Boxer12
Enthusiast
Has anyone tried running race gas in a Gen 4 w Mopar PCM?
Race gas?
- Thread starter Boxer12
- Start date
Yes. No noticeable or measurable difference over the 92 pump gas. Even so, I mix it in when I'm racing just for the extra protection. I shoot for a 96 octane calculated mix which should have an extra margin in case the quality of the gas is poor.
Boxer12
Enthusiast
Keith, do you have the Mopar PCM (I assume yes). Is that about a 3:1 ratio with 91-3:100 octane? Jim
Yes I have the Mopar PCM but it added zero horsepower. I was also hoping it would allow me to remove the deflector in the hood intake but I still get a CEL and limp home mode if I take it out. The throttle seemed a bit improved though. Overall a worthless mod but I didn't really want to hassle with having the stock PCM reinstalled so it's still in.
Your ratio comes out to 97.75 octane mathematically but I don't know if that's really how it works out. It should be more than enough though. I've also mixed in some leaded race gas when I can't find any high octane unleaded and there hasn't been any bad side effects from that. Makes the inside of your exhaust tips turn light gray though.
Martin
Enthusiast
I've also mixed in some leaded race gas when I can't find any high octane unleaded and there hasn't been any bad side effects from that. Makes the inside of your exhaust tips turn light gray though.
I'm sure you already know this, but even two or three tanks of leaded race gas will kill your cats, and once they're dead, they can plug up pretty quick (assuming you cats are still installed). The O2 sensors will also eventually get messed up from the leaded race gas, which can lead to all kinds of problems with proper fuel delivery. You may not have noticed any bad side effects yet, but when strange things do start happening, keep that in mind. Also, I think there may be some warranty issues with running leaded in an unleaded-only engine.
I am aware of all that but it's a good reminder for folks.
I've found in my many years of burning leaded gas in late model cars with 02 sensors, that it takes quite a bit to foul a sensor. I'm sure others have had different experiences but that's been mine. In fact, there was only one instance where a sensor started getting lazy and I raced the snot out of that car and it had over 70,000 miles on it. Cats are another story. I remove them on my '09 when I'm off road.
I'm pretty confident in saying that the small amount of leaded gas I'll burn in this car will never be enough to cause a problem.
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Boxer12
Enthusiast
I have the Belanger race exhaust with high flow metal cats and no warranty (track used ACR).
Tere
Enthusiast
You only need to up the octane if you alter air-fuel ratio (anything which would result in a leaner mixture) -- you will never, ever get more HP by upping only the octane (myths die hard). Increasing octane allows you to safely run slightly leaner A/F mixtures -- leaner mixture what gives you a tad more HP. The purpose of increasing octane is to avoid detonation / pre-ignition which tends to destroy pistons in a heartbeat.
You can up the octane 1 point by adding a gallon of toluene to the tank. So 1 gallon of toluene over a 93 octane tank will give you about 94 octane. Toluene alone is 114 octane - high boost F-1 cars used up to about 80% toluene many moons ago.
PS: When Granny wants to squeeze a few extra ponies out of her high boost '03 350Z, she'll lean down slightly and dump a couple gallons of toluene in.
You can up the octane 1 point by adding a gallon of toluene to the tank. So 1 gallon of toluene over a 93 octane tank will give you about 94 octane. Toluene alone is 114 octane - high boost F-1 cars used up to about 80% toluene many moons ago.
PS: When Granny wants to squeeze a few extra ponies out of her high boost '03 350Z, she'll lean down slightly and dump a couple gallons of toluene in.
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ViperGeorge
Enthusiast
Octane is a measure of gasoline's resistance to detonation. I believe the higher the octane the slower the burn. Engines that are set up to run race fuel must run race fuel or detonation can destroy the engine. Running too high an octane in a regular engine can, or so I've been told, lower power output since the gas burns slower.
You only need to up the octane if you alter air-fuel ratio (anything which would result in a leaner mixture) -- you will never, ever get more HP by upping only the octane (myths die hard). Increasing octane allows you to safely run slightly leaner A/F mixtures -- leaner mixture what gives you a tad more HP. The purpose of increasing octane is to avoid detonation / pre-ignition which tends to destroy pistons in a heartbeat.
You can up the octane 1 point by adding a gallon of toluene to the tank. So 1 gallon of toluene over a 93 octane tank will give you about 94 octane. Toluene alone is 114 octane - high boost F-1 cars used up to about 80% toluene many moons ago.
PS: When Granny wants to squeeze a few extra ponies out of her high boost '03 350Z, she'll lean down slightly and dump a couple gallons of toluene in.
I disagree with the part in blue but agree with the part in red. When you're racing, engines get hot. Hotter than normal. The extra heat will increase the chances of detonation. I ran my '97 GTS on premium all the time. The engine was bone stock. The only time I ever heard it ping was on a road course. Mixing in some race gas would have prevented that. That's the only reason I do it now even though the Gen 4's supposedly have knock sensors. Safety and to keep the ECM from retarding timing.
It's true, you don't need more octane than what's required by your engine and that excessive octane may reduce power. I've never experienced that but I've also never run any of my naturally aspirated cars on straight race gas. Boosted engines are a whole separate issue.
