Re: Water vs Methanol : Ultimate Tuning
During the time researching about water injection during the past 3 years I never came across into a definitive thread on "How to tune correctly water injection". Let's try to define this here.
Presently I have a basemap tuned by myself on 100% water injection. During this time I came across that eventually the practice of water injection does infact change the theory of fuel & ignition timing needed by far.
Right now I am boosting a 1.5L engine with a GT2560R turbo @ 18psi. The engine is happy with a 13.5 AFR on high load. Insanely this is a ratio a normally aspirated engine should run.
I am using an AEM progressive injection system start injection at 6psi and give it full at 10psi (due to no intercooler). Injecting about 350cc PRE-Throttle body and 150cc PRE-Turbo = Total of 500cc
Pre-turbo comes 4psi later than Pre-throttle body by using a variable check valve.
At this stage I am seeing about 50DegC during high-load/rpm @ 18psi @ 500cc water injection. Ambient is 26DegC and injecting below 10psi temps stay within 30DegC.
--------------------------------------------------------------------------
Water to fuel injection Ratio :
A hard pull on 4th gear up to 7000rpm :
Start of water injection @ 6psi = 250cc of water
End of water injection @ 18psi = 500cc of water
Fuel according datalog :
@ 6psi Boost / 564cc x 4 injectors = 2256cc @ 20% Duty = 451cc
250cc water vs 451cc fuel = 55% Water to Fuel
@ 18psi Boost / 614cc x 4 injectors = 2456cc @ 46% Duty = 1130cc
500cc water vs 1130cc fuel = 44% Water to Fuel
According to the theory of water injection, not more than 15% water to fuel should not be injected as it could cause damage to the engine. Apparantly this is all falks as I am running this setup for more than a year without damage !
--------------------------------------------------------------------------
What are the differences in the burn when injecting 100% Water vs 50/50 Water/Methanol ?
I am not going into chemistry and molecules, all we want to know is "What are the overall effects when injecting Water Only or 50/50" ?
We all know this! Water does not burn so injecting 100% water does it's "100%" to cool the Flame down.
But what happens to the Flame Burn when using a 50/50 mixture?
Methanol burns slowly than Pump fuel so still it does a % to cool the Flame down. So roughly now we have 60% is there to cool down the flame while 40% is there ready to burn.
So if we take a 100% water burn vs a 50/50 Water/Meth burn, the 50/50 is going to burn hotter.
Heat increases pressure - More pressure = More Power. So logically a 50/50 if tuned right! it should produce more power overall.
--------------------------------------------------------------------------
What Happens to the AirTemp when using 100% water or 50/50?
Air is cooled by the evaporation of the liquids during a rush of Air or more boost. The hotter the Air the more the evaporation effect takes place. That's why many find water injection in forced induction applications and many tell not to inject below 20DegC.
There is a theory saying that when two different liquids like methanol and water are evaporated at the same time, evaporation can be increased above the theoretical 100% relative humidity thus cooling more air. (100% R/Humidity means altough there is a rush of air, there is so much water in the air that the air rush is not enough for evaporation to take place thus no more cooling can be obtained)
I still do not have a practical data to confirm this but I am working on it.
--------------------------------------------------------------------------
Tuning on 100% Water then 50/50. Why?
From experience in tuning, I confirm that 100% Water does not change AFR altough if injected more than it should boost could not reach it's maximum since the turbine needs heat/speed of the flame to run. Water slows this process down eventually.
The best is to tune on 100% Water and find maximum power/torque with the least possible AFRs. Mine is about 13.5AFR.
Once tuned right on 100% Water, put a mix of 50/50 and leave all as it is. Make a run and AFRs should go below the 100% water values since now methanol is burning aswell. Put the engine on dyno and check power/torque accordingly. If W/M injection is right you should leave the ignition timing as it is as the extra timing was already put during the 100% water tune.
|