spacecadet said:I just came in to say, go spend time near an F mod in grid at an SCCA event.
Loud, like in numbers dear god it gets old FAST.
I was at an autocross this fall where I encountered an F/Mod for the first time ever. On it's first run, it launched and then immediately broke something and had to be pushed off course and never ran again all weekend. I had to resist the urge to cheer.
In reply to No Time :
You beat me to it.
Also a 2 stroke doesn't need to be peaky with a narrow power band. it's easy to alter the power band of a high performance 2 stroke engine
The amount of criticism here leads me to believe that many of you have never riden a snowmobile, much less one with a couple hundred hp.
Yes they are light which makes their performance staggering when traction is available. I'm talking 0-60 times that put modern liter bikes to shame.
I'm sure the right set up in a car could be lots of fun. Some Yamaha sleds essentially use sport bike motors with a cvt that looks to be what there guys have done. But if your going to go big I'd go right to a handful of monstrously powerful 2 stroke motors. 1000cc brp twin maybe, arctic cats 900 twins made somewhere close to 150hp stock and 100hp from pretty low rpm. Of course I would go with an xcr 800 Polaris triple because of the noise!
aircooled said:Knurled. said:In reply to aircooled :
CVT.
Tuned right, they are way better than a manual trans, which generally is always in the wrong gear.
Sounds reasonable, but also seems to indicate they are using a transmission designed for a vehicle a quarter the weight of the Triumph.
On the other hand, it takes a lot of power to shove a 600lb sled over snow, so the transmission should be able to handle a relatively high duty cycle.
Hey, it's a fun engineering exercise, but I am not sure it's a good bang for the buck (to answer the OP question). I suspect you could swap a Miata drivetrain in for similar effort / money (both will need extensive mods) and end up with a far more practical (and not much slower) vehicle, that you could actually drive around town or to work. The CVT is certainly a great way to maximize power, but would be an absolute obnoxious nightmare in anything but all out performance driving. I personally would not be a fan even at an AutoX. A run would be go pretty much like this:
WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!!!!!!!!!!!!!!!!!!!!, rup, rup, rup, rup..... seems like that would get old pretty quick.
If you are into it, go for it. Not for me.
I investigated a bunch of different ideas to power my awd subaru Justy ice racer.
Needed to transfer power into the stock justy 5 speed,could use the justy gears or just run it in "a" gear and use the gearing from a bike or cvt sled engine.
Very narrow space left by the 3 cyl justy engine,I wanted to use a twin sled engine but couldn't find space for thr primary/secondary clutches and jackshaft and chain to power the input shaft of the justy trans.
A sled head buddy asked his clutch guy about setup and he said good luck trying to make it work well with the weight of a car.
So its Vtwin sport bike power.
Btw I also had an F500,those knocking the noise etc etc never tried one.....very different and challenging to drive one properly but pretty magical if the surface is flat as glass.
@NickD I've owned my car for nearly 5 years and the only mechanical I've had is the chain coming undone because the mechanic (me) forgot to safety wire the master link. It went 6 events before it came undone.
@aircooled the engine noise is not nearly as bad has that; it picks up revs very quickly so it's more of a Waaaaaa, mmmmm, Waaaaaa,mmm. As for autocross the CVT is a huge plus as your never caught between gears. If you ever get a chance to drive an F-mod jump on it.
As for th performance of sleds; I watched a stock sled run an 8 second (might even been in the 7s) and the only mod was a drag belt and wheels on the skis.
Knurled. said:aircooled said:Knurled. said:In reply to aircooled :
CVT.
Tuned right, they are way better than a manual trans, which generally is always in the wrong gear.
Sounds reasonable, but also seems to indicate they are using a transmission designed for a vehicle a quarter the weight of the Triumph.
On the other hand, it takes a lot of power to shove a 600lb sled over snow, so the transmission should be able to handle a relatively high duty cycle.
Exactly. That track has a ton of drag. It's harder to push or pull a sled by hand than it is to push a 3000 lb car.
Man I miss my piped Polaris XLT580, gutless below 5500 rpms but when it got into the powerband you better hang on tight or you'll be flapping from the handlebars like a flag in Wyoming. The engine will rev to 8 or 9k and hold there while you just keep going faster. What a rush!
I always dreamed of putting a sled engine in a light kit car like a Bradley GT.
I don't understand what's with people on here... snowmobile engine with a CVT in a light car is a side by side like a razor turbo, right or wrong?
Same kind of weight so why would everyone say they wouldn't be good to drive? If that was so, no one would be running around on them and having a blast racing them on roads or off road. They are even street legal now.
Are you really saying a r1 motor doesn't have the right powerband or a RAZR turbo with way more power doesn't either?
I suggest trying one before giving their opinion so they can base it off of real experience instead of imagination.
The fragility of a snowmobile CVT is the reason those powertrains aren't a popular swap, they don't handle the weight of anything in the production car ballpark well.
In reply to GameboyRMH :
Are the razor type side by side cvt's as well? Or how do they work?
if the snowmobile cvt wouldn't hold up could you swap a different cvt on?
In reply to GameboyRMH :
Are the razor type side by side cvt's as well? Or how do they work?
if the snowmobile cvt wouldn't hold up could you swap a different cvt on?
In reply to Somebeach (Forum Supporter) :
It comes down to if you put a drive train from a 1400lb vehicle in a 2500lb vehicle.........go figure it may fail.
The issue is most snowmobile or SxS only weigh 1600lbs or less so finding an off the shelf solution may not be an issue.
Scalability of a CVT is challenging due to thermal challenges. The rubber belt setup from a snowmobile can likely be good to about 12-1400lbs with <300hp I would think. You might try talking to some of the guy running bigger triples in Amod. They make 300ish HP work in those.
As far as oil cooled automotive derived, well nobody has really done a performance one as of yet. I'm not sure how many of them would hold up to prolonged performance use.
I'm biased, I'm a F500 owner/driver. It's amazing that people will say things about Fmod, but not about Amod running 2stroke/cvts...
Whatever you want to say, it's one of the most fun things I've ever driven in 20 years of autocrossing and it's not that expensive. The only breakages I've had were related to the chain drive, and only twice in different places. Both breaks were fixed with stronger parts. I broke a $20 part, and a $6 part... And replaced a $65 chain as preventative maintenance.
Is it that we are faster while spending less?
Try driving one. Not having to care about shifting and never being caught off powerband at low RPM makes for a ton of fun.
In reply to Apexcarver :
I'm impressed that you have gauges. That implies that you have time to look at them!
I can't imagine looking anywhere but far, far ahead.
Why can't an adapter plate be made and run a manual trans behind a snowmobile engine?
In reply to Noddaz :
Aside from the potentially narrow powerband, if it's a 2 stroke then they really, really don't like it when you close the throttle at higher RPM. SAAB 2 stroke cars had a one way clutch on the transmission to prevent engine braking in order to save the engine.
This dashed all of the cool thoughts I had the first time I handled a Mercury Marine V6 engine. Those things are TINY and weigh nothing.
Pete. (l33t FS) said:In reply to Apexcarver :
I'm impressed that you have gauges. That implies that you have time to look at them!
I can't imagine looking anywhere but far, far ahead.
As an F-mod competitor for 10 years there is actually more time then you think.........but yes things happen fast.
Somebeach (Forum Supporter) said:In reply to GameboyRMH :
Are the razor type side by side cvt's as well? Or how do they work?
if the snowmobile cvt wouldn't hold up could you swap a different cvt on?
The SxS CVTs barely hold up to use in the SxS they were designed for, so I don't think they'd work well in something even heavier.
Noddaz said:Why can't an adapter plate be made and run a manual trans behind a snowmobile engine?
You would need to find a way to isolate the engine from axial loads put on the crank when disengaging the clutch. They run ball bearings for the crank in the 2 stroke engines which are great for radial loads applied by the CVT, but no thrust bearings to handle loads from an automotive style clutch.
Watching mountain riders on their turbo sleds the belts don't last very long on those, and are not cheap.
In reply to adam525i :
I think that's the weak point for a CVT once you get to the weight of SxS and created the biggest challenges for a snowmobile powered car. Add in the traction you could get with good tires and the belt has to absorb all the shock and provide slip during launch.
I wonder if it's possible to run multiple snowmobile CVTs in parallel to increase load capacity?
In reply to No Time :
So, my 800lb 105hp car has been through 5 years, many autocross weekends, and a track day on the same belt that was on it when I got it (no idea how old it was then). I am getting ready to replace it out of guilt rather than need.
In reply to Apexcarver :
That's similar to my snowmobile experience, but in the 400-500lb and 70-80hp range.
On snowmobiles, modern belts hold up well and catastrophic failures tend to be rare. The biggest killer is heat and slippage. Breaking trails in deep, heavy, wet snow can kill a belt in short order if the rider abuses it with lots of start/stop and slipping of the belt.
Those mountain sleds are up over 200 hp, 450 lbs dry without rider and can be a 165" long, 3"+ paddle track in deep snow. Lots of track weight to get spinning in deep snow and No Time is right, the heat seems to be the issue.
The CVT systems also tend to be the same across the range so the same clutches came on a fan cooled twin pushing 50-60 hp or a liquid cooled triple up over 160 Hp with just different weights and springs to tune it to the engine.
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