Strange running 930 after engine rebuild. Thoughts?
 

I would like to ask the 930 turbo experts for help in diagnosing my poorly running engine issues.
It is a 1987 930 turbo all stock except for a 1 bar boost spring and an adjustable BL-WUR.
This past winter I had a local wrench rebuild the top end of the engine as I had a broken head stud. The car ran surprisingly well even with the broken stud. I installed an Innovate wide band A/F gauge about a year ago and before the rebuild the engine would idle at 13.8, cruise at 14.0 and while under boost run 12.3 plus or minus .2 so it never ran what I would consider lean. I had the A/F gauge on there for a while before rebuild so I know how it ran before all this.
Now after the rebuild it runs lean. I have the idle set to 13.8 and it idles at 950 steady as a rock. When I press on the throttle jus a little bit it immediately goes lean to 16.5 – 17.0 and won’t have good throttle response at all. Not drivable at all. All this is taking place while parked and is no different while driving. I don’t run it as its way to lean for a turbo. It also will pop when you try to give it more gas pedal.
I checked the WUR and it’s right on spec. I even removed the adjustable BL-WUR and installed my stock non adjustable one and it ran the same. So it’s not the WUR
Fuel specs are 6.75 bar system pressure.
Non adjustable WUR:
2 bar at 50 deg F cold pressure
3.9 bar warm up pressure
2.9 bar @.5 bar pressure on the boost port.
These specs are the same before rebuild and it ran great.
Timing is set to 2 deg BTDC vacuumed hose installed.

So my question is what would make it go lean just off of idle and stay lean through out to WOT?
Keep in mind this engine has maybe 2 hours on it.
One thing I noticed is there was no vacuum on the hose that hooks to the outside of the pot on the dist. shouldn’t there be some vacuum at idle on this hose?

I’m wondering if there is a vacuum leak somewhere.

OK fellow Pelicans what do you think it is?

If you had a serious vacuum leak I would think your idle AFR would show it as well, but maybe not. Try squirting starter fluid or brake cleaner around all the intake injector blocks. Perhaps your wrench over-torqued them and cracked a couple to where they're sucking air.

Couple other thoughts: I wonder if the metering arm is moving freely. Almost sounds like it's not, since you go instantly lean when pressing on the gas. If the arm doesn't pull down in response to air flow then you wouldn't be getting the fuel needed. Don't know why this would be affected by a top end rebuild, though, but you never know. Pull off the air cleaner and push down on the metering plate to see if it moves freely. And/or, start the car up and push down on the mixture adjusting screw to where it contacts the metering arm and push further to see if your car will stumble from being overly rich.

One other thought: There is a frequency valve back behind the fuel distributor that's part of the Lambda system. If perchance your wrench had unplugged the wiring to it, you will see a very lean condition that cannot be corrected with any amount of adjustment. Do a listening check: Turn the key but don't start the engine. Force the pumps to run by pulling the green connector behind and on the left side of the fuel head (it connects to the metering arm via a micro switch). Pulling the plug will make the pumps come on as well as the frequency valve. You should be able to hear the valve's obnoxious buzzing. And while doing this test, go up front and pull each fuel pump relay one at a time and listen for the affected pump to stop running....just to confirm that both pumps are operating.

That's a start, anyway. More help to come I'm sure.

Have you verified ignition timing?

Edit: see that you are 2 degrees BTDC at idle vacuum hose connected. Depending on year, the test should be done with the hose connected, or disconnected...there should be a sticker in the engine compartment that denotes the spec for your car.

What about firing order? It's pretty easy to mix up a spark plug wire or two.

Start with the easy stuff.

Mark: The metering plate moves freely like a ballance beam scale and once there is pressure on the system when the pumps are running there is a slight pressure or stiffness to the metering plate. I think thats normal? Anyway it feels the same as when it ran well before rebuild. I will check the intake blocks for cracks / vacuume leaks. I know they are new and hope there not cracked from overtightening. I will check the frequency valve. I don't remember any noise comming from that area. The only noise I could hear was the pumps.
I did check the pumps and both are running. If there was only one pump running wouldn't the system pressure be low? I want'ed to spray something on the intake blocks but worry about a fire. Is there a way to hook up a vacuume guage to the engine and see if the vacuume is correct? If there is what should the reading be?
The mixture screw on the fuel dist.will change the engine speed and seems to work as it should. One note though with reguards to your first line about the idle being affected by a vacuume leak, the idle screw seems like its close to being bottomed out like 1/4 of a turn from being bottomed out to get the idle to 950 warm. Isn't that an air bleed screw? That may point to a vacume leak as It wasn't like that before. I wonder just how much of a vacuume leak it take to get an engine to run lean like this? Seems like it needs to be quite a large leak to have an effect like this but not sure. The reason I say this is avery one of the old intake block were cracked and the engine ran good. By the way I did check the AAR and it works as it should. Compleatly closed after about 3 or 4 min and no leaks there.

Jwasbury: I will check the firing order but I think it runs to good at idle ( like before rebuild) to be out of wack but will check anyway just to scratch it from the list. Ing. timing is supposed to be 26deg at 4000 rpm. The starting point is 2deg at idle. I know this from the before rebuild settings. It's close like plus or minus 2 deg as it sits now.
Keep the ideas comming and I will check them one at a time. I'll keep you posted.

Update:
Ok Sprayed starting fluid in the vicinity of the intake blocks and instantly the idle went down as the A/F ratio went to 10.1 from 13.1 (cold engine) pig rich. This is with the air cleaner and IC on so couldn't pinpoint the exact location of the vacuum leak. I'll remove the IC and air box to pinpoint the leak. Question. I never ran the engine with IC and air box off. If I block off the AAR I should be OK to just idle the engine to check it right? Or is there anything else I need to do?

Without the IC hooked up, there will be no air drawn down through the fuel distributor metering arm and since it won't deflect, the fuel pumps won't run and the fuel distributor won't open up the necessary ports to send fuel to the injectors.

With some creativity a person can hit the local hardware store and scab together the necessary parts to link the throttle body intake with the fuel distributor housing. I've seen a few posts here for that but would have to do some searching.

I may not have to run it with IC removed. Just finished removing IC, Air box and BOV housing and found all of the intake manifold nuts were loose. When I say loose I mean 1/2 of them were backed off 1/3 of a turn and the rest were just barley tighter than finger tight. So my next question is if these were torqued to specs would they have loosed up in 2 or 3 hours of run time? I think not. Has anyone tightened up the manifold only to have them loosen up that much? The intake block and gaskets are new and I was told they were Porsche parts. Your thoughts please?

tighten them up see how it runs. might be super easy solution

I could do that but I a little peeved right now as I just spent a lot of money to have some one do this. I have to wonder what else is loose. Not something you want to find right after a rebuild. OK I looked but can't find the torque specs for the manifold. Anyone know what the proper torque is for the nuts on the manifold?

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/624311-torque-specs.html

Ronnie's.930
Thank you.

And FYI- as I recall, several of them won't be reachable with your torque wrench socket setup, so get a feel for what 18 ft lbs feels like with a box end wrench on some of the easy ones so you aren't way off on the ones you need it for.

Personally, I would be super pissed at the wrench that you paid good $$$ for a "quality" job. No excuse, those should not just back themselves out if they had been properly torqued in the first place.
Beyond all that, it does appear you've found your problem. Every cloud has a silver lining after all.

Update, Tightened up the manifold, rechecked the timing and noticed that the vacuum hose, the one that has a vacuum on it at idle, was connected to the retard side of the Dist. vacuum pot. Moved it over to the outer vacuum port and swapped the boost hose to the retard side of the pot. Runs better but not as good as before the broken head stud. I'm not impressed at all with the rebuild and all of the rookie mistakes that were made so contacted the owner of the garage and will drop the car off. This has got me really pissed off. The owner is a good guy and I know he will make it right but it hard to keep calm.
Thanks in advance for letting me vent.
I don't know how SCHNELE did it!

Yes let him go over everything, maybe he rushed it. Timing, fuel pressure, air leaks etc. I would be pissed also but just be a little patient ,maybe you will learn some things as you stand over his shoulder this time.

What's your timing at at 4000 RPM? If AFRs are good, there isn't too many other easy things it might be (i.e., cams are not timed correctly?)

I have been diving into it more and have found this.

Ing. timing is confusing. Starting point for a 930-68 USA is supposed to be 1 +/- 2 deg ADC and final is 26 +/- 1 deg BTDC. at 4000 RPM. I don't have someone to help this week so I cant check 4000 RPM. Doesn't matter because I runs so bad I'm afraid to rev it to 4000. Seems to run better when I turn the distributor all the way to the end of the slot. Dist turned CW to the end of the slot. Throttle response is good. but timing marks off when I check it with a timing light. Around the mid point between TDC and the 26deg mark. Also the vacuum line that has actually has a vacuum on it with the engine warmed up was connected to the retard side of the pot. The side closest to the dist. housing. I switched that around to the outside of the pot away from the dist body. Not sure but if they placed the distributor of by one tooth would that have the same effect? Don't know about the cam timing. He says he has it right but he did say if was off when he checked the engine before rebuild. Not sure about that either as if he cant set the timing right what's to say he has the valve timing right. What a mess.

I also don't have anyone to look at the tach and tell me when the motor is spinning at 4000 rpm while I'm back there working the throttle by hand in the engine compartment.
It needs to be up to 4000rpm because checking the ignition timing at 4000 rpm with the vacumm hoses disconnected from the distributor is only checking the total centrifical advance.
There is no more centrifical advance above 4000rpm because it is maxed out by then.
This is what I do and maybe it will work for you.

I sit in the car and rev it to 4000rpm and I listen and try to remember the sound of the motor like a musical note or pitch at 4000 rpm. Then I go back and rev the engine up by hand on the throttle butterfly linkage and listen for the same engine sound or pitch to the rpms while watching the timing light to read the igntion timing.
To make it easier you can rev it to 5000 rpms and the timing wil be the same as 4000 rpms because the centrifical advance is already maxed out and won't go any higher. So, if you're reving up it by ear like I do, go a little higher than 4000rpms to check maximum centrifical advance just to be sure. It won't hurt anything and the timing will be exactly the same.

As far as your distributor vacuum pot hose locations, on an '87 distributor the vacuum hose that has vacuum at idle should be on the vacuum retard pot like it was. Thats the one on the right closest to the distributor body.
You said you changed that hose to the other one which is the vacum advance and boost retard pot so you now have it wrong.

The vacuum retard line only has vacuum up until around 1500 rpms and then it goes away because the edge of the throttle butterfly changes in relation to the tiny hole in the throttle body bore above that point so it no longer has vacuum similar to intake manifold vacuum there.
It's purpose is to retard timing at idle and during closed throttle deceleration to lower exhaust emissions and heat up the catalytic converter. It does that because retarded ignition timing has higher exhaust temperature.

You should put the hoses back where they were because the way you have it now you no longer have vacuum advance to give you more power during acceleration and you may not have boost retard any more and that could easily damage the motor under boost.

JFairman, Thanks for the idea. I'm not sure I could reach the throttle linkage as I have the stock air filter housing and inter cooler and there no room anywhere to reach by hand. You have a custom air filter?
What's your thoughts on the timing marks? I can set it close but the closer I get to the recomended timing the worse it runs. Timing is set to 1 deg ATDC at 900 RPM per the factory manual on section 10-02 for a 930-68 engine. With this setting, as before the rebuild, it was very close to the 26 deg BTDC with hose disconnected. When it's set to this timing is runs like crap. Before rebuild it ran good. Mind you this is all with the car parked and not on the road. It runs so bad ,lean and no throttle response until you get it to 4000 range of RPM where it comes to life but still lean. Fuel pressure and volume are good.
I think gsxrken was right when saying ignition timing or valve timing. I originally thought it was the loose intake manifold but that was only part of the problem.

Thanks for clearing up the vacuum hose for me I will switch them back but I know it's not the whole problem.

Yeah I remember how weak they are with stock 1987 ignition timing. Is idle timing 1 degree ATDC with both vacuum hoses connected? It's been so long since mine was stock I don't remember what the origonal stock timing was at idle.

I have a K&N air filter on the CIS air flow meter instead of the origonal air cleaner so access to everything is easy.

If the origonal red fabric colored vacuum advance hose is still on there replace it with a new hose because they dry rot and crack under the fabric covering and you can't see that it has cracked. Then it leaks vacuum and doesn't do it's job. The origonal vacuum retard line is covered with blue fabric. They don't last and if they are still there they should probably be replaced.

I've modified the centrifical advance curve in my distributor and installed an MSD 8760 boost timing retard box with MSD 6al ignition. It makes a huge improvement in low rpm torque and drivability in these cars below 3000rpm.
My timing at idle is around 12 to 15 degress btdc. Steady cruise it's around 34degress btdc and during boost it's about the same as stock, right around 26 to 28degrees btdc. I also have WMI to reduce any detonation. E10 93 octane gas quality varies alot too.

Optimum ignition timing and aftermarket air cleaners have all been covered a bunch of times in previous posts. Some searching on ignition timing, MSD ignition, and K&N or fabspeed air cleaners on this forum will probably find all the information eventually.

Something you could easily try is just leave the vacuum advance line connected to the vacuum advance pot and remove the vacuum retard line from the retard pot and plug it with a small bolt or screw or just leave it hanging for a test.
Then check the timing at idle and see if it advances and idle speed comes up. That should help drivability a bunch right there and you'll still have the same boost retard if the vacuum advance line and pot are working correctly.
Like that you'll still have centrifical advance, vacuum advance, and boost retard and some more power and better gas milage below 3000 rpms.

Check the timing though to make sure everything is still in a safe range.

The vacuum retard line and vacuum retard pot only work to retard timing somewhere around 10 degrees from idle up to around 1500 rpms and during closed throttle deceleration at any rpm. It is for lower emissions and other than that they do nothing at all.
With your current 1 degree atdc at idle you could probably get out and run faster than the car will leave from a stop. I remember what it was like...

I have replaced both vacuum lines with new. The thing is the car is'nt drivable now after the rebuild. Before it was.
Question, With all the things in the way of the bolt on the crank how do you turn the engine to check TDC to see if the rotor on the dist. is pointing in the right spot?
I still think something is amis with the timing. Remember I have the settings set to where it was before and it ran fine. After rebuild and runs like crap. When I sort this all out, if I ever do, I will install the MSD set as well. Heard very good things with that set up. Have to sort this out first though.

Push in on the fan belt (right side) and turn the motor over with the nut on the alt.
Sounds like you're maybe one tooth off on the dist.

Sounds like my experience after the rebuild. Started fine but ran terrible. I found the mechanical advance frozen. Engine had been apart for several months. A little WD40 and a drop or two of oil on the distributor shaft and all was fine.

I'm leaning that way now, especially after the comment about having to turn the dizzy all the way to the stops to get it to run even somewhat right.

BTW, I machined the adjustment slot on mine intentionally so I could crank it all the way to the stop...in order to get 12 degrees advance at idle (that's with the vacuum retard line connected...so call that 22 degrees once I get above 1500rpms and the vac retard drops off). Then the mechanical advance takes over from there.

In a "normally" timed car, i.e., 1-2 degrees ATDC idle retard, your dizzy should be somethere mid-point in it's rotation adjustment.

Back at the shop. There going to smoke the engine to test for leaks. I did check the rotor in the dist. to see if it was off but it's right on the money.

Well "mark houghton" is the winner. The frequency valve's fuse was blown. Left the shop the first time with it blown. I have never had that fuse go. My hearing isn't all that good for the small noises so I couldn't hear it if it was running anyway. Well now that I know how the car runs when it doesn't work what exactly does the little SOB do? I guess it's just as well as I have the wrench going over the engine with a fine tooth comb now after finding this and the loose manifold nuts. Hoping to have it back soon!
Thanks everyone for the help. This forum is fantastic. Thanks.

I removed all the lambda stuff from my '87 years ago. The frequency valve is controlled and driven by the k-jetronic lambda box under the driver seat and is connected to it through the lambda harness that runs back through the firewall on the left side and terminates at the multi pin plug on the rear crossmember next to the left side shock tower.

There is a rubber socket on the side of the rear relay panel for checking the pulse frequency or dwell time of the frequency valve with an oscilliscope type meter to check how it's working but I never knew there was a fuse for the frequency valve somewhere.

I'm curious, can you tell me where the frequency valve fuse is?

The frequency valve returns varying amounts of fuel from the lower differential chambers in the aluminum lambda fuel head and returns it to the gas tank through the return line.

By definition it controls another form of hydraulic control pressure that has nothing to do with the WUR and I can explain what happens as it does that if you want to know, but the end result is it changes the amount of fuel injected to make the engine run as lean as possible at all times except for during cold strart and when it's under boost so it can pass emission testing and they could sell these cars in the USA again starting from 1986 on.

Ha! I win one, finally.

Jim's our resident CIS man having cut his teeth for many years on beemers and such running CIS. Simply deleting that little freakin' valve will mess things up unless you have some major re-turning work done on the fuel head to compensate for it being gone. Not a good thing, since eventually as the years tick by those valves are going to fail all of us.

So, to that hidden fuse.....Must be one that controls all the power to the lambda computer is all I can think of.

The fuse holder in the engine compartment. The middle fuse was the problem. Blown. I forgot all about those fuses.
So the frequency valve is another emissions add on? What do you have to change to remove this PITA valve?

Beyond my knowledge. Since that freq valve controls fuel flow from the lower differential chamber back to the gas tank, for those of us running open-loop (O2 sensor disconnected) the freq valve will stay at a constant duty cycle...something like 50%...as opposed to modulating in response to the lambda computers' direction as it sees the O2 content of the exhaust gasses changing. Thus, in open loop it's fixed and never changes.
Makes one wonder if a simple flow regulator of sorts - set up to match the flow the freq valve allows when at fixed duty cycle- would suffice and take out the electrical failure potential of the freq valve?

The short version is you have to adjust six little 3mm allen head screws under the six 4mm allen head button head screws on the top of the fuel head just a little bit to increase spring pressure on the top of the flexible diaphram disc valves in the upper chambers to compensate for consistant full system pressure that will be in the lower chambers pushing upwards on the flexible diaphram after removing the frequency valve or just disconnecting the plug on it.

If those allen head spring pressure adjustment screws are not adjusted a little tighter after removing or disconnecting the frequency valve to compensate for full system pressure in the lower chambers then the diaphram with it's 6 metal discs will be pushed higher into the 6 upper chambers partially closing off the 6 small valve like orifices in the top of the upper chambers leading to the injector lines and the fuel head will inject less fuel leaning out the AFR.

Those 3mm allen head screws are the same ones used to adjust fuel flow to the injectors to balance the flow from them equally when you know you have 6 equally flowing good fuel injectors.

If I dug up a bunch of pictures I've saved to show the parts I'm talking about and tried to tell you how they work and told you how to adjust the allen head screws while doing an injector flow test into 6 plastic bottles until the fuel flow to the injectors and AFR's are where you desire I would be giving away part of what CIS Flowtech does to modify these fuel heads on a test bench to flow more fuel when running higher boost with better cams and headers.
Larry wouldn't like that.

I'll add that the reason the frequency valve can vary the amount of fuel pressure in the lower chambers up and down in relation to system pressure by returning some of that fuel to the gas tank is because the fuel feeding the lower chambers has to flow through tiny orifices leading to them from fuel that is at steady high system pressure.
Anotherwords the frequency valve that is just an inline electronic fuel injector can bleed off some of that fuel in the lower chambers and return it to the gas tank faster than it can flow through the small orifice from system pressure to replenish it.

That is the same reason the control pressure/warm up regulator everyone calls a WUR here can change hydraulic fuel control pressure pushing down on the control plunger in the middle of the fuel head while the air flow meter linkage is trying to push it up from the bottom.
The fuel feeding the control pressure chamber above the control plunger has to flow from system pressure through a tiny orifice so the CPR can easily vary that hydraulic control pressure up or down by returning some of it to the gas tank.

This is why you need two big fuel pumps to feed 930 CIS.
This crazy mechanical fuel injection system has to return fuel being used as hydraulic control pressure to the tank for it to flow and inject more fuel to the constantly flowing injectors at high fuel pressure into an intake manifold running around 15 psi higher than atmospheric pressure.

The euro fuel heads only have one hydraulic control pressure circuit returning fuel to the tank and the aluminum lambda fuel heads have two seperate hydraulic control pressure circuits returning fuel to the tank.
That is why the lambda heads run at higher system pressure than the euro heads.

Because the lambda heads have the more flexible synthetic diaphram between the upper and lower chambers they are capable of flowing alot more fuel than the euro heads after they are modified and adjusted.
They also weigh alot less and don't rust inside like the euro heads. When modified they are much better if you are after more fuel.

There are 2 easy ways to eleminate the Lambda system, swap out to a Euro fuel head or swap out to a modified USA head. I handle both and keep them in stock. The modification on the USA head eleminates the second port allowing it to function like a Euro head. As Jim stated the USA head is then capable of producing greater flow than the USA. I have never seen an engine that needed that much flow but it is available.

Car runs beter than before. Very good now but.....

While I was playing around with the timing , and other things, trying to figure out my poor performance I noticed by mistake how well the engine ran with more advance than 26 and when the boost came in it was quite a rush! but not knowing what the safe limits are I quickly set it back to stock. So I have a few questions. I know this has been asked a bunch of times and have read this in other posts but wanted to ask in my own way to make sure I get it.

Mark, You said you set the timing at idle to 12 deg. with the vacuum retard hose attached. This is with a stock distributor and vacuum pot? So once the vacuum stops above 1500 RPM you have a timing of 22 deg. because the vacuum retard in the pot releases as there is no longer any vacuum to hold the plate thus a total of 22 deg asuming there is 10 deg of retard in the pot. 12 + 10 = 22 advance. The the counter weights in the dist. take over and add how much more? for a total timing say at 4000 RPM? Must be more than 26 deg right? And you do this with out using WMI like JFairman? Just wondering as I have read other posts like this with ign running more than 26 total timing and are geting good results. I'm starting to understand all of this and want to know just how much safety is built in with a total of X deg. running 93 pump gas w 10% Alcohol I'm going to put my my t vac on the outer port and add .8 bar of pressure to see how much advance is removed with my stock set up. I know this subject has been beat to death but I need to understand what other pelicans are running and not blowing up there engines. More advance is fun!

The outer pot on the '87 distributor is vacuum advance when vacuum is applied to it and boost retard when air pressure from the turbo is applied to it. You'll see that when you hook a mighty vac to it and test it.
The inner pot is vacuum retard when vacuum is applied to it and when air pressure is applied to it nothing happens, it does nothing. You'll see that with the mighty vac test.

Mark and I have a similar timing setup with the distributor slot machined over so we can advance the distributor static timing farther to 12 -15 degrees btdc which is farther than the slot allowed origonally. I had to also remove a little aluminum from part of the housing near the fan housing area to turn the distributor that far because it was hitting something limiting the travel back there.
We both use the MSD 8762 boost timing retard box to retard timing along with the origonal boost retard working.
This way timing is around 12 to 15 degrees btdc at idle and with centrifical advance and vacuum advance working timing increases to around 35* btdc by 4000rpms.
Then when boost comes up both the inner vacuum pot and the MSD 8762 pull the timing back to around 18* btdc in response to the air pressure.

I don't have a good timing light that has the dial back funtion on it that is compatable with the multiple sparks from MSD ignition and the pulley only has 0 and 26* btdc marks on it so I have to guess or borrow a timing light with the dial back retard function to know what timing is above idle. I should file some marks into the pulley someday so I can see what timing is with my regular old timing light.

It's kinda hard to describe how all this stuff works in text with a keyboard but once you've done it and learn it all it makes sense.
The purpose is to have a little more power and drivability around town below 3000rpms.

If you were rebuilding the motor and wanted better low speed drivability it would be good to do the timing curve modifications and increase compression to around 8:1, enlarge the intake ports, and use a smaller and more efficiant turbo that comes on earlier and doesn't boost over .8 or .9 bar with SC cams and headers with a free fow muffler.
Henry at Supertech does something like that.

MSD 8762 controls the boost and you have modified the distributor ignition curve or did you just modify the slot only?

I have been looking at the MSD 6AL-2 programmable that will control the boost and the ignition curve with a locked distributor which I'm sure your familiar with.

So your running 35* BTDC @ 4000 RPM and this is only possible with WMI? If so what is the safe limit with out a WMI?

I ask all this as the wrench installed a new vacuum pot on the distributer and set timing to 26* BTDC @ 4000 RPM and the dizzy is turned almost to the end of the slot. It runs great but I think the port closest to the dist. body is adding a lot of retard because I checked the timing at idle just to see where it is and is around 2*BTDC with the retard hose plugged in. I'll check this all out tomorrow in detail and let you know where it's at. I am surprised that it's not near the middle of the slot as you mentioned a few posts back with a stock setup.

"MSD 8762 controls the boost and you have modified the distributor ignition curve or did you just modify the slot only?"

I did modify and shorten the centrifical advance curve by bending the vertical steel tabs that stop and limit the centrifical advance weight outer travel inwards about 1/8". I also ground some metal off the sides and outer edges of the centrifical advance weights to make them lighter. Then I polished them to make them pretty and finished looking while equaling their weight even though you can't see them installed. It just makes me feel good.

That has a similar effect as putting in stronger advance weight springs but none are available unless you take apart many BMW and Mercedes mechanical distributors and test the springs... The same diameter housing distributors including points and condensor units including ones that spin the other direction all use the same advance weights, but different springs.
So I made the advance weights lighter to delay the centrifical advance curve a little and then advanced the static timing to 12 to 15* btdc so final centrifical advance is the same as it was stock.

"So your running 35* BTDC @ 4000 RPM and this is only possible with WMI? If so what is the safe limit with out a WMI?"

Yes, but that is only with full vacuum advance and full centrifical advance together and only at steady low load cruise on flat level roads like the interstate in Florida.
WMI is not spraying during steady cruise on flat level roads because there is no boost happening then.
When accelerating timing will stay there until boost starts comeing on.

If you remove the vacuum advance hose during steady no load 4000 rpms then timing is at 26 to 28* btdc just like when in nuetral while you're back there with a timing light on the pulley. It sounds like you may be forgetting about full vacuum advance on top of full centrifical advance. Thats when you have around 35* btdc

Under boost there is no vacuum so there is no vacuum advance but there is always centrifical advance.
The distributors vacuum retard and the MSD 8762 both work at the same time to gradually pull timing back to around 18* btdc when boost comes on. That way vacuum retard is pulling timing back to a safe level.

I set the adjustable pressure switch for the WMI so it starts spraying at .7 bar to help reduce the chance of detonation between .7 and 1.1bar
WMI is overrated by the places that sell it but it helps especially when the mixture in the WMI tank is around 70% methanol and 30% water. It's kinda fun to experiment with it and watch the AFR gauge when it comes on and the 930 intake manifold being a flat plenum with 6 holes leading downwards to the intake ports works good for WMI distribution with little laminar flow wetout and dropout on the manifold walls unlike the Carrera manifold with all it's length and twists and turns.

If I think of it I'll take a picture of my distributor tomorrow and post it so you can get an idea how far it's turned in the lengthened slot. I have a stainless steel washer and nylock on the stud but you'll get an idea.

This timing stuff will make your head spin and keep you awake at night trying to understand it. I think Jim did a good job explaining, as well as can be done with a keyboard.

I do not have WMI and I think I'm ok without it because when on full boost all the extra timing I added at idle has all been shaved off by the MSD 8762 and by the boost retard to the vacuum pot to where I'm left in the normal timing safety zone for these cars (maybe a degree or two more, but I don't have the means to test the actual under-boost timing). WMI becomes critical when running higher boost numbers, higher timing advance, higher compression ratios, and/or crappy lower octane gas...or any combination of those.

Belive it or not with all the good posts by yourself and JFairman and all the rest of the gang I am starting to understand this and will definatly invest in a MSD setup this year.
All I was able to do was to check how much advance I have when I pull the retard side hose at idle. Timing mark 2deg BTDC with hose attached and 15-16 deg BTDC with the hose removed. So I'm getting a little more than the expected 10 advance with the hose pulled. Didn't have any help today to opperate the throttle to check the rest with the my-t-vac. Stay tuned. Car is running good though. Have to put the a V1 on the top of the list to buy soon.

Try driving it with the retard hose disconnected and plugged with a little bolt or something. The car is going to have alot more pep leaving from a stop.
Vacuum retard is gone above the transmission in nuetral 1500 rpm throttle position anyway so you won't hurt anything.
Vacuum advance will work the same and so will boost retard.

FWIW, I took a picture of my distributor slot area today to give an idea where the stud is positioned in it after lengthening the slot for more advance and all the other stuff I've done to it.
http://forums.pelicanparts.com/uploa...1366589467.jpg