When race cars get "really light" what starts going wrong.

how much is a bug engine?

last I checked the Subaru prices were ej20 twin turbo - $600 Microsquirt - 300 adapter/flywheel from kennedy - 300

so for 1200 bucks you get 200+ hp

what does 1200 bucks get you in a vw?

icaneat50eggs wrote: what does 1200 bucks get you in a vw?

58hp

edizzle89 wrote: Reading what you are looking to do makes me think you are wanting something similar to The Lot Lizard but with mid-engine.

I was truly, deeply, existentially disappointed that Jim never made it over to one of our BMC autocrosses with the Lot Lizard.

How heavy is an ACVW engine/transaxle?

I did some figuring a while back, I remember that a VW watercooled inline four weighs less than a Mazda rotary (so good swap into RX-7) and I wanted to do an aircooled Fox until I found that the ACVW engine is actually about the same weight as the iron/aluminum watercooled!

So I guess, what might work good, would be to use a watercooled VW (220lb?) and 020 transmission, which is practically one-handable. Not very strong but if the car is light, you don't need a strong trans.

Yes you need a radiator, but how heavy is a radiator? Grab a half-width Civic radiator and fan, ought to be plenty. Stuff it in the nose with a little cowling so the airflow doesn't recirculate back in front of the radiator when sitting still.

chaparral wrote: Nobody ever asked for a heavier airplane. The lighter the car, the less wing you need for the same cornering speed increase. If you can pull 5g in all of the corners, the only thing the engine needs to do is overcome the drag.

Ever heard of Howard Hughes?

From what some FSAE guys told me, the real partical issue you encounter with a really light car is getting heat in the tires or getting a tire with a compound that's soft enough.

Just in regards to handling, the business about 7s being prone to oversteer is bunk - with the exceptions of if the geometry is terrible, or if you've got a live rear axle on a bumpy road. The sevenesques that I've driven extensively were "heromakers" which is to say that they are so forgiving, you can get away with driving errors which would get you into big trouble on 98 percent of other cars.

Rear-engined cars OTOH are another story. But everyone here already knows that.

Knurled wrote: How heavy is an ACVW engine/transaxle? I did some figuring a while back, I remember that a VW watercooled inline four weighs less than a Mazda rotary (so good swap into RX-7) and I wanted to do an aircooled Fox until I found that the ACVW engine is actually about the same weight as the iron/aluminum watercooled! So I guess, what might work good, would be to use a watercooled VW (220lb?) and 020 transmission, which is practically one-handable. Not very strong but if the car is light, you don't need a strong trans. Yes you need a radiator, but how heavy is a radiator? Grab a half-width Civic radiator and fan, ought to be plenty. Stuff it in the nose with a little cowling so the airflow doesn't recirculate back in front of the radiator when sitting still.

Assuming a nearly stock cooling system, you're looking at upwards of 18lbs of coolant and 8 lbs of radiator, plus coolant hoses, fan, etc which could be nearly 10lbs? So 36-40lbs of weight added to make a water cooled engine happy. How much does a ACVW and transaxle weigh? Or what's the dry weight difference?

Weight with the subaru non turbo motor and accessories is about 100lb's more then the VW transaxle combo according to a friend who builds sand rails. Can you do it lighter, yes, but not on a budget.

Then it gets down to the weight of the build that I want to target and the complexity. VW I can build a motor in a weekend minus machining and maintain it for next to nothing. Fuel injection on a car that is that light and would be able to turn as hard as I want it might necessitate fuel injection on those critrea alone.

Been doing some solidworks work at home to see what I car really do and then do some real world measurements in foot lengths of tubes. Talking with a guy locally that builds mid engine sand rails as well to see if he has a frame that can accept a VW vin and still be mid engine.

fanfoy wrote: From what some FSAE guys told me, the real partical issue you encounter with a really light car is getting heat in the tires or getting a tire with a compound that's soft enough.

Paging Unevolved to the white courtesy phone...

OK been talking with local engineering friends and the short answer we have all come to is to buy a Exocet and build it. Or find a NA miata and strip the living E36 M3 out of it. Non of those sound like a lot of fun.

Waiting on some quotes on the sand rail chassis but I have been hearing 3K assembled but licensing is going to be a pain in California.

I do have a friend who has a different opinion which is to take a Manx and strip that out and build the cage into the suspension and engine placement would be the simplest due to the registration issues. This is still my opinion.

wearymicrobe wrote: OK been talking with local engineering friends and the short answer we have all come to is to buy a Exocet and build it. Or find a NA miata and strip the living E36 M3 out of it. Non of those sound like a lot of fun.

Why does the Exocet not sound like fun?

As far as licensing, you know about SB100, right? If you get one of the 500 available SB100 serial numbers for the year, it's actually a lot easier to register a homebuilt car in California than it is in many other states. It used to be you had to go stand in line at the DMV at 4AM on January 2nd to get one, but apparently they've worked through the backlog and now the SB100 slots are available much later in the year.

What about a Catfish?

Best of both worlds between an Exocet and a full Meotter.

Comparing a high-hp to low-hp car with identical power:weight will depend on speed.

At a low-speed track with tons of technical corners and short straights, the lighter car will be faster in theory.

At a high-speed track, aerodynamic drag will be a bigger factor. A car with more hp will be able to overcome the drag better and generally have higher top speed (assuming gearing and everything is correct).

So, the answer is: it depends

In reply to LanEvo:

I'm not sure what this adds to the mix, but 10-15 years ago some other magazine did a Viper vs Lotus comparison to test this concept and the viper was faster on both high speed and tight tracks.

I've only driven a Viper once (at Mosport) but I wouldn't be surprised if it had more mechanical grip and better braking than the Lotus at any speed.

I should have said "all else being equal." I was thinking in terms of E36 318is at minimum weight vs. E36 M3 with ballast to match that power:weight ratio (and assuming identical suspension, tires, etc.) In that case, I'd expect the lightweight car to do better at low-speed tracks and the horsepower car to do better at high-speed tracks.

In the real world (like NASA GTS) it seems going for more power is always the answer.

wearymicrobe wrote: OK been talking with local engineering friends and the short answer we have all come to is to buy a Exocet and build it. Or find a NA miata and strip the living E36 M3 out of it. Non of those sound like a lot of fun.

You can buy a turn-key Exocet.

FWIW, the building process on my Stalker V6 kit car was one of the most enjoyable and educational things that I've ever done. I'd love to build an Exocet. Now as far as budget goes, sure you can spend $20K building an Exocet, and it will be fantastic, but the last $7K are diminishing returns. A box-stock Exocet will be very fast and outrageous fun. A $20K version will be a little safer, and faster. But More, more, MORE! is a boring game after a certain point, and the winners are usually the rich guys, so f--k them, build an affordable car and have at it.

Speaking of which, there's absolutely nothing wrong with screwing around with a 65 HP aircooled buggy. At 1000 lbs. it will still be quick, with a power/weight ratio similar to the "hot hatch" category of modern cars. And you could do it very inexpensively - especially if you convert someone's sand buggy to street use. It's not about miles per hour, it's about smiles per hour.

Kreb wrote: It's not about miles per hour, it's about smiles per hour.

So this is the key, I already have a even by internet standards a bat E36 M3 insane track car.

So I am off to craiglist to look at miata's and Manx's. There is a good contender in Poway but at 7K he would have to come down about 2K to make it a viable option IMO

Are there any legal concerns making a VW pan based car mid engined with the VIN location being right where the engine would ?

So many years ago one local autocrosser showed up with a Meyers Manx clone and did pretty well with it. After a while it was lowered and the 1600 dual port motor got some larger barrels (1680 I think) plus some decent dampers and sway bars. At that point it started to challenge for top time.

Eventually it was sold to another member who turned it into a mid-engine missile that was no longer a budget car.The VW suspension is not state of the art, well not since 1930 but you can still get them to work surprisingly well.

For goodness sakes my autocross car (F500) uses bump stops for dampers, it's 750lbs with driver.

What is the weight minimum for shifter cart 300lbs give or take?

Ages ago I saw an article on a British hill climb single seater; carbon fiber tub with motorcycle engine as semi stressed member, I think it weigh some crazy thing like 360lbs. It didn't have any issue with getting heat in the tires, just a case of getting the tire size and compound right.

If I were trying to get something super light and street registered a dune buggy would be one possible choice. They are 1200lbs or so and can be made lighter.

There are a whole host of British sports cars that can be paired down to nothing. Take an old Sprite, installing one of the many one piece front ends takes something like 100lbs out of them. Motor swap to Datsun A series and tranny will shed another 75lbs.

The biggest issue with making cars super light is turning them into a flexible flier. Sometime that extra 100lbs makes the car faster.

In reply to icaneat50eggs:

I know markets tend to vary around the country, but my local Craigslist has one EJ20, 3.5 hours away, asking $900. Looking at sold listings on eBay indicates most engines are going for between $750-1200, tack on another $200-500 for engine plus trans.

What do you get for the same money with an a/c VW? Apparently about 100 pounds weight savings right off the bat, plus the ability to save a E36 M3load more weight by avoiding the knock-on effect of heavier components everywhere else on the vehicle to deal with the added weight and power.

I ordered my ej20 from tiger Jdm for 450 a few years ago. The twin turbos can't be dropped into any American subies so they go cheap

In reply to icaneat50eggs:

Ah, that makes some sense, my searches might not have highlighted the cheap JDM ones.

In reply to Tom1200:

Or a Spitfire - which being a body-on-frame car would have potential for fitting a minimalist body. Of course, those are what the original LoCosts were for the most part.

From what I've read over the years, one of the biggest challenges with tuning a lightweight car is resisting the urge to over-tire it for the weight and power.