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JMortensen last won the day on August 21 2022

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  1. Autox but will be doing track days hopefully next summer. Track should have me doing 140 - 150 at the end of the straight, from what I hear.
  2. I think tube80z shared that with me a few years ago. Made me regret that I had installed my fuel cell at a 7* angle because when I did it 7* was considered the max angle you could run without separation. He's talking 20* in there though. That's way outside of what I would have thought would work. I think when I do build one the focus will be on making it as long as possible and I may try to change the angle along the length. Been looking at AJ's gigantic one, and it appears that maximizing the angle in that particular space is the focus, rather than sticking to a particular angle. You can see it kinda steps up past the axle, then flattens out a bit under the gas tank, then steps up again at the end. https://ajhartmanaero.com/modular-diffusor/
  3. Here's something that really surprised me when I read it: diffusers actually work best when the air starts to separate: https://www.racetechmag.com/2017/08/willem-toet-explains-motorsport-diffusers/
  4. 4. This doesn't seem counter-intuitive, as more lift on the front end will tend to make the car understeer, and that's the more inherently stable tendency. 5. I'm sure I read in a book somewhere that lift or drag translates directly to work. If the airflow is doing work it will show up as force on the car. So as calz says, if you clean up the airflow under the car so that it isn't turbulent, you can reduce drag and lift, as it has to do less work to get under the car - acting less like a parachute. If you have a lot of lift, that's a sign the the air is doing more work. Closing the huge hole in the front and ducting to the radiator prevents all that air from packing into the front and pushing up on the hood. This will reduce lift and drag. A spoiler on a Z reduces lift and drag as well (to a point, after which it will reduce lift and increase drag). 7. The further away from the axle the more leverage you have too. So a rear wing can be mounted lower and further back and make more downforce than the same wing mounted in cleaner air and higher in some circumstances. Thinking back to what might be the same video about splitters, I think his view on the shape of a proper splitter is a little simplistic. Most of the time on a race car you're rule limited, or you have practical constraints that limit the shape, but in the more unlimited classes you see the upturned nose of a splitter or a raised tunnel entrance in the front. There are also interesting front wings on open wheel cars that we can learn a little bit from where they have unusual profiles: relatively high in front, flat and close to the ground for a bit, then sloping up at the back. Not unlike McBeath's drawings of what an undertray should look like, but with a more wing-y looking top side. Most low level race cars use flat splitters, but diffuser on the splitter kind of aim for the same sort of shape in the back as the wing. If you're going to design a splitter I'd suggest a close look at what AJ Hartman is doing. He's working with high level aerodynamicists, does lots of CFD and wind tunnel testing, and makes good stuff. Then he makes youtube videos telling you how to DIY it. Pretty amazing, really. Note the front lip shape. Sharp on top, rounded on bottom.
  5. I've watched a bunch of his videos on youtube and ended up buying a bunch of pressure pucks and five 1" manometers to do some track testing. Of course I bought all that shit and then put the car down and spent the next year doing other stuff. Still need to make a temporary dashboard to hold the gauges. The one thing that he really bugged me with was his refrain that "you can't just slap a splitter, diffuser, and a wing on and make downforce" which he said quite a bit IIRC. I ended up linking in the youtube comments to AJ Hartmann's company, because that's exactly what he sells, and it obviously works. I haven't watched anything in a few months, but I did finally find one where he added I think it was a splitter and wing and was like: "HEY! That really worked!" As you mentioned though, he has a ton of good info and practical techniques in his videos, I can imagine the book will be better. Did a lot of coast downs for drag measurement too as I recall. Anyway, thanks for the heads up. Will purchase.
  6. Read your previous post, if it's plugged at the wheel cyl probably just need to rebuild/replace.
  7. What worked for me with an entirely new brake system was pushing fluid backwards. Open the bleeder, use a tube feeding syringe to force fluid to the master. I tried everything; pump/hold/open bleeder, gravity bleed, repeated pumps with hose submerged, vacuum bleed, couldn't get a pedal until I reverse bled. Good luck. It was frustrating as hell for me. https://www.amazon.com/Syringe-Adapter-Feeding-Refilling-Drawing/dp/B07SQC95DT/
  8. This doesn't look like the more aggressive NISMO one, looks like a Z31T LSD. That's probably a good thing. They're plenty aggressive as it is. You might open it up and see if it has the big washers on the sides. If so, that's a pretty big weakness. You can get some clutches from Gary Savage if he's still making them: https://www.facebook.com/garysavage42 or pull the clutches and have 4 more of the ones with the tabs on the inside laser or water cut. Here is a write up on installing it.
  9. You can mod the shifter if you get the shorter trans, may require some surgery on the center console if you're running with an interior. Sounds more race car based build though. With regards to weight distribution I can tell you I went from the L6 and 49.5F/50.5R to the LS 52/48 and having changed the spring rates and alignment, etc that the "nose heavy" LS version turns in WAY harder than the L6 version ever did. I moved the engine to the right 1.5" and have the right head about 3/4" from the firewall, had to cut part of the trans tunnel to fit the bell housing. Spring rates are 600/700, no rear bar anymore. The point is you can work around the weight distribution issues. In a more extreme example, I used to autocross against the Mustang guys at Maximum Motorsports. Fox body Mustangs have a ridiculously bad distro of something like 60/40, and MM made those pigs fast. EDIT--will be harder to avoid understeer with staggered tire setup.
  10. Pull it off, check the end of the crank and the slot for the woodruff key. Pretty common for the slot to break. Happened to me.
  11. This is pulled the FSM, just in case he doesn't respond.
  12. All that electrical makes me feel functionally retarded. Nice job.
  13. I think the reason the whale tail works is that it lengthens the car and the flow tries to stay attached longer, and this reduces some of the ill effects of air from underneath losing contact and becoming turbulent, and also redirects the air coming off of the top, which would otherwise be traveling down and creating lift. I think this is why the drag racing spoilers work too. I've wanted to see wind tunnel/CFD data on this forever. The one think that I think might be an issue is that if the tail is TOO long it might insulate the wing's upwash from the bottom of the car. I think you want the wing to pull air out from underneath, especially if you have undercar aero, but since we both have (or will have) wings hanging off the back a ways, makes sense that the spoiler can be a little longer. Spoiler angle and length with wing is definitely something worth testing.
  14. It's not multiple disk. Looks like your typical CF pressure plate with a standard disk rather than their dual friction disk which has pucks on one side. I remember you talking about double or triple disk button clutches, but FWIW, I've seen quite a few Center Force pressure plate failures online where the weights fail, and had a friend with the dual friction that chewed into the flywheel and tore up the thrust bearings in his CA18DET engine. Avoid.
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