Totally don't know why I'm posting this in 3800 land. Just because that's where things go, I guess.
So I've been doing the usual over-thinking/math about increasing mass flow through a turbo(s) at the limit of what the turbo will deliver. Specifically, trying to figure out how much more I could squeeze out of the stock turbos on the Mercedes because upgrading them is simply not an option (for multiple reasons...it's an engine out job, more than 850hp requires a $15,000 standalone computer because there's supposedly no adjustment any of the tuners have access to to scale injectors in an S600 computer, everything involved is enormously expensive).
Basically, I was trying to figure out exactly how much mass flow increase you get through a turbocharger from the vaporization cooling out of a wet nitrous shot (propane on the fuel side) at a ratio of around 27% of your non-nitrous horsepower in terms of the shot size. That's 200hp on top of 750 worth of non-nitrous airflow. Anybody else want to struggle with the math on that to verify my findings? This is with the assumption that the turbo is absolutely maxxed out, boost falling off, and it's already been intercooled to the max so the temperature change has no effect on power apart from mass flow through the compressor. It may end up putting a little more to the ground from VE/pumping loss changes as well, but with the compressor as the limiting factor it shouldn't matter how easily the engine breathes...if it takes in more air, it would just be at less psi and due to choke flow at the outlet, turbos flow the most air mass at mid to higher pressures, usually 1/2 to 3/4 the way up their chart. So reducing boost pressure through intercooling or other means that make the engine more efficient would not have a positive effect on the absolute mass flow the turbo could deliver. The ONLY way left to increase power out of these bad boys would be by improving air density at the compressor inlet. Water/meth cannot do this to significantly low temperatures so despite helping shift the map a little bit due to wet compression, but cannot do so to the extent of a 70-100 degree F inlet temp drop that a nitrous/propane combo can provide.
I come up with around a 14% inlet density improvement if you vaporize all the nitrous and propane before it hits the turbo, but the nitrous/propane combo displaces around 10% of the air mass in doing so for a net mass flow gain of around 4% and a net hp gain of the nitrous shot plus that 4% applied to the pre-nitrous horsepower. In this case that's 750 base HP * 1.04 = 780hp plus the 200 shot of nitrous = 980hp. Which is a shame because I'd love to call it an even 1000. The 4% was a very complicated and recursive calculation overall so I don't want to go into it here, but does that sound about correct? 30hp of free/incidental power on top of a 200 shot? I KNOW that it would be a lot more if the nitrous functioned as intercooling and the turbo was maintaining a set boost, but that's not what I want to know for the following reasons:
I know I've seen people claim crazy gains from this over and above the nitrous shot size, but I think that's often due to the turbo being on a boost controller, not running all out...so obviously colder charge air is going to result in a lot more air mass at the same boost pressure IF the turbo can deliver it. But if your compressor is maxxed out, it's a different story and that's the situation I am trying to predict. These will be absolutely off the map on the screaming edge probably with no wastegating before I even think about adding the nitrous.
Does anyone have real-world results of a similar situation? By that, I mean spraying nitrous through a turbo that was small enough to not be able to maintain the peak boost in the upper rpms. Most likely a stock turbo on some car or other that was on the bottle? I would need to know the shot size, the horsepower without it, and the horsepower with it, and it would have to have been sprayed pre-compressor. I'm not interested in incidental intercooling gains, the math on that is easy enough. I want to know the net effect on air density vs total new volume...which I have come to believe is around 10% at that 27% of horsepower shot sizing (and the propane is something like 1.5% of that, so probably 8.5% on the nitrous alone).
So I've been doing the usual over-thinking/math about increasing mass flow through a turbo(s) at the limit of what the turbo will deliver. Specifically, trying to figure out how much more I could squeeze out of the stock turbos on the Mercedes because upgrading them is simply not an option (for multiple reasons...it's an engine out job, more than 850hp requires a $15,000 standalone computer because there's supposedly no adjustment any of the tuners have access to to scale injectors in an S600 computer, everything involved is enormously expensive).
Basically, I was trying to figure out exactly how much mass flow increase you get through a turbocharger from the vaporization cooling out of a wet nitrous shot (propane on the fuel side) at a ratio of around 27% of your non-nitrous horsepower in terms of the shot size. That's 200hp on top of 750 worth of non-nitrous airflow. Anybody else want to struggle with the math on that to verify my findings? This is with the assumption that the turbo is absolutely maxxed out, boost falling off, and it's already been intercooled to the max so the temperature change has no effect on power apart from mass flow through the compressor. It may end up putting a little more to the ground from VE/pumping loss changes as well, but with the compressor as the limiting factor it shouldn't matter how easily the engine breathes...if it takes in more air, it would just be at less psi and due to choke flow at the outlet, turbos flow the most air mass at mid to higher pressures, usually 1/2 to 3/4 the way up their chart. So reducing boost pressure through intercooling or other means that make the engine more efficient would not have a positive effect on the absolute mass flow the turbo could deliver. The ONLY way left to increase power out of these bad boys would be by improving air density at the compressor inlet. Water/meth cannot do this to significantly low temperatures so despite helping shift the map a little bit due to wet compression, but cannot do so to the extent of a 70-100 degree F inlet temp drop that a nitrous/propane combo can provide.
I come up with around a 14% inlet density improvement if you vaporize all the nitrous and propane before it hits the turbo, but the nitrous/propane combo displaces around 10% of the air mass in doing so for a net mass flow gain of around 4% and a net hp gain of the nitrous shot plus that 4% applied to the pre-nitrous horsepower. In this case that's 750 base HP * 1.04 = 780hp plus the 200 shot of nitrous = 980hp. Which is a shame because I'd love to call it an even 1000. The 4% was a very complicated and recursive calculation overall so I don't want to go into it here, but does that sound about correct? 30hp of free/incidental power on top of a 200 shot? I KNOW that it would be a lot more if the nitrous functioned as intercooling and the turbo was maintaining a set boost, but that's not what I want to know for the following reasons:
I know I've seen people claim crazy gains from this over and above the nitrous shot size, but I think that's often due to the turbo being on a boost controller, not running all out...so obviously colder charge air is going to result in a lot more air mass at the same boost pressure IF the turbo can deliver it. But if your compressor is maxxed out, it's a different story and that's the situation I am trying to predict. These will be absolutely off the map on the screaming edge probably with no wastegating before I even think about adding the nitrous.
Does anyone have real-world results of a similar situation? By that, I mean spraying nitrous through a turbo that was small enough to not be able to maintain the peak boost in the upper rpms. Most likely a stock turbo on some car or other that was on the bottle? I would need to know the shot size, the horsepower without it, and the horsepower with it, and it would have to have been sprayed pre-compressor. I'm not interested in incidental intercooling gains, the math on that is easy enough. I want to know the net effect on air density vs total new volume...which I have come to believe is around 10% at that 27% of horsepower shot sizing (and the propane is something like 1.5% of that, so probably 8.5% on the nitrous alone).