this post was submitted on 20 Jul 2023
1188 points (98.2% liked)
Asklemmy
43963 readers
1093 users here now
A loosely moderated place to ask open-ended questions
If your post meets the following criteria, it's welcome here!
- Open-ended question
- Not offensive: at this point, we do not have the bandwidth to moderate overtly political discussions. Assume best intent and be excellent to each other.
- Not regarding using or support for Lemmy: context, see the list of support communities and tools for finding communities below
- Not ad nauseam inducing: please make sure it is a question that would be new to most members
- An actual topic of discussion
Looking for support?
Looking for a community?
- Lemmyverse: community search
- sub.rehab: maps old subreddits to fediverse options, marks official as such
- [email protected]: a community for finding communities
~Icon~ ~by~ ~@Double_[email protected]~
founded 5 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Ok, the TL;DR is lack of aero, and weight, and we couldn't really fix it, and keep our class.
As I mentioned, we took an SR20 and destroked it to get it under 1500cc. We loving (sometimes) referred to is at the SR15VET or the 150SX. The class also limited aero. We were able to take some of the JDM body pieces off of the Type X Silvia, but we couldn't add any other aero components, and keep our class.
Our best guess, since it happened religiously at the same speed, was that it was an aero issue (mostly). Air would get under it, the car would get light and then spin. Land speed racing is counterintuitive to EVERYTHING you know about racing. Typically, you want a light as possible, and the biggest fattest tires, with relatively low tire pressure, amongst other things. You also typically want a linear power band, with progressive power over the whole range. Land speed racing is it's own beast. You want the skinniest tires you can get to work, and I swear, you overinflate them. You want the car to be heavy too. Our power band was also, basically, nothing, nothing, nothing, nothing ALL OF IT. I can't find the dyno right now, but it really couldn't get out of it's own way, and then when like 6k rpm hit, and the turbo started to get happy there was a MASSIVE power/torque increase.
Some of the old timers came by our pit, in their golf cart, and started chatting with us. They seemed fascinated by our little import, and what we were doing. So they start asking questions. "How much does the car weigh?" "2800lb", or whatever it was. "bullshit, you need to add xxx more pounds" "what kind of tire pressure you running?" we reply "xxxpsi" "bullshit you need to be over 70psi". "did you add ballast?" "no....." "bullshit. you need to talk to xxx guy, he'll tell you where to get some cement" This was really our first foray into land speed racing, and it was definitely a learning experience.
Our next course of action was to add ballast, but the thing about land speed racing is that it takes place on "dry" lake beds (typically). Here is an iconic pic of Challenger II in 2014, when Speed Week got rained out (happens a lot). They had dragged the car all the way to Boneville only for the weekend to ultimately be cancelled. And they had to take pics of the car on the "salt" of course.
The year that we went out, and set the record (same year Challenger II did) a massive storm blew in over the mountain range, as our car was in tech, making sure we could make another pass, on our last day. Well, it was lingering over the mountain range, and heading for us. I've seen what that amount of water can do, and how fast it can do it, so we decided to get the pit packed up and head out, before we were submerged. There were EZ-Ups blowing away, shut flying everywhere, raining, windy, and salt was already getting more soggy (there is only a patch in the middle of the lake that's dry enough to drive on typically. The edges are usually still lake-ish. The day we arrived, I drove the "borrowed" SUV off the end of the road, and onto the salt, but I had to drive through water to get to the pits. The water was up to about the side skirts of a big chevy SUV. When we left the salt on the last day, the water was basically trying to come in the cabin, it was that high, at that point. The whole point of that is that we didn't have time to play with any changes, and the team captain and driver weren't able to continue with the car the following seasons, so it go mothballed.
@Plaid_Kaleidoscope
@techconsulnerd
Amazing! Thank you for sharing. I've heard about the wanting heavier cars and over inflating your tires before, but I had never considered the powerband before.
I've watched a few things about land speed machines and it's truly fascinating. Especially the aero stuff. Aero seems to be the epitome example of dunning Kruger, as the more you know, the more you realize you don't know. (as I've been told)
That was a really cool picture too. When it rains like that, does the salt stay hard underneath or is it muddy?
Everything about cars is that way. You think you know something, and then you learn a little bit more of the tech behind something, and it just makes a million more questions.
As for the powerband, if you think about it, it all kinda makes sense. If you’re driving a technical, short course, like streets of willow, for instance, you want a wildly different powerband, and probably car, than you would if you had to run down the back straight at big willow.
For streets you’ll want power in the low to mid rev range. You don’t need top end, because, unless you’re dumb like me, and drive an 89whp RX7 with like 3 ft-lb of torque, you aren’t likely to be anywhere near top speed, or the top gears. But, because there are tighter, more technically corners (which you’ll slow down more for), you’ll want some lower end power to get you back out of them fast.
If you’re on a much more open, and longer track, where you may reach top speed on a straight, but don’t need to pull the car out of tight corners often, you’ll probably want power in the mid to high rev range. Using my RX7 as an example, I’d run out of power long before I ran out of straight away on the back straight. Not the right car for the job.
For land speed racing, it’s far more important to have top end power, since it’s going to be closer to wide open throttle (mostly), and probably at the end of gearing, all the time. Once you get the car off the line, you aren’t going to slow down until the run is done. In fact, there are a lot of the vehicles there that get bump started off the line with a truck. So because we wanted as much power, at the top of the rev range, we chose a turbo that would be at peak power where we wanted it, which meant it seriously made like 50ft-lb until it didn’t.
The surface is wildly varied and racing gets cancelled often because of the surface conditions. The ever hating shoe person that I am, I had my feet in the ~~sand~~ salt as much as I could. The end and outside edges of the track are where the “crunchies” are. Imagine if salt built itself up naturally to be little peaks and valleys. Stepping on it collapse it to flat. The flattened edge of the racing surface is wet enough to make little snow men out of. I know, I got bored waiting for cars. lol. But it’s relatively thick (disclaimer it’s been losing salt for many years, and there are people trying to bring awareness to restore it. Don’t go out and do dumb shit to it. People have gone out and damaged it more than once. Article here ) actual track surface is pretty well packed. It’s surprisingly cold to the touch too. It’s really weird. If it’s submerged, I actually didn’t walk in that so I can’t for sure but driving on it, it was pretty stable. More like driving on hard packed dirt than loose sand.
Dropping knowledge bombs. Saltmen, who woulda thought lol