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TwoSeven
14th June 2006, 22:38
On an inline-4 bog standard 600. I know why the inlet closes at say 35deg ABDC - but why does it have to open at 15BTDC ?

edit: zorst closes 7deg atdc

if poss.. please show math.

cowpoos
14th June 2006, 23:06
it doesn't really....depends on the motor....whats it out of? that might help the techie's explain the state of tune...

Motu
15th June 2006, 06:59
Inertia,takes time to get things moving....and once moving to stop them again.

idb
15th June 2006, 07:33
What Motu said.
Fuel doesn't appear instantaneously in the cylinder when the valve is opened, it has inertia and needs to 'accelerate' from zero and move from the carburettor and into the cylinder.
So the valve has to be open long enough and soon enough to get the necessary charge of fuel into the cylinder before it is needed for combustion.

I'd be a shit teacher, but I know what I mean.

Paul in NZ
15th June 2006, 07:35
Dunno about the maths - no really I don't, but..

The inlet valve opens early because of something called 'overlap' which is defined as...

The amount of time, expressed in crankshaft degrees, that describes the window of time between the the Inlet Cam's opening point BTDC and the Exhaust Cam's closing point ATDC.

Usually, this varies between zero degrees to as much as 70 to 90 degrees on some race motors. Most street engines will have 20 to 30 degrees of overlap and most performance cams will have 50 to 60 degrees of overlap. Increasing the degrees of overlap tends to move the powerband up the RPM band. Increasing the overlap can increase peak power, but ONLY if the exhaust system is properly designed to scavenge the cylinder. Decreasing the overlap tends to boost lower rpm performance.

So Valve overlap is the period during engine operation when both intake and exhaust valves are open at the same time. Valve overlap occurs when the piston nears TDC between the exhaust event and the intake event. The intake valve is opened during the exhaust event just before TDC, initiating the flow of the new charge into the combustion chamber.

As the exhaust gases are evacuated from the combustion chamber, a small but distinct low-pressure area is created on the surface of the piston head. By opening the intake valve earlier that TDC, the charge begins to fill this low-pressure area while exhaust gases exit. The low-pressure area on the head of the piston assists the fresh charge in filling the combustion chamber to its maximum capacity.

Valve overlap is designed into the engine and is most useful at higher speeds. At higher speeds, the extra amount of intake charge brought into the combustion chamber provides a substantial increase in available power. The amount of time that both valves are open in directly related to engine rpm. The higher the engine rpm, the shorter the amount of time that both valves are open. The angle of crankshaft rotation when both valves are open do so change, only the amount of time both valves are open varies. Thus at idle, the amount of time both valves are open is relatively long compared to that at top no-load speed.

Motu
15th June 2006, 08:18
The Goldstar cams I used in my B31 had 120 degrees of overlap - 65-85 - 80-55.So the inlet valve was closed with the piston almost halfway up the bore,the exhaust valve opening just past halfway on the power stroke...a fucking serious cam to run on the street.I couldn't run a ram tube as the fog it collected upset the mixture....the left leg of my jeans smelled of petrol.I used to run various exhaust systems and carbs,pistons,other cams.And still a first start kicker.

My XLV750 had 10 degrees overlap,valves opening and closing 5 deg before and after TDC,about the same as a Briggs & Stratton...how the hell did they get so much power out of it?

Paul in NZ
15th June 2006, 08:29
The Goldstar cams I used in my B31 had 120 degrees of overlap - 65-85 - 80-55.So the inlet valve was closed with the piston almost halfway up the bore,the exhaust valve opening just past halfway on the power stroke...a fucking serious cam to run on the street.I couldn't run a ram tube as the fog it collected upset the mixture....the left leg of my jeans smelled of petrol.I used to run various exhaust systems and carbs,pistons,other cams.And still a first start kicker.

My XLV750 had 10 degrees overlap,valves opening and closing 5 deg before and after TDC,about the same as a Briggs & Stratton...how the hell did they get so much power out of it?

I for one have never been able to get to grips with why some things work and others don't on certain engines. I know the B33 we 'tried' to improve with wild cams and a massive carb ran like shite... Later on we found the magneto was on it's last legs but as spotty youths, we assumed, spin the mag on the bench, spark appears - it's a good un.. complicated beasties magnetos - when they go wrong....

Had the same problem with the big concentric we tried, the engine never really shifted enough air through it to make it work properly, probably down to the wild cams and us not setting them up properly.

Eventually, I started listening to advice from trusted tuners rather than half reading Tuning for speed.. When my carbs on my hot atlas got so rooted it would not idle, I purchased smaller bodies (only new ones we could get) and a very kind man bored them out for me effectively creating smooth bore carbs which I didn't quite get then but they sure made a difference...

Funnily enough, I have resisted all the usual performance mods to my Guzzi and Triumph. Most of the tuners admitting these days that while you may gain a few bhp, there is a serious downside.... Funny old world..

riffer
15th June 2006, 10:03
So - if you were going to produce a GDI motorcycle engine, how would valve overlap work?

Motu
15th June 2006, 10:15
We are just pumping air then...but air still has mass,just don't have to factor in the fuel as well.Fuel injection has allowd intake runners to be tuned,this wasn't really possible with carbs,there was always a compromise.Check out a fuel injected car engine - nice intake manifolding the last 15 years.

Paul in NZ
15th June 2006, 11:09
We are just pumping air then...but air still has mass,just don't have to factor in the fuel as well.Fuel injection has allowd intake runners to be tuned,this wasn't really possible with carbs,there was always a compromise.Check out a fuel injected car engine - nice intake manifolding the last 15 years.

Yes, I'm certainly no expert on this but the idea of overlap is to get as much fresh charge into the chamber as possible. This is done by using the movement of the departing burnt charge pulling in the fresh charge etc etc.

Whether the charge is mixed in the inlet tract or the chamber is largely immaterial because it's the air that has the most mass to move. It should (I suspect) be more efficient because the air has no fuel vapour suspended in it but the challange would be to time the entry of the fuel so that it has enough time to mix with the air but not loose any into the exhaust ...

Then again, I know stuff all about it really... Ask me about flat screens, I know about them.... a little

Ixion
15th June 2006, 11:31
Port angles come largely into this too. The ideal is to have the incoming slug of mixture moving fast in a sort of spiral (if it moves too slow the fuel falls out of suspension), and shoot off down into the cylinder in a corkscrew direction that takes it away from the still open exhaust port.

And , in a perfect world, the exhaust port is being blocked by a pulse of gas pressure send back from the megaphone.

And the overlap is often partly determined by the inertia of the valve gear. Heavy valves, you just can't open them too quickly, the cam has to have a gentler ramp up (not to mention the dreaded silencing ramps!). Overhead cam engines tend to have less overlap because of this (cf Mr Motu's XRV750) . On an OHV pushrod engine, the first fraction of a second is taken up just flexing the pushrod, shoving the rocker around etc. Stiffer, less wobbly train on an OHC can react faster without getting all tangled up. Ditto for 4 valve heads. One overlooked advantage of these (overlooked cos motorcyclists don't care qany moe) is reduced fuel consumption - less valve overlap less fuel pumped straight out the zorst.

But, then emissions reduction stuffs all of this up.

'Twas always a black art. That's why I like two strokes. So nice and simple.

Motu
15th June 2006, 12:31
We've talked about this before,it's valve acceleration.The old Beeza had huge pushrods damn near a foot long,although they were alloy,and a couple of monster valves,and on the Goldy an 1 1/2in carb,that must of slowed gas speed down a lot...coming off cam was damn near stalling the airspeed in the port...and reversing it for sure...The cam was an unusual shape,a small base circle and long flanks with a flat tappet - it must of come up on the flank then levered the whole valve train up on the nose.I never valve bounced a B31 (well,I did with a broken valve spring) and I don't think the Goldy had problems,but 7,000 rpm must of been damn close to super nova stage.

But the XLV750 could make good power on lawnmower cam timing because of advances in valve weight,port shape,cam profile,and combustion chamber design.If we ever get to the point of having electronicaly controlled valves (I don't think it's possible with poppet valves) we will be able to have infinatly varable valve timing over the whole rev range....always ''on the cam''.

riffer
15th June 2006, 12:43
Wow. Great answers guys.

Could you control valves with electromagnetics? Or is it just not fast enough?

idb
15th June 2006, 12:45
Wow. Great answers guys.

Could you control valves with electromagnetics? Or is it just not fast enough?
I think I read somewhere that they are used in F1 engines.

Motu
15th June 2006, 12:56
No,they use pneumatic control to close the valves.An electronicly controled valve can't work very fast,they have been used on diesel engines,like about 5,000rpm max.They will have to use some other method of port control before they can be used in anything.....a 19,000rpm F1 engine? - no way in hell.

TwoSeven
15th June 2006, 13:05
Inertia,takes time to get things moving....and once moving to stop them again.

Interia doesnt sound right. Doing some (really rough measurements) the surface area of my inlet port is 2.54cm2 and my exhaust port area is 1.77cm2 (its acutally slightly bigger, but I dont yet know how to calculate the volume of an oval).

Because the inlet valve is opening on the exhaust stroke, the exhaust gas is under pressure - the inlet valve is now at 1mm lift (15 deg btdc), that means the exaust gas should in theory try to go out the inlet more so than trying to go out the exhaust port (path of less resistence).

Hence I am confuzzled as to why one would open the inlet valve then. Only thing I can think of is that most of the zorst gas is gone (perhaps because of scavanging) and there is hardly any pressure left (or its less than the inlet charge).

TwoSeven
15th June 2006, 13:11
The Goldstar cams I used in my B31 had 120 degrees of overlap - 65-85 - 80-55.So the inlet valve was closed with the piston almost halfway up the bore,the exhaust valve opening just past halfway on the power stroke...


I think your talking about dynamic compression here. Something I am currently trying to do the math on. This engine (a cbr600f2) runs the inlet close at 35 abdc when its on-cam, so losing about 20% of the compression stroke as far as I can work it out. I've been thinking prehaps reducing the duration slightly so its down to about 25 deg.. Less gas charge but more compression.

Zorst valve for me opens at 38bbdc on the power stroke.

Ixion
15th June 2006, 13:13
It's actually quite complicated, because you can't think of it in static terms. Remember this is all happening about 50 times per second.

f'instance, on the previous stroke, there was this column of air whizzing at high speed down the inlet tract. Then the inlet valve slammed shut in front of it. But the air has inertia too, so it tries to keep moving and banks up behind the closed valve under pressure. One fiftieth of a second later (that's 20 milliseconds!) the valve opens again. Who knows what the inlet pressure at the valve is then?

Same sort of issues in the exhaust port, made even more complicated by resonance (though you can get that in the inlet , too, when the inlet valve shuts it causes a reverse ripple back through the carb - one reason why hairy race engines backfire through the carb. And inlet valves can be big enough that as they close the heads actually serve as paddle pumps, forcing the air mixture backwards. )

I prefer to classify the whole subject under "magic" myself.

TwoSeven
15th June 2006, 13:15
As the exhaust gases are evacuated from the combustion chamber, a small but distinct low-pressure area is created on the surface of the piston head. By opening the intake valve earlier that TDC, the charge begins to fill this low-pressure area while exhaust gases exit. The low-pressure area on the head of the piston assists the fresh charge in filling the combustion chamber to its maximum capacity.

So exhaust is scavanging then (means I have to get the primary header length accurate I guess).

willy_01
15th June 2006, 13:21
whats stopping manufactures using rotary valves on a 4 stroke? Can they not handle the combustion pressure or is lubrication their biggest issue (hence why they only seem to be doing big things on 2 stroke engines). It just seems better, not having anything upsetting the flow of air into the chamber ie the valve itself.

idb
15th June 2006, 13:22
Interia doesnt sound right. Doing some (really rough measurements) the surface area of my inlet port is 2.54cm2 and my exhaust port area is 1.77cm2 (its acutally bigger coz its oval but not by much).

Because the inlet valve is opening on the exhaust stroke, the exhaust gas is under pressure - the inlet valve is now at 1mm lift (15 deg btdc), that means the exaust gas should in theory try to go out the inlet more so than trying to go out the exhaust port (path of less resistence).

Hence I am confuzzled as to why one would open the inlet valve then. Only thing I can think of is that most of the zorst gas is gone (perhaps because of scavanging) and there is hardly any pressure left (or its less than the inlet charge).
Remember that the exhaust valve opens before the inlet.
This means that by the time the inlet valve opens the exhaust gases are already moving out of the exhaust valve.
These gases have already developed a momentum (inertia if you prefer) and don't just suddenly change direction to head out the newly opened valve.

TwoSeven
15th June 2006, 13:24
Port angles come largely into this too. The ideal is to have the incoming slug of mixture moving fast in a sort of spiral (if it moves too slow the fuel falls out of suspension), and shoot off down into the cylinder in a corkscrew direction that takes it away from the still open exhaust port.

And , in a perfect world, the exhaust port is being blocked by a pulse of gas pressure send back from the megaphone.

And the collector as well (zorst attentuation is next on my list of things to look at) :)

Ixion
15th June 2006, 13:27
whats stopping manufactures using rotary valves on a 4 stroke? Can they not handle the combustion pressure or is lubrication their biggest issue (hence why they only seem to be doing big things on 2 stroke engines). It just seems better, not having anything upsetting the flow of air into the chamber ie the valve itself.


They did. Rotary vales of various sorts (most notably the Knight sleeve valve) were hot stuff in the 30's.

As you indicate, lubrication and gas sealing were their bugbears.

Engineers have always regarded the poppet valve as the most horrible of horrible things. Problem is, no-one's found a better way yet. Except two strokes of course.

Paul in NZ
15th June 2006, 13:33
So exhaust is scavanging then (means I have to get the primary header length accurate I guess).

Yes, but remember that a tuned header length is generally only effective at a certain engine speed. The trick is deciding where you want your power to be and making sure inlet length, valve timing and exhaust design all conspire to make it so. Classic example is yamahas EXUP valve that effectively changes the tuned length of the exhaust thus giving a broader spread of power.

In a 4 pot engine, not only is the length of the header important but you need to make sure the collector and muffler are correctly dimensioned.

http://www.carcraft.com/techarticles/0304_merg/

Oh heck the 'net is full of it...

Once you start tuning an engine nearly everything becomes a trade off. I'll sacrifice a little power and torque here to gain a whole lot there... Street bikes usually require a broaded spread of power hence all the trickery...

You need to have a plan and stick with it. Just bolting a bunch of shite on is likely to make the bike run slower....

Motu
15th June 2006, 13:33
Right - the exhaust gas has already gone,it has inertia and as it goes out it can help pull in the intake charge.The whole resonance tuning thing works on that,plus a negative pressure wave coming back up the pipe and into the cyl.It's a cycle of events,each dependent upon the other - The exhaust gases go out first under pressure,then the pressure drops,but they are still going out.The inlet side works the same way - by the time you have got the stuff pouring into the cyl it will keep doing it until you tell it to stop.Even with the piston coming up the inertia will keep the charge going in until the forces of the piston overcome it...then you can close the valve.It would be easy if they were sheep and you had a good dog to control them....

Paul in NZ
15th June 2006, 13:36
They did. Rotary vales of various sorts (most notably the Knight sleeve valve) were hot stuff in the 30's.

As you indicate, lubrication and gas sealing were their bugbears.

Engineers have always regarded the poppet valve as the most horrible of horrible things. Problem is, no-one's found a better way yet. Except two strokes of course.

That and rotary valves (and rotaries) often end up producing very large combustion chambers that are horribly inefficient on fuel. Not a good thing in this day and age..

TwoSeven
15th June 2006, 13:37
Remember that the exhaust valve opens before the inlet.
This means that by the time the inlet valve opens the exhaust gases are already moving out of the exhaust valve.
These gases have already developed a momentum (inertia if you prefer) and don't just suddenly change direction to head out the newly opened valve.

So the inertia of the gas is creating a low pressure area behind it which helps to build the inertia of the inlet charge [conductence ?].

Question is, the zorst gas is under pressure (because its being pushed out, rather than being sucked out as is occuring to the inlet charge which is not under pressure). So I thought that would have an impact as well. Perhaps the piston is now slow enough so that the dwell at tdc is starting to have an effect as well.

I wonder if its to perform attenuation of the inlet port in the same way as the megaphone is used to attenuate the zorst port ?

Ixion
15th June 2006, 13:37
Yith. And long and weirdly contorted ports. Which didn't matter so much in the 30's when 6:1 was high compression.

Ixion
15th June 2006, 13:40
,,

I wonder if its to perform attenuation of the inlet port in the same way as the megaphone is used to attenuate the zorst port ?

If you look at some of the pictures of the single cylinder racers of the 60's you may see some with honking long tubes on the carb intakes. A foot long in extreme cases. Theory was these acted to attenuate the inlet flow, as you say. Dunno if it ever actually worked, mind.

idb
15th June 2006, 13:43
And the collector as well (zorst attentuation is next on my list of things to look at) :)
It works too.
I made myself some headers for the 750/4 and tuned the lengths from a formula I got from a book.
The power came on exactly where I calculated it should.

There'll be other factors come into play as well (as discussed above) but I don't care-it proves how clever I am at the end and that's all that really matters.

idb
15th June 2006, 13:49
So the inertia of the gas is creating a low pressure area behind it which helps to build the inertia of the inlet charge [conductence ?].

Question is, the zorst gas is under pressure (because its being pushed out, rather than being sucked out as is occuring to the inlet charge which is not under pressure). So I thought that would have an impact as well. Perhaps the piston is now slow enough so that the dwell at tdc is starting to have an effect as well.

I wonder if its to perform attenuation of the inlet port in the same way as the megaphone is used to attenuate the zorst port ?
Yes, the inertia of the exhaust gases helps 'suck' in the fuel charge.

But wait, there's more.....
Pulses of low pressure are sent back through the exhaust gas column from the end of the header pipes.
These pulses help to scavenge the exhaust gases from the exhaust valve as well.
Peak efficiency is reached when the low pressure pulse arriving at the exhaust valve coincides with that valve opening.

Motu
15th June 2006, 13:50
whats stopping manufactures using rotary valves on a 4 stroke? Can they not handle the combustion pressure or is lubrication their biggest issue (hence why they only seem to be doing big things on 2 stroke engines). It just seems better, not having anything upsetting the flow of air into the chamber ie the valve itself.

Shit,a whole page of posts went up while I was doing my reply,making it redundant! This thread must be more interesting to some than the bitch sesions going on elsewhere....

Ralph Watson,one of this countries great unknown engineers,has made a working rotary valve (Ralph Watson built the Lycoming Special) There is a very limited edition book about him (into second edition),I got mine hot off the press from the author,printed by one of my customers.Ralph's lifetime work,like Burt Munro,but oh so smarter,was his BSA Special,using a V twin engine.Finaly he had built the whole engine himself,including crankcases,cranks,rods,pistons and cyls - then he made his own rotary valve heads.By the time Ralph was confined to a wheelchair suffering from Parkinsons disease he had put more than 30,000km on it (I'll check my book tonight) He beat all the so called problems with rotary valves...the motor is a work of art.

TwoSeven
15th June 2006, 13:52
Yes, but remember that a tuned header length is generally only effective at a certain engine speed. The trick is deciding where you want your power to be and making sure inlet length, valve timing and exhaust design all conspire to make it so. Classic example is yamahas EXUP valve that effectively changes the tuned length of the exhaust thus giving a broader spread of power.

In a 4 pot engine, not only is the length of the header important but you need to make sure the collector and muffler are correctly dimensioned.

http://www.carcraft.com/techarticles/0304_merg/

Oh heck the 'net is full of it...

Once you start tuning an engine nearly everything becomes a trade off. I'll sacrifice a little power and torque here to gain a whole lot there... Street bikes usually require a broaded spread of power hence all the trickery...

You need to have a plan and stick with it. Just bolting a bunch of shite on is likely to make the bike run slower....

I've already chosen and 'fixed' my parameters. Am using 12.5k rpm where the old peak power was. My goals are to increase dynamic power (but not a priority) and modify the torque cuve and move peak torque closer to peak power (only to make the bike slightly more agressive). I'm not interested in increasing overall power. I could just buy a new bike for that.

On the design styling side I would like to also make an underseat zorst (which is changing my zorst length and diameters - if done much of the math just seeing now if the engine will like it or not). I'm thinking of changing the 4-1 into two 2-1 on each side.

So far I've not had much of a need to look at the carbs because it seems that the flow rate is more than enough from the 36mm to cover stuff (although i might look at the jetting closer a bit later).

My trade off is that I'm taking everything from below 5.5k rpm and a little from above the 14k range (but I think I might need that bit back).

Paul in NZ
15th June 2006, 14:33
If you look at some of the pictures of the single cylinder racers of the 60's you may see some with honking long tubes on the carb intakes. A foot long in extreme cases. Theory was these acted to attenuate the inlet flow, as you say. Dunno if it ever actually worked, mind.

I have played with extended inlet manifolds on triumph twins and there are gains to be made in torque but i suspect, not in BHP. Isolating the carb from the vibrating engine helped a little as well but there was a distinct $$ limit and mechanical limit beyond which I could not go....

(snif)

Brian d marge
15th June 2006, 14:36
We on the Enfield site, have done a lot of work to get these thing running with modern power outputs with enfield reliability

Charles Fayette taylor ; The internal combusion engine

wood ; SAE Journal no 50 June 1942 - Airflow through intake valves

Livengood and Stanitz ; The effects of inlet design size and lift on air capacity and output of a four stroke engine
SAE Journal 915 November 1943

Eiichi and Watanabe ; An Analysis of the Volumetric Efficiency using mean index Mach number
SAE 790484 March 1979



Also see the Temp Entropy diag below and the pressure Volum dia for an otto cycle

It will give you grey hair nutting all that out but the maths is all there and so is the answer ....

Stephen

Paul in NZ
15th June 2006, 14:37
Shit,a whole page of posts went up while I was doing my reply,making it redundant! This thread must be more interesting to some than the bitch sesions going on elsewhere....

Ralph Watson,one of this countries great unknown engineers,has made a working rotary valve (Ralph Watson built the Lycoming Special) There is a very limited edition book about him (into second edition),I got mine hot off the press from the author,printed by one of my customers.Ralph's lifetime work,like Burt Munro,but oh so smarter,was his BSA Special,using a V twin engine.Finaly he had built the whole engine himself,including crankcases,cranks,rods,pistons and cyls - then he made his own rotary valve heads.By the time Ralph was confined to a wheelchair suffering from Parkinsons disease he had put more than 30,000km on it (I'll check my book tonight) He beat all the so called problems with rotary valves...the motor is a work of art.

Now thats something I'd like to know more about....

I remember a quote from Phil Irving regarding the Sarich (sp) orbital engine - "That engine will never go into serious production' or words to that effect...

Sealing a rotary valve at high rpm would probably be the issue I suspect.

Some days I seriously wonder if we are on the right track at all. Perhaps the research should have gone into transmissions and we could have stuck with a fixed speed engine to get optimal operation.

Kickaha
15th June 2006, 17:16
Wow. Great answers guys.

Could you control valves with electromagnetics? Or is it just not fast enough?


I think I read somewhere that they are used in F1 engines.

Renault F1 have experimented with this in their quest for infinitely variable valve timing but as yet they have not been able to make it work

willy_01
15th June 2006, 18:03
Renault F1 have experimented with this in their quest for infinitely variable valve timing but as yet they have not been able to make it work

haha are you sure? Renault have come from nowhere in the last 2 years.

I saw a very cool engine about 2 years it was a 36 cylinder (3 v12's) supercharged 2stroke desiel:gob: (well i think), i cant remember what it was called so cant find anything on in again but that was a true piece of engineering art, has anyone else seen this thing?

TwoSeven
15th June 2006, 18:21
It's actually quite complicated, because you can't think of it in static terms. Remember this is all happening about 50 times per second.

I'm doing both static and dynamic calculations. :)

TwoSeven
15th June 2006, 18:23
We on the Enfield site, have done a lot of work to get these thing running with modern power outputs with enfield reliability

Charles Fayette taylor ; The internal combusion engine

wood ; SAE Journal no 50 June 1942 - Airflow through intake valves

Livengood and Stanitz ; The effects of inlet design size and lift on air capacity and output of a four stroke engine
SAE Journal 915 November 1943

Eiichi and Watanabe ; An Analysis of the Volumetric Efficiency using mean index Mach number
SAE 790484 March 1979



Also see the Temp Entropy diag below and the pressure Volum dia for an otto cycle

It will give you grey hair nutting all that out but the maths is all there and so is the answer ....

Stephen

I've been trying to do some of the thermal stuff already. Biggest problem at the moment is trying to calcuate the temperature changes. I've just been using fixed values (25degC), but want to be able to calculate stuff inputting a measured air and fuel temp. Recon I might have it in about 5 years time :)

TwoSeven
15th June 2006, 18:28
haha are you sure? Renault have come from nowhere in the last 2 years.

I saw a very cool engine about 2 years it was a 36 cylinder (3 v12's) supercharged 2stroke desiel:gob: (well i think), i cant remember what it was called so cant find anything on in again but that was a true piece of engineering art, has anyone else seen this thing?

Take a look at the new Audi R10 Le Mans racer then.

Brian d marge
15th June 2006, 20:04
I've been trying to do some of the thermal stuff already. Biggest problem at the moment is trying to calcuate the temperature changes. I've just been using fixed values (25degC), but want to be able to calculate stuff inputting a measured air and fuel temp. Recon I might have it in about 5 years time :)

the sae papers deal with air flow through the valves

woods sets out a methos to determine flow at various valve lift/ valve head dia

from memory watanabe deals with the dynamics of the flow


Stephen

Methos ..is like a mentos but different
The older sae papers are free , someof them are anyway !

Motu
16th June 2006, 14:41
I've got some photo's here of Ralph Watsons rotary valve heads....and I'm a bit scared about posting them.They are from the book ''Ralph Watson Special Engineer'' by T R Sheffield.It was put together for Ralph to clear up discrepancies about his work,and to cronicle what he's done.The photos are from Ralph's personal collection - I really hope I don't upset anyone,but I think everyone needs to know a bit more about this guy...after all,a film was made about Burt Munro.If you think I shouldn't put them up,take a peek,than I'll delete them.We are just tucked in the corner of some obsure forum anyway...

riffer
16th June 2006, 15:06
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You must spread some Reputation around before giving it to Motu again.







I'm enjoying the read...:yes:

Ixion
16th June 2006, 17:02
I've got some photo's here of Ralph Watsons rotary valve heads....and I'm a bit scared about posting them.They are from the book ''Ralph Watson Special Engineer'' by T R Sheffield.It was put together for Ralph to clear up discrepancies about his work,and to cronicle what he's done.The photos are from Ralph's personal collection - I really hope I don't upset anyone,but I think everyone needs to know a bit more about this guy...after all,a film was made about Burt Munro.If you think I shouldn't put them up,take a peek,than I'll delete them.We are just tucked in the corner of some obsure forum anyway...


Hm. The valve appears to be pure rotary, not reciprocating rotary like a Knight valve. How does it cope with deposit buildup . It's one thing to produce something like that which will run fine under racing condition, pulled apart every couple of thousand kilometres. Another matter to make it reliable for 250000 untouched miles.

That's always been the Achilles heel of rotary valves. Good as, to start with. 50000 miles later , oh dear.

I'm not knocking his work, just Devil's advocating. I've always hated the poppet valve myself, it offends my sense of engineering fitness.

Paul in NZ
16th June 2006, 17:36
Lust...... Imagine the Guzzi with...... LUST......

Motu
16th June 2006, 18:54
Hm. The valve appears to be pure rotary, not reciprocating rotary like a Knight valve. How does it cope with deposit buildup . It's one thing to produce something like that which will run fine under racing condition, pulled apart every couple of thousand kilometres. Another matter to make it reliable for 250000 untouched miles.

That's always been the Achilles heel of rotary valves. Good as, to start with. 50000 miles later , oh dear.

I'm not knocking his work, just Devil's advocating. I've always hated the poppet valve myself, it offends my sense of engineering fitness.

All of Ralph Watson's cars were road legal,even the Lycoming - it was never trailered....Jim Boyd would toss a bag in and drive to Levin,Wigram,Invergargil,whatever,race for the weekend and then drive home again.They were all totaly driveable cars.The BSA had done 30,000 miles at the time of the article,Ralph had taken it on several South Island trips (makes us look like nanny bikers).Of course he had to keep an eye on it as part of his development,but he says it just needed a bit of a decarb and the seals cleaned.

There was a report from the new owner,and he was saying how surprised he was on how wide the power band was,considering that the valve timing would be considered quite wild for poppet valves.As it says,possibly the only working rotary valve engine in the world,as powerful and reliable as an ordinary valve train.Ken McIntosh gave Ralph a Manx motor and wanted him to do a rotary valve for it,but Ralph,always practical and honest said the power gains weren't worth the effort,he admitted that modern development had surpased his efforts.

Would look good on show on the front of a Morgan too eh?

Pixie
30th June 2006, 13:34
whats stopping manufactures using rotary valves on a 4 stroke? Can they not handle the combustion pressure or is lubrication their biggest issue (hence why they only seem to be doing big things on 2 stroke engines). It just seems better, not having anything upsetting the flow of air into the chamber ie the valve itself.
www.rcvengines.com

Pixie
30th June 2006, 13:47
Wow. Great answers guys.

Could you control valves with electromagnetics? Or is it just not fast enough?
From 2003:

Lotus and Eaton hope to have vehicles demonstrating AVT technology within two years and to have systems in production and available for delivery by 2008.

An undisclosed major European vehicle manufacturer has already signed an agreement to acquire the AVT system for one of its platforms.'Eaton's Automotive segment produces products focused on fuel economy, the environment, and targeted safety systems.Our collaboration with Lotus means we can get to market quickly with one of the most exciting developments in valve train technology for many years', said Stephen Buente, EatonSenior Vice President and Group Executive - Automotive.'Between Lotus and Eaton there is the right mix of experience and know how to make the AVT system a world-leading technology that is attractive to vehicle producers the world over'.

The fully variable AVT system is several generations ahead of the various mechanical systems introduced by OEMs to improve the flexibility of their engines.

It offers a level of valve control never seen before in production engines.

Replacing the camshaft with lighter and more compact hardware, the electrohydraulic valve actuation technology enables virtually infinite manipulation of the timing, duration and extent of lift for each valve.

The complex control system selects and implements the valve lift profile that achieves optimal operational efficiency across the engine's entire speed and load range.In addition to reduced emissions and fuel consumption,Lotus' AVT technology offers increased torque and power output potential from the engine.

Furthermore, the AVT system will subsequently be an essential enabler for new combustion processes.

For example, Lotus has demonstrated that controlled auto ignition (CAI) and homogenous charge compression ignition(HCCI) are capable of reducing engine-out nitrogen oxides (NOx)emissions by up to 98%.

Pixie
30th June 2006, 13:56
That and rotary valves (and rotaries) often end up producing very large combustion chambers that are horribly inefficient on fuel. Not a good thing in this day and age..
The RCV engine can have a combustion chamber smaller than a poppet valved engine

Pixie
30th June 2006, 14:02
haha are you sure? Renault have come from nowhere in the last 2 years.

I saw a very cool engine about 2 years it was a 36 cylinder (3 v12's) supercharged 2stroke desiel:gob: (well i think), i cant remember what it was called so cant find anything on in again but that was a true piece of engineering art, has anyone else seen this thing?
Napier Deltic
Here's a working model:
http://www.craftsmanshipmuseum.com/Tomlinson.htm

TwoSeven
30th June 2006, 17:14
My next project after the 600 engine is going to be either a window powered stirling engine, or a hand powered one. That is, work from the heat of the hand. But first, need to start off with the tin-can engine. But thats way in the future.

thealmightytaco
3rd July 2006, 17:09
My next project after the 600 engine is going to be either a window powered stirling engine, or a hand powered one. That is, work from the heat of the hand.

What about running off the heat of your ass? Be a sore seat to ride but. Butt.