7a cams-intake retard!?

[GazzaG60]

iirc 1 tooth on the 16v was 7 degrees

[driftin jo]

iirc 1 tooth on the 16v was 7 degrees

360deg/51 teeth=7.058 deg

[JP]

Yes and no.

we're talking about just advancing the intake relative to the exhaust so we'd be looking at advancing the chain gears not the main pulley. The chain gears are 25teeth so every tooth is 14.4 degrees which is a lot more than you want.

[V6quattro]

7A intake:
Opens: 6 Degrees ATDC
Closes: 38 Degrees ABDC
Duration: 212 degrees

7A exhaust:
Opens: 42 Degrees BBDC
Closes: 3 Degrees BTDC
Duration: 219 degrees

So where is the overlap?
Exhaust is long closed (3 deg BTDC) when intake opens (6 deg ATDC).
9 degrees is the time when both the intake and exhaust valves are closed (theoretically speaking, not accounting for the fact that the valve is on a spring and not instant).

From another perspective - 7A cams always make more top-end power than stock cams. If there was overlap, then top-end power would drop off, due to backpressure on smaller exhaust housings.

If you are really measuring something, then your camshafts are not timed correctly.

As I'm not really happy with the power output of my engine I did some measuring on my 7a cams today. Are this the factory settings measured at 1mm valve opening?

This are the results measured at 1mm opening at the lifter.
Intake
Opens: 0 Degrees ATDC
Closes: 28 Degrees ABDC

exhaust
Opens 50 Degrees BBDC
Closes 15.5 Degrees BTDC


Strange results right? Can I say my camshafts are approximately 8 degrees retarded?

[V6quattro]

Just remembered my timing mark on thw valve cover was always 0.5 tooth off. When i turn the engine to correct timing on de valve cover the crankshaft is 8 degrees BTDC!!! (see photo)

How could this happen? I have a steel crank gear and a adjustable cam pulley. Could it by possible the timing-mark on those aftermarket items are wrong?

I think i will instal it to the factory specs and not look at the timing marks. How will this effect my power. I think i will put it on the dyno again and see if some more power is plausible

In running a Precision 6262 bb .68 A/R T4 3,5inch exhaust on E85 2.1bar

[Laaf]

If using that kind of cam wheel you have to check the camshafts timing by lifting the valve cover. The marks on the wheel are used when making fine adjustments on the timing, not for setting the engine to original markings at TDC.

[V6quattro]

Thanks laaf!

So the white mark on the camgear does not represent the original timing mark? If i remember right i also tried the original camgear and it also was 0,5 tooth of.


I also like to say i use a rs2 timing belt and waterpump.

[Laaf]

Thanks laaf!

So the white mark on the camgear does not represent the original timing mark? If i remember right i also tried the original camgear and it also was 0,5 tooth of.


I also like to say i use a rs2 timing belt and waterpump.

Correct, on your camwheel the scale has worn away. But it is used when changing timing setups.
I dont know if you have it right when you are using a ADU belt and waterpump. I think the timing marks on the chain sprockets would line up as normal even if the timing mark on the camwheel is 0,5 tooth off.

[V6quattro]

Correct, on your camwheel the scale has worn away. But it is used when changing timing setups.
I dont know if you have it right when you are using a ADU belt and waterpump. I think the timing marks on the chain sprockets would line up as normal even if the timing mark on the camwheel is 0,5 tooth off.

If the engine is at TDC and the timing-mark on my camwheel is 0.5 tooth to the right (as i currently run my car) the timing marks on the chain sprockets do not line up.

If i line up the cams using the round marks on the chain sprockets (the timing mark on the camwheel lines up perfectly with the valve cover) and put the engine at TDC i can't get the timing belt on because is 0.5 tooth of

Only thing i don't really understand is that are my cams now advanced or retarded?

[V6quattro]

Nobody ever had this issues? Camshaft is a half tooth off.

I use EFIexpress crank gear / rs2 timing-belt and water-pump / Tommi's Billet adjustable cam gear (but if i remember right i had this also with the original cam gear.

[Greg_S]

I assume you are running rs2 belly and water pump. If so IRS correct that it is .5 tooth out on the timing mark

[V6quattro]

What do you mean with 'rs2 belly'?

I you don't use the RS2 cams an camgear you don't have to set timing 0.5 tooth out right?

When im at TDC the markt on the camshafts are also 0.5 tooth out.