Engine This or Thats?

[KielEire]

I am not the most knowledgeable when it comes to mechanics and motors, but I am trying to learn. I am going to go out on a limb here and
guess that there are some of you who really know what is what when it comes to engines. I am also going to guess that I am not the only one trying to learn.

I am going to embarrass myself and ask a series of questions to get some insight as to how to make the best engines I can. I hope others can learn from this too.
Assume I am trying to build bot a race engine and an economical engine.

Torque

Torque Graph.png (415.4 KiB) Viewed 4494 times

Questions:

When it comes to generating power, what is the best?
Is torque what you feel when you pull away from a stoplight? Or is that Horsepower?
If your torque line is flat, is that good? As it means you are not losing power?

Horsepower

Horsepower Graph.png (595.2 KiB) Viewed 4494 times

Questions:

Is smoother always better?
When it bumps (gains 5-15% more in 1000rpm) is it producing more power than if it were to be flat?
When you have a sharp increase (20-30% in 1000rpm) because of turbo, is it always a bad thing?

Turbo

Turbo Graph.png (35.49 KiB) Viewed 4494 times

Questions:

What are the advantages of each one?
What about the disadvantages?
Sharp will obviously give you the most power, but will flat give you a constant boost the whole way through?

Other questions:

What is the Green Line on the bottom of the graph for?
How far over our peak power should the redline be?

Any other advice you can give me or any other new gearhead would be most appreciated!
Thank you!

[Killrob]

When it comes to generating power, what is the best?
Is torque what you feel when you pull away from a stoplight? Or is that Horsepower?
If your torque line is flat, is that good? As it means you are not losing power?

I'll make the start here.

1) There is no right answer here.
2) Technically: None of them.
3) Yes, that is good because it means the engine's power output is predictable. Not because the engine isn't "losing power".

You cannot feel torque or, in fact power, at any point! You can only feel forces. These are the results of the power and torque generated by the engine. Torque is a rather meaningless figure to look at as soon as you have attached a gearbox to the engine that produces it. It is power (work per time) that is important to create and uphold the force that accelerates the car.

[KielEire]

1) There is no right answer here.

Mhm.. Everyone is a winner! There are no wrong answers!
B.S. I know you have the secret formula to the "Perfect" engine. You just want to be the only one and win everything. Dontcha Killrob?

[OCAdam]

1) There is no right answer here.

Mhm.. Everyone is a winner! There are no wrong answers!
B.S. I know you have the secret formula to the "Perfect" engine. You just want to be the only one and win everything. Dontcha Killrob?

I know you're joking but... Check the BRC thread and stage results.

And then you realize how far others have managed to surpass the devs... but then again, look at any speedrun of a game and you'll find plenty of people decimating dev times.

[KielEire]

Killrob came in 8th for S1000, I came in 52nd. He has a lot of knowledge that I don't.
I want.

[Der Bayer]

It only depends on the application. The BRC engines are shit for normal cars (fuel consumption, driveability, costs, MTBF, ...).

The engines posted by KielEire can all be good in some kind of car (as far as I can tell from torque curves only). Except for the first torque curve, this one seems to be heavily exhaust limited.

There is no reason to discuss torque and power curves independently, as they are directly correlated by the engine RPM. In general a flat torque/linear power curve is very easy to drive and does pull well in low RPM while a rising torque curve/steep power curve feels sporty and has more power in the higher RPM. So if you want power, go for high cam profiles, if you want offroad, comfort, ... go for low cam profiles.

If you haven't watched this already, do so.

Regarding Turbo boost: The more is always better for torque/power (in the RPM range you have boost). If the torque/power changes are too big, the car will be undriveable (wheelspin, unexpected power gain, ...).

The green line shows how efficient the engine is and in which RPM range it is most efficient. Basically you need less gears the wider the low range of that curve is to get good fuel consumption. Low cam profiles have their efficient RPM range at low RPM, allowing for high gears when cruising.

The redline depends on your power curve and on your bottom end. Usually it's 500-1000 RPM higher than peak power. But if you hold constant power over a long RPM range, there is no need to cut it off too soon. Maybe it's best to say that you should cut it off as soon as power has dropped by 10-15% compared to peak power. But only if your bottom end can survive that.

Killrob came in 8th for S1000, I came in 52nd. He has a lot of knowledge that I don't.
I want.

Practise is the key. And read my engine designer guide, it's a bit old but the basic message still is true. In the BRC you lost a lot of time because of the too low redline. You could have made the power band a lot wider. And the drivetrain setting was probably a bit too short.

[KielEire]

Thanks so much Der Bayer. It can get a little overwhelming trying to learn all of this. But I know there is a great community here so I am not afraid!

[Killrob]

Getting some good base knowledge of the game with the manual is essential, yes. There is no magic formula there was before (in 2012) and we killed it hard and then ran over it 7 times at least... it was called MinMaxMinMaxMaxMinMinMax - lots of fun to play... not.

Although off-topic, I should add that my BRC cars were themed (towards tameness) and not optimized for performance - devs winning community competitions is kind of a dick move.
I wouldn't have won the BRC 1100, competition was too intense there, but the Super 1000 would at least have been Top 3, probably the win with my non-themed car which I knew to be much faster.

[OCAdam]

Most of the time a good engine is dependent upon what you were intending its application. Say, for example, you were trying to build a motor that was themed towards being able to be stuffed in a car sold to a country that was extremely poor and had only 80 RON gas. Then you'd likely aim for something super cheap to build (and low man hours), keep fuel requirement under 80 RON, and then maybe focus for either economy or power (probably not both though).

I have a feeling what I posted before didn't really come across as a joke. My bad; it was supposed to. Though I'm still fairly certain no dev ever thought LoZ:OoT could be beaten in under 30 minutes... because of a glitch with Gomah's room to get straight to Ganon's castle.

[USDMFTW]

There is not correct way, all of those engines are good, its what application your designing it for, you would not want engine 3 for a eco car etc.

[mer_at]

All three of your torque curves can be good in the right car.
The first one would be good for scenarios where the horsepower is limited. Or if you are only allowed to use few gears.
For a car with 3 gears, i would definately use the first engine, and not the third. If you use 6 gears it would be the other way round.

You should not look at your engine's graphs. You should think what your car will be like, and think what torque graph would fit best for this car.

e.g. my BRC1100 entry.
V8 Turbo with 558hp

Stage1: 369s

and an I4 with 553hp - but 12kg lighter - means better weight distribution

Stage1: 372s

3 seconds lost, just because the powerband of the car is crap now