EFI University

[C. Ludwig]

Someone car to check my math? Using the formula:

Efficiency =
(Pressure Ratio^.28 v Absolute Inlet Temp) - Absolute Inlet Temp
Absolute Outlet Temp- Absolute Inlet Temp


We're playing with pre-turbo water/methanol injection and the numbers are too good to be true. I'll give two sets of test numbers below. The first set was with a .75 GPH nozzle and straight water. The second set was with a 2.0 GPH nozzle and 50/50 water/methanol.

5000rpm 16.7psi 2.1PR 583 Inlet ABS 698 Outlet ABS 120%
6000rpm 16.2psi 2.1PR 582 Inlet ABS 732 Outlet ABS 90%

5000rpm 15.8psi 2.1PR 568 Inlet ABS 645 Outlet ABS 167%
6000rpm 16.8psi 2.1PR 567 Inlet ABS 671 Outlet ABS 130%

We haven't tried no injection to get an idea of what those numbers would be. However, referencing other data from other cars, the formula and my math seem to be accurate. I just see no way that we're seeing over 150% efficiency. One thing that comes to mind is the sensor being too slow to register the temp rise and we're actually much hotter on the outlet than we're recording. It's a standard GM open-element air temp sensor that we're using.

Thoughts?
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[Arnout]

pre turbo? what RPM does that turbo spin and what happens to the drops of water then?

[C. Ludwig]

At well over 200*F the water and methanol vaporize. That's what creates the charge cooling effect.

No idea on turbine speed. The expense of a turbine speed sensor is outside the scope of this project.
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Haltech, AEM, Apexi PFC Sales, Installation, Tuning
Custom Harness Solutions
www.ludwigmotorsports.com

[stevieturbo]

Extensive discussion here about it.

http://www.aquamist.co.uk/vbulletin/forumdisplay.php?f=17

And from their testing, there is no risk to the impellor when an atomised liquid is sprayed.
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9.85 @ 144.75mph
202mph standing mile
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[dkGoodrich dot com]

Very interesting!
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KY's Fastest Honda's, Acura's & Subaru's
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[Slides]

To calculate the efficiency correctly you need to account for the energy absorbed by the evaporation of the liquids. I remember seeing threads somewhere in the past where otherwise logical "engineers" claimed that the AI increased the efficiency of the compressor, not so, the heat energy absorbed by the mass is pretty much the same it is just that the injectants reduce the temp rise.

Unfortunately you can't do it with a basic spreadsheet, need to run a macro with lookups & cases etc & probably iterations to account for phase changes, different vapour pressures etc, so it is a massive PITA even if you try to do it roughly with pen & paper for a specific case.
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mazda Rx, you'd think they were full of truffles

[Grocerius Maximus]

A turbocompressor is a ratiometric device, the denser the air inlet conditions, the higher the mass flow rate at max speed, or any equivalent speed for that matter. The power difference between the same turbo at max speed sucking in 150F radiator waste heat or 60F outside air is HUGE.

Speed sensor kits can be had for $250.00 USD.

Bet way to think about compressor 'efficiency' is how much shaft power it takes to move that mass of air at that PR. When you improve the efficiency of the compressor the TURBINE expansion ratio goes down, and your turbine inlet pressure drops.

[Liborek]

[Slides]

The point is technically, lifting a mass flow to the same pressure with teh same compressor will give it the same heat.

But, with the injectant, the same mass flow can be achieved at a lower pressure ratio as it is coming out cooler, so the turbo is doing less work for the same mass flow, & hence less turbine inlet pressure for the same mass flow= less exhaust pumping loss & more power from the same air mass.

So, assuming the same compressor inducer conditions, even if you are at the flow limit of the compressor for a significant part of your rev range, by limiting your shaft speed to only what is required to maintian the pressure required at max turbo flow at that engine speed & the lower PR required by the cooler intake charge you achieve more power making hte engine system as a whole more efficient.
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mazda Rx, you'd think they were full of truffles