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Rb26 Cam Choice

Brezza

By Brezza,
in Engines & Forced Induction

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r33_racer Grand Master

r33_racer

Posted
Posted

You really should do the valve springs with those cams too. More so just because of the possible valve float you could have when you start winding the boost into it. Then it will be another job to do and more time off the road. May as well do it when you do the cams and then it cant be a problem.

Brezza Proficient

Brezza

Posted
  • Author
Posted

You really should do the valve springs with those cams too. More so just because of the possible valve float you could have when you start winding the boost into it. Then it will be another job to do and more time off the road. May as well do it when you do the cams and then it cant be a problem.

I'm not planning on putting more boost into it.

i'm wanting to keep high boost around the 24-25psi mark. i dont really want to go blasting 2 bar through -5's

the std springs should be fine, there are plenty of people using these cams with std springs. the ramp rate is supposed to be fairly std spring friendly.

at the end of the day, they're still a mild cam.

Brezza Proficient

Brezza

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That will be great - you will be doing a lot of people a favour if you make one mod at a time and dyno after each - you may need to touch up your tune after doing just the exhaust to account for the extra flow. Looking forward to seeing the results - my money's also on the exhaust doing the most but always ready to be proved wrong by hard evidence!

cheers mate!

yeah, i'm looking forward to the results too.

it shouldnt take too long to tickle the tune to suit the extra flow from the exhaust.

i'm lucky that my tuner doesnt charge me heaps for dyno time, cos at the end of the day he can find out what works well too.

i think the exhaust might help the turbo's spool up earlier, but will mainly show a gain in top end.

realistically i think the exhaust might get me 370-380kw

and maybe the cams might pull a little more?

but who knows? i'm not sure how my turbo's will go with the extra flow? i am getting a little puff of smoke after boosting it. its looking like turbo seals

  • 4 months later...
Brezza Proficient

Brezza

Posted
  • Author
Posted

results from changing from 3in turbo back (365rwkw @ 24psi) to a 4in turbo back (372rwkw @ 24psi). there was a problem with holding that boost and the tuner fiddled with the positioning of the actuator arms to try and fix it. the boost was wavy at 24psi.

after the cams it pulled 360rwkw @ 20psi and when pushed to 24psi the boost would be wavy and not gain much more power.

so i've just left it at 20psi.

my view on the cams is that they're great! car still drives nicely and it pulls hard to redline! +1 for type b poncams if you're shooting above 350rwkw, they will fatten midrange and make the car sound better too!

NoFigJamHere Enthusiast

NoFigJamHere

Posted
Posted

Mate change the valve springs!!! Running the boost that your running is showing deficiences in std parts. You will thank me later... Amount of Kms on the engine and whether its been rebuilt would be interesting to know aswell. And anyone in here who thinks otherwise has never built a decent RB engine... The exhaust was the coorect move but i'd have gone 4" with 2.75-3" dump pipes. There no such thing as TOO big an exhaust on a turbo engine chasing power. Also IMO change the cams, if there dialed in correctly and the engine tuned correctly you'll love it.

Shoota_77 Veteran

Shoota_77

Posted
Posted

results from changing from 3in turbo back (365rwkw @ 24psi) to a 4in turbo back (372rwkw @ 24psi). there was a problem with holding that boost and the tuner fiddled with the positioning of the actuator arms to try and fix it. the boost was wavy at 24psi.

after the cams it pulled 360rwkw @ 20psi and when pushed to 24psi the boost would be wavy and not gain much more power.

so i've just left it at 20psi.

my view on the cams is that they're great! car still drives nicely and it pulls hard to redline! +1 for type b poncams if you're shooting above 350rwkw, they will fatten midrange and make the car sound better too!

It's kind of disappointing to not make more power with the new cams but at the end of the day, like you alluded to, it's how the car drives that is the most important. You're already running some pretty impressive numbers so anything bigger is really just a 'mines bigger than yours' exercise imo. I can say that cause you're making a shiteload more than me!! Sounds like a bit of fun!

Any further plans now?

Brezza Proficient

Brezza

Posted
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i got some manifolds to go on, and am also saving for some new dump & front pipes. going to go for a split dump front pipe. 2.5in off ex wheel and 1.5in for wastegate. it's split for at least 40cm then merges back to a 3in twin to the 4in cat back.

hopefully it'll sound good.

it might have a little more grunt? never know. the current setup on there is a 2.5in dump pipe and 2.75in front pipe. i think, havent taken it off to measure.

springs will be too expensive to do since i already paid for the cams to be put in.

in all seriousness, the car has enough power for the street. i'm running federal RSR's and am still spinning tyres on hills runs. there is plenty of power under foot. i'm mainly thinking about changing the exhaust note a little with manifolds and dumps

Piggaz Grand Master

Piggaz

Posted
Posted

i got some manifolds to go on, and am also saving for some new dump & front pipes. going to go for a split dump front pipe. 2.5in off ex wheel and 1.5in for wastegate. it's split for at least 40cm then merges back to a 3in twin to the 4in cat back.

hopefully it'll sound good.

it might have a little more grunt? never know. the current setup on there is a 2.5in dump pipe and 2.75in front pipe. i think, havent taken it off to measure.

springs will be too expensive to do since i already paid for the cams to be put in.

in all seriousness, the car has enough power for the street. i'm running federal RSR's and am still spinning tyres on hills runs. there is plenty of power under foot. i'm mainly thinking about changing the exhaust note a little with manifolds and dumps

Manifolds? As in some stainless rubbish? Dont waste your money.

Shoota_77 Veteran

Shoota_77

Posted
Posted

Sounds good, post up a video of the sound and we'll be the judge!

Mine needs some decent pipes too. Only drama is the main person that you impress upon is the cops! Slipping under the radar isn't a term that applies when you're running that sort of power and pipe volume like what you will be!

34GeeTeeTee Grand Master

34GeeTeeTee

Posted
Posted

It's kind of disappointing to not make more power with the new cams but at the end of the day, like you alluded to, it's how the car drives that is the most important. You're already running some pretty impressive numbers so anything bigger is really just a 'mines bigger than yours' exercise imo. I can say that cause you're making a shiteload more than me!! Sounds like a bit of fun!

Any further plans now?

Well he made similar power at less boost, but the midrange etc should have increased? Is there a before and after Dyno print out/comparison?

I was advised that anything over 20 ish psi i should change the springs and did so seeing it wasnt that much to do they are potentially a 20 year old part and i didnt want to run the risk and neither did the tuner that built my engine :)

I was advised the same, i wasnt going to run 20psi but the same applied.... Old springs and retainers with bigger lift etc apparently the risk isnt worth it.... I went back and forth with this over the past month or so and decided i was NOT going to change the springs and retainers, but after seeing a few horror stories i was quickly steered towards spending the extra $$$

Brezza Proficient

Brezza

Posted
  • Author
Posted

midrange has improved with the cams.

i picked up some second hand manifolds for $200 the pair. so a fairly good price considering what they are new. these ones were off a car and there are no signs of them being welded again from cracks. the guy who had them before went from twins to a single so he didnt need the manifolds anymore.

i'm not going to bother changing the springs now that i've already changed the cams. its not really worth the extra labour $$$, looking back i probably should've changed springs. but to do it now the labour bill would be too much and to maybe gain a couple KW's. i dont know if i can be bothered.

its turning into a p1ssing contest when you're trying to extract more than 350kw from a GTR. you spend more and more money for limited return on more power. and to only say to someone that mine is more powerful. most of the power i have in the car can only really be appreciated at high speeds and on the street you can't do it.

i do respect those opinions from people who have built cars and know what they're talking about, but i'm getting a little tired of everyone regurgitating what someone else says. i hear advice from so many people with less power than me on how to make more out of my car, all they are doing most of the time is spitting up what others have told them.

anyone who has actually driven a 350kw+ car on the street will tell you the same thing, its a lot of power for a street car.

i'll probably update this thread with results after i make changes to the exhaust, but once that's done i will have done every bolt on i can and maybe it'll make more power?

as far as cams go though, the poncams are great. there is a slight difference to low rpm driving (taking off at the lights) but in the midrange they really come alive and do not drop off at high rpm. for anyone looking at pushing a little more out of their GTR when their std cams arent cutting it. the poncams are a great compromise for the street & power.

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