Water and AFR

[sdminus]

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

[sdminus]

Any body
!!!!!!!!!!!!!!!!! :D

[slostar]

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

[sdminus]

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

[TurboGTi]

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

[slostar]

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

http://img.photobucket.com/albums/v178/slostar/log2.jpg


http://img.photobucket.com/albums/v178/slostar/log1.jpg


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.

[sdminus]

What air fuel meter are you using. Does it correct for egt.

Scott

[slostar]

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.

[sdminus]

Yeah i think it does. I use the LM-1 also. what program is that log displayed in ?

Scott

[slostar]

seems to be a pretty good meter huh. an older vesrion of logworks, theres a later version out on the inovate site.

[mx5]

its not a great deal diffrent, thats probably why i didnt notice it while just watching the guage.

Because adding the water won't change what your lambda meter reads. The lambda will be the same. There is no difference.
So just tune the fuel for your power optimal lambda levels and forget that you have the water (it just works in background helping with cooling and supressing pinging)

[sdminus]

seems to be a pretty good meter huh. an older vesrion of logworks, theres a later version out on the inovate site.

Yeah the LM-1 is the daddy LOL. I have now got a digital egt gauge for my fc datalogit. Shold have a better idea now. (even though i retuned with alch injection)

Scott

[slostar]

sweet.
i just ordered the aux box 3 for my lm1. will get some more logs up with: afr, rpm, map & acceleration, when it arrives




its not a great deal diffrent, thats probably why i didnt notice it while just watching the guage.

Because adding the water won't change what your lambda meter reads. The lambda will be the same. There is no difference.
So just tune the fuel for your power optimal lambda levels and forget that you have the water (it just works in background helping with cooling and supressing pinging)

i know. but the graphs do show a diffrence, even tho they are pretty crap. im not saying water alters the wideband reading, if thats what you mean?

[sdminus]

Which ever way it still deserves looking at. I know afrs can change with your lunch but he does have a point. The afrs do seem to change. hmmmmmm


Scott

[slostar]

did some more runs. nothing much exciting happened
done in 4th gear, ran out of road to rev it right out. wi soild line no wi dotted:
http://img.photobucket.com/albums/v178/slostar/starlet%20ep/Image54541.jpg

theres a bump in the power graph just after wi turns on. (11psi) but that could have just been a bump in the road or something. as power and torque is just done by a calculation of g's, rpm, weight etc..

need to play with the afr some more see what happens



comments?

[sdminus]

To me it looks like the AFR's are stable ish. There is very little differance between WI and none. I would expect this sort of deviation between runs on the same set up so i think on this run we can say wi does not affect AFR.

Im very interested in the Bump in the graph. It apears to have a big rise in power. There is no boost spike there tho or anything odd about the rpms. You also see a increase in the G,s so its defo going better. I presume this is the water on point but why does it do this.

What are you using for your water injection ?

Scott :?:

[slostar]

yeh im interested in the "bump" on the graph also. will do few more runs to back it up when i get a chance.

its just a single stage setup. mostly a coolingmist kit. switching it through my boost controller at the moment. its probably around 20% water vs fuel when it comes on. could explain the bump.
temped to try more water and switch it on later, probably using injector d/c. as its prone to detonation just after 6000rpm. you can see it on the graph where the boost jumps up half a psi or so

[sdminus]

Is there any differance in you water injection map and your non water intected map ?

I wonder if what we are seeing is a change in egt.

Scott

[slostar]

same map, runs were done within 5mins of each other on same part of the road. good point. might try sort out a probe to log egt as well

[slostar]

same again, but changed to a bigger jet. seems to loose 4-5 hp right through the rev range after the wi is activated. got the sligtest det at one point in the rev range, on the run with no wi. pretty cold out there witch would explain the extra boost and power over the last graph

afr is doing its own thing as usual...

http://img.photobucket.com/albums/v178/slostar/starlet%20ep/Image545419.jpg

not sure what to try next. might try drop the afr back down to 11.8 or so, see what effect it has. not too keen to go any leaner than what it is.

[sdminus]

I would expect to see a drop in power by that amount. I would be tempted to get an egt and log that before i try much more.

Scott.

I wonder if this datalogs from FC datalogit will work on logworks ?

Scott

[sleeper7]

old thread but trying to bring it back

Currently running two M5 (5gph at 100psi) nozzles and a 150psi shurflo pump. controller starts at 3psi and full at 25psi.

My AFRs are in the low 10s and EGT is max at 675c. Timeing is 20btdc at 1.5 bar.

http://www.putfile.com/sleeper7 short incar video

Two options to get the EGTs up. #1, retard the timing and see if this helps. #2, lean the map out.
opinions?

[Richard L]

Option 1 will loose power for sure.
Option 2 is much better but ensure you have a good failsafe system. I believe coolingmist has a failsafe (block jet) you can purchase as an add-on?

[markbudgen]

Hi all,

I get a similar effect which maybe a wide band measurement effect from a cooled exhaust. Here's a picture of the effect in my car.

BR, Mark.

http://upload8.postimage.org/974259/20_6_7v215C.jpg (http://upload8.postimage.org/974259/photo_hosting.html)