Car picked up Sat. when I really didn't expect it to.
60 ft 1.429 1.425 1.424
330 ft 4.248 4.249 4.238
660 ft 6.665 6.669 6.649
MPH 101.561 101.292 102.117
Temp 66.6 68.8 69.0
Humidty 51.1 38.7 37.5
Baro 29.00 28.98 28.98
DA 1702 1840 1850
GPP 51.2 41.7 40.7
3000lb no box car 355 SBC glide 5.13 gears launch at 3k shift at 6200 Stage temp 170 every pass Rupert 750 alcohol carb jetted 144 square no power valves.This message has been edited. Last edited by: Eman,
Staging at same temp?
Did they drag the track just before you ran or spray it?
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I know with injection going from 150 to 180 can pick you up almost .05 if system is s little too rich.
Have always tried to stage injected alky at 150 to 160. Reason I mention injection is I have no idea if carb responds the same
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Real careful about staging temps, staged at 170 I have a 165 thermostat in the motor. I watch to see it open and then the temp goes to 170.
Didn't drag or spray the track and the 60's are within .005. I did the split times it picks up .01 between the 60 and 330 and then another .01 from the 330 to the 660.
take the thermostat out, they are notorious for sticking and you won't see it on the temp gauge. work the temp with the waterpump and fan
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Thermostat has 3 holes drilled around the perimeter so water circulates open or closed. I can run the WP with the cap off cold and see the circulation.
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Your weather data gives nearly the same Correction Factor for methanol for the three laps; 1.0593, 1.0590, 1.0588. My little ET predictor spreadsheet shows 6.664 for Laps 2 and 3.
Other than a 10mph+ tailwind (doubtful), what were the trans temps for laps 2 and 3? If Lap 3 was 30-40* hotter than Lap 1 or 2, that's an easy .01-.015.
I'm not sure I'd expect 2 numbers from methanol carb jetting on the lean side due to 0.2 degrees ambient temp rise.
How many other cars broke out that round?
Maybe the track came around from Lap 1 to Lap 3.
Don’t overlook oil temperature. Best thing I did was adding an oil temp gauge to my dash.
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home brew 582 BBC Dart 355
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Do you have the time stamps from the slips?
How many minutes between Pass 1 to 2, and Pass 2 to 3? Short turnaround / hot-lapping, with a few minutes of heat soak between, can pick mine up .01 compared to a "normal" interval as in earlier rounds. If there is an oil down or other lengthy delay, I slow .01 or more. I have always attributed it mostly to fluid temps, (engine oil, trans, diff). Assuming little/no change to DA.
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You didn't post all the info but my take is your 2nd run is the bad one, it should have went faster! Your DA's are meaningless here, humidity is the driving factor!
Time between runs,
First run 1:39 PM second 3:34 third 4:57 all runs in the same lane.
Trans temp between 125 and 150. Don't have an engine oil temp gauge yet.
Top 38, what other info? Tell me why 2nd should have picked up?, is it because of GPP of water? Is this an indication I'm too lean?
I went back and added MPH to original postThis message has been edited. Last edited by: Eman,
Big humidity drop between the two I believe is what he is referring to. The GOW dropped 11 between 1st and 2nd.
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What Gauge are you using ? Air Density online showed the DA to be 1685 at 2:30 1350’ at 5:30 when I made a pass. Also showed the Humidity only moving from 62 highest to 52 lowest then started going back up. Lean will make throw out crazy runs. A least it does on my injection and I can’t see a carb being any different. Friday DA was 3200 to 2700 and Saturday 1685 to 941 last pass I made. Not sure Air Density online is correct but my car follows the air change from it
how much did the track cool
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1.036, 6.16@ 224
Some good comments in here, time between rounds even though engine temp may be the same heat soak mine will go quicker.
You need to look at all the weather factors and look at what makes your combo move.
Play around with a spread sheet
Its completely different to what you guys call gasoline
Forget looking at humidity as that number changes with temperature so its useless.
You need to look at vapour pressure or water grains, and other things, forget all about density altitude
But very important is the tune up for the given conditions.
How do you know where you are?
You need to learn how to read a methanol spark plug if you don't already.
A bit on the fatter side of the tuning window will be more consistent
the leaner side will throw you curve balls every now and again.
i'd have a 180 t/stat for methanol and stage at 180.
And don't forget about wind or you the driver,
Are you hitting shift points the same etc
But to answer your question what makes it pickup.
if it picks up when the air has gone off, your probably on the lean side,
if it picks up hugely as the air improves then you may be a bit fat.
A carb won't be as consistent as injection but if the tuneup is correct it will be just as predictable so long as everything else with the car and driver is on the moneyThis message has been edited. Last edited by: Paul Dilley,
I guess I don’t monitor enough fluid temps on my car. The only thing I do is pull into the water box at 150 with the water pump on. No oil temp no trans temp. I double it and loose and start single 2 hours or 15 minutes between rounds doesn’t phase the ET if I have the tune right it’s deadly. Driver just sucks 99.9% of the time.
I use a Kestrel 5100 I hang up and it's out of the sun.
I guess what really puzzled me and Top38 said it, 2nd pass should have picked up if the car was following the weather.
I'm just trying to get a little better handle on it and the car surprised me when it picked up The car has been very consistent on alky. Most seem to have higher jetting than I do so I was wondering if I am too lean.
The weather front moved through Friday night and it rained really hard all night. The cold front moved in and dried everything out so it was getting better as the day went on.
I have a Rupert alky carb built for a 355 and it came with 150 jets.
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