P.s. is your street mandatory interlocking driveway? And did that bear that was near your house eat my memory card?
jspazz, your tie lines need to be on the dotted green lines for constant blower velocity.
PR shouldn’t be a design goal, its not your boost perse. Keep in mind the fluidity of pressure and velocity in flows. Boost is not a static pressure.
blower speed determines flow
flow determines power
pr measures flow restriction
flow restriction reduces power
internal blower bypasses can be used to prevent the blower from running beyond its desired efficiency range, but shouldn’t be your control system for limited output
and I’ll pose this question, encourage thought hopefully…
why are the blower speed lines curved/negatively sloped… lots of time you see the false assumption that same blower speed = same air flow, clearly by the slope of the blower speed lines this is not the case?
its fairly simple but provides good insight into the dynamics of the system
The lines are plotting a dot using a given flow and PR, so no, it does not follow the blower speed lines.
I am highlighting to you that for the estimated flow and PR (black lines) that stage II cars are at right now, the 1900 has more efficient compression than the 1320. So it will indeed have a denser charge at the same mani pressure, and thus more power.
In terms of the red lines, I am assuming 2.4 is the maximum pressure ratio allowed, so the pulley will be sized accordingly (using the speed lines shown in the map for a given flow). The flow is determined at this point by how much the 3.0T can gulp down, which is an unknown, so the 1600 m^3/hr is a guess as in ‘around 500 WHP’. All we want to use the compressor map for is to ensure we’re somewhere around the island and not on dangerous territory. Maps are not always accurate, even from the manufacturer, likely due to differences in where they measure p1 and p2 for the PR data.
So yes, without changes to the head, intake runners, charge coolers, PR in this case is the only driving force to push more air through those heads. Bigger blower will give us more pressure. And yes, the bypass will HAVE to control output, since you will possibly need to limit for a.) pump gas or other detonation issue or b.) not exceeding the pressure ratio limit of the blower (which Eaton states at 2.4).
Audi actually uses the blower recycle as the throttle anytime the mani is over atmospheric pressure, check out the engine study guide. Weird, huh?
A positive displacement blower will have “some” leakage, as PR increases. That’s all. The assumption that one turn of the blower will push 1.35 L doesn’t hold ‘exactly’ true as PR increases, but it’s pretty close. It would be impossible to have absolutely zero gap/tolerances inside the blower.
Lol…
It actually looks exactly like my neighborhood, but I didn’t make the picture. Email me your addy like I said, I’ll drop it off…
I see what you were illustrating there now, fair enough
I’ll see if countvaugh can chime in, his explanation of how he has sized blowers/pulley ratios agrees with my approach, PR is a measured quantity
flow is inlet flow to the blower at some standardized temp/pressure minus backflow. if the motor cannot handle that flow pr increases, more backflow through the rotors. If you assumed that the flow is outlet flow at those pressures your air mass would be able to support massive power.
quick calc, I’ll check it later I’m in a precarious spot
airflow = 960cfm = 27184 L/min (kind of low after I looked back)
pr = 2.0 = abs pressure = 2 atm (again low re 2.4 max)
t = 100*F (who knows, just threw that out there)
air mass = 227184/0.0821311 = 2129 mol/min air
= 35.5 mol/sec air
= 7.5 mol/sec O2
c8h18 + 12.5O2 => 8co2 + 9h2O
7.5 mol/sec O2/12.5 mol O2/mol c8h18 = 0.6 mol/sec octane
dHcombustion octane = -5.4 MJ/mol
energy release = 3.23 MJ/sec = 3237 kW = 4000+ bhp
ecus do strange things with load based programming, my car used to back the throttle off at higher rpm despite it being floored
beem, so you’re saying you would not use boost as a guide…rather build your system, then see what boost turns out to be
a.k.a. you’d rather make your build…not build your boost.
I believe ArthurPE was speaking the way jspazz is…starting with boost, then working back from there. Seemed backwards…boost isn’t your goal…power via air and fuel is your goal. You make your goal and boost…well let it be what it may/needs to be to meet that goal.
Yeah beem, I generally use 1 lb/min = 10 bhp (crank), so I figure our 460 bhp stage II car will flow the 1200 m^3/hr after a quick calc.
I guess without a flow bench, it’s not like I could test the rest of the system (cams, heads, etc) for what the motor can flow under the blower. So yeah I’m making a lot of assumptions based on what we can see it flows now, and using the modeled flow in the logs tells us. I could plot WOT airflow at different RPMs on the curves, I guess, and that should tell us more, but just looking at where we end up on the 1900 curve when talking about 500 whp tells me for sure we are in the ballpark, no need for a 1650 upgrade.
But again, I would say our high compression wouldn’t allow much room for extra boost anyway, not on pump gas, see what I said about APR S2 extra boost vs REVO extra timing: right now it’s pretty much a wash. I’m sure direct injection helps with the CR, but to what extent? Id think some people might have to blow some ringlands first to tell us the whole story (prime dont forget to log each run! :-).
What do you think?
its 10.5:1 correct? I think you should have room for more cylinder pressure given the DI magic.
the way I model the system in my head is that the airflow stagnates in the cylinder, thus converting dynamic pressure to static pressure, increasing density. This stagnation pressure is the pressure to use in the torque equation that arthurPE favors, not boost, which is only the static portion of the air charge (its not a pitot tube). So to me boost means nothing in regards to power, I could partially block a port and it would still flow but it would lose energy due to the restriction, less energy, less total pressure in the flow and less stagnation pressure.
so since boost doesnt mean much I think your limit comes from a torque number or too much heat… now this is where boost is useful as a measurement/design constraint. I can use it as a celling, open the valve to limit the blower from going into excessive poor efficiency ranges. The isentropic efficiency is showing you how much effort is wasted, and wasted energy normally becomes heat, which the intake charge will soak up. so if we know that the heat is going to melt piston crowns, predetonate etc, we can use the boost bypass valve to divert flow and reduce pr and increase eff and reduce Q.
if the worry is rods instead of pistons, then cylinder pressure is the concern, so itd be better to run the blower slower to keep the enthalpy change in check.
in this vein we now can make the arthurpe equation valuable… say we make sakis estimate of 634bhp… (7k rpm say)
pmep = Tnc/Vd * 2pi
pmep = cylinder pressure (Pa)
T = torque = 634bhp/1.33 = 475ftlbs = 644 N*m
nc = 2 for 4 stroke
Vd = displacement = 3L = 0.003 m3
pmep = 4pi * 644/0.003 = 27 bar, thats very high a 1100bhp koenigsegg is at 28 bar
now that I think of it, this isnt the arthurpe equation
I’ll look at it more later today (re estimating), but 500whp sounds plausible. All of this is therotical waxing but is a good discussion on the dynamics of what will actually determine the output.
And really I’m just glad whoever is doing this skipped the 1650
Edit: i started writing but you weren’t done your post, I’ll look more in a sec. Liking the discussion
Ok I guess you’re talking VE then…which I guess we could model based on all sorts of equations, but it would be a long exercise until we flow-test the head and cams. I am not considering pressure transients in the cylinder head due to cam duration, etc etc because its not really required - I would agree that if you increase cam duration, port the head, introduce other variables, then the VE changes and the intake mani pressure changes. But since none of that is changing, then more mani pressure equals more power.
We have realtime flow from the VCDS logs, and the 1320 compressor map, so if you want that data, it may be better to create a rough VE table at WOT using the real data. Then you can use that data to see how much flow the motor will gulp under the load of the 1900, and thus how much pressure will be built up in the mani (to ensure we do not exceed 2.4, if that is the real limit).
if it helps any, the way I look at these things is mass and energy balances, my education background is chemical engineering, and the car is a little chemical plant with two mass inlets and one mass outlet (evap system be damned)
and yes I do agree, same system, more boost = more air mass (and until the fringes more power)… I tend to think non concretely though so that may be part of the disconnect
J, I’ll do my part so whatever it takes! LOL Just enjoying reading and learning from you and Beem… I sincerly appreciate all of the information even if no one has really made a guess on ET and MPH… lol
its always fun to talk about the theory, unfortunately oppurtunity is limited it seems.
I think your guess is definitely fair on your car, mid to low 11’s and low 120s as long as the motor can handle it (whos the guinea pig?)
Lol I could tell that you’re a chem eng, so am I…
I’ll get that flow, rpm, mani pressure and temp from my logs and we could piece together a plot of volumetric flow at WOT of the 3.0T under the blower, since we have the rest of the data from the TVS1320 map.
well, we needed to figure out where the blower was going to be working first PT.
So, I’d say you’ll be 500 whp…4000lbs…425 wtq…decent torque curve but nothing like the TVS1320 in stock form curve…and at my track, with APR tuning it I’d say on pump gas the car would run 11.70 @ 120…and a bit better on race 11.40 @ 124. At your track maybe a hair quicker as they seem to know how to prep! Frigging cayuga. Basically I’ll predict TTS blower RS4 type performance with you on race and them on pump.
Then I predict you getting mad, calling JHM to tune the 1900 kit…them saying no…you crying…selling the B8, buying an RS5, getting a JHM blower and running 10s. 
I agree with Saki’s times…hey Prime, are you ever going to run pump then? You must have the pump program by now…
beem, like I said I appreciate learning about the math and theory and anything else you offer up… 11.3x at 121.xx would be my guess… I am sure I’ll be the tester at the strip from a dragrace standpoint… will see A. How does the DSG hold up? and B. How does the motor hold up? lol I don’t think either will be an issue…
Saki, I think your trap is optimistic… either way will be fun to see… Oh and I could see a a few or more of your predictions coming true…
J, I had to look but I do have a 93 program… I can give it a try but the weather will hurt me as well… There is a gasser race(old cars only) this weekend so will see how the weather is the next few weekends…
Some lofty estimates here
http://www.audizine.com/forum/showthread.php?p=7769556
[QUOTE=blackESfour;7769556]the kit will be coming in stages… as from what i hear (cant mention names) First package will involve a new blower, Bolt on, and no internals needed. Good up to 500whp. Then another stage with Fuel kits etc… in increases of 550whp, and final stage of Built internals climbing to 600+whp. As for prices… im sure the last stage will be close to 15k or more.
[/quote]
if he thinks a built motor B8 S4 + big blower is going to be $15,000 he is mental. Try $30,000.
APR will charge $15,000 for the stage 1 kit with the TVS1900 and guys will line up to pay it.