[Diy_efi] Using GM '747 to control TCC lockup only -- THANKS!

Wed Sep 13 02:59:03 UTC 2006

You could talk to a parts guy (an older one) and have him find an "EGR 
delay valve" or "distributor advance check valve."  It works like a 
straight-through tube in one direction, and an orifice in the other.  
Used in the late 70s-early 80s on many American cars and trucks as well 
as Toyotas.  If you install it in your lockup vacuum switch (or 
distributor, or EGR valve) it only passes vacuum through slowly - so the 
thing receiving the vacuum receives it slowly.  Then, if you romp on the 
gas (or roll onto it too fast,) the trick valve releases the vacuum 
quickly, so your [tranny doesn't stay locked up, dizzy doesn't stay 
advanced, EGR doesn't stay open] when getting on the gas. 
HTH,
TomV

Leo Schneggenburger wrote:

> Hi David,
> I just happen to be a transmission specialist and yes, you need lock 
> up unless you have really low (high numerically) rear gearing. I would 
> recommend the vacuum setup as with proper adjustment it will 
> automatically unlock under higher load conditions as it should. Hope 
> this helps.
> Leo
>
> David M. Ingebretsen wrote:
>
>> Many, Many, thanks to all who helped.
>> When I had the transmission built, I had the guy put in a "kit" so 
>> that I
>> have a self grounding solenoid in it already. It is also wired so I 
>> can have
>> it engage in 2nd through overdrive or only in overdrive. I had to do 
>> some
>> fancy wiring to get it to work with the 747 ECU.
>> I think the ideas that use a vacuum switch get me most of the way 
>> there. I
>> found that B&M makes a speed dependent lockup, and I think a 
>> combination of
>> that with a vacuum switch might be close enough to the ECU logic to 
>> work.
>> Maybe just the vacuum switch. I'll think on it.
>>
>> It is important to have the transmission locked more often that 
>> because it
>> builds heat way fast when the torque converter is slipping. The 700R4 
>> design
>> and cooling depends on that torque converter being locked.
>> I think the basic ECU logic is to engage when possible and disengage 
>> at a
>> high rate of change of throttle position, at closed throttle, and at 
>> WOT.
>> There is also some speed dependency I haven't looked at closely. I 
>> think the
>> idea to disengage at WOT and high rate of change of throttle position 
>> is to
>> make use of the torque multiplication you get with the torque converter
>> slipping under load and also to disengage when you are coming to a stop
>> (although, the circuit always disengages when the brake is applied).
>>
>> Anyway, thanks for the ideas everyone.
>>
>> _______________________________________
>>
>> David M. Ingebretsen, M.S., M.E.
>> Collision Forensics & Engineering, Inc.
>> 2469 East Fort Union Boulevard, Ste 114
>> Salt Lake City, UT 84121
>>
>> 801 733-5458
>> dingebre at 3dphysics.net
>>
>> __
>>
>> -----Original Message-----
>> From: diy_efi-bounces at diy-efi.org 
>> [mailto:diy_efi-bounces at diy-efi.org] On
>> Behalf Of Eugene Pilipanko
>> Sent: Monday, September 11, 2006 6:20 PM
>> To: diy_efi at diy-efi.org
>> Subject: Re: [Diy_efi] Using GM '747 to control TCC lockup only
>>
>> www.bulkpart.com    part # 74416ak.   Summit racing part # TCI 376600 
>> or Jegs part 3 890-37660 should help you out.
>>
>> ---- Original Message ----- From: "Milosz Kardasinski" 
>> <miloszk at gmail.com>
>> To: <diy_efi at diy-efi.org>
>> Sent: Monday, September 11, 2006 5:16 PM
>> Subject: Re: [Diy_efi] Using GM '747 to control TCC lockup only
>>
>>
>>  
>>
>>> What I have seen in some applications is the use of a vacuum sensor
>>> connected to ported vacuum. You'd have
>>> to set the switch point to whatever you feel is the appropriate vacuum
>>> threshold...but all the sensor does is ground
>>> out, which engages the TCC below a certain vacuum setting. Some also 
>>> connect
>>> a switch in series to turn off TCC
>>> whenever the brake pedal is depressed.
>>>
>>> ----- Original Message -----
>>>
>>>    
>>>
>>>> I converted a Jeep 4.2 liter to a GM throttle body, works well. 
>>>> But, I'm
>>>> thinking of purchasing a MOPAR MPI conversion which was designed 
>>>> for that
>>>> engine.
>>>>
>>>> My dilemma is that I have a 700R4 automatic in the thing and like 
>>>> that the
>>>> GM ECU ('747) controls the TCC lockup. I will lose that feature in the
>>>>       
>>>
>>> Mopar
>>>    
>>>
>>>> unit.
>>>>
>>>> Any ideas about the feasibility of using the '747 to just control 
>>>> the TCC
>>>> lockup?
>>>>
>>>> I think I can piggy back off most of the sensors the TCC logic 
>>>> uses; temp,
>>>> speed, MAP, but I'm not sure about the throttle position. I saw a 
>>>> cable
>>>> throttle position sensor which might work.
>>>>
>>>> What happens when the ECU isn't actually controlling the fuel 
>>>> anymore and
>>>> the closed loop logic gets feedback, but isn't controlling the system?
>>>>
>>>> Is there a better way to automatically control the TCC and disable the
>>>>       
>>>
>>> other
>>>    
>>>
>>>> processing in the GM ECU?
>>>>
>>>> I just hate going to a switch on the dash. It's so "unelegant".
>>>>       
>>>
>>> _______________________________________________
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>>>
>>>     
>>
>>
>>
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>>   
>
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