VVT Tuning Noise - ADDED: Comparison Video

[AdrianG]

Originally Posted by SirBrass

Isn't oil pressure also measured by the ecu? I know oil & coolant temps are.

On phone I am. Therefore, if mistakes I make, Frank Oz blame you should.

No, there is no oil pressure sensor, just an on/off style sensor to make sure there IS oil pressure. It doesn't measure how much pressure there is, you'd have to add your own sensor.

[regal]

Originally Posted by AdrianG

No, there is no oil pressure sensor, just an on/off style sensor to make sure there IS oil pressure. It doesn't measure how much pressure there is, you'd have to add your own sensor.

And that's part of the problem we have no oil presuure logs for the FA20.


I found the spec on the filter, its 23 psi whichi is high, so this is probably pretty high volume pump. The next question is what is the oil pressure in the torque dip. Possibly the bypass valve is fluttering.


I doubt this is the issue by 4-5k rpm the pump shouldn't be held back by the bypass valve, but it would be interesting to know if the oil pressure in this rpm range has any affect on the noise.


It would also be interesting to know if this isn't a high flow oil pump like most Subaru's, or if they cheapened it out with a different part number. Anyone have parts digrams that can compare the FA20 oil pump to The FA20T?

[Sonolin]

So, TL;DR a healthy car should have this "dip" in fuel pressure as shown here, when going WOT. The dip should then rise, and level off. Healthy car:

Originally Posted by shiv@vishnu

...Here is a WOT run from ~1800rpm:

Otherwise, if your car is running unhealthy (which apparently would be a fuel pump issue), it will instead have a "wave" up & down of the fuel pressure.

Originally Posted by Element Tuning

Also, from what I understand, if D/I fuel pressure doesn't rise directly with VVT/Cam increase (like it does in pic #1), the tune should be modified.

Is that correct?

[regal]

Originally Posted by Sonolin

So, TL;DR a healthy car should have this "dip" in fuel pressure as shown here, when going WOT. The dip should then rise, and level off. Otherwise, if your car is running unhealthy (which apparently would be a fuel pump issue), it will instead have a "wave" up & down of the fuel pressure.

Is that correct?

There is nothing wrong with this DI pump graph imho. the vertical line is at 1900 rpm, by the time we get to the torque dip the fuel pump is stead as a rock.


I think some are afraid to back track their hypothesis after seeing the data.
I good engineer is never afraid to admit when he is wrong, part of step to finding the solution.


I was going to say we don't have a problem its just engine noise, but in the other forum there are quite a few broken camshafts with totaled engines.

[Sonolin]

Originally Posted by regal

There is nothing wrong with this DI pump graph imho. the vertical line is at 1900 rpm, by the time we get to the torque dip the fuel pump is stead as a rock.


I think some are afraid to back track their hypothesis after seeing the data.
I good engineer is never afraid to admit when he is wrong, part of step to finding the solution.


I was going to say we don't have a problem its just engine noise, but in the other forum there are quite a few broken camshafts with totaled engines.

Yes, I understand. But Element Tuning & others have said there's a fuel pressure "wave" in unhealthy running cars. (I said fuel pump, but that's probably the D/I right?)

I'm just trying to figure out how to diagnose that issue for sure that Element Tuning was referring to above (with the wavy fuel pressure line).

EDIT: Fixed my post should make more sense. I was just trying to summarize the thread.

[regal]

The "wavy" fuel pressure line really isn't wavy unless the sample rate was taken too slow, which I doubt fi pressures are high.


MHO we need to be looking elsewere. Maybe here :http://www.ft86club.com/forums/attac...0&d=1352490977




This is one of those TSB that is so difficult for the mechanic that they just check it off and hope the engine blows up

[andrew20195]

Originally Posted by DJCarbine

Found this, its got some more technical explainations

http://www.purcellperformance.com/Te...13%20FR-S).pdf

Specifically this passage



Sounds like its still hydraulically controlled with the addition of a detent for "locking"

There is actually a lot of good info in there if it is indeed accurate

Just found this thread today, and lots of good info here. I just wanted to clarify that while cam actuation is controlled by oil pressure, it is initiated by valve spring pressure. The spool valve controls the ability of oil to flow into and between the advance and retard chambers, but the oil is only there to hydraulically lock the cam adjuster.

From the Subaru Chain Driven Engines TRB:

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.

Subaru's service info is generally not well organized. Looking for info on the function of this system in the actual online service manual turns up information on how the EJ AVCS works, so...

[regal]

Originally Posted by andrew20195

. The spool valve controls the ability of oil to flow into and between the advance and retard chambers, but the oil is only there to hydraulically lock the cam adjuster.
.

Well thats good should mean that we aren't mechanically wearing out the cams from oil pressure. But this is all ultimately tied to the timing chain, I know the've gone back and forth on oil weight for that. Maybe Elelement is on to something. Synthetic Rotella may be may next oil change!

[Element Tuning]

Regal, The dip will occur when you drop the hammer at 1900 or you drop it at 3000 RPM but like you said it's not going to be an issue at high rpm because of how fast the cam is spinning at that point (more frequent pumping force). It's the rate of change in the cam timing at low RPM that causes this as the ECU has to deal with the sudden change in cam phasing when the lobes aren't spinning fast enough to prevent the pressure dip. It's normal for this car. I have proven this in my testing by turning off the cam advance.

The "wavy" fuel pressure data log is 12 hz which is same as the OFT and it's a known bad DI pump and had to be replaced. I posted this for people concerned with noise and this will tell you if you have normal noise or possible DI pump noise.

Originally Posted by Sonolin

Yes, I understand. But Element Tuning & others have said there's a fuel pressure "wave" in unhealthy running cars. (I said fuel pump, but that's probably the D/I right?)

I'm just trying to figure out how to diagnose that issue for sure that Element Tuning was referring to above (with the wavy fuel pressure line).

EDIT: Fixed my post should make more sense. I was just trying to summarize the thread.

Yes the "wavy" line is from a know bad DI pump car. This is why I'm showing it to people. The dip in the OFT logs and the 48hz log I provided are from a normally function DI pump.

So this is why you'll have one side of the fence saying there's no problem, the noise is normal and the other side of the fence saying, hey this sounds really bad it can't be normal. Log your DI and rule it one way or the other.

Overall we're loosing track here guys. LOL! The direct injection fuel pressure is not controlled by the variable cam timing, and it has nothing to do with oil pressure. The direct injection pump is controlled by the "Spill Valve" and in your EMS you can set the DI pump pressure target to whatever you want (at least in the Hydra) and then some fine tuning is required so when you set a target you actually hit it.

The variable cam sprockets from Subaru have always been spring loaded but it's not the valve springs that control your engine valves. Typically the waste oil from the cam sprocket is feed through oiling ports in the from of the camshaft and that oil is pushed through to lubricate the cam journals.

In terms of oil weight guys don't go crazy. If your NA and you don't race the car you could stick with a good 0-20w. Like someone mentioned any oil that is packed with moly or other additives will be better than your super emissions friendly 0-20w. If you are tracking the car we have seen 280F oil temps NA so you should step up the viscosity.

Turbo guys should really step up in viscosity if taking the car to the track. My car overall was quieter and everything with the thicker weight but keep in mind it was also a high end oil with a ton of "add pack."

I'll post and follow up with the "wavy" car and if I feel I need a 4 lobe driven DI pump I'll do it and either tell you it was a waste of money or I'll just keep a big ol secret.

[DJCarbine]

Originally Posted by andrew20195

Just found this thread today, and lots of good info here. I just wanted to clarify that while cam actuation is controlled by oil pressure, it is initiated by valve spring pressure. The spool valve controls the ability of oil to flow into and between the advance and retard chambers, but the oil is only there to hydraulically lock the cam adjuster.

Good info!

[regal]

Thanks elements for the back and forth. I think you've finally proven there are bad DI pumps. I asked toyota for DI pump pressure plots when the whole cricket thing first started. Maybe the cricket noise those of who have spent 20 years in a factory can't hear is a sign of wear. In general a pump making abnormal noises is wearing prematurely. Do they have a new revision yet that does wear out?

[Sonolin]

Thanks for the clarifaction @Element Tuning !!

[Element Tuning]

Originally Posted by regal

Thanks elements for the back and forth. I think you've finally proven there are bad DI pumps. I asked toyota for DI pump pressure plots when the whole cricket thing first started. Maybe the cricket noise those of who have spent 20 years in a factory can't hear is a sign of wear. In general a pump making abnormal noises is wearing prematurely. Do they have a new revision yet that does wear out?

I was told they are on maybe revision 3 but until I get the car back I won't won't able to see if there is a practical difference. I don't think it will get rid of the dip (which we've been able to tune around) as I think that is just what we're going to get with a 3 lobe pump at low RPM.

I had never heard the "crickets" until this particular car so I could never relate to what others were experiencing. These engines make so many strange noises from the cam rattle at start up to the EGR, to the injector clicking, its like an engine haunted house. LOL!

[andrew20195]

Originally Posted by Element Tuning

The variable cam sprockets from Subaru have always been spring loaded but it's not the valve springs that control your engine valves.

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.