fuel

[Berzerker]

The compression on both engines is listed as 10.0:1. Is that considered high compression? (I don't know.)

10.0 is usually on the high end, yeah. So it probably tunes it down a bit towards 7-7.5 if it detects lower octane when it would need a tighter ratio to prevent knock.

 

[mldavis2]

The static compression doesn't mean as much today as it used to. My Pontiac GTP (supercharged) was only 9:1 but the supercharger supplied a constant boost pushing it up much farther so the numbers didn't mean much.
On turbocharged engines, it's is essentially the same. The turbocharger forces more air into the cylinders, so a 10:1 engine becomes 11:1 or 12:1 effectively. That in turn requires higher octane fuel to prevent pre-ignition. Higher compression = more heat. (PV=nrT) So the static compression is increased by the turbo boost, and the computer monitors all that and controls the boost along with spark timing to prevent pre-ignition as detected by a knock sensor. It's all quick as a millisecond and very effective, but reducing boost reduces power, hence the need for higher octane. A tank or two of low octane in an emergency won't hurt, but you won't get the power of higher octane. In many parts of the U.S. at higher altitudes, the "premium" octane rating is several points lower than at lower altitudes. This is unfortunate for drivers with superchargers or turbos because we don't need the lower octane fuel at thin air at higher altitudes which cause over-lean conditions on normally aspirated engines. All turbocharged engines that I know of from virtually every manufacturer require higher octane fuel.

 

[Bubbabiker]

10:1 compression ratio is becoming the norm due to the push for greater efficiency and reduced emissions. Some normally aspirated engines are even higher like Mazda's SkyActiv engines. With today's advance engine management systems with direct injection has made it possibly while running on regular pump gas.
Back in the 1980's it was normal to see engines with forced induction at around 8:1 (or lower) compression.

 

[Kazz]

My question is how far beyond 93 octane the system can optimally use. That Ford reference takes me to my old Fiesta ST which could see power gains over and above 93 Octane when using E30. I do wonder if the Stinger can do the same!

 

[Stingin' Away]

The compression on both engines is listed as 10.0:1. Is that considered high compression? (I don't know.)

Manufacturer's lower the compression ratio in FI cars. 10.0:1 is more on the high side of FI engines. For example, The '13 ZR1 has a compression ratio of 9.1:1. The Charger/Challenger Hellcats are 9.3. Basing the Stinger's compression ratio with these, you can see it is a bit higher. Take into account those are superchargers on the ZR1 and Hellcat, not turbos. This may be why the Stinger's is a bit higher.

 

[Bubbabiker]

My question is how far beyond 93 octane the system can optimally use. That Ford reference takes me to my old Fiesta ST which could see power gains over and above 93 Octane when using E30. I do wonder if the Stinger can do the same!

I was wondering the same. Ford does take advantage of higher octanes with increasing timing above the premium fuel. Testing has shown a gain of around 40HP/50TQ with the 3.5L Ecoboost using E30 (95 octane) compared to 87 octane. With pump premium it's 20-25HP gain over 87 octane.

 

[robz32]

My question is how far beyond 93 octane the system can optimally use. That Ford reference takes me to my old Fiesta ST which could see power gains over and above 93 Octane when using E30. I do wonder if the Stinger can do the same!

Any engine is capable of maximizing its performance using any type of fuel, provided the internal engine components can withstand the increase in Hp and torque, and as long as all fuel delivery components are upgraded or compatible (fuel pump, injectors, fuel rails, etc) with the type of fuel being used and the ECU is tuned to make appropriate mixture (air/fuel ratio) so it doesn't blow it self up smithereens.

Now all fuels are not created equal, meaning that some may generate more energy than others, this due to the calorific value of it.

Another point I would like to touch on is that no engine or ECU is capable of changing its compression ratio, the only thing that can be done on the ECU side is pull timing to prevent any detonation/knock or lower boost for forced induction setups (safety boost mode). However we are not far away from seeing the first engine in the world to have the capability of changing it compression ratio, see video below.

[video=youtube;3rn-gZNJBIU]https://www.youtube.com/watch?v=3rn-gZNJBIU[/video]

 

[Kazz]

Agreed, and yes I'm aware that variable compression is on it's way. I still would like to know if the 3.3TT can use E30 to full benefit or not.

 

[mldavis2]

Turbocharged engines do, in effect, vary compression ratio by controlling the waste gate. At idle, compression is effectively whatever the static ratio is. Under boost, the compression ratio effectively increases to pack fuel/air mix into the cylinders.

 

[robz32]

Agreed, and yes I'm aware that variable compression is on it's way. I still would like to know if the 3.3TT can use E30 to full benefit or not.

It could, provided all components are compatible with E30 and all required upgrades to the fuel system are done and the ECU program is cracked.

 

[Kazz]

Again, I understand. But "could" is not proven "does".

 

[Bubbabiker]

Only way to validate it is with dyno runs. Maybe one of the tuners can add E30 to the mix just to see if there is net gain.