[Benjamminz_IS]

How hard would it be to make a kit for the IS that added a "displacement on demand" feature for those that make some road trips or a lot of highway driving at cruising speeds?

I'm sure it's not as simple just turning of injectors for cylinders... but then again I know nothing about how chrysler and honda go about achieving their versions of this technology...

 

[HoustonLex]

I've only seen displacement on demand used on V configuration motors where an entire bank of cylinders is cut off...

Honda uses it on their V6 and Dodge uses it on their V8...

Considering the IS300 is an inline six, it would be more difficult. The IS350 on the other hand may be much easier

 

[kuuligan]

It will be kinda tricky because all 6 pistons share one crankshaft.

Maybe its moreso of messing with the electronics

 

[Crester]

Could you shut off every other cylinder??? Like maybe have cylinders 2, 4, 6 shut off... and 1,3,5 running? That might help with the balance?

 

[Benjamminz_IS]

Could you shut off every other cylinder??? Like maybe have cylinders 2, 4, 6 shut off... and 1,3,5 running? That might help with the balance?

This is what I was thinking... but I was reading about the way GMC accomplish this and it sounds like their head is somewhat complicated, but I'm not sure if it is necessary.

The way theirs works:
"To switch the engine from 8 cylinder to 4 cylinder operation, the computer operates four solenoids that control oil flow to special hydraulic lifters for the intake and exhaust valves for cylinders number 1, 7 4 and 6."
...snip...
"Hydraulic oil pressure, supplied by the engine oil pump and controlled by computer-activated solenoids, is used to dislodge the locking pin and collapse the lifter, thus closing the valve. In reactivation mode, removing hydraulic pressure causes the locking pin to return to its latched position to restore the lifter's normal function. The computer stops valve operation for all four of the cylinders within one engine cycle or two revolutions of the crankshaft.

Synchronizing the throttle opening, fuel injector control and spark advance with the valve deactivation is the difficult part and GM has mastered the programming for this critical sequence. I could not tell when the engine was switching between 8 cylinder and 4 cylinder operation. There are no indicators on the GMC Envoy to indicate it has the DOD system nor any visual indication to the driver that the engine is running or 4 or 8 cylinders. I did notice that the average fuel economy readouts on the trip computer did keep improving as I was cruising or coasting. Sit at a stoplight or accelerate and economy decreased.

During start-up and idle, the Vortec V8 runs on all 8 cylinders for smooth operation. During acceleration, all 8 cylinders provide power but the system switches to 4 cylinder operation during light throttle cruise or deceleration. I hooked up a computer scan tool that GM technicians use for diagnostics and checked out the readings as the system switched. In a short 10 minute city drive route, the system switched between 8 and 4 cylinder operation over 40 times. The only way I could tell this was by looking at the computer data. There was no roughness, hesitations, r.p.m. changes or any other sign of the DOD system operation other than my scan tool readouts. "

I'm not sure if keeping the intake/exhaust valves from opening is necessary, this is my main concern. If it IS necessary, then I fear this will be a little to hard to design and make practical... but who knows maybe someone here who hasn't read this yet knows enough to school me on this =)

hope everyone is enjoying their sunday!

 

[Benjamminz_IS]

sorry I had forgotten what I actually read so I went back and found the article and quoted it... above post edited...

 

[agent009_98]

Could you shut off every other cylinder??? Like maybe have cylinders 2, 4, 6 shut off... and 1,3,5 running? That might help with the balance?

that's right. Houstonlex is wrong. in V configuration, it's v8-v4 and v6-v3. Honda have the active engine mounts that can change its damping properties to counter vibrations due to change in firing order.

 

[Benjamminz_IS]

that's right. Houstonlex is wrong. in V configuration, it's v8-v4 and v6-v3. Honda have the active engine mounts that can change its damping properties to counter vibrations due to change in firing order.

I would think the v6 would definetly be a "shaker" in v3 mode... I would even think almost "scary" shakey... v8 in v4 mode shouldn't be too bad... but I think our I6 would fare the best as far as vibration/balancing is concerned...

 

[Benjamminz_IS]

though... now that I think about it... the only thing you are really taking away from v6 and v8 is detonation of the specific cylinders... and I doubt that the detonation of those cylinders really adds much to the vibration... as you still have the same rotating mass, less the fuel... then again a higher compression ratio probably would also effect how "shakey" an engine in "half displacement" mode would be...

 

[nocash]

Good point.

However, you have to consider the energy generated by the detonation itself (newton's#3).....take those detonations away in an unblanaced fashion and you're going to get the shakes.

DoD is a funny technology. It doesn't provide huge fuel efficiency gains (i've read estimates of 5-10%) but it was relatively complicated to perfect. Now that it seems to be perfected, it is relatively cheap to implement and it should propogate.

But with pretty modest FE gains, it makes me wonder why they bothered in the first place.

though... now that I think about it... the only thing you are really taking away from v6 and v8 is detonation of the specific cylinders... and I doubt that the detonation of those cylinders really adds much to the vibration... as you still have the same rotating mass, less the fuel... then again a higher compression ratio probably would also effect how "shakey" an engine in "half displacement" mode would be...

 

[Benjamminz_IS]

supposedly they've gotten gains of 20% on some vehicles... maybe not "steller" performance... but I think these numbers can also be tweaked with more programming of whatever ecu/piggyback module you use... that is if it can even be done on the IS... I am going to get the answers somehow... and will definetly be posting my findings...

but yes, you are correct about N#3... which is why I think our engine would recept this technology more gracefully...

 

[Benjamminz_IS]

what will be interesting will be to see an I6 hybrid with this technology... I'm sure there is one in the works on some engineers computer... if a prius can get 65mpg i bet with this technology added they could get near 80mpg... and for a commuting vehicle that would just be awesome... i could go almost 3 weeks without filling up, as far as getting to work and back... heh... that would be crazy...

 

[agent009_98]

i think direct injection is the way to go. It's much more simple compared to conventional DoD.

 

[METEORO]

It will be kinda tricky because all 6 pistons share one crankshaft.

Maybe its moreso of messing with the electronics

???? you lost me there. Not aware of any engine that has mulitiple crankshafts.

 

[HoustonLex]

???? you lost me there. Not aware of any engine that has mulitiple crankshafts.

what about the W8?

 

[agent009_98]

I think the w8 has one crankshaft...

 

[TTilE]

???? you lost me there. Not aware of any engine that has mulitiple crankshafts.

I think he's more referring to the vibration issues.

 

[HoustonLex]

I think he's more referring to the vibration issues.

I think he meant camshaft

 

[Inspar8r]

I think he meant camshaft

for his sake, i hope so.

 

[TTilE]

I think he meant camshaft

Well that would be just as incorrect as saying the problems assoicated with a single crankshaft engine compared to a multiple cs engine. It was not a very credible statement by any means, but I think what was on his mind was the vibration issues assoicated with shutting off cylinders attached to a crankshaft with insufficient dampening capabilities (and of course I would include/attach the other dampening mechinisms in the engine to that last point).