BEGI turbo ...3500 rpm shiftpoint???

[DBR]

i've heard that to get the quickest acceleration times from a dead stop, you shift at max torque, which is only 3500 rpm on the flyin miata/BEGI turbo. see here:

http://www.flyinmiata.com/protege/tech/dyno_runs/FM_P5_6psi.pdf


seems kinda low. any comments? things must get kinda frantic at full throttle.

 

[spoolinmp3]

To get the most out of your motor you need to wind it out. Yes you get maximum torque at that range but you need to sift at 6500 to 7000 rpm to get maximum acceleration

 

[Gyre]

I think what they mean is that you want to shift so that the range you're running maximizes torque, not at max torque. I'm not sure that's quite true because the lower gear could give you more acceleration for a little past max torque because of the mechanical advantage.

When you shift you go from a higher RPM to a lower RPM (I'm not about to calculate it right now). If you shifted at 3500 rpm, you'd drop too low. By shifting some amount above 3500 rpm, you'll drop down to something near 3500 rpm, maximizing torque through the whole range.

It looks like the torque curve is steeper before 3500 and shallower after 3500 so it's better to shift later than earlier.

 

[70]

You get the most acceleration in any gear at max torque. You get the most acceleration at any speed at max power.

You want to shift close to redline (about 6200 rpm in the Protege) to get the max acceleration overall, and so that in the next gear up you land right in front of the max torque.

 

[igdrasil]

yeah...I found that shifting @6000rpm will make the next gear pull stronger...

I have not tested this a lot on track, but I know that it will def. pull strong.

 

[DBR]

thanks for the answers. a lot clearer now.

You get the most acceleration in any gear at max torque. You get the most acceleration at any speed at max power.

StuttersC...if possibe, can you expand on this distiction, or give some examples of each. it seems to be saying a lot, but i'm not sure i understand. thanks.

 

[70]

thanks for the answers. a lot clearer now.

StuttersC...if possibe, can you expand on this distiction, or give some examples of each. it seems to be saying a lot, but i'm not sure i understand. thanks.

How do I clarify that more? Um, well, leave us say you are in third gear. For third gear you will get the most acceleration at the max torque. So around 3500 rpm you will be getting the most acceleration out of that gear. The same would hold true for any other gear. Around max torque you will be getting the most acceleration you will ever be able to get out of that gear.

Now let's say you are in second gear hitting the top end, which is going to be around 58 mph. Obviuosly you will be at or close to the peak horsepower at the top of the gear and you will be getting the most acceleration at that speed.

Does this help? Understanding the relationship between horsepower and torque really helps with this.

 

[turbo740]

It's been said in other ways but you want to shift at a point that will drop your next gear right into that 3500rpm sweet spot. Check what speed you are at when in 2nd at 3500 rpm. Suppose it's 35, just for the heck of it. Then, when you are at 35mph in first, shifting to second will put you in that sweet spot. Now, what RPM were you at in 1st when you shifted to 2nd at 35mph? If the gearing were linear, you would shift at that RPM every shift and it would, theoretically, drop you into the 3500 rpm sweet spot again. Not sure if this makes any more sense than how it was already presented, but it's another view.

Have fun.