Bad TPS?

[Mr Impala]

I've driven it a few times. I’ve also updated the Base Fuel Table with Learn Table a couple times. I don't work anymore so I haven't been able to drive to & from work, so it's running around. I did cut the timing back a little from the last time I drove it, as it pinged/knocked on a full throttle blast until it shifted into second. I'm running 87 octane with about 9.8:1, 64cc iron Chevy heads, 1.94/1.50 valves. I supposed the cam is helping me a little with the little bit of overlap, but I know I'm pushing it.

The Config File and datalog from this morning, run for about 30 seconds and a couple jabs at the throttle was about it. Thanks in advance for checking it out. Kurt

[GPatrick]

After a few weeks of driving, download your Config File and post it here so we can see what your Learn values show. Consistent Learn values tend to show that the system is working well.

[Mr Impala]

GPatrick: Taking your suggestions and putting them into my existing Config File seems to have done the trick. I no longer have any weird datalogs. Nothing on the negative side of time and no lines that I have no idea where they came from. They look normal. Then I routed all wires better, and use Faraday tape on the coil wire and WBO2 sensor wires. Checked the datalog again, and all good. Now I just need to get out and drive it. Thanks again for all of your help. Kurt

[GPatrick]

This Excel spreadsheet allows you to create a Base Timing Table in terms of an old mechanical distributor with vacuum advance. I already modified it for WOT timing of 34°, with basic vacuum advance settings. It's based on a 500 to 6500 RPM range with MAP values from 20 to 105 kPa. You'll have to edit your tables or run the Wizard to get the correct MAP scaling: EFI Timing Table Generator IMPALA .zip. If you'd like to work on this offline, send me a message with your email address and I'll contact you.

[Mr Impala]

GPatrick: Thank you. I was thinking in terms of the old distributor where I'd set the initial timing at 10°-12° BTDC. I forgot about the vacuum advance that needs to be added.

Thanks to this forum. I learn so much. I'll post tomorrow to let you know how it goes. Kurt

[Danny Cabral]

I know how it works, and what happens.

[GPatrick]

This is a plot of TPS RoC % for a pure idle with the exception of a throttle blip at 82 seconds. The scale is -15 to 15. There are a number of excursions above 7 and below -7 that would have kicked it out of Closed Loop with Blanking set at 7. I probably wouldn't set it below 10 based on the noise alone, but would start at 15 and concentrate on the rest of the tune first.

[Danny Cabral]

I didn't know his Blanking value(s) were inhibiting Closed Loop. I thought it was another general Config File question.

[GPatrick]

The biggest problem is that your base fuel table, timing table, and target AFR table are set up with a max MAP of 210 kPa (105 is normal). This won't make it not run but it indicates that the tune is not appropriate for a N/A engine. Your target AFR in the WOT region is 13.6, which is likely lean - unless this was optimized on a dyno. An idle target of 13.9, a cruise of 14.4, and WOT of 12.9 is probably a better starting point. If you run the wizard and enter those values the MAP will be scaled appropriately. Additionally, your MAP scale goes down to zero or 1 in all tables and the lowest MAP value that the Sniper MAP sensor can read is 20 kPa. This will also be corrected with a wizard. When the axes values are above and below the actual operating range for your N/A engine you are losing tuning resolution.

Although the Holley help hasn't been updated your blanking value for TPS at 7 was causing the system to stay out of closed loop as seen in the datalog. When blanking is exceeded the system goes into open loop for a period of time. If it goes above 7 regularly as it is in your log with no throttle input, closed loop didn't kick in until the end of the log. Even engine vibration at idle can cause blanking to be exceeded. 15 works very well in many applications and if necessary it can be slowly reduced if necessary. However, blanking and other enrichment values should not be modified until a solid running tune is achieved.

You have inadequate timing at idle and low timing in the WOT region because the MAP axes are messed up. For your engine an idle of 22 degrees, WOT of 34, and a cruise of 40 should work well.

As mentioned above, it will be easier to correct a wizard tune than to edit the one that you have. All you have to do is keep that file on your computer and on the SD card. If you run the wizard and you hate it, load the current config.

If you run the wizard, post your new config and I can lead you through the creation of a new timing table that will be a much better baseline setup.

Note that in log 17 and 18 you had ECU resets due to EMI/RFI. The other logs did not have EMI/RFI. The backfire is likely due to the reset - the Sniper loses its mind after a reset and it sees odd values and tries to get back into control. This can result in wild momentary timing or fuel changes that are due to faulty data. Look carefully at the log. Look at each parameter one at a time. Note where it was before the reset and note where it is when it restarts at a negative time value.

Your TPS signal is noisy at idle. Try to take a log with the throttle linkage disconnected to see if it is due to vibration. Otherwise, you may need to loosen the TPS and rotate it slightly to find a new zero in case the TPS itself has a bad spot. Are you sharing the TPS signal with a transmission controller? Also make sure you don't have any alternator wiring running near the TPS.

[Mr Impala]

Should the Enable Dwell Table be enabled? If so, 2.0 msec a good starting point? Also, engine-wise, since the ignition has been upgraded, should the gap of the plugs be increased .005 or .010" or. Thanks for the help!

[Danny Cabral]

Change both AE vs TPS & MAP RoC Blanking to "7".

[Mr Impala]

There isn't a starting point for the AE vs MAP Blanking? Any suggestions? Go back 7? 20?

[Danny Cabral]

The Help manual is outdated. That's why I posted the link.

[Mr Impala]

According to the "Help?" in the Holley software, the AE vs TPS RoC Blanking should be, or at least start at 7 and the AE vs MAP RoC Blanking should be/start at 15. My AE vs TPS is/was 7 and the AE vs MAP was 7 and changed to 15. Are those numbers appropriate?

[Danny Cabral]

Read link: The Holley Sniper EFI will intermittently inhibit Closed Loop at idle, if the AE vs TPS/MAP RoC Blanking values are set too low (LINK).