tt061880

Gernby, I went to the track tonight and I have to say that it's kinda hard to predict your 1/4 time. Here's the result of my best run.

r/t 60' 1/8 MPH 1/4 MPH
.000 2.058 8.875 81.47 13.606 101.98


I have no idea why my car has no top end tonight. Everything is the same, the only thing different is that I switched to 5W-20 instead or the old 5W-30 oil. From judging my 60' you would think i'll do at least 8.6x for 1/8 and my MPH for 1/4 should be at least 102. The result is kinda weird compare to all my other runs. My 60' usually in the 2.1x and I still hit 13.6 all day and tonight I hit my best 60' but I only run 13.6, so wierd.

Gernby

iTrader: (1)

It's all a mystery to me, but it looks like you got a REALLY great launch without having much power to take advantage of it. I will continue to wonder what I could have done with a non-slip launch and a longer track.

tt061880

Yah I had no idea where the power went, the car has an intake and the weather was low 60 so it should have trap at least 103.

caymandive

iTrader: (2)

What intake do you have? You were stock when you ran a 13.49@103.8 right?

tt061880

I have the Joez and yes I ran 13.49 without the intake, it was such a big disappoinment last night. BTW this was done on the stock dunlop with 17k miles, I guess the Dunlop isn't that bad at all.

caymandive

iTrader: (2)

Yeah the stock Dunlops have been pretty good for me too. I now have almost 17k on them. I'm sure the decrease in time/mph last night was due to weather conditions. Humidity/temps/pressure, etc.

tt061880

Gernby I'm sorry to hijack your thread, anyway it was 63*F and about 60% humid, i'm not sure about the pressure.

caymandive

iTrader: (2)

I came across an article that explained these 3 variables and thought I would share it with the rest of you. Pretty shocking if I must say so myself. Would never expect that Barometric pressure is the #1 key to fast times. So watch those pressures before hitting the track!

"barometric pressure is number one by a wide margin, temperature is second, and humidity is a distant third.

Barometric pressure is the key to fast times. Barometric pressure is Mother Nature's supercharger; it's the force that pushes air and fuel into the cylinders to fill the low-pressure area created by the downward motion of the pistons. You've undoubtedly heard that Nature abhors a vacuum. Well, it's barometric pressure that fills the void.

If you race on a day with 24 inches of barometric pressure, 60-degree air temperature, and zero humidity, two of the three factors would be perfect - but your race car would still be slow. On the other hand, if the barometer were 32 inches, your car would be incredibly fast even in 90-degree heat and 70 percent humidity.

Engine performance essentially comes down to the number of oxygen molecules that you can pack into the cylinder on each combustion cycle. Barometric pressure does the packing for you. We can also increase the effective pressure by using a hood scoop's ram effect to "supercharge" the air box; it's an effect that can't be duplicated on most engine dynos.

Air temperature, in tandem with barometric pressure, has a direct bearing on air density. Warm air is less dense than cool air and consequently contains fewer oxygen molecules in a given volume. That's why we want our engines to breathe cool air through a scoop rather than heated air from beneath the hood. Temperature does matter: Horsepower increases approximately 1 percent for every 10-degree Fahrenheit reduction in temperature. Savvy racers know that their cars run faster in the cooler air of the late rounds even though the barometer doesn't change significantly.

FULL ARTICLE

Gernby

iTrader: (1)

I didn't realize barometric pressure would be all that significant, but I've always known atmospheric pressure is critical. That's why all the fastest drag strips are near sea level.

Lexmex

Not too long ago I bought my track here in Mexico one of these devices. Actually has a little external sensor, too.

Now, I race at a very high altitude, 7,411 feet at the starting line, but every day when I arrive I check this device to gauge if it is a decent night or not and we let the racers know. A lot of them would moan about times, but this actually reassured them when they realized the heavens above aren't always on our side.

My best nights actually come when we have a low bank of clouds in the area and things get really cool, high pressure, low humidity and low temperatures.

caymandive

iTrader: (2)

Lex,.. that is a really cool device you got there.

Gernby

iTrader: (1)

Just an FYI to let you guys know that I went out to the 1/4 mile track yesterday, and started a new thread about it here. FWIW, my prediction in the 1st post above was pretty close since I got a 13.251 @ 105.34.

phatboyc

Can't we let our hoods partially open from the interior latch and let the manual hood release hold it. This would cause a ram effect strait to the air inlet. Anyone tried? Is this dangerous of the hood releasing? I heard in the past some Porche guys did this to overcome their engine over heating.

Gernby

iTrader: (1)

I think that would have a more negative effect than anything, and would be dangerous. The stock airbox is already getting air from the high pressure area in front of the radiator. By popping up the hood, that pressurized air would be allowed to flow over the radiator instead of through it.

The Porsche guys were doing something totally different. They were air cooled rear engines. They were probably just altering the hinges of their engine cover to channel more air down across the block.

phatboyc

I see. Here is another crazy idea then. To rap your JoeZ pipe in some sort of heat insulator. I know the metal vs plastic inlet pipe has been discussed before. But some sort of fiberglass insulator sure couldn't hurt. Even if it's just when your engine is idling on the line and producing allot of heat. It would prevent the pipe to get to hot and in return get cooled quicker after take off. Right?

I see you guys removing your engine covers. Is this only to allow the cool down of the engines between runs? According to Lexus these are for proper air flow in the engine compartment. Notice any difference with it on/off for you run?