cis injection

[scott.k]

just a question out of curiousity, with the cis system work without the valces and hoses in the bottom right side of the system? To be more specific, will it work if you were to remove the decel valve, the auxiliary air valve, and those rubber and metal hoses linking them together down there? And then just capp where the hoses connected off?

Also, venting the pcv/oil spillover into a catch can with a filter/vent on top?

If not, what can be removed from the injection system and still have it working?

Thanks
Scott

CIS Primer for the Porsche 911

[scott.k]

in these pictures, im wondering if I can remove the pieces with the white tape. this basically includes the aux air valve, aux air regulator, decel valve, (and all of the metal and rubber hoses connecting these. Also, the small vacuum hose that comes out of the deceleration valve and enters the back of the throttle housing metal block type thing.

thanks for the help
Scott

[scott.k]

[Bob Kontak]

Here is a link to the CIS primer. Read about what the components do. I think you could delete the decel valve but the other two would cause hard starting unless you rig up some sort of manual air bypass.

CIS Primer for the Porsche 911

[Scott R]

You can delete them, starting will be hard as mentioned above, and decel will be a bit off. It could die on occasion as you let off the gas coming to a stop. But why would you want to do this? Everything in your picture works in harmony when the system is running correctly.

[Dr J]

I did it. Removed all of it. I don't have the component in your last picture though. I live in a warm climate year round, so cold start is not that big a deal. When you remove the decel valve, you may have some burbling/popping. Some like it, some don't. Depends on how rich or lean your engine runs. After cold starting, I have to keep the accelerator somewhat depressed for about 30 seconds or so, until the mixture leans out a bit. Otherwise, I get the oscillation associated with rich mixture. This is enough to stall the engine. The other thing I notice is that my rpms start low (800-900) when cold, and as the engine warms, they go up to about 1100 rpm.

I have considered reinstalling the auxiliary air regulator so that I don't have to hold the accelerator when the engine is cold, and so that I can lower the rpms at warm idle to below 1000.

[crustychief]

I don't think it will pass smog like that.

[Mia911]

Yup you might be right.....but good thing We don't have that problem in Miami....

[Dr J]

Speaking of smog, I forgot to mention I put a cat bypass. In my last drive in a parking structure I was able to set off alarms just by revving the engine!

[scott.k]

dr j, thanks a ton, never seen anyone whose actually removed it all.

as for smog, no need to worry, im registering the car in the family's house in nevada, smog exempt there. but if it works with all removed, i think im going to try it. Ill just keep that coldstart think(i think thats what it is), on intake runner on cylinder 2.

What about the ECU with the auxilary air regulator?

Also, did you just plug up the holes for teh hoses?

Thanks a ton for the help
Scott

[scott.k]

sorry about my lack of knowledge, which will shown clearly here, but what about an efi system like individual throttle bodies? When you look at an engine with them set up on it, there are no valves of these types, no cold start nothing, just 6 throttles and 6 injectors?

thanks
scott

[Scott R]

You appear to be having a lot of problems with injection. I believe you also tried to mount a Holley to your engine a few weeks back? It would probably be best to source a known good working 80' CIS system and call it done.

The system you have needs to have the ECU working, and ideally the O2 sensor as well since it has a frequency valve. Either get a good working 80' system, or an earlier that has the components you don't want.

[T77911S]

you can remove all the air stuff you mentioned. just hold your foot on the gas just a little to help starting, hot or cold. that is all the aux air valve (AAV) is doing. keeping your foot on the gas after it starts performs the funtion of the aux air regulator (AAR). as for the decel valve, if your mixture is set correct and you dont have air leaks, the idle should drop to normal RPM's without any problems.

as for making the CIS even more simple, and MUCH more reliable, i like the 77-79 systems. they are the last years that did not have any electrics on them. then the only things that will leave you stranded are a bad fuel pump or ignition.

[Bob Kontak]

Originally Posted by T77911S

just hold your foot on the gas just a little to help starting, hot or cold. that is all the aux air valve (AAV) is doing. keeping your foot on the gas after it starts performs the funtion of the aux air regulator (AAR)

Good point. That would be the "manual air bypass" I was thinking he would have to rig up.

[Dr J]

Scott, this is what I did:

1) I went to Ace Hardware and purchased a rubber straight tip - like you use for the bottom of a chair 1" diameter and used a hose clamp to seal the hole in the rubber boot that connects the air flow meter to the throttle body. In your case, you can take the 90 deg piece and do a test fit at the store. (This area is shown in your 3rd pic)

2) The cold start valve has a spacer which has the opening for the aluminum/rubber line from the devices that bypass the throttle. I removed the spacer and bolted back just the cold start valve, thus eliminating that hole. I had to get new, shorter bolts for the cold start. In your case, you could just leave the spacer and plug it. (This area is also in your 3rd pic). The diameter of this piece is 0.687"

3) The smaller vacuum lines from the throttle body used for the decel valve were plugged with plugs from Advanced Auto. (This area is not visible in any of your pictures). The diameter at the throttle body is 0.198"

4) Being a 1979, I don't have a frequency valve so there is no ECU. Can't comment there. (This is shown in your 4th pic).

5) My cat bypass has a hole for an oxygen sensor which I used to add a wideband O2 sensor.

6) The crankcase breather hose goes to the oil filler tube and a crankcase vent filter for the other tube.

7) The decel valve connections at the throttle valve are 0.39"

[scott.k]

Originally Posted by Dr J

Scott, this is what I did:

1) I went to Ace Hardware and purchased a rubber straight tip - like you use for the bottom of a chair 1" diameter and used a hose clamp to seal the hole in the rubber boot that connects the air flow meter to the throttle body. In your case, you can take the 90 deg piece and do a test fit at the store. (This area is shown in your 3rd pic)

2) The cold start valve has a spacer which has the opening for the aluminum/rubber line from the devices that bypass the throttle. I removed the spacer and bolted back just the cold start valve, thus eliminating that hole. I had to get new, shorter bolts for the cold start. In your case, you could just leave the spacer and plug it. (This area is also in your 3rd pic). The diameter of this piece is 0.687"

3) The smaller vacuum lines from the throttle body used for the decel valve were plugged with plugs from Advanced Auto. (This area is not visible in any of your pictures). The diameter at the throttle body is 0.198"

4) Being a 1979, I don't have a frequency valve so there is no ECU. Can't comment there. (This is shown in your 4th pic).

5) My cat bypass has a hole for an oxygen sensor which I used to add a wideband O2 sensor.

6) The crankcase breather hose goes to the oil filler tube and a crankcase vent filter for the other tube.

7) The decel valve connections at the throttle valve are 0.39"

thanks for the help, i really appreciate it. i think i might end up doing this is any of those valves fail.

[scott.k]

hey, i was just wondering, does anyone have a wiring/ecu diagram for what plugs into what on the injection system?

thanks
scott