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It definitely has me thinking about better mpg more than I ever have.
Thats also the beauty of most Honda designs. It allows folks to discover things and often take control and use it to their advantage.
If Honda chooses to make the Accord Diesel smoother, they might choose to use it in that model as well.
Remember, all pistons are still running even in I-3 mode. The extra vibration comes only from lack of burning fuel on one bank (not so much in 4-cylinder mode, since it is actually a V4 layout).
26.63
26.64
26.78
27.31
27.20
27.38
26.67
Funny, my 2000 3.0l V6 Accord got 28 mpg the first tank and 28 mpg at 196K miles. However, I doubt my 16 yr old daughter gets 25 mpg the way she drives it now.
A high-pressure turbo and an intercooler may be a complex system, but a tried and true system as SAAB initially used this system in the early '80s SAAB 900 Turbo. It's a very reliable design, and a high-pressure turbo will easily reach 150K miles without a failure if one changes oil regularly and uses a quality oil in the first place - and, not shut the engine down immediately after high-speed operation, so that you don't cook the oil out of the turbo's bearings.
Diesels, especially those used in over the road trucks, have been using this design for many years, and it's truly a reliable solution. I think some are just concerned with the long-term reliability question of the VCM system.
Like every technology, it has evolved over (now) two decades, with VCM feature added five years ago. Diesels aren't the same old thing either. A lot of complexity has been added besides turbo/intercooler. You can't compare today's diesel to diesels from two decades ago, could you? One could even argue against the new catalytic converter, the new casting techniques, the common rail design and so on.
But if we were to be wary of every new development, we might as well stick with a Model-T. I'm sure it didn't have the engine mounted even on a subframe, much less an active control/hydraulic mount. :P
VCM uses VTEC. Honda has been doing something similar for ages that a lot of folks probably don’t know about. That would be selective opening/closing of valves. In these applications, at low engine speeds, the 4-valve/cylinder engine in the four-cylinder Accord operates in 2-valve/cylinder mode. One intake and one exhaust valve are kept shut. This design has been used in several engines (including Honda VFR where it is called Hyper VTEC).
VCM takes the same idea a bit further by not closing two of four, but all four. It is about as simple an idea as it can get. This was used in cylinder idling system in first generation Civic Hybrid as well. Unlike VCM which operates under a variety of situations, the cylinder idling system shut three of four cylinders only during deceleration.
There are downsides to VCM, however, and one of them is due to the fact that it is applied to an engine design that wasn’t designed around it. It has limited the choice of cam profile. Unlike normal circumstances, VTEC can select between two cam profiles, one for low rpm performance and the other for mid-high rpm performance. By limiting to one profile, the engine now becomes more like one without the VTEC advantage in terms of performance. The performance aspect has been replaced by VCM aspect.
This is the reason Accord V6/VCM feels a bit softer in low-mid range (than non-VCM version of the engine) since its cam profile is better suited for high rpm performance. This would also be the reason for Honda’s choice to choose 3.5-liter engine over 3.0 or 3.2-liter in Accord. With that little compromise, the car still has the performance of being powered by something like a good 3.2/V6 in low-mid range for around town driving, while also benefiting from VCM in terms of fuel economy. For highway passing power, 3.5/V6 power would be available.
I messed around with the cruise control a lot during the trip. I found that my 5-speed auto tranny makes worse decisions about when to shift while under cruise control then it does when under the control of my own foot. The cruise wants to maintain speed and so the transmission often downshifted to prevent any loss in speed. When controlling the throttle myself, I was often able to keep the car from downshifting, while only loosing 5-7mph on a hill. Even beyond the issue of downshifts, I think the grade-logic simply works better when it gets the input of the human foot, rather than the single-tracked "mind" of the cruise control.
My point is that you might be able to better evaluate the VCM system when the car is making fewer transmission shifts. So, at least in my experience, you might want to keep the cruise off.
....your point is well taken. In fact, your entire post was right on the money, IMHO.
What I can't figure out: Why is an obviously clued in hombre like you driving without triple cone synchros, a clutch and a vertical shaft that does more than offer lip service to poseurs (forgive the spelling:don't use that word very often)
Seriously, good post!
best, ez....
Based on my observations, Honda’s cruise control and transmission shifts tend to be firmer for first few thousand miles and they either learn or seem to settle down after that. You might notice a few things turning smoother around the time you get the first oil change done (around 7500 miles?).
BTW, I will also recommend to not replacing the original oil at least thru 5000 miles, and this may be mentioned in owner’s manual. Most of us seem to focus on break-in as something about throttle usage, but rarely about impact on brakes and oil. It might be better to keep an eye on it though, around 3000-4000 mile. If it is in good condition, keep going.
- In I-3 mode, valves on all cylinders on the rear bank are shut down.
- In V4 mode, valves on right outer cylinder in the front bank and valves on left outer cylinder in the rear bank are shut down (I may have front/rear bank switched).
- At the time the ECU issues the command to shut down the cylinders, PCM cuts off the fuel supply to those cylinders. However, the spark plugs still ignite (to keep the cylinders warm and ready). The pistons still move in the idling cylinders. The only thing that isn’t happening is intake of air, injection of fuel and the rest of the process.
As I had mentioned earlier, in non-VCM designs, Honda has used VTEC to shut down half of the valves in each cylinder (one intake and one exhaust) at lower engine speeds. This is being done even in 2.4-liter I-4 Accord that is PZEV rated. The same has been done to improve performance as well. In motorcycle world, Honda calls it “Hyper-VTEC”, used in VFR. Interestingly enough, this design pre-dates VTEC moniker. It was launched as REV in 1983 Honda CBR400F. And REV was really the beginning of VTEC which was launched six years later in cars (beginning with NSX, in 1989).
VCM takes that original 2-valve or 4-valve set up from REV to 0-valve or 4-valve set up.
I got the auto tranny for funny reasons (it is the first auto I have ever owned in a non-SUV). The dealership gave me an outrageous deal on my 98 Accord, such that I didn't want to give them much time to reflect on their offer. If I agreed to buy an 08 off their lot, they also gave me almost 1000 off of MSRP and threw in the auto-tranny and a spoiler for free. (The auto was free because I told them there was no way I would pay for something I REALLY didn't want). It seemed like a no-brainer to me . . .I loved everything about my 08 EX-L silver w/ black leather, except the auto transmission. I test drove it many times and found the auto to be very impressive ---for an auto! I test drove everything under $35k and found the Honda auto to be superior to any other brand. Finally, although I have always driven my cars for 8-10 years, I had intended to purchase the Acura TL when I saw the Honda - so I'll be taking a serious look at the redesigned TL in 2009-2010. I figured an auto, 4 banger is the easiest to unload without as much depreciation.
I'll bet that's more than you wanted to know . . . thanks again for the compliment!
Obviously $5 - 7K or so more but might be worth the wait...
Had to make a choice for my 08 Accord w/NAV purchase as to whether the V-6 or the 190 hp I-4 would be best.
Gave this some thought about VCM and decided that since I will be only using 4 cyl instead of the V-6 on the highway, unless passing or going up hill, It would be a waste of a good money purchasing the V-6. Saved the money, and happy with the decision and find no issue passing other cars on the highway.
Where do you live? While I could go to a dealership to experience one, I would rather see it work in a friend's car (if I can call you that) over different situations.
http://www.driveaccord.net/forums/showthread.php?t=13506
i am so bummed out right now.. I waited for this car for 2 years and was so excited when I picked it up. I have a sick feeling now that I have what will become a nightmare on my hands,, someone walk me off the ledge! how does one return a car they just bought with 1100 miles ?? :-( I bought the 2003 V6 the 1st month it came out and never had any 1st gen issues.. i loved that car and now really miss it.
http://www.vtec.net/forums/one-message?message_id=713706&page_number=1
Honda must do something to remedy this as more owners come forward or I predict V6 sales to suffer as people learn of this operational concern. I trust that Honda will find a solution and do the right thing to make the VCM issue/s go away and/or completely transparent. At least I hope they will.
http://www.driveaccord.net/forums/showthread.php?t=13506
http://www.vtec.net/forums/one-message?message_id=713706&page_number=1
That said, I'm sure it can be felt a bit (like transmission shift can be, especially with colder weather).
....I wuz tempted to do the same thing for another poster - - - - then a sparkling post concluded with a preposition (so my praise remained undelivered and elroy got zinged by the mod for a non-grammatical effort)....
...actually, this board is fun and has a lot of positive attributes....
best, ez...
Since all professional reviewers of the EX V6 have mostly praised the car with no hint of hesitation or surge that you describe, this leads me to believe you bought one with a rare but annoyingly real "bug" in the VCM mechanism.
CR in their preliminary report on the EX V6 which was recently released on their website, has only good things to say about it.
It can be felt ALOT. its ridiculous and my prediction is MANY more unsatisfied V6 owners will come forward. The vibration is very noticable and the surging is uncomfortable. Having a "clue" comes from experienceing the issue that others and myself are feeling. Your lucky that you have not had this issue,thats great. but the new engine has issues,, plain and simple and people need to be aware before they buy.
Thanks for the kind words.....