cam timing for xr6 hp

[FS5]

i've been playing around with the cam timing with my xr6 cam.i currently have it advanced 5*.
my question is how far can i safley advance this cam ?

[atec77]

Originally Posted by FS5

i've been playing around with the cam timing with my xr6 cam.i currently have it advanced 5*.
my question is how far can i safley advance this cam ?

why would you want to advance it ?
there are adjustable drive gears if you have the $

[Stav]

I think generally you do not want to go more than the 5 degrees but I am just going by hearsay.

[FS5]

i remember jonbays posted something about cam timing on a thread a year or so ago but can't seem to find it.

[Sox]

Advancing a cam increases low end power, at the expense of top end.
More than 5deg would make it rather breathless up top, and it might also encourage detonation.

Rick.

[JoesAu]

or u might you lose your valves as well lool

[FS5]

i know the effects of advancing and retarding the cam.
i'm just experimenting at the moment with the hp cam ,i believe advancing it will run a quicker ET at the track.
sox,i'm only running it on the standard ecu at the moment.you reckon it would still ping just using that?
its not breathless up top ,not yet anyway.it still peaks around the 5200/5300 mark.compared to running it at 0* it dosent seem to have lost much topend if any,but its picked up heaps more midrange

[FS5]

Quote:
Originally Posted by au3xr6
the cam is not the same as the HP at higher revs here are the cam specs
lift
HP inlet 6.743 exhaust 6.434
VCT inlet 6.717 exhaust 6.434

timing
HP INLET OPENS @ 14 DEG BTDC CLOSES @ 68 DEG ABDC
VCT INLET OPENS @ 12 DEG BTDC CLOSES @ 72 DEG ABDC

HP EXHAUST OPENS @ 56 DEG BBDC CLOSES @ 24 DEG AADC
VCT EXHAUST OPENS @ 58 DEG BBDC CLOSES @ 24 DEG AADC

the difference between the XR6 VCT and the fairmont VCT is in the ECU fit an XR ECU and you will gain 4kw and 3nm hardly earth shatering but there are small gains. an added benifit of the XR ECU is adaptive shift no wiring mods are required to make this change so you get a slight performance boost with the more agressive shift maps available

this was posted in one of my earlier threads,considering the vct and hp cams run the same exhaust vailve lift.but the vct cam opens up the valve 2* earlier, then when the vct thing dose what it dose it advances it a further 10* (correct me if i'm wrong).
going by this i should be able to advance it atleast 12* ????
i want to try it around 8* advanced but i want to be 100% sure before i give it a go.

[Sox]

Originally Posted by FS5

i know the effects of advancing and retarding the cam.
i'm just experimenting at the moment with the hp cam ,i believe advancing it will run a quicker ET at the track.

Possibly, ET's are all about launch, and more grunt down low will certainly help in launching.
Your terminal speed may be down slightly though.

sox,i'm only running it on the standard ecu at the moment.you reckon it would still ping just using that?

It's hard to say, advancing does require less ignition advance, so it will certainly get closer to detonation.
The AU's have a knock sensor, so if it does, it might only be for a split second when cracking the throttle at low revs.
I assume you use 98 fuels, and if you don't then now might be a good time to start.

its not breathless up top ,not yet anyway.it still peaks around the 5200/5300 mark.

Ok, 5300 is quite low anyway, so the power loss might be above that, and less noticable anywa because power was already dropping off.

compared to running it at 0* it dosent seem to have lost much topend if any,but its picked up heaps more midrange

Yep, a good strong midrange is damn handy for passing etc.

Rick.

[Sox]

Originally Posted by FS5

this was posted in one of my earlier threads,considering the vct and hp cams run the same exhaust vailve lift.but the vct cam opens up the valve 2* earlier, then when the vct thing dose what it dose it advances it a further 10* (correct me if i'm wrong).

That would appear to be the case.

going by this i should be able to advance it atleast 12* ????
i want to try it around 8* advanced but i want to be 100% sure before i give it a go.

The other thing to be mindful of is the VCT will have a different ignition timing map, so it will retard ignition timing when the cam is advanced. You won't have that control, so may have detonation issues.

It's worth a try I guess, maybe talk to someone like JMM before doing it, just to be sure on piston to valve clearance.

Rick.

[Stav]

Originally Posted by FS5

i know the effects of advancing and retarding the cam.
i'm just experimenting at the moment with the hp cam ,i believe advancing it will run a quicker ET at the track.
sox,i'm only running it on the standard ecu at the moment.you reckon it would still ping just using that?
its not breathless up top ,not yet anyway.it still peaks around the 5200/5300 mark.compared to running it at 0* it dosent seem to have lost much topend if any,but its picked up heaps more midrange

I have to disagree that the car will lose much power up top .I got my car dynoed some years ago..131 rwkws.I advanced the cam 4 degrees and the top end power was still 131 with a fatter power curve.I dont know if this is typical but thats what happened in my case. I do believe it is the synergy of the parts and not just the cam that determines peak power. Exhaust design and inlet design have probably a bigger effect of peak power rev ranges.

[sly]

Only going on seat of the pants, but my car doesn't seem to have lost any top end with the cam advanced a bit. In fact it now has a slight (but noticeable) lift as the short runners open. Before there was just a change in the induction noise.