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Poncams On A Highly Modified Rb25? Gains?

ReganGTS25T

By ReganGTS25T,
in Engines & Forced Induction

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shanef Grand Master

shanef

Posted
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can i just bolt on an rb26 head to my rb25 block? it was at 132 mph eh well compared to most rb25's on this forum its pretty well modified atleast brought to the limits of some parts

send him a pm and ask - http://www.skylinesaustralia.com/forums/Di...age-m23582.html

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DECIM8 Grand Master

DECIM8

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Im interested in this thread, it obviously points out porting the head improves alot more than most people say.

Oh cams make a massive difference in offboost to boost performance. I found driving that i'd reach 4g before id change (not so great for fuel) just because it was so torquey.. but IMO well worth it.

Edited by DECIM8
RB30-POWER Mentor

RB30-POWER

Posted
Posted

porting like everything has it disadvantages as well.

opening ports up, decreases port air speed at low rpm and can effect emissions, low rpm torque and fuel economy/efficiency.

not a problem if power is an ultimate aim at the end of the day, but manufacturers have different requirements when these things are cast.

Cjmartz2k Proficient

Cjmartz2k

Posted
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Hey Regan, I just noticed this thread. A popular combo here on Okinawa is 256 poncam for intake and HKS 264 for exhaust. Lets you keep VCT which really helps with spool IMHO. I think you can squeeze a bit more out of that turbo, but not much. I could see 600rwhp, but that would REALLY be pushing it. Biger cams sound sweet though. I'll have to get a vid with my HKS 264's idling and send them to you. You'd probably need a set of valve springs though--I'm running tomei springs and tickling 8k rpm on a regular basis. Peak torque around 7.2krpm though, so shifting about 7.5 is probably best for speed. I think I need a little bit bigger a/r exhaust housing.

For your purposes, the spray might be better, but I just don't know much about N20 on top of a turbo set up. I've heard forced induction cars really like N20 because it acts like a chemical intercooler, but those cylinder pressures must be intense!

ReganGTS25T Enthusiast

ReganGTS25T

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Hey Regan, I just noticed this thread. A popular combo here on Okinawa is 256 poncam for intake and HKS 264 for exhaust. Lets you keep VCT which really helps with spool IMHO. I think you can squeeze a bit more out of that turbo, but not much. I could see 600rwhp, but that would REALLY be pushing it. Biger cams sound sweet though. I'll have to get a vid with my HKS 264's idling and send them to you. You'd probably need a set of valve springs though--I'm running tomei springs and tickling 8k rpm on a regular basis. Peak torque around 7.2krpm though, so shifting about 7.5 is probably best for speed. I think I need a little bit bigger a/r exhaust housing.

For your purposes, the spray might be better, but I just don't know much about N20 on top of a turbo set up. I've heard forced induction cars really like N20 because it acts like a chemical intercooler, but those cylinder pressures must be intense!

lol chris you follow me every where eh? lol yea man i need bang for the buck im goin agianst a zeni tani built r33 vspec with an hks t51 kit at 2.3 bar fully built engine i think you might know about zenitani guy builds fast gtrs then after that i have to run a drag r32 brought from japan 1200 kilo car with 550 awhpwith 2 gt30's, im hoping to get 800+ crank hp out of my car with the gas 2.5 bar and vp c16 i gota loose weight too man im weighing like 360 lbs lol 165 kilos for you aussies i weigh the diference betweena gts and a gtr :banana: to tell you the truth chris ive ran my car with and without vct and i did not notice any diference in spool or power on stock cams next time im on the dyno ill check and see if thiers actualy any diference well with my setup
BoostdR Mentor

BoostdR

Posted
Posted

2 bar at 4200rpm..... hmmmn

as soon as the up the cam spec you will reduce your powerband, increase lag, and loose vacuum. So a daily it won't be. Best bet is to run higher lift and similar duration to stock, step 1.

Adriano Grand Master

Adriano

Posted
Posted

Thats the opposite to what most people have found. I would upgrqade the cams, as im very surprised you arent getting valve issues at 2 bar. Properly dialled in cams will make the turbo come on earlier, and extend the power band, allowing you to reduce the boost to a more efficient level.

WHITER33GTS-T Veteran

WHITER33GTS-T

Posted
Posted
ive got a 409 rwkw rb25det on stock cams with a gt3582 at 2 bar built cp pistons tomei rods greddy intake manifold its also port n polished how much would i gain with some poncams havent found any information on the search engine soo i guess i have to ask heh its either that or n2o i wouldlike the cams but just dont know how much those crapy 256 8.9 lift cams will give me

My old RB25 made 399rwkw @ 17psi with a twin turbo setup running a mix of avgas and pump fuel. It had Tomei cams. 256 inlet and 264 exhaust and Tomei pistons. The rest internally was stock. Just had bolt ons.

I have just built a RB30 bottom end and using my RB25 head with same cams. I want to know what gains I will get my changing the cam timing???

How much do people "advance or retard" the cam gears???

WHITER33GTS-T Veteran

WHITER33GTS-T

Posted
Posted (edited)
Am i reading that correctly? Did you just say you ran 399rwkw on an internally stock RB25?!?!

It had Tomei pistons, stock crank and rods.

1000cc injectors, greddy plenum, 85mm throttle body, Twin T3/T4 turbos, Haltech E11v2, Tomei cams and had a rev limit of 8200

Edited by WHITER33GTS-T
sly32 Proficient

sly32

Posted
Posted

hmmm full boost of 2 bar at 4200rpm, do you have a dyno sheet? i find it very hard to believe, with cams i would go 264deg with solid lifters, dont want anything to big for street as it would be very lumpy, if you want different degree intake to exhaust then you will need cam gears aswell as it will have to be fine tuned.

PM-R33 Grand Master

PM-R33

Posted
Posted
It had Tomei pistons, stock crank and rods.

1000cc injectors, greddy plenum, 85mm throttle body, Twin T3/T4 turbos, Haltech E11v2, Tomei cams and had a rev limit of 8200

Ahh woops, i missed that it had Tomei pistons. But still, thats pretty impressive power on the stock rods.

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