Chris White

[QUOTE=m42racer]"The most important product of modern cylinder head design is the turbulence created in the combustion chamber – a pretty tough thing to measure. The propagation of the frame front can be greatly effected by the turbulence, by as much as a factor of two. "

Good thing I was talking about turbulence in the combustion chamber, to be more accurate you want swirl but turbulence is good too.

I suppose you have a swirl meter that works inside the combustion chamber while it is running? Mapping flow inside the port is simple enough but it doesn’t answer the real question – what is the mixture doing once inside the combustion chamber.

So let me ask this, since you seem to know lots about the subject – what is the speed of the flame front in a 951 engine?. Feel free to narrow it down to any boost/rpm level you wish.

Nope. Wrong, on so many levels. I won’t even go into it unless requested.

Two important things to remember –
1) its all a system, find the weakest point and improve that. if you improve something that is not a limiting factor then there will not be any significant improvement.
2) Its all about combustion – what takes place inside the cylinder. The better and more uniform the combustion the better the performance possibilities are. Look at the differences between the 8v heads and the 16v heads in the combustion chamber/piston quench designs and you will see where some serious power differences can come from.

Bengt Sweden

This is too confusing to go unanswered.
Turbulence is what you have when you don't have laminar flow. At high velocities, like in our case, there is no chance to get laminar flow except very close to the walls, and that is good because with laminar flow velocity is zero close to the walls and only successively increase towards the flow center.
Turbulence is a flow property telling that the media can't transfer shear forces, it can't t occupy space and it doesn't hurt velocity since it actually means that it is undisturbed by wall effects.
Swirl as Chris mentions is a different thing.
Bengt

m42racer

"So let me ask this, since you seem to know lots about the subject – what is the speed of the flame front in a 951 engine?. Feel free to narrow it down to any boost/rpm level you wish."

I have no clue. Please accept my ignorance here, but I am very interested in this subject. Would be so kind as to give me some information etc, with calcs etc, so that I can better understand what I do not know.

Originally Posted by m42racer
"The question was asked if wet testing reflects what air does. Yes it does. Liquids and air do similar things under the same conditions.

"Nope. Wrong, on so many levels. I won’t even go into it unless requested."

I request it. Also, please inform me as to why companies like Superflow, Audie, GM, Ford, Saab, Recardo develop wet testing equipment to flow manifolds, heads etc. I won't take a cheap shot at you, but seems to me that these guys do this for a living, and you do what you do.

I have seen this wet testing done, and it does tell many things that simple flow testing cannot. It has shown on dyno testing that the information gained has produced better engine running results.

I for sure do not know a lot about this subject, but I have seen this testing done, and have been told by many race engine designers that turbulence in the ports are not a good thing. What happens in the chamber is not what this discussion was about I thought. I thought we were discussing the flow thro the ports. Maybe I misunderstood what this discussion was about.

As for what happens in the chamber, I'm sure you are right again. But it won't happen very well if nothing gets in there. And that is a function of the manifold etc is it not?

I happened to met an Cylinder Head engineer from the English development company Recardo at the UK racing trade show at the beginning of this month. He is working with PD on some projects PD are doing for somone. I did ask him about this wet testing and the new technology in computer port mapping. It was very interesting how different parts of ther port and chamber can be measured. Anything you can offer here would be most useful. Information from 2 sources is always better than one.

J Chen

Wet testing is nice cause it will allow you
to ' See & Identify ' how & where the flow
moves but the set back of this is that the
medium used as compaired to air has different
properties especially at high flow high speed rates.

Skunk Workz

Oh yes it will... Let's say it this way: If you wanted to build a whup-a$$ 944 NA 8-valver,getting the big 3 as first syllable on your engine dyno sheet,revving 8k +...you'd need about 38mm dia. It all comes down to how much boost you will run. But given that you go for the typical 18 psi, and you make it flow as much as possible WITHOUT increasing the area much (good valve job,gentle clean-up,slight re-shaping), I think that head would work very well,even if the displacement is 500 cc's more...I have yet to try that combination,but I will go for something like that myself. Right now I have to get the 944NA-heads I'm working with done..

TurboTommy

Skunk,
I can't believe you're relying on your software program to come up with these figures.
One can achieve 120hp on 600cc high compression four cylinder at 100% VE (or slightly more) if the engine's peak power is up around 13,500 RPM.

I doubt you and your software really know what 125% VE really means (as described very briefly in my post about absolute psi in the cylinder).

I'm not questioning your take on the improvement that can be had in the case of the 944 series intake ports. I'm just saying there might be an improvement of 5% on top of the stock 85 to 90%.

If you actually have stumbled on a way to achieve 125% VE on an IC engine, you will soon be a multi millionaire. You will be bathing in laveander, you will be eating in the finest restaurants, you will be buying two Carrera GTs (one for you and one for your live in high priced Call Girl).

Please somebody chime in here and tell me that I'm mistaken.

m42racer

I was hoping to hear back with the information/calculations about the flame speed etc. I'm very interested in this. I'm not sure where this came into the original discussion, but now that it is, I would love to know more about it. Calculating the speed etc. It seemed that it was thrown out there to challenge my knowledge etc. I know only what I have been told and read. Most of it is so beyond me that I probably get it all mixed up and wrong.

I'm really interested in hearing from Mr White as to why he thinks this new technology of wet flow testing is "wrong on so many levels". Why would they create a testing procedure with liquids if it did not represent how the air moves and behaves in the port.

These discussions are typically amongst us owners and enthausists who only know part of or very little about these subjects. If we knew more we would be doing it and not talking about it. I am sure we can all learn something here from those that contribute. Some that contribute need to stick to us ignorants, as they would be way out of their league discussing these subjects with known experts.

ehall

PPPPPIIIIIIISSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS!!!!

I just wanted to try to win this pissing contest!

Skunk Workz

Ok...the F1-guys use software for their cars,and so do NASA...go ahead and doubt them,on the ground they use software. Like I said before,I don't care if all people will belive me,somebody will actually TRY IT before they claim it's not possible...and they won't claim that,because they will feel like the Mythbusters...busting the myth that more hp/better power off boost/etc is not possible on the 944/951's.
Not hp...RWhp. On pump gas. Still possible,I know. But the stock bike has about 102 to the wheel...and we increased the rpm by just 250 over stock,so it's not from revving it a "few thousand more". And we DEcreased the intake port size,it flowed 6 CFM LESS than stock... You tell me where all that hp came from.

If you know it so much better than me,go ahead and tell me how it's done,then...VE is proportional to...you end the sentence,since you "obviously" know that I am wrong.

If you just go for flow,yes. If you take the speed of the intake charge into account,you can have quite a bit more than that.

I don't think so...I'd sure like that,but that won't happen,as there are plenty of really good tuners doing that around the world already...I doubt you'll ever find a really competetive engine in racing today having less than 115% peak VE.

ehall

Damn, I'm almost out of ****. I may not be able to win this one...

Chris White

I thought it was getting interesting – is a multiway pissing match, two or more threads going in separate directions at the same time!

Just to contribute my points as per m42racers request –
I will start a new thread on fame front propagation and what it means tomorrow. It is relevant to the original discussion in tangential sort of way. seems it deserves its own thread. I did not toss it out as a challenge – it is my current ‘holy grail’ and I will be happy to chat (write) about what I know so far. I wish I knew more and I don’t claim to be a true expert on it….in fact I can’t find a true expert that will talk!

As to the “I'm really interested in hearing from Mr White as to why he thinks this new technology of wet flow testing is "wrong on so many levels".” I suppose I should answer that so ehall can have time to replenish his supply!!

I would suggest that the item I was referring to gets reread.

“The question was asked if wet testing reflects what air does. Yes it does. Liquids and air do similar things under the same conditions.”

Air and fluid act quite differently yet you say they act the same. That is one level that your statement is wrong. If you don’t get that basic premise then I give up. Too much for me to cover. Fluids can model SOME behavior gases have but not all.

There are some very good things being done with fluid analysis but that does not make the ‘similar’ quote right. You have mistaken what I wrote, I think fluid analysis is a good tool and I never mentioned anything negative about wet testing. I do think that ‘flow bench’ testing that gives you a CFM rating is way over blown. It does not measure quality, only quantity and once you get past a certain point additional quantity doesn’t add anything.

Just so you know why I react the way I do to some posts, it is statements like “Not true. well documented and tested” that rub me the wrong way. You missed the point but instead of asking for some clarification you decided to make some statements that implied that you know of these things. The point that I was making is that porting and polishing can and will have an affect on the flame front propagation (obviously in the combustion chamber) due to changes in the way the mixtures acts in the combustion chamber during combustion. Sure, you can measure and model some of the effects in the chamber but you can’t do it during combustion (maybe the top of the field F1 guys have this but I find it useless to discuss testing technology that is not available to the general public and will never be applied to 944 engines).

Chris White

Russ Murphy

By the way I'm not being facetious. Thank you for your conciseness Chris.

Peckster

No. Especially if you don't know what you're doing.

ehall

"maybe the top of the field F1 guys have this but I find it useless to discuss testing technology that is not available to the general public and will never be applied to 944 engines)."

I HAPPEN to have an F1 buton right here on my key thingy, next to the ESC button thingy....which does thisss... so SOME of us DO have this technology

Eyal 951

So what i have here, in your humble opinion is worthless? What is everyones take on this: