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 Old 04-07-2016, 03:26 PM   #401

 
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I fully understand how scavenging works. These are the facts.

Mass flows from high pressure to low pressure.

On a 2871 turbo (not a hybrid), the exhaust pressure is higher than boost before turbo is fully spooled.

Torque and airflow is improved by full VVT advance in the same regions of operation where exhaust pressure is greater than boost pressure.

From these things we can surmise that if both valves were open enough at the same time for significant mass transfer to occur it would be exhaust gasses flowing from the manifold, back through the cylinder, into the intake manifold like an EGR system, limiting the fresh air that can be ingested and reducing torque, which is the opposite of what we observe
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 Old 04-07-2016, 04:12 PM   #402
 
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I agree with you that gases should flow back to the intake manifold. But actually that small lift acts like a siphon or Ventouri or ejector how you like to call it. ( like a compressed air paint gun which is drawing the paint through a straw like tube)Exhaust gases tend to be pulled from the cylinder creating a mini-vacuum which will let the air to flow in the cylinder. I think you know how an ejector works. Of course, with higher valve lift you will have reversion because there will be no more ejector like
Hope you got the idea with my bad english.

EDIT: There is also the inertia of the moving exhaust mass which plays also the role
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 Old 04-07-2016, 04:35 PM   #403

 
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The venturi effect is completely unrelated. The equation for flow through a valve is the same as through any other orifice and is driven by the pressure differential across it.

The venturi effect creates a low pressure zone in the orifice but does not increase or decrease mass transfer. It is a product of the velocity/mass transfer of the gas through the orifice. If the venturi effect drove mass transfer we could use it to make perputal motion machines, as once the flow started through the orifice it would feedback on itself. This obviously does not occur.

Now you can claim that the inertia of the exhaust keeps it from back flowing briefly, but then its really not scavenging is it, and again would only work at one very specific RPM. The inertia of the gasses would remain the same, at too slow RPM the gasses would fully reverse and backflow, at too high the valve would close before the inertia slowed the flow. Either way the exhaust isnt being pushed out of the cylinder by the intake charge so it's not scavenging.

The reality is you can't scavenge a turbo motor without a giant turbo with a big hotside that is really only happy at peak power. We have cams that fit our high back pressure reality.
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 Old 04-07-2016, 04:54 PM   #404
 
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@Ziggo
Scavenge not means that the gases are pushed by the frwsh air. It can be caused by the exhaust being pulled due to the inertia of moving mass. Both situations are called scavenge. I would not translate now the "IC theory and calculation book" which I studied, from Romanian to English, but I cand assure you that either way is called scavenge. You think to a much larger scale thinking that I stated that we see huge flow through that small openings. The flow and gas inertia will suffice to empty the cylinder for the most EGR and improve the combustion quality; that combined with the increase of dynamic CR equals win. And as more hot gases pass through that small opening the turbo spool will be improved;that's because the turbo is spining due to heat and the mass of the exhaust gases.
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 Old 04-07-2016, 05:42 PM   #405
 
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Originally Posted by Ziggo View Post
The reality is you can't scavenge a turbo motor without a giant turbo with a big hotside that is really only happy at peak power. We have cams that fit our high back pressure reality.

I would argue that if you think of the turbo from a conservation of energy perspective, the exhaust side will always have more pressure than the intake side. The turbo is only taking a percentage of the pressure energy from the exhaust side and putting it into the intake side; it can never reclaim more than 100%.
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 Old 04-07-2016, 05:43 PM   #406

 
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@Mazdazilla6; your flow bench numbers might come into play here. You're seeing decent flow at .066" lift aren't you?

Disclaimer: I'm very confused how the overlap (which I think is now being agreed upon) is creating faster spool. I have many experiences with engine design, but the specifics of turbo spool I know next to nothing about. However, I'm thoroughly interested in what asshat and ziggo come up with. Carry on, gentlemen. I shall observe and eat popcorn.

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 Old 04-07-2016, 05:53 PM   #407
 
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If you would watch the video attached 4-5 posts bellow you would understand how it works.
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 Old 04-07-2016, 06:27 PM   #408
 
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The video you posted... Is that not exactly whats happening when we are using VVT at low rpm?
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 Old 04-07-2016, 06:30 PM   #409

 
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That video is also not our motor. Central fuel injector is a dead giveaway.
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 Old 04-07-2016, 06:41 PM   #410
 
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@Ziggo
The placement of the injector have nothing to do with the valve timing.
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 Old 04-07-2016, 06:45 PM   #411

 
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Originally Posted by silvapain View Post
I would argue that if you think of the turbo from a conservation of energy perspective, the exhaust side will always have more pressure than the intake side. The turbo is only taking a percentage of the pressure energy from the exhaust side and putting it into the intake side; it can never reclaim more than 100%.
That would be true if there were no energy added to the system, however there is combustion between the compression and expansion so there is plenty of energy available to turn the turbine.

The primary driver of backpressure is the the turbine housing. You can generate a positive ratio even with a small turbine if you have a housing with a big A/R, but this kill dynamic response.

Originally Posted by calinflorinalexandru View Post
@Ziggo
Scavenge not means that the gases are pushed by the frwsh air. It can be caused by the exhaust being pulled due to the inertia of moving mass. Both situations are called scavenge.
Whatever you want to call it, but this occurs regardless of the intake cam timing, and as I indicated, only works at a narrow RPM range.
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 Old 04-07-2016, 07:04 PM   #412
 
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@Ziggo
How limited is the RPM where it works is not my point. What I wanted to prove on all this long thread was explained earlier and understood by somebody. Regarding the backpressure you saw when you made it I can consider it an isolate case. A lot of variables can affect the backpressure (Turbine A/R, wastegate opening, turbo-back exhaust)

If you don't mind and if you have desire to discover more you can read the following article. It is written in colaboration with CompCams not by an amateur.

Turbo Camshaft Guide - How to Select the Right Cam for Your Turbocharged Engine - Car Craft Magazine

P.S.: Is a 10 minutes read but is worth it and explains a lot of misconceptions regarding cams and calculations
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 Old 04-07-2016, 07:10 PM   #413
 
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Originally Posted by Ziggo View Post
That video is also not our motor. Central fuel injector is a dead giveaway.
And you don't want to understand that it doesn't matter is our motor or not . The running principle is the same for all engines. We have a 4-stroke turbocharged gasoline direct injected engine. Doesn't matter you call it DISI, TSI,TFSI,TCI ,GDI.
And for the god sake when I'll be back home I will make a video with the engine timed with an endoscope camera to see that the valves are opened in the same time. I will block the old vvt to 30 degrees. Until then keep your idea.

EDIT:I forgot that is turbocharged
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 Old 04-07-2016, 07:21 PM   #414

 
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Other engines that do scavenge as in your video can have drastically different turbo setups that allow them to operate as described.

Consider it an isolated case then since you are so determined to ignore it.

This specific vehicle, which has the measured back pressure, shows increased performance with the VVT advanced 35° such that if overlap was resulting in significant massflow, would be causing reversion.

My turbo setup is hardly uncommon, I've tuned other BNR S3 turbo that show the same benefit to the advance.

I wouldn't advise thinking my back pressure is an isolated case. The ATP turbos all have similar hotsides, and the K04 is even more restrictive.
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 Old 04-07-2016, 07:29 PM   #415
 
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@Ziggo
The video was posted with the purpose of demonstrating how overlap and scavenge can improve the turbo spool. It was an addition to all other docs which could be much easier understood that graphs and numbers.
You still not read the article which I posted. Just count pkease how many "overlap" and "scavenge" words there are.
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 Old 04-07-2016, 07:50 PM   #416
 
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Originally Posted by Ziggo View Post
This specific vehicle, which has the measured back pressure, shows increased performance with the VVT advanced 35° such that if overlap was resulting in significant massflow, would be causing reversion.
Which words in the next phrase you did not understood?
" The overlap is significant enough to draw out most of the remaining EGRs due to scavenging effect"
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 Old 04-07-2016, 07:51 PM   #417

 
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I'm unconcerned with the article. I know exactly how scavenging with overlap is supposed to work, which is how I know that isn't in this case. The cams are not designed for it, and the observed performance doesn't support it occurring.
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 Old 04-07-2016, 07:55 PM   #418
 
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Originally Posted by Ziggo View Post
I'm unconcerned with the article. I know exactly how scavenging with overlap is supposed to work, which is how I know that isn't in this case. The cams are not designed for it, and the observed performance doesn't support it occurring.
Why should I squeeze my brains with you if you are so ignorant to all the data and articles I brought in this thread. You can talk to the hand and with your buddies which consider very funny your ignorance even though they do not have any idea what about are we talking about here.

P.S. : earlier you stated that is not possible together overlap+scavenge+high back pressure. If you'd have read the article you would see that is very possible

EDIT: In the same article the cam profile posted is starting the meaurements from 0.000" and is much clear how the overlap is counted. Adding this because you don't have the desire to read it so i do it for yourself
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 Old 04-07-2016, 08:19 PM   #419
 
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Originally Posted by xfeejayx View Post
@Mazdazilla6; your flow bench numbers might come into play here. You're seeing decent flow at .066" lift aren't you?

Disclaimer: I'm very confused how the overlap (which I think is now being agreed upon) is creating faster spool. I have many experiences with engine design, but the specifics of turbo spool I know next to nothing about. However, I'm thoroughly interested in what asshat and ziggo come up with. Carry on, gentlemen. I shall observe and eat popcorn.

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I lost track of this thread because of all the shit slinging.

Anyway, yes the head flows ~50CFM/cyl @.066". Overlap will NOT spool a turbo faster, the LARGE majority of what spools a turbo is thermal expansion of the exhaust gas across the wheel. The rest of what spools it is the flow of the gas itself. 6th grade physics tells me that hot exhaust gas will expand more than cooler charge air.

Time to go back and read I suppose.
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 Old 04-07-2016, 08:26 PM   #420
 
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@Ziggo

"The inertia of the gasses would remain the same, at too slow RPM the gasses would fully reverse and backflow, at too high the valve would close before the inertia slowed the flow."

Yes you are right. Even in the manual attached is stated that there is 0* advance during starting, idle and low RPM's. But whom read the stupid manual?
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 Old 04-07-2016, 08:53 PM   #421
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Originally Posted by calinflorinalexandru View Post
Why should I squeeze my brains with you if you are so ignorant to all the data and articles I brought in this thread. You can talk to the hand and with your buddies which consider very funny your ignorance even though they do not have any idea what about are we talking about here.
Ok, pay attention and read this slowly because I'm only gonna post it once.

This argument is going well. What I mean by "well" is that useless rants like that ^^ aren't very prevalent in this thread. Which is unlike 99.9% of this forum.

Keep your personal opinions and below the belt shots of our other members to yourself. There's a reason these guys have their names in Gold. We don't just hand out Gearhead statuses for participation.

As far as arguments go, this ones pretty clean so far. Keep it that way.

Now carry on.



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 Old 04-07-2016, 09:01 PM   #422
 
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Originally Posted by Ziggo View Post
Whatever you want to call it, but this occurs regardless of the intake cam timing, and as I indicated, only works at a narrow RPM range.
So how does VVT advance actually increase spool? If we 0 out the table the turbo spools like shit.

How is VVT affecting the spool of the turbo when we advance it if not using this "scavenge method"?
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 Old 04-07-2016, 09:19 PM   #423
 
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Originally Posted by calinflorinalexandru View Post
You can find attached a doc where was calculated the flow through the intake and exhaust valves from 0 to max lift with a SuperFlow. This for the Diesel engine but should be no problem comapring to DISI because there is no difference between them regarding intake and exhaust strokes
I'm calling bullshit on this. Being someone who has actually put OUR head on a Superflow SF600 flow bench and flowed it. Saying that our head is no different from a diesel head is wrong in many ways. The flow itself through the port is dictated largely by three things, the port size, the port shape and the intake valve size (and a couple other things such as valve angle and port centerlines etc) and I can just about assure you that our DISI head is not at all like that diesel head. It's WORLDS different from the next closest thing, which is the NA version of the engine. So examining how that head flowed does us no good.

Originally Posted by calinflorinalexandru View Post
The amount of airflow is enough to change the processes in the engine. How significant it is can be calculated with proper tools. For this argument there is attached video for Bosch GDI which explains how does that small overlap improving the turbo spool.
As I stated before overlap will not spool a turbo faster. Because even if there is scavenging going on like you say there is, that air charge going through the exhaust valves is wasted air charge. If that air charge were to be heated (combustion) and allowed to expand in the exhaust it would help spool the turbo A TON more than just some air charge being pushed through the exhaust. The reason why we can get better spool by advancing the VVT is because it allows for the greatest air charge to enter the cylinder and be combusted, thus meaning there will be more exhaust gases available to expand in the exhaust ports and spool the turbo.

I'm seriously questioning what kind of knowledge you actually have versus what you're reading in documents and just posting here. I myself don't even have much credibility but I've personally talked with plenty of people who are, some of them being professors who I talk with on a daily basis who are EXTREMELY intelligent guys. I will take the word of someone who has years of experience in the field over someone who wrote an article and posted it online. Lastly, just because Mazda releases certain documents does not mean it is the be all end all on our engine. After all, the guys who make those official Mazda documents are human just like you and me and they are not all knowing. It's very easy to have unknown error in a test and not know it and then publish it in a document. So just because something is "official" don't take it with absolute certainty.

Originally Posted by sh4d0w View Post
So how does VVT advance actually increase spool? If we 0 out the table the turbo spools like shit.

How is VVT affecting the spool of the turbo when we advance it if not using this "scavenge method"?
Answered above
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 Old 04-07-2016, 09:29 PM   #424
 
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Well I guess it's about time I chimed in again.

I took the time to do spreadsheets (Yay! But not really...) in order to get a better idea of what's actually going on vs what my dyno software shows. My dyno software, by the way, was able to accurately predict both trap and ET on my uncle and dad's racecar to less than a tenth and got the MPH within a MPH, so I'm pretty trusting on the numbers it spits out.


I'd like to preface this post with some other information:

1. I called up Web Cams to see what the fuck their "ramp rate" numbers were, but apparently it's an internal number that's probably arbitrary to the grind. I did, however, discover, that they only post numbers from .010" up because, and I quote: "It's difficult to get a good read below that." Bearing in mind, .010" is one quarter of a millimeter, so that's kind of understandable.

2. Web Cams measures bump sticks on the stick itself; this does not include any form of compensation for clearances, so I factored that in.

3. I used linear interpolation between listed values. It's not perfect, but it's "good enough" to show what we need to know.

4. I also factored in some other shit which may or may not be useful; that will follow later on in this post.

5. I have a bit of confusion regarding the VVT advance numbers from Tomas, so I'm going to ask for clarification here: @Tomas;: your VVT numbers are set for 35 degrees, but written down as half that at the crank. Is that supposed to be the case? I'd figure 35 degrees of cam advance (at the crank) would yield the same in valve event changes.

6. I did my best to combine both Tomas and Web Cams numbers, but I'm sure there's some variance due to clearances / wear and tear.

7. All my math is available upon request.

8. I'm heavily sleep deprived and in horrible pain (and have been for the past month), so my cognitive functions are lacking. Please let me know (no, not you gypsy) if I got something wrong or need to add something else. Before anyone asks: I either have a bulging or herniated disk that is squeezing off the nerves to my left arm; I'm scheduling a Dr. appointment tomorrow since the chiropractor was making shit worse (after $300 in copays no less). Anywho, on to the meat:



These are the numbers I started with:


I looked up clearances (found in another thread here from ~2013 IIRC) and went with the tightest values, except for the intake side which I added .002" to because lazy and because math. It pretty much negates all un-mapped cam timing data below .01", so that's handy.


Then I normalized them to make it easier to see where in the cycle the valve events were happening (one cycle = 720 crankshaft degrees; aka two rotations):



I then used the above data to convert the entire cam profile over using the same math; to do this, I went off of Tomas' measurements for lobe center, then applied Web's numbers for duration:


I did it like this because Web didn't provide that info and even if Tomas' numbers are off because of clearances, the lobe center shouldn't be affected by that anyways.


And here's what that looks like graphed out (sorry in advance for the odd orientation; Google Docs has its own set of usability limitations, after all):


By the way, the peaks are clipped because I couldn't figure out how to do a double vertical axis, not that it matters much in this instance.


Just for kicks, I did a linear conversion to see how the profile curves were; duration column is a measure of how many crankshaft degrees it takes to see a .001 lift, and is linear. Note that lower numbers are more "aggressive" as the time to movement ratio is lower:


Apparently, our ramp rates are pretty aggressive.


It turns out that the just for kicks info was helpful though, since I used part of it to compute a closeup of TDC between valving events to a much more precise (and I use that word loosely here for obvious reasons) degree. Here's what the data looks like (it needs some scrubbing as the last two columns aren't really used):



And she's ready for her closeup:



Bonus round: I calculated piston position using some online calculator (cause my brain is too fried to do the formulae properly apparently) so we have a piston position map from 340 to 380 degrees of crank rotation (0 on bottom axis = 0, 360, and 720 degrees in the other charts):




So what does this tell me?

1. Yes, there's some overlap even without VVT factored in.

2. The vast majority of it happens with both sets of valves open at or below .01" of lift (which is 0.254 mm, by the way); this suggests that flow would be akin to trying to take a constipated shit through 40 feet of garden hose; you may get somewhere with it but it's not going to be worth it. Also, peak lift at maximum overlap is only .013", for whatever that's worth.

3. Even with 30 degrees of advance (if the curve should even be moved 30 degrees on the graph), *all* the overlap happens below .04" (.038" or not even a full millimeter, to be exact) of lift, so flow will still be garbage. If movement is actually limited to half, then that means peak overlap is at .023" of lift for both. Terrible.

4. The piston movement is going to fuck everything up flow wise regarding "scavenging" as it appears to only dwell at TDC for a whopping 3 degrees of crank rotation; the movement is slight, but I think still relevant; no less relevant than "flow" at 1mm or less valve lift.

Side note: Maybe someone who owns a flow bench ( @Tokay444; ) can chime in with some .01" to .05" flow numbers on a stock head, both intake and exhaust...?

5. Turbos run off of the expansion of exhaust gasses, of which there is nearly always more volume of exhaust than fuel air mix (especially in our platform where the air is cooled by fuel to a very high degree inside the cylinder); high manifold pressures are a given, and the only way to get around that would be to run some seriously road illegal setups like top mounted equal length/tuned manifolds with huge AR (5000+ RPM spool) turbos and 5" hood dumps, not to mention the exhaust side headwork that would be required. Any car with a street worthy exhaust setup probably won't fit that bill.
Attached Images
File Type: png Converting and Positioning.PNG (8.4 KB, 387 views)
File Type: png Core Numbers.PNG (10.0 KB, 211 views)
File Type: png Layout.PNG (13.1 KB, 390 views)
File Type: png Overlap Interpolation.PNG (49.4 KB, 211 views)
File Type: png Overlap Closeup.PNG (64.3 KB, 990 views)
File Type: png Piston Position.PNG (31.2 KB, 211 views)
File Type: png Ramping.PNG (6.3 KB, 384 views)
File Type: png Stock Profile.PNG (37.9 KB, 206 views)
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 Old 04-07-2016, 09:41 PM   #425
 
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Originally Posted by sh4d0w View Post
So how does VVT advance actually increase spool? If we 0 out the table the turbo spools like shit.

How is VVT affecting the spool of the turbo when we advance it if not using this "scavenge method"?
From earlier in this very thread:

Originally Posted by Enki View Post
My apologies gents, I should have clarified. In the context of cruise/low load/low RPM, (below 4500) VVT increases airflow. Ziggo is right; even things like ignition timing affect airflow through the engine as exhaust gas temps inside the cylinder when the exhaust valve closes can affect the airflow into the motor when the intake valve opens.

The reason why VVT doesn't give us any additional airflow at higher RPMs has to do with cam timing and head flow and piston speeds; have a look at the cam diagram below:



For the sake of keeping this simple, I'm going to make some sweeping generalizations.

OK so pistons speeds are usually greatest right around halfway down the cylinder, where they start to slow; for the intake stroke in this case, that will be at about 450 degrees as marked. This matters, because this point is where the piston will "draw" the hardest on the head to allow air into the cylinder. Fast piston speeds means less time for air to enter, as you would expect; but there's a bit more to this than just that. When you create even a partial vacuum inside the cylinder (as happens when the piston moves down), you're causing a fluid (not liquid, don't make that mistake) to flow (in this case, air). When something with mass moves, Newton's first law (an object in motion tends to stay in motion) comes into play; basically, because air is flowing into the cylinder, it will continue to try to flow into the cylinder until some energy or force causes it to stop flowing. In this case (low RPMs), the piston going up the cylinder is to blame, and some air will be forced back out of the cylinder via the intake valves.

At higher RPMs, it doesn't really hurt airflow to have the valves open after the piston has already started down the cylinder since there's less time for the cylinder to fill, and we can still continue to draw air (via Newton's first law) into the cylinder even though the piston is moving up to counteract it.

Anyway, you can see that the intake valve is closing well after the piston would be heading back up the cylinder; this reduces the volumetric efficiency or the power capability of the engine at lower speeds (but may not hurt at higher speeds). Advancing the camshaft forward 30 crankshaft degrees almost completely negates this intake reversion, and allows for more air to enter the engine via better timing of valve events; in fact, you can see that with 30 degrees VVT, the intake valve will be at peak lift right around peak draw (450 degrees rotation), rather than after it.

Having maximum valve lift at this point, along with reducing the time that the intake valve is open while the piston climbs the cylinder is what causes the increase in airflow.

So why doesn't VVT help airflow at higher RPMs? Time. By the time 450 degrees rolls around, even if the intake valve is open all the way, chances are the air in the intake manifold is still trying to accelerate into the cylinder; by the time it would have reached the same speed as it did at lower RPMs, the intake valve is already closing.

I think the easiest way to visualize the effect cam timing has on airflow is to think of it like this:

You have a weight on the table in front of you, with a rubber band around the outside of this weight. Also inside the rubber band is your finger, which you use (in place of the piston) to move the weight around the table with, however, you can only move your finger so far before you have to stop and wait for the weight stop moving before you can move your finger again. You'll notice that a faster movement of your finger (like the piston at higher RPM) will induce more stretch in the rubber band before the weight even begins to move, while at slower speeds, the weight is more likely to move with minimal stretch.

Thus, the energy of drawing upon the intake manifold takes time to cascade through the entire system and ultimately winds up ending the draw outside the air filter.

Make sense?

Questions?

Did I miss something?
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 Old 04-07-2016, 09:42 PM   #426
 
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@Enki; Thanks for the illustrations. Two things. One, max pressure delta is at the lowest lift, so don't make the mistake that there's insignificant air flowing through the orifice. Two, if we actually are seeing overlap (which I see as not desirable) then we might actually see some benefits by clocking the VVT back a couple of degrees while timing the engine so max advance left us with no overlap and indicated 0* would in reality be a couple of degrees negative. Just food for thought.
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 Old 04-07-2016, 10:04 PM   #427
 
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Originally Posted by Mazdazilla6 View Post
One, max pressure delta is at the lowest lift, so don't make the mistake that there's insignificant air flowing through the orifice.
That would require a pressure delta that's in favor of the intake side though; I'm reasonably certain that's going to be rare except maybe for specific configurations or RPM bands and not the general rule.

My 6758 (with .65 hotside) only gained 3-4 PSI boost with a 5 PSI jump in spring past a certain RPM; the manifold is gasket matched and tuned runner, and my turboback was a minimum of 2.85" (the same as the other EFR setups making well over 400 WHP. That same turbo now has a .85 hotside on it and didn't lose any spool, which tells me something about both the EFR series *and* our engines.


Originally Posted by Mazdazilla6 View Post
Two, if we actually are seeing overlap (which I see as not desirable) then we might actually see some benefits by clocking the VVT back a couple of degrees while timing the engine so max advance left us with no overlap and indicated 0* would in reality be a couple of degrees negative. Just food for thought.
That's an interesting idea; it would probably benefit those with stock cams and big turbos the most, especially if they are spinning higher than about 6500 ish.



I'd like to add that if I were to run stock cams on my destroke build, I'd probably be able to get away with holding max VVT longer (and have it be effective) due to the change in piston speeds that I'll be seeing. More food for thought.
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 Old 04-08-2016, 03:33 AM   #428
 
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@Enki @Mazdazilla6 @09speed3z @ziggo and many others

First of all I want to appologize by creating headaches and sleepless nights for you guys. I wanna thank you by this way for all of your work done on this awesome forum for the mazdaspeed community

The whole debate started from my statement which was argued with information released Oficially by Mazda that there is overlap with our cams.
I did not state that the overlap is the solely contributor to the Turbo Spool.
I did not say that there is soo much flow that we can actually spool the turbo by it. The only statement I've made was that the flow is significant enough to draw part of EGR's from the combustion chamber , improving the combustion quality which added to the higher DCR means better spool.
I fully understand that is not desirable to pull fresh air to the exhaust.
All my statements are available for Big Turboes, under that 0.05" of lift .
Regarding the VVT advance I still sustain my statements that there is only 30* maximum advance as is specified in the Official datanot 35* ; this unless somebody proves that is wrong; once I'll put my hands on the old VVT actuator dismantle it and measure te opening angle.

Regarding my attitude against the MSFGEARHEADS :
- as long as their attitude against me was shitty I consider it being provoqued to answer in the same way. By my attitude I did not want to disconsider their knowledge or the work for this community

Mybe I've missed some more aspects which I would like to clarify but the story ends here for the moment until I'll be back home and I'll upload the promised videos
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 Old 04-08-2016, 06:30 AM   #429

 
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There is sensor feedback on the intake cam so we can log both commanded advance and actual advance. We are not commanding 35 and seeing 30 in the response. Not sure what cause you would have to distrust the sensor feedback.
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 Old 04-08-2016, 01:44 PM   #430
 
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Originally Posted by Ziggo View Post
There is sensor feedback on the intake cam so we can log both commanded advance and actual advance. We are not commanding 35 and seeing 30 in the response. Not sure what cause you would have to distrust the sensor feedback.
The following measurements made on the Mazda 6 MPS VVt actuator makes me think like that. Even the photo was not taken parallel with the actuator there cannot be a lot of discrepancy.

EDIT: If we would command 40* in the tables what will be the feedback? A MIL perhaps ? Or a few bent valves?
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 Old 04-08-2016, 02:27 PM   #431
 
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@Mazdazilla6

Quote: "I'm calling bullshit on this. Being someone who has actually put OUR head on a Superflow SF600 flow bench and flowed it. Saying that our head is no different from a diesel head is wrong in many ways. The flow itself through the port is dictated largely by three things, the port size, the port shape and the intake valve size (and a couple other things such as valve angle and port centerlines etc) and I can just about assure you that our DISI head is not at all like that diesel head. It's WORLDS different from the next closest thing, which is the NA version of the engine. So examining how that head flowed does us no good."

That article I posted not to compare our heads with a diesel head. It was posted because someone here was 100% sure that under 0.05" of lift there cannot be any flow because the openings are too small . As I could not find the data from our heads I chosed other methods just to make the people open their eyes and not to remain stuck with one idea or concept Same applies to other articles and docs posted by me which don't make refference to our DISI.
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 Old 04-08-2016, 09:41 PM   #432

 
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Originally Posted by calinflorinalexandru View Post
The following measurements made on the Mazda 6 MPS VVt actuator makes me think like that. Even the photo was not taken parallel with the actuator there cannot be a lot of discrepancy.

EDIT: If we would command 40* in the tables what will be the feedback? A MIL perhaps ? Or a few bent valves?
IIRC the most we can get out of it is like 37° even when commanding more advance, which lines up pretty well with the picture. The commanded value is in crank degrees, and I would bet that with the fat lobes jammed up against their stops you would see the skinny ones with 18.5° of space in front of them.
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 Old 04-09-2016, 03:33 AM   #433
 
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The maximum travel is determined by the small chamber. If you move a little bit until the big chamber lobs are reaching the stopper, one side of the small chamber lobe will increase and the other will decrese (total angle is remaining the same). Just sum up the angles in the small lobes. Cannot explain better. I will remake the photo and I will specify which is the maximum travel.
E.g. : 16.37* + 14.62*= 30.98*. On the other side there is around 29.46*. That is maximum travel. You cannot go past that. There will be all the time clearance in the big chamber side
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 Old 04-09-2016, 06:40 AM   #434

 
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Think about that a little more please. If you rotate the inner part counter clockwise relative to its housing the large lobes will contact the housing before the small ones, thus you can't just sum up the space on either side of the lobe to get the total travel. Also remember that these measurements are in cam angle, which is half that of crank angle.
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 Old 04-09-2016, 08:05 AM   #435
 
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@Ziggo
I agree with you 100%. But the picture is misleading. I have to put my hands on the old vvt and using a protractor I can see exactly whats happening. I agree that the travel of the VVT is half than crankshaft angle. For the moment a much higher resolution and clear photo taken parallel with the actuator will be very useful
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 Old 04-15-2016, 07:48 AM   #436
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Simple cam tuning rules for BOOSTED engines:

* Advance intake and exhaust => more low-RPM power, less high-RPM power
* Retard intake and exhaust => more high-RPM power, less low-RPM power
* Less overlap => lower EGTs, faster turbo spool, less fuel
* More overlap => higher EGTs, slower turbo spool, more fuel

Boosted engines don’t like overlap. The incoming cold air and fuel cools down the outgoing exhaust charge, condensing the exhaust gasses. This is VERY counter-productive in a turbo application since the engine needs no help from scavenging to fill the cylinder. I've heard this being called "turbo chill".

Cool, condensed gasses in the same space push less hard on the turbo, causing lag. HOT gasses are better at spooling the turbo, thus the advanced exhaust timing to open the valve sooner in the power stroke. This steals some of those hot, expanding exhaust gasses to help spin the turbo a little faster. When the piston is near the bottom of the bore, hardly any energy is going into rotating the crank anyway, so stealing expanding gasses won’t hurt anything. The retarded intake just helps cut down the overlap further.

Retarding overall cam timing: Retarding overall cam timing is better for high-RPM power. This is because the valves are closing later. The intake valve is closing AFTER the piston has started to travel back up the bore for the start of compression stroke. This is terrible at low RPM because the intake air velocity is low, and air that was once in the cylinder is now being pushed back into the intake manifold and causing turbulence.

At high-RPM, the rules change. Air has weight, and thanks to Sir Issac Newton, we know that once it is moving, it doesn’t want to stop moving. This means that the air can continue to flow into and fill the cylinder, EVEN AFTER the piston has begun to travel UP the cylinder bore. This can allow an engine to exceed 100% volumetric efficiency, if even by a small amount.

Advancing overall cam timing: Advancing overall cam timing is better for low-RPM power. This is because the valves are closing a little sooner. The intake valve is closing AT or NEAR when the piston is at the bottom of the bore for the start of the compression stroke. This is great at low RPM because the intake air velocity is low and easily affected by changes in the direction of piston movement in the engine. Almost as soon as the piston gets to the bottom of the bore on the intake stroke, the valve gets slammed shut so no air can escape as the piston begins to travel back up the cylinder on the compression cycle.

At high-RPM, this may become a restriction since the air has inertia and responds a little slower to pressure changes, potentially choking the air flow to the engine a little.

Conclusion: This information is aimed at allowing tuners to understand what happens when cam timing is altered. When a larger duration camshaft is being installed, unless the lobe centerlines have been changed, the overlap will be increased. If installing larger camshafts in a turbo application, advancing the exhaust and retarding the intake will reduce the inherent increase in overlap caused by upgrading to a larger profile. Most cam grinders, especially regrinders, put the new profile in the same position as the old profile because it is easier, or the only way possible. This has to be changed when the cams are installed in an engine to attain the desired result.

A forced-induction engine should idle smooth when properly tuned, and a naturally aspirated engine should be “lumpy” and have a lope if it is tuned aggressively towards the high-RPM range. If a forced induction engine is loping at idle, fuel is being wasted, turbo spool time is being increased, and power is being lost.
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 Old 04-15-2016, 08:18 AM   #437
 
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Oh, right, this thread. Thanks for the post, Justin, some of that looks familiar.
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 Old 04-15-2016, 11:47 AM   #438
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May be it should be deleted.
It has endured enough misery.
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 Old 04-16-2016, 07:06 AM   #439

 
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cause its copy-pasta Cam Gear Tuning - Tuning Advance, Retard, and Overlap for Power
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 Old 04-16-2016, 07:24 AM   #440
 
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Ugh. That's not what I meant, but yeah.
Toilet thread is toilet.
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