air - fuel mixture when running track days and H2O tuning?

[d15b7]

hi fellas!

my car is a 2003 Mitsu EVO. stock, with exception of turbo back straight exhaust. computer is stock, no boost controller. i have a HKS Super AFR, which is currently set to all zeros. on a wideband, the car runs very rich, stock. it shows ratios of 10.1 and 10.2 to 1! we get 93 octane fuel here on the east coast, so that is what i use.

i have just finished construction of my homemade water injection system. i'm using the shurflow 100 psi pump and a 6.4 gph nozzle. i have the pressure switch set for about 12 psi. btw, stock EVOS run boost of up to 19.5psi, and gently tail down to about 17 psi at redline....

my main question is:

a trackday is coming up for me (i'm an instructor for the PCA, BMW CCA, Ferrari Club, etc.) and i' like to take my EVO for one of the three days, just to "see what she can do" :)

i'd like to tune the fuel mixture beforehand; i was thinking of tuning it to about 11.5:1 from 4000 rpm up to 7000 rpm; i was planning on doing the tuning without the water injection. when at the track, i would of course run the water injection as a matter of increased "safety" (knock resistance, EGTs, etc.).

does this seem like a reasonable air-fuel target? most of the guys with tuned up EVOS (more boost, etc.) run around 11.5 to 1. but they are either drag racing or just driving around. this will be track duty; 25 minutes of HARD driving....

i don't have any access to any other diagnostic equipment, such as a knock meter, etc. all i have is a good wide band O2, you guys, and the seat of my pants!

just looking for some good input!

thank you in advance.

todd
d15b7@aol.com

[Charged Performance]

The original section was meant to discuss mixtures of water with other coolants like methanol. I am moving to a better matched section.

That is quite a bit of water from a static flow potential system, to use for a layer of det suppression safety. You may find that it bogs your engine down without some additional fuel or timing work.

A static flow system will inject more water per intake stroke at the point that it engages than it does at redline. And the differential in water weight per intake stroke is greater than the higher load the engine is under in the midrange.

To address this without complicating your system I would consider a smaller jet if you aren't planning on tuning your fuel leaner than you are considering. 5gph is about as much as I would consider based on your discussion so far.

I would look to start the injection at about 10 psi.

Your engine will bog at the lower end of the range will likely bog down some. Advance the timing a degree or two in the lower range first. Then reduce fueling until the engine no longer bogs down at the lower end.

Work your way up the rpm range in this manner.

I wouldn't be surprised if your fueling looks something along the lines of 12.5:1 at the point of engagement tapering down 11.5:1 at red line.

If you only reduce fuel to the point where it is not bogging down any longer you should still be a far way from det. With det cans you would likely find you could lean out a another half point of AFR even and get some more power prior to hearing any det.

[d15b7]

thank you very much for the reply!

you are absolutely right; i was out tuning last night, up and down rt 273 with the wideband and my HKS Super AFR.....

i leaned it out to a fairly steady 11.3 to 11.5 AFR from 4000 to 7000 (without the water). feels super strong now; really strong.

with the water engaged, it definitely feels "softer"; doesn't pull nearly as aggressively. that nozzle is too big (the 6.39 gph nozzle, which is rated that at 40 psi, and i am running a 100 psi pump).

this morning, i ordered two more nozzles; a 4.4 and a 3.1. will try those out soon!

thanx again!

todd

[boostm3]

On my '99 M3, with a 3.2l 10.5 static CR engine, IM running a Vortech supercharger (centrifugal) making 11 psi boost at redline.. And, Im running no intercooler, at the moment. That will soon be rectified, but for the purposes of this discussion, assume no intercooler.

AFRs are in the 11-13:1 range. No knock has been evident.. Intake Air Temperatures while cruising, since there is no intercooler, and since its before the water injection triggers, are high... Generally about ambient plus 70-80 degrees. If Im doing a WOT run, I will typicvally see my IAT values near 175 degrees at the beginning of the run, which will drop to near 115 degrees at redline, which is 7000 rpms!

Im using a .8mm jet. Now.... I used to trigger at 4 psi, which its around 4000 rpms. Recently, Ive found that I can trigger this nozzle at about 2.75 - 3 psi, which hits around 3000-3300 rpms, and NOT experience any stumble or stutter, at least, that I can feel.

So, Im wondering, is there any reason I shouldnt be triggering so early? Since I perceive no fall off in performance when it triggers, I ve thought that the best place for me to trigger, since I have no intercooler would be as early as possible. On my car, Timing is strongly effected by the IAT sensor. So I feel its to my advantage to trigger early.

There is a good water to air aftercooler unit which should add about 20-25 whp to my current setup... The aftercooler has been instrumented to show that where my IAT value are in the 170s during cruising, they will be near 110, and with the combo of the aftercooler Plus my water injection, they will be in the mid 90s in summer weather. When I install the aftercooler, I will raise the trigger point to around 6 psi, as I dont believe I will continue to need it to lower my IATs at lower rpm levels, and will instead use it to suppress knock, which, because my injectors are near max above 6500 rpms. Still, they currently are able to sustain a 13:1 ratio at redline. Everywhere below redline, its in the 11s and 12s.

Does this sound reasonable?

[Charged Performance]

Turbo engines usually have a low static CR and run up to significantly higher boost levels. They can and should use higher boost triggers as a result. 8-10 psi on a static CR of around 8.5 is usually where detonation just becomes a concern.

SC engines, especially those with higher static CR, will hit detonation at much lower boost levels. Triggering at boost onset or at very low boost is necessary and appropriate. If you are not experiencing any bogging your boost trigger setting and it is pulling hard through the range you are likely in good shape.

And yes relying solely on WI to cool the charge (no IC) also reduces the desired trigger point.

[d15b7]

hi fellas!

just got back from the track weekend; car ran superbly, and it was hot hot hot out here on the east coast -- over 85 degrees on sunday.

i ended up tuning it for what i considered "very safe". without the water engaged, i had A/F from 4000 to 7000 rpm typically 11.5 tapering to 11.0. with the water, 10.8 down to 10.0. the addition of the water seems to really make the wideband see almost a point richer condition.

i ended up using a much smaller nozzle, rated for 1.9 gph at 40 psi; i was driving it at 100 psi, so i am not really sure how much it was flowing above 1.9 gph. i had the activation point set for 11 psi. no bogging was evident anywhere; that i can say for sure. i was using about 3 liters of straight water every 25 minutes or so of tracktime. fuel was 93 octane pump gas.

observable results were the following: car seemed to pull the same in the morning (60 degrees ambient) as it did in the afternoon runs (85 ambient, and a very hot track temp surface, maybe 120 or so). i have no boost controller, so the oem computer is in charge of that. i never saw or felt it pull boost, which it does if it sees detonation. i am fairly certian detonation was not occuring....

next step is to really tune it a little more aggressively for power; i just wonder how to go about that; should i tune with the water engaged and shoot for an A/F of about 11.5? then go and do some more torture testing at the raceway and see if boost is pulled, etc?

so far, i am very please with the results!

thank you all for the help.

todd

ps as a side benefit, it seemed to get much better fuel economy than i expected on track. i thought it would be around 8 mpg; was doing about 12 mpg.....