Say if a car was tuned for C 16, leaded, motor octane of 117 and spec gravity of .735. How will the car run on Sunoco Maximal, leaded, motor octane of 114 and gravity of .701.

I spoke w/ Todd K and he believes that the different gravity may be problematic. How critical is the gravity?

 

Damn you Sean! I just made a post in your other thread asking the same thing. I have a friend who works in the lab (now is a manager, but use to be a lab guy) for one of the biggest fuel/chemical testing companies in America. I called him to ask the question but he didn't answer.. I mean seriously who ignores phone calls at work. I see it as a free smoke break for the non-smoker LOL!

 

Hopefully one of our tuning and fuel guru's will come in explain to us everything. I know my friend is lazy and I doubt I'll get a call back until he wants to go to the bar. LOL!

 

I am no expert, lol. However, I would guess that specific gravity will have an effect on your A/F ratio. So in your case the .735 number is larger and requires more air. The .700 is a smaller number and may require less air or you will be running to lean for the same tune. I figured our ECU's would compensate for this but maybe not?. In my musclecar days, we had to rejet for different fuels.

 

Luckly enough I'm young enough to not have to deal with Carbs, but I did have to reset my fuel pressure do to weather everytime I was at the track for my n2o kit. I used C16 in that tank.

 

951,

So .701 is going to run leaner than .735? That would explain the detonation issues I had. I definately will not run high boost (over 1.3) until I get some C 16.

 

I would also think that the specific gravity decreases with temp, and we all know how these ecu's like to pull timing on hot days. I would think that the lower spec.grav. would do the same and cause the ecu to pull back timing. This is what I meant by ecu compensating. I know that is not a good thing.

It would be interesting to see if any of the tuners have tested the different grades to see what happens. Problem is that octane levels change as well, so how much do you attribute to spec.grav over octane?

it would be interesting to compare these two. One has higher octane and the other higher SG.

C16
Used in: Turbocharged engines, blown engines and nitrous applications. NHRA Comp Eliminator spec fuel. Recommended by the top nitrous oxide companies.
• Color: Blue
• Lead: 6 Grams per gallon
• Motor Octane: 117
• Specific gravity: .730 at 60° F



C23
Recommended for Ultimate Performance in Nitrous Oxide Applications. Used in 800cid IHRA-style drag race engines.
• Color: Blue
• Lead: 6 Grams per gallon
• Motor Octane: 119
• Specific Gravity: .7096 at 60° F


Powell, musclecars still use carbs as well as injection, so it isn't your age as much as it is the type of car you got into. For WOT carbs are good, for modulation forget it, they suck. But most american musclecars go down a 1/4 mile at WOT and that is all they want.

 

yes, theoretically(again I'm no expert) because it weighs less at that A/F. So your A/F increases, by how much? I have no clue and I didn't think it would be that big a deal, but maybe it is.

 

i 2nd that!!!

 

Oh yeah def. the big n2o and N/A cars still run carbs. I am a turbo man myself Next car I build when I get into a house and my pay stabilizes will be a twin 88+mm 99+ Mustang that will run on a drag radial. 2500-2800hp on a drag radial Sadly 8.9s @ 151 was just a tease to me. I am addicted to speed which scares the crap out of my family LOL!

 

What's the SG of 104 or MS109 for comparison?

 

I found this, but not sure how accurate it is. These to VP's seem pretty close even though their octane levels are much different.:

VP RED
A great standard grade of racing fuel. Used in any high compression race engine up to 13:1, off-road racing, marine engines, motocross, karts and personal watercraft.

• Color: Red
• Lead: 4.23 Grams per gallon
• Motor Octane: 105
• Specific Gravity: .730 - .745 at 60° F



VP-110
Formulated for use in drag race, oval track, road race and off road competition in normally aspirated engines with compression ratios up to 14:1. Good lower cost alternative to the other guys stuff.

• Color: Purple
• Lead: 4.23
• MON: 107, RON 113, R+M/2 = 110
• Specific Gravity: .73 at 60° F

 

i was wondering the same thing cuase the vp 104 is much more expensive then the sunoco 104 ....i mean whats the difference??

 

I can't find VP

 

MOTORSPORT 103
MS103 provides power and protection equal to some leaded racing fuels. Compared to Motorsport 101, it allows even more aggressive timing and higher compression-up to 14:1 in cast iron head engines and up to 15:1 with aluminum heads. Can allow doubling of stock boost - consult your engine builder. Also contains no metal compounds and won't harm catalytic converters or oxygen sensors. AMA legal for Supercross & Outdoor Nationals.


color red
oxygenated yes
motor octane 99
r+m/2 103
specific gravity .743 at 60 deg.


that is the VP rating.