gesTTalt

I used an <a href="http://home.earthlink.net/~cogent001/vw/air_fuel_EXAMPLE.xls"> excel sheet, created by John S </a> (corrected to 225 engine) to come up with these numbers. This was a run I did a while ago with my DBR/MTM chip. I plan doing a few other things that would require retuning.

Boost Pressures (Max boost is at 27 psi, and the settle nicely to 23 psi where it then tapers - as seen on the graph)
<img src="http://public.westcoasttt.com/gesttalt/vag_runs/image001.gif">

A/F Ratio and Injector Duty
<img src="http://public.westcoasttt.com/gesttalt/vag_runs/ACF18FF.gif">

Looking at the graphs, it seems that I'm running a little lean. However, when I look at the exhaust pipes, O2 sensors and plugs, they appear clean (no white residue).

What are your impressions? Do you think our injectors will be able to handle a 5 bar fpr (with retunining of course)? IF I can't get it retuned, what would happen if I ran a 5 bar fpr? Am I working the injectors too hard?

john s

Change 145 in I5 to 179. If you're running higher than stock fuel pressure then append
*sqrt(x/3)
to the cell where x is the differential pressure of the regulator in units of Bar.

The numbers you're charting are lean, new numbers will be richer.

gesTTalt

thanks John, I'll append the sheet and rerun the numbers.

gesTTalt

not exactly sure which variable I would append with the *sqrt(x/3)? is that to the adj constant?

TTschwing

Just pulling Lambda factors off the vag (block 217) and converting to A/F .....or am I missing something?

A/F lambda
17.0:1 1.16
16.0:1 1.09
15.5:1 1.05
15.0:1 1.02
14.7:1 1
14.6:1 0.99
14.5:1 0.99
14.2:1 0.97
13.2:1 0.90
12.5:1 0.85

gesTTalt

air flow. Plus, as noted by John, I can estimate what a 5 bar fpr will do to the system (which I'm still trying to figure out from what John wrote).

sTTanford

Air/fuel right, so higher means leaner. stoichiometric at 14.7, and typically you wanna run at an equivalence ratio of 1.2~1.3 for WOT. when im on the dyno tuning and AFR creeps past 13 it is time to hit the brakes, i keep closer to 10, 11 to be safe.

hm... actually, the excel DATA looks pretty good! the chart looks funny tho, weird.

i'd bet that your pipes look clean because you usually only run rich at higher RPM and/or WOT (and transients, ie let off the gas, etc). if you are a good driver and dont treat the gas pedal as an on/off switch, you probably are runing on the lean side most of the time. do a VAG log at 50% throttle and see what you get! i'd be interested to see that. also, try letting off the throttle halfway thru the run and see how good our ECU is at damping the transient response.

gesTTalt

I used the formulas for the data that I ran for my car. If what you say is true, that I am running rather lean, would uprating the fpr help?

gesTTalt

RPM A/F
1640 13.94
1680 14.71
1800 12.58
2000 12.26
2280 12.50
2680 12.23
3120 13.35
3600 13.62
4040 11.79
4440 10.91
4880 10.63
5240 10.37
5560 9.91
5880 10.00
6160 10.51
6400 10.50
6640 10.55

sTTanford

just throw that puppy in! =) give it a log tho. again, "running lean" isn't a bad thing and is a bit of a misnomer since it implies you are running lean when in reality you are just running less rich.

again, dont really have the motivation to go thru all the calculations done on the excel table (since things aren't labeled well), but the numbers look believable.