I will give that a go next time I make it to the track, which is looking like next season unfortunately.
VPRPWRD's weight reduction thread
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I will give that a go next time I make it to the track, which is looking like next season unfortunately.
I will give that a go next time I make it to the track, which is looking like next season unfortunately.
Do you have an iPhone?
As a matter of fact I just got a 4s.
Download Dynolicious. It's not the drag strip, but I promise it will keep you entertained through the winter.
It's more accurate too.
Its going to depend on each individual truck. I spent one day trying different shift points. I used to shift at 6,000 in each gear, then someone told me to shift at 5,500 and I would run quicker. Well I tried that, and I had to shift to 5th gear to finish the run, and I lost time. But I did not give up. I analized each increment on the time slips ( the intervals between 60' and 330', between 330' and the 1/8th, between the 1/8th and 1,000' and between 1,000' and the 1/4 mile). The only increment that was quicker by short shifting was between 1/8th and 1,000'. Therefore I started shifting at 6,000 between 1-2 and 2-3, the at 5,600 for the 3-4 shift. Now i should say that my truck makes peak horsepower at 5,600, so ideally you want to run just past peak power for optimal results, thats why I say each truck is different. Check your dyno sheet and see where peak hp and torque occur.
I also use a chart where I figure my speed in each gear at 6,000 rpm and what it drops too when shifting to the next higher gear. I can go into this if anyone is interested. Lots of work on a calculator , but its fun.
Definitely interested. I'm not scared of a little calculator work!!
I've built spreadsheets that would calculate and graph this information. I haven't applied it as effectively as you have, but I agree that it is fun.
Fixed it for you
Fixed it for you
It's like you read my mind!
OK , here we go. I'll try to keep this as simple as possible, I hope you follow my reasoning. First you need to know 3 things. 1. transmission ratios (1st=2.66, 2nd=1.78, 3rd=1.30, 4th=1.00), 2. rear end gears (4.10, 4.56, or 4.88 or whatever), 3. rear tire diameter (stock tire 305-40-22=31.5", M&H drag radial 390-40-17=29.5", M&H cheater slick=30") so you can figure the full circumference.
Multiply your tire diameter by 3.1416 to get the circumference in inches. (for example, M&H Cheater...30" x 3.1416 = 94.248")
Next figure your overall gear ration for each gear: In my case 4.56 gears
1st gear 2.66 x 4.56 = 12.1296
2nd gear 1.78 x 4.56 = 8.1168
3rd gear 1.30 x 4.56 = 5.928
4th gear 1.00 x 4.56 = 4.56
Now comes the fun part, to figure your speed in miles per hour per 1,000 rpm in each gear. RPM = revs per minute, times 60 (1hour) = 60,000 revs per hour (this is what your engine will turn at 1,000 rpm in one hour). Now I will work through an example for my truck.
For 1st gear: 60,000 divided by 12.1296 (ratio) = 4,946.57 (revs of the rear tire at 1,000 rpm for 1 hour)
4,946.57 revs x 94.248" = 466,204.3293" ( inches traveled in 1hour).
466,204.3293 divided by 12" = 38,850.36' (feet per hour).
38,850.36 divided by 5,280' = 7.358 miles per hour per 1,000 rpm in 1st gear.
Repeat for each gear : 2nd gear = 10.9957 mph per 1,000
3rd gear = 15.0557 mph per 1,000
4th gear = 19.5723 mph per 1,000
Now lets say I shift out of 1st gear at 6,000rpm, my speed will be (about) 7.358 x 6 = 44.148 mph. Then I divide 44.148 by the speed for 2nd gear (10.9957) and I get 4.015 or approx 4,015 rpm. I know my truck does not drop 2,000 rpm between shifts, because of slippage and other factors, but if I was to just let out the clutch and not be at full throttle then the truck would be doing 44 mph in 2nd gear at 4,000 rpm.....and so on.
Next shift at 6,000 in 2nd gear (10.9957 x 6 = 65.97 mph), 65.97 mph divided by 15.0557 = 4.382 (or 4,382 rpm in 3rd)
Next shift at 6,000 in 3rd gear (15.0557 x 6 = 90.3342 mph), so you can see here that most people are shifting into 4th gear at the 1/8th mile marker (with 4.56's and a shorter than stock tire).
So there you go, .....have fun!
Multiply your tire diameter by 3.1416 to get the circumference in inches. (for example, M&H Cheater...30" x 3.1416 = 94.248")
Next figure your overall gear ration for each gear: In my case 4.56 gears
1st gear 2.66 x 4.56 = 12.1296
2nd gear 1.78 x 4.56 = 8.1168
3rd gear 1.30 x 4.56 = 5.928
4th gear 1.00 x 4.56 = 4.56
Now comes the fun part, to figure your speed in miles per hour per 1,000 rpm in each gear. RPM = revs per minute, times 60 (1hour) = 60,000 revs per hour (this is what your engine will turn at 1,000 rpm in one hour). Now I will work through an example for my truck.
For 1st gear: 60,000 divided by 12.1296 (ratio) = 4,946.57 (revs of the rear tire at 1,000 rpm for 1 hour)
4,946.57 revs x 94.248" = 466,204.3293" ( inches traveled in 1hour).
466,204.3293 divided by 12" = 38,850.36' (feet per hour).
38,850.36 divided by 5,280' = 7.358 miles per hour per 1,000 rpm in 1st gear.
Repeat for each gear : 2nd gear = 10.9957 mph per 1,000
3rd gear = 15.0557 mph per 1,000
4th gear = 19.5723 mph per 1,000
Now lets say I shift out of 1st gear at 6,000rpm, my speed will be (about) 7.358 x 6 = 44.148 mph. Then I divide 44.148 by the speed for 2nd gear (10.9957) and I get 4.015 or approx 4,015 rpm. I know my truck does not drop 2,000 rpm between shifts, because of slippage and other factors, but if I was to just let out the clutch and not be at full throttle then the truck would be doing 44 mph in 2nd gear at 4,000 rpm.....and so on.
Next shift at 6,000 in 2nd gear (10.9957 x 6 = 65.97 mph), 65.97 mph divided by 15.0557 = 4.382 (or 4,382 rpm in 3rd)
Next shift at 6,000 in 3rd gear (15.0557 x 6 = 90.3342 mph), so you can see here that most people are shifting into 4th gear at the 1/8th mile marker (with 4.56's and a shorter than stock tire).
So there you go, .....have fun!
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Sissy
Besides your chart takes tire sizes in metric, what about M&H slicks and cheater slicks measured in inches? Enter that!:dontknow: With my method you can figure things like what will I be doing in 3rd gear at 5750 rpm? etc!
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Sissy
Click the box that says "use tire diameter" then just put 30 for the 30" tires, I used 28. You can also change the rpm of the graph, the default is each 500 rpm but you can change that to any amount you want
I kid!, good find.....but I still will do it my way.:rock:
This is great stuff here. I can't wait to try this out this weekend. One question I have is, would it be beneficial to get a more accurate reading if I actually measured my current tire's outside diameter? The main reason I ask is because I have seen different tire manufacturers same size tires measure significantly different in outside diameter, some times as much as 3/4".
Yes!! It is critical that you measure your actual tire diameter. There can be much more variance than 3/4".
I wouldn't worry about it really, there is no reasonable way to figure it out because the tire grows a little as the speed increases, slicks get a good bit taller
I was thinking about that this morning, actually. The solution is to have Dan ride along in the bed with a tape measure, while we make a couple passes. He can lean over and take measurements as we go.
In all seriousness, I would be curious to know how much a street tire grows. I bet it's less than the difference of the advertised diameter and actual diameter.
Probably depends on tire pressure and sidewall stiffness. Lower pressure and or softer sidewall will equal more tire growth.
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