rb20 - adjustable cam gear settings

[ToroGTS]

I'm getting a set of adjustable cam gears to replace my old rusty OEMs. I'm wondering if there are any generally accepted intake/exhaust cam settings that might give me a benefit without taking it to the dyno. Any info or recommendations?

[99_SI]

Advance intake , leave exhaust. Hope you have a wideband to keep and eye out on afr...


Sent from my iPhone using Tapatalk

[FunnyGas]

Generally....
+3 IN
-5 EX
...is usually where most end up.
Adjust a degree or two at a time, not 3 or more. You can check compression after adjustments to see any gains. Moving the valve closer to the piston is your goal (but not too close), your compression should increase. You will need to set base ignition timing after each adjustment. Tuning (on the dyno) will see the most gains from these.

That's what I can remember from my RB20 days anyways.

[Skym]

Do the adjustments on a dyno, as need a dyno to see how it affect's the powerband after each adjustment. Also make sure you can adjust fueling, timing to suit (Nistune or similar).

How to degree cams properly -

http://www.kelford.co.nz/sole-purpose-of-degreeing-your-cam

Adjusting intake camtiming + or - and how it affect's powerband -

http://www.tomei-p.co.jp/_2003web-catalogue/e092_adjust-p.html

Power gains (also affect's torque curve) from adjusting camgears on a RB20DET (click on photo in link below) -

http://www.uniqueautosports.com.au/service-centre/dyno-centre/skyline-r32-gts-t.aspx?back=1195

[ToroGTS]

I do have wideband and nistune ect. I'm thinking I'll just throw it on +2 intake and -2 exhaust, until I can get it on a proper tune.

[Dragon Humper]

The tried and true method of adjusting the intake closing point to achieve maximum compression has never steered me wrong in 25 years. Install the gears straight up and then move the intake around up to a 5deg max the get the most compression on the highest reading cyl you have (with all the plugs out and the throttle blades wide open). The intake closing point is the most critical of all the timing events and the compression method is king to figure that out, it is also qite variable from motor to motor, even stock. Things like machining tolerences, headgasket type and amount of belt stretch play into that. One motor could need 2deg, another could need 6.

Once the intake is set play with the exhaust. If nothing much happens then you can advance it to give you a fatter top end or retard it a bit to bump up the low end torque. That is tightening the lobe seperation and spreading it, which biases torque production to higher or lower in the rev range respectively.



Jon.

[ToroGTS]

Dragon,
Any effect on spool from cam timing? I would imagine reduced open valve overlap = less exhaust backflow into cylinder and hotter (more expanded and energetic) exhaust gasses giving a quicker spool.
Is there much overlap on the oem cam profile anyways given that this engine is stock turbo?

[Dragon Humper]

The effects of cam timing on an engine is generally the same N/A to boosted, it much more pronounsed in a turbo motor. The wider lobe seperation will generally speed up spool but hurt over all power production. Biased low end timing will make the 20 feel more like a 25 stock to stock. Once you get a bigger turbine though it doent make as much of a change.other than make the spool much more like a light switch instead of a nice progression. Thats a user prefference thing.



Jon.