Adjustable Exhaust Camgear Setting

[KiwiRS4T]

Lots of people must have a series 2 RB25DET with an adjustable exhaust cam gear. Has anyone done the testing to determine the best setting? That is has anyone done a series of dyno runs where the only variable was the setting of the exhaust cam gear?

I have one on my Stagea with basic mods: 3in turbo back exhaust and GCG highflow turbo which will be running 1bar (about 16psi) when i install my Z32afm and 550 injectors. It is currently set at 4 (crank) degrees retarded as per SK's suggestion. Unfortunately he never got around to the dyno testing to find the optimum setting. Surely someone has done it? If you haven't I would still be interested to hear what you have set it to but i really want a setting based on real live testing.

Thanks!!!

[FineLine]

There is no hard and fast rule as to the setting. Each engine will respond differently to changes in cam timing.

Let your tuner and the dyno tell you where the cam timing needs to be for best performance.

[R31Nismoid]

You didnt dyno test for the best settings? jebus...

As per what Noel said - every car = different.

Some like neutral, some like 2 degrees, some want 4 or 5. You should test - not just go on someone else's suggestion

[Sydneykid]

  KiwiRS4T said:

Lots of people must have a series 2 RB25DET with an adjustable exhaust cam gear. Has anyone done the testing to determine the best setting? That is has anyone done a series of dyno runs where the only variable was the setting of the exhaust cam gear?

I have one on my Stagea with basic mods: 3in turbo back exhaust and GCG highflow turbo which will be running 1bar (about 16psi) when i install my Z32afm and 550 injectors. It is currently set at 4 (crank) degrees retarded as per SK's suggestion. Unfortunately he never got around to the dyno testing to find the optimum setting. Surely someone has done it? If you haven't I would still be interested to hear what you have set it to but i really want a setting based on real live testing.

Thanks!!!

I haven't tested it on the Stagea, but I have tested it on a number of RB25DET's in other cars with GCG high flows. The -4 degrees is the most common setting for improved reponse, slightly faster boost build and slighty more power from around 3000 rpm to 5000 rpm. Of course you get nothing for nothing, so there is a slight loss of power from 5500 rpm to 7250 rpm. So the setting is dependant of what you want to achieve and it does vary sometimes from engine to engine. As always I would treat the -4 as a place to start, then tune from there.

Cheers

Gary

[KiwiRS4T]

Yes I appreciate that testing is the only way - guess I was looking for a short cut. It runs fine at 4 deg but i will take the time to try other settings.

[datsfreak]

I just got my adj gear in the post.

Its -4 retarded at the crank right?

so the adjustment would be 2 of the little notches if the inner wheel was turned clockwise - that being if each notch = 2 degrees of crank

thanks

BTW a good post on dyno gains from this is at:

camgear

[KiwiRS4T]

Thanks for the link but three pages of posts didn't tell me anything that i didn't already know - that an adjustable exhaust cam gear on an RB25 DET can give you a few extra KW. What I really wanted to know is if anyone has done the hard yards and tried a number of different settings to see which gives the best result. It is a pain to do because you have to take off the cas and put it back between each run but as has been pointed out before it is the only way to optimise the setting for your car. I will be doing it this weekend and will see if i can pick the best spot with road testing. If not it will have to wait until I get on the dyno in a couple of weeks. I'll report back!

[R31Nismoid]

I doubt you'll find power in the top end... the only thing you might find is midrange improvements with the adjustements.

How much gain is subjective as you already know, peka power really shouldn't change

[_Ryan_]

Don't Stagea's use a different cam to the equivalent skylines, so their settings would be irrelevant?

[Dose Pipe Sutututu]

check this out

http://www.uniqueautosports.com.au/dyno.htm

look at the dyno results from the tunes that John did on RB25DETs with aftermarket exhaust cams

[KiwiRS4T]

  R31Nismoid said:

I doubt you'll find power in the top end... the only thing you might find is midrange improvements with the adjustements.

How much gain is subjective as you already know, peka power really shouldn't change

Not really looking for more top end - want more in the mid range. I don't believe in subjective improvements (it feels faster etc). I would be looking for measurable improvement e.g. on the road i will be measuring 60 to `120 times in 2nd gear or on the dyno actual kw.

[paulr33]

i wonder what mine is set to, i know dr drift said the factory position was best but i wonder if its different

ive got the bass junky factory hack cam gear adjustable thingy on mine

my top end does feel a bit flat ish - always has and my car never made mega power, 191rwkw was its peak

but the response and low down power is absolutely amazing - even with 213kms on the clock now, its still got amazing response

standard rb25det with usual mods, std turbo, std cams, cam gear adjusty thingy, assloads of ignition timing (peaks near 53deg) on the map

but im dead certain the CAS is backdialed a touch too

[datsfreak]

Might be a stupid question but... my cheap brand adj gear has the R on the left and A on the right of its adjustment.

BUT looking at pictures of HKS adj gears it is the other way around

For example look about half way down this following ad for parts, he is selling a cheap brand gear but behind it there is a HKS gear box--the markings are opposite.

ad with adj cam gear

Whats the deal.?

The motor turns clockwise(looking from the front) so the cheap gear it correct, ummmm, is it?

[KiwiRS4T]

  datsfreak said:

Might be a stupid question but... my cheap brand adj gear has the R on the left and A on the right of its adjustment.

BUT looking at pictures of HKS adj gears it is the other way around

For example look about half way down this following ad for parts, he is selling a cheap brand gear but behind it there is a HKS gear box--the markings are opposite.

ad with adj cam gear

Whats the deal.?

The motor turns clockwise(looking from the front) so the cheap gear it correct, ummmm, is it?

You don't have a picture of your cheap cam gear. The one in the photo is correct in that it shows degrees of retard (or advance) correctly on the scale i.e. to retard cam timing you turn the adjustable pulley anticlockwise and the correct reading will line up with the mark. Maybe your cheap pulley is indicating the direction you need to turn the wheel rather than showing the correct scale for adv or ret.

[datsfreak]

Here is a pic of my cam gear...

If I turn the inner wheel counter-clockwise, it will indicate A(advanced) on the marks..

So this is wrong?

[Sydneykid]

  datsfreak said:

Here is a pic of my cam gear...

If I turn the inner wheel counter-clockwise, it will indicate A(advanced) on the marks..

So this is wrong?

Yep it's wrong, HKS have it right

Cheers

Gary

[datsfreak]

Thankyou!

That was what I was thinking but I really wanted someone else to verify it.

  Sydneykid said:

Yep it's wrong, HKS have it right

Cheers

Gary

[DYNAMITE]

Heres mine not sure wat its set 2