horizenjob wrote:
Quote:
the s2k diff is smaller and I like it's mounting setup better but supposedly it isn't as strong...
This car will have so much less weight on the tires that the diff strength is likely much less of an issue. If you have half the weight on the tires, you'll only be able to put half the torque thru the diff...
I'd agree that the weight is massively reduced on the smaller car but I would also say that by stepping up the size and adhesion limits of the tires that it isn't directly half the torque pushed through the driveline. a hard prosolo drag launch on R comps even in a 1400lb car is going to put more stress on a diff than hard street driving on 350 wear tires on a stock car.
Driven5 wrote:
Tongboy wrote:
the s2k diff is smaller and I like it's mounting setup better but supposedly it isn't as strong...
Not as strong how? From what I recall, in the Miata world it's generally accepted that the S2k differential is based on the 1.8L Miata differential, but actually offers a stronger drivetrain due to a shot peened ring and pinion and its use of larger stub and half shafts. I know there were some issuse with the case strength in the AP1 cars, but remember too that the S2000 is both heavier than a Miata and has forced induction Miata power. Off hand I don't know of any direct comparisons to validate whether the early case is physically any weaker than the Miata ones. And speaking of weight, don't forget how much less (~50%?) of it the differential will have to fight in this car. Especially considering the stated purpose of this car, I personally would probably be looking moreso at which setup is lighter...And wouldn't forget to post the weights for the others on this site who have inquiring minds.
From what i've been able to find the s2000 diffs aren't terrible for stock power levels but they tend to break whatever the bearing holders are that hold the diff into the casing (like lower rod arms breaking, i just don't know the proper name) they sell a few kits to strengthen it but the miatas don't have that as a failure point - they'll toss axles and shred gears, I suppose it's six and a half dozen either way. I do agree they certainly hold more power factory spec to factory spec by far. both setups deal with roughly the same torque output from the factory FWIW.
Total weight of the diffs isn't something I thought of - that's a good point. I'll have to throw them both on the scale for equal comparison. I also want to find out if the driveshafts are compatible - the s2000s are wider than i'd like to use but I could work with them - i'd then have to check if the outboard CVs are compatible to the miata spindles as well...
homebrew wrote:
Hi Tongboy, good to see another Portlander building a seven. I finished mine when this forum was just getting started so I never developed a build blog of my car. But circumstances have changed and soon I will start one to document the changes I am making to satisfy a local racing organization that questions the safety integrity of these cars for track days. Which brings me to why I'm here. When I saw your title stating you plan on a track toy be advised that rollbar requirements vary widely depending on who you participate with. Since you are at the beginning stages I would start thinking about the rollbar now and incorporate it into the chassis before it becomes nothing more than an after thought like they more or less are now with the original design.
It seems most race sanctioning bodies want the main hoop to start on the lower frame rail then up to the required height and across the cockpit to the opposite side lower frame rail then tie in your upper frame pieces to that hoop. If I were to build another car that is how I'd start. If you look around on this site there are some good examples of this type of construction.
I have a friend with an Ultralite that has the S2000 engine and trans. I think it's a good choice for these cars. We should have meet up with all the builders and owners in the Portland area like they're doing in other areas. Good luck with the build and if I can help with any questions feel free to contact me.
Jim Larfield
Hi Jim! Thanks for the great information. I'd love to chat rollbar design with you as I really am at an ideal phase in the project. My intention was to run a 5 point rollbar and try and get as much rear arm angle as I can. And then run a seperate full cage that bolts up toward the windshield for wheel to wheel racing. You've got me thinking about maybe a more permanent main hoop and a front hoop integrated into the cowl area with the appropriate ties. I'm trying to meet the SCCA road race regs which will get me the scca solo2 rolled in and be meaningful when chatting with the NASA guys if I head down south for any of their events. I'm told conference runs somewhere near the scca specs but I haven't been able to talk extensively with anyone there yet. Any experience you'd be willing to lend would be much appreciated.
oldejack wrote:
Here's the club brother Phillip is in. .... He tells me that they have a couple of Locost7s. (hmmmm plural of Locost7. ..
)
http://www.eescc.org/I've run an autox with those guys, very friendly and welcoming folks. I'd like to run their next hillclimb if I can get out of design paralysis and get moving forward.
I know a friend of a friend with a crazy powerful LS-powered locost car that runs with them on a semi-frequent basis.