Andrew

I was wondering, what would happen, how would I estimate the power increase if we land outside the choke line on the compressor map?

So for example at maximum turbo shaft RPM our airflow is 10kg/min at 2 atm absolute pressure (if we go higher on boost then that same turbo shaft RPM will obviously get us less volume of air) but for our engine we would need 12kg/min of airflow at 2 atm absolute pressure, the only way for us to get that maximum 10kg/min is to drop the pressure ratio by ~20%, meaning we have roughly 1.6 atm absolute pressure at 10kg/min, BUT, our compressor map shows that 1.6 atm is below the choke point. So I was wondering what would happen in this case, how would I estimate power output?

I know that typically a rough rule of thumb used is take the absolute pressure and multiply by current torque at a certain engine RPM (but that works if we are assuming we have an intercooler and whatnot in place) but I just don't know exactly what to do in this case, where we can not get back inside the compressor map as the engine is too big and requires too much volume vs not enough pressure (and yes, I know that we shouldn't choose such turbochargers that choke up the engine, but this question out of pure curiosity, WHAT IF).

And yes, I do have somewhat of an idea why the choke line exists (though it's nowhere near as easy to grasp as the surge line). The lower the pressure, the higher the air flow velocity, add into the equation the RPM of the turbo shaft and we get

Does anyone have access to a BSFC curve from a semi truck?

So I was reading a bit about ohms, it's a resistance. I don't know if I got the grasp of it, but is 1 ohm basically a resistance of 1 watt (so x amount of watts + 1 ohm resistance = x watts - 1 watt) or am I wrong here, I'm stuck.

So I read this site: https://sciencing.com/how-8643971-convert-wattage-... and according to it, this https://www.micksgarage.com/d/heated-accessories/p... heater would increase the air temperature inside a 3 liter container of air (~3.88g of air) by 206C if heated for 5 seconds

160W * 5s = 800j

800j / 3.88g = 206

206 / 1 (specific heat capacity of air) = 206C

And for petrol it is around 215 times as hot, is this true or is something not right here? Or is this just assuming perfect conditions (i.e. no heat loss, etc)?

https://www.ultimatespecs.com/car-specs/Volkswagen...

What pistons does this engine use, anybody know? I only found out information about the block, head and crankshaft.

So I have thought about this and I was wondering if I was missing something out here. For this example we'll assume no resistance.

Two ~0.5 liter cylinders will be used in this example, one will be 2:1 (over-square), the other one will be 1:2 (under-square). Pressure will be 10 atmospheres (101,325 pascals).

Engine 1:

Bore = 108.4mm (0.1084m)

Stroke = 54.2mm (0.0542m)

Piston surface = pi * r ^ 2 = 3.14 * (0.1084 / 2) ^ 2 = 0.00922m^2

Force = surface * pressure = 0.00922 * 101325 = 935.115N

Torque = force * offset (stroke, leverage) = 935.115 * 0.1084 = 101.366Nm

Engine 2:

Bore = 68.3mm (0.0683m)

Stroke = 136.6mm (0.1366m)

Piston surface = pi * r ^ 2 = 3.14 * (0.0683 / 2) ^ 2 = 0.00366m^2

Force = surface * pressure = 0.00366 * 101325 = 371.234N

Torque = force * offset (stroke, leverage) = 371.234 * 0.1366 = 50.711Nm

Then due to how the sin wave is, the average "useful" torque translates to about 60% of the max (get the average on a sin wave, it is around 60%) so 101.366 * 0.6 = 60.8Nm for the short stroke engine and 50.711 * 0.6 = 30.4Nm for the long stroke engine.

Overall, our result is actually the OPPOSITE of what most people would think is true because everyone thinks that the bigger stroke improves torque. But I would like to ask, am I missing one big chunk of information here that is a huge dis-service to the long stroke engine? Because this seems like FAR too many drawbacks for a long stroke engine (limited breathing, low torque, and slow revving).

I don't get it, what makes higher rpm a requirement to build boost? The only thing I can think of is the fact that with more exhaust (due to higher rpm) the exhaust manifold pressure rises and therefore provides more forceful expulsion of exhaust through the turbo, helping spool it up. What other things (apart from the compressor map) can dictate where the threshold is and why that happens?

Has anyone ever made a pump duse (I think that's the correct way to spell it? Well that's what Google tells me at least) conversion on an OM606?

How would I go about calculating the air resistance given the angle of the blades, the shape, dimension, angular velocity and any other details that may be necessary?

I want to find out roughly how many Nm of torque I would need at certain speeds to maintain.

What specifically has to be changed in the ECU when you straight pipe a car? Everywhere I go everyone keeps babbling on and on about tuning, but NO ONE states WHAT NEEDS TO BE TUNED. Is it extra fuel, is it spark/injection advance, what can it be?

Theoretically speaking, with size, the mass increases by x^3 (1^3=1, 2^3=8. So with twice the size, we get 8 times as high of a result, in this case mass) and then the rotational inertia takes that mass into consideration AND the radius (as the radius of the turbo wheel increases, the inertia, assuming same mass, increases by 4 times then. 1^2=1, 2^2=4) meaning that we have an exponential curve in terms of the mass we have to spin up.

So overall, the rough theory seems to add up, but I'm wondering, how much of it is true, how big of a difference in spool is there if we took a turbo that say, gets 200 horsepower efficiently and compare it to two turbos that can reach 100 horsepower each?

I would like to try and get more low end grunt from the engine and boost the turbo pressure up a bit, so as a result, it should have the same peak horsepower but earlier, and an earlier torque peak.

Would retarding injection timing help a bit? Would I need to make a custom intake manifold? Would I need to close the valves earlier? Any suggestions are appreciated

P.S. To those lazy to look up the engine, here is it -> https://en.wikipedia.org/wiki/BMW_M51

Logically speaking, with turbochargers it's a feedback loop -> exhaust drive turbo, turbo packs in more air (and allows more fuel as a result), more exhaust, better spool and so the cycle goes on. But then add a wastegate and that just starts to taper things off slowly.

So I'm trying to roughly visualize a boost curve. Anyone willing to point me at some sources of information?

Surge line I kind of understand, it's where the compressor is unstable as it cannot pump any more air, the pressure is too high and therefor it forces the air back. But the choke line I have a hard time understanding fully. Why is the choke line drawn at the bottom, where the pressure ratio is lower (unlike surge line, which is drawn on top)?

Like... there are a lot of them girls that would be the type to match you on Tinder (or any other app) and then ignore you. There are girls that quite literally, beg you to chat to them and then ignore you. There's girls that start showing off their body and then instantly block you, as if it was you being a creep and not them sending you photos. The amount of things I've seen girls do over the years, I'm seriously starting to lose faith in humanity and want to socialize less and less because of this weird-*** form of "communication".

Not to mention, the irrational way of thinking, selfish, arrogant, rude.

And no, I'm not being sexist, I heard from a few female friends that some guys do the same to them too, it's just that I'm speaking from my own experience here.

I have a Mitsubishi turbocharger and I found a number on it, but I really want to have a look at the compressor map, or at the very least, what it's capable of and what trucks it has been on (I've been told it's from a truck). Where can I find the exact turbo given the model number?

I only heard of a Perkins 2.5 liter 3 cylinder engine, can anyone give me anymore 3 cylinder engines that have close to 1 liter per cylinder?

What difference is there roughly in the average cylinder pressure in diesel engines with these three different fuel pump setups? (I'm talking not turbocharged yet)