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?
" All sorts of things can happen when you are open to new Ideas" Inventor of Kevlar
Re: Dog Shift race Trans Question
[Re: jcc]
#3212090 02/08/2409:32 PM02/08/2409:32 PM
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.
'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
Re: Dog Shift race Trans Question
[Re: Blusmbl]
#3212149 02/09/2407:51 AM02/09/2407:51 AM
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,
" All sorts of things can happen when you are open to new Ideas" Inventor of Kevlar
Re: Dog Shift race Trans Question
[Re: jcc]
#3212175 02/09/2411:56 AM02/09/2411:56 AM
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
Re: Dog Shift race Trans Question
[Re: weedburner]
#3212206 02/09/2402:02 PM02/09/2402:02 PM
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.
Re: Dog Shift race Trans Question
[Re: A727Tflite]
#3212367 02/10/2401:01 AM02/10/2401:01 AM
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
Re: Dog Shift race Trans Question
[Re: weedburner]
#3212484 02/10/2401:57 PM02/10/2401:57 PM
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.
Re: Dog Shift race Trans Question
[Re: jcc]
#3212532 02/10/2405:13 PM02/10/2405:13 PM
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.
[img]http://i.imgur.com/boeexFms.jpg[/img] 31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
Re: Dog Shift race Trans Question
[Re: Hemi_Joel]
#3212573 02/10/2407:19 PM02/10/2407:19 PM
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?
" All sorts of things can happen when you are open to new Ideas" Inventor of Kevlar
Re: Dog Shift race Trans Question
[Re: jcc]
#3212639 02/10/2410:11 PM02/10/2410:11 PM
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
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60
Re: Dog Shift race Trans Question
[Re: jcc]
#3212716 02/11/2410:54 AM02/11/2410:54 AM
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.
Re: Dog Shift race Trans Question
[Re: A727Tflite]
#3212727 02/11/2411:25 AM02/11/2411:25 AM
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.
My apologies, I assumed the op had a drag race application in mind.
Grant
Re: Dog Shift race Trans Question
[Re: RTSE4ME]
#3212728 02/11/2411:26 AM02/11/2411:26 AM
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.
" All sorts of things can happen when you are open to new Ideas" Inventor of Kevlar
Re: Dog Shift race Trans Question
[Re: jcc]
#3212794 02/11/2403:43 PM02/11/2403:43 PM
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.
Re: Dog Shift race Trans Question
[Re: Uberpube]
#3212867 02/11/2408:22 PM02/11/2408:22 PM