Can you please decipher what this means for a newbie trying to learn about the class?
Thanks.
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There are Three Rotax 2-Stoke Engines in the F500 class
1) Rotax 494 (Rotary Valve) 2 Stroke Engine - Appox. 105Hp
2) Rotax 493 (Reed Valve) 2-Stroke Engine - Appox. 105Hp
3) Rotax 593 (Reed Valve) 2-Stoke Engine - Pro Bulid Appox. 115Hp - per the lastest post
There is also the Motorcycle Engines
4) 600cc Motorcycle - 4 Stroke Engine - Pro Build Approx. 115Hp - per the lastest post
I did not want any confusion about the Rotax 2-Stroke Engines. The 115Hp only applies to the Rotax 593 Engine.
The First, Third, Fourth, & Fifth Place finihing cars at the Runoffs were powered by 600cc MC Engines.
The Second Place finishing car at the Runoffs was powered by a Rotax 593 Engine.
The Sixth Place finishing car at the Runoffs was powered by a Rotax 494 Engine.
There were no Rotax 493 powered car at the Runoffs.
Rotax 494 & 493 Powered Cars - Minimum Weight - 800lbs
Rotax 593 Powered Cars - Minimum Weight - 850lbs
600cc Motorcycle Powered Cars - Minimum Weight - 900lbs
All of the Rotax 2-Stroke Powered Cars have a CVT/Clutch Drivetrain
All of the 600cc Motorcycle Powered Cars have a Gearbox Drivetrain
Rotax 494 & 493 Powered Cars - No Inlet Restrictor Plates
Rotax 593 Powered Cars - 25mm Inlet Restrictor Plates
600cc Motorcycle Powered Cars - 28mm Inlet Restrictor Plates
F500 is a Restricted Class it is not a Spec Class!
You tell me what you think it takes to learn this class?
Thanks for the engine details.
Ah, things were simpler when everyone ran the same Chaparral 440 engines. *ringdingdingdingyawwwwwwWWWWWWding ding ding*
True clint had a problem in the race and failed a suspension rubber due to exhaust heat. Brian had the pole over Clint by about 2.5 seconds and gapped Clint by about 2,5 seconds on lap 1.
All i am trying to say is that a 593 powered car was much faster than a 600cc Suzuki with 30mm restrictors.
I've used 2 different engine builders for my 06/07 Suzuki motors. The best dyno sheet either could produce for me (with 30mm restrictors) was 107 hp @ 13700 rpm, with 46 lb-ft torque @ 10250 rpm.
That's hard data.
Remember an "engine build" in this class means fresh (stock) rings and (stock) gaskets to get the compression up to (stock) spec, a (stock) valve grind, and a set of high strength rod bolts.
I think the RunOffs this year demonstrated that a top driver with a 593 and a top driver with a 28mm restricted MC will be very competitive on a long, fast track. I'd gamble the 593 with a well set up CVT would be dominant on a shorter, tighter track.
Personally, I'm not in this to win the RunOffs. The folks in the class are great to hang around with - from the front runners to the back markers. The cars are a BLAST to drive! And I am not braking the bank to run mid-pack in a Major's race (I've been on the podium more than once!) and up front in a Regional (I've won my share in SEDiv).
Find a good car - FV or F5 - and go have fun! Don't feel like your 1st choice is a life-long commitment. If you try F5 for a year or 2 and don't like it, you can always sell it and move over to FV, or vice versa.
George well said, there really isn't a wrong answer when it comes to picking either class.
I'll reiterate what I've said before; Many moons ago I had a FV and even gave thought to getting another one but I really wanted to go faster. After driving an F500 at an autocross I was sold. The double bonus for me as a regional level guy is I can autocross and road race the car. In my case the road racing is vintage racing.
I was glad to see Wieda run up front at the RunOffs as I showed it is possible with a two stroke car. There was also great racing throughout the field.
When I was at the vintage races earlier this month I got lots of positive feedback on the car, loads of people asking what it was and various technical questions. I'm also hoping that the older cars will start making their way into vintage racing.
I'm still of the opinion if more people drove one of these cars there would be a lot more people running one.
The flow difference between a 28mm diameter restrictior with an inlet radius ànd a 28mm restrictor with a sharp edge is about 20 %.
When i did my first MC dyno test the tech guy at the scca told me to use a specific set of sizes with the same radius on all sizes. After i turned in the data one of the SÇCA tech guys called me up and told me to redo the testing with sharp edges and .125" thick plate but by this time i was personally out $4500 to get all the work done so i borrowed the use of a flow bench and then compared the flow bench results between the 2 different types of restrictors and I wrote a report and sent all the bits and data to the SCCA tech people as requested. I made no recommendations for the restrictior sizes at all, I simply supplied the requsted data to the club
I do not know who made the decisions at the club but the club people made the decision to start the 600cc mc powered cars as a regional class only. The MC powered cars were regional for 2 years before the classes were merged into one National class.
There was a lot more involved but the above may give you a tiny idea how much was involved!
If you have any questions just ask and I will do my best to answer your questions.
The above is just a part of my involvement but i cannot imagine how many man hours the club people contributed to the total effort, and I personaly thank them all!
My understanding that when the MC motors were in the gestation stage for F600/F500 competition. Bill Kephart a CRB member at the time and Formula Ford driver since about forever did not want to see the MC motor cars be given their own Formula (extended wheelbase and a number of other 'desirable' features as he felt that such a car would gut FF as the cars would be faster and cheaper..
Until FF adopted their Spec Tire, it was a toss up of who was faster FF or F500. The spec tire has made top level FF slower when compared to the top level F500 drivers.
Inhave always. Thought that f500 and f600 should have been seperat classes with f600 starting life as a regional class. With a simple flat plate 32 mm restrictor. I knew how difficult to optimize the many many variables on the 2 stroke powertrain package is! The CRB DID NOT AGREE! Now no one is happy
I actually do not blame the club for the decision that was made because the poll that the CRB took indicated that the combined class would be very popular. That did not happen, sadly.
I am still of the opinion that seperate class's are the best solution and let the class entries define the status.
The big problem at present - many existing 2-stroke cars were bought by individuals who thought putting a MC power train into a existing 2-stroke chassis would be a piece of cake - only to find after they have sliced the car apart that the necessary fabrication skills and abilities far exceed their own. Thus we now have a thousand or so pounds of junk that virtually nobody wants. A functioning race car effectively removed from any potential of being in competition again - either as a 4-stroke or a 2-stroke.
Eric, Thanks for your cordial response.
I didn’t make any claims or statements related to the Dyno Results or the 600cc MC engine. I have no interest in discussing or arguing about 600cc Horsepower numbers, I don’t own one!
These are the Dyno results that where originally posted. The only reason I posted the Dyno Results was to show Unrestricted Horsepower for the 600cc MC Engine. Someone can correct me if I’m wrong but I don’t think there’s any restrictor edge radius effects are involved with the Unrestricted Horsepower shown on the graph.
Again, Thanks for your cordial response it’s appreciated!
My current racing plans for 2021 are to only race at SCCA Regional Events and spend absolutely none of my money at any SCCA Major Event or attend Runoffs that would contribute to the F500 participation rate. I will also not be resubmitted my proposal to the CRB (that I spent 8 months working on last year) which if approved would change the restrictions on the Rotax 494 powered cars to try to improve the participation rate in the F500 class.
George, thanks for your 30 mm dyno info. Does anyone have dyno data on a 600cc mc engine with 28mm restrictors that they can share?
BTW when Brian won the runoffs with the 593 2 stroke with the required 25mm restrictiors and Clint had a 600cc GSXR600 engine with 30mm restrictors. After the race I wrote a letter to the CRB requesting a 31mm restrictior for the next year. I suggest that you look at the video from both of those races. Imo the proper restrictor size for the 600cc motorcycle engines should be 30mm for equal acceleration from 60 mph to 100 mph with the 593 2 stroke engine. I hope that the SCCA instrumented both 2 stroke and 4 stroke cars at the last Runoffs at Road America!
Comments please!
Blank post
Away from signal for three days, and will reply to those posting in regards to my posts. Thanks.
So far as the post just above, Geez.
It may be clear to somebody who knows what you mean. However, stating the 115HP only applies to the Rotax 593 is contradictory to you listing the 600cc 4s at 115HP. That could lead to confusion.
1) 494, a rotary valve 2 stroke produces around 105HP peak.
2) 492, a reed valve 2 stroke produces around 105HP peak.
3) 593, a reed valve 2 stroke professionally built produces around 115HP peak per the latest post.
4) 600cc, MC 4 stroke professionally built produces around 115HP peak per the latest post.
I think at this point in the game the weights need to be evened up then trim the remaining balance of performance with the restrictors. Now that the two stroke is about 1mph faster on top end (same car 2 stroke vs 4 stroke) the weight is a huge advantage under braking and in the turns. 50 pds difference on a four mile track is a huge amount when the MC cars are no longer faster on top end.
Thanks Daryl, great info and pretty consistent with what I wondered. Especially the part about Vee and heads.
I imagine that Vees May hold a little more value on resale, given its class longevity and health. A might early in thinking about resale but a factor in what we do, if we do.
It may work out that an arrive-and-drive may be a better fit, in which case SRF3 is also to be considered. But we get those fees add up quick... and whatever we do, we want to run our own car if a few paid sessions confirm “we’re in.”
Thanks again.
Thanks for that and all the work you put into it!
When you list “competitive engine hours,” do you mean in Majors? I was under the impression by a few Vee guys I’ve talked to that they needed rebuilds after maybe 20-30 hours, am I way off?
It does make sense to me that a WC bike motor can run quite a bit longer than a Vee, competitively.
Yes, Majors/Runoffs level competition was the scenario I asked about. Specifically, I asked:
The discussion from the FV community is here. That number 53 hours is iffy, as I didn't get much info from the community (and I'm not an FV owner myself). If you have better data, let me know.Quote:
This data represents the cost to run a nationally competitive effort (win a Majors race or be in the top 5 at the SCCA Runoffs). Not a cost-is-no-object car, but a very good car. In some classes this is usual (FE2 for example), while in others less common (SM). In many classes you can buy and operate a car mid-pack at Regional races for significantly less than the numbers here.
A session is defined as 25 minutes on track.
A weekend is defined as eight sessions: three practice sessions on Friday; practice, qualifying, and race on Saturday; and qualifying and race on Sunday; for a total of 3:20 time on track.
A full season is defined as eight weekends; for a total of 26:40 time on track in a year.
Operational cost is the cost of tires + engine + gearbox + fuel + brake pads + chain. These are only the major, predictable costs to operate the car during the event. There will be other smaller operational costs (changing engine oil, brake fluid, etc.), plus longer-term maintenance costs as items wear out, plus unpredictable costs due to damage, plus other weekend costs such as event entry fees, towing to the track, hotel, food, and so on. Total cost of racing, including depreciation of the car’s value, over a long term (a number of years) divided by number of weekends raced, will be significantly higher than this per-weekend operational cost. The numbers above are intended to be useful in comparing classes, and should not be construed as the total costs of a weekend of racing.
Engine and gearbox scenario: you have a pro-built nationally competitive engine and gearbox (cost was part of the purchase price listed). It produces this power for some amount of time, and then starts to fall off, and at some point is no longer competitive. You take that engine back to the pro builder, who does whatever is necessary for that particular engine (some classes more, some less) to make it competitive again. How much does that cost and for how hours on track will it be competitive?
Greg
Appreciate it, Greg. :thumbsup:
I stopped counting about 10 years ago because i did not like the numbers i kept getting !
Greg:
IMO under the current GCR Engine & Weight Restrictions for a Rotax 494/493 (500cc 2-Stroke) powered car it’s almost impossible to meet this cost criteria in the F500 class. In a Cost-is-not-an-Object scenario it may be possible. Changes to the GCR Engine and/or Weight Restrictions for Rotax 494/493 (500cc 2-Stroke) powered car are required to be able to meet the criteria. Winning a Majors race is dependent on number of F500 entries & type of F500 cars entered.
Mike Mueller’s Runoff’s Winning Cars were Cost-is-not-an-Object cars
Runoffs Highest Finishing Rotax 494 Cars
2017 – 4th Mike Muller
2018 – Only 5 Entries, Winning Car DQ’ed,
2019 – 8th Jay Beckley
2020 – 6th Steve Jondal
Scott
Imo there is no chançe for a 493 or a 494 to be competitive against either the 593 enginè or the 600.cc mc engines!
OK, I just report what the various communities tell me for their class. I'm not a member of the F5 community. I've never owned or driven an F5.
Why don't you take it up with the F5 community and get back to me with a set of numbers, and I'll put them in the spreadsheet.
Greg
I dunno, seems like they're getting too fast. Maybe change to requiring a Smart Four2 engine & trans that puts out 89 hp?
(I'm kidding of course, but an engine like that would be great for an H-Mod resurrection, that and Kei-car installations. Should be fairly affordable, what?)
Clearly you don't understand what I'm saying. Lets try it a different way. The car with the current engine on your Spreadsheet can't be built without changing the rules! No set of numbers exists for an F500 car with that engine that fits your Spreadsheet unless SCCA changes the rules.
Jay Novak said
Imo there is no chançe for a 493 or a 494 to be competitive against either the 593 enginè or the 600.cc mc engines!
I will tell you how to fix that. Make the 593 cars run at 900 lbs, make the 600 cars run with a restrictor one size smaller, and make the 493 and 494 cars run at 800 lbs. Fixed, done deal.
My last 494/493 proposal (that may need tweeked) makes no changes to the current Rotax 593 or 600cc MC engine & weight restrictions. I'm trying to make these changes without putting the 600cc MC engine through yet another restrictor plate change.
1) Allow the 502 159-Degree Rotary Valve in all 494 Engines
2) Allow 40mm Carbs in the 494/493 Engines (was not in my first proposal)
3) Reduce Minimum Weight to 775lbs. in the 494/493 Powered Cars
This proposal makes no changes to any Rotax 593 or 600cc MC cars at the front of the pack!!!
If there’s no Rotax 494/493 car/driver combination that can win if these changes are made then
what’s the problem???
The only thing I see wrong with this is when you increase the weight on the 593s and we will have the braking problems the mc cars have. I would like to help the mc cars out with weight but then you are going to get the top end and acceleration changes that go with it we just got the 593s and the 593 close for the first time in four years. If we do anything maybe. bring weight down on mc cars to 850 and smaller restrictor. Then put a 36 carb on the 593s. We can not keep adding weight to these cars. If someone could give us data on the 494 motor with the 40 carbs and the other rotary valve. Then maybe that would be the way to go but getting these cars down to 750 would also not be wise for safety reasons. If the 494s could do this then also make a pipe rule on those cars so we do not go into pipe wars like we had for awhile in this class. you could probably go with a 44 carb on the 494s. They do not make 40s anymore. Or they are hard to find. Not quite sure about 40s. Rotary valve motors like big carbs. there may be other options on the rotary valve that may help that motor more with the bigger 44 carbs. Another question would be do you want to go with the rave valve or non rave 494s. there are alot more non rave cylinder motors that were made then the rave motors.
F500 is a Restricted Class, it's not a Spec Class. The class restrictions need to be open enough to allow racers to build cars that are competitive within that set of class restrictions. If racers cannot build cars that are competitive within the class restrictions then the restrictions need to be changed.