SC'd 03 Vette, 80# injectors, Greg's data; any experience lean spot at 2.7 ms?

[mowton]

Using Greg's data on the 80# Cobra injectors on a SC'd 2003 Vette, I am experiencing a lean tip-in event, only on transition from stop to go and with very light steady state throttle depression (APP% approximately 15%). Once you are under way and through this area, other transients are OK (i.e cruise at 20 mph and accelerate to 30). Idles great. Injector pulse width is about 2.4/2.5 ms at idle/in-gear (A4) and during tip-in event, begins to rise to 2.6-2.8 where lean (>15 AFR) event ocurr. Once you get to about 3 ms. all is back to Stoich and behaving as designed.

I did see some very small values (much less than the .0152 resolution of the 2003 PCM) in the small pulse adder at the PW time's where I am experiencing the issue. All area's around these 3 or 4 values are zero (to 5 places!) which led me to think there is a phenomenum with these injectors linearity at those specific points. Today I am going to update those area's with increments of .0152 to see if it corrects the problem.

Any one else seen anything like this? I searched the forum but came up with nothing.

Thanks

Ed M

[joecar]

Ed, let us know how you go with the SPA increments.

[5.7ute]

Ed, let us know how you go with the SPA increments.

X2
Ed do you have a flow v time chart like the attached on your injectors? Something like that will help you visualize if the problem you are having is due to small pulse offsets or if it is an issue elsewhere in the tune.

[mowton]

X2
Ed do you have a flow v time chart like the attached on your injectors? Something like that will help you visualize if the problem you are having is due to small pulse offsets or if it is an issue elsewhere in the tune.

Not sure what you are referring to as far as the chart? You say attached, but I don't see one. Didn't get a chance to work at it today, hopefully tomorrow.

The interesting thing here is Gregs SPA tables for these injectors go to zero and then a value and back to zero again, per the attached.

Thanks for the look :cheers:

Ed M

Update -- I see it now. I assume the SPA defines the non-linearity of the injectors in tabular form.

[5.7ute]

Should be there now.
Make sure you check the values that correspond with your PW minus the battery offset & SPA contribution if applicable. IBPW appears to be a total PW.

[mowton]

An update, the roads in the Northeast are still pretty bad, so may not get the car out til the end of the week.

One additional bit of data I didn't submit......event happens in both open loop MAF and VE

[bobbycollier]

What injectors were you running before these and did you have a similar problem? What OS are you running and are you using fuel trims or speed density? I have problems with my injectors at times, but it seems to be voltage related (charging issue due ???). Perhaps the injector tables are fine but you have something else going on like VE issue?

[mowton]

What injectors were you running before these and did you have a similar problem? What OS are you running and are you using fuel trims or speed density? I have problems with my injectors at times, but it seems to be voltage related (charging issue due ???). Perhaps the injector tables are fine but you have something else going on like VE issue?

Unfortunately I am commiting the one thing that irks me and that is asking for help and not coming back with any new data, but other priorities (cars being picked up) have put this project on the back burner. When I left the shop, the car was strapped to the Dyno for a Monday start.

As far as the original injectors and running condition, I am not sure as the car came in when I wasn't there. I will ask. It was a car which was built by someone else and brought to the shop to help fix the FU's. It is now a 2 BAR EFILive Custom OS (but as I said above, it did it with the stock 1 bar as well). The car is being tuned in Speed Density.

The more I look at the numerous logs, the more I may be shying away from the 2.7 ms tip-in theory. It appears to be a light throttle (APP% 15, 1400 RPM, 70 kPa, 2.7 ms IPW) where the AFR goes to 18 (from the commanded 14). The good news it can only be 3 things....air, fuel or spark :grin: Hopefully we will have more info this week. Again sorry for starting this and dragging out the project.

Ed M