Distributor vacuum lines/smog removal

[djdawson2]

Today's fun includes removing what I can of the smog equipment. Looking at the distributor vacuum lines, there are 2, one red and one blue. The blue line goes through a switch before going to the intake manifold, whereas the red one goes straight to the intake.

Is the blue one used to retard timing during warm-up? Is the blue line and the switch needed after smog removal?

Thanks

[jcc911]

DJ Take a look at my thread 78 SC Turbo Conversion. There are a few diagrams there that show where these hoses go.

[jcc911]

Hope this helps.

[PrimeMvr]

The blue one retards timing at idle. I believe that when the switch is in place, it actually cuts the vacuum to that line during warm up so the idle is advanced more. The retard at idle is to heat up the exhaust gases to aid the catalytic converter. The red one retards the timing on boost to avoid detonation.

I recently found that my pot was disintegrating inside and was not functional on the vacuum side and barely on the boost side. I've seen more than one post with the same issue. I removed mine, locked my dizzy and put in a 6AL-2 from MSD to control the timing. My car is a new machine since. Check out MSD Success thread for more info if you're interested.

[djdawson2]

jcc911:
It looks like in your drawing that I could easily do away with the switch that is in line on the blue line, on my car the one that goes to the bottom of the canister on the distributor. From your drawing, it looks like you're running straight to the IM with no other gadgetry.

PrimeMvr:
That sounds like an excellent idea. However, how did you decide on a timing curve? With seemingliy infinite combinations of boost level vs. rpm it seems like this would be challenging at least.

[jcc911]

Actually the drawing was done by Profighter. He might have more insight on this.

[heliolps2]

it,s important to keep that switch for the cold start, it will increas the the idle by 300 rpms at the cold start ,along with AAR , the switch will then close after 2min , The diagram from jcc911 is the way to go just keep the switch. as for your timing it depends on what dist you have , get the number that is stamped on the side , that will tell you what the spec for your dist, and also whats the max octian in your area , and what boost , do you have an after market intercooler

[mark houghton]

That switch (solenoid) is a nice to have, but not entirely necessary. I don't use one and the AAR is sufficient to kee the rpm's high enough, in my case anyway.

[PrimeMvr]

Originally Posted by djdawson2

That sounds like an excellent idea. However, how did you decide on a timing curve? With seemingliy infinite combinations of boost level vs. rpm it seems like this would be challenging at least.

That's the million dollar question that has been discussed in great detail on this board. After hours of reading, here's my approach and I'm sticking to it.

The timing specs in the US manual are designed around emissions, not performance. With all the smog gear removed and a few mods, I believe my car to be closer to an ROW than US. The ROW spec is 29* at 4k. I backed that off to 26* because I have 8:1 CR and no access to a dyno, which would be the best method of tuning and listening for detonation.

For the non-boost timing curve, I did several hours of seats-of-pants tuning with my laptop hooked up. The 6AL-2 is sweet in that you can push a new curve with a few mouse clicks on the fly (I mean safely parked at the side of the road of course).

You are correct that theoretically there is an infinite combination of RPM/boost curves you can come up with. I kept it simple. The manual indicates that the boost retard takes out 8-10*, so I simply configured it to have 10* out by about .4 bar and keep it there. Since I'm going all in with the advance long before my engine creates this much boost, my curve is quite simple in the power band.

There is more performance to be gained by getting aggressive with the timing in the power band, but until I can get out of town to a dyno, I'm not willing to push it. I can say without a doubt my car is running great. I could barely drive it around town before. Now it goes up hills under 2k with no argument from the engine at all. I live in a very hilly area and I had to use the handbrake to get away from stop signs before with the engine reved to 2k, and even that was dicey. I wouldn't even pull out into traffic because it was so embarrassingly sluggish off-boost. Now, just let the clutch out and gas it...vroom. Love it!

[heliolps2]

Hi Mark , yes you are right , on my 930 I just adjusted the AAR to make up the 300 rpms , on the timing , well with my limited expierence with the daul vacum dist there is a ROW model and a Calfornia Model , I bought 3.3 my car in CA in 1999 thinking it was a USA 68, so I thought the timing should be at 31 btdc at 4000 rpms. come to find out just the other day that I have a ROW 66 dist and the timing should at 29 at 4000 rpms . I now live in Virgina super gas here is 93 octain , I belive that timing more important if you live in a area that has only 91 octain , when I lived in CA I blow 2 motors , cyl 5 went both times ,

I was very new to the 930 world at that time , looking back , to much timing and low octain and boost 1.1 bar !!! let me tell about the car its a 1976 911S chassi with 993 911gt body coil over with RSR shocks Tarett sways G50 / 8;32 ring & pin kennedy 600 lite clutch , and big reds brakes .
motor 1989 3.3 shuffle pined polished case new crank from Porsche , set of carilow rods ARP bolts though out the heads ported and polished and shaved to get 7;5 to 1 comp , 964 cams with ASSCO 8000 rpm valve springs with titanium retainers , bosch 4wcs plugs , Smog delete , tial WC with a high breed turbonitics Garrett turboand a full wilth intercoole and 993 Carrera heat exchangers modifyed . On the fuel side a black fuel head thats been modified to 320 mil per min ,009 injectors big fuel lines , and a 112 WUR stock , my CO is set at 2.5 %. At 3000 rpms cruze my AFR is at 14. full boost at 12.4 .
I get 12MPG City 16 HWY at the track 4 MPG , It was not easy to get to this point with alot of help o n this Fourm that I learnd it all .
Just last Month I took off one of my heat exchanger for repair ,to find that cyl 2 was really lean by its color WHITE realy WHITE so I pulled the other side , same thing cyl 5 the center cyls ,so I pulled the fuel lines and tested 30 seconds WOT got 160mml all even , nso not the fuel head , next test the injectors they tested the same. with some research , come to find out that cyl 2 and 5 run leaner in high performance applications , so I adjusted the fuel head on cyl 2 and 5 then checked the EGT with a infered gun, got it close drove it for a month ,then pulled the heat exchanger off again to see the color ,they all matched The dyno showed 428 at the rear wheels 0 to 60 in 3.9 seconds 1/4 mile 11.9 at 124 mph drive really good under 2000 rpms thats my shifting mark around town. so thank you Mark And 911st for the great forums

[heliolps2]

sorry for my miss spelling and gramer. I hope every one under stands , and I hope this helps some one out there

[heliolps2]

is their a spell check on this thing. if yes please inform me. I'm new to the Forum

[JFairman]

screw speelcheck.. different spellings from folks give posts character.

you could also write your message in microsoft word or whatever, use the spellcheck there, and then copy and paste it into a post on pelican.

[krasuskyp]

Hey Dave!

Great thread, and agreed w/ Fairman about the 'character'. I can forgive spelling / grammar all day (and ask you tolerate ahem 'mine' 8-))...

...however!

*Line-breaks* every few sentences is enormously helpful in making posts READABLE! 8-)

Funny reading about 2&5 lean and seeing the thread just now posted on 'that'... great info.

Davey, report back your findings should you remove that line / switch - I may mine as well, seeing as Professor Houghton's idles fine sans...

[JFairman]

I'm using that vacuum switch to block the boost pressure enrichment line going to the control pressure regulator until a summit racing rpm switch opens it at 4600rpm nowadays so it's not blocking vacuum retard to the distributor to help raise idle speed during cold starts anymore.

I think Mark's and mine which are both 87's don't need it for a good cold start idle because we both have MSD 8762 boost retard modules hooked up with the MSD 6al, and we both have static idle speed ignition timing advanced around 10-12 degrees btdc.
That makes the idle alot stronger and smoother and with no catalytic converter or state emission testing in Florida thats an easy big improvement in midrange response and torque below 3000rpms and before boost shows up.

[mark houghton]

I have to admit, though, that I also adjusted my AAR (by driving in a pin) to increase what I felt was too low an idle at cold....and that was before I added all the advanced timing. Now, she lights right up and idles at around 900 for maybe the first 10 seconds, then moves up to around 1100-1200 until warm enough to drop back down to about 950.

[djdawson2]

Pauly,
Well... this thread wasn't half as entertaining to me as the one about my raw fuel stench at WOT. I never dreamed that I would discover that my intake manifold was about to fall off the engine!!!

I do like the programmable ignition idea... but I'm gonna have to set aside some dedicated dyno time to switch over. For now, stock will have to do, and has always seemed fine.

As far as the switch on the blue distributor line, I'm going to leave it in place... not much of an inconvenience for good cold starts. My car seems to behave no different on cold starts with or without the blue line attached to the dist... probably because where I live (9000ft) it's probably already running fat all the time.

Dave

[heliolps2]

thanks guys , again new to this system , go it now . Has any one else experienced lean cyl 2 and cyl 5 and what did you do to fix it

[djdawson2]

Helio,
You may want to "Post a new Topic" to get better response...

Dave

[billjam]

Originally Posted by jcc911

Actually the drawing was done by Profighter. He might have more insight on this.

Actually, the drawing was done by me! And I do have a bit more info that might help if you are trying to figure out your plumbing and decide what you can do without.
The first drawing below is straight from the back of the 930 Owner's Handbook.
The second drawing is how I currently have my car plumbed. Keep in mind that it never really gets cold here, so I don't have to deal with seriously cold starts (below freezing).