Multi displacement FJR

[timalan]

Just curious how possible it is to take a Fuel injected Four like the FJR and Do the Multi displacement Hemi thing like dodge did.

I don't know how dodge did it but, I just thought if you could make it seamless down to a smooth twin while on the Highway at 70ish but, back to a Four at the hint of Passing or other throttle "playing" Hmmmm 70mpg highway 35-40mpg in joy mode.

Is it possible? Flame away.

 

[twowheelnut]

I can't believe that there is not a clip of Dean Wermer on youtube...

:lol:

 

[ionbeam]

Successful variable displacement needs to be designed in, not added on. Ask Caddy how forcing it to fit worked out in the 1981 El Dorado with the 8-6-4 variable displacement engine.

I'm positive the FJR could be converted to variable displacement. Probably would cost way over $60k and still may not be bug free. Heck Ness’s twin supercharger bike worked, Leno’s turbine engine works, the 24 chainsaw engined bike works. The words practical and economical are not usually associated with this kind of work.

Round guessing at numbers: Drive 12k miles a year @ 40 mpg @ $4/gallon = $1,200. Drive 12k miles a year @ 80 mpg @ $4/gallon = $600. Take the $60k for the conversion (conservative estimate) and the $600/yr savings = 10 year payback, while riding a 680 lb/2 cyl stone = not fun. Or, keep it out of cylinder lock-out and retain some power and extend payback to 15-20 years. And this is the bright, optimistic outlook

 

[GunMD]

Round guessing at numbers: Drive 12k miles a year @ 40 mpg @ $4/gallon = $1,200. Drive 12k miles a year @ 80 mpg @ $4/gallon = $600. Take the $60k for the conversion (conservative estimate) and the $600/yr savings = 10 year payback, while riding a 680 lb/2 cyl stone = not fun. Or, keep it out of cylinder lock-out and retain some power and extend payback to 15-20 years. And this is the bright, optimistic outlook

Uhhh....let's see here....

mmmm...carry the nine....

Yep, you're wrong. It's more like 100 years for the return on that little investment.

 

[ionbeam]

Err, um, yes, move the silly decimal place over one more time. While this kind of accuracy won't prevent me from working for NASA or being a tax accountant, I'll never work for an oil company.

 

[timalan]

Err, um, yes, move the silly decimal place over one more time. While this kind of accuracy won't prevent me from working for NASA or being a tax accountant, I'll never work for an oil company.

Um yeah, I was thinking that a Motorcycle mfg. would do the research testing and Design. I just wanted and would buy one. (it must be the enviromentalist/penny pincher in me) Car Mfg, have made them and sold them. and the Hemi 300 I road in the other day worked wonderfully. I didn't acctually know it was never ending and pointless discussion it was just an Idea. My forum PAL reads my name in posts and sticks me here. Aint life grand.

 

[jestal]

Just curious how possible it is to take a Fuel injected Four like the FJR and Do the Multi displacement Hemi thing like dodge did.I don't know how dodge did it but, I just thought if you could make it seamless down to a smooth twin while on the Highway at 70ish but, back to a Four at the hint of Passing or other throttle "playing" Hmmmm 70mpg highway 35-40mpg in joy mode.

Is it possible? Flame away.

It is entirely possible given sufficient time and money. But any aort of variable displacement scheme does need to be designed into the basic engine architecture, especially with a DOHC type engine. Not something you are going to tack on later or develop a "kit" to bolt on.

Understand that the method used to make this technology work involves disabling the intake and exhaust valve operation when both valves are closed. The valves, once disabled, lock whatever charge was in the cylinder at the moment they were disabled and that ( disabled) cylinder becomes a sort of gas spring that returns whatever work is being done to compress the charge locked in the cylinder. Each time the crank turns the disabled cylinders compress the gas trapped in it and equally pushes the piston back down returning the energy. The variable displacement systems are far more complex than just turning off an injector.

Simply turning off the fuel to individual cylinders would actually add to the pumping losses in the engine and cause it to get poorer fuel economy. The system must disable the intake and exhaust valve to be variable displacement.

Despite the cheap shot at the Cadillac system ( V-8-6-4) that was in production in 1981 the method employed to deactivate the valve train actually worked quite well and the system did deliver improvements in fuel economy. It is far easier to put the hardware necessary to deactivate the valve train in a pushrod type engine which is why you see the technology resurfacing on the GM V-8s and the hemi. The older Cadillac system deactivated the valve motion at the rocker arm where the latest systems do it at the lifter rather than the rocker arm.

The real complaint with the 1981 Cadillac was not the function or reliability of the V-8-6-4 system itself but the engine smoothness when changing from 9 to 6 to 4 cylinder operation. Since that engine was a 90 degree V8 it would run rough in the V6 mode due to the uneven firing impulses of a 90 degree V6. The same is true with todays systems but the electronic control systems provide the ability to shift active displacements very smoothly by covering up the change with automatic throttle adjustment (drive by wire) and instantaneous fuel and spark adjustment for each cylinder...something not available back in 1981... Everyone assumed the driver would accept the rougher engine operation for the fuel economy improvement but it didn't work out that way.

The modern variable displacement systems are on engines with much higher specific output so they will make enough power to run on only 4 cylinders ( on V-8s for example). This way operation in 6 cylinder mode is never required. The engines only run in 8 or 4 cylinder mode. The real "mistake" on the 1981 Cadillac system was that it was adapted to a relatively low power 6.0 liter engine that was in a 5000 pound car...it wouldn't pull itself along on level ground in 4 cylinder mode........ the V8-6-4 system was quite nice on the older 500 cubic inch engines (which it was originally developed for but never sold on) as they could run for long periods of time in 4 cylinder mode and even climb hills on 4 cylinders quite smoothly. The 6.0 liter engine of that era was not the best candidate for that technology...

The efficiency improvements by changing the displacement are very significant due to the improvement in pumping losses running at the lowered displacement. Any (spark ignited internal combustion gasoline) engine that runs much of the time in a heavily throttled configuration will show significant fuel economy gains running at reduced displacement hence an FJR type engine would be an excellent candidate for variable displacementif only it wasn't so difficult to incorporate cylinder deactivation with direct acting cam followers in a DOHC arrangement. The compactness of this type valve gear allows little room to accomodate the lost motion when a cylinder is deactivated. Honda is one of the few companies putting cylinder deactivation in a DOHC architecture. Mercedes also did it several years ago on their high end V12 engines that were DOHC but had severe problems with the valve gear and total catotropic engine failure on a random basis. The V12 mercedes would run for long periods of time with cylinders shut down (due to the inherent excess power available in the V12) and it seems the "dead" cylinders would suck sufficient quantities of oil past the piston rings ( with no high combustion chamber pressure to keep the rings from fluttering) and the deactivated cylinder would eventually hydrostatically lock and just destroy itself... It is best to time your cylinder deactivation only when that cylinder is on the power stroke so as to trap high pressure in it to keep the rings under control. Nice try but a huge mistake by merc as it turned out.

 

[twowheelnut]

Er, slow day for you there, j? :lol:

 

[Ed_Grant]

Well I read J's post all the way through. Interesting stuff.

 

[radman]

Here's a cheap shot at Caddys system-Mr Goodwrench had hair til Caddy came out with the V8-6-4-0........