volume vs. mass

[Pit Viper]

I was reading through RICE RACING's posts, and it got me back to the volume vs. mass issue with water injection. I think most people start out working with volume, but when you look at people who have really gotten into the science behind it (RICE RACING, Richard, etc...) they talk about mass.

I started relooking at my current setup in terms of mass vs. volume, and it looks to me like it makes at least a 5% difference in my mixtures. I'd love some feedback on this.

Currently I have a V6 running 508 cc/min injectors. I'm running a direct-port setup with a 0.3 mm jet at each port, and I run a 50/50 mix of distilled water and methanol.

Without getting overly complicated on the math, by volume: 102 / 508 = 0.20.
So, 10% of water and 10% of methanol vs. fuel.
Or, the total mixture is 83.2% gas, 8.4% methanol and 8.4% water.

However, by mass, gasoline has only 73.7% of the mass of water, and methanol 79.1%.
So, by mass the mixture is now 80.4% gas, 8.6% methanol, and 11% water.

To work it in the opposite direction, if I wanted to inject water at 15% of fuel, and run a 50/50 mix by mass, what size jets would I need? My fuel injectors won't change, so:
508 cc/min (.737) = 374.4 374.4(15%)=56.16 for water. 56.16 / (.791)=71 for methanol
71 + 56.16 = 127 cc/min jet. So, I would need to ramp up my jets by 24.5% to get to that mix, right?

[RICE RACING]

I was reading through RICE RACING's posts, and it got me back to the volume vs. mass issue with water injection. I think most people start out working with volume, but when you look at people who have really gotten into the science behind it (RICE RACING, Richard, etc...) they talk about mass.

I started relooking at my current setup in terms of mass vs. volume, and it looks to me like it makes at least a 5% difference in my mixtures. I'd love some feedback on this.

Currently I have a V6 running 508 cc/min injectors. I'm running a direct-port setup with a 0.3 mm jet at each port, and I run a 50/50 mix of distilled water and methanol.

Without getting overly complicated on the math, by volume: 102 / 508 = 0.20.
So, 10% of water and 10% of methanol vs. fuel.
Or, the total mixture is 83.2% gas, 8.4% methanol and 8.4% water.

However, by mass, gasoline has only 73.7% of the mass of water, and methanol 79.1%.
So, by mass the mixture is now 80.4% gas, 8.6% methanol, and 11% water.

To work it in the opposite direction, if I wanted to inject water at 15% of fuel, and run a 50/50 mix by mass, what size jets would I need? My fuel injectors won't change, so:
508 cc/min (.737) = 374.4 374.4(15%)=56.16 for water. 56.16 / (.791)=71 for methanol
71 + 56.16 = 127 cc/min jet. So, I would need to ramp up my jets by 24.5% to get to that mix, right?

Everything is related to meaning by mass, how many molecules you are using of any given item, be it oxygen, hydrocarbons, or water. All your AFR's are by mass not volume, so it makes sense to talk water injection by mass as well (not cc/min). < as that does not relate to anything really at the end of the day.

All the old reports you read are by mass and they may or may not (usually qualified in the Introduction and testing methods) include such things as the fuel content of the WI mixture if WM50/50 to the overall fuel weight let alone the density of the combined mixture/s and its true mass v's 100% water. Either way its going to be within 10%~(less mass) on a WM50/50 mixture compared to pure water.