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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old February 1st, 2011, 14:44   #16
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Quote:
Originally Posted by MarkoP View Post
Many in this tread have mentioned that running engine has much bigger depression than what you can archieve with flowbech..

MarkoP, Thankyou for turning my head upside down, I see what you are geeting at. I was certainly guilty of having presumed the larger pressure difference, but having re-thought it quickly if we were to map the cylinder pressure againts the MAP through the induction cycle he prssure difference would have to be much smaller in comparison to MAP other wise the flow would increase to balance it out. What the MAP under high boost does is to increases the density of the gas flowing not the speeds or the relative presurre differential so the bench test probably still stands as a good measure of change to performance.

Does anyone know of some real life data for the rpm's we are inetersted in tha we could see?

I presume the pressure difference will be negative at inlet valve opening quickly reducing to a small minumum then increasing to a maximum at just after Mid way down and then reducing again up until Inlet valve closes.
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Old February 1st, 2011, 20:21   #17
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I'm no expert in this field by any means - Just thinking about the subject at hand.

For turbulent incompressible flow the reduced equation is:

Q = A x Cd x sqrt(P1-P2)

Q = Volume flow rate
A = Area of the hole
Cd = Combined Discharge Coefficent of the area A - how efficient the hole is
P1-P2 = Pressure difference across the area A

The gas IS compressible and I'm sure that there is laminar flow at very low valve lifts, but for the most part to get the idea across the above simplified equation works well.

To increase the flow we can increase the area (open the valves more), improve the Cd (porting, valve angles, etc) or increase the pressure differential (more boost).

The pressure differential across the valve for a given RPM will be proportional to the boost pressure. The cam timing and rod ratio will determine the basic differential for a given RPM - given the high compression and very close valve to pistion clearances at TDC, the piston is on it's way down before the intake valve opens so there may be a higher than boost pressure dP at the beginning of the intake stroke. Yes, there will be some interdependance as a better flowing head at the same port pressure will fill the cylinder better creating less dP across the valve since the piston rate of displacement is constant, but again, generally speaking, more dP will yield more flow. The only way to really figure this out is to have in cylinder pressure measurement and compare it to port pressure and measured flow.

How well it will all extrapolate from ~1+ PSI to 30 PSI is a little bit of a moot point as flow bench data is stead state, whereas nothing in the actual dP or flow rate in the engine is steady state. The flow bench is just a way to compare relative gains/losses in steady state repeatable conditions.

Just thinking outside the box here....maybe one could take a long block, drive it with an electric motor and have a huge (55 gallon drum size) supply plenum to the intake manifold that has a mass airflow meter on the inlet of the plenum which will give an average mass airflow rate. You could pressurize the plenum to see the effects of boost pressure on mass airflow as well as adjust cam timing, duration, lift as well as rod ratio, etc with RPM.

Sorry Alex22 - Didn't mean to hijack your thread here. A before/after test with/without the swirl meter and comparing CFM's is a good idea to see how much of an effect the swirl meter has on the flow rate.

Keep up the good work!
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Old February 2nd, 2011, 01:05   #18
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The main reason that I am flowing the head at 28" of depression is that it is one of the industry standards and I will have something to compare flow results to, that and the DC tachometer is only rated for 8000 RPM and I would rather not find out how long it can be driven above its maximum speed. Another thing to keep in mind is that the SF600 draws almost 40 amps on a 220 volt system and it is only capable of about a 1.5 change in pressure. The amount of power required to test at 30psi is just unreasonable for 99% of the people out there.

A running engine is a dynamic system and the flowbench is a static testing machine, but that doesn't mean that information gained on a flow bench is not useful. The flowbench allows the operator to not only measure how much air is moving through the port per unit time and in my case the swirl in the chamber, an experienced operator can make observations based on sound and test probes. All of that information combined will give a very good picture of how the air is moving through the port. From there problem areas can be identified and modified and the head can be flowed again to test the head porter's work.

Here are some results from the last 2 days of porting.


From the way things are looking the finished port design may have some weld added to certain areas and have some very funky shapes, but I'm nowhere near finished with the testing so that plan could change any day. The results posted are from repeated tests on the same port. Some of the grinding that I did reduced swirl or flow and since there is no eraser on the back of the die grinder and welding takes too long those areas are still in the port. Once I get a good idea of what adding or removing material from each area of the port does and how they work together as a system I will apply all of what I have learned on a fresh port... then probably more grinding and on to another port...

What do you make of these results and do you think there is any to know just how much swirl the port needs and how much can be sacrificed for flow?

No exhaust numbers at the moment.

~Alex
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Old February 2nd, 2011, 09:12   #19
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Testing at 30 PSI pressure drop is non-sensical. Flow becomes choked at a critical pressure ratio of 0.528 for air; the absolute values of the pressures do not matter; the ratio of the drop does. Keeping the measurements at 28" water with inlet pressure being ambient keeps results consistent with almost universal practice, so keep that up Alex.

Edit: pictures added. The critical pressure ratio comes from (2/(κ+1))^(κ/(κ-1)) -- some may know κ as γ (gamma) instead.



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Old February 2nd, 2011, 11:10   #20
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There is a clear trade-off between swirl/tumble and flow. The more flow you want, the more the swirl/flow must be compromised. No free lunch.

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Old February 2nd, 2011, 13:11   #21
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Quote:
Originally Posted by TDIMeister View Post
Testing at 30 PSI pressure drop is non-sensical. Flow becomes choked at a critical pressure ratio of 0.528 for air; the absolute values of the pressures do not matter; the ratio of the drop does.
Would 0.528atm be approximately 970fps or 0.87mach?
..I am not so good in math.
That would mean ~153VE% potential which you do not see often with real life engines and I think there is some lower values to aim for when porting heads.

Quote:
Originally Posted by TDIMeister
There is a clear trade-off between swirl/tumble and flow. The more flow you want, the more the swirl/flow must be compromised. No free lunch.
Your the chief in here, but I have to disagree.
I have seen 80cfm/sq.in of valve area flow numbers from ported TDI head which is decent number when comparing any of 8v gasser production heads.
My swirl meter is still un-attached, but I assume that because smoke levels reduce under whole RPM band also flow quality must be better.
If not, then I would think that more smoke should be seen as long as RPM is high enough to get benefit of increased flow.
Also when larger valves are used, low lift flow is increased which reduces low rpm output even more.. but gives some to higher RPM band.
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Old February 2nd, 2011, 13:24   #22
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Quote:
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Would 0.528atm be approximately 970fps or 0.87mach?
Not 0.528 atm, just 0.528 P/Po. By definition this is when the flow approaches M=1 at the smallest cross-section.

Quote:
Your the chief in here, but I have to disagree.
Well then, here's a perfect opportunity to prove me wrong and vindicate yourself. Get a before-after of flow AND swirl tested by Alex (or any engine consulting company like Lotus Engineering, Ricardo, AVL, FEV, etc., or any half-decent University engineering department). Ruben might even be able to hook you up...

Quote:
My swirl meter is still un-attached
Then attach it or talk to Alex. Then talk to us.
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Old February 2nd, 2011, 13:37   #23
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BTW, the graph shows flow and swirl/tumble coefficients at full lift. It doesn't make any attempt to explain characteristics at low lift. Of course, larger valves and better port shaping will improve flow and probably not affect charge motion too much at the same time if done correctly. But the trends -- if not the absolute numbers -- as shown in the graph will be undisputable. It's nothing personal It has nothing to do with how good of a porter you are, it's physics.

Flow coefficients are normalised to piston area. Swirl coefficient is also normalised as the ratio of the circumferential velocity component to the axial velocity component of the swirling flow.
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Old February 2nd, 2011, 13:42   #24
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For your edification, you don't have to take my word for it. Here's the bibliography:

Title: Modern engine technology: from A to Z / [edited by] Richard van Basshuysen and Fred Schäfer, editors.
Translation: Lexikon Motorentechnik
Publisher: Warrendale, PA: SAE International, c2007.
Subject (s): Internal combustion engines - Dictionaries
Internal combustion engines - Encyclopedias
Description: xix, 1047 p. : Ill.
Other (s) Author (s) / Title (s): Van Basshuysen, Richard, 1932 -
Schafer, Fred, 1948 -
ISBN: 9780768017052

Title: Internal combustion engine handbook: basics, components, systems, and prospects / edited by Richard van Basshuysen and Fred Schaefer.
Translation: Handbuch Verbrennungsmotor
Publisher: Warrendale, PA: SAE International, 2004.
Subject (s): Internal combustion engines
Description: xxxix, 811 p. : Ill. (Some col.)
Other (s) Author (s) / Title (s): Van Basshuysen, Richard, 1932 -
Schafer, Fred, 1948 -
ISBN: 0768011396
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Old February 2nd, 2011, 13:54   #25
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Originally Posted by TDIMeister View Post
Not 0.528 atm, just 0.528 P/Po. By definition this is when the flow approaches M=1 at the smallest cross-section.


Well then, here's a perfect opportunity to prove me wrong and vindicate yourself. Get a before-after of flow AND swirl tested by Alex (or any engine consulting company like Lotus Engineering, Ricardo, AVL, FEV, etc., or any half-decent University engineering department). Ruben might even be able to hook you up...

Then attach it or talk to Alex. Then talk to us.
How much 0.528PR is from atmospheric?
I calculated that 1Mach should be close to 0.7atm.

Real life results do not justice bragging rights?
No, really, do you think that by incresing flow @ 2000-2500rpm by reducing swirl could yield to reduced smoke?
My believing is that added air helps from the point when engine starts to starve on air.
Increased low lift flow typically reduces power under to at least torque peak of N/A engine.. on forced engines torque peak is more or less "artificial" depending how turbo is sized.

There are several reaons why I did not attach swirl meter.
One was obviously that I am lazy =)
One was the fact that there are different type of swirls, low port runner would make huge swirl, but not that type of swirl you could use with TDi engine.
When I started porting TDI heads I noticed at some point that they did have unique shapes compared to typical heads they liked, so I went after what they wanted from flow and sound vise.. I know you enjoy reading this

If you did not notice Alex has increased flow and swirl on some lifts.
You can fix the seat area / do some bowl porting and flow will go up.
If you do not touch swirl, then flow speed at that point is increased which will increase swirl.. not so hard to figure without engine consulting company =)
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Old February 2nd, 2011, 13:59   #26
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BTW, the graph shows flow and swirl/tumble coefficients at full lift. It doesn't make any attempt to explain characteristics at low lift. Of course, larger valves and better port shaping will improve flow and probably not affect charge motion too much at the same time if done correctly. But the trends -- if not the absolute numbers -- as shown in the graph will be undisputable. It's nothing personal It has nothing to do with how good of a porter you are, it's physics.

Flow coefficients are normalised to piston area. Swirl coefficient is also normalised as the ratio of the circumferential velocity component to the axial velocity component of the swirling flow.
And that is absolutely correct Sir, the straighter the port, more it has opportunities to flow.
I was just refering to you previous statement and the fact that your the respected authority in here so I tried to straighten that a bit as its not that black and white:
Quote:
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There is a clear trade-off between swirl/tumble and flow. The more flow you want, the more the swirl/flow must be compromised. No free lunch.
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Old February 2nd, 2011, 14:08   #27
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Another excellent flow bench thread:
http://speedtalk.com/forum/viewtopic...3c2ac64713b4b8

Schematic of Tippelmann test rig and flow coefficient normalisation equations:
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Old February 2nd, 2011, 14:10   #28
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I was just refering to you previous statement and the fact that your the respected authority in here so I tried to straighten that a bit as its not that black and white:
I see, ok.
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Old February 2nd, 2011, 14:35   #29
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Quote:
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How much 0.528PR is from atmospheric?
I calculated that 1Mach should be close to 0.7atm.
I think you're using Bernoulli's equation for that. Bernoulli only applies for incompressible flows; beyond Ma≈0.3 the flow can no longer be considered incompressible, so you must use the long equation I gave a few posts up for isentropic flows. When you go past Ma>1 and have a normal shockwave, both equations don't work (because the flow is not isentropic across the shockwave, but I digress... )

Quote:
No, really, do you think that by incresing flow @ 2000-2500rpm by reducing swirl could yield to reduced smoke?
My believing is that added air helps from the point when engine starts to starve on air.
Yes you can. It is explained by other factors. You can have less smoke with more airflow but less swirl because you're simply running an effectively higher lambda. There's nothing really wrong with doing that, but there may be circumstances that you want to target lambda/smoke because it's a sign of how efficient the combustion is with the available air (air utilisation rate).

Most people here won't care about that, but say you're racing in an air-restricted rule regime, so you want to get the most performance (most fuel burn) out of a given amount of air you can get into the engine. Or, you want to reduce trapped air mass in the interest of targeting PCP if you're already at the bleeding edge.....

Quote:
Increased low lift flow typically reduces power under to at least torque peak of N/A engine.. on forced engines torque peak is more or less "artificial" depending how turbo is sized.
Agreed.

Quote:
There are several reaons why I did not attach swirl meter.
One was obviously that I am lazy =)
One was the fact that there are different type of swirls, low port runner would make huge swirl, but not that type of swirl you could use with TDi engine.
When I started porting TDI heads I noticed at some point that they did have unique shapes compared to typical heads they liked, so I went after what they wanted from flow and sound vise.. I know you enjoy reading this
I do! And if you find a way to have a great flowing head whilst keeping a healthy amount of the useful form of swirl, then you've hit upon a holy grail of Diesel performance tuning and I want to be in on it.

Quote:
If you did not notice Alex has increased flow and swirl on some lifts.
You can fix the seat area / do some bowl porting and flow will go up.
If you do not touch swirl, then flow speed at that point is increased which will increase swirl.. not so hard to figure without engine consulting company =)
The numbers do show that what you describe is perfectly true, but the normalised numbers (because it's a ratio of the swirl-velocity divided by the axial velocity component of the total mass flow) also will not drastically change, which is my original point.
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Old February 2nd, 2011, 14:44   #30
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Originally Posted by TDIMeister View Post
Another excellent flow bench thread:
http://speedtalk.com/forum/viewtopic...3c2ac64713b4b8

Schematic of Tippelmann test rig and flow coefficient normalisation equations:
That sort of swirl measuring device would be better, especially if honeycomb could be divided to 2 or 3 separate circles measuring force.

Thanks for bringing that thread up.
Nice to compare flow numbers to top of the line flowbench =)
My bench is calibrated to show ~same as flowbench what Ford is using, or actually mine reads 3% more, but as SF and other commercial benches show approximately same I can live with that.

My M20 flow numbers are somewhat higher than what marquis is showing, ~5-10% to 10mm, but then at 12mm I got 1% less.
There could be variance in seat profiles etc causing errors, so maby I should not compare like this.

He calculated flow speeds of 77m/s and I did measure 87m/s.
Usually measured flow speed is higher than calculated and I do not know at what flow/lift point he did calculation.
But if he used stock cam as baseline he probably calculated from 9mm lift where I have ~10-13cfm (7-9%) more flow.. that would match close enough.

How much do you calculate TDI engine would consume air at 4000rpm if boost pressure is excluded?
Or with given flow data from Alex how much depression there might be at same RPM?
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