NefMoto

Hi!

Haven't found topics with my answers, so I am making new one.
I am interested how variable valve timing works on 2.7T.
As I understand on 1.8T there are only 2 positions. 0degrees - no advance and 22 degrees advance for better spool up and performance. Found also map on 1.8T, but can't find it in 2.7 file. in damos: NWWUE
From this graph I understand that there is more than 2 positions.

(http://i97.photobucket.com/albums/l214/boomerw/Screenshot2012-06-27at80704AM.png)

Anybody can explain how it works on 2.7T

Same as 1.8t. There are only 2 positions, advanced and not-advanced. VVT has little effect on k03, but does have more effect on k04 and up. RS4 is different from S4 as it has bank independent control.

How do you see more than 2 positions from that graph?

what do you mean by bank independent control?
I don't understand this graph. I thouhgt that grey area is advance degrees. And it is changing depending on RPM. How do you understand this graph?
For example If I install better intake camshaft and want to tune this timing, what I need to search for?

Meaning, on the S4 the solenoids are controlled in unison with a shared pin on the ECU. In RS4, each bank has its own ECU pin, thus independent.

The domain axis of the graph is RPM and the range says load, but I suspect it is requested torque, so the VVT is only active at high load from 1k-4k RPM. The map you need to look for to tune this is KFNWSE, although there are a multitude of NWS maps.

Hope this helps.  ;)

great! That is what I wanted to know! Thanks.

From my experience (little) on k03 vvt is useless and decrease performance and boost....

It is load.

Also, KFNWSE doesn't exist in ME7.1.

You want to look at the Alpha FR for this.

Right, so it's just KFNW for 2.7 then?

Yes. As far as I can tell.

Also KFNWWL (for warmup)

Its pretty straight forward, you want to advance the cam as you start to spool and keep it advanced until just after peak tq and the load settles, keep it in for a few hundred rpm and then let it shut back down towards redline.  On the ko3 (stock) setup it shuts off so soon because as the rpm climbs the turbines become very restrictive and that overlap isnt beneficial.

On a big turbo with a low turbine inlet pressure (tip) you can run it out much further.  Personally on my big single I come on with it around a measured load of 80 at like 3200 rpm and it stays on to about 5800 rpms, being fully switched off by 6100-6200

Something I never see mentioned is the time in which the solenoid needs to transition, it isnt instantaneous.  You will need to play around with this to get it right.

The way i tune VVT is to turn it off completely at all points, go and do a few pulls in various gears.  Then i turn it on completely (I wont run it over 7000 just for safety sake) and do the same pulls over again.  Then I over lay the maps to see whats is what.  The non advanced pulls will be laggier with a softer tq peak but stay level on  power up top.  The fully advanced pulls will spool faster but lose some power up top.  This paints the clear picture of where its beneficial to be on vs off and you can set your maps accordingly.

I have tuned a few cars where I ended up having it come on, then off, then back on and back off for a short period up high in the rpms.  Every setup will be different in what is going to maximize power.  Port sizes, turbo sizes, manifold types and even wastegate type can all influence a given system and how it behaves with the VVT.

Interesting, thanks for sharing your experiences.  I'm looking forward to playing with this once I have all the other areas of my tune ironed out.

very intesting info , thanks to all for share it , i was finding info about of vvt for 1.8t  Me 7.5 , this help me so much

Very informative. I am leery about having the intake advanced though up to 7k on test runs... are these WOT?  I assume they are...

Trooper, how do you fine tune timing for each VVT state with tuning method above?

yes, this is all for WOT and i agree, its sketches me out having it on over 7k.  none of us really have any business running it over 6500

I more or less flatline timing to what i know works on a given boost/fuel for this process and then after I figure out where the VVT is good for a car i tune the timing to get even better spool and more consistent power up top.

What is the logic in doing it seperately?

Good information.   I was just looking into tuning nws on 2.8l n/a heads and cams. I'd be very surprised if any of the factory S4, RS4, or n/a maps are optimal for this cam being used in a boosted motor.     

Anyone have any experimental data with these cams yet?   I'm willing to give it a try over the next couple weeks.

There is one slightly simpler thing you can also do.
Not as good as measuring both positions on the dyno, but it works quite well in my experience.

Dial in the cam switch, do a pull. Note load (rl_w) at the switch point.

If:
* load before the switch point was higher, and it gets lower after the switch point, then your switch point is too early;
* load before the switch point was lower, and it gets higher after the switch point, then your switch point is too late;
* load remains flat, then your switch point is in the right spot.

As an alternative to measuring load, you can measure acceleration (delta speed vs time) and do it that way, but I have found that usually looking at rl_w gives good results.

Just a one thing at a time sort of process, how I like to work.  Now that I have more experience with it I kinda know what will work for me and do set the timing up close to the end goal and then do the vvt, but I always then go back and clean it up after the vvt is dialed.

Hey, its just how your ecu is labeling it really.

on some it is 1 for on, 0 for off.  Look at the high numbers as on and the low numbers as off.  I understand it as that 18 equals 18 degrees advanced so that is on.  tune accordingly.

Do any of you have/use any tools to tune the timing, maybe something like the FKKVS fixer but instead of logging injection time, RPM and short term fuel trims like for the FKKVS, maybe it uses the logged RPM, load, and timing correction to suggest changes to the timing table?  Maybe the sheet would use an algorithm to suggest timing changes, as timing corrections are not necessarily strictly instantaneous and are  affected by what happened leading up to that specific load/RPM cell.  Just thinking out loud, as something like this with an iterative refinement could really help with the fine tuning.

Interesting approach...

Based on this system what would you make of my load profile shown below... the switch point is 5000 RPM ON to 5500 OFF

(http://i1357.photobucket.com/albums/q755/britishturbo/cam_Switch_load_zpsf540fa13.png)

Looks like you get load drop so extend advance by 250-500 rpms and see where that gets you...

Log cam advance.  Overlay with load.  Adjust. :P

That would be wnwi_w and wnwi2_w correct?
Good thinking... see where it really is not where it's supposed to be lol

Hard to say for sure with boost dropping right there too... I'll log actual position as ST suggested and post again :-)

Lock the cam state at no advance

Tune KFZW

Lock at full advance

Tune KFZW2

Overlay load from both and it will be clear

Keep in mind as ST said that it takes a few hundred RPM to adjust

Good plan. I had thought about locking in each state before but hadn't planned on tuning the timing for each while there.

Wash and repeat style works best for me.  Maybe 3 times back and forth to get all hidden potential.

So is anyone worried about running the cam at max advance at high RPMs?

No. unless you believe that crap Max says lol :-p

But no unless your valves float of things expand a crap ton from heat the clearance is the clearance.

I understand that, but not everyone has a fully built top end Lee (fucker). As such, I'd be leary of running 7k+RPM at max advance. Just curious :)

but since full advance is unsafe past a certain RPM, dont lock it past that?

Haha fair enough. I forget not everyone has an 8500 redline :-)

Its perfectly safe unless you float a valve.

I dunno. I wouldn't do it on a stock valvetrain, or at HIGH boost. Could float/blow a valve open. I'm with Nyet.

Are we mixing up advance and retard here?

+18* overlap angle or fnwue 0 = advanced position aka the normal state, linked with KFZW.

-4* overlap angle or fnwue 1 = retarded position, linked with KFZW2.

err. yea. what he said.

speaking of floating valves..not really.. http://youtu.be/P3HwJDxgLUU I dunno if the valves are stock but they appear to be. the ones I bent looked like the ones in the vid.

Nope.

fnwue == 0 == retarded

KFNW output 0 clears B_nwsb, clears B_nws, and doesn't energize N205/208.

When B_nws is clear, then fnwue = 0.

Normal state is no overlap.

Huurgh. I think phila has it right.

First you say fnwue 0 = retard, and then normal state is advanced? :D

I think we need to bone out what is an retarded vs. advanced cam operational angle.

Phila said it just how it is.

Normal state = No Advance = No Overlap = KFZW = 0 in KFNW
Advanced State = Overlap = KFZW2 = 1 in KFNW

So timing a cam later in the cycle is advancing it? The opposite of ignition timing?

Here's a stock KFNW table from a 2.7 M Box:

(http://i1357.photobucket.com/albums/q755/britishturbo/kfnw_zps1f213fa3.png)

Where you see 1 the cam is advanced - overlapped
Where you see 0 the cam is normal (retarded) - no overlap

Some suggest to advance the cam for longer int he rpm range to try and increase spool.

One thing I want to warn about though... in my log I did yesterday even though I set it to advance the cam until 5500 the logs showed it stayed advanced all the way to 6800

I'm confused about this as well.

Retarding the exhaust valve increases overlap.
Advancing the intake valve increases overlap.

if "advance" means "increase overlap" i'd say something is wrong with using the word "advance", unless by "advance" you mean "advance the timing of the intake with respect to the exhaust by retarding the exhaust, assuming the intake timing remains the same"

The Exhaust cam does not move... the Intake cam gets Advanced.

IF you look at a 2.7 the timing belt drives the outside cams - the exhaust cams.

Whoa. No wonder I was confused.

Thanks. Now everything is clear.

I have a question related to selective valvetrain upgrades.

Long story short I ended up with stock valvetrain with upgraded exhaust springs.

I understand the the first thing to catastrophically go are exhaust valves if you over-rev as they start floating at kiss piston or intake valves. If intake valve floats as well, it will only cause loss of power since some of the charge will escape back into manifold but the valve should close far before the ingnition takes place so "no big deal". The engine will just hit proverbial wall and driver will definitely feel that.

Considering the above upgrade, how much, do you recon, I extended my RPMs by doing just exhaust valves?


Thanks!

Can you also please also post your KFNW with axis labels?
KFNWWL, KFPBRK, KFPBRKNW, KFPRG, & KFURL too if you have time.

My recommendation here is to keep your "stock" max rev limit because even though you upgraded the exhaust valve springs you are limited by the stock intake springs, bottom line. Is a few extra hundred rpm (maybe that much) really worth being on the verge of catastrophic failure? If valves are floating, no matter which(intake/exhaust) it is bad news as there are no advantages to floating valves and we all know there are way high chances of collision.
 In my opinion you either should have saved some money and replaced the exhaust valve springs with OEM replacements or spent more and purchased a good set of both intake and exhaust springs.

So it is called advanced when inducing more overlap because it is the exhaust cam that is the driven?

Advancing in relation to cam drive and not engine cycle.

The timing relationship between the crankshaft and exhaust cam doesn't change because the timing belt is positively tensioned at all times (idealy) The "slack" in the chain between the exhaust cam and intake cam is tension controlled by the solenoid which is also "powered" hydraulically by engine oil pressure. It gets the signals from the ECU via pulse width modulation. When its powered, the cam advances as such that the valves open sooner because the solenoid tensions the chain which rolls the cam "forward" more so then if the chain has slack.

I have a 100% understanding how the VVT works, I am just not comfortable with the terminology of the cam states.

You like me also describe the cam as advanced when opening the valves sooner, but is this thread they describe the cam timing as retarded when opening earlier in the cycle. Hence my question if the cam state is concidered retarded in relation to the driven cam, the exhaust cam, and not in relation to the combustion cycle(opposite of ignition timing terminology).

I don't understand the disconnect happening here...  The cam, when the actuator is active is advanced forward from its normal state.  Normally the intake valves are still 100% shut when the exhaust valves are still opened.  This advance we create makes the intake valves open sooner while the exhaust valves are still open, hence the term that they are advanced.  This overlap makes it so that boost pushes through the cyl and gives the exhaust a little bump.  Thus the reason why with tiny turbos where the exhaust side has way more pressure than the cold side the flow will actually go backwards in the upper rpms.

The VVT only changes from a "normal" state to an advanced state. So maybe what they are talking about is when the VVT reverts back to it's normal state which, is technically retarding the timing. But this makes it confusing. It's just either normal or advanced!
With ignition timing, when using the term "advanced" means the spark/ignition/combustion/whatever is happening sooner(farther BTDC on the compression stroke). So if combustion is happening at -6 degrees BTDC, a more advanced ignition timing would be for example: -6.1 degrees BTDC or anything after -6 degrees on the compression stroke.

BTDC is Before Top Dead Centre so a negative value would be after top dead centre so -6.1 BTDC is retarded compared to -6 BTDC.

Normal state (retarded) the intake valves open ATDC.

Advanced state the intake valves open BTDC.

What's the confusion?

Sorry for the confusion. I should either have taken the "B" away from TDC or taken the minus signs out.

what is the equivalelnt of KFNW for ME7.5? couldnt locate this map on ME7.5...

Im thinking KFNWSE but not sure

Also, does this KFNWSE looks ok? (stock)

Yes, KFNWSE.  Sorry, don't know if it's set up correctly for you though.

It took a bit longer to start on this due to some fueling hardware issues, but this week, I took a couple of steps into vvt tuning on my RS6R car with 2.8 Heads and Cams.   I started by zero-ing out KFNW.  The car felt slower, and boost built much slower.

So I went the other direction and added the RS4 K-box KFNW values and rpm axis (cam change-over around 5200 rpm) and this is what I got:  Acceleration increased, boost hit harder, and you can see in the graph that even though actual boost is flat, at the switching point and a bit beyond, load is decreased.   It appears that some overlap is having a positive effect at the switch over point.

Resolution is low, so I attached the log as well.
Green is Desired Boost
Red is Load Acual
Purple is Boost Actual

(http://img7.imageshack.us/img7/6830/l47.png) (http://imageshack.us/photo/my-images/7/l47.png/)

I'm a bit scared to keep the cams advanced much higher in the rev range, but hell, if it keeps making more power, then why not?   Well,

my thoughts on one side are, in theory, so long as the belt and chains are attached, it shouldn't matter how quick the motor is spinning.   If the valve has not moved into the path of the piston at 4000 rpm, then it shouldn't at 6000 rpm either, right?
 
On the other hand, the 2.8 NA intake cams overlap the exhaust valves longer to begin with and with an additional 20* of advance, it seems like if there was going to be one of the three (RS4, S4, 2.8) that may have a problem, this would be it.

Any other thoughts?   Am I interpreting the graph correctly?

I looked up a Passat 2.8L ATQ file today and found KFNW and KFNWWL maps to compare with RS4 K-box since ATQ heads are what I am running.  

Interesting to note the NA cam angle strategy is nearly the opposite as the S4 and RS4.  Note also that cam switch back to normal position takes place at the same RPM as the S4.  Was audi concerned about smacking an intake valve at high RPM in this file as well?  Now what about the warm-up vvt map for the RS4.   Shows that Audi had no issues running the cams advanced through redline with the RS4 cams.

(http://img593.imageshack.us/img593/728/x4w7.jpg) (http://imageshack.us/photo/my-images/593/x4w7.jpg/)

Has anyone else rapped out an NA heads/cams car with the cams advanced through the rev range?



 

If you didn't flatten out the changeover maps, you're going to have trouble distinguishing "more power" from "ME7 is doing stuff (calc load different, req boost different) because the cam angle changed"

http://s4wiki.com/wiki/Tuning#Cam_changeover_effect_on_requested_boost