VVT Tuning Noise - ADDED: Comparison Video

[1Cor10:23]

@Element Tuning the log that you posted with 'waves' - was the DI issue from failed seals or a different DI issue? Wondering what the latest on seals are as it's giving me some concern regarding tracking this summer.

[regal]

Originally Posted by andrew20195

This describes the previous AVCS system. The AVCS on the chain motors does not have high pressure springs internal to the cam sprockets. It uses valve spring pressure. This is probably one of the reasons why they've been having issues setting cam codes, as many of them are set when the intake cam gets stuck advanced due to design flaws with the early sprockets.

Well that sucks, was there a part number or casting number change?

[andrew20195]

Originally Posted by regal

Well that sucks, was there a part number or casting number change?

Not sure on that, but it's generally on cars manufactured before July 2012, when the countermeasure went into production.

[Element Tuning]

Originally Posted by 1Cor10:23

@Element Tuning the log that you posted with 'waves' - was the DI issue from failed seals or a different DI issue? Wondering what the latest on seals are as it's giving me some concern regarding tracking this summer.

It was from a DI pump with the "crickets" sounds and I could here it struggling with the OEM tune at AVCS onset. I suspect this was the standard failure as the car still ran and would hold decent pressure at high RPM.

Originally Posted by regal

Well that sucks, was there a part number or casting number change?

Sorry I don't know as the tech had told my customer that this was the third different revision or part number that he had to install.

[OrbitalEllipses]

Originally Posted by Element Tuning

Sorry I don't know as the tech had told my customer that this was the third different revision or part number that he had to install.

If there's a superseded P/N any number of Subaru (or Toyota) techs we have kicking around on the forum would be able to provide that knowledge. So let's get a few into this thread?

[Element Tuning]

Originally Posted by andrew20195

This describes the previous AVCS system. The AVCS on the chain motors does not have high pressure springs internal to the cam sprockets. It uses valve spring pressure. This is probably one of the reasons why they've been having issues setting cam codes, as many of them are set when the intake cam gets stuck advanced due to design flaws with the early sprockets.

I think you're misinterpreting the technical document as it does not use the "engine valve springs." They are talking about the spring in the "spool valve." There are actually a number of springs in the variable cam timing mechanism of the FA20.



What is unique to this over the EJ is the ability to "lock" the cam in place and as we've seen with tuning you have both advance and retard of the cam unlike the EJ which can only advance from the centerline.

Hope that helps.

Thanks,
Phil Grabow

[andrew20195]

Originally Posted by Element Tuning

I think you're misinterpreting the technical document as it does not use the "engine valve springs." They are talking about the spring in the "spool valve." There are actually a number of springs in the variable cam timing mechanism of the FA20.

I'm quoting directly from the Subaru Technician Reference Booklet on the chain driven engines. Like I said, it's the only source I can find with this info, but seeing as how closely Subaru engineers are involved in technical training, I'd be surprised if they got it wrong.

From my earlier post:

The new system does not depend on a hydraulic rotor to function. Instead oil is moved from
one chamber to the other which reduces the volume of oil needed to operate the AVCS.

and

A spool valve pressed into the Camshaft rotor controls the oil flow into and out of the Advance
and Retard chambers. The force needed to rotate the Camshaft within the Camshaft sprocket
is delivered by the valve springs.
The oil in the sealed chambers holds the Camshaft rotor into a fixed position. If oil is transferred
from one chamber to the other, the Camshaft rotor and Camshaft rotate within the Camshaft
sprocket.

All the springs shown in the Toyota document appear to be check valves from what I can see.

[Element Tuning]

You do see the FRS document picture I've attached with the "Advance Hydraulic Chamber" and the "Retard Hydraulic Chamber" right? I've attached another image showing the structure of the hydraulic chambers.




I'm not making this up and I happen to have both the intake and exhaust cams and actuators sitting on my desk It uses hydraulics but unlike the older AVCS is has separate chambers for Advance and Retard which is really sweet!

Those are the facts, let's move on

[regal]

Originally Posted by Element Tuning

You do see the FRS document picture I've attached with the "Advance Hydraulic Chamber" and the "Retard Hydraulic Chamber" right? I've attached another image showing the structure of the hydraulic chambers.




I'm not making this up and I happen to have both the intake and exhaust cams and actuators sitting on my desk It uses hydraulics but unlike the older AVCS is has separate chambers for Advance and Retard which is really sweet!

Those are the facts, let's move on

For those of us out in he skicks I don't think the localish Scion dealership will have a cue, just insist on new heads if something is wrong?

[arghx7]

I know the AVCS is not totally on topic, but just for clarification before we move on:



These systems are called "cam torque" activated, but they still use oil as a control mechanism (see attached paper). As the cam hits the bucket (in Ford's implementation) or the roller finger follower (Subaru), the force makes the oil slosh inside the chambers. The spool valve is there to coordinate that sloshing in a controlled way.

In a conventional AVCS system, the oil is basically forced by hydraulic pressure to phase the cam. The source of energy is ultimately the oil pump. With this system, the oil is a way of transferring the force of the cam by sloshing in the desired direction at the right time.

The intermediate locking position, which I didn't realize the FA20 was using, is a cold start emissions countermeasure, especially for meeting 2013 model year MSAT regulations of HC/NMOG at 20F/-7C testing. Aisin also uses that type of technology for Nissan applications. By dialing in overlap during cranking you get reburn of HC emissions that normally would have been thrown out the exhaust and unconverted.



The above image compares running no intake cam advace, versus hydraulically moving the cam at startup, versus having an intermediate lockpin with no delay.

[calmtigers]

So in plain english, have we come to a consensus if the OFT/Perrin noise is detrimental to the life of the engine?

I've read the entire thread but got lost pretty quickly in the technical language!

[wbradley]

Originally Posted by calmtigers

So in plain english, have we come to a consensus if the OFT/Perrin noise is detrimental to the life of the engine?

I've read the entire thread but got lost pretty quickly in the technical language!

Very unlikely detrimental. But some possibility it will reveal a weakness in the fuel systems ability to maintain constant pressure at throttle tip-in. Nothing to worry about.

[wparsons]

IMO, it sounds like the bad noise might be the sound of a DI pump wearing out, but is more likely to annoy you than actually accelerate pump failure.

[kiichiro]

Having logged a cumulative 65,000 test miles on Perrin tunage I can only say that there is no likelihood of damage from the VVT or tune settings