D,

Thx much for the info.

If I may ask, how did you establish -16 @WOT? Did you set it up on the dyno? Is that at 1 bar boost?

I belive -16 is close to what the US 930 comes in at.

i picked -16 basically from reading this post. Figured it would be a safe number to start with. My timing at idle and cruise was determined by just driving around and trying different things till it felt right. Yes I run 1 bar

i'm going back to the track Wed night to see how the intercooler is working

Ahhhhh....that 'splanes it then! I thought I saw a meltdown on the horizon.

I'd like to know how anyone knows what the timing is if the only 2 marks* on the crank pulley are 0 and -26 degrees BTDC that you line up with the slash on the fan housing with a timing light at idle and 4000rpm with distributor vacuum hoses removed?

*not including the other TDC marks you use when doing valve adjustments

My 1987 AC pulley is 5.25" and it's sandwiched against the crank pulley that is about 7/16" smaller than the AC pulley in diameter.
If i could find a degree wheel thats 5.25" in diameter than I could glue it to the AC pulley and use a timing light but the slash mark on the fan housing is almost 2" from the edge of the AC pulley.
I've heard of degree'd tape that you can maybe stick onto the edge of one of the pulleys but it would have to calibrated for the diameter of the pulley.

How do you guys know what your timing really is other than 0 and -26 with the stock pulley(s) and a plain old xenon timing light with no advance dial on it?

Use a small triangle file and cut marks into your stock pulley. Measure from TDC with a flexible ruler. Calculate your dimension per degree by using:

in/degree = Diameter x PI / 360

In your case:

5.25" x 3.14159 / 360 = 0.0458"

It's easier to put a mark every 4 or 5 degrees:

4 degrees = 0.1833" (about 3/16")
5 degrees = 0.2291"

That's exactly what I have done, but used a permanent marker for each 5 degree mark.

my mechanic is very good at setting up crank trigger ignitions and has verified my "real" timing matches what the megasquirt is showing.

mark- thanks for looking out, i don't need any melt downs. This thing is running so good right now it's just a joy to drive.

Guys I"ve just read this whole thread.. Wow!! So there should be two threads.. One entitled "how the stock ignition works".. and one "how we want our ignition to work"..

So there's a thread over on the engine rebuild section http://forums.pelicanparts.com/911-engine-rebuilding-forum/437273-using-coil-pack-ignition.html

They are talking about using standard coil packs.. The standard Audi 1.8 pack is of interest to me as I have 210k on my audi without a failure and they are cheap.

So why not a unit like the MSII interfacing to these ?? Or John @ JS what about modifying your knock control unit to interface to coil packs ? REALLY clean and cheap..

Seems like the info on what SHOULD be a map is out there.

Reading this whole thread is most impressive. I would probably be well served to do it again myself.

I would be interested in learning the difference in spark intensity between the different systems.

It is hard to beat the stock CDI distributor system as to how much power makes it to the spark plugs. MSD is one exception for several reasons. I believe most wasted spark systems like the TEC's are not as intense but as they are often teamed up with a twin spark system where such benefit may offset there weakness. Usually mappable timing also comes with such a conversion which should be a significant benefit by its self.

Not sure about the coil packs but would like to know more.

With the high effective compression ratio a boosted motor achieves an intense spark becomes more important. It is interesting how much effective compression increases effect ideal spark plug gaps. That is a NA motor running 8.5/1 CR can run a lot larger gap than a motor running close to 13/1 effective CR. I suspect the rich AFR's we need to run on boost may exaggerate this further.

If we can just keep our AFR's where they need to be (i.e. lean surge off idle & fat on first boost) and the timing is closer to an ideal, we should be just fine.

To me, must modifying the vac/boost retard limiter for more retard from the pot and setting the on boost timing and AFR's on the dyno would probably the biggest bang for the buck.

The next significant step up being a programmable ignition curve tuned on the dyno with temperature compensation.

I posted in a knock sensor thread about a version that interfaces to an EDIS and coil packs.

http://forums.pelicanparts.com/4983455-post94.html

John , just started reading it.. so does your system allow plotting of boost vs retard/advance vs rpm ? If so it sounds like it's perfect!!! How much are we talking ?

Probably best if you follow that up on the knock sensor thread or directly with John.

Thx.

Use with megasquirt or other ECU if you want fully mapped timing.

I did complete the pressure test on my brand new distributor capsule. I confirmed that with equal pressure on both ports, there is no advance or retard. I used a test pressure of 10 psi (0.7 bar).

With 10 psi on the outside connection only, full retard is produced. With 10 psi on the inside connection only there is no change in timing produced.

I don't think we ever got a valid test on the timing solenoid, as to whether it cuts off pressure to the inside connection at full throttle. Based on this test, I still think it must. At full boost both ports should have the same pressure, assuming the thermal valve has opened up.

I am unable to do this test as I have converted to EFI and full electronic timing control. Can someone do this test?

Maybe I didn't read your response properly, but a CIS system doesn't only spray for 2 revolutions, a CIS system starts spraying as soon as the throttle flowmeter plate moves. CIS= Constant Injection System. It is very difficult to atomize fuel properly at idle with this system if you use big intake ports, not a problem if emissions are not of concern though.
Bernie

I have a digital timing light you just line it up with the mark on zero then turn the knob one the back of the light to get the setting you want then adjust the distributor accordingly. oops didnt read it all mine has an advance dial Just go buy a new timing light!!!!

SpeedySquirel,

Yes. How we get boost retard is still an important and somewhat of an unverified point. Is the solenoid in the vac-retard side critical to getting retard on boost or can the pot on the dist deliver boost retard without it?

Per your tests it seems the solenoid must close off the vac-retard side to keep it from getting an offsetting boost signal and hold it from retarding on boost.

If this is the case, all we need is for the solenoid to close off idle and the TPS would be part of this.

Maybe using the solenoid is part of getting vac-retard only at idle and keeping it from happening at higher rpm with throttle lift to minimize emissions and popping in the muffler. (rpm & throttle position)

Part of me knowing how the Retard-Pot works wants to believe it will still retard with boost to both sides but that would go against your test results.

Thus, we need someone to hook a connection up to the solenoid and see if it closes off idle and under what conditions.

I believe at least one of our 930 experts runs without this solenoid and feels it is not necessary.

Would love to get to the bottom of this one.

"oops didnt read it all mine has an advance dial Just go buy a new timing light!!!!"
lol... you're right!

I tried the math formula someone posted. Measuring and marking the pulley with a sharpee pen approximately every 5 degrees ~ 3/16" with the alternator and AC belt on there is almost impossible.
You would have to remove the pulley and file in tiny marks for every 2 degrees with a knife file and dial claipers for measurment and then rub some white paint into them and wipe the rest of the paint off the surface to see them.

I bought a harbor freight timing light with the advance dial recently when it was on sale for $15 and returned it because it didn't work right at all.

I have an old sunpro timing light thats say's made in USA and works fine but doesn't have the advance dial so guess I got to get another one.

[QUOTE=911st;5043599]
I believe at least one of our 930 experts runs without this solenoid and feels it is not necessary.
QUOTE]

I am far from an expert, but I am one that does not have the solenoid you speak of; my understanding is that it functions solely to delay timing retard for a short period after initial startup to increase the cold idle. All I have is the thermal valve which opens at about 150 degrees F.

It's still somewhat of a mystery to me as to how boost retard is initiated. The only thing I might offer is that the two lines attached to the distributor have their source connections at a different point in the throttle body assembly, and I'm guessing that vacuum and/or boost signals will be different based on where the ports are located relative to the throttle plate. With that, I'm also guessing that even under wide open throttle, there will be a difference in the amount of pressure that each line sees, i.e., the pressure won't be equal to both sides of the distributor timing can. It may be that differential that causes the timing to retard under boost.

Hi Mark, I have the MSD 8762 boost retard like you and the distributor turned clockwise in it's slotted adjustment as far as it will go. From looking at the pulley with a timing light it looks/guessing like that puts the idle timing at around -8 deg. with both vacuum lines on the distributor.

With things set up this way you don't want the little idle vacuum retard solenoid blocking the vac retard at idle because idle timing becomes advanced too far and idle goes higher and is rough.. just too much advance at idle.
Just pull the vacuum retard line off the pot while the motor is idleing cold (carefully with the fan just 3" away) and you'll see what I mean.

Mine starts up cold and idles at 1100rpms smoothly without the cold start vacuum retard solenoid and only the cold start TB aux air bypass valve working so you just don't need that vacuum solenoid when the idle timing is advanced like an older car without vacuum retard emission controls to increase exhaust temperature to make the catalytic converter work better.
After a few minutes with the aux air slide valve warmed up and closed it idles steady at 800rpms.

Mark, I've been wanting to ask where you have your MSD 8762 settings?
We both have '87 cars so our distributors should be the same.

I have the distributor advanced all the way as far as the slot allows without reindexing the distributor gear.
The 8762 retard start control on the side of the box set to start retarding at 5psi and the seperate retard slope control knob mounted in the car is currently set to retard timing 2 degrees for each pound of boost.
Trying less boost retard under full boost doesn't make it pull any stronger and I think I can hear the beginning of spark knock, but no high pitched pinking or detonation from the engine while the windows and sunroof are rolled up to reduce wind noise.

If I turn the slope control to retard timing 3 degrees for each pound of boost over 5psi while accelerating at 1bar boost I can feel the power drop off.

Turning the retard slope knob on the 8762 on the fly reacts very quickly. I like it.

Here's a pic of the 8762 retard slope knob in the car mounted on top of the autoheat box.
http://forums.pelicanparts.com/uploa...1259783630.jpg

and the 8762 box showing the lockable boost retard start point screw set to 5psi.
http://forums.pelicanparts.com/uploa...1259783712.jpg