18psi

iTrader: (76)

you can run -50F IAT's (let's just dream here) and disconnect the wastegate running ALLOFIT, and the 2554 still aint gonna magically start flowing more than it does or being any more efficient at it. I just tuned a 2554 on a 1.6 on e85 a little bit ago. past 10psi aint not much happenin, and that's with corn where I can get creative with timing.

cyotani

iTrader: (8)

I'm thinking about playing around with water meth on my turbo build as well. I'd expect it to be most beneficial on knock limited engine/turbo configurations.


My internal through process on water's cooling effects on air density (this is not full thought out and might be very wrong, just generating ideas to spark some conversation on the subject):

You injected water-meth post turbo at say 15 psig (29.6 psia) and 150F (610 R). The water vaporizes and absorbs some heat. Maybe 30 F taking the IAT down to 120F (580 R). The mass of the air doesn't change at all from this reduction of IAT, and by using the ideal gas law then P2 = P1 * (T2/T1) so the Pressure of the boosted air should decrease to 13.5 psig according to my napkin math...
PS: I know this is very over simplified.

The decrease in temperature will not add extra oxygen molecules to your air charge. However, it will help some with auto ignition detonation so if that is limiting your spark advance the decrease in temperature will help overall power.



The other weird piece of the puzzle is that methanol is a fuel that reacts with oxygen during combustion. Methanol and gasoline are both competing with the available air.
Methanol makes best power around 4:1 AFR and gas at 12:5:1.
If you inject 15% methanol of your gas volume then in order to achieve a 12:5 AFR for your GAS reaction your overall AFR needs to be 10.8:1



Basically, richen up your target AFR tables when you add methanol.



I'm I making stuff up or is this logic on the right track.

Savington

iTrader: (31)

Sort of. True AFR, yes. Gas-scale gauge AFR, no. Since the gas-scale gauge is converting from lambda, it will automatically compensate for the difference in stoich ratios between methanol and gas. IOW, your target AFRs on a gas-scale gauge won't change.

The really curious thing about water injection is that the water you inject displaces air molecules that could have been there. As a result, water injection is really only beneficial if you're detonation limited the whole way through. If you are det limited, you can't take advantage of the air you already have anyway, so replacing some of it with water to make better use of the air that's left is a good idea. If you can get to MBT without WI, then water will just decrease power. As such, running water on a turbo like a 2554R will result in midrange gains where you were detonation limited before, but no top-end power gains.

Methanol is a little different because it contains an oxygen molecule, so you end up making more power by displacing some air with the volume of methanol. Taken to its extreme, replacing all the gas with methanol will result in a huge power bump (and a fuel system twice as big as the one you had on gas).

cyotani

iTrader: (8)

ahh, good point, they are lambda sensors... not AFR sensors.

SuperSeb

iTrader: (1)

Thanks for the explanation. My cooling the charge air you reduce its pressure, effectively reducing the turbo pressure ratio (you dropped the pressure after the turbo). But I guess that even at a lower pressure the 2554 can't flow much more (it might just be more efficient, cf turbo map).

I just wanted a fun system with a big red button :-)

cyotani

iTrader: (8)

I think you'd still have the same pressure ratio across the turbo compressor wheel. The WM injection cooling of the air charge typically happens down stream after the charge air cooler.

Savington

iTrader: (31)

Yep. The only way you change the p/r is by injecting pre-compressor, and that wreaks havoc on the compressor wheel.