wazzurp

I have a question for those with an AP1 with 4.77.

Does anyone know the top speeds per gear. I know with the stock gears you get to 60 before needing to shift into 3rd


1st gear
2nd gear
3rd gear
4th gear
5th gear

Thanks

negcamber

Gear Calculator:

http://www.turnzero.com/technical_resource...gear_calculator

wazzurp

Thanks Man,

It says top speed with 4.77 would be 141 in an AP1 I thought it would be less.

Krenath

Interesting...

The values that come out of the TurnZero.com calculator don't match up with other sites (such as http://www.fatboyraceworks.com/gears/index.php ).

Supposedly, MPH = RPM * TireO.D. * .002975 / GearRatio * DiffRatio

(the number .002975 is the conversion between inches and miles, the conversion between minutes and hours, and the conversion from tire diameter to tire circumference all multiplied together... * 60 / 12 / 5280 * 3.14159265 )

According to that calculator, several other gear ratio calculator pages, and my own excel spreadhseet based on that formula:

With 4.1 (stock) gears, top speed of an AP2 should be 192.23 MPH
With 4.1 (stock) gears, top speed of an AP1 should be 199.02 MPH

With 4.77 gears, top speed of an AP2 should be 171.07 MPH
With 4.77 gears, top speed of an AP1 should be 165.23 MPH

Of course, that doesn't take wind resistance into account at all. These numbers are probably only valid on a dyno where you don't have wind resistance slowing you down.

The gear ratios I'm working with are,

AP1: 1st- 3.133 2nd- 2.045 3rd- 1.481 4th- 1.161 5th- 0.971 6th- 0.811 Diff- 4.1 RPM- 9000

AP2: 1st- 3.133 2nd- 2.045 3rd- 1.481 4th- 1.161 5th- 0.943 6th- 0.765 Diff- 4.1 RPM- 8200


Those numbers look absurdly high to me. Please check my formulae and math.

If there's even half a chance I'm right, then top speeds per gear in an AP1 with a stock diff would be:
1st: 51
2nd: 78
3rd: 108
4th: 139
5th: 166
6th: 199

In an AP2, they'd be:
1st: 46
2nd: 71
3rd: 99
4th: 126
5th: 155
6th: 192

vtec9

I didn't look too far into it, but I think that page and you are wrong in your calculations. perhaps your gear ratios are incorrect. I think the turn zero page is right since it shows the Ap2 being gear limited to ~155mph at 8200rpm which is correct.

Krenath

The ratios are the same ones that TurnZero display when you pick the AP1 or AP2 from the dropdown select

Where I think the problem might lie is in the tire diameter calculations, but if I plug in smaller and smaller tire diameters in order to get the numbers where TurnZero has them, my final tire size is closer to 245/40-*14* than 17.

What I have for my tire diameter is 24.72 inches for 245/40-17 tires. I suppose I should just go measure the tire radius from the ground to the center of the hub and that'll account for tire deflection and give me something fairly accurate, but it still requires that the rest of the math be accurate. As we can see from the numbers so high they're just silly, that's not the case.

OCMusicJunkie

The graph isn't working. I'm not so interested in top speed... I'm interested in where Vtec kicks in for each gear. I don't want to be getting 12mpg in Vtec at cruising speed.

vtec9

just plug in 6000 for the RPMs and you will see the approximate speed in each gear when the vtec switchover occurs. I say approx because it varies based on several factors, but is always 'around' 6k. However, just because youre above ~6k doesn't mean you will be in vtec. At low throttle (less than half?), vtec won't engage.

OCMusicJunkie

Just went ahead and did that. You still need to be close to 100mph in an AP2 before Vtec will kick in, even with 4.77s. I might go ahead with this now.

wazzurp

I just ordered mine through hardtopguy (nice guy) 4.77 for the AP1 I will wait to get the reinforced diff. Do you think I should get an AP2 housing or just go with the Comptech, no plans for boost ever.