Turbo vs Atmospheric engine race track

[hsg]

Lag is an ever-present issue with turbo race cars, F1 just has a big electric motor to spool it up and fill in the lower RPM power gap. There are inherent advantages and disadvantages to both, turbos come with intercoolers which increase weight and cooling drag, that weight is also higher up which is a detriment to laptime. If you go back to the 80s when turbo cars ran alongside NA cars the pattern would generally be - NA faster in corners (less weight, better COG, easier packaging, easier on tyres) with the turbos blasting past on the straights (more power overcoming the losses).

I'm not sure I agree with your assertion that turbo engines are cheaper/lighter/more durable. It'd be cheaper for F1 to go with a NA 2.5-3li V8 revving to 12-15k made by Cowsorth/AER/Gibson/Judd or someone.

If both cars have same mass and engines same peak power, which car will do better lap time?

[gruntguru]

Lag is an ever-present issue with turbo race cars, F1 just has a big electric motor to spool it up and fill in the lower RPM power gap. There are inherent advantages and disadvantages to both, turbos come with intercoolers which increase weight and cooling drag, that weight is also higher up which is a detriment to laptime. If you go back to the 80s when turbo cars ran alongside NA cars the pattern would generally be - NA faster in corners (less weight, better COG, easier packaging, easier on tyres) with the turbos blasting past on the straights (more power overcoming the losses).

I'm not sure I agree with your assertion that turbo engines are cheaper/lighter/more durable. It'd be cheaper for F1 to go with a NA 2.5-3li V8 revving to 12-15k made by Cowsorth/AER/Gibson/Judd or someone.

If both cars have same mass and engines same peak power, which car will do better lap time?

The turbo engine will typically have a wider band of near-peak power so will typically do the better lap time. Width of power band should be expressed as: (usable rpm band)/(peak power rpm).

So an engine that is usable (say within 10% of peak power) from 4,000 - 6,000 with peak power at 5,000 has a width of 2,000/5,000 = 0.4 or 40%.

This would outperform an engine that is usable from 8,500 - 11,500 with peak power at 10,000 - a width of 3,000/10,000 = 0.3 or 30%.

The only detriment to lap time is lag which - if bad enough - can negate the above advantage.

[hsg]

Lag is an ever-present issue with turbo race cars, F1 just has a big electric motor to spool it up and fill in the lower RPM power gap. There are inherent advantages and disadvantages to both, turbos come with intercoolers which increase weight and cooling drag, that weight is also higher up which is a detriment to laptime. If you go back to the 80s when turbo cars ran alongside NA cars the pattern would generally be - NA faster in corners (less weight, better COG, easier packaging, easier on tyres) with the turbos blasting past on the straights (more power overcoming the losses).

I'm not sure I agree with your assertion that turbo engines are cheaper/lighter/more durable. It'd be cheaper for F1 to go with a NA 2.5-3li V8 revving to 12-15k made by Cowsorth/AER/Gibson/Judd or someone.

If both cars have same mass and engines same peak power, which car will do better lap time?

The turbo engine will typically have a wider band of near-peak power so will typically do the better lap time. Width of power band should be expressed as: (usable rpm band)/(peak power rpm).

So an engine that is usable (say within 10% of peak power) from 4,000 - 6,000 with peak power at 5,000 has a width of 2,000/5,000 = 0.4 or 40%.

This would outperform an engine that is usable from 8,500 - 11,500 with peak power at 10,000 - a width of 3,000/10,000 = 0.3 or 30%.

The only detriment to lap time is lag which - if bad enough - can negate the above advantage.

So turbo has flatter power curve of usable band?

I find this for Power Band Width=RPM at Peak Power−RPM at Peak Torque..

[Billzilla]

Isolated anecdote - A very good engine builder I know well builds engines for the local MX-5 series. He's found that for the turbo engines (in the same car) to beat the n/a ones. they need to have 20% - 50% more power.

[hsg]

Isolated anecdote - A very good engine builder I know well builds engines for the local MX-5 series. He's found that for the turbo engines (in the same car) to beat the n/a ones. they need to have 20% - 50% more power.

What is reason for that?

Here we can see that turbo operate in band 5000-7000RPM and NA engine in 6500-9000RPM.
NA engine use wither rpm band, but is this bad ,because ICE engine has only at one RPM max power, so bigger the band, more you drive car at lower power?



https://www.youtube.com/watch?v=s2Jfqc5smDg

https://www.youtube.com/watch?v=94-GofRYHaI

[bananapeel23]

Lag is an ever-present issue with turbo race cars, F1 just has a big electric motor to spool it up and fill in the lower RPM power gap. There are inherent advantages and disadvantages to both, turbos come with intercoolers which increase weight and cooling drag, that weight is also higher up which is a detriment to laptime. If you go back to the 80s when turbo cars ran alongside NA cars the pattern would generally be - NA faster in corners (less weight, better COG, easier packaging, easier on tyres) with the turbos blasting past on the straights (more power overcoming the losses).

I'm not sure I agree with your assertion that turbo engines are cheaper/lighter/more durable. It'd be cheaper for F1 to go with a NA 2.5-3li V8 revving to 12-15k made by Cowsorth/AER/Gibson/Judd or someone.

If both cars have same mass and engines same peak power, which car will do better lap time?

Depends on the track. The turbo engine (assuming it has an MGU-H) will do better at low speed because it gets more airflow at low speed due to the forced induction.

On a track like Las Vegas or Monza the NA engine would have the advantage of being more inefficient and burning off more of its fuel, while getting plenty of air all the way around the lap due to the high speed.

If we're going with a traditional turbo engine with no anti-lag, the NA engine would win every time, except maybe at high altitude tracks like Mexico, where the forced induction would again be a huge advantage.

Basically the more the wastegate has to be open, the worse the turbo becomes.

[hsg]

Lag is an ever-present issue with turbo race cars, F1 just has a big electric motor to spool it up and fill in the lower RPM power gap. There are inherent advantages and disadvantages to both, turbos come with intercoolers which increase weight and cooling drag, that weight is also higher up which is a detriment to laptime. If you go back to the 80s when turbo cars ran alongside NA cars the pattern would generally be - NA faster in corners (less weight, better COG, easier packaging, easier on tyres) with the turbos blasting past on the straights (more power overcoming the losses).

I'm not sure I agree with your assertion that turbo engines are cheaper/lighter/more durable. It'd be cheaper for F1 to go with a NA 2.5-3li V8 revving to 12-15k made by Cowsorth/AER/Gibson/Judd or someone.

If both cars have same mass and engines same peak power, which car will do better lap time?

Depends on the track. The turbo engine (assuming it has an MGU-H) will do better at low speed because it gets more airflow at low speed due to the forced induction.

On a track like Las Vegas or Monza the NA engine would have the advantage of being more inefficient and burning off more of its fuel, while getting plenty of air all the way around the lap due to the high speed.

If we're going with a traditional turbo engine with no anti-lag, the NA engine would win every time, except maybe at high altitude tracks like Mexico, where the forced induction would again be a huge advantage.

Basically the more the wastegate has to be open, the worse the turbo becomes.

On slow track, you can put short gears so engine will be all the time in optimal power band.
Why do you think that using more fuel is benefit?

[bananapeel23]

If both cars have same mass and engines same peak power, which car will do better lap time?

Depends on the track. The turbo engine (assuming it has an MGU-H) will do better at low speed because it gets more airflow at low speed due to the forced induction.

On a track like Las Vegas or Monza the NA engine would have the advantage of being more inefficient and burning off more of its fuel, while getting plenty of air all the way around the lap due to the high speed.

If we're going with a traditional turbo engine with no anti-lag, the NA engine would win every time, except maybe at high altitude tracks like Mexico, where the forced induction would again be a huge advantage.

Basically the more the wastegate has to be open, the worse the turbo becomes.

On slow track, you can put short gears so engine will be all the time in optimal power band.
Why do you think that using more fuel is benefit?

If you burn fuel off faster you weigh less.

[hsg]

Depends on the track. The turbo engine (assuming it has an MGU-H) will do better at low speed because it gets more airflow at low speed due to the forced induction.

On a track like Las Vegas or Monza the NA engine would have the advantage of being more inefficient and burning off more of its fuel, while getting plenty of air all the way around the lap due to the high speed.

If we're going with a traditional turbo engine with no anti-lag, the NA engine would win every time, except maybe at high altitude tracks like Mexico, where the forced induction would again be a huge advantage.

Basically the more the wastegate has to be open, the worse the turbo becomes.

On slow track, you can put short gears so engine will be all the time in optimal power band.
Why do you think that using more fuel is benefit?

If you burn fuel off faster you weigh less.

If turbo is more efficient then you can drive with less fuel in tank...

Assumption is power and mass are the same

[bananapeel23]

On slow track, you can put short gears so engine will be all the time in optimal power band.
Why do you think that using more fuel is benefit?

If you burn fuel off faster you weigh less.

If turbo is more efficient then you can drive with less fuel in tank...

Assumption is power and mass are the same

Well yes if you assume mass is the same and fuel doesn't burn off, then it doesn't matter.

[hsg]

If you burn fuel off faster you weigh less.

If turbo is more efficient then you can drive with less fuel in tank...

Assumption is power and mass are the same

Well yes if you assume mass is the same and fuel doesn't burn off, then it doesn't matter.

Turbo and NA engine has different power curve, here is difference.

[JordanMugen]

Lag is an ever-present issue with turbo race cars, F1 just has a big electric motor to spool it up and fill in the lower RPM power gap. There are inherent advantages and disadvantages to both, turbos come with intercoolers which increase weight and cooling drag, that weight is also higher up which is a detriment to laptime. If you go back to the 80s when turbo cars ran alongside NA cars the pattern would generally be - NA faster in corners (less weight, better COG, easier packaging, easier on tyres) with the turbos blasting past on the straights (more power overcoming the losses).

I'm not sure I agree with your assertion that turbo engines are cheaper/lighter/more durable. It'd be cheaper for F1 to go with a NA 2.5-3li V8 revving to 12-15k made by Cowsorth/AER/Gibson/Judd or someone.

If both cars have same mass and engines same peak power, which car will do better lap time?

Why is peak power important?

Surely only cumulate power (work) is important? [Which some people say as "torque wins races", but that shouldn't interpreted as peak torque but rather average torque for a given engine class -- i.e., average power.]

No use having (for example) 225hp @ 9000rpm if that tuning means you lose 10 hp from 6000-8500rpm, the engine with 215hp peak but (average) 10hp more from 6000-8500rpm will almost certainly perform better -- assuming say a 1500cc aspirated engine class.

[Or say it's a 1000cc aspirated class, then 215hp peak @ 13800rpm may outperform 230hp peak @14000rpm, if the first engine is less peaky and makes more power than the second from 8000-12800rpm (assuming rev limiter of say 14200rpm). I.e., what you gain in the last 1400rpm before redline may not be enough to offset what you lose compared to the first car below 12800rpm, having tuned the engine to be super peaky for peak power. AFAIK, such bike engines don't tend to have varioram or VVT.]

Though in some class (those with fixed gear ratios but free inlet runner length), the teams have different inlet runner lengths to move the torque band to suit the characteristics of different circuits -- since obviously the rpm when exiting a corner will be different for different circuits, as gear ratios are not free to choose.

F1 does allow varioram systems (now on turbo engines when it's not as relevant, which is weird!) but not VVT. I guess VVT, VVL and varioram systems can help with having a broader spread of torque when they are permitted.

Sequential turbos were a fad in road cars at one point (e.g., FD RX7 or Subaru Legacy B4) to have two different sized turbos each with a different torque peak, but I take it they are not popular in race cars? How about twincharging (supercharger and turbosupercharger) in race cars, e.g., the VW 1.4 TSI twincharge have a supercahrger to provide boost at low rpm which disengages with a clutch and then the turbocharger provides the boost at medium rpm.

I take it twin scroll turbos with different sized scrolls are popular now, and provide much of the benefit of sequential turbos with far lower complexity?

[JordanMugen]

My logic is that turbo has allways better power/weight ratio

Club racing classes (like 750MC in the UK or Gridlife in the USA) are based on power-to-weight though, that's peak power (on their chassis dyno) divided by weight (on their scales).

So you really just want to have the highest average power. Really both turbo and naturally aspirated engines can be competitive, as the whole point of these rules is to have a wide variety of cars and accommodate all competitors -- Corvettes racing Honda sedans racing BMWs and so on.

The turbo options will have turbo lag, but I guess you can use anti-lag (if it's allowed). I don't see why a turbo option wouldn't be competitive (though I personally don't like turbo engines).

One popular option is to use the cheap and cheerful stock Honda K24 engine from the Honda Accord, and say you are limited to 200hp you'll reach 200hp at 6000rpm (with the normal intake and header) and then just pull the ignition timing (or VVT angle) out of the ECU map from 6000-8000rpm to just hold the engine at 200hp (where it would normally make, say 220hp peak).

The whole idea of these classes is that they should be much more cost effective than, say, a 2000cc class where everyone is spending huge money trying to make the best 2000cc engine possible.

[JordanMugen]

1988 the Turbo motors were both fuel and boost limited, na cars had unlimited fuel. Turbo cars won every single race.

Why turbo won every race,does it have more HP than NA engines?

Of course. The equivalency factor of 2 was not correct. (Simplistic) but with 60 PSI boost (or 75 PSI absolute), then 3000cc atmo engine at ~15psi ambient is roughly equivalent to 600cc turbo engine not 1500cc.

So ~600cc supercharged would have been a more correct equivalence for 3000cc NA.

Granted simple pressure is not the same as mass air flow, and experts may chime in on true equivalence.

[JordanMugen]

Lag is no longer an issue for street or race turbo cars. Properly sized, more efficient turbos have effectively eliminated lag problems even without electrical help.

Nah. E92 M3 over F82 M4, Porsche GT3 over 911 Turbo, Ferrari 458 over 488, Subaru BRZ over Subaru WRX any day of the week in my book! Just more fun.

Trying quickly stabbing and releasing the throttle -- stab, release, repeat. A low inertia NA engine (or electric motor) jerks the vehicle forward instantly in a way a turbocharged engine simply does not.

If you drive "like a normal person" and feed in the throttle, it's no issue, but where's the fun in that?

Sadly some electric cars have artificially dulled throttle response to increase refinement as do some silly ICEs with unresponsive dual mass flywheels. Regardless, BMW enthusiasts describe the scalpel-like response of the eight throttle E92 M3 compared to the molasses like doughy feeling of the F82 M4.

If turbo engines are really more power dense and more controllable, why are they are so unpopular on motorcycles where low weight is at a premium? There have been very few popular production turbocharged motorcycles... If anything this suggests the power is less controllable, particularly on a traction limited one wheel drive vehicle.

Regarding road cars, touting superior performance of turbo engines seems pointless when 500+ hp electric motors are routine. So if ICEs are all about fun -- go for the NA one (or old school turbo engines with "biblical" turbo engine as those were IMO more entertaining than modern turbo engines with artificially limited boost for an artificial flat torque curve that merely simulate larger NA engines (but that sound bad and have doughy throttle response)).