Tampa 928s

Looking at my chart it seems like at the tail end “high boost high rpm”, it is going very lean but I am not sure if this is indicative of the chart. This maybe the backing off or delay on the chart when letting off the gas.

It always comes back to shark tuning or the lack of! Now when someone is ready to loan rent or otherwise provide one my option is Mega Squirt-3.

Any chart readers care to chime in?






Time A/F Rpm Maf Inj Duty Boost Acell

233.636 14.89 1870 3.8 18.1 -2.76 1.977
233.718 14.67 1930 3.81 18.7 -2.72 1.977
233.8 14.63 1980 3.82 19.4 -2.72 1.977
233.882 14.99 2040 3.82 19.7 -2.72 1.977
233.964 15.11 2090 3.81 20.2 -2.72 1.977
234.045 15.1 2150 3.87 20.7 -2.76 1.977
234.127 14.82 2200 3.93 21.3 -2.8 1.977
234.209 14.67 2260 3.93 21.6 -2.89 1.977
234.291 15.1 2320 3.94 22 -2.97 1.977
234.373 15.19 2370 3.94 22.7 -3.1 1.977
234.455 14.63 2420 3.94 23.5 -3.23 1.977
234.537 14.49 2480 3.96 23.8 -3.41 1.977
234.619 14.73 2540 3.97 24.1 -3.58 1.977
234.701 14.85 2600 3.99 24.4 -3.75 1.977
234.783 14.96 2650 4 24.8 -3.92 1.977
234.865 14.79 2710 4.03 25.4 -4.1 1.977
234.947 14.44 2760 4.04 26.1 -4.27 1.977
235.028 14.88 2810 4.06 26.2 -4.4 1.977
235.11 14.82 2860 4.06 26.3 -4.57 1.977
235.192 14.98 2910 4.07 26 -4.61 1.977
235.274 15.26 2950 4.07 25.8 -4.7 1.977
235.356 14.64 3000 4.07 26.3 -4.74 1.977
235.438 14.45 3050 4.07 26.9 -4.79 1.977
235.52 15.08 3090 4.1 27.1 -4.79 1.922
235.602 14.82 3130 4.13 27.3 -4.79 1.867
235.684 14.3 3190 4.11 27.9 -4.74 1.922
235.766 14.58 3240 4.09 28.4 -4.7 1.977
235.848 15.24 3280 4.09 28.5 -4.61 1.824
235.93 14.96 3310 4.08 28.6 -4.57 1.668
236.012 14.73 3370 4.09 29.7 -4.53 1.824
236.093 14.32 3430 4.09 30.8 -4.48 1.977
236.175 14.55 3470 4.17 30.7 -4.48 1.945
236.257 14.98 3510 4.25 30.6 -4.48 1.914
236.339 14.66 3570 4.26 31.7 -4.44 1.945
236.421 13.95 3620 4.28 32.8 -4.44 1.977
236.503 13.58 3670 4.31 33.9 -4.4 1.977
236.585 13.48 3720 4.33 35 -4.4 1.977
236.667 13.39 3770 4.29 36 -4.4 1.977
236.749 13.33 3820 4.26 37 -4.44 1.977
236.831 13.23 3870 4.32 38.1 -4.44 1.883
236.913 12.94 3920 4.39 39.3 -4.44 1.789
236.995 12.95 3980 4.37 40.3 -4.44 1.883
237.076 13.22 4030 4.35 41.3 -4.44 1.977
237.158 13.42 4090 4.42 42.5 -4.35 1.977
237.24 13.23 4140 4.48 43.9 -4.31 1.977
237.322 13.42 4210 4.58 46.1 -4.18 1.977
237.404 12.97 4270 4.68 48.4 -4.05 1.977
237.486 12.92 4340 4.81 52.3 -3.71 1.977
237.568 13.08 4400 4.93 56.3 -3.41 1.977
237.65 12.16 4490 5.03 62.2 -2.85 1.977
237.732 12.04 4570 5.13 68 -2.28 1.977
237.814 12.01 4680 5.16 72.1 -1.6 1.977
237.896 11.79 4790 5.19 76.3 -0.91 1.977
237.978 12.1 4940 5.21 78.8 -0.43 1.973
238.06 12.27 5090 5.23 81.3 0 1.969
238.141 12 5110 5.16 80.1 0.13 1.973
238.223 11.94 5120 5.09 78.8 0.26 1.977
238.305 11.92 5189 5.1 78.2 0.13 1.977
238.387 11.98 5249 5.1 77.7 0 1.977
238.469 12.05 5339 5.37 82.7 0.09 1.98
238.551 11.92 5419 5.65 87.7 0.17 1.98
238.633 12.83 5539 5.67 90.4 0.99 1.98
238.715 12.58 5659 5.68 93.2 1.77 1.977
238.797 12.41 5769 5.71 93.7 2.67 1.977
238.879 12.26 5879 5.74 94.3 3.53 1.977
238.961 12.07 5979 5.77 94.5 4.1 1.98
239.043 11.94 6079 5.8 94.7 4.61 1.98
239.124 16.58 6109 5.76 93.6 4.96 1.718 *
239.206 22.39 6129 5.72 92.7 5.3 1.457
239.288 18.49 6209 4.98 86.9 5.3 1.226
239.37 22.39 6280 4.24 81.2 5.3 0.995
239.452 22.39 6159 3.64 63.3 4.22 0.631239.534 22.39 6029 3.04 45.5 3.15 0.268
239.616 22.39 5749 3.11 40.6 1.34 0.315
239.698 22.39 5459 3.17 35.7 -0.52 0.362
239.78 22.39 5140 3.21 29.7 -2.28 0.338

123quattro

I don't think that data is sampled at a high enough rate to really be useful. Looks like you went into decel fuel cut. If you are really worried about it, try and make the tip-out cal less agressive on initially pulling fuel.

AO

Email sent.

But I agree with John. The "tell" is the injector duty cycle is dropping as well as the values from your accelerometer. This tells me you lifted.

Nothing to worry about.

Tampa 928s

That's what I thought, looking at the data log it was right at the apex and yes seemed to be dropping. It was scary looking at the spike going lean so I would like some peace of mind on this.

AO

I now see what is worrying to you... The RPMs continue to climb while AFR drops. Inertia will carry the RPMs up a bit, so don't use that as the measure for when you lifted.

If you want to be certain, you can log the throttle position switch to see when you lifted - but even that may have a slight delay as you have to go from WOT to Cruise to Idle.

dprantl

+1, that is probably you lifting off... it would put it to rest if you logged your throttle position switch. When I log WOT runs, I always delete the rows where the TPS is not 3.

Dan
'91 928GT S/C 475hp/460lb.ft

Tampa 928s

Remember I only have a Data logger not the ability to shark tune. I could possible add the Wot to the log with a bit of work.

Tim Murphy

There is no problem with that log that I can see. Your concern is when you lifted it went lean.... that's what it does. If you were still into the throttle the car would not be happy at all and you wouldn't have to data log it because you would hear and feel it.

What exactly is it that you are having a problem with? You had some high idle issues we discussed, any change in that with removing the teflon tape from the temp-2 sensor threads?

One of the guys here had a comment on your log file.
Here is what he said:

toofast928

Tampa what size injectors are you using?

Tim Murphy

Stock 24lb

He is running a Murf928 Stage 1 kit. This kit uses the stock fuel system with the addition of a Vortech FMU.

FYI, future kits will have the option of running 42lb injectors and no FMU.

toofast928

Tim what max Duty Cycle are you seeing with 42# injectors?
Tony-

Tim Murphy

Depends what car.... Don't know yet on the Stage 1 cars but 80+% on Stage 3 which make just a bit more than 600 CHP.

Tampa 928s

Took it for a drive and during heavy not Wot acceleration I can hear a back fire, maybe a little too rich?
Also I have the surging back when in let's say 3rd gear a heavy acceleration causes a shudder.
Tim suggested this has anyone tried it and if so any feed back?

http://www.saxonpc.com/100mm-cells-for-100.html

Tim Murphy

Is your fuel pressure back to stock now? If not, set it back to stock and leave it there.

You say the surging is back.... did you change something from when there was no surging or did it just show up out of the blue?

Do you still have a high idle after warm up?

Did you take the teflon tape off the temp-2 sensor threads?

My suggestion for the air straightener was for something completely different.

The air straightener idea was for steady state light acceleration surging which I thought you were having issues with but after talking to you that is not the case. The theory, for those following along, is that there is a jet stream created with the Stage 1 plumbing configuration by having 2 bends right after one another. The air straightener (which would act like an intercooler on a Stage 3 car) will stop the swirling air after the first bend. There is a lot more as to why and where it should exactly be placed, based on testing, but that is irrevelent in this discussion.

A "shudder" under hard acceleration sounds more like an ignition problem or perhaps an injector intermittient problem under load. At what rpm are you experiencing this?

Also, a backfire under load suggests that fuel was still getting put in the combusion chamber and the spark went away for a bit. Just like when you drove your dad's Olds to the school dance and you would drive past the school with your foot to the floor and turn the ignition off and then back on again creating a big backfire. Common, you know you did it

Tampa 928s

FP is still 41 not 39.
It was surging once I reinstalled it back in the original location.
Idle is high after warm up 900-950.
Tape is off.
Shudder is consistent it does it while in 3rd 2,200 of so hit the gas not Wot boom.
And yes I like the noise and would love to throw a flame .

Seems like it glitches lean on a couple of spots.

33.833 14.49 2100 3.33 11.4 -9.35
33.915 14.86 2120 3.38 11.9 -9.23
33.997 14.95 2150 3.46 12.5 -9.1
34.079 14.73 2170 3.45 13 -8.92
34.161 14.76 2190 3.51 13.4 -8.75
34.243 14.71 2220 3.48 14.1 -8.62
34.324 14.02 2240 3.49 14.7 -8.45
34.406 13.72 2270 3.44 14.8 -8.36
34.488 14.17 2300 3.41 14.6 -8.28
34.57 14.66 2330 3.49 14.5 -8.28
34.652 14.98 2360 3.38 14.5 -8.28
34.734 15.27 2390 3.5 14.4 -8.28
34.816 15.54 2420 3.48 14.7 -8.32
34.898 14.66 2450 3.49 15.2 -8.36
34.98 14.26 2480 3.58 15.5 -8.36
35.062 14.33 2510 3.55 15.7 -8.41
35.144 14.39 2540 3.58 16.2 -8.45
35.226 14.29 2570 3.54 16.5 -8.45
35.308 14.85 2610 3.5 16.8 -8.45
35.389 15.19 2640 3.64 17.3 -8.41
35.471 14.6 2670 3.69 18.3 -8.32
35.553 14.44 2710 3.7 18.9 -8.23
35.635 14.49 2740 3.7 19.3 -8.15
35.717 14.88 2780 3.67 19.4 -8.06
35.799 14.99 2820 3.65 19.8 -7.98
35.881 14.42 2850 3.71 20.4 -7.89
35.963 14.41 2890 3.76 20.8 -7.8
36.045 14.85 2930 3.73 20.8 -7.72
36.127 15.11 2970 3.71 21 -7.59
36.209 14.74 3010 3.84 21.6 -7.5
36.291 14.54 3050 3.77 21.9 -7.46
36.372 15.05 3080 3.76 21.8 -7.37
36.454 15.08 3120 3.8 21.9 -7.33
36.536 14.63 3170 3.68 22.5 -7.29
36.618 14.54 3210 3.77 22.5 -7.24