How Much Of A Difference Higher Lift Makes ? + Camshaft Duration

[XKLABA]

I still have the type Rs in the car now with a 3.0 and HKS GT-RSs making 458awkw and it makes positive boost pressure under 2k RPM

Love a 3.0

[cobrAA]

I still have the type Rs in the car now with a 3.0 and HKS GT-RSs making 458awkw and it makes positive boost pressure under 2k RPM

Love a 3.0

that's interesting!! That would means theres no such thing as too small duration ( but then again, we can't make bold statement on simply one exemple.. lol). how big is your exhaust, intake piping ?

I see HKS paired their gtrs ( which should flow about 80lbs of air just like the EFR 83/74) with 264 cams ; http://www.hks-power.co.jp/en/product/turbo/actuator/gtrs/index.html

Edited October 6, 2014 by cobrAA

[XKLABA]

that's interesting!! That would means theres no such thing as too small duration ( but then again, we can't make bold statement on simply one exemple.. lol). how big is your exhaust, intake piping ?

I see HKS paired their gtrs ( which should flow about 80lbs of air just like the EFR 83/74) with 264 cams ; http://www.hks-power.co.jp/en/product/turbo/actuator/gtrs/index.html

Intake is factory except for the 105mm monster ARC intercooler and twin turbo pipe mod, exhaust is twin 3" with twin 3" cats into a single 4"

Compressor maybe but not exhaust, the GT-RSs have to small of a turbine wheel which means the manifold pressure has to be to high to make the same boost level

[KiwiRS4T]

Since I'm no expert on cams I would buy one from Kelfords rather than Tomei because Kellfords make a lot of custom cams and if you tell them what your set up is and what you want from it I would suggest they would supply the right gear.

[Lithium]

but then again, we can't make bold statement on simply one exemple.. lol

If you know that much you can mock my thoughts and my accent, why are you asking anything at all?

This is the kind of thing that had me reduce the amount of involvement I had on these forums, and now why I am no longer going to be posting on here after this- it's my issue but I can't help but find it somewhat irritating when is a topic which has potential for good conversation among people who have good things to offer, you get mouth breathers mocking anyone who has a different view to offer to themselves... reminds me of the Bedford level experiment, and associated topics. People too often just don't learn how to learn, but instead learn something and proclaim that something as everything using the same evidence which suggests there is more to consider as proof that it's all there is to consider. Listen to Xklaba, he knows more than you - and seems to be be less disillusioned than me. Try and keep a more open mind, you have a shitload to learn... that much that it seems you can't even see it and don't feel like there is any reason to look.

Xklaba, may see you sometime in the near future

I'm out!

[djr81]

That's what Kelford advertise, yes. Do you reckon they are lying, or wrong? What I am guessing from what they suggest in that blurb is aside from being a cammy at low rpm it's likely to have a hell of a power delivery. I haven't tried that exact cam profile so am not going to state exactly what it will perform like as fact, but on the flipside I have been involved with a few cars using Kelford cams and know that they probably know a lot more about cam design than I, and probably everyone in here, I know that their cams have always done exactly what they said they would in the cases I have been exposed to, and they tend to perform a lot better than equivalents from other brands I've seen mentioned here in cases I've seen where people have upgraded to them. I'd venture to say that comparing advertised duration and lift between Kelfords and Tomeis to guess power & delivery would be like comparing compressor sizes between Precision Gen2 CEA turbos and Turbonetics T-series to determine the same.

When you said Halford - were you talking about Kelfords? Either way, totally agree with the caveat. Goes beyond that too, the opening/closing of valves and some stuff you probably can't tell from specs will have an influence on the performance and at the end of the day unless you have some serious experience or at least theory with engine / cam design it's probably a lot safer to take into account the manufacturers description and advice on the different models to set expectations instead of casual glances at advertised lift and duration to pigeon hole cams of completely different brands and designs together... which is a lot of why I piped up in this thread.

I'm no expert in this, but I know enough to know I don't know enough to tell people how cams I've not experienced first hand are going to perform with any kind of confidence from those two numbers - I suspect most others are no more qualified, if not less to make that call. I don't mean that to be rude, I'm just pointing out that it's probably something better to go more by peoples results... ideally with the same kinds of setup overall as you are going to be using, that's probably the best way to go about choosing cams.

Just my thoughts, anyway. I should highlight the "I'm no expert" of course, if there is one in here - this would be a great place to add more if they were so kind

Not saying they are lying, not saying they are wrong. Just saying I don't (necessarily) believe all marketing information fed my way. For example, despite all the promises I am less than refreshed after my last beverage so who knows.

Cams are, more than most things, an exercise in matching lift/duration to all the other stuff you have going on (rev range, turbo, bore vs stroke, CR, fuel etc etc etc). A 272 may be an absolute weapon on an RB30/26 but hopeless on a 26. I don't know I haven't tried one. My limited experience was to go from Poncam B's to a 256/252 combination on a 26. Car made less power on an extra pound boost but was quicker. The biggest difference was in the low to mid range. So based on that extrapolating to 272 I cant reconcile it with what I had.

Longer duration move your torque up the rpm range, which is more power. Careful cam selection can get you a wider torque curve which is what everyone is chasing.

My rule of thumb on an RB26 test is how much power is made at 4000rpm. If it is thereabouts of 200 or more then response is pretty good. Much less and it is a bit hopeless. That is with petrol. E85 is different.

The caveat was just to remind people that duration is measured at a small amount of lift. How much lift affects how much duration. Something to be mind full of so everything is apples and apples.

Ultimately if shorter duration made more horsepower you would keep stock cams.

[Ben C34]

Some great thoughts on here.

Let's over simplify things rather than complicate them.

A naturally aspirated engine makes its power due to the cam and head combo.

A turbo car makes its power due to the turbo, followed by cam and head. That's where the confusion comes in, another variable, even when simplifying it.

As per some here, I know enough about cams to know I don't know enough. It's full on. To put it in perspective a mate who is full on into drag racing (v8 big blocks) very recently paid 5000 for a cam. Is a cam itself ever worth that? No. It's the knowledge behind the cam. This is a smart dude who's knowledge and dedication and experience is immense, and he still spent the cash for someone else's knowledge on the cam. He didn't try to design his own because he knew he didn't know enough. When he got the cam he rang the supplier (In the states) as he was surprised as the cam seemed smaller than he was used to. Sure enough it was a winning setup that shouldn't have been doubted, although on paper most would have looked elsewhere.

Also As mentioned , advertised duration doesn't really mean jack, and it's the subtle differences in ramp rate etc that make all th differences, which is not reflected until it is used. And who ever changes a cam only on a turbo car and retunes for comparison? I would love to see it but most wouldn't bother, usually it's multiple changes and once.

Edited October 7, 2014 by Ben C34

[Skepticism]

If you know that much you can mock my thoughts and my accent, why are you asking anything at all?

This is the kind of thing that had me reduce the amount of involvement I had on these forums, and now why I am no longer going to be posting on here after this- it's my issue but I can't help but find it somewhat irritating when is a topic which has potential for good conversation among people who have good things to offer, you get mouth breathers mocking anyone who has a different view to offer to themselves... reminds me of the Bedford level experiment, and associated topics. People too often just don't learn how to learn, but instead learn something and proclaim that something as everything using the same evidence which suggests there is more to consider as proof that it's all there is to consider. Listen to Xklaba, he knows more than you - and seems to be be less disillusioned than me. Try and keep a more open mind, you have a shitload to learn... that much that it seems you can't even see it and don't feel like there is any reason to look.

Xklaba, may see you sometime in the near future

I'm out!

I get the feeling this was a typo.... ?

Judging by the general tone of the post + the typo frequency in cobra's posts

[djr81]

Sooooooooo...... Does anyone know what lift the Tomei cam's duration is measured at?

[Ben C34]

Sooooooooo...... Does anyone know what lift the Tomei cam's duration is measured at?

Advertised duration means nothing. And that's what's quoted....

On the type b neo cam card it has the duration at 1mm so I assume it would be able to be found on google for the 26.

[djr81]

So would I. But I couldn't find it.

Tomei:

Type

Application

Duration(IN)

Duration(EX)

lift(IN)

lift(EX)

Part number

MSRP(USD)

A

BNR32,BCNR33

260°

252°

9.15

9.15

143036

$580.00

BNR34

143037

B

BNR32,BCNR33

260°

260°

9.15

9.15

143005

BNR34

143018

* Type A
Designed to best suit the stock & N1 turbos for optimum performance balance of low to mid range torque.
The Exhaust cams duration was reduced to maintain best idling.
* Type B
By extending the duration timing compared to the Type A Poncams, both response and peak power was raised and these camshafts best compliment the mid to large size turbo charged applications.

Kelford: 182 cam, notionally a 272 degree cam at 0.35mm lift.

Duration @

1.00mm VALVE LIFT

Intake:

234

Exhaust:

234

Timing @

1.00mm VALVE LIFT

IVO:

7 BTDC

EVO:

53 BBDC

Just trying (and failing) to reconcile the two. Just like I failed with the google. Mostly returned Kasabian references.

[Ben C34]

http://lmgtfy.com/?q=tomei+rb26+cam+specs

3rd result

[djr81]

Cheers dude.

At 1mm you get:

Poncam A

Inlet: 226 degrees.

Exhaust 218 degrees

B

Inlet 226

Exhaust 228

note: despite them both being a nominal 260 degrees on the same lift the get different numbers at 1mm lift.

256 camshaft:

Inlet 225 degrees

Exhaust 223 degrees.

Compared with 234 degrees for Kelfords 182. So the Kelfords is still quite a bit bigger.

Edited October 7, 2014 by djr81

[GTSBoy]

Any duration at 0.35mm lift is broadly equivalent to the total duration or "at seat" duration.

The absolute gold standard for advertised cam duration is 50 thou of an inch. 1.27mm. Metric peoples like the Japs may well use 1mm instead.

No-one ever should ever ever ever compare cams based on the total duration because you can hide a hell of a lot of duration between zero lift and 50 thou if you have a gentle ramp rate, or you can fit a hell of a lot of flow into that low lift gap if you have a savage ramp rate - and of course you can then fit a lot of lift in between the 50 thou points. Even worse - two cams can have exactly the same duration at 50 thou, exactly the same lift, and totally different performance, based on how rapid teh ramp rate and the dwell near full lift. The cam with more area under the curve would be the one with the shorter total duration too, just to further confuse the issue. The main decider (IMHO) is the dwell near full lift. I used some cam profiles for my ALFA many many years ago based on Pat Braden's work. His were huge lift (like 13mm) and I backed off on that but kept a lot of the savage ramp rate and wide lobe top he had. Took good springs to keep them on the buckets, but they worked a treat. They had less total duration than most hot ALFA cams but made better power. The tops of them were so wide they looked flat, almost as if they had two peaks.

[zebra]

Any duration at 0.35mm lift is broadly equivalent to the total duration or "at seat" duration.

The absolute gold standard for advertised cam duration is 50 thou of an inch. 1.27mm. Metric peoples like the Japs may well use 1mm instead.

No-one ever should ever ever ever compare cams based on the total duration because you can hide a hell of a lot of duration between zero lift and 50 thou if you have a gentle ramp rate, or you can fit a hell of a lot of flow into that low lift gap if you have a savage ramp rate - and of course you can then fit a lot of lift in between the 50 thou points. Even worse - two cams can have exactly the same duration at 50 thou, exactly the same lift, and totally different performance, based on how rapid teh ramp rate and the dwell near full lift. The cam with more area under the curve would be the one with the shorter total duration too, just to further confuse the issue. The main decider (IMHO) is the dwell near full lift. I used some cam profiles for my ALFA many many years ago based on Pat Braden's work. His were huge lift (like 13mm) and I backed off on that but kept a lot of the savage ramp rate and wide lobe top he had. Took good springs to keep them on the buckets, but they worked a treat. They had less total duration than most hot ALFA cams but made better power. The tops of them were so wide they looked flat, almost as if they had two peaks.

This

So much This

Ideally you should have the head on a flow bench, find out the lift where the flow drops off and choose your lift off that.

Then get the highest/fastest ramp rate that you are comfortable with...and whether you can get springs to control it.

[djr81]

Yeah the Tomei stuff reads as 50 thou or 1mm - which goes to show they are sh!t at conversions.

Harsh ramp is a killer of valve trains as well as high lift, just not so much on RB's?

[zebra]

Well yes it is

But you can either have the performance or you can have 200,000k rebuilds

[The Bogan]

What about overlap, from my understanding the overlap is just as important as lift and duration.

[GTR_JOEY]

Advertised duration means nothing. And that's what's quoted....

On the type b neo cam card it has the duration at 1mm so I assume it would be able to be found on google for the 26.

Any duration at 0.35mm lift is broadly equivalent to the total duration or "at seat" duration.

The absolute gold standard for advertised cam duration is 50 thou of an inch. 1.27mm. Metric peoples like the Japs may well use 1mm instead.

No-one ever should ever ever ever compare cams based on the total duration because you can hide a hell of a lot of duration between zero lift and 50 thou if you have a gentle ramp rate, or you can fit a hell of a lot of flow into that low lift gap if you have a savage ramp rate - and of course you can then fit a lot of lift in between the 50 thou points. Even worse - two cams can have exactly the same duration at 50 thou, exactly the same lift, and totally different performance, based on how rapid teh ramp rate and the dwell near full lift. The cam with more area under the curve would be the one with the shorter total duration too, just to further confuse the issue. The main decider (IMHO) is the dwell near full lift. I used some cam profiles for my ALFA many many years ago based on Pat Braden's work. His were huge lift (like 13mm) and I backed off on that but kept a lot of the savage ramp rate and wide lobe top he had. Took good springs to keep them on the buckets, but they worked a treat. They had less total duration than most hot ALFA cams but made better power. The tops of them were so wide they looked flat, almost as if they had two peaks.

Thank fek... Someone actually made some sense and got their point across effectively

[Ben C34]

Yeah the Tomei stuff reads as 50 thou or 1mm - which goes to show they are sh!t at conversions.

Harsh ramp is a killer of valve trains as well as high lift, just not so much on RB's?

They quote 50 thou and 1mm. They are different values. They know what they are doing