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Discussion Starter #1
I was going back through the search feature just like at skylinesdownunder to see what you guys think of different cam combinations, which I really could not find any information. Is there a reason for this? On both big Skyline sites, there is not to much info.

Also, running more duration on the intake, is that the norm for the RB26DETT, like in the standard form? I know a lot has to do with your flow numbers on your head, which leads me to another question, what are the flow numbers for the stock head?

Do they make any aftermarket heads for the RB26, or should I just get out the grinder, and start sculpting?

Thanks,
Tony
 

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Tony,

I'd be inclined to tread very carefully when trying to gas-flow... Increasing air volume is all very well but you can end up destroying the air velocity and the deliberate swirl effect of the port. Amazingly a huge number of people don't realise that quite often the ports on a cylinder head are rough for a reason, it is to cause sufficient turbulence to aid the atomisation of the air/fuel mixture. Over polishing can actually ruin a cylinder head.

Admittedly the air velocity is not quite so critical for a Turbo engine as the air is being forced in under pressure, but if you are driving the car on the road it might pay to try and keep the mods to a minimum. I would think Nihon Sungyo-San made the cylinder head the way they did for a reason. If you want more power, wind your boost up a little, its a lot easier than taking the head off :D

However, if you would like to run an RB head on a flow-bench we have one at work (Superflow) which you are welcome to use at a weekend :D Same applies to anyone, wanna gas-flow a head, let me know and the flow-bench is yours :D

Cheers,

Dan
 

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IMHO, finding camshaft information is tough because of a number of factors. For instance:

(1) There are so many other mods that you can do to the GT-R that have a good impact on performance that many people run short of funds before they get to cams.

(2) As mentioned already by DanOh, cams that work well for one person's engine setup are not necessarily right for another person's engine setup. The right cams are highly dependent on a lot of other of the mods performed.

(3) In some cases, those people that are in the know about what cam combinations work best with particular mods on an RB generally don't like to disclose that knowledge. After all, it cost them time and money to come up with knowledge that gives them the competitive advantage.

In regards to duration, most of the tuned GT-Rs I've seen specs for here in Japan appear to have similar duration on both the intake and exhaust. Obviously, I've got no idea about the adjustments they are making through cam gears, etc.

Cya O!
 

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dan0h said:
However, if you would like to run an RB head on a flow-bench we have one at work (Superflow) which you are welcome to use at a weekend :D Same applies to anyone, wanna gas-flow a head, let me know and the flow-bench is yours :D
Dan,

That's a great offer, I'm sure someone will take you up on it sooner or later. :)
 

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Just thinking about this a bit more chaps ... if we could get flow figures for the RB26 head, using the flow data at each 1mm increment of valve lift we can build a flow table that could be used accurately in Dyno2000. This is an engine simulation system very popular in the US and was used by us on our race projects... The results are VERY accurate (within a few HP). More info on Dyno2000 is here---> www.motionsoftware.com

I have the latest release of Dyno2000 and I will build up a basic RB26 simulation, however its accuracy is based on a simplified flow chart unless you have real data, although even on this "assumed" data it is pretty accurate but the obvious step to take is if someone wants to send me an RB26 head, or come down here one weekend and have one flowed we would have the data to make some very accurate predictions of power output changes, and more importantly the effect on power that cam's of differing specs have (if you see what I mean :rolleyes: )....

Dyno2000's most useful thing however is "Iterative Testing", you specify a range of parameters (like IVO, IVC times) and it runs repeat tests over and over again changing these variables within your specified range to see which makes the most power or torque (again in a specified range, for example, looking for max power between 6k and 7k RPM). In short, Dyno2000 is the ultimate cam development tool!

Sorry this is a bit of a ramble but it should make some sense :D

Cheers,

Dan
 

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Discussion Starter #6
Dan,
Thanks for the information, specially the flow bench invite. I personally will not be grinding out the head, until a rebuild, but I am not sure if that will be in the near future or not.

hipo,
"In some cases, those people that are in the know about what cam combinations work best with particular mods on an RB generally don't like to disclose that knowledge."
You got that right. That sort of information in the states is a little more freely given out, oh well. I'll see what my insticts tell me, and go from there.

As for port velocity, I have had some class time on that. I have a little knowledge about it. There are a lot of Red Necks that like to just hogg it out, which we all know is way wrong.

I have come to realize that detailed cam info for the RB26 is Taboo:D I will have to do trail and error to learn myself. I am off to win the Lotto.

I have worked days on my Desk Top Dyno2000, it will get you in the ballpark, but still not realiable.
 

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SkylineUSA said:
I have worked days on my Desk Top Dyno2000, it will get you in the ballpark, but still not realiable.
Hmmm... it was spot-on with our SAAB racing project... Maybe more by luck than maths :D

Good luck with it Tony, sounds like you have your work cut-out what with all the secrecy!

Cheers,

Dan
 

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Discussion Starter #8
Secrecy, not me. I'll squeal like a stool pigeon with a gun to his head, if I get it right.

The Dyno2000, when I change the boost numbers, they do not change the hp nubers the way they should. Or if you over carb the engine the power still goes up. Thats what I was refering too.

Plus, I am months away from dumping big buck into this engine just yet, I need to blow this one first:)
 

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Ahh ok, fair enough ... I must admit that the boost behaviour of Dyno2000 is questionable, I've noticed that too ... we only used it for a normally aspirated engine project :)
 
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