Tadge Juechter backtracking from another lie about Corvette C7 Z06 and C7 Stingray?

Purely rhetorical question since +Tadge Juechter , the chief of the +General Motors Corvette program (still?) has a well established record of making claims that never manage to materialize in real life.  IF one chose to be rude, the statement written above amounts to Juechter lying through his teeth and then attempting to weasle out after being scrutinized by the buyers of the newest generation of Corvette.

The funny part is of course that Juechter's explanations never hold water, outright bullshit as a matter of fact but apparently with enough kool aid, credible enough to be accepted by so called Corvette enthusiasts.  Those lies are there in addition to multiple instances where Juechter misleads the buying public (such as was the case with the "lightweight frame" translating into a considerably heavier car overall).

Among many lies, such as the awesome Nurburgring lap time, C7 Z06 being the better track car and of course, that ever popular "most track capable Corvette ever), there is another one: the flex fuel capability of the newest generation of Corvette.

Ethanol has high anti-knock quality due to its high octane number, and high latent heat of evaporation, which decreases the compressed gas temperature during the compression stroke. In addition to the effect of latent heat of evaporation, the difference of combustion products compared with gasoline further decreases combustion temperature, thereby reducing cooling heat loss. As a result, torque and thermal efficiency increase compared to gasoline. Also, reductions in CO₂, NO_x, and THC are are another benefit of the ethanol based fuel.

Ethanol based fuel like E85 isn’t magic, and there’s some basic science behind why you can expect more power. The real merit of the fuel is in two of its properties: its octane rating and its cooling ability. Octane rating is a measure of a fuel’s ability to withstand detonation or knock. Too much boost or too much ignition advance can lead to detonation on pump fuels and hence the fuel’s octane rating often limits the power we can make. Increase the octane rating though and we can often make more power. The octane rating of E85 is in the region of 105, but when combined with its cooling properties, the actual knock resistance of E85 is much higher than the octane rating would suggest.

E85 also has a very high latent heat of evaporation. In plain English this means that when E85 is injected into the engine, it goes through a phase change from liquid to gas and during this process it absorbs a lot of heat from the intake charge. A colder intake charge is denser and improves power, but also has the effect of making the engine less prone to detonation.

The consequence of the benefits of E85?  More horsepower of course and sustainable power, more importantly.  Now, where E85 really shows its benefits is on the engines using forced induction.  To put it plainly, it allows for higher effective compression and this is exactly what forced induction does.  On normally aspirated engines using spark ignition, the power gain is about 5%.

The major problems with using E85 amount to addressing water absorption, corrosion, alcohol content variations and decrease in stoichiometric air to fuel ratio (from 14.7:1 to 9.8:1).  The last item is of particular value because it requires more robust fuel delivery system and has a direct impact on fuel economy.

Obviously, even though the benefit to the base Corvette Stingray would be neglible, the Z06 would appear to be a natural candidate for the flex fuel/E85 feature since not only would be less prone to detonation, running cooler and producing considerably more power.  Somehow, this is not the case. 

Although Tadge Juechter made his initial remarks regarding flex fuel  feature as the further performance " back in 2013, this is another promise upon which he failed to deliver.

Now, almost TWO YEARS LATER, here is an explanation Tadge Juechter provided to supposedly clarify any doubts and answer the questions:

"Higher octane of E85 is directionally correct in mitigating knock and resulting spark retard. We have recommended the use of racing fuel and octane boost for that very reason in certain situations. The issue with E85 in high performance engines is that there is less total energy per gallon, that is why fuel economy measured in miles per gallon tends to be worse with E85. 

While it is theoretically possible to build a 650Hp engine that uses E85, The challenge is getting enough fuel into the cylinders. The fuel flow rate to the injectors has to be higher in proportion to the energy content of the fuel. That means over 25% more fuel flow. Direct injection engines require very high fuel pressure to operate. At the time the LT4 engine was designed, there was no pump in existence that could manage the combination of flow and pressure. 

It is always possible to try to force a supplier into a unique low-volume solution to meet our needs however it would have been larger, heavier and much more expensive. In addition to the pump on the engine, the pump in the fuel tank would have to be up-sized and possibly even need twin pumps. Routing fuel from the tanks at the back of the car to the engine at the front is always a challenge. Higher volume of fuel flowing requires larger lines that are even more difficult to package. So, for a variety of technical reasons, we elected not to design for E85 on Corvette.

In a nutshell, what Juechter is saying is that higher fuel delivery system requirements made the E85 feature economically infeasible, along with adding more weight to the already heavy cars.  This explanation has to be the most pathetic and bullshit "explanation Tadge Juechter has provided so far and in fact, even more pathetic than his defective oil filter excuse, justifying self obliterating LT1 and LT4 engines.

What is required to enable SI engine to use ethanol based fuel in addition to gasoline based fuel?

The requirements are not very complicated:

Alcohol content sensor, accounting for variation in the real life ethanol contente

Upgraded fuel pumps, injectors and fuel lines

ECU capable of utilizing ethanol being present in the fuel

The use of ethanol rich fuel on its own does not equal to high power gains on its own, what is needed are the ignition advance increase and increase in boost levels.  What is also needed is an engine capable of withstanding these high boost conditions.

Unfortunately, in case of Corvette C7 Z06, there is a big problem and it is not a problem related to the reasons Juechter has stated: the LT4 engine is not robust enough and to make the matter even worse, both the forced induction chosen itself and the choice of the supercharger do not allow for a meaningful boost increase.  Increase in the boost level of the undersized Eton supercharger would most certainly amount to increase in heat generation completely negating the entire attempt.

Now, what is really interesting with Juechter's explanation is the fact he has made the comments regarding the magic ethanol potion AFTER the new line of engines, LT family was already completed.

The increased fuel supply factor is not something that came up as a big surprise, yet somehow, Juechter lied on numerous occasions, leading the ignorant Corvette buyers into believing that flex fuel would be the newest Corvettes "secret weapon", certainly, not a last moment surprise.