So where do you guys think the optimal shift point is for maximum performance? I reset the shift light to 4800. I think torque is the important thing here. But suggestions welcome. Here is nissan's specs:

Horsepower
287 @ 6,200 RPM

Torque (lbs/ft)
274 @ 4,800 RPM

 

I will probably set it around 6250 - 6450. I think that's the shift point where we will see the fastest times.

 

mine is at 6000 rpm

 

Mine is at 6K

 

For myself, I'd probably tend to set the light at a higher RPM close to the redline. For break in, I think the light is helpful. After that, I'd rather not have it blinking at me all the time. Purely a matter of preference for me.

 

I would set it at 6000-6200, after then the HP and TQ curves tend to drop off quickly. I don't think redline will bring much more than vibration, so HP peak may be the fastest.

Boomer

 

6200. After a while, the light gets annoying. I want to know when I really HAVE to shift.


Hey Matt, where do you live in Queens? I have a few friends near Bayside.

 

I live in this huge mansion in Flushing. jk I live near main st.

 

if the max torque happens at 4800 rpm, isnt anything above this just burning gas and reving the engine to make a louder noise? Above 5500 rpm i am not getting as much explozion as i feel between 4500-5500.

I think for now i will just set it high as someone here suggested. cuz the only light i want to see is "VDC Off" hehe

 

You can't live on torque alone - that's why there's HP. And you gotta get to 6200 if you want to maximize it!

 

Each time your engine makes a revolution it is producing power, if the engine is spinning faster you will get more power even if the torque is less for each revolution (at higher rpm's). This is the reason why we talk about hp.

Therefore for the fastest times you want to shift at or above peak hp, you may want to shift after the peak hp because the next gear will pick up at a higher rpm since you will be traveling faster.

 

Another reason why you want to shift at a higher rpm is so that you'll be at a higher starting rpm when you get into the next gear. Just time yourself doing one method vs. another method and I bet your times will be faster if you shift at 6000 vs. 4800.

 

In any given gear, the more torque the better. However, if you can make it to a lower gear (which will require more RPM to maintain the same speed) the torque generated by the rear wheels to the road will be greater due to the mechanical advantage of the gearing (this is why horsepower is important - it gives you an indication of the engine's capability regardless of gearing). Therefore, it is good to stay in a gear long enough so you can take advantage of the lower gearing, and, as importriders noted, so that you remain in the powerband when you upshift. Since the Z has huge lowend torque, a close ratio transmission, and drops the torque significantly at the high end, you can probably shift below 6000 or so and not miss much power. If you look at racerboy's dyno results (https://my350z.com/forum/showthread....&threadid=6238), you can see that at 5500 there is aproximately the same torque as there is at 3000. If I look at the gear chart in my 2nd edition catalog, it looks like the largest RPM change is 1-2 shift = 2500 RPM. Next is 2-3 at about 2000, and the rest are about 1500. I would therefore never shift over 5500-5700, and most of the time would probably shift closer to 5200. Maybe aftermarket cams and a freer intake and exhaust can open up more of that top end. So far, I've had to shift at 4000 (due to break in period) and I still am impressed by the performance of the engine. Fantastic!

-D'oh!

 

OK, I suck (not that anyone seems to care). After all the talk in my above post about the advantages of gearing, I forgot to take that into account in the shift point calculations. So, here's the real deal:

The goal is to make the torque created by the rear wheels in the gear you are about to exit the same as the torque in the gear you are about to enter (if possible). If that is not possible, the goal would be to make the difference between the two as small as possible.

So using racerboy's dyno chart and the RPM differences from my post above, along with the torque multiplication given by the gearing, the following applies:

Gear 1-2:
1st gear applies 13.42XEngineTorque to the Wheels, so even at 6500 RPM there is 13.42x185=2483 lb-ft at the wheels
Shifting to second would put the engine at 4000 RMP which gives us 8.21x213=1748 lb-ft. In this case if you shift sooner you will have an even greater difference and therefore you would want to shift near redline.

Gear 2-3
In this case we have 8.21x185=1518 lb-ft @ 6500 in second gear, and 5.73x215=1232 lb-ft in third. Again, shifting near redline is good.

Gear 3-4
5.73x185=1105 lb-ft @6250 in 3rd, and 4.50x219=985 in fourth.

Therefore, after all that, it looks like intuition is correct and shifting close to redline is the best way to go.

That makes me feel better about the useful range of the engine. It would still be nice to get a more linear top end though.

-D'oh!

 

I set it at 6100 rpm, i know when the light goes on I will power shift it...so it will take me a bit over that. That's what I tried at the track...and I got a 14.3 at a bad track. just my 2 cent. If there is a better way, please do tell...i want to improve.