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Discussion Starter #1
It’s been two and a half years now since I added my 2007 QP to my collection and I have to say I do enjoy it, it’s a 4.2 drysump sport with Cambio corsa gearbox , I spent all my working life working on what we refer to as exotic cars and as such the mechanic in me cringes every time I hear the variators rattle , it’s only for a second or two and only if the car has sat overnight, once running there was a slight noise fron the engine when listening with the hood open but of no concern and I wrote it of as normal the car has also always had a slight roughness at idle again no issue as I am comparing it to my Bentley and my S550 which is probably unfair .
Well I got around to the variator noise last week , testing for stored oil pressure in the accumulator under the manifold showed none not a supprise as I don’t se any valve to close off the system when the engine is shut down , so it appears to only store energy while the engine runs and it’s charged .
I decided to fit a small one and a half quart accusump in to the system which would store oil under pressure while the car was not in use . It’s mounted under the hood beside the brake servo and is not visible once the plastic covers are installed it feeds through an electric solenoid to a tee and two hoses then connect the fitting in the left head and the hose to the original accumulator . When the engine is cranking the solenoid opens charging the system on both banks before the engine starts , when the key is switched off the solenoid closes and so stores oil under pressure ready for the next start .
The results, absolutely amazing! It starts even after standing for a couple of days in complete silence , you would think it was a Tesla , all I hear is the exhaust note , secondly and surprisingly it’s much quieter at idle and while driving and the idle is noticeabley smoother , I guess the variators must have been rattling about just a little bit at idle and upsetting things .
This has transformed the experience and all for about $600 Canadian .
Very happy so I thought I would share .
Happy motoring Dave
 

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Interesting read. Have you got any photos of the install?

Cheers

C
 

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Would really like to see some pictures on this. And if this does work, I can tell you, but you probably already know, how many Maserati owners this can help. looking forward to an update on this.
 

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Discussion Starter #4
Sorry but no pictures as yet , I do intend to move the position of the oil pressure gauge to a more convenient spot in the near future and I will take some photos then , posting may be a challenge with my rudimentary computer skills,
I have driven the car quite a bit now since the first post and still nothing but good results , another side benefit is that as the engine is so much smoother the clutch take up is also smoother by a considerable amount . I have the drive by wire enhancement fitted but it was always a little juddery on initial take up especially at low throttle or creeping along in traffic now nice and smooth .
Dave
 

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It's surprising to me that even while under "normal" driving conditions that the engine is smoother, etc. I'm not the sharpest knife in the drawer, but this suggests to me that the oil supply to the variators must be marginal at best. I would think your modification would really help those folks with the Automatica (ZF) transmission.
 

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Discussion Starter #7
12 cylinder , I would think that the variators in my engine were suffering from a low capacity of oil supply due to a small capacity to store any volume in the original accumulator, this was allowing the cams to rattle back and forth or flutter if you like , much like a loose timing chain would or a worn distributor (if you you go back that far ) would do with ign timing.
If this were the case on an automatic I think the damping effect of the torque converter would help to cover up the problem rather than the solid connection of a clutch .
I will take some pictures and pay attention to the oil pressure gauge readings when I next find some time . While being retired I am quite busy at present preparing a 1931 Alfa Romeo 6c gran sport Zagato for its upcoming season of competition as well as several other projects.
Dave
 

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Hello Silver spur....a 1931 Alfa 6C Zagato....!!! Wow...!!! That is like a "holy grail" type of car! I can't think of a better way to enjoy being "retired"! Your explanation about cams "flutter" makes sense, so the issue is likely oil volume and not oil pressure. I used to have a QP Sport-GT with duo-select and loved it. My wife is permitting me to get another QP, but it has to have the ZF automatic. So I am wondering if your modification will work on the wet sump cars, as they seem to have considerably more variator issues than the duo-select cars. I wish you great success with your Alfa...!
 
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Wet sump and dry sump variators operate entirely differently...Wet sump are not making noise because of lack of lubrication, it is because they are not returning to the base locked position...I have had wet and dry sump ones all apart several times...Jason
 

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Discussion Starter #11
Hi Erik.
Well it’s been a year now since I installed the accusump and I couldn’t be happier with the results .
The car gets limited use as I have other cars I also drive so it’s sat often for weeks with out use , happily the accusump has retained pressure for as long as 3 months while I was away during the winter , the first start was perfect with not even a hint of rattle . It continues to start silently under all circumstances and runs smooth and evenly .
What else is there to say it just works
Cheers Dave
 

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I would like to know you thoughts on replacing the variator accumulator. The accumulator, according to the manual/training books is described as the device that supplies/stores the pressure for the variator advancement. I am trying to understand why the same device in the F1 trans which is used to supply immediate pressure for engagement and gear selection is a maintenance item, and the one used for variator oil supply is not considered something that is prone to age.

Doesn't make sense to me. At all.

I do understand that 40-50 bar in the F1 system is not the 12-14 in the variator, but the role of the accumulator is described to be the same.

Now in the beginning of my posts regarding the high pressure variators (speaking of dry-sump units only), I was also perplexed as to how:

1. Both sides nearly always fail, and at the same time, right down to the minute. There have been no documented cases I could find on unilateral failure. This is not the case with the wet sump cars, indicating the wet sump variators themselves were prone to causing their own failure.

2. It has NOTHING to do with maintenance. I have seen many fail early in life and others NEVER fail, regardless of condition of deferred maintenance.

3. Many of the repaired cars come back to the dealer with subsequent replacements. I have seen 3 jobs at 80K miles on one car. Others have 130K miles and no failure. The ones that fail many times are typically sold and wind up back on the secondary market.

This all points to there being an underlying cause to the failure. Something is failing pre-variator and causing immediate, accelerated wear.

Here's the kicker, and the point to all this:

I just spent $10K on new variators, seals, bushings, variator solenoids, etc. Everything right from Ricambi and NIB.

1,000 miles later (this week), variator rattle is back!!!!!

Everything is NEW! Jason and his team did an AMAZING JOB, with the work, doing everything that was discussed and it was apparent that there was wear on the bushings and these parts needed replacement. I, IN NO WAY, BLAME THEM SO PLEASE DON'T MISUNDERSTAND. THIS WAS A REPAIR THAT I ORDERED AND THEY SHOWED ME EVERY STEP OF PROGRESS, PROVING THAT THE WHOLE SYSTEM IS NEW NOW.

However, it was verified that the newly discovered rattle is in fact the variators, but I'm convinced that until the underlying cause is found, every variator I install will fail, or at least rattle.

So, now it's back to the drawing board. Call me crazy, but I'm starting with the accumulator.

I will repeat something I posted in 2015 "you can keep replacing your tires, or you can find the nail in your driveway."
 

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In closing, Silver Spur, I think your solution proves that there is in fact an oil supply/pressure issue that causes the rattling. The fact that my bushings were significantly worn, and are now brand new, proves that the bushing wear itself does not "cause" the rattling sound, however the rattling likely causes the wear on the bushings.

And, for the record, the rattling is very loud, just as it was before replacement. It didn't start as a muted rattle and progress over time, as it did in the beginning. Again, this suggests that the problem basically re-announced itself showing the same issue as before, regardless of having the new parts installed.

And finally, the underlying cause not being the variators would explain why some cars fail early and some don't, and why they both fail at the same time. I only suspect the accumulator because this is the behavior of failing accumulators in transmissions also. Some fail early, some don't. This could depend on use vs. age vs. who knows what. Totally different than a mechanical part that wears out from motion.

The jury is out on whether or not I found the problem as these are only my now educated guesses. We'll see.
 

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How does the the cam cap check valve mod come into this equation? Was this done on yours Erik?

(Just looked at that doc. It says 07 to 09 wet sump cars.)
 

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Discussion Starter #15
Erik , that’s awful but onwards we go
Re failures of both variators at the same time , that would be a hell of a coincidence that they both wore out at the exact same time .and yes I think I would have to look for a common connection to explain that .
Re service life on accumulators , there are two types commonly used in automotive applications , the spheres found on RR / Bentley , Citroen , MB etc contain a rubber diaphragm with high pressure nitrogen on one side , oil on the other , these do require replacement as the nitrogen pressure depletes .
Low pressure systems like the old 600 MB Grosser or the accusump systems use a spring and piston in a cylinder , the OE item on the maserati variators appears to be the spring and piston type and therefore would not have any expected service life .
When I checked mine it was not storing any pressure so I suspected a failed seal on the piston or perhaps a broken spring , I didn’t investigate any further .
I will look for an invoice showing the parts I used on my installation and if you want to PM me I can send you some photos , which you may post if you like ,
Ps . During my installation nothing was cut , no holes were drilled so it is totally reversible .
Good luck
Dave
 

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Erik , that’s awful but onwards we go
Re failures of both variators at the same time , that would be a hell of a coincidence that they both wore out at the exact same time .and yes I think I would have to look for a common connection to explain that .
Re service life on accumulators , there are two types commonly used in automotive applications , the spheres found on RR / Bentley , Citroen , MB etc contain a rubber diaphragm with high pressure nitrogen on one side , oil on the other , these do require replacement as the nitrogen pressure depletes .
Low pressure systems like the old 600 MB Grosser or the accusump systems use a spring and piston in a cylinder , the OE item on the maserati variators appears to be the spring and piston type and therefore would not have any expected service life .
When I checked mine it was not storing any pressure so I suspected a failed seal on the piston or perhaps a broken spring , I didn’t investigate any further .
I will look for an invoice showing the parts I used on my installation and if you want to PM me I can send you some photos , which you may post if you like ,
Ps . During my installation nothing was cut , no holes were drilled so it is totally reversible .
Good luck
Dave
Could you put it as a sticky?
 

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A great big FWIW, since I know I am butting in where I have no direct involvement with dry sump engines, but this thread reminds me of another one from long ago on the subject of oil pressure retention. So, I assume all on this thread are familiar with this one:

https://www.maseratilife.com/forums/coupe-spyder-gs/79457-cam-variator-oil-circuit.html

I love root cause analyses, but does the old thread suggest any potential workarounds that would keep the problem at bay until the root cause is discovered?

If not, please excuse the post.

KTBD
 

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Erik , that’s awful but onwards we go
Re failures of both variators at the same time , that would be a hell of a coincidence that they both wore out at the exact same time .and yes I think I would have to look for a common connection to explain that .
Re service life on accumulators , there are two types commonly used in automotive applications , the spheres found on RR / Bentley , Citroen , MB etc contain a rubber diaphragm with high pressure nitrogen on one side , oil on the other , these do require replacement as the nitrogen pressure depletes .
Low pressure systems like the old 600 MB Grosser or the accusump systems use a spring and piston in a cylinder , the OE item on the maserati variators appears to be the spring and piston type and therefore would not have any expected service life .
When I checked mine it was not storing any pressure so I suspected a failed seal on the piston or perhaps a broken spring , I didn’t investigate any further .
I will look for an invoice showing the parts I used on my installation and if you want to PM me I can send you some photos , which you may post if you like ,
Ps . During my installation nothing was cut , no holes were drilled so it is totally reversible .
Good luck
Dave
You are correct, this is a piston-type accumulator. The same design is used to store pressure in the F1 system. In the case of the F1 unit, it is widely understood that these accumulators start to slowly leak and cause frequent pump spooling due to it's decreasing ability to hold pressure. To your point, the rear-engine F cars use the bladder type and have a different characteristic failure, where they fail rather abruptly, unlike the piston units.

Assuming that the piston-type accumulators wear over time, as what is explained in the technical training manuals for the F1 systems that use them (QP, CC, Ferrari 612, Ferrari 599, etc.), then I would suspect that the same type unit would be exposed to the same amount of wear, if not more, mounted in the "V", where you have a high amount of engine heat.

So, hypothetically, if the variator accumulator did in fact fail in the same way as the F1 units do, slowly starting to bleed and failing to deliver adequate pressure to the VVT system, what would be the result? I'd say that it would begin to starve both banks of pressure and symptoms of rattling would start and evolve over time bilaterally. The rattling continues and eventually wears grooves in the bushings as seen in them when failed units are removed. If this were the case, and you replaced the variators, bushings, etc., I would think the symptoms would temporarily resolve until the lack of pressure begins, once again, to cause symptoms - a much quicker return of symptoms due to the fact that the accumulator is in a much more advanced stage of failure the second time around.

Again, this is purely theoretical, but this is what I suspected the first time (symptom wise) and it's exactly what happened to me.
 

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Discussion Starter #19
Erik , I agree 100% and after all is said I think you need a better oil supply, my installation uses the accusump ( a small one of about 1 liter capacity if I recall) to store oil under pressure when the engine is off, this is accomplished with an electric solenoid valve which closes with ignition off . When the ignition is on the valve opens and during the starter cranking period and oil is immediately supplied to both variators .
Once running the valve remains open and the accusump is recharged and will supply a reserve of oil under pressure as and when the variators require it .
I also fitted a ball valve tap at the outlet of the accusump so I could isolate it if ness but I have never used it . The other end of the accusump has a pressure gauge fitted if you want to watch what’s going on . I haven’t looked at it since the installation so can’t give you any details as to pressure but I do recall that it shows pressure at all times when cranking or running.
The whole thing is powered by a 12v ignition on feed from the fuse box to a relay beside the solenoid .
Dave
 

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One more important point:

With the dry sump units, the progression of the issue follows a certain "pattern," and I've been able to experience it over the past 4 years and 60k miles. In it's advanced stage, here is the issue:

The variators will make a very LOUD rattle on startup only under certain conditions. The engine must be shut off hot (i.e., after driving), and the car must sit in the sun for about an hour, then restarted in that environment. Cold, it's silent.

The failure started in 2014 (when I got the car) as a muted rattle - typically characteristic of a dry sump variator issue. In the early stages, and most common on these models, the wet sump failure is much louder than on the dry sump cars (I understand that the technology varies between the two, but I'm trying to demonstrate the difference between the sounds since everyone seems to recognize a wet sump variator rattle). However, once the problem matures on the dry sump cars, the CEL lights up and the noise gets very loud, especially when the car is "warm." Not "hot," but WARM. So, if you start it first thing in the morning, then it rattles for a few seconds. Drive for 30 min; park for an hour in the sun; then restart - you'll get a very loud rattle, more pronounced than a cold start rattle. It makes perfect sense that if the failure in fact was caused by a pressure supply issue, then the noise would be much louder on a warm startup with the oil being less viscous, thus causing more strain on the system trying to supply pressure.

Well, my theory is supported by my new symptoms. The initial cold start rattle is gone, due to the fact that the variators, seals, and bushings are new. The variators themselves are holding startup pressure. However, if you get the engine hot and leave it hot in the sun for an hour or two, it will rattle on startup very loud, just as it did before the install. If you let it sit overnight, then the oil viscosity returns and the rattle is gone once again.

The verdict is this:

The variators are working fine. They are holding pressure, advancing and retarding the timing as expected when the engine is running and holding adequate oil to supply the needed pressure on startup. There are no CEL messages, etc.

However, when the oil is hot and has just enough time to drain away, the variators become starved, at least temporarily of oil pressure. Coincidentally, a warm startup is when I believe the accumulator should be doing most of it's work. It should (I'm guessing, since all the Maserati techs I talk to seem to have a different variation of how this actually works) store the oil pressure for the variators when they need it, and it's proximity to them helps with this. The variators should need it the most during warm startups.

Now that I am running new variators and seals, but still have a pressure supply problem, the warm start rattle persists.

In summary, here is what I believe are the ultimate sources of necessary VVT pressure:

1. Cold start - pressure relies upon oil in the system (variator and bushing);
2. Warm start - more pressure is needed to compensate for lack of oil viscosity, This pressure is supplemented/stabilized by the variator accumulator;
3. Hot start - pressure remains high for a period of 30 minutes to (?) and depends on the age of both the variators and accumulator.

So, if during a warm start there is inadequate pressure in the accumulator, there will be a deficit in pressure reaching the variators for a few seconds, causing a rattle, regardless of the variator's ability to hold pressure.
 
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