Good day at Emerald

[I.Mupferit]

Well it is if the Chinese can find enough takeaway dishes to recycle into new cylinder heads and crankcases. 😬

 

Edited to say: reply to David W (obviously)

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

 

Edited by - Brent Chiswick on 26 Apr 2006 11:23:56

[Nifty]

Oily,

 

Is this a yellow car and was it being pulled by an MG hatchback .. if so you passed me heading towards Watton (I was heading towards Thetford) near East Wretham Camp .. I flashed but I wasn't acknowledged .. not surprising since I was in the Landy.

 

Keep off the straight and narrow 😬

[oilyhands]

Nifty,

 

Spot on.. it was indeed a yellow cart being towed by an MG hatchback.. well spotted.

 

Oily

[Peter Carmichael]

I would have thought it comes from the amount of energy you can release from the fuel.

 

Cripes. I've started thinking about this as one of "those" discussions where detail definitions come into the picture and I feel a long post coming on. Most of my comments are made in the context of natasp engines.

 

Bhp comes from the rate at which you can convert energy in fuel into usable mechanical power. The energy conversion is a well-understood process, achieving very similar brake specific fuel consumption in most configurations of four stroke engines. This is often stated as the rule of thumb,"half a pound of fuel per horsepower per hour", and is used in injector sizing.

 

(There are so many factors ignored by this rule of thumb I'm not going to elaborate other than to say it is good enough for most of our purposes.).

 

Because we know the combustion process also requires a narrow band of air:fuel ratio, we know the rate at which air needs to be processed through the four stroke cycle - the airflow through the engine.

 

I'm going to use 12.5:1 as the A/F ratio for the engine in question producing 263.7bhp (presumed accurate), resulting in an air requirement of 10,700 litres per minute of air at ambient atmospheric pressure. Filling the cyclinders with 1.9 litres of air in each cycle would mean 5632 cycles per minute, each cycle consists of two crankshaft rotations and therefore 11200rpm. To achieve this cylinder throughput at 8850 rpm means that the engine is pumping 2.4 litres of air in each cycle, which is achievable because of the overlap and timing of long duration cams. When your engine is not yet on cam it is pretty much processing air at ambient pressure. When your engine comes on cam the resonances in the air flow compress the air into the cylinders, giving this gain in effective pumping capability.

 

The calculations at peak torque for this engine suggest the engine is processing 2.65 litres of air per cycle from just 1.9 litres of swept volume.

 

The point of all this elaboration is that it doesn't really matter how you flow the 10,700 litres of air per minute, just as long as that quantity of air flows. When oilyhands does his porting work it is so that you get a set of ports that can flow 10,700 litres of air in a minute rather than ones that just flow 10,200 litres, say. The port design will serve a short stroke engine running double the revs or the long-stroke of the K.

 

Oily's tuning of the K series raises some interesting questions. We are accustomed to thinking about bike engines as getting lots of power from not a lot of engine and being a coherent package for track use with a gearbox thrown in. We are thinking these days about Duratec engines with their thumping torque delivery and the potential for very high power outputs from a larger number of litres. The K is a bit in the middle. It seems you can damn it for not producing as many bhp/litre as a bike engine and equally you can damn it for not producing as much bhp as a large capacity Duratec. The truth is that all of these engine designs share a basic thermodynamic cycle and share basic limitations.

 

The Hayabusa and K share very similar bore dimensions, although very different strokes (63mm vs. 89.3mm), which means the limits in power potential will come from more fundamental things such as the shape of the basic head casting, how much downdraft there is on the inlet ports etc.

 

If you got a short throw crank and a set of rods and matched it to a Dave Andrews K-series head, you might well get a 250-260bhp 1.3 litre engine and no question would arise about bhp/litre.

 

In short, bhp/litre is a meaningless comparison fobbed off on us by lazy journalists and marketeers and other sources of received wisdom. Most people quoting bhp/litre figures are trying to sell something or justify why they've spent more money than sense would advise. By meaningless, I mean you need to add allowance for other parameters before a meaningful comparison can take place; those parameters depend on your purpose in the comparison - either assessing the quality of tuning work and whether there is further potential in an engine design, or comparing the potential of different engine designs.

 

Edited by - Peter Carmichael on 27 Apr 2006 13:46:01

[oilyhands]

Calm down Peter :-))

 

Oily

[Tight fart]

In short, bhp/litre is a meaningless comparison

 

Not to anybody who competes with a capacity limit it isn't. The engine capacity is the basis for nearly all racing classes, getting as much out of what you have is paramount.

 

I have some of Keith Duckworth quotes that fly in the face of your theorys but I feel I'd better dig them out and get them word perfect If I am going to survive here 😬

 

www.tightfart.com

A7 RDP pics here

[Tight fart]

I feel like I'm back at school in front of the headmaster. 😬 😬

 

www.tightfart.com

A7 RDP pics here

[Peter Carmichael]

TF.... first of all.

 

Second...

By meaningless, I mean you need to add allowance for other parameters before a meaningful comparison can take place

 

Which you went on to use, with:

a capacity limit

 

So...

 bhp/litre x litres = bhp

Yes, a bhp comparison is useful for comparing cars in a typical racing class.

[Peter Carmichael]

The other significant thing is number of cylinders. If an Oilyhands in-line four cylinder head can flow 10,700 l/min, link two of the heads to a common crankcase and reduce the stroke by half and you are still looking at a sub 2-litre 400+ bhp engine.

 

Lots of revs though, which will show up as pain in the valvetrain.

 

This is why the RST-V8 has potential for far greater power than any of the four cylinder brethren.

[7 wonders of the world]

Dave,

 

Superb result !

 

quote:

--------------------------------------------------------------------------------

bhp doesn't come from litres, it comes from valve area

 

 

It's not valve area that's the crucial, but the total circumference of the valves over which the gas flows.

[Tony Whitley]

Ah, so the optimum solution would be small area valves (to fit in the head) with a large circumference. Interesting concept...

[AdamQ]

Easy as Pi ❗

[Peter Carmichael]

Ah, yes. Valve curtain area: circumference x valve opening

 

For all that we call them big valve heads, a valve is merely the lump of metal covering the big hole. The grind of the cam determines the valve acceleration away from the seat and hence the rate of growth of the initially open area. Flowbench measurements on some high flow K heads from a well known tuner show the increase in flow flattening off at beyond 9mm lift. Cams are well into 12+mm lift, so there is a significant dwell period when the port/throat is a limiting factor, but I generally agree that valve circumference is also a deciding factor. This is after all why 2 valve per cylinder designs cannot compete with 4 valve designs.

 

Have a look at this ancient thread: Self deception and position vacant at Ilmor

[caterhamnut]

I just got myself a bit excited about the following metric: bhp/ total cylinder cross section area

 

...pah! I dream of getting a bit excited by such things. Unfortunately all I could do is colour them in, so this is another thread where I shall just have to sit back and be educated and entertained!!

 

Well done Oily 😬

 

(Having said that, I did keep getting goosebumps at the F1 testing yesterday, so maybe there is hope.... 😬)

 

www.mycaterham.com

here

91,000 miles -1st 1.6k Supersport, '95 Motor Show car

[DSL]

Well done Oily *thumbup*, & there was you telling me 250bhp was about the ultimate a few months ago 😳 😳

[jerrypike]

david

king for a week 😬

 

peter

yamaha were using 5-valve heads on bikes 20 years ago ostensibly for the valve area/circumference equation

i assume they've disappeared for cost reasons (manufacture/service) 🤔

 

jerry

[Rob Walker]

Oily,

 

Now enough is enough, I am never going to get any further duratec orders if you continue getting results like this.

 

Rob

[Dobuy]

Excellent job, don't care what type of engine it is, that kind of horsepower is fun

 

Duratec SV, built in Dubai

[Tight fart]

I have never believed that there is any point in having a gas flow rig and measuring the flow.

 

www.tightfart.com

A7 RDP pics here

[AMMO]

Tight Fart

 

I don't know of any successful engine tuners who do not use or have used a flowbench of some sort at some point. Ricardo was doing it ages ago. Lotus and Cosworth have flowbenches. Let's not start a debate about it though and just agree to disagree. Your opinion is sacrosanct and it is not my job to convince you otherwise.

 

Oily

 

Changing the subject, what is the bore, stroke, rod length and valve sizes of the latest 1900 K? Particularly interested in the inlet valve size you have managed to squeeze in if that information is not too personal.

 

Peter

 

I always do a quick calculation of bhp/litre. Doesn't harm does it? Especially whan I was developing my old race bike and the stroke was being stretched and changes were being made tothe bore and valve sizes. It was interesting to see how the power, torque and bhp/litre figures changed. Call me strange if you like but I found it quite interesting.

 

AMMO

[Tight fart]

Sorry I should have used the full quote.

 

"I don't want to give away too much of our philosophy on cylinder head design, because it is obvious that most people are just not thinking about the problem. Most of them get absolutely mesmerised by gas flow, mainly because it is something that can be measured fairly easily. The unfortunate thing is that there is no point in getting an awful lot of mixture into an engine unless you can manage to burn it at the right time, and if you try too hard to get high gas flow figures you can easily wind up with a combustion chamber which does not combust. I have never believed that there is any point in having a gas flow rig and measuring the flow. I think it is possible to look at the shape of a hole and decide whether air would like to go through it or not. A hole that looks nice and smooth and has no projections will generally flow easily. Most people start with something so horrible that to create an improvement should be very simple. I would claim that I could arrive at something very close to their results from gasflowing just by putting my finger down the hole and seeing what it feels like; in any case, to be totally mesmerised by the air situation is to loose sight of the object of the operation is a bit short sighted."

 

Not my thoughts I know nothing about tuning engines. I had been reading on how they were getting 143bhp per litre (sorry Peter) out of a modified cortina engine back in the mid 60s.

 

Oh and the above is from Keith Duckworth 1933 - 2006

 

www.tightfart.com

A7 RDP pics here

[oilyhands]

FWIW I dont use a flowbench although I have in the past, the best flowing heads I have done were produced without the aid of a flowbench, I use the Duckworth method to all intents and purposes viz..

 

"I think it is possible to look at the shape of a hole and decide whether air would like to go through it or not. A hole that looks nice and smooth and has no projections will generally flow easily. Most people start with something so horrible that to create an improvement should be very simple. I would claim that I could arrive at something very close to their results from gasflowing just by putting my finger down the hole and seeing what it feels like"

 

That doesnt mean that a flowbench is not important, especially if you are inexperienced with the particular head, but like any other device, it can easily lead you up the garden path, it's important to remember that a port does no flow air continuously, but rather flows air in a serious if pulses where the air is accelerated and decellerated.

 

I dont doubt that Cosworth were producing more BHP per litre, but I will say again, the bore stroke relationship of the Cortina engine is much more favourable and gives room for very large valves. Anyone who does not believe that larger valves will lead to better volumetric efficiency does not understand the dynamics. It is also probabe that Cosworth had more resources to bring to bear than I can currently muster. Given an engine with a 90mm bore and 70mm stroke, the output capabilities would be much higher.

 

Ammo,

 

The engine is a stock 89mm stroke and 82mm bore with standard rod length and centres. The inlet valves are 33.8mm and exhaust 28.3mm. I have built other engines with these valve sizes, but the trick work is in the port orientation.

 

Oily

[AMMO]

Thanks for the info Oily. Excellent result for the size of inlet valve.

The head is obviously working very well.

 

 

AMMO

[oilyhands]

Some of you may remember this 1900K owned by Simon Thornley that made 264BHP at the Emerald RR some months back. The power trace was still climbing at the self imposed rev limit of 8800. now that the owner has done a seasons worth of events the engine is properly run-in and he decided to take the car back to Emerald for a further series of runs with a raised rev limit of 9250.

 

The conclusion is that the engine has too much cam as the power is still climbing at 9250 where the engine made 286BHP.

 

Needless to say the owner is very pleased, he had said all season that the engine seemed to be improving as the bores settled in.

 

Next season may see the timing backed off in the mid range to reduce the torque which peaked at 179lb/ft at 6700.

 

Dave

[MartinWoodham]

Nice result!!! *thumbup*

I must call you about my 1600 SS project.....when's a good time?

 

Martin

Aero'd Roadsports B with a garage slowly filling up with upgrade parts