1971 TCS system general questions.

[Mike H.]

Re: 1971 TCS system general questions.

Joe,
I don't believe the CEC carb mounted solenoid activates with the A/C compressor, at least it doesn't on mine! That is why the additional relays engage the A/C compressor on engine shut down to help prevent run on, due to the greater throttle blade opening required for A/C on idle.

[Dave S.]

Re: 1971 TCS system general questions.

Joe,

Another function of this "off the wall" system is the elimination of vacuun while in 3rd and 4th gear. There is a switch on the side cover that activated the solonoid (and extends the plunger) when the car is in either 3rd or 4th. Now we can see why it thankfully was a one year only design.

[Joe L.]

Re: 1971 TCS system general questions.

Dave-----

I believe that the vacuum interupt in high gears is a function of the TCS system as used for all of the years that it was used. In fact, with the apparent exception of 1971, that is the only basic "function" of the TCS system.

[Jack H.]

BINGO, Mike--that's correct! *NM*

[Jack H.]

Yes, again...

the high gear activation of the CEC solenoid was an extention of the '70 TCS system but integrated into the single part (CEC solenoid). Some are quick to 'blame' the CEC system for 'poor' performance, but that's generally because they don't full understand. Here's more:

In high gears (3rd/4th manual trans or 3rd/rev automatic), the CEC solenoid is engaged and you get full vac advance to the distributor + a slightly higher curb idle. The vac advance is there to generate fuel economy while crusing for long periods of time at highway speed. It's NOT there in low gear based on the assumption, FEW spend long periods of dwell in low gear (parade cruising) and they're in low gear(s) only briefly during accel/decel. If that's true, then the benefits of vac advance to the dist are slim/none since the distributor's advance is DOMINATED by centrifical considerations. So, if we're sitting at a stop light, let the engine idle without vac advance to retard timing and generate more complete combustion.

When we decel from high gear (exit the freeway, Etc.), it's the absolute instantaneous engine RPM differential that dictates how rich exhaust gas is going to be in unburned hydrocarbon content. If we 'scootch' curb idle up a 'tad' with the CEC solenoid we achieve a cleaner exhaust content....

So, the one-year only CEC system combined the prior TCS technology with the benefit(s) of having two curb idle settings for the carb. The 'smart' relays and multiple inputs allowed the used of a very primitive on-board computer to do the 'intelligent' thing at the proper time.

But, because engine compression fell a BUNCH at the same time, the CEC system was viewed/blamed for loss of performance and folks found myriad ways to 'castrate' it. Bottom line, getting rid of the CEC didn't buy them 'squat' but they felt better about the car!

[Patrick H.]

Re: 1971 TCS system general questions.

Dave,

See Jack's note below. Vacuum is blocked in 1 and 2, not 3 and 4.

Patrick

[Dave S.]

Re: 1971 TCS system general questions.

Patrick,

You are absolutely correct. Thanks for pointing out my error.

[Tom R.]

Re: 1971 TCS system general questions.

The 71 Chassis Service Manual has a nice diagram of the TCS system including the two relays and depicts the various relationships. I could scan and email for anyone interested...but it will probably be a big file.

[Roberto L.]

Re: 1971 TCS system general questions.

Very interesting subject, even if the device seems unimportant. I would like to know a safe way to test the 70 TCS solenoid. Remember that I have a Super T10, not a Muncie , so my TCS trans connection is open. Is it safe to ground the trans TCS wire to test, as in 3th and 4th? I guess there is no problem but my moto is "ask before verify"

The rest of the system is connected. Thanks!

Roberto, NCRS #30019, RMC

[Jack H.]

Re: 1971 TCS system general questions.

Check your wiring diagram and you'll see the tranny TCS switch is a simple contact closure to ground mechanism (one wire only to the TCS switch). But, it NEVER hurts to ask/check first!

Abrasos, amigo!

[Jim T.]

Re: 1971 TCS system general questions.

Jack I was reading all the posts and saw that you mentioned what will happen when the temp sender detects to high of engine heat and allows full vacuum. Back in 1970 my car did reach the high temp at idle one day. The car was new and I became interested why the idle would speed up in park with the air on during a hot summer day. Finding the reason I disconnected the TCS and ran full vacuum, still have it that way. Car never got hot at idle again and picked up a couple miles per gallon in city driving.