David Vizard's PowerTec 10 EP 19 Why valve and port Discharge Coefficients are so important
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- Опубликовано: 10 сен 2024
- In this , episode 19, DV explains the importance of understanding what the Discharge Co-efficent is and how it provides a target port flow performance.
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Between you Mr. Vizard and Mr. Holdener I have learned a lot! I have to thank you both!!!
These videos are absolutely stunningly brilliant. I particularly love the venom you display when you tell us about people who perpetuate the BS we often hear about these subjects!
Dave, I've followed your teachings for decades now - since you published the book regarding modifications to the 2.0 liter Ford engine during the/your Pinto era.
Thank you for passing along the knowledge and wisdom!
I can’t help but watch your episodes over and over just to make sure I didn’t miss anything. Thanks DV and Marvin 👍
Great content as always. As a mine Ventilation engineer, looking at how the same airflow principles are applied is very interesting.
@ 21.20 you show a graph that tops out at ~440ft/sec (or 134m/s.) In my experience you rarely see velocities >110m/s. With a 'rule of thumb' to design any flow orifice to have a peak (average) velocity of less than that value. Certainty, it's very rare to see a mine fan with a tip-speed that exceeds this value.) As at this speed, airflow begins to change it's characteristics from 'incompressible flow' to 'compressible flow.' (Obviously for jet engines and turbocharger compressors/turbines this is different as this velocity is exceeded.) But when sizing throttle bodies, carburettor throat's or estimating 'peak-flow' through a known cross-sectional area, it often represents a hard upper bound.
There was an excellent paper written by Blair and Cahoon titled: "Best Bell" which conducts analysis into what the perfect bellmouth shape is. Well worth a read.
But there might be a typo in the title ;)
Richard Holdener is a fantastic engine dude .
I have both your how to port and flow test cylinder heads and how to build horsepower books and I’ve found them to be extremely informative and helpful. However, I would be very interested to see more of the same material such as determining exhaust cam duration, determining intake and exhaust lift and overall cam spec design for 4 valve cylinder heads. And yes, I know that almost everything in the books can apply to almost any internal combustion engine however I feel like it would help a lot to bring this very high quality information to the sport compact field who, for the most part, think that these lessons learned from the V8s don’t apply to them. Please, a series on multi valve cylinder heads would be massive!!!
Thanks so much for making this knowledge available in this way .I was introduced to this back in the 80's as I was building a VW bored out to 88mm and 1 size bigger intake valves and the largest exhaust valve I could fit . Did porting myself with instruction at beginning and left to it . My Baja Bug pulled wheelies in first and second . Loved it !
Thank you for your time and information David.
Subbed to Richard Holdener long ago . Love his 560 ft/lb torque TPI 383 sbc !
I apologize for the premature lecture David. This has been in my scope of work for 40 years. 👍
You have my attention and if I can afford to attend a seminar I certainly will.
David absolutely insightful and fascinating! 20 years ago no one would share this in depth knowledge!
Thank you, thank you, thank you!
The pro racers always tried to keep cylinder head info locked down.
@@cjbert6790 They sure did Bert! Much of David's material is not intuitive, but is the result of test and development. You need deep pockets to learn the levers for success, and if you paid for it, you kept it close in your team as Intellectual Property not to be shared.
Mr Vizard, thank you for yet another excellent video. To the point if I may, respectfully... the music. A question to give context, in your collegiate level classes did you supply a soundtrack to your classroom while giving instruction, does any professor? It simply does not add to your material, therefore it distracts from it. Your presentation otherwise is fantastic and allows me the layman to grasp the concepts and techniques presented. Or, I would gladly pay for a patreon account for edited music free videos. Or take a poll - who of your viewers stops watching if there is no background music? ( probably none?) Again, respectfully thank you for sharing your winning experiences & techniques.
I think I missed the mark again on this sound business but I believe I have found what might be the problem. My computer plays back sound in the editing program quieter than the playback on RUclips. If I cut the background sound more it might meet with you approval. I will try it on the next one.
@@marvingvx1 I think all us, your faithful subscribers/viewers can understand your production adjustments along the way and appreciate your efforts. I've seen others mention it and I don't wish to "pile on" in a mean way. If I may add one more point. We require no ominous/suspenseful music to keep us engaged, your stories & material are more than enough. Simply, this is what people subscribe for - distracting production/poor content (in general) is why people unsubscribe (customer service science - eg book - The Effortless Experience). You already have us, just keep it simple to keep us coming back. Thank you for being open to feedback.
Agreed. Zero music necessary or wanted. Mr. Vizard's words are what's important and any music is distracting from them. Everything you need for an outstanding video is there before you add the music.
I like the music. We're listening to David Vizard. He is a wizard. The music fits.
PLEASE, PLEASE, PLEASE kill the music. Don't turn it down, kill it altogether. As others have said it adds nothing but a distraction. We are trying to grasp at times some very in-depth principles, the video doesn't need distractions to make that harder.
Thanks David. I enjoyed the technical level that you presented this topic. Perfect for some like me who wants to know more but who is far from being a professional.
Love your work David.
Thanks again Sensei Vizard!!
Thank you so much for sharing your knowledge with us. I love reading your books and watching your videos. The only thing I could do without is the music in the background. It's distracting and kind of creepy.
Thank you for showing telling, see ya next time see ya bye bye.
Thank you for the lesson.
Thanks Again for a Great video ,
Dam !!! I will have to see this again. Makes sense now. Good job Sir !!
Thanks David!
Great show keep it up
Be great David to now see a standard port on a SB Ford 383 stroker and then measuring the improvements as porting took place
For me, the audio seems fine on this one and the music is never too loud. I actually started to like the music, but I think you should ask your viewers to post comments on the next video telling you if they like the music or want it gone. By the way, I don't know if you know, but you can go to the RUclips Studio and edit the titles of your videos to correct the typos if you want to.
Thank you for the info
David let them know the water column in the straw tha equals a little over one psi means the psi measured as the result of the water weight in the straw. Approximately 27.7 inches of water column = 1 psi inches of Mercury can be explained similarly. With Mercury weighing much more than water is the difference. Tha Sam goes for other liquids with different specific gravity.
I saw the Chevy engine overhead cam , for indy,, the intake ports were top of the head, like where hemi spark plugs are, I'm thinking those heads should flow like a wind tunnel! 60's tech is often seen as outdated/ obsolete, I'd like to have one of those engines! Maybe a 383version, they did some crazy stuff back in the day! I'm curious what a engine like that would do with a modern make over, or a modern version!!.. They had to be just off from straight on from the valve! I would love to see one of those heads, with crazy ports like that, it has to be interesting!
James, I learned some very interesting things about ports like this. I will cover this in my '5 golden rules' porting series. It will be in the two part vid of rule #1 so when the first comes out bbbuuuuugggggg me to include such.
DV
David, your above software links do not work. Have other links?
Once again superbly explained and mind “broadening”. Thanks.
Could a subject such as oils/lubricants be a separate episode?
Br - Peter Lundorf - Dk - Europe
Mr. Vizard I hope I get this right which I probably wont but here goes anyway. As the valve opens you should have choke flow so the gases are at super sonic. Would this make them more dense so that more gas will flow out of the cylinder, and then as the valve opens more you lose choke flow. This would then decrease the density of the air causing an increase the pressure in the port restricting the air flow somewhat.
The internal combustion engine, is a very complex air pump, it may be considered a simple pump, if you are only looking at the air filter and muffler, get much closer than that, it starts getting complex! Especially if you understand anything that is going on!!
How about a video on piston ring seal?
how do you take air at one atmosphere and zero velocity back up to atmospheric pressure at the valve with high velocity? Bernouilli would have an issue with that. I think the "112%" is just a math error at very low lifts. Blair outlines it in his book.
Thank you mr vizard.could you do a video on runner length not just for rpm tunning for pressure waves thankyou. Peace
Mr. Vizard, could you flow bench test the stock 225 slant six head at all the different lifts and then port it, retest it and then run your cam matching program against it? Then a carb, intake manifold & tune headers & an exhaust to it?
Sweet video! With tons of knowledge! When comparing these to 100% efficiency, did you take valve stem diameter into effect or not? Because if you weren’t then the port is actually more efficient
How exactly do you measure port efficiency? Do measure recorded flow against a theoretical maximum flow to get a percentage of it?
That's exactly the definition of Discharge Coefficient.
@@ashkira2 Ahh OK was losing focus with the background music, must have missed that.
Hi David....i am based in australia..i have an aussie muscle car that is running a nice 306 windsor...its getting tired was thinking of doing a 347 stroker but i am also thinking of doing a 351 windsor .which i have a 1974 block,was going to use a stock 351 eagle forged crank with chev 6.2 rods and pistons...in your opinion which would you choose..dont have an issue with space as my car came out with both blocks.thanks for your time. Steve in OZ
From memory (and it's not very good) I think the 351w block was an 1" taller in the deck.
The Windsor block can interfere with stock suspension on small ford cars. That’s the reason to build a 347.
Steve, So long as it does not interfere with the suspension I would go for the 351 format. However I would also work overtime to fund a stroker crank to make it a 408. If you can do that you won't be disappointed.
DV
It’s amazing how bad a poppet valve can mess up a perfect port.
How come you haven’t done Pontiac motors?
Does the discharge coefficient change as the Boost goes up. I've always wondered if some ports are better suited to boost, versus normally aspirated. So if you had a huge port low velocity inefficient would it become efficient with 3 bars boost or will the inefficient Port still make inadequate power? Thanks great video I love this information
Boost change basicly nothing.
@@V8Lenny why does the engines volumetric efficiency change so dramatically with Boost? Is it more velocity or just oxygen?
@@danielsullivan9865 VE doesnt change , only density changes.
Hi, Have you experimented with an inlet port surface finish like a Golf ball?
Had one like that in my exhaust port (doctor gave me a shot & 3 weeks of antibiotics and cleaned right up tho)!
The golf ball dotted finish will only improve flow attachment if the bend angles already cause flow detachment without it. If the bend angles don't have flow detachment on it and you applied a golf ball dotted finish, it will just reduce efficiency.
Hi Dave
Bmw m62 .an here
Still wo wandering if I could speak too you over the phone some time
Yes,
Go to davidvizardperformanceseminars and leave a phone # and I will get to you.
DV
Ok will do
👍💪
I think david should check the p key on his keyboard
Yes it is imortand he does that.
Why don't you add sound to the port. Vary the frequency and amplitude and see what happens. If you put a microphone in the ports of a running engine what does it sound like. This is still simplistic view of what is occurring.
I always have "ort discharge" after eating bean burritos.
Personally I blame squirrels
That's nuts!
Who chooses the creepy background music?
Trev - I hate owning up to this but I do!!! Sorry.
@@marvingvx1 lol, maybe I will have to enjoy it if it's coming straight from the king of porting.
Is there any chance that you will do a video on swirl port heads like the tbi and direct injection diesels?
David you have a clear idea in your mind what "simple" means and what "complex" means, but unless you know what the person who originally made that statement meant, and in what context they meant it, you can't unequivocally say they were wrong. Let me play the Devil's advocate for a second... Take your average Briggs and Stratton mower engine, which would probably be akin to very early automobile engines, since the saying was around before I was born, and may even date back to the early part of the last century.
If the engine contained a few dozen moving parts one could very easily say that is "simple", if it contained many thousand parts, you could say that is "complex". If you look at and engine from the perspective of how it achieves combustion... suck, squeeze, bang, blow, again you can very easily apply the term "simple" to its operation. I personally don't believe the original author of the saying was talking about the science behind the cyclic operation, but instead was making a very general statement of an internal combustion engine is not that complex at a fundamental level.
I would further back this up by something my father said to me in the mid 70's when I was trying to get my motorbike running. He said all it takes for an engine to run is air, fuel, and spark (compression being a part of air). Again he wasn't trying to trivialize how the internal combustion engine worked, but instead give me some broad strokes guidiance on what to check to get it running. I believe this is what the author of that saying was trying to convey.
What a bunch of nonsense
I presume you are describing yourself here - yes!