technicalninja

This might be the single most important thread I ever create on this forum.
This should help many many members.
And this has ABSOLUTELY nothing to do with Miatas....

Cylinder deactivation...
It's called many different things but it all works in the same way.
Basically it works by cutting fuel and spark to cylinders to "shut them down" as an attempt to increase fuel economy.
This is not a big thing. What they do with the valves is the killer here.
They disconnect the valves from the valve train and close the valves in the deactivated cylinders.
Over time this DESTROYS the rings and it destroys the rings ONLY!

If you had asked me "how can you wipe out the rings ONLY in an engine leaving everything else perfect?" I would not have been able to give you and answer before I saw this crap...

What happens when the valves are closed on a running engine is thus:
Initially the trapped cylinder charge would create tight spots in the engines revolution. Over time (pretty quickly IMO) this trapped charge escapes via the ring gaps and the cylinder has a little bit of residual pressure at TDC.
It also goes into DEEP vacuum at BDC. At 1800 rpm it's doing it 1800 times a minute (it's not 4 cycle anymore).
That cylinder cools down FAST. Commonly heat = pressure and vacuum = cold.
The rings are designed against PRESSURE. Not to keep vacuum in.
The rings are pulled in a non-standard manner. Probably much "fluttering" happens.
This cooling down, then being re-heated, and being loaded opposite their design destroys the rings.
It doesn't happen fast but it reduces the engines life expectancy by a factor of 2-4. Your 300K capable engine before DOD is now a 100K engine with it...
I've seen evidence of this in both Honda V6 and Chevrolet V8 engines.
The NORMAL symptoms are increased oil consumption and **** poor spark plug life in the DOD (displacement on demand) cylinders.
Spark plugs come out trashed, heavily oil fouled, insulators cracked/missing. The non DOD plugs in this same engine are perfectly fine...
This is such a bad issue that the latest form of this crap from GM puts DOD on all 8 cylinders and they stagger the operation.

I did a rebuild on a Honda V6 because of this. The oil consumption reached a level that badly carbon fouled the exhaust valves to the point that one of them SHATTERED and we had a dead cylinder.
Before this I had never seen a single shattered valve in an engine. I've had a **** ton of burned valves, I've had shattered valves (multiple) from catastrophic failure but never a single shattered valve.
The bores in the DOD cylinders were PERFECT but had the most mirrored finish I have ever seen.
The rings on the DOD cylinders had gaps in the .030-.045 range.
The rings in the normal cylinders had gaps in the .015/.018 range, basically new.
The really wild thing was all of the rings in the DOD cylinders had lined up the gaps in a perfect line. This included the oil control scrapper rings...
How in the hell did it do this??? Those scraper rings are sort of held into position by the expander between them...

A set of rings, refinishing the bores, one exhaust valve, and a VCM deactivation device fixed it...
It had 105K on the engine, Old people owned it from new and maintained it perfectly. It was NOT abused.
It was expensive to fix...

All DOD systems can be deactivated. In the case of the Hondas I install a device that alters the CLT signal to the PCM a little tiny bit as the VCM crap will NOT activate until a specific temperature has been reached.
We trick it with a slightly low CLT and the long term fuel trims take care of adjusting the fueling appropriately.
I spoke with the guy who designed the units I use. He went through the process of getting it approved CARB approved. It doesn't change anything except it kills off the DOD which Honda calls VCM (variable cylinder management).
The guy who designed it owned a 08 Odyssey which went from no oil consumption to a quart every 500 miles. His engine did not eat itself and after killing off VCM his engine reverted back to no oil consumption.
He did not replace his rings which I am sure have monster gaps on the DOD cylinders...
His crap started at 120K and he has 185K on the van now...
He said his BIGGEST customers now are Honda and Acura dealers. He said they don't charge their customers for the devices, just install them to stop the oil consumption.
Honda has had class action lawsuits over this crap. Google Honda VCM if you want more info.
The parent companies CANNOT deactivate this stuff as their fuel economy numbers were tested with this crap installed. DOD does actually improve fuel economy a little tiny bit (MPITO IMO)

TL/DR - find a way to kill off DOD as soon as you can. There are dongles you can plug into the OBD2 port on GMs that work fine. There is stuff available for the Hondas that take just a few minutes to install.
Save you engine! The manufactures DO NOT care if it dies after the warranty runs out (in fact they prefer that it dies) and ALL DOD crap will make it through the warranty period...

And yet another wall of text.
This one was IIMPORTANT!

MetalMuffins

iTrader: (1)

Have a cat good sir.

deezums

iTrader: (3)

I am putting a odyssey engine in a pilot because of this dumbass ****...

Is there any way to defeat VCM other than lying to the ECU about coolant temp? Because as I understand it the coolant gauge no longer works to show overheat when the "fix" is mucking with the CLT line, and the one who killed this one didn't care the oil ran dry, sending it back with a dead or worthless coolant gauge is not a good idea IMO.

Erat

iTrader: (5)

I would not deactivate the GM system with software. I would absolutely do a DOD delete by replacing the lifters and all that. I say that because i've never seen ring failure and i've seen PLENTY of lifter failures. And honestly, if you use them enough and you keep the RPMs down they'll last for a long time.

technicalninja

I use VCMTuner's stuff. Only the advanced one.
Products – VCMTUNER

The unit takes 2 or 3 degrees off the signal. The temp gauge works perfectly fine just shows temp a RCH lower than before.
Read his stuff. He was impressive to speak with and he is NOT a wrench like I am...

I agree with Erat fully. The GM DOD lifters are PURE ****.
Sadly to properly dispose of them you have to take the heads off, close some oil ports, and modify/replace the valley cover.
The Dongle will turn them OFF for less than $200 and requires 5 seconds of work. It is also easy to remove if your still under warranty (remove dongle, disco battery, drive 50 miles). Google "AFM delete" for tons of options.
Dongle is a fast and dirty way of stopping damage to the rings. Most customers can afford this method over the correct way...

If you ever take heads off of a late model GM V8 and you leave the DOD crap in...
Shame on you!!!!

technicalninja

Another bit of information regarding the Honda application of this junk.
VCM enabled V6 engines REPLACED the VTEC portion of the magic and replaced it with the VCM equipment.
No more nice bump in power at 5K rpm do to the loss of the long duration profile. Loss of torque down low do to the loss of the low duration profile below 5k.
It actually say "IVTEC" on the engine cover. They lie! No more VTEC at all. They made it whimpy AND super expensive to fix. Honda appears to have "lost their *********" sometimes around 2004/2005 and have been on a ECO/green path since then.

This engine ALSO requires $2K computer controlled motor mounts to make the 4 and 3 cylinder modes smooth.
It also has a "white noise" generator for operation in the 3 cylinder mode.

None of this extra complexity is needed if you disable the VCM...
It actually has PCM codes for motor mount failure. You have to put a resistor in-line if you're replacing them with stock non VCM mounts ($1300 cheaper!)

technicalninja

And another note...
I prefer Toyota over Honda. They are more reliable.
I was driving a customers 2013 Lexus RX350 and I noticed an ECO light.
I started shitting bricks...
Toyota also getting into this junk was very depressing.
A bit of internet searching revealed that Toyota was NOT installing DOD equipment.
It was just a "feel good light" that illuminated when you were driving the car in an efficient manner; low throttle opening, high vacuum mode...
Not a problem at all. Just disregard the little green light.

I then began to wonder if the application of a "psychological" light actually achieves better fuel economy improvements than the actual DOD equipment.
It might, it really might.
Better to train the monkeys than hobble the equipment...

rleete

iTrader: (21)

This has been the overall story of my entire career.