911SC Turbo

[sammyg2]

EFI would be a good solution for many, but not for me. I like CIS, it is simple and reliable and functional.

I think it would be a little easier for me to change a fuel pressure regulator than an entire fuel injection system.
The only time I would consider changing to EFI would be if the car was smog exempt and the CIS was completely shot. Obviously others have a different opinion of CIS

[tsuter]

911SCs didn't come with EFI. They are 100% mechanical and K-Jetronic is sophisticated and easy to work with and tune. I'm keeping it that way with mechanical modifications only. Keeping it in the technology of the period is a lot of the fun. I have other vehicles with programmable EFI... one using a MAP sensor and one with a MAF!

Sammy, regarding the BOV versus a DV, the fuel is long since in the intakes when that BOV opens. When the throttle closes, the sensor plate falls and shuts off fuel mechanically and immediately. The turbo outlet pipe (pressure side vents air) senses the vacuum and vents the compressed air side without affecting the sensor plate. If a DV was in place to recirculate air to the turbo inlet pipe it could even blow back the sensor plate. Something you don't want.
The BOV should get a better sound as well.

[tbitz]

What are you guys using for boost retard on the ignition?

[tsuter]

Sammy, the sensor plate height exposes slits in the fuel distributor for the fuel. More height = more air in = more slit = more fuel. You would have to raise the fuel pressure quite a bit to get enough more fuel. With the enrichment injector you are increasing fuel by 16% i.e., 7/6 when it opens. This would take a 35% increase in fuel pressure to match or an increase from 60 - 80 psi. I think that would be difficult and problematic although certainly people run fuel pressures to 100psi.

Also with the enrichment and under 10psi boost no intercooler is required as the extra fuel cools the mixture and richens it enough to avoid detonation.

Some people just shim the fpr but then you are getting the higher fuel pressure across the range as opposed to when you need it. In my case, I open the erichment CSV at 3psi boost.

Re: the O sensor for AF meter, put it in front of the turbo in the header as it needs to get really hot to work correctly. Or maybe a four wire heated sensor will work further back where the bung is easier to install.

[tsuter]

tbitz, you don't really need ignition retard under boost if you use supplemental enrichment as that solves the detonation problem and keep the boost under 10psi
I also mechanically limited the distributor to 20 degrees total advance as well (10 and 10). Set at 5 BTDC and then 20 degrees of mechanical advance for a total advance of 25BTDC.
That's for CRs of 8.5 or less.

[sammyg2]

Tsuter, on your distributor modifications, I may need a little better explanation.

I read the BAE manual and it described two pieces of steel 180 degrees apart, unsupported at he top that need to be bent in at the top equal amounts for a distance of about 2 1/2 to 3 mm to achieve a total mechanical advance of 20 crankshaft degrees.

A couple of questions:
Bent in at the top, does that mean towards the center? The 2 1/2 to 3 mm, is that total or per side? thanks.

PS, yes, I'm at the point where I need to do this.
I installed the MPC and got up to 7 psi, but I MAY have heard pinging. not sure, I got out of it fast but it did sound like it.
I backed it off to 5 1/2 psi and I'm going to keep it there until I get the hobbs switch hooked up with extra fuel.

Oh yeah, another thing:
I have two vacuum hoses going to my dizzy. I believe one is vaccum advance and one is vaccum retard.
I need to do my homework on this one to see what affect boost has on the two different mechanisms, if anyone has any knowledge on this please share. thanks.

[tsuter]

Sammy, I would not attempt to recurve the distributor unless you need to. The enrichment CSV may solve all detonation up to 10psi with your stock ignition curve.
In any case I can't remember the specifics on the mod to the distributor. It was done by a "professional" on a little machine... distributor machine?? Not a pair of needle nose pliars!! Little weights centrifugally crawl up those metal shafts. There are two advances - one beginning around 2000-2500 and another around 4000-4500 as i recall. You would limit both to 10 degrees. But find someone to do it if you do it.

Use the Decel fitting/nipple on the back of the TB for the Hobbs switch. This way it cuts off immediately on throttle close.

I'm also connecting the BOV vacuum line here ... see T fitting and vacuum line coming off the line to the Hobbs pressure switch.



Regarding the vacuum advance and retard lines to your distributor, I just left them connected per stock. You still have vacuum as soon as you lift off the throttle so they'll still work subject to any mechanical limitation you may make in recurving the distributor.

[sammyg2]

Cold start injector question (stock location):

The injector is supplied with power from the start circuit which grounds through the thermotime switch, right?

What changes when the thermotime switch gets warm?
Something has to change to keep the cold start injector from firing when the engine is warm, I'm just trying to figure out what it would take to bypass it and have it inject on demand.

I read a post in this thread about using a double pole pressure switch but i'm still not clear on how the system is supposed to work.
I'm not even sure my system is working the way it should be right now.

[sammyg2]

O boy, another question:
I was reading my bosch fuel injection manual yersterday and read about how the warm up regulators on turbo CIS cars have a vacuum line on the WUR that senses boost and changes the control pressure, similar to if the engine were cold.
911SC's don't have that, do they? I don't remember a vacuum line going to my WUR and I can't see one just by looking. I wonder how much a 930 WUR would cost? Never mind, Dumb question. I can't do without an arm and a leg.

I have a hobbs switch, I have a cold start injector off a BMW CIS engine, I'm just trying to figure out a way to do the enrichment without cutting into the stock fuel lines and drilling, tapping, welding on the turbo outlet pipe. maybe I should just do it, can't be that bad.

Tsuter, when you mounted the injector in your turbo outlet pipe, how'd you do it? Just drill three holes and tap two for the hold down screws? i need to go back and see how you did the fuel line tie in.

I need more fuel at boost but if I richen up the mixture any more it affects idle.
backing off on the boost is no longer an option.
5 psi doesn't work any more because I have tasted 6.
6 won't be enough because I want 7.
7 won't be as nice as 8.
This is sick.

[ohecht]

Sam,

Just a small part of the puzzle, but my WUR (SPR) on my 82 SC has a vacuum connection and line going to it. I believe it is for altitude compensation, but it could probably be made to work for boost.

My understanding of the CS injector circuit (it has been a while since I looked at the wiring diagrams) is that the circuit is grounded by the thermotime switch only when the switch is cold due to low engine temperature, the starter is turning, and the "time" aspect of the thermotime switch has not elapsed. I believe the timer portion is just a very sensitive bimetal strip or the equivalent that will only keep the switch closed for a few seconds when the current is flowing for any reason. This prevents flooding the engine if the other two conditions are met (engine cold and starter turning), but the engine won't fire for some reason or takes more than a few seconds to start.

Again, off the top of my head without looking closely at the diagrams, I would think you could run a separate path to ground for the injector that bypassed all of these elements, and also allows them to continue to work for cold starts. Once the engine is running and not on boost, the injector would function as stock, as the new path you ran to ground would be open at the Hobbs switch. On boost, the Hobbs switch closes, and the injector operates independently of the fact that the other path to ground is still open. Theoretically, I can't think of any conditions when you would get unwanted operation of the cold start injector or when it would not work when needed.

Again, this is with no specific knowledge of these components, just a basic familiarity with their function and my long history of making separate circuits on cars to run things under different conditions than those for which they were designed.

I like the cold-start injector solution because it is simple, uses existing components, and I think the biggest advantage would be the way the late airboxes send the fuel from the injector right into each intake runner. You would get the additional fuel practically as soon as possible without using the CIS injectors themselves.

Olivier

[iamchappy]

Join the club,
I think if you follow with Suters plan and maybe a MSD BTM for retard like me. You
can have 8 or more. Suter has been pretty successful running his. Fuel and timing are the keys to more boost. A few metric to AN adapters and you can tap into your fuel lines without cutting and clamping, The CSV
mount is a problem with the BAE pop valve
thats why I went with the BOV, I am putting my CSV where Suter has his and welding the BOV to the intake pipe upstream of it . It may cost you 500 bucks to get it done right but it should work. I picked up an analog Westach af and a Dynatune led af to monitor the mixture when it's running. It should be all together in a couple of weeks still waiting on my back ordered wastegate.

[iamchappy]

I too like the idea of using the engines CSV for enrichment Suter was worried that the fuel may not atomize evenly through all intake runners. I would like to see how the fuel squirts out of the CSV runners into the intakes, I like the theory.
Here is a picture of my cockpit controls and guages.

[sammyg2]

On the early CIS engines the cold start injector may not distribute evenly to all culinders but on the later ones they are improved.

Oh well, I decided i'll just do what he did and install the spare CS injector in the pipe and tie into the fuel lines.

That is unless I can come across a DP hobbs switch for a reasonable cost...................

[tsuter]

Sammy using the stock CIS CSV with the internal manifold won't work unless you find a way to blow air thru the internal manifold. That does happen on cold start as the AAV is open, but when warm, there won't be any air movement and the fuel won't get distributed.
Also to use the existing CSV you would need a DPST relay activated by the Hobbs switch. That is because as mentioned above you will need to provide power and a ground to the CSV since the thermotinme switch when warm will not be provind a ground.

So best is really just to add another CSV and plumb it in.

[tsuter]

So gents, my turbo inlet and outlet pipes are at a powder painter since I just had the Tial BOV flange welded on and I've been getting tired of dinging up the paint.

Anyway todays project was to install a boost gauge.

I won't spend $200+ for a 3" VDO boost gauge and $70 for a "Porsche" tubing kit so I went to egauages.com and bought a $36.50 2 1/16" VDO 1-15 PSI boost only gauge and a $7.95 tubing kit!!!

No way I'm doing a cheap azz install in the clock position with a small gauge so I decided to install it below the AC controls. Not the best location but so what! Its a play car anyway!.



Just unfastened the AC controls and console box and screwed a $4.95 VDO bracket on the bottom



Routed the capillary tube through the tunnel and out by the transmission and up to the motor.



Used some vacuum hose at various points on the capillary hose to reinforce/protect it.

[tsuter]

Extended the capillary hose into the engine compartment. I must say getting it routed and tied down was a PITA. Maybe the Porsche $70.00 tubing kit is easier???



In any case its all in now and back together. The 0-15psi boost only gauge should have good scaling compared to a 2.0 bar gauge that'll I'll be into only for 8-10 psi.

The thing on top is a three band equalizer for the stereo so power was close for gauge lite.



I'll still swap my 3" working clock for a 3" VDO boost gauge. Even up.

[sammyg2]

Looks very similar to what I did, except mine is under the knee pad just to the right of the steering column.

running that tubing without kinking it is lots-o-fun, isn't it?
Going through the tunnel I was afraid it would rub against something and get a leak so I fished it through some 1/4" nylon tubing just for added protection in that section.

I have a spare 3" oil level guage that I plan to modify to hold my air/fuel ratio gauge that will take the place of my working clock.
I'm going to try and install the a/f guage inside the oil level gauge.
If I did it right it will look like it belongs there. If not, oh well.

[tsuter]

Got the turbo inlet and outlet pipes back from the powder painter today and fitted the Tial BOV. Looks OK. Next step is to put things back together and hopefully be on the road sometime tomorrow for a checkout drive.

[iamchappy]

Thad VNice.
I should have all my stuff together by the end of next week, I have been sort of a blingaholic of late waiting for my parts to show up. Mounting gauges running wires and PITA pressure gauge line, painting brakes and shocks, aluminum pedals and floorboard bling stuff. I cant wait for the real fun to begin.

[tsuter]

Well here it is installed! Big azz Tial BOV sitting in the turbo outlet pipe.

The BOV vacuum hose goes to the decel nipple on the TB. Actually a "T" line shared with the Hobbs pressure switch for enrichment.
The other lines on the turbo outlet are the control line to the Turbo XS boost controller (blue thing on left) and a nylon capillary tube (white curling thing) to the newly installed boost gauge up front.

That line (boost gauge) is temporary there so not yet tucked away too clean but I had an extra NPT.

The fuel enrichment CSV is mounted in the lower side of the turbo outlet on a barely visible flange just before the turn into the TB.

Be driving tomorrow!!