CIS Performance Mods.........

[fred cook]

A lot of you have been following along on my engine build thread "3.3SS rebuild finally underway". In that thread, I mentioned that I was going to do some performance mods to the CIS to help make it work better on the new larger, higher performance engine. I also said that I would share the info once I got the engine up and running. So, here goes!

Since the new engine has Carrera heads with large ports, the first thing I did was to buy an early SC air box and runners. This opens up the intake runners to 39mm which is quite a bit larger than the later (1980-83) intakes. Even so, I had to flare the ends of the runners to match the phenolic spacer blocks that fit between the heads and the runners. The blocks measured 42mm while the runners were 39mm. So, each runner was flared about 3mm at the head end to help keep a clean air flow into the head intake port. On the other end, the SSI header flanges had to be flared out a couple of mms to match the 39mm exhaust ports. That takes care of the intake and exhaust to engine "stuff". On to the CIS work.

I guess it would be easier to name the bits that I kept from the 1980 CIS system. I mounted the air flow sensor/fuel distributor on the early air box. This was a direct bolt on. I also kept the AAR (choke), WUR, Frequency Valve (no CO sensor so working at 50%) the cold start valve and the fuel pump safety valve. The two AAVs were deleted.
Also, the throttle position switch was left on the throttle body. Since the distributor was replaced by the XDi ignition system, those two vacuum ports were blocked. New hoses were made up to go from each end of the AAR to the throttle body and the air box. I used some pieces of 90 degree bend aluminum tubing to go around corners more neatly. The WUR, Cold Start Valve and Safety Valve kept their stock plumbing.
So, at this point, what I had done was to back the CIS up to a pre-emissions layout. This helped neaten up the back side of the engine and eliminate potential vacuum leak locations. Next, I added a momentary contact switch mounted on the non moving portion of the throttle linkage. It is wired into the leads to the cold start switch so that when the throttle goes to wide open throttle or WOT position, the cold start valve is actuated. At this point it acts as a 7th injector to add fuel into each intake runner. This action is completely automatic and ONLY happens at WOT. I have been using an Innovate air/fuel ratio gauge to set the CIS. At this point, the engine runs at about 14.5 which is very close to stoichiometric (best setting) while doing normal driving and will drop down to about 13.5 or so at WOT. This should give good fuel mileage and good top end power. It will also help prevent the system going lean and burning a valve. I currently have about 200 miles on the new engine and it starts and runs well with good power indicated while doing 2k-4k and 3k-5k power pulls in 3rd or 4th gear. I have just reset the ignition interrupter from 5k up to 7500 rpms but have not driven the car since doing so. Once it hits the 500 mile mark, I will change the oil/filter, check the valve adjustment and the head nut torque and then consider it ready for day to day service. If I find any issues with the CIS operation or decide to make any other mods, I will post the info on this thread. Also, at some point, I will take the car and put it on a dyno to see what the hp and torque are for this engine setup. I am expecting good midrange torque and top end horsepower! We will see what happens!

[boyt911sc]

Originally Posted by fred cook

A lot of you have been following along on my engine build thread "3.3SS rebuild finally underway". In that thread, I mentioned that I was going to do some performance mods to the CIS to help make it work better on the new larger, higher performance engine. I also said that I would share the info once I got the engine up and running. So, here goes!

Since the new engine has Carrera heads with large ports, the first thing I did was to buy an early SC air box and runners. This opens up the intake runners to 39mm which is quite a bit larger than the later (1980-83) intakes. Even so, I had to flare the ends of the runners to match the phenolic spacer blocks that fit between the heads and the runners. The blocks measured 42mm while the runners were 39mm. So, each runner was flared about 3mm at the head end to help keep a clean air flow into the head intake port. On the other end, the SSI header flanges had to be flared out a couple of mms to match the 39mm exhaust ports. That takes care of the intake and exhaust to engine "stuff". On to the CIS work.

I guess it would be easier to name the bits that I kept from the 1980 CIS system. I mounted the air flow sensor/fuel distributor on the early air box. This was a direct bolt on. I also kept the AAR (choke), WUR, Frequency Valve (no CO sensor so working at 50%) the cold start valve and the fuel pump safety valve. The two AAVs were deleted.
Also, the throttle position switch was left on the throttle body. Since the distributor was replaced by the XDi ignition system, those two vacuum ports were blocked. New hoses were made up to go from each end of the AAR to the throttle body and the air box. I used some pieces of 90 degree bend aluminum tubing to go around corners more neatly. The WUR, Cold Start Valve and Safety Valve kept their stock plumbing.
So, at this point, what I had done was to back the CIS up to a pre-emissions layout. This helped neaten up the back side of the engine and eliminate potential vacuum leak locations. Next, I added a momentary contact switch mounted on the non moving portion of the throttle linkage. It is wired into the leads to the cold start switch so that when the throttle goes to wide open throttle or WOT position, the cold start valve is actuated. At this point it acts as a 7th injector to add fuel into each intake runner. This action is completely automatic and ONLY happens at WOT. I have been using an Innovate air/fuel ratio gauge to set the CIS. At this point, the engine runs at about 14.5 which is very close to stoichiometric (best setting) while doing normal driving and will drop down to about 13.5 or so at WOT. This should give good fuel mileage and good top end power. It will also help prevent the system going lean and burning a valve. I currently have about 200 miles on the new engine and it starts and runs well with good power indicated while doing 2k-4k and 3k-5k power pulls in 3rd or 4th gear. I have just reset the ignition interrupter from 5k up to 7500 rpms but have not driven the car since doing so. Once it hits the 500 mile mark, I will change the oil/filter, check the valve adjustment and the head nut torque and then consider it ready for day to day service. If I find any issues with the CIS operation or decide to make any other mods, I will post the info on this thread. Also, at some point, I will take the car and put it on a dyno to see what the hp and torque are for this engine setup. I am expecting good midrange torque and top end horsepower! We will see what happens!

Fred,

Very interesting to know the result of the dyno test. BTW what is 'safety valve'? Two (2) AAV's? Thanks.

Tony

[fred cook]

Originally Posted by boyt911sc

Fred,

Very interesting to know the result of the dyno test. BTW what is 'safety valve'? Two (2) AAV's? Thanks.

Tony

My bad, I should have said safety switch, the fuel pump cutout switch. Yes, 2, the 1980 and later SC used two of them for emissions control purposes.

[boyt911sc]

Originally Posted by fred cook

My bad, I should have said safety switch, the fuel pump cutout switch. Yes, 2, the 1980 and later SC used two of them for emissions control purposes.

Fred,

Hate to disagree with your CIS information. Since we are in the technical forum, there is one (1) deceleration valve, one (1) AAR, and one (1) AAV (auxiliary air valve) in '80-'83 SC's. Where is the other AAV located?

BTW, I like what you did to your new engine. Thanks.

Tony

[fred cook]

Originally Posted by boyt911sc

Fred,

Hate to disagree with your CIS information. Since we are in the technical forum, there is one (1) deceleration valve, one (1) AAR, and one (1) AAV (auxiliary air valve) in '80-'83 SC's. Where is the other AAV located?

BTW, I like what you did to your new engine. Thanks.

Tony

Looking at the left rear corner of the engine. Both of these valves carry the same part number (1980 SC engine). One could well be used for decal purposes as it has one port that is not covered. My bad! Guess I just got a bit lazy in my descriptions. Anyway, both are now removed as is the heater blower motor and mount shown further to the right. This picture was taken during a "cleanup" exercise done several years ago on the same engine.