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Old August 4th, 2019, 11:29 AM   #1
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Question Turbos, VCM and Tuning on J35Z2

I've read up alot in posts around here and followed the long thread from NVA-AV6 about a 7th gen turbocharged accord v6 build project a while ago.

Owning a 2010 Sedan 3.5L V6 with the J35Z2(Auto) VCM Engine, I'm having a hard time finding actual tested information about this motor as very few/none have actually shared details about actually modding and dyno-testing this engine, besides general pointers.

1. Why does nobody tune the J35Z2 for a turbo build? Let's say hypothetically I procure a custom turbo manifold for a single turbo setup, acquire all parts required. I know people keep saying VCM is a hindrance. But where Exactly does VCM stall me in terms of tuning?

As I understand, VCM engages only on very light throttle, which is not enough to spool the turbo. As I go WOT/heavy foot, VCM immediately disengages, so I don't see how it interferes with forced induction.

Reading up more on it, the cam lobes on J35Z2's camshaft for VCM-deactivating cylinders are just circles, so the valves for those remain shut in VCM mode.

I just don't see how VCM can mechanically affect tuning.

Of course I am just getting started with knowledge and hands-on experience with all this and might be completely wrong or missing a major point here.

People mention that maybe the OEM ECU triggering a secondary map under VCM mode interferes with the primary map. But all this information seems to be speculative most of the time and I haven't yet come across any tested results.

Has anyone ever actually turbocharged the J35Z2 successfully while preserving VCM (maximum fuel economy under part throttle, even if the difference in gas mileage with/without VCM is about 2 mpg)?

2. Seeing that KTuner has the ability to disable VCM and tune AF ratios/timing, etc. on the J35Z2, can KTuner be used to tune a turbocharged J35Z2 setup?

Also with the above questions, I also am ignoring the weaker automatic tranny's ability to handle any significant power (340 whp+).

I'm also ignoring the fact that the Accord handles like a boat stock and is a FWD not ideal for such power (Wheelspin/A family sedan).

I'm also not taking into account the general hate for VCM due to part failure/design issues, as I personally like having the extra 2 mpg and haven't yet come across any fouled spark plugs/worn engine mounts/noticeable vibrations on a properly maintained 10+ years old car (Maybe I got lucky).

I'm strictly speaking about just tuning this particular VCM engine.

What I can't wrap my head around is if people have poured down money for built FWD inline 4 turbo civics with 800hp+ (which indicates sometimes money isn't really the issue), why are built turbo J35Z2/Z3 so rare/non-existent?
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Old September 4th, 2019, 02:33 AM   #2
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Bump. Anyone?
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Old October 7th, 2019, 09:57 AM   #3
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Couldnt agree more
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Old November 3rd, 2019, 04:59 PM   #4
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The cam lobes for VCM deactivated cylinders are NOT just circles. When VCM activates, it triggers a solenoid that stops the cam follower from pushing the rocker arm, so the rocker arm can't open the valves. Not that this answers your question, I just figured it was good to clear it up.

It is definitely possible to turbo an 8th gen. My biggest fear is that it will force the auto trans to give out sooner than its already short life expectancy.
There are plenty of things that you can be afraid of, but if you are willing to risk it, I don't see why you can't.

The one thing I don't understand is why you would bother to keep VCM enabled. Even on low boost you are going to be throwing way more fuel at the cylinders, way more than you will be saving with VCM. Could you keep VCM on? Maybe, but why risk something going wrong when you could totally eliminate the risk by turning it off?
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Old November 9th, 2019, 08:11 PM   #5
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I have an 04 accord coupe j30a4 stock internals boosted which has been riding good since 2017. Havent had any main issues.....can only use the hondata flashpro with the jseries motors
7th generation
03 accord coupe
HFP lip kit
Spec stage 4 clutch
Modified siemens injectors 560cc
Hondata Flashpro
6speed tranny
60mm borg warner
9 pounds
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Old December 20th, 2019, 04:46 AM   #6
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I think we see so many civics and such with high-hp is because they are a cheaper, more abundant platform. Although the j series is becoming popular now, it wasn’t really popular back in the day for a few reasons. Everyone and their mother could get a B series in the late 90’s/early 00s. They were tried and true, fit in almost anything and the aftermarket is unbelievable. There are a number of transmission/engine combos, hell even the b tranny can mate to the h engine now.

To put this in perspective, the Honda J series wasn’t used until 1998 in the accord v6, and even then, it only came with a bunk-ass 4 speed auto that was known to give out at the first sign of torque. Honda didn’t make a manual transmission for the J until 2003 with the cl-s and the new accord v6. And even now, they’re hard to come by. The fact that the J series came on a few years later, had auto trans problems and a manual wasn’t available for the first 5 years (and is still hard to find). I think there’s so little accord builds for a few reasons:

1) the autotragic trannies are known to go, even in stock form, which scares off anyone with an auto that wants to make a bit of power. Anyone who daily’s their accord probably doesn’t wanna do a tranny, esp. on the newer 8th gen and up accords which seem to be more valuable than the 7th (I have a manual 7th gen I got for ~2k, people almost give these things away).

2) the lack of manual trannies. The only transmissions for the these cars that can hold any power are the manual ones, which not many people have. They are often expensive, and if you want the LSD from the TL, you really gotta pay to play. As well as the older 7th gen accord/o4-08 tl manual transmissions won’t line up to the 08 style engines, and the bell housing/clutch case housing needs to be swapped over. The time/effort/cost is often not worth it for people just to obtain a transmission to handle the power they plan to make.

3) the civic is not as “luxury”, older, and more abundant. They’re easier to come by, which means less value. As well, any civic from about 1988 to 2000 can take pretty well any Honda motor you can fit in it, and can be obtained cheaply (granted older ones are getting expensive). It’s easier/cheaper to tune an old civic (as mentioned, the j needs hondata to tune), easier to come by, parts are cheaper and more abundant. Although it may seem like these civic owners have “poured” money into their cars, they get the results, because it’s a tried and true platform. Since the 90s people have been making crazy power on the civic. The accord, not so much (not to say it can’t be done, but because it’s not as “tried and true” there’s a lot more room for error/things that people spend money on and didn’t need to).

Not trying to discourage, but the civic has been a legend since about 1992. The VCM auto accord, not really an enthusiast platform. I think people are terrified of breaking engines and trannies/voiding warranties with their still-new accords. I imagine we may see a pick-up in the enthusiasm for accords once the v6 gets older and the value drops a little. But think about it like this... if you blow up your 4 cyl b series Honda, it’s a lot less expensive than blowing up your 2010 VCM Honda V6.

People know what works and what doesn’t with civics. It’s easy to come up with a recipe for a built civic - make a list like for a grocery store with a goal in mind, and slap it together. We know what fits, what doesn’t fit, what needs to be jimmied and jammed and what can fit together to make what work and what sensors will work with what engine, all kinds of little stuff that people have figured out over the years. The technology is simple and straightforward compared to 15-20 years later.

No one wants to touch a fairly new, still-valuable and expensive engine with unfamiliar technology. and not to mention a questionable transmission. Don’t mean to discourage but it’s too new and unfamiliar, that’s why.
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Old December 20th, 2019, 05:06 AM   #7
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Not to say it can’t be done, but personally, if I were to do this, I would use an older accord to keep costs down, with a manual transmission to hold the power, and a non VCM v6 for ease of tuning/reliability (not much experience with the VCM but I’ve heard quite a bit). Again, it can be done, but for the money spent, there’s better platforms to do it to. Hell, even a manual 7th gen, an early cl-s/tl-s or a j32a swap 6th gen would be a good turbo candidate in my opinion. Once you get into the DBW/oval exhaust port era though( 7th gen accord/04+ Tl) **** gets expensive.
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