Overkill: Other than the 7.3 Gas engine, Ford has separate cam phasers for intake and exhaust. With this, they easily outperform cylinder deactivation. Hold the intake valves open (by retarding the intake cam) during the first part of the intake stroke and it's accomplished the same benefit as cylinder deactivation, without extra gadgets.
I'm aware of Ford also using reversion to "wash" the valves on the Ecoboost engines, which is why they originally didn't bother with dual injection, though they've retreated from that position. But Ford hasn't actually used cylinder deactivation in the same manner as GM and FCA have as far as I'm aware, which was the claim in the post I was responding to.
Not to get too into the weeds here, but that's an interesting description you are making, because it would affect all cylinders, rather than just specific ones. So, rather than just cutting displacement, you are modifying, broadly, camshaft/valve timing. Dual cam phasing has been around for decades (BMW's dual VANOS for example), but this is the first time I've heard somebody claim it can perform the same function as cylinder deactivation. This is doubly weird because of course Honda engines that use cylinder deactivation are OHC. Do you have some data on this that I could read?
Normal process, as I understand it, is that the cams default to full advance, and that's where they sit on startup. As engine RPM is increased, the timing is retarded, shifting the power band upwards until the camshafts are at full retard. There is however a limited range. Now, being able to advance/retard each camshaft of course allows even finer tuning of this process, but are you sure you mean the first part of the intake stroke? Because the intake valve would already be open during the first part of the intake stroke, if you are trying to bleed-off compression, you'd leave it open for the first part of the compression stroke; hold the valve open longer by retarding the timing of that event, but that sounds beyond the range one would normally allow for the phaser unless they were specifically looking to do this, which, based on Ford's use of reversion to "wash" the valves, I could see being the case.
Anyways, would love some more details on this if you have it.
Reducing engine vacuum is worth as much as 15% at light throttle. Slow the engine down, via more transmission gears is the most effective way to gain this efficiency, retarding only the intake cam is the next best method and finally cylinder deactivation still gets the job done. With 4 speed automatic transmissions, doing things with the engine was beneficial. With the lasted 8 to 10 speed transmissions that are doing 80% of this benefit, I see cylinder deactivation as a useless relic.
The HEMI with MDS was never backed by 4spd however. MDS was used behind the NAG-1 (5spd) and then the ZF 8HP for a decade now, so clearly the engineers don't share your opinion. Worth noting, despite the multitude of gears, depending on what you have in the pots, highway RPM may still be elevated. Our 1500 has 3.92's out back and is spinning over 2K at highway speeds.
GM has now chosen to get even more aggressive with their new "update" to their cylinder deactivation, which, according to
@clinebarger, is even more problem-prone than its predecessor. I can't see how they'd invest even more money in doing this if the benefit wasn't there
Food for thought on that one.
As far as failure go, they likely cause in the neighborhood of 2 failures out of 100 engines, too few to find any hard statics.
Yes, would be interesting to see some statistics on that, I expect that number is high. My dealer has never done lifters on an SRT for example, and they've sold several hundred of them.
I've seen internet pictures of cams lobes for cylinders 1, 4, 6 and 7, which are the only cylinders being activated/deactivated on a Hemi. We need a mechanic to give us a better feel for there reliability. Where I live both old GM LS engines and Hemis commonly have this issue; however, they also are well over 150k miles, and beyond anything that I'm interested in owning.
We've seen lifters from the non-MDS cylinders wiped. The problem has also happened on non-MDS engines including the Hellcat and 6.4L backed by a stick.
@TeamZero who is an FCA tech has chimed-in on this subject a few times to add his perspective. The issue isn't with MDS, it's with the improper heat treating of the pin or roller and can happen on MDS and non-MDS lifters. The latest revision has apparently had a significant impact in reducing ROO.
GM's issue, while similar, is different in the sense that it does seem to also include a failing of the deactivation function of the lifter, which the FCA lifters don't experience.
Next someone asked about how piston cooling oil jets help oil the cam. When the piston is on the downstroke that piston squirter oil is pushed at downward direction into the spinning crankshaft rod assembly. At 550 rpm the outside surface speed of the crankshaft is about 8 mph, which is the same as an exposed motorcycle chain at 23 mph ground speed. With a newly oiled chain that has quit dripping, almost nothing flies off. Spray oil onto the chain at 23 mph, and you just got a bath. Or take your newly washed car at 8 mph through a 50' long damp spot on the road, no issues. Drive 8 mph through a 50' long 1/4" deep puddle and back to the car wash you go.
Sure, you might end up with more oil flying around in the crankcase, but there's still that big ass galley below the cam blocking much in the way of any oil making its way up there. The purpose of the cooling jets/squirters is to cool the pistons, not oil the camshaft, or other components, so any additional lubrication being provided here is wholly accidental.
Anyway, as I noted, both the 6.4L HEMI and the 6.2L HEMI have squirters. So if the 7.3L Ford is also having this issue, the common theme here doesn't appear to be squirters or cylinder deactivation but the fact these are all pushrod motors and apparently lifter quality isn't what it was in the 80's and 90's, lol.
