For inspiration:
Curtis73 (Forum Supporter) said:psteav (Forum Supporter) said:IIRC, the snowmobile miata still makes around the same 92-94 whp as the 1.6 lump did...but the car is like 1700 lbs.
The outboard idea is intriguing. Non-running outboards are stupid cheap.
I have wanted this for years, but I can't figure out a decent way to get them to run horizontally. I suppose you could lay them on their side and build a thing to rotate the carbs 90 degrees but I would think you might get abnormal cylinder wear.
You also have to do some internal mods (depending on the power head) to prevent the cooling water from joining with the exhaust
Abnormal wear from what? There's no oiling system with a two stroke (VRO be damned) and they already sit so that the cylinders are laying on their side. Fit one up with a sidedraft carb system and let them remain on their side. Done.
Since power is just torque and rpm, it comes down to choosing how you want to make your power. Torque is primarily what breaks things, requiring the rest of the drivetrain to be heavier. RPM is the key to light total weight for the same power.
Even at the same torque rating, twice the cylinders hits the crank half as hard because it's hitting twice as often. So while a 7k rpm LS3 based V-twin should be capable of similar power to a 16k rpm 600cc sportbike I4, and still be a substantially light engine, it would also still be punching the drivetrain with widely spaced LS3 level torque spikes... Between the cylinder count and rpm, on the order of 5x those of the sportbike. Which is why I'm doubtful that the same bike clutch/gearbox or snowmobile CVT would survive for very long behind it. Meaning it would probably still need a heavier automotive type drivetrain behind it... I suppose some of the big-cube aftermarket 45* v-twin stuff ($$$$) might hold though? Regardless, powersports engines are pretty much as good as it gets for powertrain power-to-weight in the mortal realm of mass-produced (available and affordable) options.
Running just a torque converter on a torque biased engine is an interesting prospect too though. Perhaps design the chassis for 'easy' diff swapping between events for top speed adjustments, although seems it would probably need some secondary reduction or non-standard (crazy) diff ratio for autox. Maybe turn it transverse and run a chain with sprocket swapping... Alternatively, some type of DIY planetary or 'chain-gang' based 2-speed might help alleviate that without too much weight or cost gain. Then again, the transmission weight is low and centralized, so still maybe not the biggest concern either.
Can you keep a jet ski engine cool off the water? Watercraft make crazy power relative to their size because they're always connected to a giant heat-sink.
In reply to A 401 CJ :
Been a while since thermo, but isn't that why they are efficient at power production, and not necessarily why they make power?
In reply to A 401 CJ :
Keep in mind the duty cycle and duration. Even compared to a racecar, PWC's run at a MUCH higher duty cycle too. Meanwhile drag racers can eliminate their water jackets entirely and still make crazy power for a short duration.
For $2,500 you could live out your V8 300 HP 2 stroke dreams..
Driven5 said:
Running just a torque converter on a torque biased engine is an interesting prospect too though, even more so if it could be locked up. Perhaps design the chassis for 'easy' diff swapping between events for top speed adjustments. Maybe turn it transverse and run a chain with sprocket swapping... Alternatively, some type of DIY planetary or 'chain-gang' based 2-speed might help aleviate that without too much weight or cost gain. Then again, weight low and central in the car might not be too big of a deal to just use a powerglide.
A quickchange rear end is the beast you are looking for.
Tom1200 said:Apexcarver said:In reply to Mr_Asa :
And, for a given power and weight, what's more efficient? Working the fluid through a converter or the belt and moving sheaves? I'm pretty sure the sheaves waste a lot less power than what goes into frothing and heating the trans fluid. Also, the weight part of the equation...
If you go over to my F500 thread, I have a link that puts in car footage side by side of my F500 vs Gimpy's CP car. That comparison will show why I giggle every time I run my f500... IT SCOOTS. I also have footage side by side with a shifter kart and I can hang until the braking zone for the first real turn, but with a whole lot less work from the driver.
Link please.............I really want to see that video.
The big note on the shifter kart video is, yes, I massively gave it up on the first big right hander as I was scared of a bump that if I was off line might have torn my floor up.
Just as a data point and something to think about. High peak horsepower from tiny motors isn't what I've found to be the best setup for autocross. Torque is king.
The Zoomboni uses a totally boring 5.0 Ford mill that doesn't even make much horsepower, but the torque is all you need for autocross. A 5.0 isn't actually all that heavy (I loaded one in the back of my Suburban with one other dude helping me) and the T-5 is lighter than a Miata gearbox. So it could get lighter but the whole package is right at 1850 lbs and seems to work well enough.
In reply to KyAllroad :
Provided it makes adequate torque thats more a gearing concern though?
In reply to nocones :
This is basically what the Chaparral 2 Can-Am cars did. They only had a Powerglide, so 2 speeds, but 1st was seldom used. Big block torque and very low mass.
Apexcarver said:A quickchange rear end is the beast you are looking for.
Generally speaking, absolutely. I was thinking more along the lines of Challenge-budget friendly ideas though.
In reply to KyAllroad :
More specifically, torque to the wheels per pound of car is king. Half the car weight requires half the torque to the wheels. Half the torque to the wheels can be provided by 1/4 the torque at the crank turning twice the rpm. When geared down to equivalency, high rpm engines can be capable of similarly broad torque curves to the tires. And while broad torque curves are important for geared transmissions, they are not so much for CVT's.
Halving the weight also provides additional gains in turning and stopping, not to mention consumables, which reduces the tq/lb demands to achieve the same total performance.
nocones said:For $2,500 you could live out your V8 300 HP 2 stroke dreams..
These can be found much cheaper than that...I sold one a few years back.
Mercury 2.5 weighs under 200lb dressed power head, made up to 300hp from the factory. A couple have been used in sprint cars and dune buggies. The exhausts are meant to be wet so that would need to be resolved.
codrus (Forum Supporter) said:Pete. (l33t FS) said:Light, however, they are not.
I think rotaries got their reputation for being lightweight in the 1970s, when most piston engines were iron block, iron head, etc. Lots of development work on making piston engines lighter, not so much on rotaries.
Now you can get billet end and center plates, saving a huge amount of weight, about 1/2 the weight of the stock parts. Complete with coolant channels and everything needed to run normally on the street. Housings are already alloy. 1000hp no problem.. but definitely not a budget option
In reply to MattGent :
That's the only one I found easily. What kind of price do you think you can get one for?
Mr_Asa said:Curtis73 (Forum Supporter) said:psteav (Forum Supporter) said:IIRC, the snowmobile miata still makes around the same 92-94 whp as the 1.6 lump did...but the car is like 1700 lbs.
The outboard idea is intriguing. Non-running outboards are stupid cheap.
I have wanted this for years, but I can't figure out a decent way to get them to run horizontally. I suppose you could lay them on their side and build a thing to rotate the carbs 90 degrees but I would think you might get abnormal cylinder wear.
You also have to do some internal mods (depending on the power head) to prevent the cooling water from joining with the exhaust
Abnormal wear from what? There's no oiling system with a two stroke (VRO be damned) and they already sit so that the cylinders are laying on their side. Fit one up with a sidedraft carb system and let them remain on their side. Done.
They sit with their cylinders laying on the side with the thrust angle of the rod pushing left and right. When you lay them on their side, they have the additional gravity adding to the side thrust. Given the fact that their lube is from a tiny bit of oil mixed with the gasoline, you get far less lube. Most H- or flat/boxer engines counteract this with an offset pin in the piston which you wouldn't have in a 2-stroke.
It may not be an issue, but I know from all the Subys (which is two) I've torn apart, there is almost always more wear on the bottom of the cylinder than the top.
But you are correct that without the crankcase full of oil they will run just fine in nearly any orientation. Hence why 2-stroke is more popular in things like chainsaws that have to operate in multiple vectors.
mr2peak said:codrus (Forum Supporter) said:Pete. (l33t FS) said:Light, however, they are not.
I think rotaries got their reputation for being lightweight in the 1970s, when most piston engines were iron block, iron head, etc. Lots of development work on making piston engines lighter, not so much on rotaries.
Now you can get billet end and center plates, saving a huge amount of weight, about 1/2 the weight of the stock parts. Complete with coolant channels and everything needed to run normally on the street. Housings are already alloy. 1000hp no problem.. but definitely not a budget option
I'll want to see the power duty cycles capable before I trust those billet housings.
Racing Beat cast some a long ways back, and they were not cheap (roughly $1500-1800 each, and you needed twelve-bolt stationary gears), but they were also marketed not to drag racers like the billet housings, but to aircraft engine types. A drag motor doesn't even need a cooling system once it makes enough power (perversely enough) but aircraft are very much a bolt the throttle open for minutes at a time application.
Pete. (l33t FS) said:mr2peak said:codrus (Forum Supporter) said:Pete. (l33t FS) said:Light, however, they are not.
I think rotaries got their reputation for being lightweight in the 1970s, when most piston engines were iron block, iron head, etc. Lots of development work on making piston engines lighter, not so much on rotaries.
Now you can get billet end and center plates, saving a huge amount of weight, about 1/2 the weight of the stock parts. Complete with coolant channels and everything needed to run normally on the street. Housings are already alloy. 1000hp no problem.. but definitely not a budget option
I'll want to see the power duty cycles capable before I trust those billet housings.
Racing Beat cast some a long ways back, and they were not cheap (roughly $1500-1800 each, and you needed twelve-bolt stationary gears), but they were also marketed not to drag racers like the billet housings, but to aircraft engine types. A drag motor doesn't even need a cooling system once it makes enough power (perversely enough) but aircraft are very much a bolt the throttle open for minutes at a time application.
Check out PAC Performance in Australia, they are pretty much the leaders with this stuff at the moment. I wouldn't have any reservations about running their setup, street strip or circuit
Here's Hoonigans visit to PAC Performance
https://www.youtube.com/watch?v=UYK2yqRjkPc
https://rotronpower.com/rt690xe-rotary-engine/
220HP, 95lbs complete. That's current rotary technology. Looks like it will be used in the Crighton CR700W Motorcycle https://www.autoblog.com/amp/2021/11/02/crighton-cr700w-rotary-motorcycle/
Dreams are nice aren't they?
In reply to mr2peak :
It annoys me slightly that a company making Wankels, that is not Mazda, is calling them "rotaries". 
Mazda was the second to market by a handful of months, and the last production automobile by 33 years, so they kind of have a right to their preferred name.
(Speaking of members of the Wankel Consortium, anyway. I hear scuttlebutt about Chinese truck engines and AvtoVAZ engines)
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