Aftermarket Camshafts for RB26

[Tommyk]

Hi guys

Im going to be doing some considerable performance upgrades to my stocker

I need some advice as to what I should do for cams. Ive been advised by a workshop to look into cams rather than getting cam gears.

A list of mods going to be done to my car :

Full exhaust system

Power FC

Boost controller

I know theres not much, but apparently you really dont need to do much to these engines to get a fair bit of performance.

Im looking into the tomei poncams, but am really confused by the lift and duration. Ive been advised to get stage 1 cams, but youve got various ones with different types of duration and lift.

Can someone advise me what I should be getting ?

Also, if there are any other upgrades you guys deem feasible (not pod) then please suggest it

Cheers

Tom

[azza_GT-R]

what was theie reasoning for saying no to cam gears, that was to be my next mod and was under the impression that it is one of the best mods to be done also bear in mind for cam gears your looking at $400 - $600 wheras for cams starting at $1000

[Sydneykid]

The Tomei poncams are great for RB25's and I wouldn't use anything else in them. But I have found very little difference (if any) in RB26 cams. Thus far I have developed a preference for Jun, with the 264 duration and 9.7 mm lift for using in a combo (road/race) engine. We use the 272/280 with 10.8 mm lift in the race engines.

They both benefit from adjusting the camshaft timing to suite individual engines, unlike the Tomei Poncams in the RB25's which don't seem to need any adjusting.

[Scooby]

Hi SK;

does that mean you don't think it's worth installing PONCAMs in an RB26 but that adj cam wheels are worthwhile?

[Sydneykid]

does that mean you don't think it's worth installing PONCAMs in an RB26

Oh no, the Tomei Poncams work fine, just no better than others I have used. I like the extra lift that Jun offer for the same duration.

but that adj cam wheels are worthwhile?

Adj camshaft pulleys are ALWAYS worthwhile on RB26's, that has been my experience anyway.

[pnblight]

I put stage 2 poncams 260 deg 9.15mm lift in my gtr as they were the largest lift that were a straight bolt in fit and i bought adjustable cam gears in the kit (A MUST) in my opinion as i would have gain next to nothing leaving them at 0,0deg it wasn't until we tuned the cams on the dyno that they really started to work (i gain over a 100rwhp in tuning cams).

SK did the june cams require head mods to fit the 9.7mm lift ?

The poncams are awesome go stage 2 and wheels and you will not regret it ,plus they are very easy and cheap to fit.

[JXL]

are the GTR cams already a higher standard of cam than those found in the rb25.bita newbie at the quality of all the parts in there.

i bought my R33 RB25DET with what was supposed to be upgraded cam shafts supposedly tomei but i am yet to have the cams taken out to check for sure. wasn't a factor in the purchase anyway, got a decent price and the car was in excellent shape all round.

i got my car checked out at nissan before i bought it and they were under the impression the car had more aggression through the revs than it would standard and more than what a airpod, full exhaust and BOV could provide for it. (they were on aswell)

when i do get around to having a look on them is there a code number anywhere on their to check for sure??

[Sydneykid]

SK did the june cams require head mods to fit the 9.7mm lift ?

If you mean machining, no we get 10 mm before I have to spend 10 seconds for each lobe slightly relieving the casting. It's no big deal, I did the clearance for the 10.8 mm lift Jun 272/280 cams in less than 20 minutes with the die grinder. That included set up and wash up time, piece of cake.

If you mean valve springs, I always change them in RB26 cylinder heads. The standard springs are too soft for my taste, not enough seat pressure. At the very least I would shim them up.

[pnblight]

If you mean machining, no we get 10 mm before I have to spend 10 seconds for each lobe slightly relieving the casting.  It's no big deal, I did the clearance for the 10.8 mm lift Jun 272/280 cams in less than 20 minutes with the die grinder.  That included set up and wash up time, piece of cake.  

If you mean valve springs, I always change them in RB26 cylinder heads.  The standard springs are too soft for my taste, not enough seat pressure.  At the very least I would shim them up.

yes i was talking about lobe clearance thanks, SK

What clearances would you remend or do you stick with the std clearance

And do you have a preferred brand when upgrading valve springs

[Tommyk]

I just spoke to matt (hitman tuning guy) at penrith over the phone.

He suggested I shouldnt be bothering with cams + gears unless i get larger than stock turbos.

Im just trying to justify whether the extra tuning cost $2-300 for cam gears and the extra cost $400 in purchasing two cam gears is worth the performance increase. Is there even any point in purchasing tomei 260/260 9.1 cams over the stock units? These are attainable for about $900

Cheers

Tom

[7heavn]

I've got 2530's on my GTR with stock cams and find 0/0 to be the best setting so far . I have adjustable cam wheels on the front of the motor but they were bought by the previous owner and he had them installed at a certain workshop in Sydney .

When I became the owner of the car I first ran it up on a dyno and the results weren't very impressive at all 275rwkw @1.2bar and an outing to WSID proved even further that something was a miss . So being upset at this point and not knowing the reason for lack of power even though the motor proved to be healthy I let Ben and Eric from Bel garage loose on it and the main problem became evident both wheels had a great deal of advance . After they were pulled back to 0/0 Ben took it out for a tune of the power FC and basically now I'm making the same power as before at only 4500rpms .

I have read and heard of other people getting good results with adj cam wheels on std cam rb26's but I can only go off what I've actually seen with my own eyes . Differen't ppl and workshops have differen't opinions with cam wheels and there settings.

[Ronin 09]

Tom - this is the dyno graph from last week when I had Poncams 260 9.15 installed.

I like the midrange. Will try and scan up the torque graph tonight.

Mods are:

*turbo back exhaust

*power fc

*cam gears

*1 bar boost

*std airbox (not a mod, but vs. pods), std turbos

[Tommyk]

WOW

That looks good.

Do you know what it looked like BEFORE you got the poncams installed ?

[Ronin 09]

haha dammit wish I had run it before getting the cams in! everyone keeps asking that

I know that some other guys on the forums with the similar mods MINUS cams make around the same peak power, so if anyone has a dyno of an R32GTR with FC tuned minus the Poncams, pls post it so I can lay one over the other and give a better picture of what the cams have done to the midrange.

...would be very much appreciated

[Tommyk]

Ive done a bit of trawling through old threads

SK : mentioned this

"If you intend to use 7,000 to 9,500 rpm, something around 272 to 288 degrees would be the go. For 5,500 to 8,000 rpm, around 260 to 272 and for 4,500 to 7,500 rpm then 248 to 260 is the go. That's a simplification, but you get the idea."

Now, the standard cams are :

Intake: 240 duration w/ .338 lift (8.58mm)

Exhaust: 236 duration w/ .326 lift (8.28mm)

Does this mean that they will give better power down low ?

If I want better power down low, does it mean I should look at cams with a smaller duration? or am i just simply confused ?

Thanks guys

[Sydneykid]

Ive done a bit of trawling through old threads

 

SK : mentioned this  

 

"If you intend to use 7,000 to 9,500 rpm, something around 272 to 288 degrees would be the go. For 5,500 to 8,000 rpm, around 260 to 272 and for 4,500 to 7,500 rpm then 248 to 260 is the go. That's a simplification, but you get the idea."

 

Now, the standard cams are :

Intake: 240 duration w/ .338 lift (8.58mm)  

Exhaust: 236 duration w/ .326 lift (8.28mm)  

 

Does this mean that they will give better power down low ?

If I want better power down low, does it mean I should look at cams with a smaller duration? or am i just simply confused ?

 

Thanks guys

You can't leave lift out, you could support the argument tha tthe higher lift (9.2 mm versus 8.2 mm) adds more to the mid range than the longer duration takes away. The concept of improving mid range on a small capacity turbo engine is to get more boost sooner. That means efficiency improvements, all the usual stuff needed to get the air in and out as efficiently as possible. Higher lift is a very good efficieny improvement.

My usual example, we have an RB25DET that makes 265 rwkw, but the important thing is it has more power EVERYWHERE than standard. From idle to rev limiter the efficiency improvements help the not overly large turbo (GCG ball bearing hi flow) to produce boost at low rpms and yet still have sufficient airflow for its rated capacity (450 bhp). It's all about average power and an 11.9 at 120 mph is testament to the effectiveness.

The real secret is to get the components all matched up to suite the power curve that you want. For example it would be a waste of time (and a lot of money) trying to get improved low down power from a turbo that doesn't produce boost until 5,000 rpm.

Then it is down to the full rpm range tuning, I see plenty of engines that are perfectly tuned from 6,000 rpm to to rev limit, but are truly crap under that. So it is important to talk to your tuner about what YOU want, not "drop it off and come back later" expecting a perfect job. Remember what might be "perfect" for you, may well be "terrible" for someone else.

Hope that helps:cheers:

[Ronin 09]

SK, your thoughts on my dyno curve?

[Sydneykid]

SK, your thoughts on my dyno curve?

Bloody fantastic, 150 rwkw at ~3,750 rpm is impressive. It appears to run out of airflow a little bit over 6,500 rpm, what's the boost curve look like? I am now used to looking at N1 turbo dyno graphs, your standard turbos are pretty much on the mark from memory.

[Scooby]

Ronin,

That's a great curve - looks to be a perfect street set up, linear as hell, almost like stock but just higher up the graph! That's what I'm hoping for.

Well done. From memory you have the Trust elongated dumps?

PS

Your choice of course but I reckon leave it like that, don't wreck it by being

greedy LOL!

[Ronin 09]

Bloody fantastic, 150 rwkw at ~3,750 rpm is impressive.   It appears to run out of airflow a little bit over 6,500 rpm, what's the boost curve look like?  I am now  used to looking at N1 turbo dyno graphs, your standard turbos are pretty much on the mark from memory.

I don't have a print out of boost & power vs speed, so can't answer that question. I would be guessing that the stockers are pretty much on the limit at or around 250rwkW in terms of airflow...

What sort of improvement could I expect with N1s? 2530s? GT-SS?