This months Bike magazine

<div class='quotetop'>QUOTE (yamaka46 @ Feb 11 2008, 10:52 PM) <{POST_SNAPBACK}><div class='quotemain'>mmmm. cherry picking again Barry....

If you keep this up we might start to think that you might not be as much of an engineer as you think you are...

<div class='quotetop'>QUOTE (roger-m @ Feb 11 2008, 11:06 PM) <{POST_SNAPBACK}><div class='quotemain'>been to google uni i suspect got a masters in arrogance

gee I bother to try to show you why I put forward the point and you carry on with childish prattle even while I'm typeing!! ....... well good luck to you .... go buy a two stroke !!

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:06 PM) <{POST_SNAPBACK}><div class='quotemain'>Not sure what you mean here Rog. ??

we are not talking intercoolers here Rog. its a two stroke where the air/fuel is sucked into the crankcase, then compressed, then forced up through the transfer ports into the combustion chamber. So whether or not you cooled it on the way into the crank its going to be warm by the time its gets to the combustion chamber.

With DI the amount being metered in has to be so small none of this really matters ..... as again ..... because it injects such a small amount that it must be burned before the exhaust port opens ... ie. very tiny amounts ie. a low power engine. So its a crazy argument really ... irrespective of how the charge is put in there the millisecond unburned gases leave the exhaust port .... its wasting fuel .... and High performance 2 strokes do this a lot .... so much so an expansion chamber put on it increases performance to a great degree at the RPM of operation of that chamber.

To get a two stroke to be fuel efficient and non poluting and yet turn out the performance of say a current motogp bike maybe it would need to be a 1000cc anyway ..... then they would have to have a test to check emmisions each race so there would be this huge game playing with getting just the right amount of fuel injected to give the max. power before emmissions were exceeded. What a nightmare.

Again its all because of inefficency and pollution.

Just to give you an idea of the type if tune of engine we are talking here ..... I have a little Johnson Outboard here .... 9.9hp and its a little bigger than 250cc ...... dismal by motorcycle requirements hey!!?? and its pretty fuel efficient and not that bad for emmisions. They also do a 15hp ... the only difference is the jet and venturi in the carby ... but I don't think they push that capacity block much past that as the thing becomes inefficient ....

And those outboards don't even have a chamber to do the suck the burned gases and bat the unburned charge thing ....

So what use would there be in putting a denser charge in when by DI they are virtually trying to minimise the charge to the amount before it exceeds emissions??
you were stating that by warming the fuel your bike would run better, dont try and put spin on it now. we can all read back . i only mentioned intercoolers because you bought up turbos and it was relevant to fuel temperature statment you made. if fuel was more efficient when warmed there would be no need for intercoolers.
petol is petrol, whether its being use in a 2 stroke or a 4 stroke.
on a sub note. diesel is more efficient if its warmed before being injected into the cylinder. your a diesel fitter aint you

<div class='quotetop'>QUOTE (roger-m @ Feb 11 2008, 11:13 PM) <{POST_SNAPBACK}><div class='quotemain'>you were stating that by warming the fuel your bike would run better, dont try and put spin on it now. we can all read back . i only mentioned intercoolers because you bought up turbos and it was relevant to fuel temperature statment you made. if fuel was more efficient when warmed there would be no need for intercoolers.
petol is petrol, whether its being use in a 2 stroke or a 4 stroke.
on a sub note. diesel is more efficient if its warmed before being injected into the cylinder. your a diesel fitter aint you

Nobody says you "warm the fuel in your bike"!! , that makes it sound like you heat up the tank or something!! .. I said it the air/fuel gets warmed goingt through the crank hence vapourises, and ignites well etc. (Gee Rog. don't go out there warming your fuel up will you!! read what I said better first ... or even better don't ever play with this stuff. )

All fuels ignite easier when heated diesel or petrol, some ignite too well .... and crank heat helps to vapourise the fuel ( again I say it ) ..... what more do you want me to say Rog.!! you throw in intercoolers ( which have no pertinence here ) then don't read what I wrote unless its got some "politics" value for you .... read the techo bits Rog. its more interesting.

And no .... no diesel fitter here ....... I am a Mechanical engineer and electromechanical test Technician ..... so I have come in contact with several types of engines as well as other mechanical and electromechanical devices

Just out of interest Rog. what do you do for a crust?

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 10:37 AM) <{POST_SNAPBACK}><div class='quotemain'>ah you are thinking turbochargers etc. ?? Maybe?

no, i was thinking of a few basic principles of physics..

1. cold air is denser than warm air....fact....and therefore contains more oxygen...fact.
2. because the air to fuel ratio must stay the same to burn with max efficiency, irrespective of revs or temp, an intake charge with more oxygen in it will need more fuel to mix at the right ratio...
3. if more fuel is burned, more energy is released...simple enough conclusion.....

<div class='quotetop'>QUOTE <div class='quotemain'>a cold charge does not ignite as easily .... mix that with some of the exhaust gases from the previous rev's combustion and it is not as easily ignited as a warmer charge

4. correct, a cold charge will not ignite as easily as a warm one...
5. igniting a cold charge doesnt seem to be a problem at all, what with spark plugs and all that!

<div class='quotetop'>QUOTE <div class='quotemain'>Heating fuel raises its Flash point, and vapourises the fuel better as well.

6. yes, hotter fuel evaporates easier, but do you want a fuel air bomb going off in the cylinder?
its called detonation and will reduce the life span of your engine to a hideously short amount...

so, how is it that a warm charge will help your 2stroker run better again?

hmmm, seems i missed a few posts in the interim!

maybe i should read them all now that i have seen them!

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:31 PM) <{POST_SNAPBACK}><div class='quotemain'>Nobody says you "warm the fuel in your bike"!! ,
Just out of interest Rog. what do you do for a crust?
i noticed you have edited your original post where you asked if we had notiuce your bike runs better when the fuels warm you are such a ....

im not about to share any information about myself with you, infact i normally skip most of your droll posts so ypour only one notch above ignore. ive said it before and ill say it again, you are full of ..... engineer my arse

2791:no_bullshit.jpg]

<div class='quotetop'>QUOTE (frosty58 @ Feb 7 2008, 03:51 PM) <{POST_SNAPBACK}><div class='quotemain'>thanks pete & sarto for your effort. good read. yes thanks pete and sarto.

oxley's got a good point but the 2 stroke in racing is doomed.

<div class='quotetop'>QUOTE (roger-m @ Feb 12 2008, 01:06 AM) <{POST_SNAPBACK}><div class='quotemain'>i noticed you have edited your original post where you asked if we had notiuce your bike runs better when the fuels warm
2791:no_bullshit.jpg]

Now that is ........!!

you even quoted it and its the same ...... mods can tell if I changed it .... thats a pretty gutless way out Rog.!

Heres's the relevant part of my original post:

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:31 PM) <{POST_SNAPBACK}><div class='quotemain'>Also it misinforms a lot about a well designed 2 stroke .... another sideline benefit that I think DI can never get is the warming of the charge whilst in the crank.

No mention of tanks being warmed or even just fuel ... I was quite specific as it is a real and well understood phenomena.

I think in your furvour to dispute anything I say you did what you usually do and thats half-read it. Then you go back later and claim its been changed

Gutless Rog.!!

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 02:19 PM) <{POST_SNAPBACK}><div class='quotemain'>Now that is ........!!

you even quoted it and its the same ...... mods can tell if I changed it .... thats a pretty gutless way out Rog.!

Heres's the relevant part of my original post:



No mention of tanks being warmed or even just fuel ... I was quite specific as it is a real and well understood phenomena.

I think in your furvour to dispute anything I say you did what you usually do and thats half-read it. Then you go back later and claim its been changed

Gutless Rog.!!
well put it this way, i cant find it anymore on the thread, mabe ive over looked. i think the real engineers on this boards no what youe about. nuff said ....

Just to add in on the fuel temperature:
Higher fuel/air temp is NOT wanted as it decrease the power as less air get in and it create self ignition. The trick is to enable the fuel to evaporate and one way to help this is to let it heat up, but the major thing in both 4 and 2 stroke injection is to enable small enough droplets. With a finly distributed mist it will evaporate soon enough to brun up during the stroke. It's not like it is in that much of a hurry to evaporate, that would again lead to detonation. In fact, a major contributor to cooling the aluminium piston is the liquid fuel that hit the piston. First as liquid it protect from the flame then most of it finally evaporate and ignite but as it go from liquid to vapor it also adds lot of cooling to the piston.

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:06 PM) <{POST_SNAPBACK}><div class='quotemain'>Not sure what you mean here Rog. ??

we are not talking intercoolers here Rog. its a two stroke where the air/fuel is sucked into the crankcase, then compressed, then forced up through the transfer ports into the combustion chamber. So whether or not you cooled it on the way into the crank its going to be warm by the time its gets to the combustion chamber.
nope, we're talking DI, so the bit about sucking air/fuel into the crankcase is irrelevant. BTW DI uses very high pressure, that tends to warm the fuel up quite enough. As far as warm/cold charges (bigAl) the ideal is cold air, warm fuel.

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:06 PM) <{POST_SNAPBACK}><div class='quotemain'>With DI the amount being metered in has to be so small none of this really matters ..... as again ..... because it injects such a small amount that it must be burned before the exhaust port opens ... ie. very tiny amounts ie. a low power engine. So its a crazy argument really ... irrespective of how the charge is put in there the millisecond unburned gases leave the exhaust port .... its wasting fuel .... and High performance 2 strokes do this a lot .... so much so an expansion chamber put on it increases performance to a great degree at the RPM of operation of that chamber.
Nope, putting in very small amounts is not what DI is about, its about putting in very exact amounts, hence the engine can be high powered. With DI engines there is no valve overlap (unlike a conventional 2-stroke) so the expansion chamber concept is not used and fuel wastage is kept to a minimum

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:06 PM) <{POST_SNAPBACK}><div class='quotemain'>To get a two stroke to be fuel efficient and non poluting and yet turn out the performance of say a current motogp bike maybe it would need to be a 1000cc anyway ..... then they would have to have a test to check emmisions each race so there would be this huge game playing with getting just the right amount of fuel injected to give the max. power before emmissions were exceeded. What a nightmare.

Again its all because of inefficency and pollution.
Now this really is BS. There are no emission checks for Motogp, just a max fuel limit of 21 litres. If you can manage the whole race on that then it is assumed that your emissions are just fine.

It used to be reckoned that a 500 2-stroke was the approximate equivalent of a 750 4-stroke, so to state you'd need a thou' is crazy. DI makes things better, not worse.


<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:06 PM) <{POST_SNAPBACK}><div class='quotemain'>Just to give you an idea of the type if tune of engine we are talking here ..... I have a little Johnson Outboard here .... 9.9hp and its a little bigger than 250cc ...... dismal by motorcycle requirements hey!!?? and its pretty fuel efficient and not that bad for emmisions. They also do a 15hp ... the only difference is the jet and venturi in the carby ... but I don't think they push that capacity block much past that as the thing becomes inefficient ....
Clue here is the use of the word carby. So you have a low powered old style marine 2-stroke. What is the relevance of this to the DI discussion.

<div class='quotetop'>QUOTE (BarryMachine @ Feb 11 2008, 12:06 PM) <{POST_SNAPBACK}><div class='quotemain'>And those outboards don't even have a chamber to do the suck the burned gases and bat the unburned charge thing ....

So what use would there be in putting a denser charge in when by DI they are virtually trying to minimise the charge to the amount before it exceeds emissions??
DI does provide a dense charge due to the high pressure air assisted injection. As I said before, DI allows metering of exact fuel amounts, not necessarily small fuel amounts.

<div class='quotetop'>QUOTE (yamaka46 @ Feb 12 2008, 12:32 AM) <{POST_SNAPBACK}><div class='quotemain'>Now this really is BS. There are no emission checks for Motogp, just a max fuel limit of 21 litres. If you can manage the whole race on that then it is assumed that your emissions are just fine.
In fairness, you may have to concede on this point. Whilst this is no doubt true from a technical point of view, in the current climate (political and otherwise) I don't think it would be acceptable from a public relations point of view to change formula to an engine with higher emissions. F1 are supposed to be going to biofuel or something in the future.

I also preferred the 500 2-stroke formula.

<div class='quotetop'>QUOTE (Babelfish @ Feb 12 2008, 05:36 AM) <{POST_SNAPBACK}><div class='quotemain'>Higher fuel/air temp is NOT wanted as it decrease the power as less air get in and it create self ignition.

so good vapourisation of fuel doesn't help an engine are you saying?


almost sounds like you are suggesting an engine works best at first start up. Which is usually a time at which even more of the detonatable fuel is fed in as the air/fuel does not ignite well until good vapourisation in occurring.

ANyway the main Issue with DI is ...... how are you going to make it work for a high performance engine? How do you get over the fact that to get the sort of charges they ran in a motogp bike ( or any high performance 2 stroke ) you waste fuel. Valve ported 2 strokes have long been thw way to go there, but they are usually only on the largest of engines as the don't spin that much ...... a two stroke valved motogo engine would require a cam and valve train that operates at twice the current rpm .... and they are at the limit now ....... its all been done to death in the past. DI is nothing new and is not for fuel eficiency at high performance ...... to cite it as the "saviour of two strokes" shows that even a modicum of research was not done. And as such I believe Mat Oxley has shown his true colours.

<div class='quotetop'>QUOTE (michaelm @ Feb 11 2008, 11:43 PM) <{POST_SNAPBACK}><div class='quotemain'>In fairness, you may have to concede on this point. Whilst this is no doubt true from a technical point of view, in the current climate (political and otherwise) I don't think it would be acceptable from a public relations point of view to change formula to an engine with higher emissions. F1 are supposed to be going to biofuel or something in the future.

I also preferred the 500 2-stroke formula.
But the whole point of the discussion is that with DI 2-strokes do not have higher emissions than 4-strokes. I was not suggesting that the formula should change back to 2-strokes. BarryMachine's comment on emissions testing was incorrect, hence my response.

I agree that we are never going to see 2-strokes in top flight bike racing again, and that we will lose the lower formulae to 4-strokes, but this is not because the technology cannot make 2-strokes as clean and as competitive. It is due, as you point out, to the political climate, to the fact that Honda hate stinkwheels, and to the fact that the general public are always going to see 2-strokes as "smelly, noisy dirty things" regardless of how clean they are made.

Actually, the noise is one thing that DI can't remove, and whilst people like you and I think that's a great thing (I love the riiiiing diing diiing diiiing and the smell of Castrol-R, come to that ) the fact that the sound is at the frequency of speech gives it a higher decibel reading than a 4-stroke. Given the whinging of people living near race tracks about noise these days, I think that that in itself is enough of a death knell for the remaining 2-strokes.

<div class='quotetop'>QUOTE (yamaka46 @ Feb 12 2008, 10:32 AM) <{POST_SNAPBACK}><div class='quotemain'>Nope, putting in very small amounts is not what DI is about, its about putting in very exact amounts, hence the engine can be high powered. With DI engines there is no valve overlap (unlike a conventional 2-stroke) so the expansion chamber concept is not used and fuel wastage is kept to a minimum

oh dear now you are even going against what the designers and users of DI are saying!!

it may be "exact amounts" but the fact is the "Exact amounts" for highest power, out of say a gp two stroke, is occuring when all the previous burned gases are gone and the combustion chamber is full of air/fuel at the optimum mix ratio. This only ever is nearly approached when some of the new charge goes out the exhaust port .... therefore s wasted .... even on a DI engine.

At GP level a 2 stroke engine was a "symphony of sonics and pressure waves" as much as a well timed set of ports...... they would still be the important things with a DI system ..... the only thing that would have changes would be how the fuel was fed in. You still have to supply an abundance of air/fuel for the engine to be at peak power.

I think you says it best with the idea of the 21 litres ...... look at how much fuel a 2 stroke GP bike used, how big was te tank they needed to complete the distance? How far would a 500 have got on 21 litres of fuel?? And yes you may be able to do that distance on a DI engined 2 stroke .... but most people would have gone home to bed when you crossed the finish line

Its all about eficiency ( everyone wants the last bit of energy out of any fuel they pay for ) and emmisions ( raw unburned hydrocarbons are supposed to be bad ).

<div class='quotetop'>QUOTE (yamaka46 @ Feb 12 2008, 11:06 AM) <{POST_SNAPBACK}><div class='quotemain'>But the whole point of the discussion is that with DI 2-strokes do not have higher emissions than 4-strokes. I was not suggesting that the formula should change back to 2-strokes. BarryMachine's comment on emissions testing was incorrect, hence my response.

I have never said the emmision test were wrong!!!

What I have said is that the engines with DI are operating under a different criteria, in terms of expected power output, than we had in motogp 2 strokes. They are engines operating well inside an envelope of performance at which the gass in the combustion chamber are being very well burned befor escaping out the exhaust. Ask for more performance and you play with a "fine line: in respect to this envelope. Ask for motogp type performanc and you dop the envelope in a puddle wait for it to go soggy and do burnouts on it!!

There really is a lot of ...... hmmmm not spin .... but selective informing with some of the info available on DI ..... these websites are sales pages too you know. But I note none of them push anywhere near suggesting they could be competitive in a race bike

<div class='quotetop'>QUOTE (yamaka46 @ Feb 12 2008, 10:32 AM) <{POST_SNAPBACK}><div class='quotemain'>DI does provide a dense charge due to the high pressure air assisted injection. As I said before, DI allows metering of exact fuel amounts, not necessarily small fuel amounts.

Can't you see that it really doesn't matter how exact they are there is only so much you can inject before emiisions come up too much. Its all sadly owing to the principle of piston ported engines, they have a limit.

<div class='quotetop'>QUOTE (yamaka46 @ Feb 12 2008, 10:32 AM) <{POST_SNAPBACK}><div class='quotemain'>Clue here is the use of the word carby. So you have a low powered old style marine 2-stroke. What is the relevance of this to the DI discussion.

The point here is that even with a carby they are pretty efficient if tuned ( supplied with a modicum of air/fuel mix.)

They are opearting with such a small amount of air/fuel fed in that they burn quite an amount of each cycles intake of air/fuel. Unfortunately at 255cc this amount is about 15 HP worth ..... dismal. I could wack a whopping great carby on them and put a new intake port and enlarge the transfer ports on it and maybe exhaust and feed it lots of fuel, whether by DI or carby and they would give me performance ..... but I could probably use the excess of burning gases coming out the exhaust to heat up the ocean I was running it in then, let alone heat it up by some emissions triggered planet heating thing.

<div class='quotetop'>QUOTE (BarryMachine @ Feb 12 2008, 12:53 AM) <{POST_SNAPBACK}><div class='quotemain'>so good vapourisation of fuel doesn't help an engine are you saying?

No i don't, did you read my post?
<div class='quotetop'>QUOTE <div class='quotemain'>almost sounds like you are suggesting an engine works best at first start up. Which is usually a time at which even more of the detonatable fuel is fed in as the air/fuel does not ignite well until good vapourisation in occurring.

ANyway the main Issue with DI is ...... how are you going to make it work for a high performance engine? How do you get over the fact that to get the sort of charges they ran in a motogp bike ( or any high performance 2 stroke ) you waste fuel. Valve ported 2 strokes have long been thw way to go there, but they are usually only on the largest of engines as the don't spin that much ...... a two stroke valved motogo engine would require a cam and valve train that operates at twice the current rpm .... and they are at the limit now ....... its all been done to death in the past. DI is nothing new and is not for fuel eficiency at high performance ...... to cite it as the "saviour of two strokes" shows that even a modicum of research was not done. And as such I believe Mat Oxley has shown his true colours.
Let me see, what engine improvments I can think of that was invented in the early part of last century and just in the end came to real use for racing or consumers.
- Turbo
- Super charger
- Twin cam
- Multi valve
- Rotary engines
- Desmo valves
- fuel injection
I'm sure if we study the history will find pnumatic valves, exhaust valves on two strokes and about every other thing reinvented the last 30 years or so, except elctronics of course.

What make these things work now and not then is the different materials, alloys, CAD and machining presition. This enable low cost, durable solutions to things invented almost a century ago.
10 years ago Honda said they were at the limit of possible bore (> 100mm) for a high reving engine with the VTR. Today Ducati run a 1200 with almot 10 mm wider bore with the max hp 1300rpm higher. (street version)
That is made possible by improvements in the injection, inlet channels and combustion chamber.
FYI, big bore engines have a similar problem with compete combustion because of the large area the fuel has to spread over in a short time and lack of fuel on the edges means burnt pistons and piston rings.

You have earlier suggested that 4-strokes are close to completly developed, electonics are they only part that have any real potential left. The above is just a small part of how very untrue this is. The problem with the 2 stroke is not that it has reached it's end of development but that very few are willing to invest in that development.


With the case of the DI engine I see your point regarding high powered engines but somehow I don't fined it unthinkable that they eventionally find solutions to these problems as well.
Also I can't agree regarding the heating issue. Heating is only one factor regarding vapourisation and AFAIK the issue with DI on 2-stroke motorbike engines has been the droplets size. This is the other way to go.

<div class='quotetop'>QUOTE (yamaka46 @ Feb 12 2008, 11:06 AM) <{POST_SNAPBACK}><div class='quotemain'>but this is not because the technology cannot make 2-strokes as clean and as competitive.

This is very wrong ..... its the whole reason two strokes have been dropped ..... do you think there were a bunch of "boffins" out there, out to ruin our fun just because we like two strokes??? Many of these boffins were the type of people who helped improve 2 strokes. They didn't sit at a table say " oh my dear no!! those gorshaweful blangy blangy two strokes are just too much to bear!!"

Even the engine designers knew that as soon as you talk emmissions and efficiency ...... the nails start going into 2 strokes coffin. It is only operable in a much smaller band of expected performance.

If you think you can make a fuel efficient high performance 2 stroke engine that outperforms a 4 stroke engine Yamaka .... then gee I'l help you !! we could make a sqidillion!! But I assure you I loved two strokes, I stil have around 2o various 2 strokes in my garage at home .... but I do accept scientific reason.

Anyway just ask Rog. He says he studied performance engineering, he should be able to fill you all in on this.