Weather station ET predictor suggestions

[Rob Wright]

Originally Posted by Altronics

In order for any car to be predictable with any weather system the car must be repeatable and jetted correctly to respond to air change. If your car will NOT run the same 60' (+/0.002) and ET(+/-0.005) on back to back runs in the with the same DA (+/-100DA), it will never be more predictable then its best back to back run.

Also very important is the Data you enter. Garbage in Garbage out.
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Gospel word on both points.

Sorry if this seems like a hijack, but one thing I see quite regularly, and it undoubtedly impacts ET consistency, is engine tuning with wide-band sensors in the header collector, and no turn-down elbows or extensions.

More often than not the collector-mounted sensor gives a false reading that shows significantly leaner than the engine is actually running at.

If you look at the attached picture, you can clearly see the collector sensor is reading much-much leaner than the sensors in each primary, mounted about 10" from the header flange.

For EFI guys, the open collector & free-flowing back pulses are causing the control sensor (in the collector) to chase all over the place while trying to hold the A/F to target. There is absolutely nothing wrong with the EFI system, it is doing what it was commanded to do. In this case the exhaust & sensor locations are the problem, so much so that the EFI AFR Target had to be set to 13.9:1 in order to achieve an actual 12.25:1 ratio.

Again, sorry if this seems like a hijack, but I had to chime in because running pig-fat on fuel is likely to cause inconsistencies that a weather station & ET predictor cannot account for.

[FireSale]

Originally Posted by Rob Wright

Gospel word on both points.

Sorry if this seems like a hijack, but one thing I see quite regularly, and it undoubtedly impacts ET consistency, is engine tuning with wide-band sensors in the header collector, and no turn-down elbows or extensions.

More often than not the collector-mounted sensor gives a false reading that shows significantly leaner than the engine is actually running at.

If you look at the attached picture, you can clearly see the collector sensor is reading much-much leaner than the sensors in each primary, mounted about 10" from the header flange.

For EFI guys, the open collector & free-flowing back pulses are causing the control sensor (in the collector) to chase all over the place while trying to hold the A/F to target. There is absolutely nothing wrong with the EFI system, it is doing what it was commanded to do. In this case the exhaust & sensor locations are the problem, so much so that the EFI AFR Target had to be set to 13.9:1 in order to achieve an actual 12.25:1 ratio.

Again, sorry if this seems like a hijack, but I had to chime in because running pig-fat on fuel is likely to cause inconsistencies that a weather station & ET predictor cannot account for.

Rob, I will agree on all of this. My af sensor is too close to the exit of my collector (sbf carburetor) and my readings never make sense as they are too lean. I'm going to add an Altronics O2 Alert, keep the current system in place and install the new one closer to the header port. Then I can compare the too. The O2 Alert will log rpm and a/f ratio which my current system won't. It has an rpm trigger, too. Carb tuning is most of the issue here. the weather data from the Eclipse is accurate.and switching to One Run Predict has helped.
DA in the Seattle area can vary from 1963 to 3496 in the same weekend. Happened at the LOD race at Pacific Raceway..