Dart 180 cc alloy head as cast

[CGT]

how long to make a flow test at any given lift ??

How about timed flow testing?

[MadBill]

Seems like given the intake pressure delta info and referencing the related valve lift, one could determine what regimes would be the most fertile for development.

[GARY C]

what i am trying to say is flow and velocity increase with depression,how much depression does running engine have at peak demand ??

Right, on a flow bench we keep re-setting the depression to the industry standard of 28",..
and take how long to make a flow test at any given lift ??

How directly does that relate to something happening in a fraction of that time ??

Randy

So do you think not having an industry standard would fix things or make them better?
If so, how?

[CamKing]

So do you think not having an industry standard would fix things or make them better?
If so, how?

For our calculations, we convert all port flow cfm to 1" pressure.
For port development, I recommend flowing at the highest pressure your bench will allow. Mistakes in the port show up easier with the higher pressure.
All the 28" standard does, is give you a way to compare numbers, without having to convert them to the same pressure.

[CGT]

Published intake-to-cylinder pressure delta traces I've seen from running race engines vary during the intake cycle from well over 100"Hg. to single digits.

I think what Randy is saying, he can correct me if I'm wrong, is that your not only dealing with the large pressure delta that the flow bench can't quite simulate but also a definite "response" time through the lift curve that is definitely not happening with a flow bench. How much time elapses during the process of you flow testing every .050 or .100...then readjusting depression accordingly. It varies im sure, but for sure takes you longer than the shortblock would be demanding it.

A better response time could deal with changes in piston placement/demand, bi-directional flow and waves faster and more efficiently. Throughout a cycle an engine can be not only flow limited but depression limited as well. Depression is constant and readjusted back to the standard when flow testing(your engine doesn't do this). You can calculate piston demand at any point you want, but these formulas that get commonly used don't come close to taking any of these time factors in account , just simple basic guidelines based on your flow at these steady state depressions.

A higher flowing head may very well not always be a higher flowing head....it may be constantly, unsuccessfully trying to find its former flow bench glory on a running engine

[SpeierRacingHeads]

Or you can us these programs, use the flow bench, and gather results, then apply them accordingly.

Smart people have been doing this for decades with record, championship results.

Engine is all math and physics, debate that all you want.

If you can't see a trend with programs vs flow bench data, your just not being honest with yourself.

If people weren't so blinded by the poster, I have posted up stuff recently that confirm this. All you need to do is look at it with an open mind and you will see no one is lying to you.

And for those reading along, Pipemax is used by almost all of the Professionals. For sure all I know and talk with on a regular basis. It's just a fact.

[GARY C]

So do you think not having an industry standard would fix things or make them better?
If so, how?

For our calculations, we convert all port flow cfm to 1" pressure.
For port development, I recommend flowing at the highest pressure your bench will allow. Mistakes in the port show up easier with the higher pressure.
All the 28" standard does, is give you a way to compare numbers, without having to convert them to the same pressure.

What flow " do you convert to 1"?

Hasn't the 28" standard been used over the decades for other formulas?

It seems it would be almost impossible to have a forum or any discussion on an engines performance or lack of if everyone was working at a different test pressure, I am sure that a higher pressure could help you find issues when developing that a lower pressure may not relieve but you would still have to what it is you are seeing and what to do with it and there would be few in the industry that could give you any data/info for an odd bench pressure, I think it would be great if the standard was higher but it seem even that to a point coverts back to the same cfm at 28"?

[SpeierRacingHeads]

Everything I do here with my CNC stuff is done at 50".. You will see stuff at that pressure you don't at 28"..

[CamKing]

What flow " do you convert to 1"?

Whatever the port is being tested at, we convert it to 1" pressure drop. Over the years, we've seen port flow measured at 3", 25", 28", 50", and higher.
There's nothing magic about 28", it's just a number. It's good to have a std, just for comparing, but that's all it's for.

[randy331]

how long to make a flow test at any given lift ??

How about timed flow testing?

Something along those lines.
I remember jon posting about swirl on a bench and how it takes some time to stabilize as the swirl speeds up and it will flow more because of it, but on real engine it doesn't happen that way. There is a piston in the way. How does it happen on the running engine ? How different is it at 4000 rpm vs 8000 rpm? How much of that swirl is there on the engine ??

How about cases like we've seen where a head flowing less makes more power ?

Or how do you simulate what I seen on my 421 re dyno session ? A head that quits gaining flow at .700" lift with .765" lift on the engine respond like it did to higher ratio rockers that took it too over .800" lift yet that same test has netted no power gain on other engines ?
That 10 average HP from 6000-8500 rpm with most of the gains being over 7000 rpm will sure make the truck pull better, and there is no way to find out without trying on a dyno.

Those are the types of things you can't simulate on a flow bench.
And none of the sims I've used would have predicted that power gain. I'm sure there are high end sims that will and maybe I should look into them.

So what's a better flow test is the question ?

Randy

[GARY C]

I wonder if people on construction forums talk about the best way to build something using the industry stnd measurements and lingo or if they just turn everything into arguing that 1 foot really isn't a foot?

It is just strange that the few who want to start this argument year after year after year after year use the same tools and industry standards when developing their engines as the rest of us.

[CamKing]

I wonder if people on construction forums talk about the best way to build something using the industry stnd measurements and lingo or if they just turn everything into arguing that 1 foot really isn't a foot?

It is just strange that the few who want to start this argument year after year after year after year use the same tools and industry standards when developing their engines as the rest of us.

When I started, the industry standard for flow bench pressure was 3". Then it went to 10". Then to 25". Now it's 28"
If no one questioned the industry standards, we would still be using 3".

BTW, the industry standard for designing a cam profile used to be, choosing a nose radius at a given distance from the base circle, choosing the opening and closing points, and draw tangent lines between the opening/closing points and the nose radius.

[GARY C]

I wonder if people on construction forums talk about the best way to build something using the industry stnd measurements and lingo or if they just turn everything into arguing that 1 foot really isn't a foot?

It is just strange that the few who want to start this argument year after year after year after year use the same tools and industry standards when developing their engines as the rest of us.

When I started, the industry standard for flow bench pressure was 3". Then it went to 10". Then to 25". Now it's 28"
If no one questioned the industry standards, we would still be using 3".

Do you know of any published data on a cylinder head breakthrough from flowing at a higher depression? I know Darin talks about t for an Indy head, it would be interesting to read what people have found.

I know DV talked about wanting to see a highly pressurized exhaust flow bench but it never came to pass.

I think size, velocity/air speed is more telling but I bet there will never be a consensus on whats best there either

[steve cowan]

Randy,
i just re-read the 2017 EMC thread again,great thread
interesting chat about oil pump and pressure,vac pumps and oil pans,really enjoyed the read and also read the magazine article on your 2011 383 that made 606hp.
on the 2017 emc thread one of your closing statements was-
ONE OVERLOOKED FACTOR IN MAKING POWER AT EMC TYPE RPM IS LACK OF DEPRESSION NOT LACK OF CFM.
can you expand on this -

[CamKing]

]Do you know of any published data on a cylinder head breakthrough from flowing at a higher depression? I know Darin talks about t for an Indy head, it would be interesting to read what people have found.

Ask the head porters, but most don't like to publish their breakthroughs.
I have personally seen problems with the port, become noticeable with the higher pressure. Problems that would have gone unnoticed, if only flowed at 28".