Weather station ET predictor suggestions

[btrc]

Mike,
What do you use for the comparison base. DA, ALT A, Barometric pressure, ??

[Mike Fuller]

The system that I had asked for Pressure altitude dry bulb temp and wet bulb temp. It would put out a corrected altitude. Then you could ask it for a ET prediction based an a previous run and those three inputs. Was very close usually.

[Larry Hill]

Does anyone have a NOVA weather station for sale?

[cad]

I use Computech RaceAir handheld. I have 11 No Box/PRO ET championships with it.

My pit partner also uses Computech but it interfaces to Crew Chief Pro. He also has a couple of Championships with it.

I like the handheld, as it is mobile, and important if there are long delays while in staging.

You choose the best, recent run as your baseline using Correction Factor or DA, and then the current factor to predict your next ET.

If your combo is jetted correctly and the AFR is close to optimum (12.7-12.9 in my case), it will run within .005.

Jay/Computech answers the phone on the weekends, also.

I would also recommend DragStat ($ vs $$$) for your laptop. Created by a NHRA Super class racer (and D5 champ) out of Colorado. He also answers the phone for tech support.

Clark Doukas

[cad]

Originally Posted by Darrel Goheen

Do you use a different data file for each track?

My buddy does use a unique database for each track.

[Altronics]

Originally Posted by FireSale

I have a PerformAIRE Eclipse, which a lot of my fellow racers swear by but I swear at. I routinely run 0.2-0.3 under the devices prediction.

Here are the predictions and my ETs from last Sunday:
13.18/12.858
13.14/12.835
13.146/12.817

I burned hours trying to come up with a number to subtract from the machine for my dial, but If I had ignored it and paid more attention to the free time slip I would have just dialed 12.80.

We invented and have been manufacturing PerformAIRE weather stations for 25 years. I don't think we would have been doing it this long if our systems were not capable of working correctly.

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.

Per our instructions: You need to have at least 1000' change in DA across 5 to 6 runs in order to generally get a good prediction. Entering 2 or 3 runs with only a few hundred feet change in DA will generally NOT give a good prediction.


We are always happy to take a look at your data and try to help you. You are free to email us directly with the run information you are trying to use, or if you like post it here and I will comment on it.

[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.
.

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..