Theres a halfway decent book to get launched on ideas https://www.amazon.com/Build-Motorcycle-engined-Racing-Cars-SpeedPro/dp/1787111695/ref=asc_df_1787111695/?tag=hyprod-20&linkCode=df0&hvadid=266004384678&hvpos=&hvnetw=g&hvrand=785898081214410495&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9007653&hvtargid=pla-606477698629&psc=1
(You can find it much cheaper than amazon, just the easy place to review it)
As far as competitive outlets, you kind of have a few choices. (SCCA classing)
Road Race
Autocross
Formula S gives you the bigger bike engine as well as aero. I dont know the most about the class, but I know that there are several homebrew conversions running there. It's a regional only run what you brung class with reasonable safety limits. You could in theory run in either AM or BM autocross class with one, depending.
F500, More limited class, but much cheaper and much more reasonable to build a somewhat competitive car. 600cc bike engine with restrictors. 900lbs with driver. No aero. Solid beam rear axle with no differential. Canisters with rubber pucks instead of coilovers (a big cost equalizer when you think about it). You would autocross in Fmod. The class also allows snowmobile/CVT drivetrains that are believed to be much better for auto-x, but I havent seen a real effort to autocross a bike engine F500 no a national basis so while it may be disadvantaged, I dont think massively so. I have a snowmobile powered F500 that is still roadrace legal that I autocross.
Its really worth looking at the SCCA roadrace GCR (Here) and building to a class to have outlets for the car, it helps you to enjoy the car and it helps if you decide to sell it later on. It also helps you not build a death trap inadvertantly to build to the safety standard.
The rub with formula cars is that they are more limited in use than modified production cars or cars close to street legal in size/dimension. I havent seen an outlet for HPDE anywhere near me that would let me run and even if there was, I dont want to be mixing up with corvettes and mustangs in a 800lb with me in it car. (older snowmobile engine gives me a weight break, see GCR) that only comes up to my thigh. I dont even know if a new mustang would feel me as they ran me over... That said. Roadrace is rather fun looking, in the northeast Pennsylvania Hillclimb Association has some rules that are well worth looking into. And autocross FTDs are always fun to shoot for and fairly easy in something like this. Point is, look around for places to run a car before you start in on building or buying. I understood the limitations before I bought.
Another consideration, its worth looking at the sports racing catagory as well in the GCR if thinking about a bike engine purpose built racecar. Again, straight to BM or AM for autocross, but a little more leeway with HPDE possibilities that would need to be researched.
Heres a photo of my naked F500 for inspiration. Building a 600cc bike powered F500 (F600) car that could be reasonably competitive is very grassroots doable. The facebook F500/FM group had someone working on an open-source design for a chassis with all the places to get parts. (a lot of micro sprint roundy round dirt track parts are useful, especially for the rear axle)
If you want to try to build one, I would be happy to do a video walk-through of my car to help you on your way.
In reply to Apexcarver :
Is there a formula car class that isn't F500 but has no aero?
Like a Formula Ford chassis that allows for the bike motor?
IMHO, the additional aero allowance can make a class a real money pit.
edit- and shouldn't a tire limit keep the powertrain war pretty minimal?
In reply to Apexcarver :
OMFG that looks like a thousand tons of fun in a 50 lb bag
In reply to alfadriver :
Roadrace classes that disallow aero? Formula F (formula ford and honda fit repowered formula ford), Formula Vee, Formula First (vee with 1600cc bug engines and wider tires basically), and F500.
You could build an uncompetitive formula S car (formula S is a catchall run what you brung, so you would be up against wing cars).
Autox? you would be in BM or AM with anything formula thats bike powered and not a F500 and they allow wings. you can also run a bike powered legends car in FM againstthe f500s, but good luck beating them. other classes disallow bike motors, so no D/Emod or XP
Wings are a piece of bodywork, its another piece to make and replace if you have a shunt. That said, cost will depend on materials and construction. There are decent ways to make them from aluminium or fiberglass that arent too bad (look into how EAA does some construction). There is a lot in setup and driving style that comes with it though. and yeah, top of the line CF gets spendy
There is a lot to consider about why F500 is the way it is. Much of it centers on "how can we build a fast formula car as cheaply as possible" which is awesome to me.
point is, if you are worried about aero cost, theres reasons to not dismiss F500
Jay_W said:In reply to Apexcarver :
OMFG that looks like a thousand tons of fun in a 50 lb bag
with purchase prices close to NA miata prices for used ones...
100hp and 800lbs with driver.
tires are about $800/set new and last well (wide tires, light car)
Small enough you dont need a "car trailer". think more like what you would load a lawn tractor on. plus, car is 650lbs without driver, so you dont really need a truck or big suv to tow one, especially an open trailer.
Sorry if I am being a class salesman, but it is a fun way to go. I am also convinced that you could build one for autocross more easily than a locost and I would love to see a crop of GRM custom Fmods.
Here it is with the body on. (body is just fiberglass held on by dezus fasteners) and the relevant thread is here https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/so-i-went-and-bought-a-racecar-f500/146445/page1/
I run a F500 as well, both at autocross and vintage road racing (my car is an 87 Novakar). I've owned a Formula Vee and a bike engined D-Sports racer prior to the F500; the Vee was cheap but kinda slow (they are fun) the D-sports was really fast but ferociously expensive to own. My cousin runs SCCA P2 (formerly D-sports) and that car has 8-10K worth of Ohlins dampers on it. Motorcycle engined single seat race cars rock but most of the SCCA classes are running factory built cars that cost 40K-100K. If you don't care about how competitive you are and are only running regionally, then build one and go have fun.
I'm just fanning the flames:
Formula Jedi on-board video at Brands Hatch:
So we ran this thing pictured below. It was home built and Yamaha 1000 powered and had moderate downforce generated by the underbody. It pulled over 2Gs in a corner and 3Gs on the brakes. The motor was making around 175hp in a 1000lb car. The lap times I turned at my local track were about 1 second a lap slower than the Trans Am lap record. From a driving standpoint they are fun but probably not the first place you want to start in a single seater as the speeds are such that getting it wrong can go very badly very quickly.
I think you should build one..................you won't be bored.
In reply to Apexcarver :
Missed your post a few days ago- the only reason that I was looking outside of F500 is the powertrain. Opening that up to chain driven motorcycle engines seems to open up more options of what to get. I had thought there had been posts of a 4 stroke equivalent to F500.
I always loved the sound of FSAE cars when they came out to events. Not so much the two strokes.
(and it's not as if I'm planning on a return to autocross... if I were, it would be a street tired version for my Alfa).
The standard motorcycle engine for F500/600 seems to be the GSXR 600; my understanding is the packaging of the motor is such that it best fits in these cars. Also the only mod they need is a baffled sump, which is available for sale at a very reasonable price.
A two stroke is the way to go for autocross (mostly due to the CVT). 4 stroke snowmobile engines have been talked about for some time but SCCA really isn't motivated to make that change.
Mmmm yeah, most people don't like the sound of two strokes. I started road racing on two stroke bikes so they sound great to me, especially things like Yamaha TZ250 & RD350s.
Two strokes are also easy to maintain as is the CVT clutch set up. The motor in my car had done 42 autocrosses, plus 5 race weekends and all I've done is rering it. I've had to shim the primary clutch once to adjust the belt clearance.
I spent $2000 for the car & $1300 to ship it. My car came with the obsolete AMW motor so I started buying up Rotax 494s, I spent $2100 on 4 running Rotax engines and some spares. I had to replace the fuel cell this year so I upgraded to a 6 gallon cell which cost me $750. I spent an additional $300 on parts to make the car more autocross friendly, so I'm into the car for $6500.
At autocross the only thing faster is my buddy in his shifter Kart.
Yeah, the 600cc bike engines are 4 stroke chain drive using the bikes transmission. Cable operated paddle shift seems to be the popular solution, but I havntt messed with one yet. (I did play with an electropneumatic driven off a paintball CO2 when I was in FSAE, honestly it was a royal PITA)
I think the only thing Tom forgot to mention is a requirement for flat plate restrictors. They are kind of trying to equalize out the snowmobiles vs the bike engines, but the other thing is that it is kind of mooting the point of digging into the bike motors. People are winning runoffs on junkyard bike motors. This is a good situation for costs.
The two stroke has its strong suits. The CVT for autocross is a pretty big one. I have also heard of replacing pistons with the engine in the car in an hour and a half. They are rather simple once you understand them. I am still digging a bit into the clutch tuning aspect, but no problems, just trying to get the last bits of speed. Minuki carbs are pretty understood too. People having problems with the newer motors (494, 493, 593) are usually getting too aggressive with leaning it out and compensating for weather at the razors edge from what I have heard.
If I didnt care about autocross and I was starting from scratch... BIKE MOTOR. They may be more complex, but they are much more consistent and had a lot more made, so are a lot easier to find a replacement for than a snowmobile engine. I try not to care how my car sounds as long as its fast, but I will say that the 2 stroke drones and the bike motor is just awesome sounding. I would go bike motor all the way.
I have a 494 snowmobile setup car because they are cheap on the used market and to fit a bike motor into mine would require reengineering from the roll hoop back on the chassis to fit it. Plus, I autocross.
Here are the engine options at present. (page 261 of the SCCA GCR)
The biggest problem I have with the bike motor is short shifting on accident. 16k rpms is not something a car driver I'm used to, so I've been known to shift at like 10k when I feel like the motor must be close to redline.
It's not. It's actually just starting to boogie.
Fun fact - I watched a video interview with a student who did the fuel maps for FSAE at Kansas recently. He was asked if he worries about knock on his engine (600cc honda maybe?). He said something along the lines of "no - we don't really worry about knock because the motor is physically moving so fast that the knock isn't fast enough to hurt anything. It's not best for power production of course."
@apexcraver, yes forgot to mention the restrictor. As for CVT clutch setup I'm suing the 98% clutch set up from the F500.org website. I've never bothered with the last 2%, granted I'm the only F500 locally. As for jetting I always jet the motor fat, the extra 2hp is not worth the chance of damaging the motor. I'm also lazy when it comes to jetting, I set it for the winter months and live with the fact that I lose a little performance in warmer months. Note I don't run our summer events (it's 107 out).
@robbie the bike motors have a rev limiter. The standard upshift procedure when I raced bikes was to preload the shifter, when the motor either fell out of the powerband or hit the rev limiter it'd upshift. Granted I raced bikes where the powerband started at 10,000 RPM.
In reply to Robbie (Forum Supporter) :
Most of the guys roadracing are using a dash that you can set up to have a progressive shift light (series of lights that light up left to right in green, yellow, red)
So you can have a visual. there is adjustment to taking on any new car though.
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