Prototypes, Engine Specifications?

[gfoster]

Absolutely new to this forum and thinking of getting into the SCCA Prototype classes. From what it seems though, it costs quite a bit of money starting out. Originally I thought I had a couple advantages. I have a machine shop, a small foundry, I'm a certified and very experienced welder. However, I thought my main advantage was that I have two complete and working cars that are essentially worthless to sell. A 2006 MX-5 Touring and a 2003 Suzuki Aerio SX. My original idea was to take the engines out, drop them in a chassis and get out on the track. Unfortunately, this was before I started diving into the requirements for the various classes, specifically Prototype 1 and 2.

What I'm wondering is, why in the world do all of the cars seem to be using motorcycle engines? I get that they produce a very good power to weight ratio, but is there a technical requirement stating only motorcycle engines?

Basically, I have a 2.0L MZR inline 4, 5 speed with 68,000 miles on it sitting in a car that I can only seem to get about 3.5k for at most thanks to the newer and swankier MX-5 and Mazda's huge push in advertising. That engine is a variant of the ones formerly used for the LMP2's (Please note the "variant" portion, I am aware they aren't all that similar).

I've built 2 Locosts in the past, so undertaking a build isn't all that big of a deal particularly with my set up, skill level, and general experience knowing what I'm getting myself into. Not to mention, in addition to being a general contractor these days, I have a structural steel fabrication and ironwork company so getting el cheapo aluminum from my metal suppliers and TIGing up a frame would be simple.

So, IF I wanted to build my own frame and harvest the parts off of my Miata including the tranny and engine, and honestly everything else, would I even be allowed to? I don't want to build something and find out I can't do anything with it. I know I will have to buy some things at some point, but as long as I can take care of the main components then the cost is drastically reduced thus mitigating the tears rolling down my face when it gets put into a wall.

Thoughts? Suggestions? Knowledge? Yays and nays?

Thanks everyone!

[2BWise]

The only thing you'd keep from the Miata for a P2 build would be the MZR. Even then it needs a lot of work to work in a race car (dry sump) and hotted up parts (intake, exhaust, and ECU) to make it even remotely competitive. If you're going to do a prototype build either start with someone else's project or buy a car to convert.

[Marty Nygard]

Try this thread in the SportsRacer forum for a lot of ideas and opinions plus even a separate link to a Miata sports racer thread.
http://dsrforum.yuku.com/topic/11332/Car-for-P3?page=1

[David Ferguson]

Let me summarize the engine specs for P2.

Your 2.0L Mazda MZR is specifically allowed. The internal components of the engine (crank, rods, pistons, heads, valves, cams) must remain stock. You are allowed to modify the oiling and cooling system as well as use any intake and exhaust system you wish (there are GCR rules as to exhaust exit placement). Typically individual throttle bodies are fitted. You are required to have individual inlet restrictors (designed for the ITBs), but if you wished to a single throttle body, it's likely a Single Inlet Restrictor would be added with a request (and a bunch of test data) - might be simplier to fit ITBs.

Building your own chassis is possible (and you certainly have the resources), but realize that you're up against race car chassis designs that have been optimized over the last 40 years. The current minimum weight for P2 with the 2.0L MZR is 1350 lbs (including driver). This may be difficult to achieve using the stock Miata gearbox and a separate rear end. That packaging will be a challenge, but I would love to see your creativity at work!

I converted my existing Sports 2000 to P2 specs when P2 was created. That is documented here:

http://dsrforum.yuku.com/topic/9870/...nversion-to-P2

[gfoster]

@david Firstly, thank you for the link, wonderful stuff. Question though, if the ITBs require inlet restrictors, won’t that cancel out any gains from the ITBs? I suppose throttle response time would still be reduced, but the amount of air wouldn’t really go up would it?

On the matter of the chassis, I agree with the fact that the market chassis have been tested and honed, however, using your Van Diemen as an example, they’re made of steel. While aluminum has a bad rep for not being as durable as steel, the alloy varieties, such as 2000, 6000, and 7000 series, are a third the weight and can be gauged to give better strength while maintaining that reduction in weight. When properly heat treated or precipitation hardened, the strength is equal to that of steel on an ounce per ounce basis or, in the case of 7000, exceeds it. (As a side note, 6000 series is what major car manufacturers use in some frames for daily driver cars and trucks and is frequently used in aircraft, firearms, and engine blocks.) I’m not set up to do precipitation hardening, but I have built heat treating ovens in the past for tempering engine block castings. I can justify the cost of clay and steel to build a small one for the frame as both can be upcycled.

@ Marty thanks for the link! Great questions and answers there.

@2BWise True, to be competitive right out of the gate it would be far better to start with someone else’s project or used car. For me though, I prefer the good ole days when people like Harley and the Davidson brothers pit their ingenuity against Indian or like any other of the early motorcycle or car racing teams did for that matter. Sometimes it isn’t about racing, it’s about learning what you can and can’t get away with technology and design wise and improving over and over again.



Thanks for the help guys! I may use this as a build thread.

[Wren]

Welcome to the forum.

I'm not sure if you have seen it yet, but you should definitely familiarize yourself with the GCR. Read it as often as you can.

https://www.scca.com/pages/cars-and-rules

Your rollover structure is going to have to be steel. Aluminum monocoques are certainly allowed for the rest of the frame. I've just never thought about an aluminum tube structure for any of it.

I'll give you the same advice I give everyone talking about building their own car. It's going to take a lot longer than you think and cost more than buying an already built car. Make sure that you are doing it because you want to or because you think that you can build a better mousetrap.

There are a lot of experienced designers and builders here. They are typically willing to help.

[holmberg]

Has anyone ever built a car with aluminum tubing? I've never heard of one. Aluminum sheet, yes, aluminum tubing, no.

Keep in mind that the SCCA rules say that the roll cage has to be steel (and other requirements) or has to be signed off by a registered engineer as meeting certain load requirements. See section 9.4.5 of the General Competition Rules.

You should know that document inside-out before you start building anything.

[Marty Nygard]

I seem to recall early "Modified" sports racers with aluminum tubing chassis. Porsche also used aluminum roll cages in their IMSA turbo 911 variants but I think that stopped after Cathy Rude's horrible crash at Brainerd.
M

[gfoster]

@holmberg If you’re talking about mass produced stamped sheet or hydroformed frames that’s just because it is incredibly cost effective and can be run continuously by machines. Hydroforming, specifically, is tube just put under tremendous pressure inside a die to take the designated shape. If you’re referring to hand made, honeycomb structures made from sheet that’s because TIGing aluminum round tube is a pain in the derriere because you can’t, rather shouldn’t, run a spool gun on it. Aluminum round tube frames get used occasionally for hotrods and motorcycles. Maybe not the most popular choice, but it is done.

In regards to the load requirements, I should be fine meeting those with an increased wall thickness/proper support bars. I know of some engineering professors at Kennesaw State University (formerly Southern Polytechnic) that run some kind of miniature, Formula SAE campus club for the engineering students. I’ll get in touch with them.

Sincere curiosity: Why does the rule book get updated every month? Seems like that would make it harder to keep the cars current with the rules and guidelines.

[David Ferguson]

@david Firstly, thank you for the link, wonderful stuff. Question though, if the ITBs require inlet restrictors, won’t that cancel out any gains from the ITBs? I suppose throttle response time would still be reduced, but the amount of air wouldn’t really go up would it?

On the matter of the chassis, I agree with the fact that the market chassis have been tested and honed, however, using your Van Diemen as an example, they’re made of steel.

The current restrictors (42mm for the MZR), don't make a bit of difference if you use of 42mm ITB's which will definitely improve the performance and can be competitive. Yes, they may have a bigger effect with 45 or 50mm throttles, but you would never need to use those on the 2.0L.

My chassis is made from aluminum honeycomb, with a steel main roll hoop. This is not the same tubular steel chassis used in the FC cars. Suspension A-arms are made from tubular steel, but uprights, belcranks, various clevises and mounts are all aluminum. Sports Racers have been made with aluminum monocoque construction since the '70s.

[Offcamber1]

Bobsy, back in the day (early 1960s) did. http://www.race-cars.com/carsold/oth...23617906ss.htm

Not sure I'd want to pump a couple of hundred horsepower through it though...

[holmberg]

@holmberg If you’re talking about mass produced stamped sheet or hydroformed frames...

No, I'm talking about race cars--formula and sports racers.

Here's an example of a chassis made from aluminum sheet: Cheetah

As for aluminum tubing, others have pointed to some race cars made from that in the 60's. I can't think of any SCCA car more recent than that though. Keep in mind, it's not just ultimate strength, it's also the failure mode--how will it perform in an impact with a concrete wall? Will it absorb energy and deform progressively? Or will it crack and tear and collapse on the driver? I honestly don't know...

Here's another site where sports racers hang out: DSR Forum Probably more there than here. There's a bunch of talented home builders there.

[JerryH]

I am 99% sure the 917 Can Am cars had alum tubing chassis....with fiberglass bonded to it in several areas.

Jerry Hodges
JDR Race Cars

[Dog Licked Racing]

One of the drawbacks with aluminum is it's modulus of elasticity - It is said that "an airplane remembers ever hard landing".

[bill gillespie]

One of the drawbacks with aluminum is it's modulus of elasticity - It is said that "an airplane remembers ever hard landing".

Uh oh, for me and Charlie Warner...??

[RussMcB]

Garrison, welcome, to this forum, SCCA racing, etc.

The monthly updated GCR is a little hard to explain, but that's how it has evolved over the decades. I think it's mainly an attempt to stay current and on top of things. Many of the monthly updates are corrections and clarifications.

Not sure exactly where you are in the ATL area, but a few of us are up in the Marietta, East Cobb area. We gather at a buddy's garage on Thursday nights. He has a Radical sports racer with a Hayabusa engine, and a few others have formula cars. You're more than welcome to pop in and shoot the breeze. Heck, it could benefit us to know about you and your fabrication abilities.

[neilca]

I agree with Russ, you should stop by some Thursday and check out the Radical and bring an adult beverage or two. I have found if 5 people show up you can count on at least different 8 opinions on any given subject. We start after 7:30

Neil Cawley
2311 Mitchell Rd
Marietta, GA 30062