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Author: Subject: Is mid engine really better?
Ratman

posted on 4/2/10 at 11:44 PM Reply With Quote
Is mid engine really better?

I sort of feel that all other factors being equal, a "mid engine" location will work better than a front engine RWD layout. But I wonder if this has ever been proved in the real world. There are some UK manufacturers who are producing 7-type cars with engines in the front and rear. I am wondering if there are records of cars with basically identical engines and similar chassis' but with alternative configuations being run at the same day at track days or races. I guess something like this happened in the early 60's when racing cars were switching to the mid engine layout. But this might have been more significant for single seaters, considering weight and frontal area. So, how does this work out for modern 7dom?

http://www.youtube.com/watch?v=2Tw1PKEHdWo

[Edited on 4/2/10 by Ratman]

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brianthemagical

posted on 5/2/10 at 12:21 AM Reply With Quote
Just have a look at nearly every Prototype, formula and many GT cars. They'll be mid engined.
Wether or not you'll notice, or if most other Locosters will notice the difference, is another matter.

The advantage is all to do with polar moments, and the mass of the vehicle being closer to the turning axis (rear wheels).

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A1

posted on 5/2/10 at 12:31 AM Reply With Quote
its probably like a lot of things, where you only really notice when you push it.
in the snow, my dads evo was kinda slidey at slow speeds, we werent overly impressed, however one day he booted it really hard and it was really neat and planted.
probably a crap way of explaining what i mean, but it made sense to me...

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Ratman

posted on 5/2/10 at 12:44 AM Reply With Quote
A1, I think you might have a good point there. The difference is only going to show at the limit. The closer you go to the limit the more is the benefit of a mid engine layout.
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Horizenjob

posted on 5/2/10 at 02:55 AM Reply With Quote
When I watch videos of sevens and locosts on the track they seem to be limited by rear traction. It is not that hard to break the rear end loose. So it would seem more rear weight bias would be in order and I think that is a big advantage of the engine behind the driver.

You also gain under braking, when the weight transfer evens things out a bit instead of overloading the front tires.

Then there is also the availability of so many powerplants from FWD cars, which can simply be moved behind the driver. Here in the states we really don't have so many RWD parts that are suitable...

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kb58

posted on 5/2/10 at 05:45 AM Reply With Quote
Hah, a very similar thread's on the LocostUSA forum... where I got flamed about being too positive about my yet-to-be completed middie, called Midlana. It went something like, "We've never seen a privately-built home-made middie that was any faster than a Locost, so pipe down." The funny thing is that this was in their own mid-engine sub-forum, but whatever. Crafty way to win an argument though, ensuring virtually no cars like this exist before saying they're uncompetitive, but I'm over that, lol.

Anyhow, here's what I write in the FAQ in my own forum:

quote:

"Is Midlana better than a Locost?"

Depends what "better" means - some people think it only means "faster." Since the primary difference between a Locost and Midlana is engine position, the only way to know would be faster is to run the following test: Two cars, equal weight, equal wheelbase, equal track, equal tires, equal aerodynamics, same exact engine, one mounted front-engine, the other mid-engine. Same driver, same track, same day. Drive 10 laps in each and see what's what - that's it.

Anything else is meaningless because so many factors throw the results off. Realistically, the chances of this test ever happening are slim to none. Of course, the fact that mid-engine cars have won every single F1 race since 1958 should be a strong indicator of what works best on-track. Given the choice, why not start with a superior design right from the start? Phil Hill once said, "It was really astounding how just the placement of the engine [behind the driver] gave comfort to the drivers. The whole feeling of being - at the end of the string - was gone."

So yes, I do feel Midlana is better; not because it may or may not be faster, but because of all the secondary benefits placing the engine behind the seats has - foremost being a much wider choice of engines and the resulting low PMOI.



If you guys are open to mid-engine layouts, check out mine at http://www.midlana.com/

[Edit] Oh, and you're right, the low PMOI of a mid-engine layout makes a huge difference on turn-in. My buddy Max (a Brit I might add got a ride on-track in my previous car, a mid-engine Mini, and said he couldn't believe how quickly the car would change directions.

I'm going to mop the floor with any Locost I meet on-track, not that I have a point to prove or that I hold a childish grudge... Of course, when I do beat them, they'll have some excuse unrelated to engine position

[Edited on 2/5/10 by kb58]





Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book - http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html

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kb58

posted on 5/2/10 at 05:52 AM Reply With Quote
quote:
Originally posted by Horizenjob
When I watch videos of sevens and locosts on the track they seem to be limited by rear traction. It is not that hard to break the rear end loose. So it would seem more rear weight bias would be in order and I think that is a big advantage of the engine behind the driver.

You also gain under braking, when the weight transfer evens things out a bit instead of overloading the front tires.

Then there is also the availability of so many powerplants from FWD cars, which can simply be moved behind the driver. Here in the states we really don't have so many RWD parts that are suitable...

You sir, are 100% absolutely correct on all counts.

A 50/50 weight distribution is great for winning a constant-speed skid-pad competition, which are pretty infrequent!

Another myth about 50/50 distribution being the end-all-be-all is when Locosters install larger rear tires to help the aforementioned rear traction issue. The resulting car may still have 50/50 static weight distribution, but dynamically the dissimilar tires are now loaded differently, resulting in understeer.

[Edited on 2/5/10 by kb58]





Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book - http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html

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Ivan

posted on 5/2/10 at 07:23 AM Reply With Quote
I feel that a properly designed and set up mid engined car will beat a properly designed and set up front engined car of the same weight and power every time.

Of course that doesn't mean that the one will be more fun to drive than the other so unless you are a good enough driver to appreciate and exploit the difference on track don't rush out to change your front engined car for a mid engined one.

Also, I think, for us average drivers a front engined car might generally be easier to pull back from the brink when you have made a mistake and let things get out of hand as a mid engined car tends to give less warning of it's imminent desire to swap ends and needs quicker reactions and better skills to catch once it starts.

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iank

posted on 5/2/10 at 07:50 AM Reply With Quote
Some additional points for/against middy's

A middy has the potential to be, maybe, 10kg lighter due to the lack of a prop shaft and less metal required in the bell housing and diff. That can be a big difference (percentage wise) in a light car.

As Ivan indicates the handling of most middys in corners tend to be "grip grip grip spin", rather than "grip, slip, squeal, spin". That bit of extra warning can certainly make the difference in the confidence level of the driver until you get to the top level of drivers.





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Never argue with an idiot. They drag you down to their level, then beat you with experience.
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smart51

posted on 5/2/10 at 08:07 AM Reply With Quote
Mid engined cars have more of their weight concentrated at the centre of the car, front engined cars have more weight towards the ends. This is called polar moment of inertia. Smaller moments of polar inertia are easier to turn (and easier to stop turning). Driven below the limit, a well balanced mid engined car will turn in faster and turn out faster than a front engined car. Above the limit, they spin faster than a front engined car.

Many mid engined cars have the engine right by the rear axle and transversely mounted. F1 cars and the like have the engine nearer the centre of the car with a gearbox separating it from the rear axle. The F1 type layout gives better weight disribution and lowest polar moment. MGFs and Elieses have weight distributions more like rear engined cars which are the most prone to swapping ends when you get it wrong.






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Richard Quinn

posted on 5/2/10 at 08:31 AM Reply With Quote
quote:
Originally posted by kb58
Hah, a very similar thread's on the LocostUSA forum... where I got flamed about being too positive about my yet-to-be completed middie, called Midlana. It went something like, "We've never seen a privately-built home-made middie that was any faster than a Locost, so pipe down." The funny thing is that this was in their own mid-engine sub-forum, but whatever. Crafty way to wind an argument though, ensuring virtually no cars like this exist, at least in the U.S., but I'm over that, lol.

Anyhow, here's what I write in the FAQ in my own forum:

quote:

"Is Midlana better than a Locost?"

Depends what "better" means - some people think it only means "faster." Since the primary difference between a Locost and Midlana is engine position, the only way to know would be faster is to run the following test: Two cars, equal weight, equal wheelbase, equal track, equal tires, equal aerodynamics, same exact engine, one mounted front-engine, the other mid-engine. Same driver, same track, same day. Drive 10 laps in each and see what's what - that's it.

Anything else is meaningless because so many factors throw the results off. Realistically, the chances of this test ever happening are slim to none. Of course, the fact that mid-engine cars have won every single F1 race since 1958 should be a strong indicator of what works best on-track. Given the choice, why not start with a superior design right from the start? Phil Hill once said, "It was really astounding how just the placement of the engine [behind the driver] gave comfort to the drivers. The whole feeling of being - at the end of the string - was gone."

So yes, I do feel Midlana is better; not because it may or may not be faster, but because of all the secondary benefits placing the engine behind the seats has - foremost being a much wider choice of engines and the resulting low PMOI.



If you guys are open to mid-engine layouts, check out mine at http://www.midlana.com/

[Edit] Oh, and you're right, the low PMOI of a mid-engine layout makes a huge difference on turn-in. My buddy Max (a Brit I might add got a ride on-track in my previous car, a mid-engine Mini, and said he couldn't believe how quickly the car would change directions.

I'm going to mop the floor with any Locost I meet on-track, not that I have a point to prove or anything. Of course, when I do beat them, they'll have some other excuse

[Edited on 2/5/10 by kb58]
This is something that I have experienced on US forums for other sports/hobbies etc in the past. You appear to be in the minority and, while this may be a huge generalisation, we used to refer to one particular forum as "The Flat Earth Society" due to the reluctance to accept something different to the norm. There does seem to be a general blanking out of what does not fit with their paradigm. Any advances are taken as an insult to the current situation.
This does not tend to happen as much in the UK as we tend to adopt the stance of "ok, show us!"

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Rosco

posted on 5/2/10 at 09:02 AM Reply With Quote
I think it all depends on what kind of engine you're running.

The two biggest lumps of weight in a car, are the driver and the engine. So if you assume the driver weighs 80kgs to 90kgs and the engine weighs much more than this (e.g. American V8, Pinto, Essex), then mid may be better. If you're running a BEC or other light engine where the engine weighs much less than the driver it probaby doesn't make much difference - or front may even be better.

This ignores any packaging benfits you mights get from a mid engined layout to get both driver and engine closer to the centre of the car - and mimimixe the polar moment of inertia.

My understanding of polar monement of inertia, and I've forgotten the maths, is that it's a measure of the force required to get something to change direction. So from a driving perspective it's all about turn-in, not about the speed you can carry through a corner, which is more about grip, centre of gravity and balance.

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smart51

posted on 5/2/10 at 09:35 AM Reply With Quote
quote:
Originally posted by Richard Quinn
This is something that I have experienced on US forums for other sports/hobbies etc in the past. You appear to be in the minority and, while this may be a huge generalisation, we used to refer to one particular forum as "The Flat Earth Society" due to the reluctance to accept something different to the norm. There does seem to be a general blanking out of what does not fit with their paradigm. Any advances are taken as an insult to the current situation.


This is something I've noticed about the US. They shout about freedom of speech but if you dare use it to say something that is not the majority view, all you hear are doors being locked and shot guns being loaded. Even in minority groups who you might think would accept those who's view differs from the mainstream do the same but with their own predefined paradigm. You have to conform or leave.

A good example of this I read on the BBC website a couple of days ago. They were trying to explain the difference between liberal and conservative opinion in the US (Those words mean different things there than here). He said that Liberals want to modernise and improve the US. They use facts and numbers and well reasoned arguements to put their case across assuming that if they're right then they'll win. The conservatives then reply saying "ner ner ner ner" in a south park voice and are deemed to have won the arguement. Americans don't like change or difference. You make a car that is different and you are wrong, even if you are right.






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FFTS

posted on 5/2/10 at 10:26 AM Reply With Quote
Power to the SHEEPLE

ba ba baaaah





Chris.

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wilkingj

posted on 5/2/10 at 10:33 AM Reply With Quote
Why do I need a Mid Engined Car when my weight distribution is 45/55% in my Viento.
Thats as near as perfect as I am likely to get.
Also it changes when that Bat F'Stard of a driver gets in it

45/55 is pretty damn good for the road.
OK on the track when you are competing against others and that 5% swing could make the difference between winning and loosing.
But How Many of you on here are out and out competitive racers where it might make that crucial difference.

Still its Fun to Debate the pro's and cons of a Middy.

I like Both styles.... as the old adage states... If it LOOKS right it usually IS.






1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.

Best Regards
Geoff
http://www.v8viento.co.uk

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nitram38

posted on 5/2/10 at 11:10 AM Reply With Quote
Just ask yourself one thing, if Formula cars were faster or handled better with the engine at the front, then they would have them.
Nearly all modern purpose built racecars have a mid/rear engined set up.






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ashg

posted on 5/2/10 at 11:26 AM Reply With Quote
i dont know how other peoples engines are positioned but on my roadster my engine is at least 15inches behind the centre line of my front axle.

in my eyes even though the engine is at the front i would still consider the car a mid engine as the driver and engine are in-between the axles.

when you look at most modern fwd cars the engine is usually over or in front of the wheels.

personally i think it all comes down to application the car is intended for. if you are an out and out racer then maybe a midy layout has the advantage but its a hard call unless you have the chance to drive both.

i have seen that riots are pretty good on track but i wouldn't say they are a different league to a 7style layout.





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brianthemagical

posted on 5/2/10 at 11:32 AM Reply With Quote
Going back to the PMOI point. Where do peeps think the car turns or pivots during turn in?

It's not the centre of the car but rear axle line and that is where the PMOI are acting about, thus weight distribution isn't too important, it's more about getting the mass as close to the centre of the rear axle as possible.

This doesn't take into account the weight distrobution for steady state cornering and front rear grip though but that's where the compromise comes in.
As a side note when F1 changed back to un groved slicks last year, the FIA didn't change the widths correctly, so there was proportionally more grip on the front than previous years and the weight distrobution moved forward to compensate.

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Richard Quinn

posted on 5/2/10 at 11:54 AM Reply With Quote
quote:
Originally posted by ashg
if you are an out and out racer then maybe a midy layout has the advantage but its a hard call unless you have the chance to drive both.

Look at purpose-built race cars such as all Formula cars, LMP etc. Engine positioning is not dictated by the rules and if you consider the current F1 teams who, between them, have spent millions and millions of £'s on R&D do you not think that if there was any advantage to having the engine in front of the driver (again) they would have gone back to how it used to be?
I appreciate that it is not just about handling, it's about the whole package.

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StevieB

posted on 5/2/10 at 12:47 PM Reply With Quote
My Indy has a 40/60 weight distribution front/rear and uses the same size tyres all round.

Both myself and my mate went on a track day at a very, very wet elvington last year and found that I had a lot more grip that his Lotus 7 which is a bit more 50/50.

I was worried the rear heavy setup would be a bit of a handful, but is seems to do a good job of keeping the traction. Which is just as well, because there is very little I could change on the car to shift the weight forward any further, apart from maybe move the fuel tank to be in front of the engine instead, which may shift too much weight.

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Gakes

posted on 5/2/10 at 01:21 PM Reply With Quote
It all depends on the application or what the driver wants. This is just what I noticed

For drifting, a front weight biased car tends to be a bit more tail happy and more grip on the front. So you can enjoy sideways driving a whole lot better on windy roads

For good handling, mid rear bias cars tend to weigh down on the the rear wheels and causes more grip and more rear control. The car is less likely to slide out, so its best for good lap times around windy roads.

I think the question should've read:
For what purpose is mid engine really better?





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BenB

posted on 5/2/10 at 02:53 PM Reply With Quote
Don't forget that F1 cars have certain aerodynamic issues that road cars don't face. Sticking the engine in the front of a F1 car would create a very wide, tall front and you'ld have to put the driver above the propshaft so the car would be higher. All that drag wouldn't be good at 200mph...

On a road car you generally want to have two people side by side and you can put the prop in between.

I think there's not much to chose between them personally....

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beagley

posted on 5/2/10 at 03:16 PM Reply With Quote
Not all of us Americans are resistant to change I also like the fact that this forum tends to help the newcommers instead of insulting them as most typical Americans. Sad really..... anyway....

I'm a big fan of mid-engined cars. The pros and cons have already been hit on pretty thoroughly so I won't continue with that, but I totally agree that its the purpose of the car that determines the best layout. It's hard to make a saloon/sedan for 5 adults when theres a big lump in the middle. Wouldn't leave much room for groceries either.





I'm not scared!!! I'm just marking my territory.

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kb58

posted on 5/2/10 at 04:26 PM Reply With Quote
Well then, since my post was received in a good light, here's my list of benefits gained by going to a mid-engine layout.

- You aren’t forced to pick from a dwindling list of rear-drive engines.

- Using truck parts to build a light sports car increases unsprung weight, giving a harsh ride and a heavier car.

- Mid-engine means the exhaust doesn’t cook your feet, melt brake master cylinders, and foul the steering shaft.

- Not going deaf due to the exhaust being next to your ear.

- No big ugly mufflers on the sides of the car. (A quiet car is becoming a requirement as more and more tracks impose strict sound limits.) Good-looking - but ineffective - Cobra-type side mufflers are often too loud.

- The rear weight bias helps acceleration and braking by increasing rear traction.

- An adult-sized footwell so you don't need special shoes or having to drive barefoot.

- You and your passenger won’t burn the back of your legs on the exhaust while getting out.

- Independent rear suspension gives a smooth ride on the street and excellent camber control at the track.

- No driveshaft down the center of the car means more room for seats.

- No concern about a broken driveshaft hitting fuel lines, the gas tank, brake lines, or you. (The axle can still break of course, but are located behind the drivetrain.)

- Midlana uses the existing FWD transaxle, while Locost builders waste time trying to adapt front-engine, rear-drive transmissions.

- Many potential builders already have a favorite FWD drivetrain that they know well. Midlana allows transfering this knowledge by using the familiar drivetrain, instead of picking an unwanted engine.

- Less weight on the front tires means steering effort is lighter than with a front-engine layout.

- The steering rack is used unmodified - no cutting or welding the rack.

- Mid-engine means the front chassis area is properly triangulated, greatly increasing torsional rigidity.

- A roll-cage is an integral part of the chassis and greatly improves safety and stiffness.

- The side-vents shield the rear fenders from rock damage and autocross cones.

- Midlana uses Miata suspension, steering, gas tank parts, but no drivetrain, so no need to buy an entire donor car.

- Mid-engine means engine torque does not twist the chassis and cause odd handling when on the gas.

- The gas tank is in a much safer location than one in a Locost, where it's used as a crush-structure!

- Side vents bleed off high pressure ahead of the rear fenders, and the engine compartment exit vents help fill the low pressure area behind the engine, both helping to lower drag.

- The oil pan is protected by the chassis, protected from hitting speedbumps, and unlike the Locost arrangment where the pan is the lowest point on the car.

- With the gas tank located at the CG, handling does not change with varying fuel load.

- A portion of the area formerly consumed by the front drivetrain is used as a lockable storage space.

- Room for a real dead-pedal.

- Option for a free heater that uses hot radiator air.

- A large frontal crush structure.

This is all listed on my FAQ at Midlana forum. There's currently a "guess the horsepower" contest and win a book. That's at Book contest though you have to register to see either.

[Edited on 2/5/10 by kb58]





Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book - http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html

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Alan B

posted on 5/2/10 at 06:21 PM Reply With Quote
Yeah.....what Kurt said...
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