Hand throttle question

[Pazuzu]

For those who use them, especially those who have added them to later cars...

How long do you use it? 2 blocks? 15 minutes? On a well maintained car, is is really even needed instead of just using the pedal for 30 seconds?
How often do you use it? Only after the car has sat overnight, or do you need to use it after an hour?

Trying to gauge the pros/cons to ripping all of the CIS emissions stuff off. People talk about converting, but they never really talk about the details of how it changes your driving.

[Trog]

Depends on how cold it is outside. I disable it when the engine will idle without any hand-throttle assist. On the coldest of days up here, it has taken up to 5-minutes.

[Tidybuoy]

Here in Fresno (which is cold in winter (30's) and very hot in the summer (100's)), I barely need it in the summer but this winter I have the lever all the way up for about a minute and then I slowly lower it during warmup to keep the rpms around 1800. I almost never drive with it up as it keeps the rpms too high.

My car is not in perfect tune but it will be in about a month.

[ossiblue]

The two responses, so far, are really typical of hand throttle use and I think others will further establish the pattern--a lot depends on the outside temperature, and using the throttle is a short-term activity.

Be aware, if you are retro-fitting a hand throttle to a later system, that you will need the micro-switch set up as well. When you pull up on the hand throttle, it not only pulls on the throttle cable but opens the micro-switch on the throttle body which permits the cold start valve to operate. On cold starts, you will need to pull up the lever (or hold your foot on the gas pedal) to operate the cold start circuit. You will already have a thermo time switch which overrides the cold start circuit when the engine is warm.

[Pazuzu]

Primarily I wanted to get a sense of whether the hand throttle was required vs feathering the foot throttle for 30 seconds. I don't mind that, but if it requires constant attention for 4 or 5 minutes at 45 degrees ambient, then it's an issue. My "cold weather" starts are on average warmer than summer starts for some of you guys

Sounds like it's not gonna be an issue for me. Hell, I'm putting an aluminum PP and flywheel on, I have to relearn how to drive the car anyways!

Edit: What triggers my cold start valve now? I do have a thermo switch to turn it off, and it works.

[Pazuzu]

Quicky research says that the CSV is fed power through a combination of the starter solenoid and the thermotime switch. So, it only sprays if both the starter is cranking and the engine is below temp.

Why would I need the microswitch then? Unless the hand throttle era cars required that the CSV ran longer than the later cars. If I simply disable the AAV/AAR/Decel setup and plan to feather the gas with my foot for 30 seconds on cold starts, will I need the microswitch?

[Jerome74911S]

Originally Posted by Pazuzu

feather the gas with my foot for 30 seconds on cold starts. . .

Wow. Up here in Quebec where things can be cool, my car simply won't idle until the oil temp begins to come up. That can take more than five minutes of driving, so adjustment of the throttle lever is always an issue.

You might get away with the mods you suggest, but it sure is alien to me.

[Pazuzu]

I turn the heater on sometimes. Just crack the flappers a bit.

I usually open both windows too, since it gets WAYYYY too hot in the car then.

[dfhtrhjn]

I've got pretty well adjusted carbs and have never needed to use it, but I have had cars where it was very handy to have for the first 5 min or so.

[ossiblue]

Originally Posted by Pazuzu

Quicky research says that the CSV is fed power through a combination of the starter solenoid and the thermotime switch. So, it only sprays if both the starter is cranking and the engine is below temp.

Why would I need the microswitch then? Unless the hand throttle era cars required that the CSV ran longer than the later cars. If I simply disable the AAV/AAR/Decel setup and plan to feather the gas with my foot for 30 seconds on cold starts, will I need the microswitch?

On hand throttle cars, the micro switch served a similar purpose as the thermo switch. The cold start valve (actually a solenoid) receives power via the start circuit but in hand throttle cars, the ground connection to the solenoid is via the micro-switch--pulling up on the lever grounds the circuit to the solenoid allowing it to spray. When the lever is down, the ground connection is open and the solenoid will not spray even when the starting circuit is energized, unless you push down on the gas pedal to (again) operate the micro-switch and ground the solenoid. That same function is performed by the thermo-time switch on your current set up, and if you keep it, you will not need the micro-switch on the throttle body. However, to allow more incoming air for cold starts that is currently done through the AAR, you will need to still pull up the lever or feather the pedal, as you currently do.

[adamr]

Please forgive my ignorance, but where is the hand throttle, is it the white lever next to hand brake on the 80 911 sc?

Many thanks

Adam

[ossiblue]

Originally Posted by adamr

Please forgive my ignorance, but where is the hand throttle, is it the white lever next to hand brake on the 80 911 sc?

Many thanks

Adam

No hand throttle on cars after 75. BTW, asking such a question is nothing to apologize for--you're just the one with the guts to ask it!

[adamr]

So here is question # 2. what is the white lever to the right of the hand brake?

thanks
Adam

[winders]

Originally Posted by adamr

So here is question # 2. what is the white lever to the right of the hand brake?

Do you mean the heater control lever that is supposed to be red?

Scott

[Jim Sims]

The owners manual for a 1973.5 CIS states that the hand lever should be pulled fully up (so the micro-switch on the throttle body closes and sends power to the cold start valve) for all starts when the engine temperature is less than "very high". Very high is defined as an engine temperature of 212 to 250 F. Unless the engine is running hot and the stop is very brief (so the engine doesn't cool off) this in a practical sense means the lever is pulled up for every start. The manual further states that when the ambient air temperature is below -5F the lever should be fully pulled up and the gas pedal partially depressed; then when the engine starts, the lever is positioned for a 1200 RPM warm up speed. For "nominal cold starts" (air temp above -5F and engine oil temperature below 155F) the lever should be pulled fully up without gas pedal application and then once the engine starts the lever is lowered to set the engine RPM at 1200 for warm up. When the engine is warmed up (~155-160F oil temp) the lever is fully lowered. When starting a warm (as opposed to a "very high" temperature) engine the lever is pulled up for starting and immediately pushed back down after the engine starts. For the very high temperature case (212 to 250 F oil temperature) the hand lever is left down and the gas pedal is fully depressed during starting. It is important to note that the '73.5 and (also the 1974?) CIS cold start valve (CSV) circuits do not incorporate a thermal time switch so the driver has to control this function. Note though that as usual the CSV only operates while the starter is turning, it does nothing for cold running after that time.

[javadog]

Couple things...

They used the hand throttles up through 1977. The Carrera 3.0 cars had them.

And, I don't think all of the cars fitted with both CIS and a hand throttle used that microswitch. The early cars did but I don't think that all of the later ones did. At least that's what I think I remember...

JR

[Pazuzu]

Originally Posted by ossiblue

That same function is performed by the thermo-time switch on your current set up, and if you keep it, you will not need the micro-switch on the throttle body. However, to allow more incoming air for cold starts that is currently done through the AAR, you will need to still pull up the lever or feather the pedal, as you currently do.

That's what i thought, the confusion came from you mentioning that I would need the switch. Thank you for your help!

[Swordfish II]

I have an issue maybe you guys could help me on.

My hand throttle (76 Euro car) when pulled up fully on a cold start results in a very high idle (3,000 or higher) so I bump it down slightly as recommended to get the 1000-1200 rpm idle. I keep lowering it as it warms up to maintain this rpm, however once fully warm my car still needs the hand throttle partially up to maintain the 950rpm idle. If I push it all the way down, idle is too low and when pushing the clutch in after being in gear the car will stall (if it isn't partially up).

Does this sound like a WUR or CSV issue or simply an idle screw adjustment issue? I have been tempted to warm it up fully then adjust the idle screw so it idles at 950 with the hand throttle fully down, but wanted to get opinions first.

[javadog]

Adjust the idle screw. Make sure the CO and ignition timing are set correctly, too.

JR

[Swordfish II]

Thank you.

Ignition timing and CO should already be ok already as the hand throttle operates the throttle cable, so it would be the same as leaving the hand throttle down and simply leaving my foot on the gas. Or am I missing something?

The engine recently (about a year ago) had a full rebuild. I suspect they simply set the cold idle before the car was fully warm