256 RB25 Poncam experiences plz .

[discopotato03]

Hi all , I'm curious to know what you gain and lose in an R33 spec RB25DET with these cams . I've had them for a long time and can't remember what it was like to tune a car for road with standard cams . Earlier on I had a PFC/Z32 and 740 Nismos and GTRS dryer where as now doing a bit better in those areas .

Even so I just wonder what you lose in idle quality and drivability right down low . I know that 256 degree cams aren't exactly wild but the standard ones are from memory 240 and I image timed to have a bit less overlap .

Also I'm curious to know if moving the cam timing around does anything for Poncams , exhaust is easy enough and inlet apparently with a bit of mucking around .

 

Gotta run cheers  A . 

 

 

Cheers  A .

[hardsteppa]

Will tell you in about 2 weeks lol.

[AngryRB]

I doubt you could tell the difference between stock cams and the 256 poncams at idle or down low, I think the exhaust tone off mine was slightly deeper but still smooth.

[discopotato03]

I don't suppose anyone knows what the actual opening and closing points are valve timing wise , I wouldn't mind knowing what the overlap period is .

A .

[Piggaz]

3 minutes ago, discopotato03 said:

I don't suppose anyone knows what the actual opening and closing points are valve timing wise , I wouldn't mind knowing what the overlap period is .

A .

http://www.rhdjapan.com/tomei-camshafts-poncam-rb25de-t.html

scroll down to your engine of choice.

[discopotato03]

From the R33 Engine Workshop manual .

Bear in mind variation in inlet cam timing .

Inlet 0-60 inactive (0+60 +180=240)

Inlet 20-40 early   (20+40+180=240)

Exh 57-3               (3+57+180=240)

These numbers line up with the 240/240 durations and I thing the lobe centers were 120 inlet and 117 exhaust .

Note the overlap timing would be (inactive) 3 degrees and (early) 23 degrees .

A .

[t_revz]

Also I'm curious to know if moving the cam timing around does anything for Poncams , exhaust is easy enough and inlet apparently with a bit of mucking around .

After trying a couple spots and seeing dyno results I'd say to get a decent shift in power earlier I had the inlet advanced so far It had no power at idle. I even had throttle adjusted so low as vct under 1000 would stall.

I now run inlet as recommended. Need to experiment with exhaust timing next time it's up for a tune

[Lithium]

7 hours ago, t_revz said:

After trying a couple spots and seeing dyno results I'd say to get a decent shift in power earlier I had the inlet advanced so far It had no power at idle. I even had throttle adjusted so low as vct under 1000 would stall.

I now run inlet as recommended. Need to experiment with exhaust timing next time it's up for a tune

 

What kind of general idle quality have you had with it at the recommended setting?  Does it sound at all "cammy"?

[t_revz]

What kind of general idle quality have you had with it at the recommended setting?  Does it sound at all "cammy"?

Not noticeable now. It was hunting when warm from 500-1100 when the idle screw was too far in but it's smooth now.

[SilverECR33]

like whats his face said, there aint much difference from idle and down low infact its better everywhere, sure the idle changes slightly cause its larger lift and duration but its not a severe change ...just do it man. u wont regret it!

ps.. wow this place changed alot .. just logged in today and its like a ghost town. saw a few tumbleweeds on the home page..

[Lithium]

Was hoping there might be the slightest hint of "bigger cam" sound at idle, not necessarily lopey or anything but I like being able to tell there is a bit more going on than stock haha.  Was pretty sure performance wise they'd be a bit of a treat  Cheers!

[t_revz]

Was hoping there might be the slightest hint of "bigger cam" sound at idle, not necessarily lopey or anything but I like being able to tell there is a bit more going on than stock haha.  Was pretty sure performance wise they'd be a bit of a treat [emoji4]  Cheers!

Closing the idle screw down I can get it to hunt as hard as a big v8...but I sound like a tool when at the lights and can't take off without throttle

[Dose Pipe Sutututu]

you can nearly make Poncams go "brap brap brap" purely for wank factor.. just drop the idle timing down to about 8~10  and lean out the AFRs hahaha

(everyone reading this, please don't do it)

[Lithium]

I thought that might be the case.  Most of the aftermarket cams I've tuned for have been big enough (read: 280-300+deg) to do it anyway, good to know you can do a bit with wee 256s - thanks, Johnny Dose on!

[Dose Pipe Sutututu]

Suuuuuuuuuuuuuuuuuuuuuuuu tutuutututuuuuuuuuuuuuuuu

Although the braps won't be as distinct as say a set of Procams or 272+

[sneakey pete]

If you want braps get a Perry port 13b.

Smallish cams for maximum boost and therefor more dose is where it's at

[Dose Pipe Sutututu]

dose is king, especially with 6+6 blade compressors!

GTX style compressors don't dose as well

[Lithium]

Each to their own.  Hate dose, love a hearty idle!   If you can get a hearty idle with a small cam, win win.   The cars with huge cams are NA race motors, btw... huge boost and dose don't apply.

[Trex]

Offtopic. Wanted to post this for a while.

 

@Dose Pipe Sutututu

[Dose Pipe Sutututu]

oooo yezz wonder who owns that car?