GTR Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
193 Posts
Discussion Starter · #1 ·
I plan on fitting adjustable cam-pulleys during my upcoming rebuild.

Anyone that have information on basic cam-timing settings to keep driveablility and good low-end torque when using HKS Stage1 264/264 cams in conjunction with adjustable cam pulleys?

With stock pulleys fitted the engine performs very well from low- to high rpm:s (both torque-wise and fast revving) :)
So I wonder what possible gains, disadvantages etc.. a different cam-timing will possibly give.

Found elsewhere information saying that a few degrees advance on Inlet cam and a similar retarding the Exhaust will improve performance (but no specific info on torque gains/loss specified).

As I am primary looking for good low-end torque (as present with std. pulleys) all ideas and recommendations on settings are welcome.

Engine is 2,6 std. R34-ceramic turbos (Boost 1.10), PowerFC, 720cc inj. about 430bhp at flywheel.

Possibly GT28Rs will be replacing the present turbos..
T.I.A.
Lars B.
 

·
Registered
Joined
·
190 Posts
The factory cams are set up to have almost zero valve overlap so that the engine will meet statutory EPA idle emissions. Engine tuners have found experimentally that retarding the exhaust cam and advancing the inlet cam a very few degrees can improve general engine characteristics, provided idle emissions are no longer important. But each car is slightly different.

When you buy a set of aftermarket cams, they will already be ground to give the correct valve timing when used with the original factory cam pulleys. There should therefore be no need to vary the cam timing from what you get straight out of the box, provided you have selected suitable cams in the first place.

If you plan to do some dyno tuning and serious further engine development work, by all means fit variable cam pulleys. But initially you are not going to know where to set those cams, because you have no idea what the engine will like best.
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #3 · (Edited)
Anybody else that want to share their experiences?
There must be loads of tuned RB26:s with aftermarket cams with fitted adjustable pulleys for other reason than "good anodized looks". :)
If not clear from my first posting, I have since long time run the car with the cams specified, but have never run it with adjustable pulleys. Driveability was/is excellent and no problems with emissions using these HKS cams.
I am just looking for possible gains by slight valve timing changes. No radical improvements in performance expected.
 

·
Registered
Joined
·
936 Posts
I have aftermarket Toemi Pon cams on mine. They are supposed to be able to be fitted with the standard pullies without the need the "dial them in".

The cams did need to be "dialled in" on my R34 even though some tuners would not bother for the sake of a degree or so. I just wanted to make sure the cams were set up exctly to the crank.

There are always going to be tollerances in engine parts and so the use of the adjustable pullies alows exact "dialling in" of the cams to the crank. This should give the cams the optimum range as the manufacturer's expected.

Nik
 

·
Registered
Joined
·
193 Posts
Discussion Starter · #5 ·
Thanks for your thoughts :)
As what I was told by a racer at the midsummer JapShow at Santa Pod the HKS cams I (and he) use will give quite improved high-rev power gains if inlet cam is advanced (approx 10 degrees, unsure if my memory is correct) and exhaust is retarded somewhat (..forgot the setting).
BTW, Driver in question won the Nissan class.. in his GunGrey R32 :)
Naturally this was a modified RB with a huge turbocharger, and not really comparable with a almost std setup as mine..
But anyway, I was amazed by the extreme response that these "mild" cams are able to give.
I have no ambition to go drag-racing, so perhaps a setting close to zero advance/retard is as good as it gets to permit best low-end/mid-range torque.

// Cheers, Lars
 

·
Registered
Joined
·
2,056 Posts
I've got Tomei 260 degree poncams on mine, 600cc injectors, standard 2.6 litre capacity and R34 turbos. The cams are on verniers.

I don't know what settings Abbey set onto the verniers (maybe you should ask them or someone else with similar facilities and experience to do yours?) but they managed to bring the boost in 300rpm earlier on mine without significantly losing top end power.

There are comparison graphs on my site http://www.planetkingsley.com/skyline/

The car is making 420 bhp at the hubs, which is approx 480 - 490 bhp at the flywheel. at 1.15 bar. The dyno runs are only 12 second runs (so boost comes in later on the dyno) but on the road in a top gear roll on I get 1.1 bar of boost at 2500rpm.
 
1 - 6 of 6 Posts
Top