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Old 11-06-2004, 07:06 PM
TurboGTi TurboGTi is offline
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Default Calculate your correct injection Percentage !

As the topic says please can someone post the information on how to calculate
fuel injector flow in cc/min
and also
WI flow in cc/min

along with all the necessary calculations to obtain optimum Water injection percentage


thanks
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Old 11-06-2004, 10:51 PM
Richard L Richard L is offline
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Are you referring how much water is needed to replacing excessive fuel injected based on stoichimetric air/fuel mixture?

For example, if an engine is running with rich air furl mixture to maintain resonable egt level and and knock free - 10-10.5:1 is normally considered as a safe tune by most tuners now a days and manufacturers.
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Old 12-06-2004, 07:23 PM
TurboGTi TurboGTi is offline
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Quote:
Originally Posted by Richard L
Are you referring how much water is needed to replacing excessive fuel injected based on stoichimetric air/fuel mixture?

For example, if an engine is running with rich air furl mixture to maintain resonable egt level and and knock free - 10-10.5:1 is normally considered as a safe tune by most tuners now a days and manufacturers.
Well its more of calculating how much CC/min of water must be injected .

I've previously seen some guys in here calculating their cc/min for both the fuel injectors and their water injection.

I'm not certain if this is foe AFR tuning or just general injection amounts.

Currently i'm running water injection on my 1300cc but i have 380cc fuel injectors. My WI jet that i'm using is a 0.5mm on the race pump.
My WI is active at 10 psi full boost is 15psi.

What i want to know is if the 0.5mm jet is enough.

I've seen people make reffeerence to the chart that you have richard with the various Jet flow rate at xxxpsi !

You understand what i'm saying... i'm a bit confused myself
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  #4  
Old 13-06-2004, 10:44 AM
Richard L Richard L is offline
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The quantity of water will largely depending on the following factors:

1. effective cmpressure ratio
2. fuel grade
3. egt
4. knock tendency
5. ambient temperature
6. final charge temperature
7. a/f ratio
8. how close you run your engine towards MBT timing

Most factory produced car will have all the above variables under control. As soon as you start to modify your engine - you will notice a few of the above variables will change - but if it is inside the safe-operating area of the ECU, minor adjustment to the fuel, timing etc will keep the engine safe.

Most factory fitted ECU employs the following procedure strategy to keep the engine alive with the following balancing act:

1) retard timing with mild knock (knock sensor)
2) Increase air/fuel and timimng with heavy knock.

It normally works very well until you iincease the boost pressure, the excess fuel used to cool the engine is now being uswed for power.

Under this circumstances - you must replenish the engine's cooling capability by either using bigger injectors or water injection. Since water has six times the latent heat of fuel, you need to dump six litres of fuel per litre of water!

Since un-burnt fuel has huge impact on the combustion process, it robs huge amount of power if it is used as a coolant rather than as a fuel. In comparison, the OH radicals within water enhances the burn process.
(please read turboice's WI paper)

At last you question as to how mush water to inject ? the sweeping conclusion and simplied - around 10-15% w/f ratio when you are running a few psi over the stock boost.

Quite easy to calculate: add all your injectors flowrate together and multiple it by 10% or 15% - look at the aquamist jet size/flow, that is it!





It is clear that WI injectionf
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Old 06-05-2005, 09:15 PM
honki24 honki24 is offline
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dont think I get it... so I've got an evo8, w/ 550cc injectors. so all added up thats 2200cc. I have a nozzle that @ 100 psi pump pressure injects 3.9 gal/min. how do I figure out if that is enough?
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Old 06-05-2005, 09:22 PM
honki24 honki24 is offline
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k... lets see... 3.9 gal = 14763 cc ...therefore... 3.9gal/min WI should mean I am injecting 14763cc/min. In one rotation there is 4 ignitions, meaning 2200cc per rotation. if I'm at say 6K rpm... then I have 13,200,000cc per minute of fuel. and 14763cc per minute of water. that means I am running .1118% water to fuel? did I do that right?
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Old 06-05-2005, 10:12 PM
hotrod hotrod is offline
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Default nozzle flow rate

I think you need to throw out that math and start over your numbers are WAY out of the ball park!
Quote:
then I have 13,200,000cc per minute of fuel
That is 13,200 kilograms of water or about 29,040 lbs of fuel ---- I don't think so

At max rpm, WOT the injectors are nearly running continuously. Forget how many times the engine fires, ( a 4 cycle engine only fires each cylinder once every 2 revs anyway ).

You will find that the WI nozzle is probably rated in gallons / HOUR

For a gallon/hr nozzle just multiply the gal/hr by 63 and you have cc/min flow. In your case your spray nozzle flows about 246 cc/min

Your fuel injectors flow 550cc/min MAXIMUM at 100% duty cycle. So the max fuel you can flow under any conditions is 2200 cc/min. If you car runs a max injector duty cycle of 85% ( that's typical max on a factory set up) your max fuel flow is 2200 x .85 = 1870 cc/min. 15% of that is 280.5 cc/min.

Your 3.9 gal/hr nozzle will give you about 13% water to fuel at max fuel injector duty cycle and the WI spray wide open.

Larry
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Old 07-05-2005, 09:09 AM
Roverdose Roverdose is offline
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ok then...

i have 4x 750cc injectors = 3000cc/min max flow

lets say i have a max of 80% duty cycle on the injectors
80% of 3000 = 2400cc/min

15% of 2400 = 360cc/min

looking on the above flow chart id need 2x 0.4 jets (350cc) or 2x 0.5 jets (440cc)

Drew
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  #9  
Old 09-05-2005, 01:09 PM
honki24 honki24 is offline
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Default Re: nozzle flow rate

Quote:
Originally Posted by hotrod
I think you need to throw out that math and start over your numbers are WAY out of the ball park!
Quote:
then I have 13,200,000cc per minute of fuel
That is 13,200 kilograms of water or about 29,040 lbs of fuel ---- I don't think so

At max rpm, WOT the injectors are nearly running continuously. Forget how many times the engine fires, ( a 4 cycle engine only fires each cylinder once every 2 revs anyway ).

You will find that the WI nozzle is probably rated in gallons / HOUR

For a gallon/hr nozzle just multiply the gal/hr by 63 and you have cc/min flow. In your case your spray nozzle flows about 246 cc/min

Your fuel injectors flow 550cc/min MAXIMUM at 100% duty cycle. So the max fuel you can flow under any conditions is 2200 cc/min. If you car runs a max injector duty cycle of 85% ( that's typical max on a factory set up) your max fuel flow is 2200 x .85 = 1870 cc/min. 15% of that is 280.5 cc/min.

Your 3.9 gal/hr nozzle will give you about 13% water to fuel at max fuel injector duty cycle and the WI spray wide open.

Larry
thanks for helpin me there! The math really helps...however I am pretty modded, and so I definately run 90-95% duty cycle. question though... why do you just neglect the rpm?
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  #10  
Old 09-05-2005, 01:45 PM
dsmtuned dsmtuned is offline
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Default Re: nozzle flow rate

Larry[/quote]
thanks for helpin me there! The math really helps...however I am pretty modded, and so I definately run 90-95% duty cycle. question though... why do you just neglect the rpm?[/quote]


RPM is one of the factors that determines injector duty cycles. :wink:

Craig
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