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Cam Advice For 25/30..

bubba

By bubba,
in Engines & Forced Induction

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bubba Grand Master

bubba

Posted
Posted

OK guys, things are progessing quite steadily and am wondering what to do with my cams (am not forking out for huge cams and a solid lifter conversion). Stumbled across this cam info again and am trying to figure out whether to stick with the 25DE cams or whether a combination of 20DE/20DET/25DE cams would be better..

RB20DET

Ex - 240 duration, 7.8 lift, opens 60 BBDC, closes TDC, LCA 120

In - 240 duration, 7.8 lift, opens 5 BTDC, closes 55 ABDC, LCA 115

overlap = 5, LSA = 117.5

RB20DE

Ex - 240 duration, 7.8 lift, opens 57 BBDC, closes 3ATDC, LCA 117

In - 232 duration, 7.3 lift, opens 5 BTDC, closes 47 ABDC, LCA 111

overlap = 8, LSA = 114

(R32) RB25DE

Ex - 232 duration, 7.3 lift, opens 54 BBDC, closes 2 BTDC, LCA 118

In - 240 duration, 7.8 lift, opens 9 BTDC, closes 51 ABDC, LCA 111

overlap = 7, LSA = 114.5

Relevant specs of the engine are:

RB25/30 (R32 RB25DE head)

Stock RB25DE (R32) cams

GT35R 0.82 exh housing

6boost manifold

50mm gate

Rev limit will be 7500rpm and looking at somewhere around 500rwhp. Can someone with a good working knowledge of cams in RB engines please help! :(

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https://www.sau.com.au/forums/topic/266695-cam-advice-for-2530/
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psi Experienced

psi

Posted
Posted

I'm in the same boat!

I have been considering stock RB25DE cams, but.. have no real clues to see if it will help me gain where I want it to gain.

My current plan is to build the engine and get it tuned.. Then go from there.

But that is not very helpful, and is a pain in the butt if it doesn't do what I'm wanting it to do!

bubba Grand Master

bubba

Posted
  • Author
Posted

Have just spent an extra 4k that I wasn't orginally planning to so I'd rather not spend $_$ on new cams unless I can really, really justify it..

Just for some comparison, these cams in this head made 490rwhp @ 22psi with a pair of 2540's.. I've had a mechanical engineer tell me to use the 20DET cams over the 25DE.. not sure on the justification though.

Craked, PM sent.

  • 2 weeks later...
bubba Grand Master

bubba

Posted
  • Author
Posted
i got no secrets!

stock rebuilt rb30 with rb25 non vvt head from r32

gtr injectors

power fc

xr6 35/40

reground gtr cams

Nice!

That turbo has a 1.06 rear yeah? what power are you making and at what boost (and when do you see it?)? :laugh:

Obviously it drives pretty nice going on how happy you were with the cams..

mr_rbman Grand Master

mr_rbman

Posted
Posted

ye it has the 1.06 rear and ideally i would've liked the smaller rear but this turbo popped up at the right price.

it currently makes 251@12psi, only reason i'm not running more boost is i dont have a boost controller and i can't warrant spending more money on a car i never drive. makes that boost by about 4000rpm but because its so torquey off boost it doesn't phase me.

cheers!

Dale FZ1 Veteran

Dale FZ1

Posted
Posted (edited)

Got a couple of variables there you'd need to work on.

What turbine A/R?

What spec are the rods and rod bolts?

The cam specs suggest pushing the effective rev range upwards - ie. moving the torque curve to the right. Turbine housing choice will move your torque curve around as well.

Some who've used the GT3040 suggest it's great/useable/driveable, although the compressor flow is likely to outstrip the turbine flow capabilities. For the higher rpm and power capacity the cam specs suggest, perhaps chase a GT3582, and make sure the bottom end is built to withstand 8000rpm? I tend to think for some applications the XR6-T version is quite a decent match for a RB30DET. Possibly a bit of a soft delivery down lower, but the relative lack of turbine backpressure allows it to hold decent torque as revs rise. Be interesting to see a dyno sheet for mr rbman.

Otherwise recommend putting the specs through a Cam Doctor review and see what the predicted results are :P

Edited by Dale FZ1

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