opposite ends of the chassis like the Jeep show car. Even with a beefed up CF drive shaft, the torsional spring rate would make joining the two engines at hi revs a vibration nightmare. Need to be more rigid, and therefore close proximity.

Heh I don't think they would fit side-by-side :p

Although I have seen the concept on a 80,000 hp warship. You wouldn't happen to be in the Navy would you? ;)

there was a guy that installed 2 engines in a tiburon...but they weren't linked together. front engine drove the front wheels, rear engine drove the rear wheels. two independant trannies too.

^ the same thing was done in an audi TT, it had a single turbo V5 at each end, making 400hp each. They wanted to hit 400KPH with it, but they counldnt get both engines to work together enough to go over about 200KPH

2 400hp engines couldn't get the car over 125mph?

i think it ran 11's in the 1/4 mile and could do a badass burnout. Both engines were turbocharged

That tiburon was sick


The two engines were turbo but no intercooler and no BOV if i recall correctly. He also had the hatch painted solid. His idea was for it to be a sleeper. It had some cheap ass Nitto 450s or something. I also think the engines were cooled by methanol.

I recall Car and Driver putting two engines in some car and getting minimal performance gains because of the increased weight.

Somewhat related, I just got a tandem bike this last weekend. I expected to hall a$$ with two somewhat experienced bikers on it. Not the case. On the flats, we were as fast as I am alone on my road bike, but slower on the hills. Very fun, but not the additive perfomance gains that I was hoping. Kind of like when I installed my intake and exhaust :)

there was a 2 engien 2 rotor per engine car at last years 7stock so it has been done already

how did the 7 go though? i have never heard of it.
anyone here knows about that car?

yeah, they couldnt get the engines to work together in the car....each engine had its own trany, so it was 4wd, 2wd front and 2wd rear....

they had some big expensive ECU in the car to control the throtle on the motors and stuff.....each engine was hand built to match the power output and rpm and everything....

in the end it came down to the fact that they engines were not working together well enough that the driver felt safe taking it any faster than about 130mph...IIRC.

I know they were far short of their 250mph goal.

That's why they have to be linked. Even slight differences in HP and the different transmissions will be fighting each other.

Neat. I actually wasn't even thinking it has to be a 7 or an 8, just thinking in general that the physical size of the Renesis might make the project a lot more feasible than some of the old V-16 dragsters that were rally two V-8s front to back.

I'm not sure how the dragsters' drive shafts were linked, but they must have been. Must have been a B*tch trying to tune all those carbs though.

I remember a few years ago seeing an article on one of those county fair type tractor pulls. You know the ones with multiple chevy 454 v8 and roots type superchargers

Well this guy had had 2 bridge ported 13b's and was very competitive :eek:

How do they link those engines together?

http://cp_www.tripod.com/rotary/images/pg27_04b.jpg

He has got some other interesting rotary concepts on his website

http://cp_www.tripod.com/rotary/pg27.htm

haha!, dude that tiburon was insannneee!, that burnout as just hilariouss.

hehe

rotary power for a tractor pull...interesting.

Ford GT 90 has 2 v8's

Think about how loud 2 uncorked, wide open rotaries would sound.

I'm going deaf, just thinking about it.

Its actually done very simply... the end of the crank shaft of the front engine gets half of a coupling mounted to it and the rear engine is modified to mount the other half of a coupling to the front of the crank shaft. The coupling is held together with sturdy chain which will break loose if something drastically goes wrong thus uncoupling the engines. Each engine then receives the same throttle input.

That's really interesting. I figured it would be a whole lot more complex. How much room does that coupling take up? Would this kind of setup be possible in a street car? :D

The coupling doesn't look like it takes up too much room. Could use a universal joint, which would take up more room, but has the added advantage that both engines don't have to line up perfectly or be rigidly mounted to a sub frame. Then both could just be on their own motor mounts.

I know I saw some application where there were two motors side by side, they would have to both feed into a gear box or something. I haven't been able to find any stuff online though.

Side by side would allow for a shorter/wider car than front/back configuration. And if you're really after handling, easier to package the driver and mass closer to center of rotation than the dragster config.

It would take up even more space, but...

What about some kind of fluid torque converter, between the engines?

Then you could have a little buffer for rpm and vibration differences.

the way to more than add the HP of each engine, ie 238+238=476, would be to hard link them together where one rotor is going through TDC 90 degrees apart as opposed to a two rotor going through TDC 180 degrees apart.

John

I'm not even sure what you're trying to say. But you think phasing the rotors would be a problem?

Remember that if the Rotors are 180 degrees apart, they're also 60, 120, 240 and 300 degrees apart. With apexes 120 degrees apart on a rotor, you could phase 4 rotors at R1:0, R2:30, R3:60, R4:90, then at 120 you have the apex for the first rotor again. Should be able to make this very smooth.

That's assuming a geared or chained linkage. A fluid torque converter would probably allow the motors to get in and out of synch. The concern here might be harmonic vibrations. Dunno.