A small part of the supercharger workings that its unrealistic

Sorry if i am posting this in the wrong board, but there are just 2 or 3 small little supercharger simulation features that i find unrealistic, i will keep this short:

1- The supercharger should take away a little bit of the N/A power, the bigger the supercharger, the more power it draws, sorry, but i am not the expert on superchargers that knows EXACTLY the amount of compression from the supercharger vs the power taken by the pulley to drive it. But i noticed in the torque curve that using a bigger supercharger doesn't change the N/A power rating.

2- You should still be able to have a carb swap option with the supercharger. These 2 are different things, and you should still be able to go around different superchargers/Turbos (forced induction modifiers) and fuel injections/Carbs (fuel feeding modifiers) as different objects. I also noticed it would be nice to have more carbs types too.

3- The low end RPM torquecurve should be increased, as it is right now the supercharger has a torque curve way too similar to the one of a turbo. The main difference between the two would be that the turbo can pull more air at a similar size and same psi, and has no parasitic power that it takes from the crank to power itself, while the supercharger main advantage its that its torque curve is mostly flat, or very flat on low-mid RPMs.

While we are at it, are we gonna be able to have more options than "single turbo" setup for a few cars and "twin turbo" for others? i would like a way for you to add a turbo based on your specs (a little bit more variety than with the variable turbo) And then being able to pick extra turbos and do the same, that way you can have a gigantic turbo and a smaller scale of turbos to reduce lag.

 

3 sounds alot like you're on a centrifugally supercharged engine. A centrifugal compressor is the same compressor type as used on a turbocharger and does require to spin at a meaningful speed before it produces any meaningful boost. They are the only supercharger with non linear boost.

Otherwise, roots and twin screw, they are linear multipliers on the base engine, doesn't give a flat curve. On paper talking purely hypothetically and ignoring issues of efficiency and parasitic loss, a 1 bar boost would double the torque at a given rpm, this doesn't give a flat torque curve, it doubles the existing one - with an emphasis on this being on paper.

 

1- Glad to know. Would like to see some indication of it somewhere tho.
2- Glad to know. Will be hoping for it.
3- Even real life torque curves of the twin screws shows a pretty stable low to mid torque curve, but if you think based on a few other TS S/C that this torque curve its realistic as it is, i believe you. Although if the TS is going to MULTIPLY the torque to begin with it should run at some high PSI, depending on the supercharger. I have heard of superchargers that run at positive power just at idle. And yes. I mean Twin screw.
4- That's a real shame. I do hope that gets changed since it provides an obvious advantage to those cars that support twin turbo from the getgo.

 

The End result would be infact the same, but i am not speaking in terms of how easy it is to have a custom made turbos (it would be easier without having to go into the engine/car configs) But if this idea DOES gets implemented, the main advantage in my eyes would be an easier time to do so when the campaign or story mode is implemented, it would be easier to increase more power onto a car on your own without having to modify something in the files by just being able to change the way a turbo works, and reducing turbo lag by adding a smaller one.

Not a "must-have", but something that would be nice and realistic to see implemented.

 

Totally on board with a much more in depth tuning system.
Different fuel systems, intakes, forced induction, exhausts, etc. Rather than just a modified torque curve, actually having different parts that have their own simulation, would be really immersive.
Actually seeing the effect of a fuel injection swap on an old carbureted V8, rather than just modified torque numbers.
The ability to miss and match different performance parts would be fantastic.
Essentially more like your traditionally racing sim.

 

I did made a post about that a few months before. However i am not asking for everything to be done ASAP since i know the team is busy with west coast, italy, maybe making optimizations on AI and FPS with several cars since i doubt the career mode is not gonna incluide freeroaming with civilian cars or something like that.

But yeah, BeamNG has a lot of potential to go from "a game about cars crashing" into a "soft body physics car simulation game".

It could try to get the freeroaming and tuning aspects that people loved from NFS underground.

If its up to me, i think that they should be getting fuel octane and compression simulation done first, that way there is a real reason to reduce compression and reduce power (while out of the power band of the turbo) before it kicks in.

 

I just noticed that the Grand Marshall supercharger produces less torque at low and mid RPM but makes a lot on the higher end, like a turbo. Dont know if it was intentional.

 

You can look under the hood and see why: the Grand Marshall has a centrifugal supercharger which is the closest thing to a turbo that isn't one. Basically it's a turbine compression driven by the crank, so it needs high RPM to produce boost. That's in contrast to the roots superchargers found on the D-series, H-series and Roamer, which produces boost in line with the current RPM. So yes, it's very much intentional. Though I think it's a big laggy even if it was a huge turbo, it saps power everywhere in the rev range except at the very top, where it makes insane boost.

 

Dude.


What.

All superchargers are driven by the crank. Centrifugal superchargers produce less power than twin screws and have less lag, if it has any. By 2k RPM the S/C should be already producing 8 psi of boost or more.

 

I think I may have confused you with my last few sentences - I was insinuating that it was almost laggy alike to a big turbo... poorly worded comparison on my part. I was basically agreeing with your sentiment that the centrifugal supercharger on the GM doesn't contribute very much down low.

Of course all superchargers are driven by the crank. What I mean was a centrifugal supercharger is similar to a turbo because it's a turbine, though driven by the crank, as opposed to a screw-pump (ie roots supercharger) driven by the crank. The turbine aspect of a centrifugal supercharger means boost isn't linear like a screw-pump supercharger, requiring high crank speeds to produce lots of boost. So, in some ways this accounts for the lack of low end boost, but not entirely.

 

I am not the MOST well versed in the aspect of forced inductions, but i think you've got a few things wrong.

Turbos dont have lag because they are so far away from the actual carb/intake (unlike root/twin screw S/C), they have lag because of their turbine buildup. While centrifugals might not have the same efficiency as roots since the air has to travel from the S/C through a small part of pipes to reach the intake itself, they dont (*shouldn't) have much of a difference compared to roots in terms of lag or low end torque, AFAIK the centrifugals CANNOT blow a lot of power due to their size and turbine size tho.

There are, in fact, ways that a centrifugal could produce very low torque on low and mid RPM but high RPM, but that would be because the centrifugal S/C section of the belt is giantic (bigger than the crank pulley) and it would take very high crank RPM to have enough torque to make the centrifugal S/C spin, but that's a "what if", and i am pretty sure that it would not be an advantage for those with centrifugal superchargers to have this kind of design.

 

i can actual get turbo torque curves to go from 0 boost to all boost in 500 rpm THATS 0 TO 500 rpm
not super chargers tho

 

You mean Ingame or IRL?

 

its normal, a centrifugal compressor requires to be spinning at a high RPM to actually produce any meaningful boost, go look at datasheets for real centrifugal compressors. They do genuinely function as you describe seeing on a grand marshal. I love these threads where you come in, bash stuff and its immediately proven to be your own lack of knowledge. I even referenced this above.

 

I am by no means an expert all the same, but I fail to see what I have incorrect. Please point these things out to me, I'd genuinely like to ensure I'm not asserting fallacies.

But they DO have a noticeable difference at the low end because a centrifugal supercharger doesn't really produce boost at low RPM, whereas a roots-style does!

Also, centrifugal superchargers are actually more efficient compared to other types, and as a result they have less of a parasitic loss compared to a roots-style positive displacement. Less moving parts, overall less resistance, etcetera etcetera.

However, I must re-iterate now, that centrifugal superchargers do NOT produce linear boost. Allow me to explain:

---

For every rotation of the impeller of a positive displacement supercharger (like a roots-style blower), the same amount of air is compressed. The exact volume of this air is (basically) the space between the impellers where the air is drawn in and compressed. Thus, no matter how fast the engine is revving, the positive displacement supercharger always produces the same amount of boot per RPM; the boost simply increases as engine speed draws in that small pocket of compressed air at a higher rate.

Example of positive displacement supercharger curve:
1000RPM > 1 unit of air is compressed and sent into the engine
2000RPM > 2 units of air are compressed and sent into the engine
5000RPM > 5 units of air are compressed and sent into the engine
8000RPM > 8 units of air are compressed and sent into the engine

and so on. Boost is linear because 0.001 units of are are sent to the engine per revolution of the crank

Powerband Example:
Low RPM > something, something, something, something, < High RPM

---

For centrifugal superchargers, the turbine aspect of the supercharger means boost is NOT linear; at low RPM, the turbine fails to compress meaningful quantities of air and the engine is running with almost no boost. This is because whereas a roots-style blower is an air pump, the centrifugal type is a glorified fan. If you hand-cranked a roots supercharger it would be difficult to do but produce the same amount of boost/rpm that the engine makes when running; to recall, we'll say 0.001 units of compressed air. In contrast, if you hand-spun a centrifugal supercharger it wouldn't compress anything because you're not spinning it fast enough. But at higher RPMs, the turbine incrementally begins to produce boost, which makes the engine produce more power, which makes the engine spin faster, which makes the supercharger spin faster, which makes more boost. This is a positive feedback loop where both variables increase each other. In result, it makes the supercharger boost curve of a centrifugal supercharger behave like an exponent. So, in math terms, centrifugal supercharger's airflow is equal to the square of its driven speed, which is only a ratio of the crank speed.

Example of the curve in action:

1000RPM > 0.1 unit of air is compressed and sent into the engine
2000RPM > 0.4 units of air are compressed and sent into the engine
5000RPM > 2.5 units of air are compressed and sent into the engine
8000RPM > 6.4 units of air are compressed and sent into the engine
(I've divided the units by ten just to make the numbers more realistic; and this is assuming the driven speed is equal to the crank speed. Just an example, not an application)

THIS IS WHAT CAUSES IT TO SEEM LAGGY.

Powerband Example:
Low RPM > nothing, nothing, nothing, something, EVERYTHING < High RPM

Completely agree; with boost controllers and the right size of turbine it's possible to get low end power from a centrifugal supercharger, but it innately produces more pressure the faster it is spun so you're fighting physics here.

Sources:
http://www.redline-motorsports.net/supercharging-roots-vs-centrifugal/
http://www.speedhunters.com/2015/04/knowledge-boost-selecting-a-supercharger/

 

Should be noted, centrifugal while dropping on low end versus roots, can be intercooled far more readily than roots/twin screw and importantly: achieves higher boost pressures. Design of roots/twin screw doesnt really allow them to reasonably achieve more than 1 bar boost across the intake and exhaust sides (theoretically to hit 3 bar, you'd need 3 blowers compounded), even overdriving them doesnt really work around it. Centrifugals can hit these pressures without compounding. That and where a centrifugal is more efficient, it heats the air less causing the air charge to be denser than a roots/twin screw. 1bar of warm boost is not always the same as 1 bar of cold boost

 

Yeah, that's true. Plus the fact that they generate less heat to begin with and have parasitic loses, and you've got an ideal forced induction setup for a racecar.

 

ok



Btw its funny because i searched for centrifugals torque curves and there has been both S/Cs that only show increased power band in the high end RPM and others that were able to keep a higher torque band all above the N/A one.