Dodge Demon: can switch from Reg to 100+ octane

[wemay]

http://www.motorauthority.com/news/11097...h-of-the-button

From Link above:
"The 2018 Dodge Challenger SRT Demon is less than a week out from its big debut in the Big Apple, and today Dodge has dropped the final bit of info in its long-drawn-out teaser campaign for the car.

It concerns the car’s fuel system. Here, too, will be another production car first: a fuel system designed to run on 100+ high-octane fuel normally reserved for race and dedicated track cars. The high-octane fuel can already be found at many major gas stations but if you prefer regular 91-octane fuel, a button on the dash lets you swap between the two.

Note, the dash switch plus a new powertrain control module (PCM) calibrated for the high-octane fuel need to be installed after delivery. They’re included in the Demon’s crate of go-fast goodies.

The benefit of high-octane fuel is that the engine can run at a higher potency by pumping in more (there’s two fuel pumps in the Demon instead of one in the Hellcat), better burning fuel without the fear of detonation, commonly referred to as engine knock. This is when the air and fuel mix ignites before the piston is fully extended. The Demon is also upgraded with larger fuel injectors using higher rail pressure.

Dodge tells us the high-octane fuel will be required to hit the car’s maximum power rating, estimated to be well over the 707-horsepower rating of the Hellcat.

Mixing high-octane and regular fuel in the tank won’t hurt the Demon’s supercharged 6.2-liter V-8, but the high-octane function won’t activate if the combined fuel octane is too low. Should the octane level drop while on the move, a message in the instrument cluster tells the driver the car will use regular until the engine is shut off and restarted. How does the car know? The PCM monitors the engine knock sensors.

A bonus video will be released tomorrow before Dodge reveals the Demon on Tuesday, April 11. The car makes its formal debut the following day at the 2017 New York auto show."

 

[skyactiv]

I imagine it uses sophisticated knock sensors. Just like there are good and bad microphones, there are good and bad knock sensors.

 

[ARB1977]

I don't see those cats lasting very long with 100+ octane.

 

[HerrStig]

I didn't know 91 octane was "regular". I thought that was 87.

 

[901Memphis]

You can always use race gas concentrate

 

[robertcope]

You can get 100 octane unleaded fuel. For example: http://www.sunocoracefuels.com/fuel/ss-100

Should be fine for the cats, I would think.

 

[slacktide_bitog]

Is the Demon E85-capable? Because E85 has a high octane rating

 

[kschachn]

Originally Posted By: ARB1977
I don't see those cats lasting very long with 100+ octane.


The catalytic converters are agnostic to octane rating, as long as it isn't obtained through tetraethyl lead.

 

[69GTX]

When I was using 100+ octane in my 1968 GTX 4 speed back in 1995 I had to search high and low to find it. Only the local marina carried it. It was either boat yards or airports. I can't imagine it got any easier 20 yrs later.

 

[dave123]

Originally Posted By: 69GTX
When I was using 100+ octane in my 1968 GTX 4 speed back in 1995 I had to search high and low to find it. Only the local marina carried it. It was either boat yards or airports. I can't imagine it got any easier 20 yrs later.
not difficult to get you just have to pony up for it pay to play. VPracing would offer one betting 60+ dollars for 5 gallon pail.

 

[Virtus_Probi]

Originally Posted By: robertcope
You can get 100 octane unleaded fuel. For example: http://www.sunocoracefuels.com/fuel/ss-100

Should be fine for the cats, I would think.


I felt compelled to perform a completely unscientific "experiment" by putting 5 gallons of 100 octane unleaded in with about 10 gallons of 93, there is one station that is not too far from me that carries the race gas. As I expected, my car didn't seem to notice that I paid $50 for 5 gallons of its meal instead of maybe $13.
I'm sure it's hard to find in much of the country, but I'd guess most urban areas have unleaded race gas pumps scattered around here and there.

 

[wemay]

Some Sunoco stations carry it around here. In my early years, we would use one of the stations as a tuner car meet and greet location. We used the race gas at times but like Virtus_Probi exprienced... noticed no change either.

 

[Gasbuggy]

Originally Posted By: Virtus_Probi
Originally Posted By: robertcope
You can get 100 octane unleaded fuel. For example: http://www.sunocoracefuels.com/fuel/ss-100

Should be fine for the cats, I would think.


I felt compelled to perform a completely unscientific "experiment" by putting 5 gallons of 100 octane unleaded in with about 10 gallons of 93, there is one station that is not too far from me that carries the race gas. As I expected, my car didn't seem to notice that I paid $50 for 5 gallons of its meal instead of maybe $13.
I'm sure it's hard to find in much of the country, but I'd guess most urban areas have unleaded race gas pumps scattered around here and there.


If anything your car would make less power. Higher octane is less volatile, less boom, it can only be capitalized on by adding more timing to increase power.

 

[Jarlaxle]

Originally Posted By: 69GTX
When I was using 100+ octane in my 1968 GTX 4 speed back in 1995 I had to search high and low to find it. Only the local marina carried it. It was either boat yards or airports. I can't imagine it got any easier 20 yrs later.


Depends where you are. Offhand, in this area, there are at least three stations selling race gas. (One actual Cam 2, two 100-octane unleaded.) Many tracks also sell race fuel. (I actually saw 100-octane E10 at Thompson Speedway a few years ago.)

 

[Jarlaxle]

Originally Posted By: Gasbuggy
Originally Posted By: Virtus_Probi
Originally Posted By: robertcope
You can get 100 octane unleaded fuel. For example: http://www.sunocoracefuels.com/fuel/ss-100

Should be fine for the cats, I would think.


I felt compelled to perform a completely unscientific "experiment" by putting 5 gallons of 100 octane unleaded in with about 10 gallons of 93, there is one station that is not too far from me that carries the race gas. As I expected, my car didn't seem to notice that I paid $50 for 5 gallons of its meal instead of maybe $13.
I'm sure it's hard to find in much of the country, but I'd guess most urban areas have unleaded race gas pumps scattered around here and there.


If anything your car would make less power. Higher octane is less volatile, less boom, it can only be capitalized on by adding more timing to increase power.


Or adding more boost...

 

[Virtus_Probi]

Originally Posted By: Gasbuggy
Originally Posted By: Virtus_Probi
Originally Posted By: robertcope
You can get 100 octane unleaded fuel. For example: http://www.sunocoracefuels.com/fuel/ss-100

Should be fine for the cats, I would think.


I felt compelled to perform a completely unscientific "experiment" by putting 5 gallons of 100 octane unleaded in with about 10 gallons of 93, there is one station that is not too far from me that carries the race gas. As I expected, my car didn't seem to notice that I paid $50 for 5 gallons of its meal instead of maybe $13.
I'm sure it's hard to find in much of the country, but I'd guess most urban areas have unleaded race gas pumps scattered around here and there.


If anything your car would make less power. Higher octane is less volatile, less boom, it can only be capitalized on by adding more timing to increase power.


I have to disagree with the lower power claim as a general statement, as I worked on the electronics for a knock detection systems for a major US OEM over 20 years ago (jeez, that long??). It was a closed loop system that set the timing such that the car normally knocked ever so lightly, at a level that the driver could not even notice...our customer considered this to be ideal spot to be running the car for power and mileage without risking long term damage. I saw a prototype running on a dyno and it was really cool to see the timing changing on the fly in response to stimuli, and I think they even simulated a step change in octane for us. Almost any modern car is going to have a system as good as this or better.

That said, I have no idea if my car is really capable of taking advantage of octane levels above 93. I doubt Subaru prioritized performance with 100 octane or whatever when they were developing the FA20DIT and it's more than possible that their range of timing adjustments wouldn't be able to accommodate unusually high octane levels.

 

[kschachn]

It's not really timing though, it is compression ratio, right? That is the root determinate if an engine can take advantage of a higher octane rated fuel. Timing only compensates for octane rating since it would be more difficult to adjust compression ratio.

So as long as the compression ratio is high enough (along with a corresponding increased efficiency) you can "successfully" use a higher octane rated fuel. You'll get more power out of a given mass of gasoline.

 

[01rangerxl]

Is this any different from what flex fuel vehicles have been doing for almost 20 years? E85 is supposed to be around 100-105 octane. My 2002 pickup can switch between it and regular 87 octane gas seamlessly, no switch. It doesn't even use a flex fuel sensor.

 

[Gasbuggy]

Originally Posted By: Virtus_Probi
Originally Posted By: Gasbuggy
Originally Posted By: Virtus_Probi
Originally Posted By: robertcope
You can get 100 octane unleaded fuel. For example: http://www.sunocoracefuels.com/fuel/ss-100

Should be fine for the cats, I would think.


I felt compelled to perform a completely unscientific "experiment" by putting 5 gallons of 100 octane unleaded in with about 10 gallons of 93, there is one station that is not too far from me that carries the race gas. As I expected, my car didn't seem to notice that I paid $50 for 5 gallons of its meal instead of maybe $13.
I'm sure it's hard to find in much of the country, but I'd guess most urban areas have unleaded race gas pumps scattered around here and there.


If anything your car would make less power. Higher octane is less volatile, less boom, it can only be capitalized on by adding more timing to increase power.


I have to disagree with the lower power claim as a general statement, as I worked on the electronics for a knock detection systems for a major US OEM over 20 years ago (jeez, that long??). It was a closed loop system that set the timing such that the car normally knocked ever so lightly, at a level that the driver could not even notice...our customer considered this to be ideal spot to be running the car for power and mileage without risking long term damage. I saw a prototype running on a dyno and it was really cool to see the timing changing on the fly in response to stimuli, and I think they even simulated a step change in octane for us. Almost any modern car is going to have a system as good as this or better.

That said, I have no idea if my car is really capable of taking advantage of octane levels above 93. I doubt Subaru prioritized performance with 100 octane or whatever when they were developing the FA20DIT and it's more than possible that their range of timing adjustments wouldn't be able to accommodate unusually high octane levels.


I have a very close friend who is a professional ECU tuner. Your Subaru is not even optimized for 93. It's optimized for 91.

 

[Gasbuggy]

Originally Posted By: kschachn
It's not really timing though, it is compression ratio, right? That is the root determinate if an engine can take advantage of a higher octane rated fuel. Timing only compensates for octane rating since it would be more difficult to adjust compression ratio.

So as long as the compression ratio is high enough (along with a corresponding increased efficiency) you can "successfully" use a higher octane rated fuel. You'll get more power out of a given mass of gasoline.



It's a balance. You can do lots of things to take advantage of more stable fuel. When you take an engine as is and it you give it more octane then you can increase the timing and/or, as someone else said, add boost if that's an option. You could mill heads and add compression.