Time For Camshafts

[OMGGTR]

pro cams. pretty sure they come in a 260 degree with the small base circle

Yeh they do 260deg 10.25mm thats what i want to get but im just making sure its a ok option....

but im told the mines set was the better option .. thats where im at so far....

[SS8_Gohan]

i've got 256's in mine, 2530 turbo's so an ever so slightly bigger turbo from what people say. She's responsive for the setup, but -5's/2530's aren't ever going to be that responsive on a standard displacement 26.

They are Midori camshafts, can check those out as well perhaps.

[rob82]

Depends on how much power your street car is making and what the turbocharger configuration is.

rob82...why do you want overlap for at low revs with a highly restrictive exhaust side?

Positive overlap only becomes an issue at high rpm when the exhaust back pressure increases. Plus I wouldn't call -5's on a 26 being overly restrictive!

What do you think an rb25 cam phaser does - increases overlap lap by advancing the inlet cam between 1400 and 4700rpm (low to medium revs)

Evo9 does the same but has varying angles

Avcs equipped wrx's does the same but varying angle

Dual avcs (09sti) advance inlet and retard exh to increase positive overlap

Now some of the STD ihi turbos on the STD wrx's is what I would call a restrictive exhaust side. With free flowing exh we can generate 14psi at 2000rpm rev limited at 6700rpm!

[Rolls]

The purpose of increasing overlap at low rpm is to increase speed and hence VE yes?

[bigmikespec]

Positive overlap only becomes an issue at high rpm when the exhaust back pressure increases. Plus I wouldn't call -5's on a 26 being overly restrictive!

What do you think an rb25 cam phaser does - increases overlap lap by advancing the inlet cam between 1400 and 4700rpm (low to medium revs)

Evo9 does the same but has varying angles

Avcs equipped wrx's does the same but varying angle

Dual avcs (09sti) advance inlet and retard exh to increase positive overlap

Now some of the STD ihi turbos on the STD wrx's is what I would call a restrictive exhaust side. With free flowing exh we can generate 14psi at 2000rpm rev limited at 6700rpm!

I tend to disagree epecially if you want to make more than 500hp.

The reason for advancing the intake cam is to close it earlier is supposed to increase cylinder pressire to improve responsiveness and help low end torque. Anyway, unless you are adapting VCT it is pointless to discuss this.

Small duration and high lift then?

[The Dan]

-5's are not small turbos. I would put them in the 35R - T04Z category of which 270 degree @ 50 is usually spot on. In fact put 290's in there and I guarantee you will not do anything but make hp and make it sound angry. Yes idle vaccum is 0 but if your tuner is good this won't really matter.

260 and 270 on the cams you mentioned are perfect for the setup. 10.25 mm lift is spot on.

When your head guy relieves the area beside the bucket for the lobe clearance, just make sure he doesn't go too deep and only take off enough to clear. Too many times I see people have so much take off in this area and they go too deep down the bucket area. The side load on the buckets are huge at this point, especially at high rpm. Removing too much will actually cause the bucket to wear and possibly seize in place

[The Dan]

Also supertech to replacement buckets for about $20 each I think. They are also lighter than factory and can be used on reduced base circle or standard. You just need to tell them which you are using.

[bigmikespec]

-5's are not small turbos. I would put them in the 35R - T04Z category of which 270 degree @ 50 is usually spot on. In fact put 290's in there and I guarantee you will not do anything but make hp and make it sound angry. Yes idle vaccum is 0 but if your tuner is good this won't really matter.

Yes compressor flow however you are not taking into account the restrictive hot side. Sorry, when I mean small I should be specific and say restrictive exhaust side. Measuring exhaust manifold back pressure and boost pressure will tell the story.

[The Dan]

Yes compressor flow however you are not taking into account the restrictive hot side. Sorry, when I mean small I should be specific and say restrictive exhaust side. Measuring exhaust manifold back pressure and boost pressure will tell the story.

I wasn't referring to your post. You are right though, they are restrictive for the size but still a 260/270 setup I think would be optimal

[OMGGTR]

well im going to go with the 270 10.25mm i want a nice note aswell so its a must lol...ive also learned some new tricks in my build such as port matching my block and head to the head gasket which i havent done and also installing a head oil drain kit from spool imports this will now save me having to pull the engine out again... oh cant forget the 1mm restrictor and blocking the rear gallery off, so many secrets!

[R31Nismoid]

You don't need external drains if you are enlarging the returns and using restrictors.

No GTR down here needed them, even @ PI.

[discopotato03]

My views on variable cam timing .

The idea of what I call opening the cams means moving one or both in the opposite direction to reduce valve overlap in the scavange phase . What this does is increase the cylinders "trapping efficiency" ie you cant lose compression pressure out of valves that are not open - in a healthy engine that is .

High performance engines with fixed cam timing have to compromise ie something thats livable low down whilst breathing well enough in the middle and higher up .

To have the best of both worlds you need very short overlap valve timing low down and increase it as the revs and load rise .

This is part of the way the broaden an engines usefull power range by increasing the engines torque down low whilst having things sized to make it breath well in the mid to high rev ranges .

I don't think this was Nissans intention with RB26's which is why they don't feel that torquey down low . I'm actually surprised the HKS VCT mod is not more popular and available from other suppliers .

For whatever reasons Nissan didn't do much more development with the RB26 after R32s , they obviously didn't think it was worth their while to improve the head and valve train like they did with the RB25 Neo and Mitsy did with the MiVec 4G63T engines . In a perfect world RB26's would have VCT on one or both cams to compliment the ITBs and a properly developed TS single turbo - for a production type 225 Kw engine .

Note the RB25 Neo had on paper almost R32 RB26 power levels and with the same inlet and a decent TS turbo it could have done better .

Mitsy changed a few things on on the Evo 9 notably the larger TS turbine housing and larger diffuser size compressor housing . The real RS got a Titanium alloy turbine and a Megnesium alloy compressor wheel . The head had smaller diameter long reach spark plugs and improved cooling jackets around the hot side of the chambers and exhaust ports . Both aimed at detonation resistance so they could run from memory 19 pounds of boost std on less than ideal fuel .

The combination of more detonation resistance/free breathing turbine housing/more boost/better cylinder trapping efficiency showed up as a broader spread of torque starting not very far up the rev range .

People say you can run quite healthy cams in these engines and not cop the reversions grief fixed cam timing engines have when you do this to them .

Anyway same deal as Nissan , car getting heavier with all the greenie mod cons whilst the engines capacity remained the same . Needed more low to mid range torque to haul the pork .

Anyway with RB26's you have to strike a compromise because without VCT or capacity increases you won't get the wide spread of torque needed to drag around one and a half tonnes and have it feel good everywhere .

My ideal would be std or mild cams to make it run nicely ie maybe 256s and GTSS type turbos to give it strong mid range torque .

I don't give a rats ass about power numbers or how high it revs because high numbers and peaky power characteristics make a road car useless in my book . When the east coast speed limit is 110 and on expressways only where can you use peaky power ? If you build impractical states of tune whos fault is it when its a PITA to drive around town ?

A .

[GTR_JOEY]

thats it you convinced me.... 2.8 stroker with V-cam for the next build

[Rolls]

Or just settle for a neo with VCT and a 3L bottom end.

A lot cheaper!

[GTR_JOEY]

This is true, had to cut out some of the bonnet cause of the turbo already so 30 will make it worse..

Suppose u could convert the neo head to solid lifters

Surely hks v cam is bet then the VCT in the 34's

Edited December 31, 2011 by GTR_JOEY

[Rolls]

neo is already solid lifters

[GTR_JOEY]

Well there u go, learnt something today

[Piggaz]

thats it you convinced me.... 2.8 stroker with V-cam for the next build

Yeah it would be nice.... and hopefully make up the 7.3 mm of stroke compared to the 3 litre.

[N1GTR]

[GTR_JOEY]

Haha yea maybe