1976 911 2.7 dizzy curve for 123 Tune 6
 

Hi,
Does anyone have an example curve for a stock 1976 2.7 911?

MSD 6425 AL6 if that makes any difference?

The car was dyno'd but wouldn't rev cleanly past 5800rpm.

The MSD rev limiter was set to 0,0

I plan to check the base setting of the dizzy at TDC and work from there.

Thanks!

Here's an advance curve as a function of engine RPM:

http://forums.pelicanparts.com/uploa...1618948683.jpg

Some curves are a function of distributor RPM, so be careful what you are looking at.

As it says in the picture, I set idle timing below 1000 RPM and check timing at 1500, 2000, 4000, and 6000 RPM. To get the 6000 RPM check, I just line up the timing light with one hand, and with the other hand, I quickly rev the engine and note the timing at which the advance stops advancing - I don't worry about what RPM I'm at - it's just a quick rev. No need to hold at 6000 RPM unless you really want to piss off the neighbors.

In the chump car, I installed distributorless ignition and could switch between the stock S curve above and the RS curve. They were pretty similar, it seemed like the RS curve was better with lower temps and the S curve was better when it was hotter. The engine was a 75 911 engine with early exhaust, modified zeniths (34mm chokes), and distributorless ignition.

Hi, thanks for the replies.
Is that curve too revvy for my 76 2.7? I believe it doesn't have the compression or cams to make power past 6k rpm?

i have set mine 'by feel' for my 1974 911 targa. All stock, standard 2.7 with CIS.
first set it to what the 'picture' in the service manual said, worked it all out as a mid line between the two. It drove ok, but I felt i could improve - that is the beauty of the bluetooth 1-2-3.
after a few tries I settled on
NO Vacuum advance or retard.
rpm advance
500 0.0
1200 0.0
3000 27.0
5000 27.0
6100 25.0
7400 22.0
8000 22.0
edit: forgot to say
I have set the 123 for a 5degree static advance

using a CDI+ and its internal rev limit set as per default.

Unfortunately the Dyno near me is out of action so I have to wait to do this properly.

Engine is out ATM as we found a vacuum leak in the intake system and are waiting for parts.

Is this a 123 bluetooth dizzy?
There are set up steps to the 123 line . The are great systems in my experience

Hi, it is the USB version but all my laptops are so old they barely start up now!

First you must set the dizzy to 0 @ TDC, When you do this you can be sure of the timing degrees.
Start up @8* BTDC. - 16* @ 1,800 rpm - 24* @ 2,400 rpm - 31* @ 3,000 rpm
no need for more advance unless you have dyno access , then maybe 1*-4* more 4k-5.5k all in
I hope this helps
PM me if you would like to speak on the phone , the 123 can get confusing
Ian

Hi Ian
Please see screenshot of my actual curve as set my previous owner.
http://forums.pelicanparts.com/uploa...1619204671.jpg

SBL, if this were in my shop I would run the curve that I posted .
You are leaving a lot on the table , My curve is not aggressive . Yours is week .
Ian

PS. where in the world are you . I am in NM , Usa

Hi, I am in England!
When I drove the car home last night it was running really bad misfire etc.
I started altering the curve a few degrees a time and it now doesn't start.
I returned the curve back to what was on it originally but still wouldn't start.
I dropped out plug 4 and it looks rough. It was brand new about 100 miles ago!http://forums.pelicanparts.com/uploa...1619257388.jpg

SBL, remove all plugs are they all the same ? how old are the injectors? compression test? leak down ? Plug wires? distributor cap ? rotor and dist shaft? igniter wheel? cdi box? coil? ect... MS program?
It is not the fine tuning of the timing that is causing this problem . The timing at idle should be at 5-8* not 18* that can make it hard to start , although some race cars have Idle timing at 16-18*
let me know
Ian

The electrode on that plug looks rounded at the edge , that only happens with miles . I am stumped

It was on a rolling road last week and they weren't happy with it, only made 130bhp and misfired at 5.5k rpm. I only drove it a few times and got progressing worse, lumpy tickover, misfire, etc so think it isn't entirely what I have done.
I have fitted new diz and rotor arm but still won't start.
Bit nervous setting the curve to the expected levels now, 10 degree retard at idle from previous setting is quite a jump!
Injectors, etc were new last year when the MSD and megasquirt fitted.
I reckon I will reset the stock base megasquirt map, check TDC, put in your curve and fit new plugs!

SBL, the curve I suggested is very mild and safe . The curve you have is not good.
The timing should be checked to make sure the 123 dist is matched to TDC . This is a process that i can help you with when the car is running again . Spark plugs can be defective these days , so a new set is a good idea . 10 degree jump form bad to good is, GOOD! The PO did not know about engine ignition timing . The MS injection timing is very important as well. Do you know a good MS tuner?
MS can be very hard to get right if you are not a MASTER on a 911 .

Tell me about all 6 spark plugs.... pics?
Ian

Quote from Jonny H ...All three devices are programmable for ignition curve. I would be very careful, there could be curves lurking in the Megasquirt and the MSD box

This is what I mean about getting the 123 to match TDC on the engine
VERY IMPORTANT !
Ian

In the first post, you say it would not pull cleanly past 5,800 RPM. I was going to ask if that meant it was missing, or just stopped making power. If it is missing, your advance curve would not cause this. I think Ian can help get your 123 setup working, but you may have another problem that needs to be found.

To address the point from Walter Mitty. I do agree that fine-tuning will change the horsepower number and have the engine rev higher, my point about fine-tuning the timing at this juncture was addressing the fact that the car was not running well . Fine-tuning the spark at this point will not affect the starting rough running or missing

http://forums.pelicanparts.com/uploa...1619277828.jpg


This is mine. It works really well.

So i popped all plugs out and checked the timing mark, I lined up Z1 expecting the rotor arm to point to plug 1 but it points to 2!
I tried 360 to see if it aligned with 4 but it lined up with 5.
Is my logic correct the PO may have got the timing 1 out and tried to compensate with 20deg of advance on the 123?

That seems logical and easy to nake that mistake.
Make sure #1,is at tdc on compression stroke. Then pull out the distributor, reinstall with rotor pointing to #1. Should start.
Clean around the distributor before you pull it with a magnet and rags , cover the hole when you remove it. If you don’t chances are you will drop a nut or washer into the distributor hole.

SBL, sounds like a good place to start. Once the car i idling it is important to set the 123
internal curve to 0* through 3000rpm, that way you know that you can't make a mistake setting the distributor to TDC and 0*, then put a timing light on the pulley, you must then turn the distributor to match the Z1 mark to TDC, now you know the timing is correct . 0* on the crank and 0* in the distributor . Now you can set the curve that i suggested or any other . I know my curve is a great starting point . The rotor info is very important as well.
Ian

So i set the 123 by disconnecting the plug to the MSD (the black wire connects to white MSD) and in doing so noticed both loop wires are in place! According to MSD manual one should be snipped for 6 cyl?http://forums.pelicanparts.com/uploa...1619345542.jpg

Please re read my post. You must confirm that the 123 is the ONLY device with a map.

Btw, if the MSD was set to 4 cylinders, effectively you’d be higher up the map ( at 4K you’d have the settings for 6k). If a limiter is set then this would come in early too. This may not matter if the MSD is not running a map.

That’s another reason why you have to know what devices have a map....

Hi the megasquirt is a basic fuel only with no ignition map. The MSD also doesn't have map it is triggered by the 123 using the point style connection (black wire from 123 / white wire MSD)
I have messaged the MSD helpline.
Uncut MSD loops results in 8 cylinder setting. Cut 1 loop for 6 and both for 4cyl.
Hopefully this is part of the issue!

Doubt it. Usually if there is no map the box is just firing the spark as a soon as it sees the trigger. In this ‘mode’, It doesn’t care what the RPM is. Number of cylinders is used to calculate RPM which is used for maps and rev limit.

What is your total advance measured off the timing light?

SBL, you are in good hands with Jonny H.
I'll watch from the side lines
Ian

Just thinking, Do you have the correct MSD coil?
Do you have the correct plug wires for an MSD?
Is the grounding correct for the MSD ?
in these last few posts I have the Idea that you did not set this system up and any part could have been improperly installed , am I correct? I think I would go over EVERY SINGLE STEP,
FOR FOR SET UP, FOR EACH AND EVERY PART NOT PORSCHE
just trying to get you to a fun running car
Ian

Isn't this all easily verifiable by disabling the vacuum advance and revving the engine? Set the curve to 10 degrees everywhere and make sure it doesn't move. Then adjust and test.

So I set the TDC (Z1 line up with fan housing notch and confirmed rotor arm pointing to #1) rotated body of dizzy until the green LED did it's thing, installed new diz cap and arm, new plugs but get no spark so I reinstalled old cap and arm still no spark.

The MSD box LED all indicate no fault and light on each 'fire' which is showing the 123 is at least triggering it.

I wonder if my coil is incorrect and stopped working, it should be a 1.5OHM however is a MSD blaster which is only 0.7OHM

All part of the fun!

longterm plan will be to ditch the 123 diz and MSD AL6 and look to get my Megasquirt 1 modified to work with a Ford EDIS-6 and trigger wheel.

I heard back from the MSD helpline and one of the loops should indeed be cut, whether it makes a difference I don't know but has made me check all of the previous installations.

I am currently researching the EDIS-6 which seems a reasonable option.

test spark
 

get an old spark plug
take off the coil wire that goes to the distributor and connect it to the spark plug
ground the plug from the threads to a good ground.
have someone turn the key and see if you have spark.
if you do
get a timing light
connect it to number 1
have someone turn the key and see if the light is close to the timing marks.

Thanks tried that last night, I have ordered a new coil with the correct ohm rating, wasn't expensive and would have needed doing eventually! Hopefully the old one was failing hence the misfiring that got progressively worse.

The OHM rating is very important , coils must be paired to ignition systems .
keep at it
Check everything
Ian

Thanks to every one who contributed, especially Ian and Jonnie. She now runs like a champ! Went back to basics and reset everything and stuck new coil in. Super pleased to have sorted it and learning along the way!

Actually, the resistance, "OHM rating", of the coil primary of a CDI (capacitive discharge ignition) is essentially of no concern versus an (IDI) inductive discharge ignition system.
With a CDI system, energy is just transferred to the coil, versus an IDI system where spark energy is developed based on the primary resistance and inductance.

He is running an MSD box , if the coil is not matched , the coil will burn out prematurely.

There are many nuances to high power ignition systems . Matching to OEM specs is important .
Ian

Really? Like what is high power? Provide detailed info. Just because the MSD provides multiple sparks that end at about 2500 RPM,
doesn't qualify as "high power".

Read here about "high power"; http://forums.pelicanparts.com/porsche-911-technical-forum/676385-msd-ignition-exposed.html

Here are parameters from various coils being used by Porsche owners;

http://forums.pelicanparts.com/uploa...1619938418.jpg

Found here; https://www.systemsc.com/diagnostic.htm

As can be seen from the parameters of the Bosch TCI coil (inductive discharge - 911 black/silver) and the MSD coils, they are very similar.

Sent to me from Sunburntlobster,
Hi Ian,
Yes it was mainly a knackered coil, the MSD didn't have the loop clipped for 6 cylinder and the diz needed reindexing and curve map bringing back to standard. Also the earth point was really poor which was causing intermittent issues with the MSD and Megasquirt controller!
New plugs and she is running strong and sounding great!
Thanks for all your help.

We are all happy for your success
Ian