- 283
- California
- RoadRocket77
Fix the power bands for the Diesel Prototypes!
- Thread starter maciej908
- 57 comments
- 4,053 views
- 283
- California
- RoadRocket77
Speaking of powerband, they need to model in the correct feel that you get with turbos and 2-stroke engines. the go-carts are the closest they got with the powerband, but it still sucks. the 125 cart doesn't have any gas pedal until you hit 8 grand, that's BS. I have a KX 250 dirt bike that hits the powerband at about a third of what that go-cart needs.
- 1,491
- Brighton
- TheFinners96
Yeah, the diesel sound files they have are garbage too. the 120d sounds like my old murray lawnmower idleing (spelling). and the race cars all sound the same. they kept recycling a lightly tweaked sound that they originally put on the Minolta.
I should add a 120d, regardless of its merits does not sound very nice in real life!
- 4,992
- Nowhere special
- SweetLilPoppet
- SweetLilPoppet
- 1,708
- GTPlanet
- Cosbuster
"Your post mentioned Forza thus you are a fanboy". I don't think I have seen any comments like that on this forum. For all the arguing, I'd like to think we are quite civil.
- 3,070
- Norway
Believe whatever you want.
I never claimed that those were official numbers because I know the level of secrecy involved in this kind of motorsport and I know that finding official numbers isn't so easy.
Tom Kristensen's comments combined with my knowledge of combustion engines tells me 5500 RPM is quite believable.
GTV0819
(Banned)
- 6,084
- Papua New Guinea
RoadRocket77Yeah, the diesel sound files they have are garbage too. the 120d sounds like my old murray lawnmower idleing (spelling). and the race cars all sound the same. they kept recycling a lightly tweaked sound that they originally put on the Minolta.
And the R10 TDI in the game doesn't exactly have the same engine sound as it's real life counterpart, although I like that engine sound but aside from the Minolta, it's also the same engine sound with the NOMAD Diablo and 350Z/Fairlady Z concept race car.
- 8,100
- Guelph, Ontario
A 125 Rotax comes in at about 6500rpm IRL, and that motor has one of the strongest bottom ends of all the TaGs.
Heck, an ICA will rev to almost 20k, where do you think the powerband comes in there?
The reason that you can pull on your dirtbike is because it's a 250 single, even a 350 twin only comes in at 7k, and the redline is at 10. 3 grand to work with is a pretty narrow powerband.
(Hey, something GT did right.
)
- 3,070
- Norway
In real life yes, in Gran Turismo no.
I haven't seen any NA engines with altered curve profiles.
The problem seems to be that any NA tuning is just a torque multiplier throughout the rpm range, which is absurd.
Real life NA tuning is about making the engine rev higher and increasing airflow at high rpm.
I've seen countless tuned engines with higher horsepower and LESS peak torque than the stock motor.
I hope they make the engine tuning more realistic so we don't get NA engines with a specific output of 150 hp/liter and torque figures like a turbo diesel... (See Audi A3 3.2 quattro).
- 1,124
- TexasTyme214
I noticed this too. Race cars at Sarthe in real life use low downforce kits, but that doesn't seem believable when you try it in GT5. With that said, almost every race car has too low of a drag coefficient. The GT-R LM Concept seems to be what I would expect aero to be like on a race car.
- 1,601
- Vienna
- bmw123_
True... Diesels can not spit exhaust flames... the reason is that Diesel combusts under pressure while Petrol only if it gets ignited by a spark plug...
If there is not-burned petrol in the cumbustion chamber, it will not burn, even if cilynders move without throttle, because the spark plug does not ignite... so the petrol gets out of the combustion chamber, touches the hot exhaust and burns...
Diesel will just burn under the pressure of the moving cylinders...
- 369
- West Yorkshire
- DRambo
Please explain for me the point at which the plugs do not spark? Are you saying they don't fire "off throttle"? I thought they would always fire so long as the engine is turning?
I don't know much about this stuff!!!!!
- 1,601
- Vienna
- bmw123_
I would like to explain, but I'm not good enough at English... Can you speak German?
- 13,834
- Adelaide
- Neomone
Isn't that sort of backwards? The petrol won't ignite if the plugs don't spark. The plugs will spark as long as the distributor is feeding them power.
As far as I'm aware in my car (Miata/MX5) at least, the plugs continue to fire at all times barring massive electrical failure, whether on throttle or off. The fuel injectors shut down and stop delivering fuel off throttle, but the spark plugs continue to fire regardless.
- 669
- UK
- Ferrari_Ducati
I've recently tested both Audi R10 and Peugeot 908 by shifting up at <5000rpm and I must admit the acceleration hasn't changed if not became better... This proves most if not all power being present at such revolutions... PD got that right after all... :/
What PD should change however is the timing of the lights on the steering wheel of the Peugeot and the Audi as I was shifting at the time when the first light came on and I doubt that's what happens IRL...
The lights on the steering wheel should come up earlier in the rpm range and not near at the end of the range... Shifting like that also makes the car sound a little more like a diesel LMP and definitely increases drivability out of corners...
What PD should change however is the timing of the lights on the steering wheel of the Peugeot and the Audi as I was shifting at the time when the first light came on and I doubt that's what happens IRL...
The lights on the steering wheel should come up earlier in the rpm range and not near at the end of the range... Shifting like that also makes the car sound a little more like a diesel LMP and definitely increases drivability out of corners...
- 630
- Friesland
- djslofstra
On my 908 HDi FAP '10 I upgraded the turbocharger to a mid rpm turbocharger. It only has around 4 bhp less than with a hig rpm turbocharger and it provides around 200Nm extra torque. So it really accelerates like hell if you keep it in a lower RPM range. It isn't that fast in high rpm so you have to set the gearbox settings quite low to maintain a high top speed.
- 8,704
Diesel simply has a high energy requirement for initiation of combustion. This is a molecular kinetics issue, and is therefore mostly dependent on temperature. The rapid compression in the cylinders gives rise to a rapid increase in temperature with it (because there is not time for heat transfer through the cylinder wall), and it is that temperature rise, not the pressure itself, that causes the Diesel to auto-ignite.
Compounding this high initial energy requirement is a low volatility (it will not vapourise easily) due to the long hydrocarbon chains. That is partly why Diesel injection is at such a high pressure, to yield smaller droplets with an overall larger surface-area to volume ratio, and thus faster rate of evaporation.
What tends to happen is the Diesel combusts in a strange way, almost straight off the liquid (the vapourised portion burns as normal, provided there is enough oxygen). That's how the soot is formed, as a sort of carbon "skeleton" of the droplets, since the heat for its vapourisation and combustion is coming externally from the autoignition in the gas phase. This slow overall burn rate is primarily what limits engine speeds in Diesels (as well as everything being heavier / sturdier because of the higher peak pressures involved).
Soot formation will tend to obscure any flames in the open air, especially from the liquid, but they are there, and there are plenty of examples on YouTube of genuine flaming Diesel exhausts, not just flamethrower kits - although a "particulate filter", as fitted to most modern Diesels (including these LMPs) would tend to act as a flame trap and catalyser (that's what it was designed to do - capture and burn the soot particles), meaning little-to-no fuel or flame reaches the tip. Diesels are also generally run lean so "pockets" of fuel don't really develop in the exhaust.
Petrol / gas has shorter and "lighter" molecules which results in a higher volatility and lower "activation" energy for combustion. That also means the autoignition temperature is lower. Given the speed that it burns, and that the wave front propagates, autoignition is pretty dangerous in a petrol engine, especially at low engine speeds (the waves bounce off the cylinder walls and combine additively in a small area, e.g. burning a hole in the piston).
That's why petrol engines don't operate in the autoignition range (relatively low compression ratios), but instead require a spark to provide the activation energy (temperature). They almost certainly can be run in "compression ignition mode", and several manufacturers have had prototypes for many years. The advantage is that you don't have to rely on the combustion spreading out from the spark plug, instead the whole charge will burn at the same time (assuming it's all at the same temperature and mixture quality). Additionally, lean mixtures are much more workable (the main reason Diesels are so economical) and combustion will generally be much faster, increasing efficiency (more torque and economy).
Google translate seems to cope with that OK, but I can try to clarify if necessary.
- 1,601
- Vienna
- bmw123_
You know, I have no problems understanding English, but writing... yeah, however...
Thanks, Griffith, what you wrote is what I wanted to say 👍
Thanks, Griffith, what you wrote is what I wanted to say 👍
- 8,704
Yeah, I think that's pretty standard with languages (any kind of language), I have the same problem. The same is true of young children, they can understand far more than they can "produce", which might be worth remembering from time to time!
No problem, anyway, although it's possibly a bit off-topic now that I think about it.
Still another point is the sounds. Diesels often have no throttle (at least, not one used as a throttle / regulator; that's done through the fuel injectors instead), so the intake is audible all the time, especially with "InDirect Injection", e.g. pre-chamber, engines (engines without a pre-chamber sometimes use variable flaps / plates to induce swirl in the intake runners, these act like throttle plates to soften the sound.) One particular example would be whatever engine I can hear in some Diesel Peugeots these days; they seem to get very loud on the intake side under all operating conditions after "a few" miles, despite the compressor and intercooler. Petrol engines generally only have loud intakes when the throttle is open. (But GT has never had intake sounds anyway...)
There's also that really high cylinder pressure "spike" radiating through the block as the typical Diesel "clack", that's proportional to the amount of fuel going in. These sounds are needed for the proper Diesel experience.
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