SCC's EVO dyno'd
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From: SoCal
But lower specific gravity means smaller molecules, so more of them "fit" in the same "set volume" as you put it. Therefore, for the same volume injected (meaning same pulse width), a lower specific grav. fuel contains more fuel molecules. More fuel molecules needs more air molecules too... (aka rich condition)
hope this helps,
heff
hope this helps,
heff
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From: SoCal
CORRECTION: It seems I have forgotten my freshman chem already... and I am only a junior...
Lower specific gravity= lower density = less mass of fuel for the same given volume... ShapeGSX-- sorry buddy but this just refutes your whole schpiel about needing to lean out the 117 octane based on s.g.... must be something else. In any case, we are talking differences of like 1.5% here so I doubt it will make much difference.
Shape: Perhaps you are just able to run a leaner a/f because the 117 is so resistant to pinging...?
Lower specific gravity= lower density = less mass of fuel for the same given volume... ShapeGSX-- sorry buddy but this just refutes your whole schpiel about needing to lean out the 117 octane based on s.g.... must be something else. In any case, we are talking differences of like 1.5% here so I doubt it will make much difference.
Shape: Perhaps you are just able to run a leaner a/f because the 117 is so resistant to pinging...?
Last edited by theheff; Mar 21, 2003 at 11:08 AM.
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Originally posted by ShapeGSX
No, a lower specific gravity fuel will flow more fuel through an injector at a given pulsewidth than a higher specific gravity fuel. That means that the car will run richer in open loop mode.
No, a lower specific gravity fuel will flow more fuel through an injector at a given pulsewidth than a higher specific gravity fuel. That means that the car will run richer in open loop mode.
EDIT: yeah, theheff beat me to this. That'll teach me to read all the posts in a thread before responding...
I see this every time I put 117 octane VP C16 race fuel (0.73 SG) into my car. I have to lean the car out at least 13 to 14% to get it running right as compared to 93 octane pump gas.
I bet you're reading a/f using a standard narrowband O2 sensor. No?
Last edited by Ron; Mar 21, 2003 at 11:53 AM.
Originally posted by ShapeGSX
That table only addresses octane. It does not address specific gravity. Most pump fuels have a specific gravity of around 0.76. 76's web page indicates that their 100 octane fuel has a specific gravity of 0.744. The addition of the 100 octane fuel's lower specific gravity would have meant that the car was running richer than it would have if they had just put 93 octane fuel into the tank.
As well, if they didn't drain the tank and precisely mix the fuel, who knows what they ended up with. It is very hard to guage the amount of fuel that is left in a gas tank.
That table only addresses octane. It does not address specific gravity. Most pump fuels have a specific gravity of around 0.76. 76's web page indicates that their 100 octane fuel has a specific gravity of 0.744. The addition of the 100 octane fuel's lower specific gravity would have meant that the car was running richer than it would have if they had just put 93 octane fuel into the tank.
As well, if they didn't drain the tank and precisely mix the fuel, who knows what they ended up with. It is very hard to guage the amount of fuel that is left in a gas tank.
Erik
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Ron and Heff
That was what I was getting AT!!!
What Shape was saying didn't make sense to me either! haha
I was waiting for him to say that my statement was true, in which case since lower SG means less dense, and thus LEANER CONDITION!
And I thought I was missing something here.
I haven't dealt with chem. inawhile too.
That was what I was getting AT!!!
What Shape was saying didn't make sense to me either! haha
I was waiting for him to say that my statement was true, in which case since lower SG means less dense, and thus LEANER CONDITION!
And I thought I was missing something here.
I haven't dealt with chem. inawhile too.
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From: Frederick, MD
Originally posted by shiv@vishnu I'm thoroughly impressed by your DSMLink engine control equalizer/fader. It looks like it would do a wonderful job controlling the frequency response of my stereo system.
Shiv, I understand that statement was made in the "heat" of a debate, so I'm not putting much weight to it. I just wanted to point out that nobody has a final tuning solution for everybody, as I'm sure you know. Some will want an AFC with little knobbies and a cool display; some will want a full blown standalone that provides *hours* of enjoyment digging through manuals and such, but in the end provides every adjustment known to man.
And then there are all the rest of us in the middle. There's a lot of ground between those two extremes. So much so that no single tool will provide all the answers. DSMLink has never claimed to provide *all* adjustments that could possibly be made inside the ECU; doing so would violate one of the principles of its creation. That is to be easy to use while providing all the functionality *most* people need. It's not intended to and never will support every tweak under the sun.
The one example you brought up later in this thread is a good one. We do not provide a means to tweak individual load cells in the ECU. We have no intentions of doing that. In most cases, it seems to be overkill. What we do in cases where something like that is appropriate (fuel adjustments) is to interpolate the values entered by the user that are intended for the highest load cells so that they are scaled appropriately in the lower cells based on the relationship established by the manufacturer between the two.
That's not to say a tool that provides that detailed level of control isn't needed. It is. It's just not needed by most people, IMO.
Regardless, the point is moot with respect to the EVOs until we or someone else gets into the code and figures out what's really going on.
Thomas Dorris
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Somehow I missed the specific gravity replies. I looked back at the calculations. It turns out that I made an order of operations error when I looked at the specific gravity adjuster. Doh! I was wrong, a lower SG will make a car run leaner with the same injector pulsewidth. The jump down from .76 (pump gas) to .73 (race fuel) leads to a positive change in the air to fuel ratio of around .4 in the 11:1 range.
I just figure I'll wait it out a bit to see what sort of packages become available. I do want a programmable ECU, but I can live with a piggyback if I can hide it well enough to be able to disable it completely for dealer service.
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Sorry, I'm back to thinking I am right on the specific gravity thing. 
http://www.smithtex.com/racing/fuelc...ml#Terminology
That was my original thinking on the subject. Now, I'm standing by it.
http://www.smithtex.com/racing/fuelc...ml#Terminology
Specific Gravity (SG):
Density of the fuel. (a) This is the weight of fuel compared to water, water being at 1.00. If race fuel is .750 (specific gravity) it would weigh ¾ the weight of water. If water at 60 degrees Farenheit weighs 8.125 pounds per gallon (ppg), then race fuel at .750 will weigh 6.09 (ppg). (b) The less dense the fuel (lower specific gravity) the higher the BTU content and the better the stability of the fuel at higher RPM's. (c) The lower the specific gravity of the fuel, the more crucial the jetting becomes, and the easier it is to run the engine lean, possible causing internal damage. (d) The combustion speed is determined primarily by the pressure (density) of the fuel mixture. A lower (SG) or viscosity fuel will flow more through an orifice (jet) and a higher (SG) or viscosity will flow less.
Density of the fuel. (a) This is the weight of fuel compared to water, water being at 1.00. If race fuel is .750 (specific gravity) it would weigh ¾ the weight of water. If water at 60 degrees Farenheit weighs 8.125 pounds per gallon (ppg), then race fuel at .750 will weigh 6.09 (ppg). (b) The less dense the fuel (lower specific gravity) the higher the BTU content and the better the stability of the fuel at higher RPM's. (c) The lower the specific gravity of the fuel, the more crucial the jetting becomes, and the easier it is to run the engine lean, possible causing internal damage. (d) The combustion speed is determined primarily by the pressure (density) of the fuel mixture. A lower (SG) or viscosity fuel will flow more through an orifice (jet) and a higher (SG) or viscosity will flow less.
He didn't do it, some jackhole trying to boost his post count did it and had his post deleted.... so now it is not visible and it looks like Mighty is the one who bumped a dead thread.
Keith
Keith
