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Old 02-28-2014, 01:24 PM   #1
Dezoris
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VVT Tuning Noise - ADDED: Comparison Video

THE ISSUE:
I have heard this is multiple tunes, including the Perrin, Vish, and Visconti.
Vish explained it's simply a large change in VVT timing in a small amount of RPMs. (5 to 40 degrees)

I'd like more technical information on what exactly is creating the noise. Perrin said its resonance, Vish said its "rasp." Sounds like shit, and like valvetrain noise to me. With all of the tuning drama recently...

I'd like a straight answer as to mechanically what is happening, because if the long term effects of reducing torque dip has mechanical implications I want the VVT timing cut back.

SOUNDS OF THE MODIFIED VVT TUNING TO REDUCE TORQUE DIP
Here are the logs to accompany the video:





New comparison video, stock VVT map vs aggressive VVT tune:





Noise can be heard here Perrin Tune: at time -31.00 and -23.00

http://www.freesound.org/people/dezoris/sounds/191194/



And here on Vish dyno: At 22 Seconds


At 22 Seconds


UPDATE: 3/11


Perrin modified my flash file to go back to a stockish VVT map from 2800-4200RPM range. After the flash the valve train noise is now gone.

The argument remains, tuners say the noise introduced from the optimal/aggressive VVT tuning is normal. Tuning VVT agressively can be done on FI or NA the same way, depends on the motor on how much noise it generates.

Given the unproven long term mechanical implications of those statements (if any) going back to a conservative VVT setting is good insurance for now.

Last edited by Dezoris; 03-16-2014 at 01:15 AM.
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Old 02-28-2014, 01:33 PM   #2
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There is no mechanical implication of running optimal VVT timing to minimize torque dip. If it's not something you want, just get a UEL header and run an appropriate UEL tune. Noise and dip gone.
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Old 02-28-2014, 01:48 PM   #3
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Quote:
Originally Posted by shiv@vishnu View Post
There is no mechanical implication of running optimal VVT timing to minimize torque dip. If it's not something you want, just get a UEL header and run an appropriate UEL tune. Noise and dip gone.

I can second that first-hand. On the stage1 tune there was always rasp during that time. Since I've installed the header and moved to the stage2 tune.. there is no dip and no noise... but it is replaced with - oh sh!t this thing is moving!!!

The header is beautiful sounding in fact - can't help but run it through the gears every time to 5K or so... )

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Old 02-28-2014, 02:18 PM   #4
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The VVT on this engine just changes the set angle of the camshaft itself. It doesn't create any extra lift and the duration of the valve opening remains the same therefore there is no extra stresses put on the valvetrain itself.


You have to remember that on the stock maps, the AVCS system is going through most of the range of the system anyway. What's the cause of the noise is the cam angle opening in relation to set events, perhaps extra overlap is causing it or earlier opening of the valve.
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Old 02-28-2014, 05:28 PM   #5
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@shiv@vishnu
@Kodename47


So the extra overlap is causing a metallic sound in relation to set events such as what?

Shiv, a header, loss of O2 and a re-tune is not worth the cost to get rid of a metallic sound from cams due to the way the VVT is tuned.

I am not trying to be difficult but lets face it if you are capable of making changes to angles of VVT and other settings you should be able to completely explain why it is creating a mechanical sound.

Can you reduce the amount of angle change in tuning to eliminate the mechanical noise caused by trying to smooth out the tq dip?

I am looking for a more complete explanation of what really is happening to cause the metallic noise, not just hey, its ok.

Heard this from other tuners before, back it up.
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Old 02-28-2014, 06:07 PM   #6
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I was wondering why at around 4krpm on a tuned stock exhaust car (mine), I was feeling and hearing shudder (is probably rasp) at WOT which would then disappear. Doesn't appear at partial throttle, or WOT in 6th, just 3rd of 4th. Probably b/c of the speed at which the revs are changing.
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Old 02-28-2014, 06:36 PM   #7
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Quote:
Originally Posted by Dezoris View Post
@shiv@vishnu
@Kodename47


So the extra overlap is causing a metallic sound in relation to set events such as what?

Shiv, a header, loss of O2 and a re-tune is not worth the cost to get rid of a metallic sound from cams due to the way the VVT is tuned.

I am not trying to be difficult but lets face it if you are capable of making changes to angles of VVT and other settings you should be able to completely explain why it is creating a mechanical sound.

Can you reduce the amount of angle change in tuning to eliminate the mechanical noise caused by trying to smooth out the tq dip?

I am looking for a more complete explanation of what really is happening to cause the metallic noise, not just hey, its ok.

Heard this from other tuners before, back it up.
Have a look at this thread: http://www.ft86club.com/forums/showthread.php?t=57662

I've compared stock to the OFT tune. My guess is it's some form of resonance. Increasing overlap or changing the cam timing will have an effect on the way the air moves and in/out and around the cylinder.

Of course you could change the timing to get rid of the noise but you'd lose The power gained. I'm sure a compromise can be made though.
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Old 02-28-2014, 06:46 PM   #8
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Answer: VTEC
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Old 02-28-2014, 06:48 PM   #9
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Quote:
Originally Posted by Kodename47 View Post
Have a look at this thread: http://www.ft86club.com/forums/showthread.php?t=57662

I've compared stock to the OFT tune. My guess is it's some form of resonance. Increasing overlap or changing the cam timing will have an effect on the way the air moves and in/out and around the cylinder.

Of course you could change the timing to get rid of the noise but you'd lose The power gained. I'm sure a compromise can be made though.
This is by far the most detailed explanation I have seen thank you.
I would like to see how many degrees it needs to be reduced to eliminate the sound and the resulting power drop. I'd rather have a power drop than an unexplained metallic resonance.


It's not an air charge sound, or tone sounds like marbles getting ground up in valve train. It maybe old school but if it don't sound right then it probably isn't.
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Old 02-28-2014, 06:57 PM   #10
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I don't agree with with the description of "metallic" noise. It's not metallic. People who describe it as such probably have never heard a real metallic engine noise before

It's just induction/valvetrain noise. You hear it in all NA engines to and extent. You hear it clear as day in VTEC honda motor just before the secondary cam kicks in. Personally, I don't even hear it unless I pay attention to it. However, I can hear a knock with the radio on, in the middle of a conversation. I guess I'm just more sensitive to things that unfriendly to engines.
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Old 02-28-2014, 09:05 PM   #11
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Quote:
Originally Posted by Dezoris View Post
I have heard this is multiple tunes, including the Perrin, Vish, and Visconti.
Vish explained it's simply a large change in VVT timing in a small amount of RPMs. (15 to 40 degrees)
Although I can't offer a technical answer or reason for it, I did note that the exact same noise is audible in the stock ROM just as torque comes back from the dip at ~4500rpm. The only difference is that it is quite brief in comparison to the tuned ROM's which change the cam timing significantly well before that RPM.
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Old 02-28-2014, 09:52 PM   #12
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Quote:
Originally Posted by shiv@vishnu View Post
I don't agree with with the description of "metallic" noise. It's not metallic. People who describe it as such probably have never heard a real metallic engine noise before

It's just induction/valvetrain noise. You hear it in all NA engines to and extent. You hear it clear as day in VTEC honda motor just before the secondary cam kicks in. Personally, I don't even hear it unless I pay attention to it. However, I can hear a knock with the radio on, in the middle of a conversation. I guess I'm just more sensitive to things that unfriendly to engines.
Let me throw this out here, I am not saying there is something wrong.
This motor and countless tunes are quiet during the overlap phase.
Why does pushing the angle change so far create "valvetrain" noise?
Because it is audible on the street, inside the cabin all the time.

If you back off the VVT angle the chatter goes away.

The angle change you are introducing is creating the noise, it's not something "typical."

I am not looking for a generic answer here.
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Old 02-28-2014, 10:51 PM   #13
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Quote:
Originally Posted by Dezoris View Post
Let me throw this out here, I am not saying there is something wrong.
This motor and countless tunes are quiet during the overlap phase.
Why does pushing the angle change so far create "valvetrain" noise?
Because it is audible on the street, inside the cabin all the time.

If you back off the VVT angle the chatter goes away.

The angle change you are introducing is creating the noise, it's not something "typical."

I am not looking for a generic answer here.
You know what I know
You and I can't deny it

It does not sound right
Yes, same sounds

Some of my tunes cause more noise than others.
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Old 02-28-2014, 10:55 PM   #14
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I don't know exactly what's going on here, but I can at least post about a few things that I've had some experience with. I'm not an NVH expert but I've had some exposure to it on a system design level and on an experimental/testing/optimization level. So I can suggest, for academic purposes at least, an experimental way to approach the issue.

So we know that exhaust makes noise, motor mounts and loose objects make noise, that kind of thing. The main things that are specific to a modern n/a DI engine are:

1) sound of the direct injection solenoid valves
2) sound of the high pressure fuel pump and fuel pulsation
3) sound of the hydraulic lash adjusters and valvetrain

There are a lot of things that affect engine NVH on a modern direct injected engine, but you can't figure out a root cause on a transient WOT from a chassis dyno like that. What you really need to do is put the engine into an NVH lab engine dyno. First thing I would do is motor the engine in 200rpm increments. Now what the hell does that mean?

Does this noise occur when the engine is actually firing, from a combustion event, or can you hear it when it's just spinning (like on a decel in the vehicle)? An electric motoring dyno bolts to the flywheel and spins the engine up and down to hold a speed. The engine doesn't have to run, but you can communicate with a prototype ECU in realtime and start commanding different AVCS positions. The beauty of that is that you can isolate whether the noise is coming from some valvetrain issue or fuel system issue without any combustion occurring. This is important because the pressure rise characteristics have a huge effect on engine NVH, especially on DI gas engines and diesels. Faster pressure rise=more noise, and that's one of the reasons why diesels are so loud.

So first I would motor the engine and see if I can audibly hear the sound, and see what my NVH instrumentation can pick up at the same time. Figure out the frequency and order of the noise in a motoring condition. Perform cam phasing sweeps at each steady-state rpm point and record data with different levels of intake and exhaust phasing. Generate plots of cam phasing vs various noise parameters (decibals, frequency, etc). Then repeat the test with the engine firing--actually run the engine at full load. See what the influence of combustion would be, and also perform cam phasing sweeps and fuel pressure sweeps to see what the influence of the high pressure fuel pump is.

Finally, I would feed that information to a simulation specialist who can do finite element analysis and figure out what the heck is making the noise. NVH simulations make little nifty animations that show the stress and strain on various engine components under different conditions, and can assess potential NVH. Then from all that work devise a countermeasure with hardware (motor mount, special engine cover, etc).

If a hardware countermeasure is not possible, look at your cam phasing sweeps, look at your NVH data, and determine what is an unacceptable level of NVH. Figure out which set of engine parameters fall create the unacceptable level of NVH. Weigh that versus engine performance and combustion data, and make a judgment to create a calibration-based NVH countermeasure in lieu of a hardware change.

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