Take a factory block:


Bore the f**k out of it, and insert new cylinder liners:

Note how it's bored right into the water galleries.
The keen eyed will note this one is an aluminium Ford GT block.

There's a guy on FordForums, with a 6.0L and supercharger.

Yeah yeah. I get that. What I was trying to get at is HOW MUCH AIR would a 100% efficient 4L motor need per revolution? 4L or 2L?

Obviously if all six cylinders had fired that would be TWO revolutions wouldn't it?

For instance --- A 250CC single engine as found in a Honda XR250 doing 1000rpm would be firing its single spark plug 500 times a minute. It would only INTAKE AIR INTO THE CHAMBER 500 times a minute.

Thus (forgetting V.E) a 250cc Honda single engine would suck in 250cc 500 times a minute, resulting in 125 lt per minute rather than 250lt you would expect at 1000rpm.

I am not trying to work out how much forced induction would help - I just want to know how much air a normally aspirated engine of a certain size would require to run at certain RPM's. Looking at the figures supplied the answer is "quite a bloody lot".

Which leads me back to improving the flow of the head and changing the shape of the piston and / or head to make a faster burning chamber if possible.



That bore and re-sleeve option looks the part alright... Do you really think you'd need to over-bore and put a new sleeve into the 4lt inline six just to get up to 96mm or so? I can see you having to do that for 100mm or more, definitely.

Hmm... I'm going to get off my broken lazy a*** and go down Butlers garage for the first time in a week or two and have a play with measuring the block before I throw it on the scrap metal heap.

Also --- I note that in the above example there appears to be channels through the retro fitted sleeves... The original alloy block has had its water galleries chopped into and the sleeve fitted... Do you think the little holes visible in the top of the new inserts actually carry any coolant or oil or anything else??? Would be a nice little job getting them all to work and line up with whatever you're doing in the head or underneath at the crank end. Anyone bothered to provide a clue what those little holes or the purpose is of that outer ring design around the bores?

125L/min is right, so 2L/rev is right for the 4.0 (well it's not exactly 4000cc).
(edit: for a four stroke, two strokes are of course use ideally twice the air)



Yes, engines are air pumps. More air in, more air out = greater efficiency. That's why the first mods anyone does is intake and exhaust. Factory intakes and exhausts have to meet noise and emissions regulations (and cost/budget), so are not optimal for efficiency. Porting heads, bigger valves, higher lift cams, boost. It's all about getting more air in and out.



Their for coolant. As said the sleeve encroach on the water galleries, so the holes help keep the required flow. They all line up with the coolant passages on the head, I believe the gasket isn't anything special (other than having bigger bore holes).

those bores are drop dead gorgeous.

I wonder what sort of play money it would require on the 6 cyl.

Reckon you could stretch a bore to fit 100mm pistons in the 6 with the resleeve, data?

Never thought about it, to tell the truth. What the bore centre spacing in the block? If it's more than 100mm + a few mm for the sleeve, then I guess you could. Pending you don't remove too much block strength to fit the sleeves.

well cms were getting as far as 98mm before heading into jackets trouble, so i imagine you should be able to chew into the jackets a bit like that boss block.

maybe 100mm slugs are possible. that would probably sting though.

has anyone ever built a square motor before? car manufacturers either go oversquare or undersquare, I wonder if being same bore x stroke results in the drawbacks of both and none of the strengths?

theres a fancy question: can anyone find me details on an engine that exsisted, no matter the age, that was completely square. (not in shape either )

EDIT: holy crap, how easy was that just answered my own question readin up on the seksi veyron..

guess what... its a square motor! 7,993 cubic centimetres (487.8 cu in) 90° W16 engine; bore: 86.0 mm (3.39 in), stroke: 86.0 mm (3.39 in) (stroke ratio: 1:1, 'square engine'), 499.6 cc per cylinder


amazing...

edit EDIT: woops and another fascinating example:

"Like the Colombos, Lampredi engines found their way into road cars as well. The 1952 342 America and MM were first with big 4.1 L (4102 cc) engines producing 200 and 300 hp (149 and 224 kW). Lampredi engines moved to the 250 with the 1953 250 Export. Unlike the earlier engines with their oversquare 80 mm (3.1 in) by 68 mm (2.7 in) bore and stroke, the 250 used square 68 mm (2.7 in) dimensions for 3.0 L (2963 cc) total. Power was impressive at 220 hp (164 kW)."

164 kw from a 3l square engine in 1953, pretty impressive.

Last edited by Grimketel on Tue Sep 22, 2009 9:50 pm, edited 1 time in total.

What about destroking and bore a bit, that would make it more square. Have to deck the block too i suppose. Then lift the revs to accomodate the shorter stroke.

You don't have to go exotic to find square engines either.

IIRC Ford's 5.0L version of the 4.6/5.4 modular V8 is almost square (90mm stroke / 94mm bore, made by boring out a 4.6L block). And it's a revver.

yeah Sr20 and toyota 3sfe/ge have 86mm bore and stroke...

rb30s have 85or86 bore and stroke

What are the rod-stroke ratio's for these square motors anyway? 1.8:1, 2:1 or more than 2:1? Flicking through textbooks I am led to believe that 2:1 is ideal for a square motor but look at some early F1 engines. 1.7:1 and rev ceilings in the mid to high teens (as in 15,000rpm+). in theory it just isn't supposed to work, but in practice it works damn well.

Now, this is where I jump in with a story that probably shouldn't be shared... But hey, the guy had just taken my bike for a ride, dropped it, and dinged all the pipes...

So, here I am on this INLINE 4, 250 (or 249 exactly) CUBIC CENTERMETER, WATER COOLED, FOUR STROKE, commonly known as a HONDA CBR 250 RR Hurricane ...

It has a redline on the tacho of about 18,000. Since the guy had just dropped my bike and wasn't helping out with any form of compensation for trashing it, I held it in second gear and finally decided to change up a gear at 24,000 (quickly decided to change up another gear very soon thereafter).

There was still power up there. Blew me away. This little Honda didn't push a little piston into my stomach (nor road) but kept producing power... Admittedly you'd have got just as much power at about 12,000 as you did at 24,000 but these little engines were pretty good between 14-17,000.

They had bore / stroke of 48.5 mm x 33.8 mm and about 45 bloody horsepower anywhere between 15-16 depending on air temperature... (!)

I hated them. They were crap, power was rated at "next to nothing" at 1000 and then went through some horrible slow progressive curve up to the ear splitting 45 horses at 16,000. Crap.

Give me a two stroke. That riding style (always aiming for perfect power range - never economy, safety or reliability conscious) progressed to the Ducati in later years too... If anyone ever saw a 916SS held on 9,000-11,000 RPM it's whole life (middle of the city, country, warming up in the morning.... You name it) that was me... And it loved me for it. Other road users may not have appreciated the science of it, but my face was all ear to ear grin.


I have just typed in the numbers of the little Honda into my simple spreadsheet and found an interesting thing...

The PISTON SPEED at 16,000rpm (in Km/h) is less than 0.2km/h different from the piston speed of our loverly inline sixes at 5,500rpm!!!

This leads me to believe that everyone has it wrong and that maximum power is attained by pushing pistons up and down at 33.33 km/h. No matter what the bore or stroke.

 

 

Attachments:

File comment: Displacement Figurer version2 with Honda data... DISPLACEMENT_2.xls [8 KiB] Downloaded 261 times

Run the figures on a F1 engine. Are they doing 33km/h too?

I was thinking that... Am just on my cellphone in the middle of nowhere with no spreadsheet access right now, but will try doing it by hand... The Williams team currently use Toyota RVX-09 engines...

I am trying to find the bore and stroke of these engines, but in the meantime, look at this...

"""""
Formula One currently uses four-stroke V8, naturally-aspirated reciprocating engines. They typically produce 224 kilowatts (300 bhp, 304 PS) per litre of displacement, far higher than most internal combustion engines. For comparison, the naturally-aspirated piston engine production car with the most specific power is the Honda S2000 engine with 92 kW (123 bhp, 125 PS) per litre.

The power a Formula One engine produces is generated by operating at a very high rotational speed, up to 20,000 revolutions per minute (RPM). This contrasts with road car engines of a similar size which operate safely at typically less than 7,000 rpm. However, the torque (turning force at a given speed) of a Formula One engine is not much higher than a conventional petrol engine. For example, the 2006 2.4 litre Toyota RVX-06 V8 engine produces 552 kW (740 bhp, 751 PS) at 19,000 rpm and outputs 274 N·m (202 lb·ft) of torque giving the engine a 14.3 bar (1.43 MPa) mean effective pressure. This is comparable with the 14.3 bar maximum MEP of the 2003 BMW E46 M3 CSL, the best production car in this respect.

Consequently, high power is obtained by making an engine turn faster, a goal sought ever since research into performance engines began. The basic configuration of a naturally-aspirated Formula One engine has not been greatly modified since the 1967 Cosworth DFV and the mean effective pressure has stayed at around 14 bar MEP.[1] Until the mid-1980s Formula One engines were limited to around 12,000 rpm due to the traditional metal valve springs used inside the engine to close the valves. The speed required to operate the engine valves at a higher RPM is much greater than the metal valve springs can handle and they were replaced by Pneumatic valve springs introduced by Renault. Since the 1990s all Formula One engine manufacturers now use pneumatic valve springs with the pressurised air allowing engines to reach speeds nearly 20,000 rpm.

The bore is the diameter of the cylinder hole in the engine block for the piston and the stroke is the distance the piston travels from Top Dead Center(TDC) to Bottom Dead Center(BDC) inside the cylinder. A shorter stroke enables the engine to produce a higher rotating speed at a constant mean piston speed but also increases the speed at which the piston must travel in each revolution. Shortening the stroke however requires enlarging the bore to produce a Formula One engines 2.4 litre displacement resulting in a less efficient combustion chamber. The stroke of a Formula One engine is approximately 39.7 mm (1.563 in), less than half as long as the bore is wide (98.0 mm) producing an "over-square" configuration.

A 2.4 litre Formula One engine at 19,000 rpm has a 25 m/s mean piston speed (39.7 mm×2×19000 rpm / 60), the same value as the previously mentioned Honda S2000 engine (84 mm×2×8900 rpm/60). This value is typically limited by increasing intake port velocities and frictional losses, but is attained by commercial vehicle engines, like the Honda S2000, BMW E46 M3's S54B32 with 24.5 m/s as far back as 2001, the Audi RS4 with 24.2 m/s or the Yamaha YZF-R6 motorcycle with 23 m/s.

In addition to the use of pneumatic valve springs a Formula One engine's high RPM output has been made possible due to advances in metallurgy and design allowing lighter pistons and connecting rods to withstand the accelerations necessary to attain such high speeds. At each revolution, the piston goes from a null speed to almost two times the mean speed (approx. 40 m/s) then back to zero, and then another similar cycle to terminate the circle. Maximum piston acceleration occurs at TDC and is in the area of 95,000 m/s², about 10,000 times standard gravity.
""" from this Wikipedia.org page

A stroke of 39.7 mm@19,000=25metres/sec (translates to 90km/hour!)

The formula for working this out is different to my crap effort...

My effort at working out this turns out to be wrong... I used
STROKE*REVS
It should be STROKE*2*REVS

a***!

So - All my figures should be doubled. The most power out of our Inline Sixes and the Honda CBR250RR is attained at double my previous guess = 66.6KM/h.



OTHER STUFF OF NOTE---
No injection of water, forced induction, etc etc etc... Sadly the good old days of people making fast cars with whatever technology they like are long gone. Maybe there is some room for a proper "ricer" race category in Australisian "modified production" race series?!,......


""""the engines must be 90° V8 of 2.4 litres maximum capacity with a 98 mm maximum circular bore, which imply a 39.7 mm minimum stroke. They have two circular inlet and exhaust valves per cylinder, are normally-aspirated and must have a 95 kg (209 lb) minimum weight. Previous year's engines with a rev-limiter are permitted for 2006 and 2007 for teams who can't obtain a competitive V8.

Pre-cooling air before it enters the cylinders, injection of any substance other than air and fuel into the cylinders, variable-geometry intake and exhaust systems, variable valve timing are forbidden. Each cylinder can have only one fuel injector and a single plug spark ignition. Separate starting devices are used to start engines in the pits and on the grid.

The crankcase and cylinder block must be made of cast or wrought aluminium alloys. The crankshaft and camshafts must be made from an iron alloy, pistons from an aluminium alloy and valves from alloys based on iron, nickel, cobalt or titanium. The complete rules are available from the FIA Formula One world championship regulations.[9]

This is leading to a power reduction of around 20% from the three litre engines, However in many cases, performance of the car has been improved. In 2006 Toyota F1 announced an approximate 740 hp (552 kW) output at 19000 rpm for its new RVX-06 engine,[10] but real figures are of course difficult to obtain.""" (from Wikipedia page again)

Average piston speeds or instantaneous piston speeds? Give me a few days to knock up my spreadsheet.

everyone is wrong huh....

is this you trying to be humorous....

max power has nothing to do with what speed the engines revs at...

power is torque x rpm.....so it has 2 factors....you can increase rpm but oif torque is reduced by a factor more than rpm has increased then power goes down....

torque is the result of maximum VE and pressure pushing on the piston...

obviously if you cant increase pressure you have to up the rpm but u still need to have pressure being generated and that is where ve comes in...

airflow not rpm is the limiting factor....provided the internals have the strength to take it....

this thread is annoying because one minute your talking theoretically the next your trying to apply to I6s....your trying to set a rev target then build the engine to it, which is stupid...

if i rev the i6 to 33.33m/s ill get the most power.....er no