Turbo vs Atmospheric engine race track

[BassVirolla]

I dont think so.

We can compare turbo vs NA engine as two NA engines: car engine vs bike engine.

Car engine has more torque at lower rpm(like turbo).
When you put bike engine in car, in racing car engine will always win because bike engine dont have power at lower rpm, so overall you operate engine at lower average power.

Isnt it?

Turbos, pipes wastegates and intercoolers all have a something called mass.

When the car is the same and the base engine is the same or roughly similar, the turbo car will always be quite heavier. In a car well under a tonne it's not negligible.

Edit: Even more, if the engine is the same and you are doing an engine tuning, to achieve the same power the turbo will probably be the cheapest route. But also the heavier. I hope I've made my point clear.

Your point is far from clear. Do you know what else has mass? ....Fuel, and turbo cars are far more fuel efficient because they don't have to rev as high to reach the same power as NA. 2 cars, same power, 1 turbo, one not, same mass before engine and fuel included, turbo car WILL ALWAYS WIN. Plain and simple.

I never said one engine will be better, or the opposite. Nevertheless, turbo engine also has some drawbacks not negligibles.

I just don't see it so clear cut, at least not without numbers backing each of the options (i.e. average horsepower in rpm usable band, specific fuel consumption, weight of fully assembled powertrain, etc.).

[JordanMugen]

I dont think so.

We can compare turbo vs NA engine as two NA engines: car engine vs bike engine.

Car engine has more torque at lower rpm(like turbo).
When you put bike engine in car, in racing car engine will always win because bike engine dont have power at lower rpm, so overall you operate engine at lower average power.

Isnt it?

No. In a racing car, bikes engines are fast. There is a whole category Formula 1000 with 1000cc bike engines, and (often) they were close to as fast as classic Formula 3 with 2000cc car-based engines. Also, 2400cc Formula One V8 engines were to all intents and purpose motorcycle engines.

Bike (and bike-style Formula 1 engines) lack torque for their power output compared to larger capacity car engines, but in theory you could put a 1000cc 150kW Yamaha R1 engine in a Ford Ranger in place of the 150kw 3.2L turbo-diesel. You would just need to triple the gear ratio, so it would turn 12,000rpm making 150kW instead of 4,000rpm making 150kW -- this way the wheel torque would be the same as ~3x130Nm = ~390 Nm.

The problem (as I understand) is that the clutch of the R1-powered pickup truck would likely go up in a cloud of smoke trying to get a loaded Ford Ranger moving from stationary!

[JordanMugen]

Isnt power curve of turbo always better than NA?

No, absolutely not. Turbos are still peaky to this day, in road vehicles they are just tuned with a torque "cap" to make the torque a straight line and therefore power a straight line -- basically the turbo engine is tuned to artificially simulate a larger NA engine.

A good comparison would be the 6.5L Ferrari V12 compared to the "downsize turbo" 3.9L Ferrari twin-turbo V8.

The torque capping is particularly aggressive on the Ferrari 488, you don't even get to the full capped) value until 5th gear!

Ferrari 488 Torque (i.e. boost) by gear:


If we look at the lower line -- the OEM tune that meets emissions regulations -- there isn't a huge difference in the power curves, both peak at 650 hp (the twin-turbo is perhaps 50-100hp up in places, but that's a big price to pay for losing the V12 sound and throttle response! It's not like the V12 is underpowered -- IMO the V12 will be more enjoyable, and it may still be more effective for racing due to the quicker throttle response exiting corners, depending on whether anti-lag is used on the turbo engine).

Partly this is because of the twin-turbo engine being artificially detuned to both simulate a NA engine (and protect the gearbox) and being detuned to make it drivable so wealthy Ferrari drivers don't go flying off the road with their overpowered 2-wheel-drive car if the boost were to come in hard (the way turbos normally behave when not restricted)!

Ferrari 488 Dyno Graph (3.9L turbo)


Ferrari 812 Dyno Graph (6.5L NA)


The 488 pulls ahead once tuned, as obviously you can just turn up the boost -- whereas "gains" available from tuning the already well optimised V12 are much more minimal.

[JordanMugen]

NA must run at a higher average rpm to produce the same power as a turbo. That is what makes Turbo cars more efficient and durable. Yes, more possible points of failure, but much lower stress put on reciprocating parts within the engine which tend to cause major failures.

Given your name I assume you know, but how you do figure that? Is high rpm on NA, worse than high BMEPs due to lots of boost?

[JordanMugen]

There are more variables such as weight, what kind of car, what kind of engines etc.
In general a turbo engine has the upper hand regarding:
- weight
- usable powerband
- efficiency
- durability
- cost
- flexibility

NA engines have the upper hand in:
- smoothness (no turbo lag)

Electric engines have even smoother delivery, that’s why the combination of a turbo engine with an electric motor is so good.

If turbo engines are better in weight (as well as the other things like "useable powerband"), how come very, very few motorcycles come with turbocharged engines?

Reducing weight is always critical on a motorcycle, yet few production motorcycles are turbocharged!

Heck, some larger torque-orientated motorcycles come with large 1800cc NA engines (be it a 1800cc flat-six, or 1800cc V-Twin (!!!)) apparently in lieu of turbocharging a "downsized" engine!

Is it really only the "smoothness" consideration -- a rider may high-side if boost comes on too unpredictably or aggressively -- or are there other considerations like simplicity and rider enjoyment?

I see "fun" is not one of your criteria! An efficient downsize turbo 100cc single-cylinder might be better by the criteria you mention, but a 250cc inline-four Japanese sportbike revving to 19,000rpm is silly and fun!

[Tommy Cookers]

.... what else has mass? ....Fuel, and turbo cars are far more fuel efficient ......
because they don't have to rev as high to reach the same power as NA.
2 cars, same power, 1 turbo, one not, same mass before engine and fuel included, turbo car WILL ALWAYS WIN. Plain and simple.

for 100 years boosted engines have had lower CR/ER and so lower in-cylinder conversion of heat to work
(no-one has ever charge-cooled to ambient and so avoided this)
similarly turbo-boosted engines have earlier EVO (ie lower in-cylinder ER)

for 50 years the very low boost high rpm 'near-NA' Indycar-type engines have surely been rather impressive
NA and 'near NA' engines benefit most from modern anti-friction and anti-heat coatings

and though with 'tuned-length' induction and exhaust systems ('free supercharging') NA 'pulses' can boost cylinder charging by 24%
with turbocharging some or other of these pulse benefits are unavailable

[BassVirolla]

NA must run at a higher average rpm to produce the same power as a turbo. That is what makes Turbo cars more efficient and durable. Yes, more possible points of failure, but much lower stress put on reciprocating parts within the engine which tend to cause major failures.

Given your name I assume you know, but how you do figure that? Is high rpm on NA, worse than high BMEPs due to lots of boost?

The forces caused by inertia of the reciprocating elements are much bigger than forces caused by pressure and combustion. (The book "Maximum boost" gives some insight in this).

So, we can assume, is more reliable increasing the boost than increasing the rpm.

Nevertheless, you cannot increase the boost without increasing the exhaust manifold pressure, hence increasing temps and lowering efficiency.

Even more, as Tommy Cookers notes, the supercharged engine is thermically less efficient.

Also gets in play the AFR, richer for turbo engines. I much doubt you can complete a race or lap in the same time with less fuel with a turbo engine than with a NA.

Edit: Turbo traditional engine. Not turbo compound as current F1. That's another different beast.