Shifting

[Towlie]

Just wondering

What do u guys shift at in ur 240's and why?

i know a lot of ppl who dont redline, and i was wandering y?

[J SPEC SilEighty]

here's something I wrote for a guy on 240sxforums.com a couple months ago...


Ok, a common mistake of new drivers is that they think it is best to always shift at redline. I think this would mostly be due to the ever so popular "the fast and the furious." So here is a way that you can find out the best shift point for the fastest acceleration.

First, you are going to need a dyno chart of your current setup. If you are stock, then I used that as an example below... With the dyno chart, you will need to check the amount of torque that you have at close RPM incrimants (every 200 RPM or so). After you have the torque number for each RPM, you will want to write this down somewhere.. I setup a spreadsheet to enter the info into and it automaticly calculated it for each gear. This next part is what takes the longest. You will need to multiply the torque number that you have for a specific RPM by the gear ratio for the gear you are in to get the actual amount of torque being sent to the differential before it goes to the wheels. After you have all of the numbers you need (see chart below) then you are going to need to look at it and find out where the most power is. In my example, the most power is at approximately 4000 RPM. When you shift gears, you want the engine speed to drop as close to 4000 RPM as you can get it because that is where the power is. If you are in 1st gear, even though the power is dropping off in 1st after 4000 RPM, you want to keep going until you are at the point where it will take you back to 4000 RPM when you shift to second so you will have the fastest acceleration for the new gear. To find what your new engine speed will be after the shift, use this formula:

NEW RPM = CURRENT RPM X (NEW RATIO / CURRENT RATIO)

So if I was to use that formula and the numbers that I had in my chart, these are the shift points that I came up with.

- 1st gear to 2nd gear: you will want to shift at redline, 6500 RPM, because that will put you at 3722 RPM in 2nd gear. NOTE: you really want to be closer to 4000 RPM then that, but since 6500 RPM is the redline, there isn't much you can do about it.

- 2nd gear to 3rd gear: If you shift at 5800 RPM, that will put you at 3988 RPM, right where you want to be.

- 3rd gear to 4th gear: If you shift at 5150 RPM, then it will put you at 3937 RPM, which is close to your 4000 RPM mark.

- 4th gear to 5th gear: Shift at 4750 RPM, and that will put you at 3980 RPM.

NOTE: Once again, this is just for a stock 240sx. If you have modified your car or it is in poor/great condition, the shift points will vary because the dyno chart will be different.

Here is the spreadsheet that I set up with all the the torque numbers and I also put up the stock 240SX KA24DE dyno chart that I used for this.

[Towlie]

thx, that helps a lot

[GT-R4life]

Very helpful explanation. Would this also hold true for cars with VTEC or other variable valve timing systems?

[SiRI]

Hmm very logical.. might have to try all taht out in a car and see if it helps a noticable amount

[Fliquer]

Simply put, you shift right about the time your power curve drops off. In a KA 240sx thats around 5500rpm. You should be able to feel where the power drops off through your butt dyno.

Nice chart tho

[Jaegermeister2k]

Hey what about the g-tech performance meter competition.It's supposed to have an inteligent shift light as opposed to those huge ass rpm meters with that light that lights up only at redline.The inteligent shift light is supposed to calculate the shift point gor you,i was gonna buy it because it also tells the hp,and 1/4 mile,and all kinds of stuff,buyt i heard a rear spoiler affect the hp number.Is that true?And how much does it affect it?

[Towlie]

Ummm, in vtech its best to redline i would think because vtech kicks in at like 5 grand right? and u want vtech on the whole time

[J SPEC SilEighty]

Originally posted by Towlie
Ummm, in vtech its best to redline i would think because vtech kicks in at like 5 grand right? and u want vtech on the whole time

yeah most of hondas engines work best when shifted at redline

[ghostchild316]

uhh, VTEC?I must be in the wrong forum then damnit!!I thought this was the nissan 240sx forum

[GT-R4life]

My bad about bringing the VTEC up, but now I have been enlightened so I'll discuss it no more.

[J SPEC SilEighty]

Originally posted by GT-R4life
My bad about bringing the VTEC up, but now I have been enlightened so I'll discuss it no more.

I still like Honda's :coolguy:

[ghostchild316]

I gots no problem with hondas either (except the riced out ones...)

[Sanchi]

i think ill stick with my nissan thank you mame'

[littl3_r4v3r]

man i can't wait to test this on my 240sx. when i get it!