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  #1  
Old 16-01-2006, 10:40 PM
sdminus sdminus is offline
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Default Water and AFR

I am about to tune my rx7. I am gonna do a base tune at 11.1:1 afr. (rotaries like it rich) AFter the base fuel map is set up i want to take full advantage of my WI system. I am still having toruble deciding how much water to add in realtion to fuel. I have seen people talk about subtracting fuel and replacing with water like for like. Is this true?????.
Is this the reason why whe n water is added performance drops????
I am of the understanding that we use water to replace the fuel used to cool the combustion. But water is more efficent at heat absorbsion. I am told 3 times better than petrol. With this inmind can i say pull fuel and replace with 1/3rd water???
can any body enlighten me and save me from an expensive mistake

Scott
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Old 19-01-2006, 12:04 AM
sdminus sdminus is offline
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Any body
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  #3  
Old 20-01-2006, 10:43 AM
slostar slostar is offline
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just go with the usual 10-20% water to fuel, just how much will depend on your setup.. not sure how others go about it. but i did a base tune at about 11.5:1 a/f. then added the water injection, (noted no diffrence in afr) lean it out to around 12:1a/f added a bit more boost.
havent had much to do with rotaries. but know enough, to know that going lean will pretty much says goodby to the apex seals. definitly lean it out more than 11.1:1 as the water will be taking over the cooling effect of the extra fuel and then some, like you said.. just how lean to go i cant answer sorry
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Old 20-01-2006, 03:33 PM
sdminus sdminus is offline
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Cheers. Like you say its hard to know how far to lean it out. I dont want to be sticking loads of extra water in with an already rich AFR. Do you think that i should proced with a EGT gauge and extreme caution. I was thinking may be this would show how the combustion temps were reacting and maybe give me a few pointers.

Scott
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Old 12-05-2006, 02:44 AM
TurboGTi TurboGTi is offline
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any updates on this ?

I know sometimes ago there was a post on WI and AFR mixtures ... i would have to do a search to find it
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  #6  
Old 13-05-2006, 01:40 AM
slostar slostar is offline
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done a coupe or runs on the road awhile back. same part of the road. each starting about 3000rpm and finishing at 7400 (limter) in 3rd gear. then over layed them. one of the graphs is on flat road one is done on a hill. so they nowhere near perfect being done on the road. but gives an idea.

dotted line no wi. solid with 100% water, water wi comes on aroud the 4 sec point. you can see the change in afr







so you can see it does lean the afr slightly. less at hig revs as its only single stage setup.
its not a great deal diffrent, thats probably why i didnt notice it while just watching the guage.
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  #7  
Old 13-05-2006, 10:49 AM
sdminus sdminus is offline
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What air fuel meter are you using. Does it correct for egt.

Scott
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  #8  
Old 15-05-2006, 09:44 AM
slostar slostar is offline
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lm1. far as i know it does compensate for egt's.
i will do some better runs when the car is going again. in 4th gear this time so it gives a better resoution. will try log rpm as well.
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Old 15-05-2006, 09:55 AM
sdminus sdminus is offline
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Yeah i think it does. I use the LM-1 also. what program is that log displayed in ?

Scott
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  #10  
Old 16-05-2006, 06:34 AM
slostar slostar is offline
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seems to be a pretty good meter huh. an older vesrion of logworks, theres a later version out on the inovate site.
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