NefMoto

On my tt from the factory it had variable cam timing. Supposedly only for cold start emissions. I've read a post elsewhere where someone had dug further into it and found that the cam timing changes during a pull. Two different positions I guess.  Well I swapped to a aeb head from the stock awp and I kept with the NON vct tensioner. Now that I have aftermarket cams coming in...   should I stick with the aeb tensioner and tune it out or should I go back to the awp with vct?  Googling hasn't learned me much in the 1.8t world and mixing performance cams with vct.

i ran a set of cat 3651's in aeb head with no vvt. had to raise idle speed a bit with lemmiwinks to smooth it out. this was back in 2006 maybe? no diy tuning then.

AFAIK all aftermarket camshafts for 1.8T could be only used without VVT or at least all manufacturers claims so!

Ok yea. That seems to make sense. I'll have to figure out how to tune out the vct.

The cam timing varies depending on engine load and RPM. It is not just for cold start up emissions, but it does function to provide a lot of overlap for fast cat warm up in addition to the torque increasing function.  The VVT has better low speed torque and some gain at the top end too. It is illogical for Audi to use the VVT for only cold start up emissions, when the VVT can increase torque also. With a small displacement engine, more torque at low RPM is needed, so why would Audi not take advantage of that? The emissions at cold start up, don't need to rely on the VVT, there are other ways of achieving the required emissions limits at lower cost. More torque at lower RPMs with the VVT helps the turbo spool faster as well. VVT will have a fatter torque curve than the same engine running the same cams without it. I don't know why anyone would not use VVT by disabling that function, unless reduced area under the torque curve is preferred. In addition, it is also illogical, makes no sense for a performance cam designer to offer cams for VVT engines where the VVT must be disabled in order to use the cams. If that was the case, the cam design is not appropriate for the application, IMO. 

Are you joking? Have you seen how big torque levels does 1.8T have in stock form down low? It is like diesel engine with highest torque at 1900 RPM (1.8T 180HP). This small displacement engine has silly small turbocharger which hapilly provides boost at near idle levels but do not want to cooperate with you when you want it to boost at around 6000 RPM - and this is why even strong tunes for K03s and pump fuel (no E85) has highest power below 6000 RPM most of the time!

Have you ever driven 1.8T powered car? Do you know it has 5 valves per cylinder and 9,3-9,5:1 CR stock? This is why you are not able to use VVT with hotter cams as it would cause interference between valves or between valves and piston.

Yes, daily. Using a performance intake cam profile that requires that VVT be disabled, will result in reduced area under the torque curve, although a fixed timing cam profile may provide higher torque at a specific RPM, the area under the torque curve will be reduced. VVT allows better volumetric efficiency and torque over a wider RPM range compared to a non VVT intake cam profile. If you need a specific cam profile to produce best high RPM torque suitable for only drag racing, then a fixed intake cam timing profile may be preferred, even if the low RPM torque  is a lot lower. A car with a fixed cam timing optimized for best high RPM torque, will be practically useless at low RPM and will be difficult to drive on the street. The main benefit of VVT, is for increased torque and low and high RPM, a wider useful torque RPM range, and more area under the torque curve, compared to a non VVT cam design. A fixed cam timing profile will require accepting more compromise over the entire RPM range. A cam profile optimize for best useful torque for street driving will not require the VVT be disabled. Any cam requiring a fixed cam timing, is not a good cam for use on a street driven car. The main point of this is that Audi does not limit VVT to only cold starts. More torque is always better than less. It is fundamentally illogical and unreasonable to believe Audi limits VVT to only cold start up. The technical facts involved with VVT cannot support this untrue allegation. It is much better to use balanced measures of  higher boost pressure, advanced ignition timing, proper A/F ratios, fuel anti-knock rating and effective intercooling capacity compared to relying on extreme cam profiles. A cam profile requiring fixed timing, is not a suitable cam design for a VVT 1.8T IMO. 

And what about older 1.8T engines which did not have variable cam timing while still having silly high torque down low?
Of course VVT has its benefits but you will not find any aftermarket camshafts which are designed to be used with VVT... And there are people who use such cams in their daily drivers. If you do not go too wild it will still be good normal car.

There is no such thing as to much low RPM torque, especially with a 1.8T. I don't know how much torque "silly high torque" is. The earlier non VVT 1.8Ts do not have as much area under the torque curve compared to a newer VVT 1.8T. With only 150 HP, stock, that is because there is less torque available. HP is the product of torque and RPM. No way around this.

The rough idle is due to excessive valve overlap at low RPM, from exhaust reversion into the intake ports and results in reduced volumetric efficiency compared to a suitable VVT cam profile. A fixed cam timing cam profile will always require more compromised results somewhere in the useful RPM range.

150HP is there only because the boost is lower. Cams and VVT/non-VVT does not make any difference there. Just try to run older 150HP engine with same boost as 180HP and check torque/power levels.

I will tell you once again - VVT is used only for emissions in stock 1.8T ECUs. Replacing stock cams does give better torque at midrange and top end.

On a K04 it is used on WOT to have more torque as well.
On a K03 there is not much point, since the turbo is so small the overlap actually hurts you.

I did some dyno testing with VVT switched both ways. On K04 and up there is a massive torque increase by keeping the VVT on until the turbo is fully spooled up. I am talking over 50nm difference at same rpm.

As for this cold start emissions crap - I've no idea who came up with that yadda yadda, but anyone saying this clearly has never ever looked at the VVT control maps on any 1.8T engine. Even on K03's it is used to increase part throttle driveability and response.

Keeping VVT active until 3000rpm with a K04-020 gained me 14lb/ft over the stock mapping.

I agree on the emissions as well. That was obviously not the intention.

I am quite sure that information about VVT being used for emissions was taken from some VAG documents.
IMHO still using hotter cams (which has bigger overlap "by design") will give you more torque and power even if you can not use VVT anymore.

Source?
More peak torque and peak hp, at the expense of low down torque.

So the unanimous answer is no vvt with aftermarket cams.  Ok.  So on to the next question. ..   does anyone know where in a stock 1.8t map about the vvt is located so one could tune it?  14ft lbs on a dyno with vvt vs non. Hey. More is more right? Why wouldn't one want to mess with it?

Hardly.
Because few of the so called tuners actually understand how an engine works these days. Their only religion is the % button.

VVT in all Motronics is in the same Group Maps! With bigturbo setups you can get from 500-1000RPM faster spool when you run bigport head AEB/AGU/ADR and big cam profiles like 3658 or 3652 with a lot of overlap!

What I do and my clients adore is to enable Cam Control (cam position = 1) and keep it to all load range up to full boost point. You need some dyno pulls to see how late you can turn off the Cam Control from the full boost point.
Often with 3658 cams I close it 300RPM after Full Boost point

on ME7 Cam Control is not fully variable like TFSi but it is ON/OFF, indeed it helps too much for bottom-end and low-end torque

For idle stability you can either change exh. cam settings with a variable gear or you can test cam controlling


Furthermore how Cam Control works on 20vts
light weight cars (Leon, Ibiza, Polo etc) only for cat heating and then OFF
mid weight cars (Audi S3 etc) cat heating and remains ON in low load and RPM
heavy cars (Audi A4 quattro etc) cat heating and remains ON in higher load levels and mid range RPM

Oh. Interesting. Well I doubt my 210/210 cams are going to provide much of a noticeable difference. 

on stock cams the is no noticable difference but when you install big overlap pairs like 3658 or 3652 CatCams the different is noticable and turbo lag decreases more than 500RPM