Over Running Clutch For Extra Mpg

[DAVID BROWER]

WHAT YOU DESCRIBE IS CALLED A FREEWHEEL DEVICE .

A NUMBER OF TWO STRIKE CARS HAD THEM BACK IN THE DAY . MOST NOTIBLY SAAB .
WHEN YOU DESCEND A HILL IN A TWO STROKE , THE REVS STAY HIGH
BUT THE FUEL CONSUMPTION IS LOW .

SINCE THE 2 STROKERs MIX LUBRICATION WITH THE FUEL ,
THE MOTOR CAN SEIZE GOING DOWNHILL IN GEAR !

THE FREEWHEEL DEVICE ALLOWS THE CAR TO COAST WHEN THE ROAD SPEED
EXCEEDS ENGINE SPEED EVEN WHILE IT IS IN GEAR .

YES , YOU LOSE ENGINE BRAKING SO THEY GAVE YOU BIGGER BRAKES TO MAKE UP FOR IT .

MY MESSERSCHMITT DOES NOT HAVE A FREEWHEEL DEVICE BUT THEY DID PROVIDE
A NEUTRAL SELECTOR THAT WORKS IN BETWEEN ANY TWO GEARS .
NOT QUITE A SOPHISTICATED BUT IT GETS THE JOB DONE .

I WOULD LOVE A FREEWHEEL DEVICE ON MY ELIO !
IT WILL HAVE MODERN DISC BRAKES MORE THAN ADEQUATE TO MAKE UP THE DIFFERENCE .

 

['lio]

A modified clutch is not a contemporary approach to this, a start stop system with coasting mode should be more efficient and easier (cheaper) to implement, see: Bosch Introduces Start-Stop System With Coasting Mode

 

[skygazer6033]

An over running clutch is really not a good idea. Modern fuel injection systems cut fuel flow in negative torque situations (coasting) to practically nothing. You really have little to gain. Of course what you loose is engine braking. Also there is a legal consideration. In many states (including Texas) it is illegal to drive with the clutch disengaged or transmission in neutral. You are considered to be out of control.

 

[wheaters]

An over running clutch is really not a good idea. Modern fuel injection systems cut fuel flow in negative torque situations (coasting) to practically nothing. You really have little to gain. Of course what you loose is engine braking. Also there is a legal consideration. In many states (including Texas) it is illegal to drive with the clutch disengaged or transmission in neutral. You are considered to be out of control.

I understand that is the same in UK, although it might be an urban myth. My late father in law had a Saab van with a freewheel transmission as a company car (very rare vehicle over here, never seen another like it). He told me he hated it because he never felt secure with it. It was possible to disable the freewheel and that is how he preferred it, especially as he didn't pay for the fuel.

 

[skygazer6033]

No myth wheaters. In my online research I actually stubled upon UK regs before I found USA state regs.

 

[Dexter Henschel]

My first post. I've been following this car since I saw an article about it in a newspaper last year and Im pretty intrigued by the concept. Paul, my hat is off to you. I've built a few thing and while they usually function, they ain't pretty, seem like they take way longer to make than expected, and cost way more than I thought. I wish you the best of luck.
I'm a big fan of manual transmissions. Although they are relatively efficient at putting the power to the ground, the engine is often spinning faster than it needs to when going down a hill, coming up to a stop sign ect.. Kinda like those fixed gear bikes that the peddles always move on, you don't get a rest going down hill, it's just a lil easier than going uphill. I can usually pick up a couple mpg by shifting into neutral a while before approaching a stop sign or while going down a hill and just using my brakes. Has there been any consideration into adding an over running clutch similar to what peddle bikes have that would allow you to coast and then peddle when you want? I think this would help the elio easily hit the 84 mpg goal but I realize it would probably add a fair cost.. A lot of automatic transmissions will disengage at 28-35 mph, what if that limit was taken so that any time you had your foot off the gas the transmission would disengage? I think that's one reason the mid 90s Buick park avenues got such excellent mileage for how big they were is the transmission would just let the car coast when power wasn't required. My brother could pretty easily get 30-32 on the highway with his. Possibly electricity controlled hubs on the wheels would work similar to a lawn mower deck clutch to allow the computer to easily engage / disengage when needed.. What's your thoughts?

I am in favor of an over-running clutch if you can disable it with a switch. I like having engine braking available in stop and go driving, and it saves a lot on the brakes. The big truck tractors use engine braking, but they are a bit noisy in urban areas. The gas engine would keep things relatively quiet.

 

[charchri4]

I am in favor of an over-running clutch if you can disable it with a switch. I like having engine braking available in stop and go driving, and it saves a lot on the brakes. The big truck tractors use engine braking, but they are a bit noisy in urban areas. The gas engine would keep things relatively quiet.

Say what??? Brake pads are 30 bucks a set and you would rather put the wear in your engine?

 

[TCBronson]

I'd rather change brake pads than a clutch any day.

 

[slinches]

If you're downshifting correctly, it shouldn't significantly affect clutch life. And engine braking is necessary in mountainous terrain as brake fade can be a serious issue even in a passenger car. If they want to implement a free-wheel system into the AMT (e.g. electronically disengage the clutch under reverse torque), then fine, but don't touch the standard transmission.

 

[BilgeRat]

Skygazer is right. I can see the cutoff on my Honda Fit on the ScanGauge, and even adjust the cutoff point via the ScanGauge. Can't see the need for a freewheeling system.