11.04/121mph with air density = 93%. Been this time before, but only in the best Fall or Spring air when air density was hovering a little above 100%. This year with the CAI and crank trigger it's generally about 0.2sec faster than last year. Also had it to the dyno to tune carb jets and timing earlier this year. Had to richen it up just a tad and back off on the timing. Made 419 RWH uncorrected in typical Summer air. Corrected to standard weather conditions that is 448 RWH. 13.0:1 AFR and 33 degrees timing seems to be what it likes best. When weather conditions change, so does the AFR and horsepower. I can monitor my AFR with my on-board AFR meter and adjust jets to get 13.0:1 if I think weather conditions necessitate it. So far all seems pretty good for summer time racing. I might have to richen up 2 jet sizes towards the end of the season when it gets cold.

As you can see, I don't pay much attention to my shift light. Sound is from the inside of the vehicle.

 

WOW - great. I'm impressed. Real nice work to get these horsepower figures.

I guess that you are already in a league where 10 degrees temperature change already mandate another jet.
And a nice video too.

 

Thank you. I think I'm OK from 70F-95F with current jets. Then in cool Fall weather I'll probably need to go up a couple of jet sizes with the denser cool air.

I think it's interesting that my horsepower can vary around 40, depending on the weather. As far as actual numbers..... It should be making somewhere above 500 at the crank. Figure 20% drivetrain loss from 500 is 400 RWH and I'm above that even at non-optimal weather. But horsepower figures are all dependent on so many things. All I can say is that I make enough to push a 2920# car with 280# driver to right at 11.00@122. Chuck n Truck's supercharged 6.0 is making a little bit more power than mine, but vehicle is heavier (about 3600 + driver I suspect). Result is a very similar time/speed. If he put his on a diet, he would be solidly in the tens. I think he has been bitten by the race bug. I'm really interested to see where he takes it.

 

I love these threads. I've always been into the drag racing, but not enough to go into details... I think it's more of the rush... for me...

but you and chuck are doing really great jobs as to bringing it to the forum. I think you 2 are about the only two I see? Maybe?

 

The performance of any combustion engine is linked to actual atmospheric conditions.
It is air-density that we need to stuff as many oxygen molecules into the engine as possible.

Temperature is inverse to density - the higher the temperature the lower the density, hence the CAI which can add greatly to your HP figures.
Pressure is in line with density - the higher the air pressure at your actual elevation, the higher the density.
Moisture is displacing air molecules - overall it's not soo important but still, everything helps.

I would expect best power (not best times) in winter at very low temperatures, very high pressure and very little relative humidity.
Probably best times are somewhere in between as the track surface should have a minimum temperature to give enough grip to put these HP down on the track.

Dynos usually correct your figures to ISA atmosphere (International Standard Atmosphere) in order to have comparable figures.
IMHO it is far more interesting to compare the ISA corrected to the actual figures. Then you can interpolate your engines gain/loss on HP or carefully extrapolate for other atmospheric conditions.

I'd have to pull the physics books out to calculate the difference but from professional experience any degree higher has the most impact on density and performance as well as pressure and moisture. Aviation has to deal with these effects every single flight.
https://www.aviationsafetymagazine.com/features/humidity-vs-horsepower/#:~:text=This%20means%20that%20if%20dry,humidity%2 0begins%20to%20affect%20horsepower

https://www.dynomitedynamometer.com/...horsepower.htm

What makes me think, that it should be possible to derive the same tables that are available for aircraft under different atmospheric conditions also for cars, including perhaps information about jetting the carbs.

BTW, my guess is that your engine makes a bit more than 500 hp at the crank. The drivetrain losses are quite consistent and you reaction times are as good as they get.

 

Yes, we are agreeing on this.

I asked the dyno operator to send me uncorrected data so I could perform my own correction. I really don't trust calibrations of temp and baro pressure from earlier session and wanted to do my own correction.

I use the following site for air density. I tuned my engine at a density altitude of around 2300 feet (about 94% of standard conditions is typical for my area). It is generally accepted that no jet changes in Holley carbs are required until density altitude changes 2000 feet - then you go up or down 2 jet sizes all around. It's also accepted that 2 jet sizes is the minimum change to make a noticeable difference.

Around here on Winter days with cold, dry, dense air it gets to around zero density altitude. On hottest humid days in Summer, density altitude can get up to around 3500 feet.

So I think I am tuned for center of this and am good for all but the coldest and hottest air.

The prediction of relative horsepower by air density % is the cool thing for me. Oxygen content of the air drives the horsepower up or down. Also why turbos and super chargers can still work well in heat of the Summer.

https://airdensityonline.com/track-h...ay/2020-08-11/

 

A nice Osceola...

Just had a look at the last couple of days. Fortunately the temperatures were down in the 70's, else with 100% humidity HP are down.

So the next step will be fuel injection with baro correction.

 

My track permanently and suddenly closed March 17, 2021. I may be done. Ready to sell it.

Real reason: The neighbors who built houses around the track tied up the sale to a local Top Fuel Driver by suing the Elkhart County Zoning commission, who had approved an expansion of the track at his request. The sale of the track was contingent on the expansion. Then Covid hit and everyone was dragging their feet for a year with no news one way or the other. Then either the owners decided to sell the land to whoever wanted it, I presume because it was easier and could just get done - or the previous buyer bailed and they sold it to whoever wanted it. A local Dairy (farm) company bought it.

https://www.facebook.com/OsceolaDragway/

 

No!! That sucks!!

It was a great read and follow.

Are you going to replace with another hobby?

 

Probably get back into reloading and target shooting. I pretty much gave that up to go racing. But not sure if my shoulders are really up to it anymore. Getting old!