Cams for RB25det

[Sydneykid]

This is getting interesting, so let's see a n/a F1 engine that produces 800 bhp at 18,000 rpm has more mid range than a turbo'ed RB engine? Since horsepower = torque X rpm / 5250 we could do that calculation.

F1 800 = T X 18000 / 5250

T = 254 ft lbs

RB (let's use the Veilside R33 drag car)

1220 = T X 9250 / 5250

T = 692 ft lbs

Hang on, mid range as the name implies, would be half way up the power curve, say 9,000 rpm in F1 engine. I could do that calculation as well but it would be speculation as I don't know the bhp at 9,000 rpm of an F1 engine. But I think the above does the job pretty well.

There is one thing that is being overlooked, the port and valve ratios for a n/a engine are completely different to those for a turbo engine. For example the positive manifold pressure of a turbo’ed engine is impossible to duplicate on a flow bench because they rely on resistance to suction as their measurement, this duplicates a n/a engine.

Moving onto lag, sorry I have problem with larger overlap increasing lag. In fact I believe it is the reverse. The more previously unburnt fuel and air that I burn in the exhaust manifold or turbine, the faster I spin the turbine and the more boost I make. So if I increase the overlap on the exhaust camshaft this decreases the delay to full boost. This is in fact the principle of how anti lag systems work.

A real world example, it is now popular for turbo cars to run a longer duration camshaft on the exhaust than the inlet (256 inlet and 264 exhaust is quite common).

Let's tie the above two examples together, I don't need a big duration on the inlet cam because the incoming air is under pressure and I can use a longer duration camshaft on the exhaust because it isn’t under the same pressure and needs all the help it can get in spinning up the turbo to decrease the lag.

Don't you just love it when a plan comes together.

[GTS-t VSPEC]

Sydneykid,

I agree with what your saying, some people just try and bring in pointless comparison's into what was a good thread.

Maybe we should spend hundreds of millions of dollars like a N/A F1 to develop a better RB head?

Then again that's a stupid idea:p

See'ya:burnout:

[Warpspeed]

Hey Peewee, you have just discovered the relationship between port area and valve area.

This cutting edge technology was researched by R.G. Falls and S.W James in a thesis published in 1941 (at MIT). the title of the paper is "effect of diameter ratios on flow through inlet valves of internal combustion engines". Get a copy and read all about it.

More work was done by Keith Duckworth for Cosworth on combustion chamber design. The current crop of four valve DOHC Japanese cylinder heads are the result of one hundred years of constant research and development by the best engineers available.

All this work is public domain, there are no secrets here. Formula one engine designers do not have secret mathematics, they still operate under the laws of basic physics. Get real.

[Zdenko]

pllleeasassee people u all know my r33gtst will shit al lover micheal's ferrari allrite!!

i dragged him last nite .. shitted all over him

"wank wank wank .. ohh bloww""

that felt good

[Guest Peewee]

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[Guest Peewee]

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[Warpspeed]

Peewee I have read through your post several times, and none of it makes any sense at all. It is in the English language I think, but none of the words seem to convey any meaning.

Are you asking a question, or making a statement ? I cannot even think how to reply to such total rubbish. Are you completely stoned on something, or what ?

Maybe someone else can understand what Peewee is on about, and respond to his post.

[Guest Peewee]

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[Warpspeed]

First I never said RB engines have good midrange, someone else here said that.

But I challenge you to give actual dimensions for the good Formula one head, and the very poor RB head, to prove the 20% difference in valve to port ratio. I want actual figures, because I do not believe you.

Yes I agree with you it is possible to overcam an engine. So what everyone knows that.

[Sydneykid]

Hi guys I believe that "RB engines have good midrange" Maybe the "someone else here said that" was me.

I had an RB30/RB25 that had over 500 ft lbs of torque at 4,750 RPM and it reved to 7,500 rpm. That's good mid range!

We currently have an RB20 that has more than 800 lbs of torque from 96 kph to 150 kph in 4th gear, that's good mid range.

So that's a big capacity RB (over 3 litres) and a small capacity RB (under 2 litres) and they both have top mid range performance.

On a production based turbo engine, port valve ratios are pretty much irrelevant. There are many other factors that have much more influence on how much mid range the engine has. Shoot, I can advance the inlet camshaft, retard the ignition timing and richen up the mixture to knock 25% of the torque. No amount of juggling with port valve ratios will have that sort of effect.

I would prefer to talk about things that matter and things that we can influence than dream about being Mr Goto.

Let's move on.

[Xeron]

peewee is correct on one thing tho, it is very easy to over-cam an engine. Dont go too big kiddies

[meggala]

hm interesting peewee comparing rb motors and F1 motors when you concider the cost difference and the fact that one was manufactuered in the 100's of thousands and the other was manuafactured in the in very small number.

the rb is a good engine for what it is as for cas I'm wondering what effect a smallish set of cams would have on a stockish motor.

also peewee are you aware of the cam specification of the rb 25 we would all like to hear what they are?

zedenko if you are getting cams 2560 or 260's are the way to go and yes you might be beter to loose the vct

meggala

[Guest Peewee]

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[GTS-t VSPEC]

Peewee,

You last lengthy post contained no actual information, what was your point, the fact that you have a mate with a Cosworth?

The point of this thread is what are the best cams for an RB25DET, have you answered the question yet?

See'ya:burnout:

[Guest Peewee]

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