I have no experience with this setup. As I understand it to help make the shift without the clutch, the throttle is effectively blipped while the shift takes place to interrupt power output.
What I don't understand, why is this blipped action not instigated by an ignition control, maybe mounted with a simple push button on the gearshift, no foot action required, and high rpm engine air flow never gets disturbed.
Seems simple to interface with an EFI system, and likely not hard to set-up with an aftermarket ignition.
What am I missing?

Thats how they work on a motorcycle, air shifter

That’s how how they work on many boats - to soften the shift to reverse.

I believe Nicholson or some other racer back in the day used a momentary switch and it was banned back then.

Agreed, hat’s how quickshifters work on motorcycles- they interrupt the ignition, not the air path side.

Some of the really quick manual trans racers are also using strain gauges on the shifter that will cut the ignition when pressure is applied during the shift as well. The throttle is always left open in these scenarios.

That seems slick, do they do a full ignition cut or operate like rpm limiters do and alternate cylinders?
Regardless, it seems a much better way rather lifting your foot every time,

Any way you look at it, spark cuts, fuel cuts, and throttle cuts are all power cuts.

Better to keep the engine flat-out thru the shift without any cuts if you can. Even if you have to push the clutch pedal to initiate a full power gear change, the resulting rpm flare is evidence of energy being stored while power flow was interrupted. That stored energy then gets put to work as the engine gets pulled down after the shift is completed.

Grant

You are talking a millisecond of power interruption. No way is using the clutch a better solution.
Clutch operation offers more variation in ET - the interrupter never varies.

Car with typical 7* dogs requires more than a millisecond of cut to unload, and then that cut happens 3 or 4 times as you make your way down the track. Takes longer to make the same amount of power vs no cut at all.

Grant

You are obviously new to all this.

In some instances rev limiter is used, with an rpm setting slightly under the shift RPM to unload the trans for the shift. There is a variety of ways to active the shift rev limiter. A strain gauge is used on some setups so that when you pull the shifter, the strain gauge signals the rev limiter. Or a switch at the very beginning of clutch travel, so you just put pressure on the shifter, then tap the pedal enuff to throw the switch but not the throwout bearing to make the shift. Or a switch on the shifter. Some EFI systems also have the capability of interrupting the power for the shift. Some guys apply pressure to the shifter, then just let the engine hit the overall rev limiter to complete the shift.
So what you envision is being done in various ways.

Seems so, learn something every day. Seems to me I would favor a stick mounted momentary push button that would temporally activate a rpm limit switch a few thousand below my shift points.
My interest here is more road race, but everything I'm reading here seems/sounds workable.
This allows left foot braking, and that is a big advantage left over from my go kart days,
Maybe why it's not shared/talked about much?

Glad you stated this is for a road race deal because to do this modification for RPM blip in a drag transmission with "dog" ring sliders would be pointless in a drag race application.

Gus

I have a Qaife dogbox in my vintage road race car. I just let off the throttle a bit to shift. I never thought to interrupt the ignition
since there are so many variables in lap times. I know some dog box tranny's require accurate rev match when down shifting.

My apologies, I assumed the op had a drag race application in mind.

Grant

The problem though as I see it, blipping the throttle has little? effect on rpm matching with upshifts, only effects the torque that keeps the dogs locked, on downshift the only rev matching it seems to me would be if transmission went effectively to neutral while rev matching took place by letting the engine rev before reengaging. Seems risky, uncertain and problematic at face value, pun intended. It would be IMO interesting to see the results of instantaneous rpms of the engine transmission that is happening during these types of shifting events overlayed with throttle position.

I had an HKS H pattern dog box in my RX7 and now have sequential Quaife. You can teach yourself to either do a light clutch stab that actuates a rev limiter or ignition cut with a switch , or a light lift on the throttle to clutchless upshift under acceleration, you need an RPM blip to downshift the transmission. I was doing throttle lift by foot because of the ecu my car had, but it takes mental training. I now have an ECU that can basically run the transmissions rpm needs from the clutch switch, strain gauge, wheel speed and the TPS, which will make it much easier to drive when focusing on cornering lines.
Close ratio dog box is king for a turbo car, quick shift, transmission efficiency, and you don't drop out of boost between shifts. You can run a much larger turbo and not worry about lag or response between shifts and keep the motor at its boost point around and out of corners, works just as good on the drag strip too for the same reason.
Here is video of the old Attain RX7 from 2001, HKS H shift dogbox RX7, 700 rwhp, 9 second car, the drivers technique makes it sound seamless but watch it at .25 speed and it sounds like it's a normal synchro transmission being shifted, and you can see his left leg just tap the clutch for the ignition cut.

Yea, thanks, this is something I neeeed to look into.