PATC 518 O.D. kit
- Thread starter oldirish
- Start date
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If you mean fluctuating between OD off and on, that can be caused by contacts in the pressure switch as the switching pressure is reached. The slower the transition through the psi rating for the switch, the more likely there will be flutter of the contacts. You can just accel a little harder just below OD engagement speed to get above the switching pressure or install an adjustable time delay relay or circuit to control a separate OD relay, set to delay a second or two. Then OD will not engage until you get above the switch psi rating.
Headintheclouds
Well-Known Member
I just installed a pulse damper designed for fuel injection in the line before the pressure switches. It may not be the complete answer but it certainly helps.
Headintheclouds
Well-Known Member
That's it. I used AN4 pipe to extend into the engine compartment so that the switches are easy to adjust. I added an AN4 coupler with 1/4 NPT take off and then a 1/4" x 3/8" NPT reducer to fit the OEM pulse damper.
I am using a micro switch on the throttle linkage to switch out overdrive at half throttle. This has a long enough operating lever to spring a bit and add some hysteresis so I hardly get any pulsing at all now. I'm still using a vacuum switch to switch out lockup but I haven't been able to completely eliminate pulsing on this circuit. My current plan is to change the vacuum switch for another micro switch on the throttle mechanism somewhere. Having just finished installing a Holley Sniper to replace the Edelbrock I am having to start over but I think I have worked out a good location.
I am using a micro switch on the throttle linkage to switch out overdrive at half throttle. This has a long enough operating lever to spring a bit and add some hysteresis so I hardly get any pulsing at all now. I'm still using a vacuum switch to switch out lockup but I haven't been able to completely eliminate pulsing on this circuit. My current plan is to change the vacuum switch for another micro switch on the throttle mechanism somewhere. Having just finished installing a Holley Sniper to replace the Edelbrock I am having to start over but I think I have worked out a good location.
You could also add a toggle switch so when you can disable overdrive until you are able get out of traffic to drive a bit faster or use a lower pressure switch to put the flutter at a slightly lower speed.
Also, for others interested, I've made a diagram using delay timers and adjustable speed window for kickdown. The pressure switches would need to be specific models and best adjusted with a test rig initially. Bike brake switch is about $8 and the delay relays are around $2 each. No vac or microswitches needed. Full throttle without kickdown is adjustable. Gap between OD and TCC adjustable. No flutter. Intermittent connection resets the timers. No overdrive until the switch has a steady connection for the duration of the delay. Duration is adjustable. 5 pin relay is essentially off until the throttle at least 3/4 of WOT.
Also, for others interested, I've made a diagram using delay timers and adjustable speed window for kickdown. The pressure switches would need to be specific models and best adjusted with a test rig initially. Bike brake switch is about $8 and the delay relays are around $2 each. No vac or microswitches needed. Full throttle without kickdown is adjustable. Gap between OD and TCC adjustable. No flutter. Intermittent connection resets the timers. No overdrive until the switch has a steady connection for the duration of the delay. Duration is adjustable. 5 pin relay is essentially off until the throttle at least 3/4 of WOT.
Headintheclouds
Well-Known Member
Good to see different ways of controlling the hydraulic transmissions.
The reason I have two separate circuits is that I want a fairly light throttle to drop out lockup and quite a bit more for overdrive. Going up steady inclines at around 70mph on the freeway I am ok dropping out of lockup but I prefer to keep overdrive engaged below around half throttle. I like having the overdrive come in straight away but not so bothered about lockup so I may experiment with a few seconds of delay for that.
There are several 40mph and 50mph limited roads near me. I can keep up a steady 40 in overdrive and 50 in lockup overdrive. I also have manual cut switches on the shifter console similar to those in the pictures Trailbeast has posted.
Having just changed to a Sniper EFI I now have a 0-5V throttle position output. It is quite tempting to just use a single pressure transducer and the TPS to drive a tiny Arduino. I can then set overdrive and lockup on and off points with as much hysteresis as required. It may come to this in the end but for a 1960s car I would prefer to stick to the period technology of pressure switches and relays. Much easier for subsequent owners to fault find and fix. I know there's a fancy computer in the Sniper but I have to draw the line somewhere.
The reason I have two separate circuits is that I want a fairly light throttle to drop out lockup and quite a bit more for overdrive. Going up steady inclines at around 70mph on the freeway I am ok dropping out of lockup but I prefer to keep overdrive engaged below around half throttle. I like having the overdrive come in straight away but not so bothered about lockup so I may experiment with a few seconds of delay for that.
There are several 40mph and 50mph limited roads near me. I can keep up a steady 40 in overdrive and 50 in lockup overdrive. I also have manual cut switches on the shifter console similar to those in the pictures Trailbeast has posted.
Having just changed to a Sniper EFI I now have a 0-5V throttle position output. It is quite tempting to just use a single pressure transducer and the TPS to drive a tiny Arduino. I can then set overdrive and lockup on and off points with as much hysteresis as required. It may come to this in the end but for a 1960s car I would prefer to stick to the period technology of pressure switches and relays. Much easier for subsequent owners to fault find and fix. I know there's a fancy computer in the Sniper but I have to draw the line somewhere.
I installed a Holley Carb jet in the inlet line before the pressure switches. It really helps with the "hunting" between 3rd and OD. Also though before I did this, I just learned to drive around the problem by accelerating up to speed a bit faster.
Cley
Cley
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