Saturday, May 28, 2011 - 02:39 am, by: Fabian Bordon(Aether)
Is anyone able to confirm if the timing set in the picture below is advanced or retarded for the exhaust cam, and also if the markings on JUN cams are 1 or 2 degrees per mark etc?
Friday, June 03, 2011 - 04:10 pm, by: Fabian Bordon(Aether)
That's where I have the confusion as the JUN cams have no 'A' or 'R', but others I have seen have, and I was under the impression that turning the inside slide clockwise as per Antonio's picture would be advancing it as well as the marking moves closer to the 'A' print? And by the looks of things that HKS cam is for a JZ motor?
Costa Tsimiklis Goo Roo Victoria 386.2 rwkw the old T51S setup - New Setup HKS T51R SPL -Going for 450rwkw on Pump Gas!
Wednesday, June 22, 2011 - 08:59 am, by: John O'Brien(Ziggy)
I'm with Antonio on this one. Seems to me that if you rotate the cam clockwise you are advancing the timing. In the picture the mark on the outer is moved towards the 'A' side so I'm gonna throw a spanner in the works and say that pic shows 4 degrees advanced.
Friday, June 24, 2011 - 10:05 am, by: Aiden Cheese(Chillpen)
this pic
and this pic
Are not adjusted in the same way. The interior on the HKS is almost the whole pully except cog. The top pic is only moved from a section which is different.
So the top pic is retarded. The Cog Notches lag behind the pulley spinning compared to if it was centered.
Friday, June 24, 2011 - 02:05 pm, by: Antonio Hunt(Carajo)
The belt is what is spinning the cams clockwise, the belt timing dosen't change from altering the cam gears. so when you turn the inside/cam clockwise of the mark on the cogs it is advancing the cam. All cam gears are generally the same, including the above 2. They mainly consist of 2 parts, the cogs running off the belt and the inside that is attached to the cams. All that is different is which direction the belt runs on that particular model of engine.
Sunday, June 26, 2011 - 11:23 pm, by: Aiden Cheese(Chillpen)
Where they're measuring the A and R is in two different spots is how i meant that they're not adjusted in the same way. Therefore they can be misleading to compare two different designs closely.
Of course they can't be entirely different because they both do the same thing.
But because of exactly what i said, is why it's A anti-clockwise (depending how you consider anti clockwise, or which bit, so the outer bit moves anti-clockwise, the inside moves clockwise) and R clockwise (same thing).
By slowing the cam down in relation to the belt, you make it spin slower. For one brain fart I for some reason said it backwards.
Haha. My reasoning was right, my words were wrong.
Monday, June 27, 2011 - 09:57 am, by: Matthew Sharpe(Madmatt)
Not slowing it down so much as changing the angle of the lobes compared to TDC on the crank - the cams still have to rotate once for every 1/2 revolution of the crank - no way around that! :-)
Monday, June 27, 2011 - 05:20 pm, by: John O'Brien(Ziggy)
The only reason I jumped into this thread is because I felt Fabian was being led astray.
Let's take it slow.
The cog part of the assembly is never adjusted. It is moved clockwise only by the belt and normally the mark is at the top when the Number 1 piston is at TDC.
These wheels have a centre part attached to the cam which can be adjusted.
Now given the engine spins clockwise, if you turned the centre part (attached to the cam remember) clockwise, it will mean the lobes are now in 'advance' of the mark on the cog. It is out of synch now because of the variable geometry of the wheel. If you turned the inside part anticlockwise you are winding the cams back and if you go anticlockwise passed the centre mark on the scale you have now 'retarded' the valve timing.
Fabian's picture clearly shows that the inside of the adjustable cam wheel has been turned clockwise. The centre mark of the scale is to the right of the timing mark on the cog.
This would seem to indicate that the cam is now in advance of the crank.
Tuesday, June 28, 2011 - 10:52 am, by: Aiden Cheese(Chillpen)
I was speaking to Lew the other day and he basically described it like this;
You can only advance or retard the intake cams by 4 deg or else the ecu will go into limp mode. The exhaust though can be changed much more.
What he found in his testing was that changing the timing would literally move the power curve up or down the rev range. That is, you could get good boost, and higher flowing exhaust earlier to increase throttle response and lower down power or alternatively go for higher top end power with a bit more power-lag.
These are my words so don't quote lew using them. I wasn't exactly studying, I was chatting
I think he also mentioned that after dump replacement, changing the exhaust a little increases the plain efficiency as the freer flow of the dump will help spool the turbo earlier, and changing the cam can help improve that more without losing top end?
Not 100% sure. But in short the cam timing can increase power and change the power band. Tuning them is a normal part of improving the power of the car.
Tuesday, June 28, 2011 - 04:40 pm, by: John O'Brien(Ziggy)
That makes sense. With a freer flowing exhaust you could retard the exhaust cam and have more 'overlap' (when the inlet and outlet valves are both open). Then the mass of air flowing down the exhaust will suck a bit more of the good stuff in through the inlet, assisting the suction of the descending piston and giving you a bit more bang for your buck.