# 1.8T VVT - Information



## Matt B (Apr 8, 2007)

So my understanding was that the VVT on the 1.8t was only used for start up. 
i.e., when its cold its on one position and as soon as it has warmed up it went to another, this was backed up by all the posts I had seen looking at the subject.

So last night I was reading the FrankenTT thread on vortex and some information about VVT was in page 5. I have blatantly cut and pasted this so I am not taking any credit for it, but I wasnt sure how many people go on vortex so I thought I would share:

"A big question I have wanted to tackle with this project is the Variable Valve Timing system. Most folks simply call it "VVT", and I want to know if the FrankenTT's ability to adjust the air intake cam might be handy for some bitchin power increases. So I started by rockin' the spectacles and doing a bit of reading on the subject. Two good sources of info on this are linked here:

http://www.vwforum.com/forums/f15/v-v-t-12044/
http://www.starracing.com/Cam%20Lobe%20 ... lained.htm

Next, I put the question to Chris Tapp at Eurodyne and he told me that he had indeed explored Variable Valve Timing tuning- and furthermore had control maps in his Maestro program. He also told me that the VVT system on cars from the factory is already a lot more active than most people realize. He said, "go log the intake cam timing positions and you'll see". So I did just that, grabbing logs from Block 091.

THERE ARE SOME LOGS HERE IN THE ORIGINAL THREAD

Whoa! The intake cam phase changes over the course of a 3rd gear pull! In the low and midrange it is altered 22 degrees for better volumetric efficiency, and then is restored to zero degrees for the upper power range. Makes sense, really. Just as explained in the links above, once the engine is moving rapidly, the intake valves can stay open later without having the induced air forced back out by the rising piston. So we've got a theory, and we're seeing it in practice. But does it work?

In Maestro's maps are controls for setting the window for the shift between overlapped and zero position. As a test I temporarily flashed the car two ways: locked at 22 degrees and locked again at zero. Taking the resulting airflows recorded we are able to identify the FrankenTT's "sweet spot" for transitioning the position.

We can see that the 22 degree intake cam phase position is good for improving volumetric efficiency down low: even with the intake valve opening "overlapped" into the exhaust cycle, the earlier closure nets improvement in airflow. But only to a point. Past approx. 4800rpm the zero position is more effective.

But what about boost? How does the VVT system impact turbo performance? Looking at the data from the same runs shows some interesting behavior:

Spool is better down low. So even with the intake valves opening early - and robbing the exhaust stream of pressure - the raised charge temperature and higher VE more than compensate. But what's going on up top with the fully retarded map? Boost is higher&#8230;yet airflows are lower. The turbo is pushing air, but it's not getting into the cylinders. Clearly, VE is really impaired by that 22 degree position at high engine speeds.

So the stock programming I originally logged in block 091 looks to be a good match for a stock forced induction system. The ECU's VVT maps were written for the little K04 currently in the car, and it looks like the VAG engineers hit it just about right."

So reading this has got me wondering, how active is the VVT in the various remaps people are running, for example do Revo, Custom Code etc utilise this function or is it just the same as it left the factory. Cue volunteers to log block 91 

Oh yeah and get over to the 1.8T forum on vortex and just read the technical discussion in the FrankenTT thread.  [smiley=book2.gif]


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## V6RUL (May 28, 2009)

Unitronic have included VVT variables on my map as i have the 22 and 52 degree cam change ability, numbers were worked out on their mule.
Steve


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## Matt B (Apr 8, 2007)

V6RUL said:


> Unitronic have included VVT variables on my map as i have the 22 and 52 degree cam change ability, numbers were worked out on their mule.
> Steve


Nice one Steve, I thought that nobody was interested in my post. I have one response yaaayy.
I am interested in this subject, I remember a lot of fuss about JBS using some VVT attack maps and people saying they lost power. 
As soon as I get a nice day I am going to log block 91 and have a look what Revo stg 3 does with the cam position.


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## jamman (May 6, 2002)

I'd read it Matt but didn't want to comment because you would be nagging me to go out logging for you AGAIN :wink:


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## Matt B (Apr 8, 2007)

jamman said:


> I'd read it Matt but didn't want to comment because you would be nagging me to go out logging for you AGAIN :wink:


Block 91 James


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## Charlie (Dec 15, 2006)

Matt B said:


> jamman said:
> 
> 
> > I'd read it Matt but didn't want to comment because you would be nagging me to go out logging for you AGAIN :wink:
> ...


^^NOW you little muntpig :lol: xx

Charlie


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