Gordon Murray letter in Evo to Koenigsegg?

[will69camaro]

I understand that with a properly tuned NA engine there wont be ANY transition but i'm saying with a turbo engine you can have the benefits of a forced induction and keep the transition so smooth you wouldn't notice. I know basic laws of thermodynamics as well. I've taken that class recently. What i'm trying to say though is your taking an engine (glorified air pump) and making it easier to breathe, forcing it to breathe more rather, allowing it to "think it's bigger than it really is." (able to displace more air for it's cubic inches than is possible through natural aspiration. I will try to find my sources on that information but i've looked into it thoroughly and recently. With a name like "mr bernoulli" though you make me question myself.

I guess i should have been more specific after reading my post and looking at what i have around here for forced induction and said that the volumetric efficiency can be greater than 100% because the air entering the cylinder is pressurized . My source goes on to say that if the engine is producing vacuum then it's VE is less than 100%, when it neutralizes at vacuum = 0 the VE has reached 100% and boost continues to increase the VE with increasing boost. I'm not saying the F1 should have a turbo by any means i'm just saying that it shouldn't be so quickly discounted...

William

[Mr. Bernoulli]

Volumetric efficiency is a simply the ratio of the volume of the cylinder to the volume of the air going into it. It's kind of an irrelevant measure in this context except to say what we already know - that superchargers (and this includes turbochargers) raise the pressure of the air entering the engine so that more can be squeezed into the cylinders, leading to a bigger bang. This is not the same as engine efficiency.

It is fair to say that turbo technology has come on a fair way since the F1 was concieved but considering GM was designing cars at Brabham with turbos and twice the horsepower of the F1 (from half the capacity) I think its fair to say that he certainly knew what they were capable of...

[will69camaro]

I understand that he knew what they were capable of then, and i'd think if he knew then how they were then he should know how they are now as well. How old is that magazine article? The forced induction used today having higher technology shouldn't be quickly discounted as a "super car" as he seemed to do with the koenigsegg.

Serious question time:
What is engine efficiency anyway? I see Volumetric, Thermal and Mechanical efficiencies and i'm curious as to whether the "engine efficiency" would be based on all three, a combination or if it's derived from a single one.

Thanks,
William

[Mr. Bernoulli]

Originally Posted by will69camaro

Serious question time:
What is engine efficiency anyway? I see Volumetric, Thermal and Mechanical efficiencies and i'm curious as to whether the "engine efficiency" would be based on all three, a combination or if it's derived from a single one.

The efficiency of the engine as a single thermodynamic system would be the energy outputed over the energy inputed (times 100%). That is to say the specific output of the engine divided by the specific energy of the fuel.

Of course an IC engine doesn't really run on petrol or diesel - it runs on air, but the energy has to be added to the system somewhere. Hence the fuel input.

[Mclaren240!]

well im out of my depth hear so fell free to tell me to shut up but from what ive herd the problems with turbos anrt so much lag anymore. I was under the impression that they were out relativly quickly the enging needs to be service far more regually and is far shorter lived i get the feeling that Gorden Murry is asd with the life of the engine before a rebuild and that it would be hard to achive that life with a turbo. Turbo sports cars typicall have bad times between a service dont they? all that extra stree on the enging/seals cant be good in the long rune. The tecnicallities baffle s**t for brains here but i am woundering if there is more to this than simpley power outputs and that engin life might be a factor to or am i just being stupid as ever?

[will69camaro]

Originally Posted by Mr. Bernoulli

The efficiency of the engine as a single thermodynamic system would be the energy outputed over the energy inputed (times 100%). That is to say the specific output of the engine divided by the specific energy of the fuel.

Of course an IC engine doesn't really run on petrol or diesel - it runs on air, but the energy has to be added to the system somewhere. Hence the fuel input.

Ok that sounds kinda familiar from my class. I understand that more fuel is needed to produce the higher power and i guess how i came off is saying that with the same amount of fuel a turbo would make more power than was possible with NA. The turbo supplies the extra air for the oxygen part of the combustion which helps increase power as long as the fuel is there to support it. Turbos (not all forced induction because superchargers aren't the same) make use of lost energy through thermal and kinetic energies of the exhaust gas. Bernoulli please PM me telling me where you went to school and what you went for, I'm very interested in knowing your background (as I am a M.E. student at A&M).

To McLaren240!:
Depending on the turbo car, it doesn't necessarily mean that the life of the car is diminished. That all depends in the setup and the tune...There is more stress on the engine but not any more than a NA engine that makes the same power. You man think you're in too deep or this is over your head but you have to start somewhere and reading and following is the best and easiest way to learn. I still have ALOT to learn about engine systems and vehicle dynamics.

William

[Gustav]

So does anybody have Christians reply?

[ArchangelGTR]

In all respects to everyone regarding the turbo motors. You will have lag with larger turbos.. Plain and simple. I own a twin turbo charged sports car. It does have lag.. but it's sheer fun on the top end. Like a roller coaster ride where it picks up power and speed towards the end of each gear. If it doesn't have lag the turbos are too small to build large horsepower. From my research about 3 years ago, Aerodyne Research has a Variable Area Turbo Nozzle designed to change inlet speeds to reduce the turbo lag giving full horsepower from 1800 to 6000 RPMS, but even these aren't designed to go more than 500 HP.

Turbo cars get bad reputations mainly from owners. Turbos require some additional cooling times in which many common owners don't give them, ie shutting down the motor after a hot run before the turbos have had a chance to cool down causing the oil to coke in them. Hence many aftermarket companies offer turbo timers to let the car cool down and circulate oil through the turbos. It's also best to use synthetic motor oils. A lot of cars in the past (early 90s and older) never recommended. In some owners manuals from the 80s, the factory recommended changing the turbo every 30,000 miles or so. These days with proper routine maintenance, your turbo should last over 120,000 miles.

But let me ask this: What exactly is GM referring to when he talks about how efficient a NA motor is vs. forced induction? Is he also talking about efficiency in its entirety.. packaging, accessability, etc.? No additional plumbing, no additional parts, no additional electronics to control wastegates, no additional heat generated by hot turbos, no intercooler to mount.

And some people do forget that the V12 in the Mac has one more advantage that a normal V12 in any other car doesn't.. no flywheel. The motor revs like a sport bike motor...at your will. It's not just the fact that BMW created a beautiful motor with plenty of torque at the bottom end, but it combined with the transmission and chassis make a relatively efficient package.