How superior are turbocharged engines compaired to NA engines in sportscar racing?

[chernaudi]

I'll start with the Porsche 936, the first turbo car to win LM overall. It used a 2.14 liter turbo boxer 6 derived from the Porsche 911 Carrera RSR and its 935 derivitive. This won LM in '76, and '77. A 935(the only actual rear engined car to win LM overall) won in '79. And these cars ran most against cars with 3.0 Liter Ford Cosworth DFV V8s, as well as Renualt Alpines.

The Alpines, however usually used 2.0L turbo V6s, and one won LM in '78.

And now I'll fast forward to 2000 to present. The Audi R8 used a 3.6L twin turbo V8, and the Bentley Speed 8 ultimately used a 4.0L version of this engine. And then there's the now famous/infamous(depending on how you look at it) Audi R10 TDI, which used a 5.5L turbodiesel V12.

The diesel engined cars aside( which in NA form could get better fuel mileage anyways-the nature of the beast), turbo cars seem to have an advantage over NA cars. I think that it's because turbo cars make the same power and torque that NA cars do, but with a much smaller engine.

I'll stage a couple of examples:

Audi R8: engine: 3.6 liter DOHC twin turbo V8 with FSI direct injection.

Horsepower: 620bhp@ 6250 rpm

Torque: 516ft/lbs@ about 4700 rpm

Panoz LMP1: engine: 6 liter OHV NA V8 with port fuel injection.

Horsepower: 620@ 7000 rpm

Torque: 540@ 6800rpm

Judd 5.0 V10: 5.0 V10 DOHC, port injection

HP: 620@ 7800 rpm

Torque: 445 ftlbs@ 6500 rpm

So, are turbo engines superior due to being small in capcaity, but making the same power/torque at the same rpm range as a larger engine, and getting better fuel economy? Or are there other reasons?

[cybersdorf]

Originally Posted by chernaudi

So, are turbo engines superior due to being small in capcaity, but making the same power/torque at the same rpm range as a larger engine, and getting better fuel economy? Or are there other reasons?

The regulations. If they favour N/A engines then everyone will build a N/A engine. Currently, they favour turbos.

[vorsprung]

It's all about the rules.

Originally Posted by cybersdorf

The regulations. If they favour N/A engines then everyone will build a N/A engine. Currently, they favour turbos.

Porsche thought N/A engine was better when they were devoloping LMP in 99-00.

[Bob Riebe]

Originally Posted by chernaudi

I'll start with the Porsche 936, the first turbo car to win LM overall. It used a 2.14 liter turbo boxer 6 derived from the Porsche 911 Carrera RSR and its 935 derivitive. This won LM in '76, and '77. A 935(the only actual rear engined car to win LM overall) won in '79. And these cars ran most against cars with 3.0 Liter Ford Cosworth DFV V8s, as well as Renualt Alpines.

The Alpines, however usually used 2.0L turbo V6s, and one won LM in '78.

And now I'll fast forward to 2000 to present. The Audi R8 used a 3.6L twin turbo V8, and the Bentley Speed 8 ultimately used a 4.0L version of this engine. And then there's the now famous/infamous(depending on how you look at it) Audi R10 TDI, which used a 5.5L turbodiesel V12.

The diesel engined cars aside( which in NA form could get better fuel mileage anyways-the nature of the beast), turbo cars seem to have an advantage over NA cars. I think that it's because turbo cars make the same power and torque that NA cars do, but with a much smaller engine.

I'll stage a couple of examples:

Audi R8: engine: 3.6 liter DOHC twin turbo V8 with FSI direct injection.

Horsepower: 620bhp@ 6250 rpm

Torque: 516ft/lbs@ about 4700 rpm

Panoz LMP1: engine: 6 liter OHV NA V8 with port fuel injection.

Horsepower: 620@ 7000 rpm

Torque: 540@ 6800rpm

Judd 5.0 V10: 5.0 V10 DOHC, port injection

HP: 620@ 7800 rpm

Torque: 445 ftlbs@ 6500 rpm

So, are turbo engines superior due to being small in capcaity, but making the same power/torque at the same rpm range as a larger engine, and getting better fuel economy? Or are there other reasons?

You are speaking of restricted racing in which any engine is only as good as the person writing the rules allows it to be.
It has little to do with any engine configuration being superior or inferior.
If the rules were tweaked further, a flat-head Ford could win week-in, week-out.
A blown engine: is how a small engine reaches levels that it cannot in atmospheric form, so a super charger is attached.
How good an engine performs NA, any engine, shows how good that design is.
How well it responds to being blown, show how strong it is.
Bob
PPS--When Porsche started using blown engines on the 911, they lost the fuel advantage they had relied on before.

[JHamilton]

Kind of a loaded question, huh? In addition to what the fellas above said, I'll add this...

It is impossible to make a judgement between any engines without seeing the entire power curve for each one. Unfortunately, we don't get to see that good stuff.

I believe the Audi is the most reliable, bullet proof engine you listed there. However, if sound and character count for anything I'll take one of the two NA ones listed.

[Randy]

As has been already stated its largely down to regulations. My view is generally that NA power is more usable than turbo power but with modern electronics this is becoming less of an issue. Under the current LMP regs I would favour a turbo engine because you get better power across the rev range whilst running restrictors and you can package a smaller engine. The big downside of turbos is complexity and heat. Remember you have to keep all those extra electronic and mechanical systems running 100% and you also have to package intercoolers and airflow to the turbos.

[Hammerdown]

I would imagine a turbo engine is theoretically more efficient than a NA but, as Bob says, it depends on your criteria. They are smaller and lighter than an equivalent NA (think 2-litre, four-cylinder AER up against a 3.4-litre V8 Judd/Zytek/Porsche/Accura etc) and should give a better weight distribution, lower C-of-G etc, but are more complex installations.

Think of how they were used in F1 back in the day, when you had 1.5 litre fours producing 1200bhp! You would have had to use a BIG NA engine to get that kind of power.

Personally I don't like them. Mainly because of the noise issue, but also because they seem to me to be 'artificial'. I'd much rather have an NA, whether it's a high-revving four or a big grumbly V8, or anything in-between!

[AU N EGL]

I believe it is differenty ways of achiving the same or nearly the same results.

Unforuntily your listing of the Audi engine was UNrestricted. Restricted as in current race confiurations is about 520 bhp not 620.

The Panoz 6 liter Ford V8 you list is restricted race trim 620 bhp not the unrestricted 700 bhp.

The Judd engine I do not know about.

And the Corvette LS7.r 7 liter V8 is restricted race trim apporx 580 bhp not the 900 bhp unrestriced.

That being said, yes tubo charged engines do get into the power band quicker as there is greater airflow from the turbos.

If the ACO did not have the air restrictors and the lap time constrictions for each class, which cars would be the fastest? assuming same engine size.

This is just my guess

LMP1 cars would still be the quickest lap times, with LMP2 cars right behind and not by much. Not taking into account the new Porsche spyder.

Staight line speed, GT1 cars with the big engines.

A big part of the engine size and air restrictors was to keep saftey in mind. Rember the speeds on the Mulsanne straight before the esses were added?

Trap speeds: http://www.mulsannescorner.com/maxspeed.htm

[JAG]

If it wasn't for the restrictors we see today there wouldn't be any atmo engine in LMP1.

During the later days of Group C1 the Jaguar V12, Cosworths and US V8's were uncompetitive against turbo power.

Even today I'd take a turbo engine over atmo in P1, they seem to be more reliable, fuel efficient and flexable to altering track conditions.

[JAG]

Originally Posted by AU N EGL

I believe it is differenty ways of achiving the same or nearly the same results.

Unforuntily your listing of the Audi engine was UNrestricted. Restricted as in current race confiurations is about 520 bhp not 620.

The Panoz 6 liter Ford V8 you list is restricted race trim 620 bhp not the unrestricted 700 bhp.

The Judd engine I do not know about.

And the Corvette LS7.r 7 liter V8 is restricted race trim apporx 580 bhp not the 900 bhp unrestriced.

That being said, yes tubo charged engines do get into the power band quicker as there is greater airflow from the turbos.

If the ACO did not have the air restrictors and the lap time constrictions for each class, which cars would be the fastest? assuming same engine size.

This is just my guess

LMP1 cars would still be the quickest lap times, with LMP2 cars right behind and not by much. Not taking into account the new Porsche spyder.

Staight line speed, GT1 cars with the big engines.

A big part of the engine size and air restrictors was to keep saftey in mind. Rember the speeds on the Mulsanne straight before the esses were added?

Trap speeds: http://www.mulsannescorner.com/maxspeed.htm

In 2002 the Audi R8 reportedly had 670bhp. The restrictors of the time were the same size current P1's use.

The current Judd should be around 640-650bhp, an AER/Cosworth turbo 650bhp+.

An unrestricted R8 engine would put out 1000bhp+, just like the Nissan an Toyota Group C engines in qualifying spec, 15 years ago!

[AU N EGL]

atmo? I guess we call them NA or natural asperated.

Of course a turbo will force more air into and pull more exhaust out of the cylinders at a much quicker rate, then naturally asperated.

[chernaudi]

The specs that I gave were as close to the 2002/post 2004 LMP1 specs as I could find. It also seems to me that the R8 engine is a little heavy(380-390lbs) for what it's used for. I think that it may have something to do with Audi'd decision to use a flat plane crankshaft in their engines. Maybe that's why there are so many atmo engines in use nowadays(durability/reliability).

[HORNDAWG]

This is an apples and oranges question. It all depends on rules and courses! Why not add Variable pitch vanes and superchargers into the mix? Prototypes are the only Sports Cars?? What parameters are you using to determine which is the best application and why? Most Sports Car racing series are based on factory cars(sort of). Do all of the manufacturers offer turbo cars???

L.P.

[chewymonster]

I am sure that the R8 engine without any restrictions at all will make a lot more than 620 horsepower. Of course it will reach its limit a bit sooner if it has to run that unrestricted engine for 24 hours in a row.

I also don't think the Corvette engine would make 900 hp if it had to run 24 hours straight (as it would have to rev to around 8,000+ for that, and I don't think it would last 24 hours at that RPM range)

[JAG]

Originally Posted by AU N EGL

atmo? I guess we call them NA or natural asperated.

I always use that term as the 3.5l Group C cars (905, XJR-14 etc.) were always described as atmo cars at Le Mans and in the World Championship.

[AU N EGL]

Originally Posted by chewymonster

I

I also don't think the Corvette engine would make 900 hp if it had to run 24 hours straight (as it would have to rev to around 8,000+ for that, and I don't think it would last 24 hours at that RPM range)

Most likely you are correct. Katech, the engine builder estimated 900 bhp without air restrictions. That is estimated, as the enigne was designed, built and tuned for +/-600 BHP and +/-650 TQ. With air restictors and tuning the numbers came down too 580-585bhp and 640 tq.

[Bob Riebe]

Originally Posted by chewymonster

I am sure that the R8 engine without any restrictions at all will make a lot more than 620 horsepower. Of course it will reach its limit a bit sooner if it has to run that unrestricted engine for 24 hours in a row.

I also don't think the Corvette engine would make 900 hp if it had to run 24 hours straight (as it would have to rev to around 8,000+ for that, and I don't think it would last 24 hours at that RPM range)

For nine hundred horse power, the engine would be in the nine thousand rpm range.(Maybe touching the tens.)
As Trans-Am small blocks were in the seven thousand range for 24 hours, 38 years ago, I have little doubt they could use the eight thousand rpm range for 24 hours nowadays without any problem.
The engine would be detuned just as they have been doing for the past forty plus years, for the 24 hour races so I would guess peak horse power would not be above high seven hundred something.