Leon

I don't know why you keep blabbering on about semantics. I've been trying to help the OP while you're doing nothing but arguing. Keep digging that hole buddy...

Indeed, hahaha!

Dude, calm down. I don't think people look at the physics when they think of raindrops. It is generally referred to a raindrop shape since when you say raindrop most people see this: I don't see why you have to be so argumentative when the OP was asking why the raindrop shape is more drag efficient. You're just arguing semantics here.

I love HWY 35! That's where I'd go on every drive when my Z was on the road, with my buddy on his GSXR 750. We'd go 280>Black Mtn Rd.>35>92>35 into the mountains>84>Canada>280. We did a bunch of variations but they always involve 35. Love that Road. I'll be doing runs there and to Mt. Hamilton and Mines Road when the resto is done.

This is what I'm talking about when I say "raindrop shape." Notice, the shapes are blunt in front, slowly tapering to a point. That is a drag efficient shape. Also notice that the plane you showed was meant for supersonic speeds, meaning that it's optimal geometry will be way different when compared to aircraft engineered for lower velocities. Here is a subsonic aircraft: Subsonic airliner: As you can see, this airliner has a blunt nose and slowly tapers to a point. Of course there are other design considerations for airliners, such as fitting in many passengers and tons of cargo so the shape isn't as efficient as a smaller plane. However, it follows the general trend and utilizes the "raindrop shape."

Take a closer look at an airliner; they are raindrop shaped! NASCAR drafting is a whole other phenomenon, if the cars themselves were long and tapered they'd be more "drag efficient." As for arrows, I'd say their pointed nature is for another reason besides keeping flow laminar and decreasing separation! That aspect is minimal. As goldfish said, that is merely a small part of the equation.

Not more efficient in incompressible flow? So would you want a brick shaped skinny thing or a wing shaped skinny thing? Would you want your needle minivan to have a square front, or the blunt curve and taper of the wing shape? Can you give me your reference that says that the raindrop shape is not more efficient, I'd be surprised and interested.

Have you checked your cam timing? A retarded cam can lead to low results across the board. However, I'd check with a different gauge first to rule out error there.

Wow, that's crazy! Good luck with your project, it sounds challenging. As for FSAE, are you going to competition? We're going to Detroit this year, it would be cool to meet up. Regardless, I'm sure we'll meet somewhere, sometime! Send me a PM and let me know.

Wow, congrats!

Awww crap! What I meant to say was, when I saw that thread, I thought the same thing!

Sorry to quote all this, but WTF, you almost described me! I am 22 now and got my Z summer of '07. I was born in Moscow and I have been a car guy even before I can remember! There are pictures of me as a toddler playing with car toys and staring at busses and any vehicle that fell unto my eyes. My parents had a non-running Volga but my grandfather had a Moskvich. I was so happy to get a ride in that car! My grandfather was the first of my family to move in '91, and soon I found out he got a Ford. I was so excited about it since I had never seen one before, only the usual Lada, Moskvich, Zhiguli, etc. When we moved to SF in 1994 my dad was able to get a slightly rusty 1987 Honda Accord, our first running car in my memory! I thought it was the coolest thing ever. It had pop-up lights and a moonroof, what more could a kid ask for? I went into "learn mode" and stared and learned every make, model and year of car that I saw on the road. When a cousin came to the US the first thing that came out of my mouth was "there are so many different marques of cars here!" Whenever my dad would come home with a "new" car, like the '84 Corolla we had (Damn, shoulda kept that one!), I sat in it checked out all the cool features and pretended I was driving (who didn't?). In high school, I got my license at 16 and couldn't wait to drive by myself. Eventually I was driving a '94 Volvo 960 and then an '89 Audi 100 5-speed in high school. I was lucky enough to take the auto mechanics class as a freshman but unfortunately it was canned after that. That was when I was really able to start learning detailed things about cars and how they work. At the end of senior year, I was lucky enough to get a 2001 Accord Coupe (manual, of course). It was a dream come true! After my first year at SDSU in Mechanical Engineering (at Cal Poly SLO now) I told my dad that I really wanted a project car. I didn't think anything of it, but one day he tells me there are a couple of Porsche 944s for sale cheap nearby. Of course I jump on it but it fell through. The rest of the summer I became obsessed with getting a project. I worked as a youth basketball coach every summer, but I yearned to work on a project with my hands. Many hours prowling Craigslist and a few drives to check out 944s, and still nothing of mine in the garage. The next summer I decided to expand my search. I narrowed it down to a RWD, stick, and likely a hatchback (just love that body style for some reason, wagons as well!). The cars I was mostly searching were 944s, Supras and Datsun Zs. It was tough considering my budget was under $1000. I found 280Zs and ZXs not knowing much about Z-Cars then, but my dad kept turning them down saying that they're too much work or that they're not worth it. Finally after 2 years of searching, my patience paid off. I found a 240Z on Craigslist advertised for $800 and took a look at it. It was sitting in a driveway rusty, dirty and covered in cobwebs. The guy was cool, he said the PO had it in a barn and it drove until something happened to the carb and it would not start. I was so giddy but tried to stay focused, so I went home to sleep on it. The next day, with some convincing from my girlfriend (she knows how important cars are to me) I offered $400 and picked it up, unbeknownst to my dad! I finally decided to make an important decision on my own. I called AAA, the truck arrived and the driver comes out, mounts the Z to his truck and as I'm paying he says "you gonna put a 350 in it?" I thought it was funny because I didn't realize how common it was at the time. Finally the truck drives off with me behind it. When the tow truck was unloading at home, of course my dad arrives from work. He gets out the car, and just says "you're crazy" with a slight smirk on his face. The first night with my own car is unforgettable. I put it into the garage, took pictures and just stood in awe that it actually happened! My appreciation for these cars has exponentailly grown, and I'm really glad I got the Z. I've been addicted ever since, learning, buying parts with all my spending money, and requesting parts and books as gifts. This car has helped me learn about so many aspects of automotive engineering. It has made me essentially fearless of any car project, where before I would think of a restoration as an almost superhuman feat (hell, it still seems that way... ). My first '71 is on jackstands torn totally apart, and now I have a rust free shell with Illuminas and Eibachs that I'll be using to accelerate the project. There is still plenty to learn but I feel so happy to have a car to work on and to eventually use for fun. I could have never imagined a better outcome, even 3 years ago! I am in my last year at Cal Poly working on my senior project (engine development for our Formula SAE team). I feel so damn lucky to be able to have an amazing car, amazing community, and the opportunities I've had in life. I think this is getting corny but I feel good sharing this stuff. These forums have also been a big help for me, so thanks to all of you. They're such a great tool for taking my car love to an obsession, and the obsession into a quest for learning as much as I possibly can! Sorry for the essay, hope I didn't bore anyone to sleep!

Sooo, does that mean you're turned on by whale penis?

Hahahaha!!! That's exactly what I thought when I saw that one!

I would say it has to do with the raindrop shape promoting a laminar boundary layer as a fluid flows over it at the front. As the fluid moves down the shape its velocity increases and the flow becomes turbulent, thus more drag. That shape you showed looks like the initial boundary layer will be turbulent from the get go.

In a nutshell, the boundary layer does not separate from the surface as the taper angle of a long raindrop is not large. If you flip that raindrop front-to-back then the boundary layer will detach at the end where there is an abrupt drop-off. Flow separation results in increased drag.

Way too much for a non-running car, IMO. It looks fairly clean, but make sure you check the usual rust spots. The rust on the hatch would make me suspect that there is rust lurking elsewhere. Bring a weak magnet with you to check for bondo. By the way, it has a dash cap so the original dash is likely cracked. If the unibody is rust free, I'd offer no more than $1k but then again I'm in CA (regional prices may vary). You never know what it's going to take to get the car on the road, that's a bargaining chip.

The cylinder head is not a factor in this. It's your piston rings that were stuck!

After I got my sitting Z going the compression went up in all cylinders. Compression was about 90psi in 2-6 and 150 psi in cylinder one before startup. I forgot how much it went up by but every cylinder benefitted. It very well may have been that all your rings were simply stuck in their grooves until you finally fired up and ran it.

If it had been sitting for a while the rings might have gotten stuck and by running it you likely loosened them.

Holy cow, I'm speechless! Such a clean and beautiful Z, that is some great work.

That is part of the compression test procedure! Make sure you're at WOT while cranking. I have my brother press down the pedal, if you don't have a helper use a heavy object on the pedal.

Very nice! Looks like you're doing some excellent work there, the CAD definitely helps on a project of this magnitude. Isn't the compression ratio fairly high on these engines, something like 9.5-10:1. Any special precautions to prevent detonation?

Nice, looks like a good base to start with. The turbo engine looks very clean. Keep us updated for sure, it's going to be a nice ride!

Hell yeah! Mine will also be orange, makes me want to do the paint myself. Love the black/orange combo, I've been planning to do something like that when it's time for paint. I have the same airdam and some black slotted mags. Hopefully it'll come out half as nice as yours. Again, great job.