Shownomercy

iTrader: (1)

t000ning is not something I will pretend to understand. But a calculated VE is different than say a standard physical VE, a 2 liter stroke can only draw in 2 liter of air. But change air temp and density, and you can "change" the VE.

hrcslam

Yeah, I get that. But, 100% VE is assumed to be with ambient conditions. As in 1 bar of engine displacement every 2 RPM. If you move more than that, it's more than 100% VE. My engine is over 105% VE NA. Since 100% VE is mechanically (physically??) limited to the volume of the engine at 1 bar, it can only be exceeded by increasing air pressure. I understand what you're saying, but with that NA engines wouldn't be able to achieve over 100% VE and some do.

I understand what you are saying though. If someone builds an engine that maxes VE at say 95%, that is how efficient it is going to be under boost at actually moving the air through. So if I were to add 1 bar of boost through that engine I wouldn't get 200% VE, I'd get -at best- 190% VE. Although the VE tables might not show this exactly, it's effects are certainly present.

Of course in order to exceed 100% VE NA you need a certain type of valve timing event and plumbing. Both of which are detrimental to Turbos...

Shownomercy

iTrader: (1)

Ya, basically if you double atmosphere, you can at most expect to double NA power. Assuming a lot, but you get the gist.

Side note, what RPM are you see above 100% VE? And what flow rate is that? (IDK what unit MAF reports)

hrcslam

I'm SD tuned right now. 107%VE at peak torque. 104% VE at peak HP.

Blackbirdws6

iTrader: (7)

I knew it was worth saving the factory ram air box off my car!!!

Blackbirdws6

iTrader: (7)

When I referred to ram air effect, it was speaking to the intake designs intended to provide positive pressure to the intake manifold. Runner length and size are all aspects of tuning output across the rpm range. In the end an NA engine is sucking in air (vacuum). Suck, squeeze, bang, blow.....

SS RRR

iTrader: (2)

The Richard likes it when you talk dirty.

Blackbirdws6

iTrader: (7)

Awww

SS RRR

iTrader: (2)

sweetbmxrider

iTrader: (13)

You said there is no difference between heads/cam air and turbo air. There is, the temp. Do you not agree?

ACE1252

With boost, on a "stock" engine application, the fueling changes because the atmospheric pressure changes. If adding only boost, VE does not change....so if your MAP can't handle the increase in pressure, it would need to be changed. So, it's a function of the MAP reading...that's how the extra fueling happens. But seems like I do remember seeing some boosted regions of a VE table....been a while since I've done my homework on this, so I would need to brush up.

Equations from one of Greg Banish's books...referencing speed density.

Airmass(g/cyl) = ((VolEngine(L)*VE*P(kpa)) / (0.28705)*T(Kelvin)*(# of cylinders)))

Fuel mass(g/cyl) = Airmass(g/cyl) / (Air/fuel Ratio)

His advanced tuning DVD deals with him adding dual turbos to his stock vette, then going through a scaling operation as he hits the limit of the MAF reading in the PCM's OS with the turbos. I'll give it a quick watch and try and correct any of my goofups.

hrcslam

I understand all this. My question was whether the VE tables exceed 100% with boost over 1 bar on he actual tables or not. It was more understanding the VE tables over 1 bar than anything. Theoretically, 2bar should read 200% VE, but usually it's significantly lower; like 130-150 VE at 200+kpa.

ACE1252

I think it does...but I'm not sure. I need to review the material more.

Usually, the VE table only goes to around 100kpa, so it would have to be expanded or scaled for boost....which was some of what I was missing(ie forgot...). The values would stay the same for 100kpa and under, but data would need to be added for up above 100kpa.

hrcslam

Yeah, I know for the stock LT1 pcm it's limited to 100kpa and 100% VE. So the VE tables would have to be manipulated by changing the constants and scaling the VE tables accordingly. So 50% VE is 100% by doubling the cylinder volume. And kpa is 50% by installing a 2 bar MAP, but I don't know what constant (if any) to change that, if that is how it's done.

ACE1252

After reviewing the video, his own Vette was a 2009. That OS was updated, by GM, to accommodate the ZR1(as the ZR1 came out in 2009), so no scaling factor was needed. The other Vette in the vid was a 2007 Z06. That car did have to get a scaled tune.

However, there's a wrinkle to what we are used to in the LT1(and early LS1) world. The VE table got nuked in favor and an equation based VE system. So I could not see what happened to the VE table as we are used to it. In EFI Live, there is a "Virtual VE table" and you use that table to scale the VE, then the software will back calculate all the other factors to give you the percentage of VE you asked for.....and to add more to the puzzle, GM combined several constants in the speed density equation to create what is called a "GMVE" value. So it's not a "VE" percentage directly.

What I can tell you is that 100% for an engine, in the VE system we are used to, is not 100. 100% generally comes at a value of around the 88 mark. So anything above that is considered boost of some form.

As to the MAP sensor change, I would expect it to be "linear" if the voltage operating ranges are the same.....but I don't know how that works in the LT1 world. I'm just guessing and could be flat wrong.

For the LS world I just watched, with the advent of the ZR1, GM provides a 3 bar MAP sensor for it. When changing to that sensor in the 2009 LS PCM, the MAP sensor coefficients did get changed when the new sensor was installed.

kingtal0n

iTrader: (1)

I could show that a head/cam combo has a higher IAT than a turbo setup, by simply providing the turbo setup with appropriate cooling equipment/conditions. The same way I can show that a head/cam combo on an LT1 at a very low IAT is just as dangerous to the engine as a high IAT (too many air molecules = death). If I can kill the OEM engine with a super low temp, or a super high temp, then clearly the high temp by itself is not a direct cause for engine failure, it only makes a certain special case for itself, and doesn't make boosted air "special" with respect to ruining an engine.

kingtal0n

iTrader: (1)

pressure difference is the word you are looking for. scavenging, acoustic tuning, sucking, blowing, is all a pressure difference or differential if you wish. stop and re read that pressure difference is the word bird I will be repeating over and over as pressure difference drives a net movement of air molecules so long as it exists. if you send a sound wave through a stationary pipe you may create a measurable pressure difference at some point along its length, as sound travels through air it can create a wave, just like in the ocean, where a bunch of air molecules group up together at a specific point at a specific time. Then the question is, what sound produces the biggest pressure difference, what are my options for making sound, and then you start asking when or how often can I create that sound, when based on what sounds I have to work with. Creating pressure differences where, and when you want them with pinpoint accuracy in single or mass production scale is one benefit of modelling. Modelling allows us to adjust one or many variables while holding everything else constant to find optimal conditions per application, and then if you want you can stamp out more of them the same way.


I never said having a turbocharger disconnected would improve economy. I am in fact suggesting the opposite: weld the waste shut and cruise on the highway with the correctly implemented turbo/manifold, record MPG. Next, open the wastegate fully, or re-install factory exhaust (will it provide adequate acoustic tuning? This is a variable) and re-measure economy. MPG fuel economy will be the same or worse. In other words, a correctly implemented turbocharger system can improve cruise economy. And now I am prepared to talk about why and provide a few references.


As the piston is descending and the intake valve opens, the resulting pressure difference causes air molecules to move. If the exhaust valve happened to be open at the same time, as is often the case for a moment, a wide variety of conditions and situations exist depending on the operating condition combination. It is up to the engineer to decide how to utilize this situation, but for now, Let us assume
the exhaust valve is closed, pretend it does not exist yet, and the container is sealed and you are driving down a piston plunger, like a syringe just sucking it back with your hand pulling in air from an open valve at the end of the syringe. If you cap the syring and pull the plunger back you will eventually be fighting that plunger. In fact at some point you will no longer be able to pull that syringe back because it will become very difficult. This resistance lowers fuel economy in a piston engine, because even with an open valve, there is some resistance, some energy is subtracted from our rotating engine to create a space for the atmosphere to "push in". Any resistance to the piston moving to the end result of creating a pressure difference in the cylinder is wasteful, and a compressor(turboharger) driven by exhaust energy is capable of creating a pressure difference at the intake valve such that the piston no longer has to create much/any of this suction effect of wasting energy trying to pull back the syringe, and in fact it may be even further reduced or even compensated as is air rushing in to pressures above atmospheric (under boost the effect is more pronounced, maybe helping to drive the piston down).



If I blow into the syringe hard enough, I could actually move the plunger down without using my hand to pull it back in a traditional way. More energy is subtracted from our rotating engine if we place the demand on the piston to draw air. In an argument towards engines without turbos, David Vizard has shown about twenty+ years ago that an exhaust system on a naturally aspirated engine could exert around 10+ times the suction on the intake valve as a descending piston, and it has been a vital part of modern N/A engines that they utilize exhaust designs for better engine breathing at reduced energy cost (pressure differences assisted by leaving exhaust gasses or so called "scavenging" help renew cylinder charge). So this is where I point out that if the engine has a particularly well designed package of parts, consider for a moment an engine like the Honda S2000's K20A3, an 11:1+ compression 9,000rpm capable 2.0L which has a nearly perfectly flat torque curve across the board (from what few dyno I have seen) and it got that way because of a variable camshaft computer controlled valve timing and a well designed exhaust system that provides all of these benefits to cylinder fill we have been discussing (specifically well timed pressure differences for that particular engine's operating range). In such a case, adding a turbocharger might not add much economy, if any, since the original system and valve timing was already so well coordinated, it would take a re-engineering (another great model, a whole new design and more R&D) to find an improvement. However, in most cases, engines typically lack that kind of extensive modelling, that level of R&D if you will permit, and so their OEM systems are not so "perfectly tuned" and thus, adding a turbocharger is usually going to improve economy on a random engine, especially if the original exhaust system was not designed well enough to suit the new application demands (you aren't actually adding a turbo for economy, after all...). As a side note, we will also desire a low pressure below the piston as well, in fact using some of the pressure difference created between the compressor wheel's inlet and the air filter, this intermediate space is connected to every OEM turbocharged vehicle's crankcase via baffled passage and allows the compressor wheel to ingest some of the crank case air molecules, to help create the low pressure below the piston which helps keep the oil clean from combustion byproduct.


Anything we can take out of our moving exhaust flow before its gone forever and apply it to the moving piston we can get something back in terms of economy. The exhaust valves are not open 100% of the time and so those cylinders are "blind" to the exhaust system conditions while they are closed, except of course for conditions which permit the exhaust valves to be open by accident (weak/failing spring).


random sources;


https://www.quora.com/How-does-turbo...s-fuel-economy
""In normally aspirated piston engines, intake gases are "pushed" into the engine by atmospheric pressure filling the volumetric void caused by the downward stroke of the piston (which creates a low-pressure area), similar to drawing liquid using a syringe. The amount of air actually inspirated, compared to the theoretical amount if the engine could maintain atmospheric pressure, is called volumetric efficiency. The objective of a turbocharger is to improve an engine's volumetric efficiency by increasing density of the intake gas (usually air).
So using a turbocharger has reduced a portion of power the engine consumes for itself..."

notice in the above normally aspirated example, they refer to the atmosphere "pushing in" the air, as opposed to it being "sucked in by a piston", either way is correct but ultimately you need to see that the miles of air molecules above us are in fact "pushing" themselves into spaces we provide.


http://www.edmunds.com/car-buying/tu...-more-mpg.html
"In addition to increasing power, turbos make use of the exhaust gases that otherwise would spew from the tailpipe as wasted energy. Turbos and superchargers both reduce the amount of work the engine has to do to breathe in the fresh air, increasing its efficiency."


https://en.wikipedia.org/wiki/Turbocharger
"A turbocharger may also be used to increase fuel efficiency without increasing power.[22] This is achieved by recovering waste energy in the exhaust and feeding it back into the engine intake. By using this otherwise wasted energy to increase the mass of air, it becomes easier to ensure that all fuel is burned before being vented at the start of the exhaust stage. The increased temperature from the higher pressure gives a higher Carnot efficiency."

kingtal0n

iTrader: (1)

I read through some of the VE question/VE table talk. What I want to empasize is that the computer is "dumb" i.e. it does not actually know if the engine is in a good state, or if you are simply running the ECU on a test bench with simulated inputs. That said, if you KNOW what Air/Fuel you want, and you have a way to adjust it, you will adjust the values on the screen in front of you to achieve whatever the desired air/fuel ratio is you want, even if the computer thinks something completely insane. One time I tuned a 2.0L engine running the wrong MAP scale, the map would read 22psi when I was around 17psi. Did I let that stop me? Hell no, I just entered values necessary to get the engine to run the way I wanted, ignoring whatever the computer was "thinking". If you already know you want 11:1 and 9* of timing at 18psi of boost on a given platform, you do whatever is necessary to squeeze it from the computer, regardless of what the computer "thinks".



Alright, I give you two cookies. We produced around 10-15 of these cookie cutters from 2004-2007, all similar with mostly stock engines for re-sale in the $25,000~ range complete cars with custom paint jobs in house. Good for about 27mpg in a 3000lb RWD platform on pump gas, the low mileage, stock RB or 2J engine series are pretty happy around 600bhp in a daily driver for 10+ years with minimal maintenance. To help them live, I recommend strict guidelines for oil changes, RPM limitation, and boost pressure. These are "played out" the engines no longer come in great condition from Japan for reasonable price, they have aged, and so are no longer high quality options in many cases (I do not recommend this swap in 2016) I have other cookie cutter go-to options these days, and I am looking at the LSx platform next for similar swaps.





I would no longer allow a vented catch can, this was back before I made such a big deal about PCV or I would have made a stronger case for it. Any Future setups may incorporate an inches of water gauge on the pre-compressor air box that evaluates PCV action during boost (so I can adjust as necessary at the filter).

hrcslam

So Scavenging....

Ummm.... Actually that's exactly what you've said.
Not how it (physics) works.

I understand the theory of piston push with boost. People have done it with twin charging, using boost of Turbo's to drive a Supercharger, the Supercharger then belt drives the engine. However, not once has it been used to improve fuel economy; not to my knowledge. Care to provide an example of real world results that an engine has improved fuel economy in a vehicle with a Turbo, same engine? Every engine with boost does this. Simple math actually.

But you're ignoring where that push comes from. The Turbo converts heat into mechanical energy, it also generates heat. That heat generated is on the wrong side of the engine and must be combated. That heat takes energy to dissipate. Intercoolers help, but as much as they help they are not enough. Therefore you end up doing 2 things (even with the intercoolers), you run richer (read: energy from the cool fuel is absorbing the heat, now wasted energy) and you run lower compression ratios. The effect on a lower compression ratio means you also have less extraction (expansion ratio) of every power stroke to absorb the power of the expanding fuel/air. See where this is going? None of this helps your argument. And neither do the links you provided below.

Every single application of a Turbo, from my knowledge, is applied to gain power. In vehicles that Turbo's are used to gain FE, they do it by using a small engine, then adding a Turbo to gain power. Again feel free to show me a vehicle that has gained FE by adding a Turbo without decreasing displacement.

So a Venturi at work huh? This changes nothing.

Scavenging does this.

Notice in that reference they (random people talking in a forum BTW, like this one....) say in THEORY and they reference Wikipedia? Umm not a very credible source. In reality, this doesn't happen. What this guy states is that if you COULD reduce the AFR to the same ratio (or leaner) as the NA engine it would be more efficient. The problem is that you can't. This also ignores Expansion and Compression ratios. Both AFR and SCR/ER are things that change between NA and Forced Induction engines because they have to due to forced induction; both of which directly impact (greatly) thermal efficiency and therefore vehicle FE.

You'll also note how they say the engine MUST be downsized to increase FE.

Here's the rest of the snipered quote you provided....
"But while turbochargers restrict exhaust flow, making the engine work a little harder to completely empty each cylinder after combustion, they do not sap as much mechanical power from the engine as do superchargers, making them more appropriate for smaller, less-powerful engines."

A little more from the guy Quoted here.....
"Of course, Grissom also reminds us that the point of turbocharging in most cases these days is to make it possible to use a smaller, lighter and more fuel-efficient engine than might otherwise be practical for overall drivability. Grissom says that turbocharging allows you to increase power using a smaller engine."

And another snipet.....
"It's the kind of elegant solution engineers love to talk about. It's a relatively simple device that rides along without diminishing performance when it's not needed, but spins into action and packs your engine with more power when you need more zip. It lets you live happily with a small-displacement engine that gets great fuel economy and yet comes through with more power when you need it: while merging onto the freeway, for example."

You can't pick and choose what you want. It ALL applies. Physics is silly like that. It doesn't care if you don't want to know it, it does what it does anyway.
Again with Wikipedia? Seriously? How about someone more credible than an anonymous author with free reign? I didn't even click the link, that unreliable.......

It would be helpful if you actually read the links you provide first. As stated above, they are not helping your argument.

ACE1252

I have no idea why you quoted me and then wrote the above. I was simply describing what was happening in the newer LS PCMs with regards to speed density. It had nothing to do with how or what you are tuning.