Why are you all arguing on a point, which is directly affected by each of your cars gearing? In LFS the turbo is only RPM related, when it comes to the speed at which it spools up ( e.g. @redline with no throttle > full throttle the turbo will spool faster than it will from 2k RPM ). Also, I shall use the XRT for this next explanation. the turbo in the XRT can not attain full boost untill 4k RPMs, the exhaust below 4k rpms is simply not enough to fully spool the turbo. This makes me remember also that new in patch Z there is also a lag between the time you accelerate and the turbo kicking in, is this the time it takes the exhaust to overcome the rotational inertia of the turbine?

EDIT: from wikipedia

Quote from Ricerguy :

In LFS the turbo is only RPM related, when it comes to the speed at which it spools up

I agree with you completely. It seems that the speed at which the turbo spools is related to the RPM in LFS.

Quote from morpha :

The turbo pressure increases linearly

No, it doesn't! Obviously, if you think about it, Ricerguy is quite correct. The rate at which boost increases is directly related to the RPM. So, the faster the engine spins, the faster the boost increases. Therefore the boost does not increase linearly. To try to prove this I am going to use outgauge and attempt making a chart of boost and RPM vs time.

EDIT:FFS I cannot seem to get the struct correct in python...FAIL!!!!!!!!

Quote from wheel4hummer :

No, it doesn't! Obviously, if you think about it, Ricerguy is quite correct. The rate at which boost increases is directly related to the RPM. So, the faster the engine spins, the faster the boost increases. Therefore the boost does not increase linearly. To try to prove this I am going to use outgauge and attempt making a chart of boost and RPM vs time.

EDIT:FFS I cannot seem to get the struct correct in python...FAIL!!!!!!!!

And once again you missed my point, I clearly stated it will increase linearly in any gear, full throttle

Quote from morpha :

at the same engine RPM

And if you scroll back up you'll see I was the first one to say that it depends solely on the RPM

At 5000 rpm with the throttle fully opened, the turbo pressure will increase EXACTLY IN THE SAME WAY in ALL GEARS, that is what I said the whole time.
The only reason why it doesn't produce as much boost in lower gears as in the higher ones is that the gears are to short to give the turbo enough time to spool up.

Quote from morpha :

And once again you missed my point, I clearly stated it will increase linearly in any gear

Boost doesn't increase linearly! The rate at which the boost increases, however, increases with RPM.

Quote from morpha :

And if you scroll back up you'll see I was the first one to say that it depends solely on the RPM

You said that boost depends solely on the RPM, and that is not true.

EDIT: As you can see in my chart, the higher the RPM is, the faster the boost builds.

Ok either get your facts straight or count me out!
What I said it that the amount of exhaust gas is solely rpm-dependent, which is what powers the turbo. Therefor, the turbo pressure is rpm-dependent.
The turbo's air compression / output in terms of volume is rpm-dependent, which is in fact the boost. That you can't see that boost in-game is because the BOV is open but that doesn't change the turbo's output, apart from letting the turbine spin a little faster due to the reduced resistance which is counteracted for by the fact that the throttle is closed, which then reduces the overall amout of exhaust gas.

Once again, at FULL THROTTLE ( = throttle 100% open, all of the compressed air is delievered to the intake manifold), the turbo pressure increases linearly in any gear while keeping the same engine rpm.

That this is not the case if you're accelerating should be obvious, simply because a shorter gearing will accelerate a lot faster than the higher gears, 3rd or 4th, depending on if it's a 5 speed or 6 speed gearbox.

€: Great, once again we're talking about completely different things even though I made my point as clear as it can be.
Your chart makes perfect sense but it has nothing to do with what I'm talking about.

Quote from morpha :

the turbo pressure increases linearly in any gear while keeping the same engine rpm.

Yes, if the RPM stays the same then the rate of boost increase is staying the same, so the increase is linear. But you didn't say "at the same RPM" earlier, you only said "boost increases linearly" but you DID NOT say "at the same RPM" afterwards earlier! If you would have said "at the same rpm" in your previous posts, then I would have not disagreed with you!!!!! I made a chart of bars/second vs RPM. If the XRR is held at ~4000rpm, the boost increases linearly at 0.3Bar per second. (I messed up my chart a little, so just multiply the bar/s values in my chart by 10). At the rev limiter, the boost increases linearly at 0.7Bar/s.

EDIT: I am going to redo this, except do it in neutral and start off with the engine off, and turn on the ignition while full throttle. That way there won't be the spike in the beginning, I don't think.

Quote from morpha :

....the turbo pressure would increase in exactly the same time at the same engine RPM as it would in 6th....

Quote from morpha :

And once again you missed my point, I clearly stated it will increase linearly in any gear, full throttle And if you scroll back up you'll see I was the first one to say that it depends solely on the RPM

At 5000 rpm with the throttle fully opened, the turbo pressure will increase EXACTLY IN THE SAME WAY in ALL GEARS, that is what I said the whole time.

Where did I not say "at the same RPM"?

Quote from morpha :

Where did I not say "at the same RPM"?

Right here is what caused me to disagree with you:

Quote from morpha :

For me, the turbo pressure increases completely linearly, any gear, as long as I'm flooring it.

You did NOT say "at the same RPM" after that!

By the way, let me use this post to upload a better chart of boost increase vs rpm...

Well that post was followed by the following one:

Quote from morpha :

Well I was wrong about the full throttle thing, there actually is some pressure starting from 50% throttle. However, the XRR's turbo boosts up to 1.7 bar at about 5k rpm, any gear, full throttle.

Anyway, enough useless text and charts proving facts we already knew for me, I'm out

Quote from morpha :

Well that post was followed by the following one:

Anyway, enough useless text and charts proving facts we already knew for me, I'm out

Well the only thing you said that I disagreed with is the linear part.

Let's throw a spanner in the works - a turbo's ability to generate boost has more to do with exhaust gas temperature than flow rate.

Quote from tristancliffe :

Let's throw a spanner in the works - a turbo's ability to generate boost has more to do with exhaust gas temperature than flow rate.

Well after realizing that I have no idea about how real turbochargers generate boost, I decided to just try to see how the turbochargers in LFS do so.

Quote from tristancliffe :

Let's throw a spanner in the works - a turbo's ability to generate boost has more to do with exhaust gas temperature than flow rate.

Let's throw a second one - a turbo's ability to generate boost has more to do with the revs and size of the exhaust turbine than flow rate

Quote from Zen321 :

Let's throw a second one - a turbo's ability to generate boost has more to do with the revs and size of the exhaust turbine than flow rate

Well the displacement of the engine also matters as much as the revs do.

Judas Preist.

Wow.

Leave it Jeff, it's not worth it!

Ok Tristan I'm not going there overall, but I have to point out that:

A) When you go WoT, last time I checked you should be at or near 0 vacuum very quickly (almost instantly at idle, not quite so at higher RPM) due to equalization when you slam the throttle open.

B) Why the hell would a blowoff valve always be open under vacuum; you would be taking in unfiltered ambient air almost all the time, which would be silly. The turbocharger would also never be able to pressurize the manifold if it didn't close until it was under pressure - quite the conundrum! :doh:

For the most part, stock turbos don't have blow off valves, they have recirculating valves, so it doesn't matter if its open or not, it's always filtered.

But a performance turbo usualy has a blow off valve, which in most cases has it's own filter to prevent dust from being sucked in at idle. But some people like to hear that noise made popular by a particular movie, and run a blow off valve with no filter without realizing what they are risking.

When you go WOT from a stand still in gear the vacuum will drop almost instantly and boost can then build as soon as the turbo spools, because the engine has a load on it and will not just rev up as fast as it can.

If you go WOT with the car out of gear, the engine has no load and will then wind up as fast as it can, usualy keeping up vacuum. This causes the valve to either only close partialy, or not at all. Which means that even though the turbo is spooling up, the boost is lost through the valve.


So the turbos in LFS behave quite realisticaly in that sence, if you just WOT out of gear the engine will keep up with the vacuum drop, and it won't drop enough to close the valve.

I could provide a diagram of the system, but it would take some time to make. It would more than likey need to be animated to show without load, and with load.

Ok, well everyone has to look stupid sometimes. For years I always assumed the BoV/Recirc was soley pressure activated. Turns out after some quick research that it's a combination of post-throttle vac and pre-throttle pressure that activates it, not just one or the other.

There's plenty of cars BTW that can get to good amounts of positive manifold pressure in neutral. There's a video floating around here that I uploaded a few years ago where 12lbs or so is acheived just by reving the engine; it just depends on the system in question. That phenomenon is just about efficiency range / compressor map on the turbocharger vs engine characterisitics.

This also means I can almost gaurantee that there are other problems with the modelling in LFS based on something Scawen said to me about it in December. Pardon me while I dig it up.

Well, it realy depends on how quickly the engine responds to throttle position, if it responds slower than you can get positive manifold pressure in nutral. but on a car that responds very quickly the engine will keep up and you will only get a small drop in vacuum.

If you put a turbo on a formula 1 engine or an engine with similar responce time I'm positive you won't get boost in nutral. The turbo will spool, theres no question about that, but the valve won't close bacause of vacuum.

Quote from Ball Bearing Turbo :

Ok, well everyone has to look stupid sometimes.

Some people more often then others.
>/me feels stupid most of the time<
Technically, everyone in this thread is spamming, because this thread is about "Turbo chergers". Everyone is discussing turbochargers, when they should be discussing Turbo chergers!!!!

Meh. I'm just excited that BBT is back doin what he does best.
I'm going to learn alot from this thread.

P.S. so im not the onlyone who realises the sluggishness(?) of the XRT's motor? Thought it was just me.

this is a extreamly dumb thread if u guys dont know how a turbo works corectly dont argue that ur right.

i dont fully understand turbo's but they dont all work the same due to differnt boost controlers wastegates and even the way it dumps the gass's can cause differnt boost curve's

shit AR ratio's of the exhaust wheel and compresser wheel alter the lienairty of the turbo's boost curve allso

yes the turbo's in LFS are WRONG!

i drive a car that can hit full boost 17psi at 2600 RPM in 3rd and 4th if u floor it from 1000 RPM and in 2nd it gets to 15PSI at 2500 RMP befor the wheels spin and it Drops down to 12 PSI when spinning

BTW it holds the boost untill 5000 RPM then drops off 2 psi befor hiting the 6500 LIMITER!

and i can go from -20 vacume to -2 vacume free reving the engine

Quote from MAD3.0LT :

this is a extreamly dumb thread if u guys dont know how a turbo works corectly dont argue that ur right.

But isn't that what you are doing by making that post? Seems a little hypocritical to me...

Quote from wheel4hummer :

But isn't that what you are doing by making that post? Seems a little hypocritical to me...

no if u read correctly im not argueing im stating what i have seen and im not saying i understand how they work i merly stated that i have seen ALOT of differnt things. but yer a little hyporcritical from ur point of view.