Can You Limit Shift It?

[PenGun]

When I was young, and had things with rev limiters, you could do really lovely shifts, by just putting pressure on the shifter, and just let the limiter make the shift.

[Sapphireho]

limiter make the shift? What?

[HaXx]

hes talking about clutchless shifting i believe. put slight pressure on the shift lever, and when you take your foot off the accelerator it comes out nice and easy then you can slide it easily into the next gear when the trans and engine speed is matched. i dont do it in my personal vehicle, because why the hell would you, but in the heavy duty trucks i drive a work, clutch pedals are only for starting and stopping, their transmissions dont even have syncros, rev matching is the only important thing.

no, i do not clutchless shift the brz after i banged it off the limiter wtf
the posts you guys see come and go on this forum blows my mind

[Spuds]

... No...

[soundman98]

thanks, but i'd rather replace a clutch than the syncro's.

[Ultramaroon]

The limiter would have to have a tremendous amount of hysteresis programmed in.

It would still be way slower than a traditional, relaxed up-shift.

For all but the most skilled operator, the syncros might as well be made of cheese because they'd last about that long.

[soundman98]

yep. the clutch is made to be replaced. the syncro's require full transmission replacement...

[DarkPira7e]

I can't, but I'm sure you can!

[Capt Spaulding]

I suspect you could do it. But, as others have pointed out, it would be 1) slower and 2) unless you are a shifting god, REALLY damaging to the transmission.

It's slower for a couple of reasons. Let's say the rev limiter kicks in at 7500. If it's soft limiter it may cut fuel or spark to a cylinder or two. The engine will not simply fall on its face.

The idea behind what you want to do is to put pressure on the shifting mechanism and when the power cuts, the load on the transmission goes away and the pressure on the mechanism is enough to execute the shift as soon as the load is removed. This works quite well on constant mesh transmissions - think motorcycles. In fact, back when humfrz was a youngster it was the idea behind the first quick shifters on bikes. It does not work as well on synchromesh transmissions.

So, if you're expecting the rev limiter to cut the power so you can gently slip into the next gear it's not going to happen. The rev limiter (if it's a soft one) will usually result in the engine developing a case of the blind staggers which even in the event you are the shifting god we mentioned earlier, won't take enough load off the transmission to get the shift done. So you're sitting there with your face hanging out and synchronizers in the the transmission turning to slurry and the engine banging and popping away. Ell seven - loser.

The other reason it's slow is 7500 is way past the power/torque peak. My experience in my car is that the power begins to drop off as you approach 7000. After 7000 both of the stock engine's curves drop like a flume ride at six flags. You can push it farther, but that will slow you down. You're better off (in my opinion) shifting at about 6800-7000. That drops you down in to the mid 5000 range which is very close to the place where the engine's torque and horsepower curves intersect which is generally (again, in my opinion) where you want to be after an upshift.

[NoHaveMSG]

The window for floating gears on this car is pretty short. There is no practical reason to do it so why bother

Shifting by banging the limiter is just....why?

[EndlessAzure]

Originally Posted by PenGun

When I was young, and had things with rev limiters, you could do really lovely shifts, by just putting pressure on the shifter, and just let the limiter make the shift.

The FRS/86/BRZ transmission is pretty forgiving. It's pretty easy to clutchless-shift on the car.


Can you limit-shift on this car? Never tried it. However, the rev-limiter on the FRS/86/BRZ is a hard fuel cutoff. It doesn't bounce, so with that considered I am doubtful it will limit shift.

[Lantanafrs2]

I've heard of shapeshifters

[ZDan]

Originally Posted by Capt Spaulding

The other reason it's slow is 7500 is way past the power/torque peak. My experience in my car is that the power begins to drop off as you approach 7000. After 7000 both of the stock engine's curves drop like a flume ride at six flags. You can push it farther, but that will slow you down. You're better off (in my opinion) shifting at about 6800-7000. That drops you down in to the mid 5000 range which is very close to the place where the engine's torque and horsepower curves intersect which is generally (again, in my opinion) where you want to be after an upshift.

No, where the curves cross means nothing as far as optimal shift points. Crossover rpm is exactly the same for any engine, and only depends on what units you are using. English units, torque in lb-ft and power in hp are "equal" numerically at 5252 rpm. But this is meaningless as the units are different. In metric (N-m, kW), crossover is at a different fixed rpm (apparently 9543rpm), again for any engine or motor.

Optimal shift point for max acceleration would be to shift far enough *beyond* peak power rpm (which is 7000rpm for stock FT86) that you end up at the same power level at the reduced rpm in the next gear up. For us, we can't rev high enough so optimal shift point is at 7400rpm redline.

[NoHaveMSG]

Originally Posted by Capt Spaulding

The other reason it's slow is 7500 is way past the power/torque peak. My experience in my car is that the power begins to drop off as you approach 7000. After 7000 both of the stock engine's curves drop like a flume ride at six flags. You can push it farther, but that will slow you down. You're better off (in my opinion) shifting at about 6800-7000. That drops you down in to the mid 5000 range which is very close to the place where the engine's torque and horsepower curves intersect which is generally (again, in my opinion) where you want to be after an upshift.

7500 is way past the peak, but HP and torque cross at 5252rpm because of the formula used to calculate HP.

HP = Torque x RPM ÷ 5252