It's the new turbo engines and clever batteries which make racecars much ore efficient - are you sure?

If you listen to the FIA, the ACO and many commentators the latest cars are 20-30% more efficient due to the clever new F1 turbo engines and clever batteries.

I'm no powertrain expert let alone a hybrid expert but comments by the chief engineer of the Toyota TS040 2014 LMP car have made me wonder if the above is really true?

Comments in the article.

"Compared to last year we are burning 25-30% less fuel"

"A turbocharged petrol engine is not so efficient"

“We don’t use a MGU-H"

"The cars are narrower than last year"

“Much of the (width) reduction has come from the tyres"

“The new driving style that requires drivers to coast down the second half of the straight"

“on a Le Mans lap 95% is powered by the engine with the MGU responsible for the remaining 5%"

Now the Toyota seems to be the quickest car under the new regs and has up to 1,000 bhp available - 520 from the IC engine and 480 bhp from the front electric motor. BUT if you look at the comments the 25% fuel saving seems to come from

1) Making the existing NA 4.7 litre V-8 more efficient

2) Making the car and tyres narrower for less drag

3) Teaching the driver not to drive flat out al the time.

I may be very, very dumb but if the MGU gives only 5% contribution it ought to be 1) to 3) above which is responsible for most of the 25% fuel gain.

Any thoughts please?

3.7L* http://www.toyotahyb...h-ts040-hybrid/

Im very interested in hearing more on that claim myself. A link to your source would be helpfull Mariner. Surely some light turbo boost would only be a good thing..

Mats , the comments come from an article on the Toyota  TS040  in Racecar Enginering  volume 24 number 6.

I think that copy has been out for about 3 months - they never put dates on them!

Edited by mariner, 07 July 2014 - 13:27.

No, turbocharging engines that operate around stoich and at areasonable CR is not usually much of an improvement efficiency wise. The mpg gains you see from doing so are only measurable if you fit a smaller displacement engine at the same time. The reason is obvious if you think about it for a while, I've forgotten.

Talking about F1 now.

Leaving aside the hybrid features, it seems the heat engine (ICE plus recovery turbine) is about 40% efficient (more than 40% according to MB). 40% is a massive improvement and is mainly due to two things.

 1. Turbo-compounding. The turbine recovers some of the waste heat in the exhaust and makes it available as additional power.

 2. Lean operation. Not confirmed, but in my opinion the engines are operating at lambda 1.2 and above. This is the area where any SI engine produces it's highest thermal efficiency (BSFC if you prefer). The FIA used to limit power output by limiting airflow to the engine (displacement, rpm, boost etc limits). Under an airflow limited formula, the engine tuner selects the fuel quantity that produces most power from the air available and that has always been lambda 0.8 - 0.9 i.e. 10% - 20% excess fuel ensuring combustion of the greatest fraction of the available (limited) oxygen. The reverse is now the case. The FIA limits the fuel flow rate to 100 kg/hr and the tuner has more airflow available than needed to consume that fuel (1.6 turbo, 15,000 rpm, unlimited boost). So the tuner can now set the airflow to extract the most energy/power from the fuel available.