Anybody tried changing cam timing?

[TDI4evah]

I've heard that advancing the cam slightly, like a degree or two, will give a little more responsiveness a few more HP.

Retarding the cam is supposed to make for slightly better economy, presumably at the expense of power.

Anyone tried it? What were the results?

 

[bmp]

I tried it

I have PD140 16V so I don't know how pertinent this is to 1.9 engines, but there are some interesting results to be had.

I tried both advancing and retarding both cams.

Advancing resulted into great response off idle, stong low end power and noticeably decreased power from 3000rpm up.
BC showed much lower fuel consumption, but in reality it stayed same as before.

Retarding cam reduced power in lower revs, throttle response was more dull, but from 3000rpm up it went like cut snake and kept pulling beyond 4000rpm.
With stock timing engine just suddenly lost all power at 4000rpm and refused to rev any further.
BC showed much higher fuel consumption, but calculation at the pump revealed that it was acually lower by about 0,2l/100km.
BUT - after I started adding diesel additive fuel consumption decreased by another 0,5l/100km which is total of 0,7l/100km lower when compared with stock timing.

And the same fuel additive did absolutely nothing with stock timing

I SWEAR I'M NOT MAKING THIS UP. I absolutely don't understand what happened there, but I'm definitely not complaining

Btw, my mechanic almost murdered me after he spent considerable amount of time trying to "fix" crankshaft to camshaft pulleys when replacing my camelt only to find out it's impossible because I have retarded cams like half a tooth in relation to crankshaft compared to "proper" timing

So that is my experience tinkering with cam timing. Hope I won't be stoned to death for this post

 

[TDI4evah]

Interesting.....

So retarding the cam some made the computer display claim higher fuel consumption but it actually fell a bit? I don't have q fuel use display, so the computer won't mix me up on an ALH

How much did you retard it?

Lastly, what was the fuel additive you used?

Thanks

 

[TDIMeister]

Everything bmp describes sounds like he had advance/retard reversed... :/

What likely happened is that since changing cam timing on a PD also changes mechanical injection timing, it had a greater effect on performance than 1- or 2 degrees would actually have on valve event timing, which would drift at least that much in the direction of retard as the belt wears and stretches.

 

[bmp]

TDIMeister: I loosened the three bolts that attach cam to the pulley and than rotated the camshaft itself.
By retarding I meant rotating camshaft anti clockwise and by advancing rotating it clockwise.
Did I get it right or is it the other way round?

I also think this situation has more to do with injection timing and quantity than with valve timing. I also forgot to mention that with "advanced" camshafts car smokes a lot more at full throttle.

TDI4evah: I think I changed the timing quite a lot. I dont have the exact figure, but it's the equivalent of half the cambelt tooth.

The fuel additive is this -> http://www.vif.cz/produkty/aditiva-do-nafty/super-diesel-aditiv-letni.html

I'm sorry, but it's a local product and I couldn't find any info in english. Interesting thing is that there is summer and winter version of this additive but only summer version makes my fuel economy better.


Btw, I have some minor aerodynamic improvements and LRR tires on the car and under the best circumstances I'm able to get over 70MPG on an extra urban trip and 60MPG tank is quite easy to achieve which is unheard of on 2l PD engines so I can only recommend playing with camshaft timing.
I've been doing this for two years now without any problems whatsoever so I guess it's also a pretty safe thing to do.

 

[TDIMeister]

TDIMeister: I loosened the three bolts that attach cam to the pulley and than rotated the camshaft itself.
By retarding I meant rotating camshaft anti clockwise and by advancing rotating it clockwise.
Did I get it right or is it the other way round?

Yup, you reversed it.

 

[bmp]

Ok, thank you for pointing that out.
I edited my original post so I hope it's correct now

 

[robnitro]

I don't think he reversed it tdimeister.
Facing the tbelt side of engine, the engine turns clockwise, correct?

If he turns the cam clockwise relative to the sprocket/belt, he is advancing the cam.
Similar to when we do on VE tdi with the injector pump bolts.

I think he gained power with advance (despite valve timing advanced doesn't help top end) because the injectors have more advance, which helps higher rpm timing.

bmp,
How do you measure the mileage you get? Do you do it by fill up or by watching the display?

 

[bmp]

I am religious about my mileage, so I always calculate it by fill up
Sometimes I also check if my computer measures distance correctly just to be sure i'm getting accurate numbers.
Yes, I know I'm mad

 

[tikal]

I have a 2004 Passat with the re-profiled Franko6 cam. I have tried retarding the cam all the way to -3.6 with no noticeable gain in mileage. Other folks report that by retarding it to around -4 they have gain around 5% to 15% in MPG.

 

[TDI4evah]

I have Frank06's cam too, but in an ALH. 5% sounds pretty good to me, let alone 15.

Maybe I'll give it a try.

 

[TDIMeister]

I found the error in reasoning – I was burned out yesterday. Thanks for setting me straight, robnitro. bmp was talking about loosening the bolts that hold the cam to the sprocket and rotating only the cam itself while keeping the sprocket stationary; I was going by rotating the sprocket and timing belt together, essentially rotating the engine AROUND the stationary cam, since in the VE TDIs one locks the cam position position. This would require a reversed thinking from what bmp was talking about.