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Learning how to build Lotus Seven replicas...together!
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PostPosted: Wed Jan 04, 2006 8:15 am 
I have considered several power trains for my Locost project and I have not yet made up my mind. The selection process seems to be a mix of logical and emotional arguments with oneself and in the process of arguing with me and others I have looked at the VW Beetle (air cooled), a Ford 260, 289 or 302 V8 and now I am investigating the flat 6 Corvair. And I like what I read!

What I like about the Corvair is this:
1- flat six= lower center of gravity for the locost
2-Air cooled engine is lighter. 300lbs for a six cylinder ain't bad
3-can produce 140 HP @4400rpm stock, 150HP @ 5000rpm (stock), 150 to 200HP with a turbo (still stock). In performance aftermarket ...the sky is the limit
4-the "sky" is actually the main positive argument for these engines. As a former commercial pilot myself I like the predictability of a big bore air cooled mill. The Corvair engine has a large audience among general aviation pilots and this drives its market today.
5-The engine (and the GM cars) still enjoy an extensive and well organized fan network in the World and in particular in North America...so the Corvair engine may not be as exotic for us as it may look.

What some of you may have against the Corvair engine:

1-the width of the Locost may have to be enlarged considerably to be able to lodge this engine in the little car ( lateral access to the heads for maintenance will make this point even more problematic)

2- Because the Corvair is a rear driving powerplant, the engine will have to be mated to a non stock transmission. This can be done . One can even get the Corvair to fire in the opposite direction if needed.


Now..Your turn.......


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PostPosted: Wed Jan 04, 2006 8:44 am 
you could always use to corvair engine in a middy design.


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PostPosted: Wed Jan 04, 2006 2:08 pm 
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Joined: Mon Aug 15, 2005 10:13 pm
Posts: 7048
Location: Charleston, WV
Sounds to me like you would be going to great pains just to be different and to use an engine you like. IMHO what you will have in the end won't necessarily be much if any better cost or performancewise than a more traditional inline four, just different. A well tuned, four cylinder can achieve those power figures pretty easily and wont be much heavier.

You say Corvair engine makes 150HP and weighs 300 lbs. The 2.0L DOHC lump in my Neon makes 150HP and weighs about the same. Sure the cooling system will add weight, but so will widening the car to make the Corvair engine fit. Just my $.02.


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PostPosted: Wed Jan 04, 2006 4:03 pm 
Great engine - original choice as well for a locost. Power to weight is better than most choices as well if you go for turbo.

I have been thinking of a flat four engine (alfa 33 1.7i) to fit either in the front (with clutch housing on engine and torque tube to transaxle mounted at the back) or mid mounted straight onto transaxle!

Don't be put off by cooling though - Tatra in czechoslovakia used the power of the exhaust gas flow to draw air over the engine for cooling when their cars were stationary (on the move there was no problem).

BTW, a former chief engineer of Tatra wrote a very interesting book about Tatra's experiences with air cooled engines they designed - I think his surname was Mackerle. It may be of use/interest to you.


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PostPosted: Wed Jan 04, 2006 6:01 pm 
chetcpo wrote:
Sounds to me like you would be going to great pains just to be different and to use an engine you like. IMHO what you will have in the end won't necessarily be much if any better cost or performancewise than a more traditional inline four, just different. A well tuned, four cylinder can achieve those power figures pretty easily and wont be much heavier.

You say Corvair engine makes 150HP and weighs 300 lbs. The 2.0L DOHC lump in my Neon makes 150HP and weighs about the same. Sure the cooling system will add weight, but so will widening the car to make the Corvair engine fit. Just my $.02.


R-Thanks for the reply.
Everyone likes to be different. This applies to me too, I agree. I like the music of a six or an eight, it is how I feel about exotic cars. But you forget the main point: the two engines Corvair and Neon that you are comparing will not produce 150HP the same way. I doubt that the neon can crank out 150HP at 5500rpm, the Corvair does...it has to do with the the Law of the displacement. The Corvair probably displaces twice the volume of the Neon...therefore I would have to build a larger fuel tank and indeed I would be as heavy or more than you. But does it matter. The goal is to have fun, no matter how you define fun. Take care.
Philippe.


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PostPosted: Wed Jan 04, 2006 6:09 pm 
archie_uk wrote:
Great engine - original choice as well for a locost. Power to weight is better than most choices as well if you go for turbo.

I have been thinking of a flat four engine (alfa 33 1.7i) to fit either in the front (with clutch housing on engine and torque tube to transaxle mounted at the back) or mid mounted straight onto transaxle!

Don't be put off by cooling though - Tatra in czechoslovakia used the power of the exhaust gas flow to draw air over the engine for cooling when their cars were stationary (on the move there was no problem).

BTW, a former chief engineer of Tatra wrote a very interesting book about Tatra's experiences with air cooled engines they designed - I think his surname was Mackerle. It may be of use/interest to you.


R-Thanks Archie for your points. I have explored the possibilities of several engines so far and I should say that the GM Corvair scores high. My plan is to keep reading about it and if I find nothing wrong with the idea (or if no one punches a big hole in my dream) I will take the plunge and find one. Take care.
Philippe.


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PostPosted: Wed Jan 04, 2006 6:12 pm 
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Joined: Mon Aug 15, 2005 10:13 pm
Posts: 7048
Location: Charleston, WV
You are right, the Neon needs 6500 RPM to make 150HP and I applaud you for taking the path less traveled. :D


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PostPosted: Wed Jan 04, 2006 6:50 pm 
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Joined: Tue Aug 16, 2005 10:29 am
Posts: 1064
Location: Alberta, Canada
It would be an interesting build for sure. I'd be measuring what kinda of width you're looking at. If you're after the seveneque shape a front mount might look odd if too wide. A mid engine config would work with a Fiero 4cyl tranny and a later Corvair motor (these have the SBC V8 tranny bolt pattern I believe). Of course you'd need to spin the motor the usual way.


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PostPosted: Wed Jan 04, 2006 9:09 pm 
Dave wrote:
It would be an interesting build for sure. I'd be measuring what kinda of width you're looking at. If you're after the seveneque shape a front mount might look odd if too wide. A mid engine config would work with a Fiero 4cyl tranny and a later Corvair motor (these have the SBC V8 tranny bolt pattern I believe). Of course you'd need to spin the motor the usual way.


R-Hi Dave,
My goal would be to build by the "Book". I want to be able to retain the traditional Lotus 7 look. Before building the chassis I should rig up the whole power train: front engine RWD, live rear axle, wheels. I wouldl make a plywood mock up firewall and transmission tunnel to make sure that everything would fit-in. My expectation is that the 30" wide engine would live happily in the engine space of the Locost + probably 4" or 5 " in width. Because the six needs a significant cooling shroud I may have to build the hood a bit longer, maybe 6". That is all.. However. because the wheels would be bigger 15" or even 16" and the rear axles wider the car would seem larger than the common Locost.

Good luck with the Hunday project.

Philippe


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PostPosted: Sat Jan 07, 2006 2:28 pm 
Most installation problems can be overcome if anticipated early enough.

Are you planning on using flowing wings or cycle wings at the front?

Flowing wings will cover the fronts of the heads if they overhang the front lower frame outer rails. The exhausts manifolds on each side could be used to disguise this further - heat shrouding carefully placed can cover a multitude of sins!

As for the huge airflow required to cool the engine during spirited driving, use it as an air deflector instead of a windscreen. This is an adaption of what Renault used this on its awesome Spider - worked well even at low speeds. I don't know if they went to USA or Canada - here's a link if not.

http://www.fedrelandsvennen.no/amcar/jo ... pider.html


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PostPosted: Sun Jan 08, 2006 8:27 am 
[quote="archie_uk"]Most installation problems can be overcome if anticipated early enough.

Are you planning on using flowing wings or cycle wings at the front?

R-Hi Archie
The Corvair idea is still theoretical for me and I have not yet worked out all the details, just in case I would end up building a Toyota based Locost like everyone else.

Should I proceed with the Corvair idea, I would go for Cycle fenders, precisely to avoid creating deflection away from the hood. The Corvairs' forced air cooling works from the top down, therefore I would make a good size scoop on top of the hood (Like the Stalker) . Just as a note for your information: the Corvair engine in order to work as a front engine RWD needs to have its rotation reversed, which means a new cam, and perhaps other things too. It needs another GM transmission, shaft and rear axle..
I still very much like the idea but I am trying to keep an open mind on the subject. The $$ dimension matters to me. It looks that the Corvair would have to be rebuilt from the ground up...Someone who has worked with Corvairs has advised me to look into the Buick (Rover)aluminium V8 instead. Same weight, same era, twice the power, probably lesser cost to get running...I take good note of what I read on these forums and when the time will come to make a decision it will be an educated one (hopefully).
Philippe.


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PostPosted: Sun Jan 08, 2006 9:32 am 
I understand the importance of selecting an appropriate engine from the start - I began my plans with a rover v8 (formerly a buick engine as you stated).

You mention that you would need to reverse the engine's rotation necessitating a new cam amongst other things - I don't know how it is driven in the corsair but the oil pump might then pump the wrong way so the oil flow would be reversed!

Simplify things as much as possible - if you consider using a corvair engine, leave it's rotation alone - the gearbox internals will be driven in reverse so turn the diff upside down to correct the vehicle movement. Much simpler than redesigning the engine! This is how Rover put the engine in its MG 6R4 rally car facing the wrong way!


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PostPosted: Sun Jan 08, 2006 2:09 pm 
archie_uk wrote:
I understand the importance of selecting an appropriate engine from the start - I began my plans with a rover v8 (formerly a buick engine as you stated).

You mention that you would need to reverse the engine's rotation necessitating a new cam amongst other things - I don't know how it is driven in the corsair but the oil pump might then pump the wrong way so the oil flow would be reversed!

Simplify things as much as possible - if you consider using a corvair engine, leave it's rotation alone - the gearbox internals will be driven in reverse so turn the diff upside down to correct the vehicle movement. Much simpler than redesigning the engine! This is how Rover put the engine in its MG 6R4 rally car facing the wrong way!


R-On the Corvair engine I have picked the brains of a Yahoo forum called Fastvair (700+ members) who are entirely focused on modifying these engines for racing. Their common wisdom is to reverse the engine rotation (I understand that the oil pump will go along with that), change the Cam+ gear which might have to be changed anyways if you are going to rev this engine higher than stock...and all I have said about a new tranny, shaft, rear axle. It looks like a lot to be, but I have not given up, yet.

Philippe.


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PostPosted: Fri May 05, 2006 1:41 pm 
I think a flat 4 or 6 would be a great idea. You could have cylinders sticking out or the panels ducted around the cylinders for great cooling and you would have that cool morgan look with the cylinders exposed. I had discussed this with champion motorsports as the vw after market and original parts make great for a locost. The front beam could be used. dune buggy windscreens are very similar to the book design. Pluse vw flat 4s are very light. The engine profile plates for vw 4s makes for easy adapter to traditional rwd trannies.


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PostPosted: Fri May 05, 2006 2:09 pm 
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Mid-Engined Maniac

Joined: Sun Apr 23, 2006 8:26 pm
Posts: 4859
Location: SoCal
How reliable is this engine, what do replacement parts cost, how easy are these parts sourced? Long term maintenance could drive a "cheap" engine to cost a lot more. It could be hard to beat the 300hp supercharged V6 used in the Stalker, which I hear sells for $1500-$2000.

About the weight, most modern engines aren't going to be that much different, especially when power's factored in.

Like you said, the 'Vair will need a complete rebuild, which impacts cost but more importantly, takes away your focus from the real project. Are you rebuilding an engine or a car?

All the above aside, if you have your heart set on this engine, just use it, why even ask what other people think?

How about passing the cylinders out the sides of the engine compartment, that would look pretty cool(!) and may not require widening. I do however think it's silly to force the engine into the Locost book chassis. Good Heavens man, *your* the one cutting tubes and welding it up, fit the chassis to your chosen engine, not the otherway around.

_________________
Midlana book: Build this mid-engine Locost!, http://www.midlana.com/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


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