Quote:
Originally Posted by Richard L
Not so long ago, a user of our WI system has lost some 40+ WRHP during a dyno tuning session, not surprise to know that he was quite disappointed. Only after a few months later and have discovered that his engine is tuned to run an a/f ratio of around 10.5:1.
I would really like to hear from anyone if they have suffered the same experience?  |
I thought I would dig this thread up from the grave after experiencing this phenomenon on the dyno last week.
My turbo DSM made about 15AWHP more without WI on the dyno. This was on 91 octane pump gas. I am new to the tuning software ECMLink and had a base tune with 11.1:1 AFR as the target in the WOT load maps for safety while I was getting used to the software. The timing was very aggressive at 21* near the top of the RPM range. The boost was set to 22psi with about 35lbs/min. The WI mixture consisted of 50% methanol and 50% distilled water. Since I have the time now, I went to the dyno to get a baseline so I have something to compare with when I get the car really well tuned.
I attached a dyno plot of all 4 runs for reference, although it is a little hard to decipher the individual runs. I really wanted some WI data, so the 1st run (002) was without WI. It was also a calibration run, so the data is not totally pertinent. There was obvious knock with the ECU taking 3.2* of timing away due to knock.
The 2nd run (003) was with my second nozzle only (larger nozzle). This run made about 288WHP. There was no knock, but the AFR went down to 10.8:1 on my log and even lower than the dyno wideband O2 sensor would read. This run maintained the power further into the RPM range because of knock control.
The 3rd run (004) was with both nozzles (WI at ~15% of total fuel injected). This run had the lowest HP (~282WHP) and lowest TQ. It, of course, also had the richest AFR at about 10.5:1 on my wideband. There was no knock, but power was not maintained into redline, I think, because the mixture was just too rich.
The 4th run (005) was again with no WI and made the most power at 295.8WHP. This one knocked like crazy (ECU took 6* of timing away), causing the power to peak and then drop off quickly.
I know this engine can handle a lean AFR with the WI. My previous tuning method was an air-flow converter, which modified the airflow signal from the MAS throughout the RPM range. I had a custom burned chip, which defined the timing and fuel tables in the ECU, but I fine tuned the AFR and timing with the air-flow converter. It was a constant trade-off, timing vs AFR. I found a sweet spot and ran a 12.8@109 in the quarter mile at about 12.9:1 AFR and 20* of timing on 91 octane gas and the 2 nozzle WI set-up with water/methanol 50/50. So I know with the proper tuning (leaning of the AFR), I can get an even better quarter mile time, and dyno.
So what I learned from this is that there IS such thing as too rich a mixture for WI.
-Craig