An interesting power curve

So i was just messing around with engines and then all of a sudden theres this strange power curve change i noticed. Any one else get things like these?

Out of curiosity what’s your cam set at?

Probably your turbo is very small? It seems to run out of boost very quickly. Either that or the game decided to change your intercooler (it does this at certain displacement thresholds) and that changed your boost profile significantly.

Also I see your AFR is 10, you’re not running rich though are you?

His intercooler is still green so its not restricting the flow, and only his compressor is red so I’d guess a small compressor, larger turbine paired with a highish (70-90) cam profile and very large exhaust diameter cause that little up swing to his power band at the redline.

[quote=“strop”]Probably your turbo is very small? It seems to run out of boost very quickly. Either that or the game decided to change your intercooler (it does this at certain displacement thresholds) and that changed your boost profile significantly.

Also I see your AFR is 10, you’re not running rich though are you?[/quote]

not rich but the game flipped out and i had to reinstall do i dont have it anymore

That’s ok, after I saw your last post, I decided I’d boot up the public build and see for myself what was going on.

Took me a few minutes to realise it wasn’t a large turbine, but a high AR ratio that was derestricting flow through the turbine:


Obviously not exact replica of the values earlier, but a close enough demonstration of what really happened. Derestrict the turbine flow too much, and the engine runs rich. Also, while the net effect is very little, raising the boost limit damages the engine, probably because of the pressures running through the compressor not being relieved by the wastegate?

Speaking of undrivable engines…


How on earth…

small turbo that spools quickly then loses power and a high cam to step into after the turbo.

Interestingly enough this was on default settings with a journal bearing turbo but with the boost cranked up to octane limit. Once I selected ball bearings it went to a generic torque curve like any other.

People were whining about not having some constant torque flow.

Well. Our company boss yelled “Sauerkraut”.
He went to do the design by himself.

And we have a very large boat…I mean car engine, with “constant” torque from 1000-5000 RPM.

Because why the hell not?


Lol I see what you did with the boost there.

How big is that turbo?

Compressor 90.0 mm
Turbine 99.0 mm
AR Ratio 1.15
Max boost 1.24 bar

Max boost doesn’t matter at that stage as the setup doesn’t allow the turbo to fully spool.
But hey people will stop whining about not having a flat powerband :stuck_out_tongue:

Well done. You have won. Claim your award.

I think I’ve almost created a 3 litre Turbodiesel… :mrgreen:



Weird how the turbo actually loses boost until it stops producing boost at 5500rpm. Reminds me of a positive displacement supercharger, actually. A badly engineered one, in this case.