MY10 SSV engine vibration with AFM in 4 Cyl Mode

I would look into getting AFM disabled most performance tuners can disable AFM also if you switch the car into manual gear changes it wont shut down to 4cyl. I have AFM and I havn't had a vibration problem with mine.

 

Do you have a sports exhaust fitted?

 

Can you provide a little more info about the car itself, such as any modification to engine, exhaust etc. Also when you say you have a virbration in AFM mode descibe it, where do you feel it mostly (steering, drivers seat, front or rear end of the car, whole car) does it vibrate at idle waiting at the lights?

Is there any harmonic noise associated with the virbration (do you get a drone or booming like sound inside the car when its doing it). Are there any abnormal noises (metalic) while the engine is running.

If the car still has the complete (exhaust manifold, cats and catback) exhaust system, they are fitted with flex joint at the cats and at the rear of the intermediate system. I have heard of flex joint failing at the cat end (where they bolt up to the cast iron exhaust manifold) and causing problems such as virbration and droning when in AFM mode.

As for fuel savings, stats provided by owners of AFM cars suggest they are only saving a maximum of 1ltr per 100klm of fuel more over a long highway trip than non AFM equiped V8s. In some cases where owners of AFM equiped cars have had the engine management system tuned (by a well known tuner) they have achieved better fuel economy with the AFM mode turned off.

But this might not be your cup of joe and I can understand you wanting to get the matter sorted. As for your Holden dealers response that they are not a representative of Holden (corporation) I disagree, they promote, sell the product and service it. They carry out warranty work on behalf of Holden and are instructed by Holden on how to carry out repaires. I think this makes them very much a representative (IMHO). As your vehicle is still covered by a Holden Factory Warranty I would advise Holden Customer Assistance of the claim made by the dealer and your difficulty in having your issue resolved in a timely manner.

Regardless of the location where you bought your vehicle you should not be penalised for taking to any dealer in the country and make that point clear. It appears that carring out warranty work by dealers is becoming less important and will delay customers as long as they can.

 

well put phil, i can vouch for better economy (not that i care too much after all its a v8) once tuned as well

 

How does the transmission disable 4 cylinders?

 

Hi mate,

I have what appears to be quite similar, when my car goes into 4cyl mode it vibrates through the wheel which is more annoying on the highway where it just sits in 4cyl, i even tap the accl pedal to put it in 8cyl when it gets to annoying sometimes, id even call it a slight grating feel, but only in 4cyl mode.
I took it in once and they re hung the exhaust but made no diff, and i havent had the time to take it in again, its exhaust related i reckon but why and were i dont know......

 

AFM vibration tends to vary between vehicles. My own car is noticeable but not annoying and most drivers wouldn't feel the vibes increase a little.

My friends sedan is very noticeable and feels like a tailshaft balance vibration (but its only the AFM). Many other AFM owners here on JC have mentioned various vibe levels too:blah blah:

I don't know a technical reason why some engines are different but I do know that actual dynamic balance of production engines does vary. Comes down to manufacturing tolerances. If you get a lucky mix of spinning components with close weights then your engine will be smoother than the next one off the line.

AFM works by closing both inlet & exhaust valves after the cylinder draws its intake stroke. It then uses the air/fuel mix as a compressible spring to assist the mass of the dormant cylinders to keep turn'in. Obviously many other things happen to make it all work but I could be bothered typing:hmmm:

Maybe if your engine had a slightly leaking valve to allow one of the cylinders to loose its pressure and unbalance the whole show then this might produce more vibs. Dunno just fish'in here...

I suppose in a perfect environment AFM makes sense but unfortunately does not appear to live up to the economical expectations. But for a 6.0 ltr, their not too bad.

 

If that's the only problem then get it tuned and turn off the AFM, you'll get better fuel economy and more power.
And the biggest bonus is you can get rid of the tree hugging badges.

 

Mine (MY11 SSV Wagon) works fine on AFM and I too want to keep it enabled, even when I have it tuned. I have no vibration or anything when it goes into AFM. I just wanted you to know it's possible for it to work fine, for sure.

 

I'd select a different dealer. What area are you in?

Reaper

 

Chev's Performance, Carrum Downs. Ask for Gary

 

What fuel do you use, I only use 98 and always have and dont have this problem. I cant tell the difference between 8 and 4 modes. Thank god. At least our **** box does something right.

 

Engine vibration in V4 mode is normal. My SS vibrated in V4 mode. With the stock exhaust it's barely noticable, if you change the exhaust tho it really kicked up in vibration and dreadful noise going in and out of V4 mode. With an exhaust it sounds like it throws up when it cuts back to V8 mode.... yuck.

I have HP Tuners, so I just disabled the V4 mode. I was worried about economy but with a few tweaks I got more power now and better economy. V4 mode is hopeless for daily commutes if you live anywhere where your going up and down hills.

I spend 65% in the city, 35% highway. I got about 400km to 64ltr with V4 mode enabled. With v8 mode only and some tweaking, I get around 450km to 62ltr. I wanted sound V8 sound so I trialed a number of diff back exhausts, none of which will work with V4 mode enabled.

V4 is only good for like Sydney to Melbourne trips if you have constant speed on a highway, other then that it actually stuff's the cars fuel trims, causes more knock retard (even if only Burst Knock) all of which kill economy. The biggest reason why V4 mode killed my economy was because it was forever switching back and forth and thus had twice as much work to do with compensating for burst knock mostly etc. (cutting power to ensure the engine runs good and doesn't run into knocking constantly).

V4 mode really is something that should be left to a VVT setup I personally think. Trying to get a pushrod motor to be efficient by such measures is a waste of time. You can tweak deacceleration fuel cut off and other things to help economy to compensate so.

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V4 mode was a really dumb idea. This is probably why 99% of tuners disable it and still improve economy......... AFM is annoying to tune and really offers no benifits not to mention it's obviously bad for the engine if you took thru all the protection gear in the tune when in V4 mode.

PS. The vibration is essentially caused by two things. One the engine itself and two the exhaust being designed for v8 resonance, not v4. Anyway thats my two cents from having an SS and starting to tune it for the past 2-3 months. I'm pretty sure even your Holden manual for the car says in it somewhere you'll have some minor vibration but thats normal.

 

are you taking it to Frankston Holden?