Warm up what?

audiofilius · 10-17-2004, 07:58 PM

Hey guys...what do u think of this..a manually controlled cold start valve...

Paulporsche · 10-17-2004, 08:43 PM

We already have one because the CSV does its thing only as long as you are turning the key to start the car. When you let the key turn back, the CSV stops firing because the car has started. You don't need or want the CSV to continue to run.

What some have suggested is a return to the equivalent of a manually operated WUR, which was the old hand throttle system. This would allow manual control of the warmup phase. I am guessing but I imagine the hand throttle was discontinued in favor of the automatic system which would seem more in keeping w/ a car of Porsche's stature and to meet increasingly strict emission requirements.

For people in tune w/ their cars the manual system seems like a good idea. For those not so inclined a system that automatically adjusts richness depending on engine requirements is better, and if set correctly, more accurate.

A lot of space on this BB has been devoted to getting that old WUR adjusted correctly to do just that and these techniques certainly do seem to produce the desired results.

BTW all this opinion I have been spouting is for CIS cars.

audiofilius · 10-17-2004, 10:02 PM

"a system that automatically adjusts richness depending on engine requirements is better, and if set correctly, more accurate"

true but...too many valves, too many switches..too many things to go wrong...
what I was thinking is activating the CSV as needed for the warming up process.

john walker's workshop · 10-17-2004, 10:19 PM

the CSV only sprays some fuel into the intake to start the engine only. after that, the WUR keeps it running richer for a short while, like a choke on a carb, and the air regulator kicks the idle up. the CSV is totally out of the system after you let go of the key, or after about 8 seconds when the thermo-time switch breaks the circuit so the engine doesn't flood out because of it. a hand throttle only raises the idle, it doesn't richen anything.

Paulporsche · 10-18-2004, 06:53 AM

Got it. So the hand throttle actually performs the same function as the AAR.

audiofilius · 10-18-2004, 07:07 AM

"the CSV is totally out of the system after you let go of the key"

True...unless u put it back in the system..ie; bypassing the thermo time switch and activating the CVC manually with an on/off push button switch.

Paulporsche · 10-18-2004, 07:26 AM

I have read about trying to use the CSV as a 7th injector for competition or performance running in some of the various CIS books. This was rejected , I think, because of its location within the fuel system. Whether this would work for short durations during warmup I don't know. Maybe you could try it as you say by bypassing the thermotime switch so the valve continues to operate until you tell it to stop. What the ramifications of this are I can't tell you. Maybe someone w/ a lot of experience w/ these cars, like Mr Sims or Mr Walker...

john walker's workshop · 10-18-2004, 08:10 AM

i've seen the CSV hooked to a switch to help start CIS and MFI engines that were "cranky", and it does work, as long as you don't overdo it, and flood the engine (fuel foul the plugs). kind of like keeping the manual choke on too long on a carbed engine. if the real problem was addressed, you wouldn't need the bypass.

audiofilius · 10-18-2004, 08:20 AM

the real culprit is the WUR. I have tried three and they're all unreliable.

Tim Hancock · 10-18-2004, 10:45 AM

I temporarily wired a CSV to a switch inside my daughters 924 to alleviate a hot start issue I was dealing with. It was kind of neat to energize this during acceleration you could feel it pulling harder with the switch engaged. After fixing the real problem I rewired back stock.

It was interesting to play with though.

audiofilius · 10-18-2004, 11:21 AM

what does the CSV have to do with hot start issues??

Tim Hancock · 10-18-2004, 11:39 AM

I was losing pressure in the system when shutoff. When the residual pressure drops quickly when the engine is hot it allows the fuel the system to vapor lock. When you try to restart a short time later, you now have vapor in the lines. It takes quite a bit of cranking time to clear the system of vapor.

So if one can inject enough fuel into the intake to allow the car to run for a short time the vapor lock clears and the engine now is running on its own. The cold start valve is generally not subject to this vapor lock because it gets it's supply of fuel before the fuel distributor. So when I "hotwired" the CSV I could provide enough fuel for the car to start.
If left on at idle or low rpm the mixture is way too rich but on acceleration it really helped.

Keep in mind this was on my old anemic 924 and was just a stop gap experiment till I got my new fuel pump/check valve and accumulators.

I kinda felt like a ricer pilot nailing the button on acceleration ha ha.

Kemo · 10-18-2004, 11:43 AM

im not sure what was up with mine...maybe the thermotimeswitch was hosed or something...but on occasion, after about 2hrs of sitting after running the car...it wouldnt start...and would flood. After reading a bunch here and getting the bosch fuel injection book, i kinda fixed it by removing the wire to the thermotimeswitch. To me, that was a hot start issue possibly similar to above. since then, i have replaced the WUR but i left the thermotimeswitch disconnected...im in texas so the whole cold start thing isnt much of an issue...however, I do wonder how much harder this is on the starter motor. I have actually thought about running a connect-the-ground kinda switch under the dash for the CSV just to ease my mind, so to speak