M20 Management shootout, MS2 vs Haltech vs?

[ForcedFirebird]

plenum size vs flow

http://sssquid.com/v2/plenum-size-effect-intake/

would be curious to see the manifold tests since most bench tests I've seen aren't really fit to test intake manifolds. Pushing air through a manifold is different than a vacuum system with non-flowing wall conditions and alternating each port with parabolic vacuum environmental conditions

My bench fits the manifolds and Digger borrowed that pic from my posts. We do real world testing with the manifolds attached and TB pinned open.



As far as blow and draw through bench, you would only ant to blow through in a turbo situation, just like the engine it would be running on.

Usually the problem lies in people testing with too little depression, we use as much depression as we can, then convert to the typical 28". When flowing at 10" (which a lot of companies do), the numbers are skewed higher.

what? No, the boundary conditions have nothing to do with the manifold.

Not sure if boundary is being used in the same sense I am used to discussing it, but boundary "layer" has a lot to do with flow.

Does the CFD take sound waves into consideration? The runners are a good length for capturing them and curious if they help cylinder filling.

[digger]

what? No, the boundary conditions have nothing to do with the manifold.

the ENGMOD4T website looks like it hasn't been updated since windows XP and they use comic sans. There's no info about how to get the software either, other than a contact form. I'll see if they're still alive though, seems like neat software

contact Neels and paypal him and he'll email. you can get a 1 month trail free if you ask nicely

http://vannik.co.za/Contact.htm

this is very off topic but they do indeed influence it and sometimes alot when youre doing a comparison depending what is different, consider this how do you know what the boundary conditions are on the outlet of the manifold? have you assumed a time varying pressure?

[squidmaster]

Since you're all experts in every field that's ever exited, you don't need me to tell you anything. I guess my 13 years in the field and college degrees have taught me nothing at all. oh well.

[digger]

Thanks for the info, do you know what headwork /cam this engine had at the time?

MM rally head and cam

[squidmaster]

Anyone want a hack up a manifold and put a maf sensor in each runner? Would be probably the only real test we can do haha

[digger]

boundary conditions in the definition that I use has to do with the software. It's the defined inlet/outlet conditions, and had nothing to do with the design itself.

and what do you mean by sound waves? The sound waves from what? What are they affecting in such a way that airflow is affected in any noticeable way? I won a partial college scholarship from my work with sound wave manipulation/direction, so this is no foreign topic.

in order for sound waves to cause any change, it has to be pretty massive

http://www.livescience.com/38181-soundwaves-levitate-objects.html

https://en.wikipedia.org/wiki/Sound_power

according to Gauss's theorem, a soundwave of about 145dB would have to be propagated from a real wall surface traveling at over 3600m/s against incoming airflow of 175m/s (not even maximum velocity) to have much effect. This simply isn't happening (rough estimations. google the equations and spend the time if you want, it's new years, I'm drunk)

My software is coded to apply the back pressure of the valve closing, each vacuum point of the valve opening and closing, and a real wall condition for every cavity with a non flow condition.

Unless the bench test has the camshaft hooked up and rotating, and has vacuum hooked up to each intake port, it's kinda hard to say just how much each new flow condition will affect each other. I'm not saying it doesn't tell you anything about the manifold, it just doesn't have all the necessary abilities to necessarily show everything you might want to know about a manifold since we aren't just dealing with one steady intake port with one steady flow.

everything looks smaller on my model because I used .5mm walls without any heat radiation calcuations. I was only concerned with the internal flow conditions. The real manifold uses massively thick walls, which makes it bulkier looking than flowing.

the manifold influences cylinder pressure downstream of it which then influences how the manifold itself behaves. this is why OEMs now model pistons and moving boundaries but who's got a super computer on hand...

can you plot each runner mass flow superimposed on a graph and also total mass flowed during one cycle for each runner?? i'm curious how uneven
the distribution is

[squidmaster]

information? Where?

[digger]

Check out the graph I posted one page back in this thread.



Cylinder draw parameters are the same with or without a manifold attached. I define how much the piston draws for how long. It has literally nothing to do with the manifold at all. If each of my boundary conditions were manifold dependant than my comparison tests would be absolutely useless. The same engine will attempt to draw the same amount of air for the same amount of time regardless of manifold. The restrictions in the manifold are what affect the outcome, which is what I measure.

There results that I obtain from my tests are the results of the manifold design, which is the whole point of the tests. If I were to change the parabolic valve equations it would mean I've changed the engine parameters, completely separate to the manifold design that is stuck onto these environmental lids.

I understand that it isn't perfect because I didn't model the entire engine and code in compressed air/fuel combustion (which is beyond my pay grade to be quite honest), and model in the entire exhaust system. But I'm not as worried about all of that because I have a baseline of what the engine CAN induce without hinderance, I have what the M20 manifold does, and I have what my manifolds can do, all compared using identical constants-- that's a true scientific test, and one that shows through simulation that the M20 manifold blows serious balls.

But, like I said, the only REAL way to test the manifold would be to stick maf sensors inside the runners and measure real-world conditions.

All I'm saying is a 1d analysis shows that the manifold itself has everything to do with how the piston draws and how long for. So comparing two manifolds with an identical piston draw using cfd like this may lead you up the garden path depending on the manifold details that you change or are comparing.

[ForcedFirebird]

http://www.livescience.com/38181-soundwaves-levitate-objects.html

https://en.wikipedia.org/wiki/Sound_power

according to Gauss's theorem, a soundwave of about 145dB would have to be propagated from a real wall surface traveling at over 3600m/s against incoming airflow of 175m/s (not even maximum velocity) to have much effect. This simply isn't happening (rough estimations. google the equations and spend the time if you want, it's new years, I'm drunk)

So sound in the intake doesn't work like exhaust? I was more implying the sound waves helping, as in many tuned runner manifolds (like **choke, choke** GM's "TPI").

https://en.wikipedia.org/wiki/Inlet_manifold

We find a lot of cars in the late 70's into 80's had overly long runners. You have to remember that unleaded fuel was still new, emission control was becoming standard. All the MFGR's thoughts at the time were to make more TQ (long runner, small plenum), keep static CR low, and trapped mass high.

[ForcedFirebird]

The link talks of Helmholtz resonance, which I am probably confusing with sound waves. Guess what I should have said is reversion. The intake and exhaust valves are open at the same time for most cams, so pressure (and sound) do escape back into the manifold. Not questioning your tests specifically, just wrapping my head around it all. It's easy to look at in Dynomation software, you can "freeze" the entire engine sim and see all the pressures (trapped mass, reversion, even air speed), problem is the inputs have to be extremely accurate and we haven't put all the m20 data in yet.

Have you calculated/measured the length and volume of the m20 runners?

You're right about the only way to truly tell would be to have a MAF on each cylinder. Would be a really cool/fun analysis.

Earlier you mentioned a cam on a flow bench, but overlap wouldn't work well in a static situation. We attach manifolds more to see how the intake port reacts to the intended manifold. Bare head flow is not always a great indication. You might gain xx flow on a bare head and a different port shape might actually work better once it's all bolted up.

The biggest surprise we had on the m20 is no mater the seat cut, +1mm valves make them flow worse until the port is worked over.

[digger]

@John: Those aren't "sound waves" in that anything is generating a sound, but the compression and reversion of the air after the valves close, which, like I said, I have taken into consideration in my simulations. I don't know about that link you posted, it mentions sound waves 0 times and only talks about what I've been talking about.

The tuning I've accomplished in my manifold designs directly deals with this issue.

@Digger: How does a manifold change the internal dimensions or properties of a combustion chamber, the stroke of a piston, the compression ratio, or anything else about the internals of the block or head? Please explain this one to me because obviously I have absolutely no idea what you're talking about.

the first thing to remember is the next cycle depends on what happens on the previous one. So If the manifold behaves differently then it causes different cylinder filling meaning there is a different amount of mass trapped in the cylinder during combustion.

So given there is different amount mass to expel this will blow down differently which produces a different exhaust pressure during overlap and different residual cylinder pressure at IVO.

The overlap starts flow into the cylinder so certain manifolds might not fill well early in the cycle because it changes overlap but make up for it elsewhere. Without modelling the whole has dynamics you can't compare different manifolds unless the changes are subtle because the assumption that cylinder draw is the same is rarely correct.

If you wanted to develop a manifold using engineering and physics start with 1d to get areas, lengths, volumes and plenum configuration. Then once you've got that start looking at the 3D effects that cfd gives using data from 1d as the input . This is my opinion.

[MercyFlush]

the first thing to remember is the next cycle depends on what happens on the previous one. So If the manifold behaves differently then it causes different cylinder filling meaning there is a different amount of mass trapped in the cylinder during combustion.

.... /SNIP/

If you wanted to develop a manifold using engineering and physics start with 1d to get areas, lengths, volumes and plenum configuration. Then once you've got that start looking at the 3D effects that cfd gives using data from 1d as the input . This is my opinion.

I agree,

This is the reason that most 1D flow simulations (Ricardo wave etc.) use iterative solves.

You can easily get numbers that *look* correct by doing some excel hack job (not implying that anyone here is doing that though) but to even get a ball park of real cylinder filling characteristics you need to be doing all kinds of calculations regarding compressible fluids pertaining to the densities, velocities (inc. gas reversion) etc. all particularly important when dealing with a shared plenum as the pressure waves induced WILL cause massive changes in local pressures (if utilized properly).

Each property plays a small but critical part in the accurate determination of mass flow rate, which in the end is all we really care about.

Also, a MAF on each cylinder is probably not going to easily work (or accurately) on anything but a bloody expensive one! There is a lag time in the sensor as well as effectively a minimum amount of time of flow to determine the mass flow rate, as you are relying on the air moving past to introduce some temperature delta on a thermally monitored/controlled device (Hotwire/film etc.). I would LOVE to see if someone can do it though :D

I understand where @squid is coming from too. He is looking at the engine as a vacuum pump as it it will essentially generate an approximately fixed level of vacuum at X point in time. The only issue I can see with this is the cylinder pressures are not exclusively generated from the piston displacement, but consist of the scavenging of the exhaust and the pulse tuning of the intake so on, which in a real performance application is life and death.

Definitely lots to think about! That's why I only use programs such as the Ricardo suite which are proven (through extensive peer reviewal and industry use) to provide accurate 1+D analysis :D

[squidmaster]

I came here to offer information for everyone based on months of work, research, and repeatable experiments. I guess i have nothing to offer those that already know everything. You guys are a riot.

[ForcedFirebird]

And John, you disagreed with me, send me a link that proved what I was saying, then tried to disagree while agreeing with me? I don't get it, man

Huh?

Told you I was just wrapping my head around what you are doing and what was involved.

[digger]

For the first time I felt like using a reaction GIF. Something with a valley girl holding star bucks saying "OMG" but I'm not going to google it.

@Digger: dude, you know a LOT. I often send people your way if they are in kangarooland, but you've got a huge misconception about how the tests works, what and where I am measuring, and the phrase "boundary condition".

Look, you people are obviously wildly misunderstanding everything about even the basics of what I am doing. Trying to avidly find fault with something you don't know about, while letting a nearly useless benchtest off the hook as definitive? Right. Do any of you even know the NAME of the program that I use? Or the basics of how it works? Okay.

And John, you disagreed with me, send me a link that proved what I was saying, then tried to disagree while agreeing with me? I don't get it, man.

I'm out.

It's ok I've been doing engineering simulation ( don't mix test and simulation terminology it's confusing anything within the software is not a test and doesn't measure anything unless you're doing a physical test or experiment.) for well over a decade so I actually know a thing or two about the approach for doing these things and getting them to match physical tests without it basically being a trial and error pretty picture generator.

You haven't done a good job explaining what you did with your boundary conditions but it sounds like it's just an assumption ( years ago when I used the older version of solidworks flow program which is what it looks like you might be using, it asked for pressure vs time table input which you could apply to the face being the outlet ). My assumption is its unlikely you've used a high speed pressure transducer to get real data at each crank angle and input this into the boundary condition as its expensive equipment. What did you input exactly and what format. So your assumption may not be right is all I'm saying, sometimes it doesn't matter if its just a relative comparison but It depends what you're actually hoping to get from the analysis. The true behaviour at the boundary is a lot more complicated than you think and if you don't capture this you might not get what you want from the analysis because of potentially false assumptions.