Quote :

Boost is directly related to the flow rate of the exhuast. Whatever causes the exhaust to flow faster increases boost.

Not quite true.

To be specific, heat is the key. The exhaust turbine is driven via pressure differential between the inlet and outlet side of the turbine, and engine RPM does not have a really directly significant effect on that, at least it's definitely not the primary factor. 4000RPM at part throttle creates far less of a pressure differential than 2000 RPM at full throttle, because the engine is producing a lot more cylinder pressure & heat in the latter situation. This is probably what is being construed as "load". The turbines work essentially by very high heat high pressure gasses expanding "inside" the turbine, and that's where the energy is dumped into the turbine so essentially they are converting heat energy to kinetic energy. It's not like a pinwheel you get at the fair. This is why a large exhaust system benefits a turbo car so much, since there is a bigger pressure differential between the inlet/outlet sides of the turbine hence spool up times are quicker.

Of course, the more boost is generated the higher the cylinder pressures are and the higher the temperatures get and the effect enters a positive feedback loop. You'll get more boost the more boost is generated for that reason until the wastegate/controller decides to vent some exhaust gasses, or else the engine would overboost itself to death pretty quick. The effect would'nt be linear like that forever due to the efficiency range of the turbo, but you get the idea.

edit: some interesting banter
http://www.lfsforum.net/showthread.php?p=80394#post80394

Quote from Ball Bearing Turbo :

Not quite true.

To be specific, heat is the key. The exhaust turbine is driven via pressure differential between the inlet and outlet side of the turbine, and engine RPM does not have a really directly significant effect on that, at least it's definitely not the primary factor. 4000RPM at part throttle creates far less of a pressure differential than 2000 RPM at full throttle, because the engine is producing a lot more cylinder pressure & heat in the latter situation. This is probably what is being construed as "load". The turbines work essentially by very high heat high pressure gasses expanding "inside" the turbine, and that's where the energy is dumped into the turbine so essentially they are converting heat energy to kinetic energy. It's not like a pinwheel you get at the fair. This is why a large exhaust system benefits a turbo car so much, since there is a bigger pressure differential between the inlet/outlet sides of the turbine hence spool up times are quicker.

Of course, the more boost is generated the higher the cylinder pressures are and the higher the temperatures get and the effect enters a positive feedback loop. You'll get more boost the more boost is generated for that reason until the wastegate/controller decides to vent some exhaust gasses, or else the engine would overboost itself to death pretty quick. The effect would'nt be linear like that forever due to the efficiency range of the turbo, but you get the idea.

If we look 80% throttle plate opening or 40% throttle plate opening in two different rpm, then rpm is main element.

What affects to boost level, drivers point of view:
1. Throttle plate opening
2. RPM
3. How spooled turbo is (turbo rpm), can be also time.
4. any other small things, like amount of fuel, temperatures etc.

It is again different when building engines, but certainly that is not something to discuss here as all this started from claim that there would not be boost on part throttle and how that would need to be changed

Sure, some bit more modern turbo engine would be nice, now turbine wheel seem to be made out from lead or then exhaust manifold is rather bad design on most LFS turbo cars.

However if one can manage to spool turbo up there is boost at part throttle.

Quote from JTbo :

now turbine wheel seem to be made out from lead

ROFL

I very much wish the vac side of the gauge was included, I've never seen a pressure gauge used for engine boost that didn't have the vac side on it was well, that'd tell more of what's going on in LFS. Right now you can get quite a bit of spool with no pressure over atmospheric being generated, so I would like to know what the numbers LFS is generating actually are.

Quote from Ball Bearing Turbo :

ROFL

I very much wish the vac side of the gauge was included, I've never seen a pressure gauge used for engine boost that didn't have the vac side on it was well, that'd tell more of what's going on in LFS. Right now you can get quite a bit of spool with no pressure over atmospheric being generated, so I would like to know what the numbers LFS is generating actually are.

True, if we judge by sound, there would be quite lot of vacuum at WOT when turbo has not gained enough rpm and as it takes long to gain rpm we are loosing for NA engine quite a bit, maybe bit too much compared to common IRL situations.

Quote from JTbo :

True, if we judge by sound, there would be quite lot of vacuum at WOT when turbo has not gained enough rpm and as it takes long to gain rpm we are loosing for NA engine quite a bit, maybe bit too much compared to common IRL situations.

What are you talking about? I'm a bit confused.

Quote from wheel4hummer :

What are you talking about? I'm a bit confused.

I'm talking from that time window before turbo spools up, time window that is quite long in many LFS turbo cars. Some may call it turbo lag also

I would like to see variable boost on some of the GTR cars perhaps, but it could come a the price of massive fuel consumption and more engine wear plus the likelyhood of your engine blowing up.

Quote from koreanbro :

this thread fails face down on concrete.

This thread resurrection fails face down on concrete.

Quote from March Hare :

This thread resurrection fails face down on concrete.

Indeed.

Quote from koreanbro :

this thread fails face down on concrete.

u guys havent heard of 1980's f1 engines.


1.5L turbo with 1500hp for qualifying trim

How many production car you can name with such power from litre figures?

Is XRT resembling a production car?

I did watch F1 cars with turbo engines live from tv when I was young, they were not too reliable

Quote from danowat :

Are you SURE that is how it is IRL?

I used to own.........a Renault 18 Turbo (back in the day), and I remember quite clearly that I had next to no boost until the engine was underload (which was normally near as dammit full throttle)

That's because the old Turbo cars used oversized turbos. So turbo cars were pretty much all or nothing. Todays Turbos cars use considerably smaller turbos which give a very wide spread of torque from the engine, as well as some boost on part throttle openings. I hardly ever give my car full throttle yet I can hear the turbo spooling up at pretty much any thing over 2.5-3k even on about 1/3 - 1/2 throttle or so.

Having said that, the turbo's in LFS date from exactly that era so thier on/of nature is actually pretty correct probably.

Quote from koreanbro :

this thread fails face down on concrete.

u guys havent heard of 1980's f1 engines.


1.5L turbo with 1500hp for qualifying trim

Instead of coming in and dragging icky teenage pop culture phrases with "u", (:rolleyes, why don't you contribute something useful like an explanation of what the hell you're talking about? Or did 80's F1's just pop into your head and you had to mention them in no particular context?

i drive a 91 mr2 turbo, and i can say that cruising at 80 mph generates some boost. then again, my turbo is pretty small, but its also pretty dead. i think the original suggestion is valid.