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Small update - I've been running with an open differential since day one. It was sufficient for the street and even autocrossing with the stock ECU/intake. Once the MS and the ITBs were installed and a little more power was available, it was evident that unloading was a real issue for autocrossing and track days.

I purchased a Miata Type 2 Torsen a few weeks ago so hopefully this is the fix. So far the swap into the RX7 housing has been pretty painless. Once I get some larger calipers and set the bearing preload everything should be ready to go back together.

Before:


After:

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-Andrew
Build Log
Youtube

Andrew,
You may need a whole new driving style. Might have LOTS of oversteer like the solid axle go-karts I used to run. Can you say sideways? Ta-dah!!!! Maybe we'll get out to see you this spring?
Don

I'm kind of figuring something will change - hopefully for the better.

I still need to add more ackermann to the front. I'm crossing my fingers and hoping that the geometry change will help the mid-turn front grip and the LSD will reduce some of the on power under steer along with keeping the inside wheel from unloading. The Sprite has a spool in the back so if nothing else it will be good training.

You guys definitely need to make it out. Steel Cities posted their schedule and autocrossing is tentatively scheduled to start on May 11th.

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-Andrew
Build Log
Youtube

After the first event of the season I'm happy to report that the Torsen swap was a success. I've never assembled a differential before so I was a bit nervous about missing something and having it whine like crazy or do something else bad.



The on-throttle characteristics are noticeably different but much better and you no longer need to drive around the inner rear tire's grip.

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-Andrew
Build Log
Youtube

Reading threw your build log. Came across this post. We test tanks at work using a similar method. 2 lbs of air and spray soapy water over them to check for air leaks. We had a guy put too much air in a tank and blew a head off one.

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30 years old, not sure what I want to be when I grow up…

Also, do you have any more pics of your oil pan? Great looking build btw. Not sure how I missed this one.

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30 years old, not sure what I want to be when I grow up…

Thanks.

Unfortunately those pics are all that I have. I didn't take very many of the chopped pan - it was literally a stock pan that had been chucked in the mill and the bottom was trimmed flush with the bell housing. I never had oil pressure issues in hard turns so I never bothered to get fancy with baffling.

Funny you mention that story - I once suggested that same method to someone that was trying to find an oil leak in a tank but failed to mention using only a few psi. After not being able to find the leak the first few tries, he cranked it up to 100 psi. We later found out that the tank was designed to 1/3 of that. On the plus side it was over designed but the manufacturer was less than amused.

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-Andrew
Build Log
Youtube

Wow, Im shocked he didn't destroy that tank. We test no more then 5 psi unless its a pressure vessel and those can go up to 900psi. They are also 1-1/2 to 3 inches thick.

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30 years old, not sure what I want to be when I grow up…

People generally don't understand that psi is pounds per square inch.
A little story about an industrial accident from early in my career.

We had these HUGE autoclaves at work. The doors were about 8 feet in diameter, weighed a couple of tons and hung on hinges with pins bigger than my wrist, and closed using multiple bolts like a submarine hatch.

One day a fairly new operator got in a rush to get it unloaded. Valves were opened and it was bleeding down. At about 5 psi he tried spinning the wheel to open the door and it wouldn't budge. He thought it was stuck, so he attached the hook from the gantry crane and hit the up button....

End result the autoclave slid back a few FEET through the wall of the building and the door went flying across the shop with the gantry crane in tow.
Thankfully no one was killed.

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Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

We had a close call at work with a big heating unit. It was a steel tube about 6 or 7' in diameter and 40' long and not rated for anything more than atmospheric pressure. It's made of approx. 1/4" steel with just flats plate bolted to flanges for end caps. A valve somewhere in the system stuck open and the relief valve didn't work properly, and the whole thing ended up somewhere around 200 psi, while filled about 3/4's or a bit better with oil at 400 degrees. Just sheer luck that it didn't burst. The gaskets at both ends leaked a bit and the flat end caps are no longer flat. Pressure can do some scary things when large areas are involved.
Kristian

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V6 in a book frame build. Now registered.
viewtopic.php?f=35&t=7587
viewtopic.php?f=33&t=18172

Pressurized fluid is worlds better than pressurized gas. The energy in compressed gas is exponentially larger. Had the tank been empty when it was pressurized, it would have been more likely to cause serious damage.

Most of the time that's true, but not in the case of steam. BLEVE's (Boiling Liquid, Expanding Vapour Explosion) are really scary stuff. Water expands about 1700 times it's original volume when it turns to steam, so basically the same as a pressure vessel at 25,000 psi.
The close call we had was with heat medium oil, so wouldn't vapourize, just would have been a hell of a mess. But the vessel was only about 3/4s full of oil though, and was pressured up with natural gas, with a giant burner and fire tu e going through the middle of the works. I still wouldn't want to be anywhere nearby if it let go.
Kristian

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V6 in a book frame build. Now registered.
viewtopic.php?f=35&t=7587
viewtopic.php?f=33&t=18172

I'm thinking the oil inside kept it from busting. 1/4" metal isn't thick at all and engineers don't call for much more then a 1/4" weld for that thickness of material. At 50psi I think was when that tanks welds couldn't hold anymore. That's crazy to think that tank held 200psi.

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30 years old, not sure what I want to be when I grow up…

To take that one step further, this example equates to the door having 7,234 square inches of surface area, x 5psi=36,172 pound of force available to do what it did!
We have a fab shop, and for years we worked on Fuel Oil and Gasoline delivery trucks. They got steam cleaned professionally, and never tested at over 2psig. We had one incident because of a lack of a secondary safety rupture disk, and the regulator was creeping up. I think it hit 20 psig with water filling about 3/4 of the tank as a hydrotest, when the bulkhead reversed itself and tore off of the bottom of the floor. Needless to say, it was fortunate that is all that happened, but it was one EXPENSIVE screw up! We made sure to use secondary and tertiary safety's after that...

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Dismantalus, Fabricatus, Assemblus.....
Certified Welder, Certified Welding Inspector, Full Time Car Freak...In New Jersey no less!

This example is virtually the same one I use when explaining how the astronaut in The Martian taped up the door opening with plastic sheet and tape, and why it would fail.
A 6-ft diameter opening and atmospheric pressure difference would present a 62,000 lb force on his sheeting and tape. I'm amazed the othewise-excellent movie missed that goof.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
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