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Learning how to build Lotus Seven replicas...together!
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PostPosted: Wed Apr 11, 2012 5:59 am 
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Shortexistence wrote:
I've always been intrigued by rotary engines. High revving, super simple, very few moving parts.


Fallacy, Rotary's do not like to rev at all, try a 13B at 9000rpm and see how many hours it lasts whereas for example, a Honda 'K' series will do 9000rpm all day long with a 3 year factory warranty.

Rotary's have a single fire per RPM and sound like they are revving higher, they are not.


Shortexistence wrote:
something rotaries are not known for, torque.



Another fallacy, as HP doesn't exist and is merely a measurement of torque and rpm, a piston engine that has 250HP at 7000rpm has exactly the same amount of torque as a Rotary with 250HP at 7000rpm.



Shortexistence wrote:
My build is obviously outrageous to most of you. cheapracer obviously thinks so.


Meh, I'm just the class clown. :lol:

(But I do think you're barking up the wrong tree with this one).


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PostPosted: Wed Apr 11, 2012 9:21 am 
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As far as the use of the car the majority of it will be on the street. Drag strip, standing mile, autocross, rallies, and track days are things I want this car to be capable of as well but as far as a serious purpose built race car this will not be one. I'm thinking the high end of this car's budget will be under 15K but am willing to be flexible to make the final product what I want it to be. I'm going back to New Mexico after school but by the time this thing is done I could be anywhere, so I don't know where it's going to be registered.


I'd respectfully suggest you cool down a bit and get your feet planted before taking on such a big project. 1st, some states will not even let you build your own car. Some on this board have run into that already. It doesn't do any good to get your car completed, after putting your own money and sweat into a build, and then not be able to drive it. Other states will let you but you may not get past an imported engine (not EPA smog approved) Some states will make you pass a smog test. Some states just don't care. So where you end up living will determine whether you can get it registered for the street or not. Read some of the registraion threads and get prepared for things not going your way. If it were me and I were where you are at this time, it would be a deal breaker for me. What you do with your time and $$ is totally up to you.

2nd, If you are dead set on a eventually having that turbo 20B engine then you will definitely need adjust your budget. There is currently a Cosmo front clip on eBay right now at $5900. Figure somewhere near another grand in shipping. Now you are at $7K before you start. Engine Rebuild DIY(1,500), porting farmout (5-750), aftermarket ECU (1K), and exhuast DIY (500), turbo rebuiild (250) dyno tuning (???)etc.... You are at or above $11,000 for your ideal engine which leaves 4K for the rest of the car.

You can easily meet 250 HP with the 2-rotor stock engine and reasonable levels of boost. This would lower your costs tremendously. And if you get a RX-7 or ??? as a donor, a lot of the parts can be reused. Building a car for 650 HP capability and only using a 250HP engine is also expensive. Trans/diff/ brakes are all factors for the HP difference, and building for HP costs $$$$ Think about whether you'd rather be driving a car you built that will knock the doors off of any US production car vs looking at a partially completed car taking up space in your garage.

FYI, here is a site with a bunch of various dyno runs for rotaries. http://www.catenet.net/dyno.php

For what it is worth, I'm in cheapracer's camp. Your goals appear to be too agressive for a beginning builder.

But we will help you in any way we can regardless of what we think.

Cheers,

Chuck

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“Any suspension will work if you don’t let it.” - Colin Chapman

Check out my rotary build log: click here


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PostPosted: Wed Apr 11, 2012 9:54 am 
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Always Moore!
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You could always get the car built with a 2 rotor engine and swap for a 3 rotor later if you are not happy. It would be a nice way to kill a winter and would eliminate a huge roadblock.

Not to discourage you but I cannot think of a single build that has been completed where the builder choose to start with a crazy engine or a huge rebuild. Those builds are typically the ones that end up for sale a few times then grow roots in the back of someone's garage or get parted out.

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PostPosted: Wed Apr 11, 2012 11:28 am 
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The build itself doesn't sound outrageous, it's just that you are applying big car numbers and needs to a car that doesn't need them. It's great that you've thought it through.

You would HATE 600 hp. You wouldn't be able to enjoy the car. 300 hp in this light a car will feel like 600 hp in a BIG car like an RX7. That's right I called the RX7 big because it is by comparison.

You can always tell the people who've never really driven a 7 by their wish list. That's the cool thing about a 7, you don't need all that expensive, high maintenance, high cost, easily broken stuff to have oodles of fun in a 7.

Until you've experienced light weight you can't understand what it brings to the equation. Look at the Miata (another porker by 7 standards) basically the only thing it's ever had going for it was it's weight. It doesn't have a sophisticated, high HP engine or even a sophisticated suspension. All it's had is that it's weighed less than most cars.

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PostPosted: Wed Apr 11, 2012 2:08 pm 
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rx7locost wrote:
But we will help you in any way we can regardless of what we think.


Indeed, I'm a smart ass but always happy to give some time up and you're in a good forum with many decent people :cheers:


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PostPosted: Thu Apr 12, 2012 11:24 am 
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carguy123 wrote:
I would say try the car without the turbo first to get it sorted.

The trip rotor will really surprise you especially when coupled to this low of a weight vehicle.

Also that way you are not working on all the problems at once. Get the chassis sorted and then throw more horsepower than God needs at it.



I would stay away from the turbo to start as well. There are other issues to consider. You'll need heat treated stationary gears with a lot of HP since the stock gears collapse at high reves.

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PostPosted: Thu Apr 12, 2012 1:16 pm 
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A high HP rotary would need a huge cooling system. One not likely to fit inside a Locost nosecone. They generate a LOT of heat.

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PostPosted: Thu Apr 12, 2012 1:25 pm 
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The Miata has very sophisticated suspension for any car in its class. Full unequal length A-arms on each end. Don't get that on a Porsche ( Other than a Carrera GT). Other than alloy suspension arms and a rear transaxle,there is very little to be left wanting. Regardless, it's no slouch stock. Not perfect, but MUCH better than any other small car.

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Volvo 240/P1800 Based Locost
2004 Aprilia Mille Factory
1988 Volvo 240 5 Speed ( For Sale)
2002 Toyota Tacoma
1999 BMW M3


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PostPosted: Thu Apr 12, 2012 1:29 pm 
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Location: Raleigh-Durham NC
rx7locost wrote:

I'd respectfully suggest you cool down a bit and get your feet planted before taking on such a big project. (snip) Cheers, Chuck


I was starting my build -- had an engine, parts, new welder, etc -- before wife got sick. Then the economy tanked, and I was forced to work "out of town" for a few years. Now wife is ex wife, etc etc. I'm back to square 1.1 (still have the new welder, albeit never fired up). This hobby depends on you having a stable home and work life to pull it off, or so it would seem to me.

The second thought I have is that many have started out fretting over the tensile strength of each rivet, looking for the unobtainium motor parts, deciding to MegaSquirt (when they've never done that before), obsessing over the relative rigidity of 16 ga versus 18 ga, etc etc etc etc. The end result is that, if they ever do get the thing built, it will be 4-5-6 years down the road.

(this is where I tie those 2 thoughts together)

The problem with taking 4-5-6-100 years to build this, aside from the fact that you can't drive it during that time, is that the longer you take the more likely that family, work, finances, etc will put a stop to things. And it increases the likelihood that you'll get bored.

My new idea here is to set a limit on the build time -- I will spend no more than 2 years, from first tube cut (or purchase of donor) until I'm driving it. After I'm driving it, then I will feel free to change motors, or turbo it, or whatever.


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PostPosted: Thu Apr 12, 2012 1:35 pm 
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+1

It's a common theme here, and an excellent idea, to do whatever it takes to get the car running, then make improvements. Improvements are fun and easy. OTOH motivation can be very hard to come by if you think your Locost has to be perfect right out of the box.


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PostPosted: Thu Apr 12, 2012 6:25 pm 
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in two years i got to the point of complete car minus front brake hoses, paint job and computer key coding,
then i ran out of money big time, about a week short of completion.

no work, no jobs on the side, nothing.

so yes set a realistic completion date by all means but [PooPoo] happens.

i have been three months trying to earn enough to make it run, got the brake hoses today, but i am sick of looking at the car, i would go as far as to say i hate it but still find it interesting as an engineering exercise, and it does beat watching day time t.v.

i have spent the day looking at the transition of the flexi lines and the solid lines, i know what i need to make, just a plate with the hole in it to take the end of the flexi and clip, but i can't make myself do it.

when i ran out of funds, i sort of blocked the car out, now i can't get back to it, i've lost the flow somewhere in the credit card debt.

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in the depths of the grand canyon, one lone builder with no budget and few skills is going for it!!!


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