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Reference Material on Programmable Ignition
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flosho  



Joined: 01 Jul 2004
Posts: 3158
Location: Eau Claire, Wisconsin

PostPosted: Mon Sep 03, 2012 12:20 pm    Post subject: Reply with quote

ideola wrote:

OK, great, if you have a baseline map to start with...but adding in a programmable ignition to a car that never had one? How do you build such a map without a dyno???? How do you know where to even begin???



You build one from scratch, like I did.. or copy one from a similar 2 liter style motor.

I used a map from an srt4.
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Tue Sep 04, 2012 1:58 am    Post subject: Reply with quote

flosho wrote:
ideola wrote:

OK, great, if you have a baseline map to start with...but adding in a programmable ignition to a car that never had one? How do you build such a map without a dyno???? How do you know where to even begin???



You build one from scratch, like I did.. or copy one from a similar 2 liter style motor.

I used a map from an srt4.


I like the idea of starting with the OEM curve as the basis for a map, so I may attempt to convert each of those into a 12x12 grid. In the meantime, would you mind posting your ignition maps? I'm really curious particularly in the turbo maps...most of the others posted here have been for NAs (and they're missing images anyway).
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gegge  



Joined: 27 Jul 2007
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PostPosted: Wed Sep 05, 2012 3:26 am    Post subject: Reply with quote

Ideola: Compare your DITC diagram with this one and you got your X-axle


The number "2" is equal to idle and if IIRC that is some 9 BTDC @ 950 rpm. Every new vertical line equals another 500rpm
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flosho  



Joined: 01 Jul 2004
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Location: Eau Claire, Wisconsin

PostPosted: Wed Sep 05, 2012 7:04 am    Post subject: Reply with quote

So I tried to post my ignition map but my backup laptop kept crashing on me and then I gave up.

I'll try again tonight.
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flosho  



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PostPosted: Wed Sep 05, 2012 2:09 pm    Post subject: Reply with quote


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Raceboy  



Joined: 01 Mar 2004
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Location: Estonia, Europe

PostPosted: Thu Sep 13, 2012 10:19 pm    Post subject: Reply with quote

Ignition is the most complicate aspect of engine tuning and to get the best results(=which makes most power without ruining the engine) is to use spark plugs with cylinder pressure transducers (=very expensive, but available on engine dynos), ION sense (not readily available), det cans (cheap and effective but require some experience) etc.

There are some aspects that would negate the definite need for dyno. For example if one's engine is detonation limited not MBT limited and tuners experience is great enough to tune given engine.

Stock 931 is MBT limited and anything in the region of stock boost levels results in overly advanced engine if one is using premium gas (which it should). If you go over 1 bar then it becomes det limited but that won't happen until 1.5 bars or so.

Even though most tuners (who do this for living) say that you can't tune the ignition at all without a dyno or something (to justify their big fees), there are certain general rules that apply regarding various engine types, CR's, induction types (turbo, nitro, supercharger) etc that allow an experience tuner to tune the engine to 95% of it's potential just making a an advance table without driving at all.
For example, I have tuned ~20 turbocharged BMW's (with M20 and M30 engines) both on dyno and on open roads and I know the required advance by heart on various engine loads/rpm.
The amount of advance engine requires depends on how quick the burn is and that depends on many-many things: placement of the plug (most important), bore size, fuel atomization, turbocharging etc.

If anyone wants, I can post an advance map from my turbocharged 924 NA (9.3:1 CR, 1 bar of boost, 250+ hp on regular 98 oct gas). This engine has lived with it for 5 years and seen track days, drag events etc. No engine failures.
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ideola  



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PostPosted: Thu Sep 13, 2012 11:36 pm    Post subject: Reply with quote

Raceboy, that is good info, and I would absolutely love to see the advance map if you wouldn't mind sharing it.

My current plan is to buy a MegaJolt system. Based on what I've looked at so far, it seems to be the best bang for the buck, and since I now have the trigger wheel solution figured out, it should be an easy near bolt-on solution. I realize MegaSquirt gives me more options (i.e. MegaJolt is limited to EDIS only, as far as I can tell from reading their docs, no COP, CNP, etc.). But MS introduces a level of cost and complexity that is unnecessary for what I have in mind. The MegaJolt setup is less than $350 all in, while a recurved distributor is at least $200. I looked closely at the "programmable" MSD systems, but they only allow retard off of a full-advance curve, which is too limited for what I am hoping to achieve (not to mention they are pricey for what they do).

Seeing the stock 931 advance curves, I am convinced that they are highly conservative, and that much more power could be wrung from the motor even with stock CIS by running a more aggressive timing curve. I am no where near running out of fuel, even at 15 psi of boost, so I am content to run my rebuilt fuel dizzy and stock CIS on that car. If I "outgrow" MegaJolt and eventually want to do the MegaSquirt full EFI conversion, I will then have a well-defined ignition advance sorted out for the turbo, and I can move the MegaJolt system over to the D-Prod tribute car, which will never have fuel injection since I am converting it to carbs.
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WEASEL149  



Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield

PostPosted: Fri Sep 14, 2012 12:55 am    Post subject: Reply with quote

+1 Raceboy, I'd also love to see your advance curves, maybe for the Gulf car too?

I've seen the list of cars you've tuned over on the VEMS sites and it's clear that you know what you're doing - impressive list.

ideola wrote:
Seeing the stock 931 advance curves, I am convinced that they are highly conservative, and that much more power could be wrung from the motor even with stock CIS by running a more aggressive timing curve. I am no where near running out of fuel, even at 15 psi of boost, so I am content to run my rebuilt fuel dizzy and stock CIS on that car. If I "outgrow" MegaJolt and eventually want to do the MegaSquirt full EFI conversion, I will then have a well-defined ignition advance sorted out for the turbo, and I can move the MegaJolt system over to the D-Prod tribute car, which will never have fuel injection since I am converting it to carbs.


I think your plan is wise. It's something I considered doing before my engine needed work.
Not only are the stock advance curves very conservative but when you throw charge-cooling into the mix too then the timing can be pushed even more.
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Raceboy  



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PostPosted: Fri Sep 14, 2012 3:34 am    Post subject: Reply with quote

Here's the advance tables.

This from the turbocharged euro 924:


And this from Gulf:


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'67 911 Irish Green hotrod, 2.4S
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'78 924
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'82 924S/931 "Gulf" racecar, 330 hp, sold
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Last edited by Raceboy on Mon Sep 17, 2012 8:51 pm; edited 1 time in total
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Scorpio  



Joined: 05 Jul 2007
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PostPosted: Mon Sep 17, 2012 8:47 pm    Post subject: Reply with quote

^ Raceboys graph sharing makes me happy
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gegge  



Joined: 27 Jul 2007
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PostPosted: Tue Sep 18, 2012 1:16 am    Post subject: Reply with quote

Thanks Raceboy! Much appreciated info.
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Scorpio  



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PostPosted: Wed Mar 04, 2015 8:34 pm    Post subject: Reply with quote

Raceboy wrote:
Here's the advance tables.

This from the turbocharged euro 924:


And this from Gulf:



hey raceboy was this your final ignition table? was it conservative..?
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leadfoot  



Joined: 11 Dec 2002
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PostPosted: Mon Mar 09, 2015 7:52 pm    Post subject: Reply with quote

Scorpio wrote:
Raceboy wrote:
Here's the advance tables.

This from the turbocharged euro 924:

wolf map

And this from Gulf:



found and inserted one of my old ignition maps between Raceboys from the sc engine (not sure which one though), a few more load cells changed across the board to get things nicer for cruise and decel... note the difference in the way my ecu is configured is by load/map sensor and referenced as 0 to 107 load not kpa... they are fairly similar in timing though, if you watch a live tune it will generally go pretty quickly straight up to max load under WOT and travel across the load cells via rpm, on the way back they tend to cut almost diagonally across the cells in a "logarithmic" pattern,
so yeah by using similar maps could get you going, remember your engine will be completely different and dependent on your fuel map too...
Stu
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Fasteddie313  



Joined: 29 Sep 2013
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Location: MI

PostPosted: Fri Jul 13, 2018 8:50 am    Post subject: Reply with quote

ideola wrote:


1979-1980 931 Centrifugal Advance Curve


1979-1980 931 Vacuum Advance Curve



I want to get a good understanding of my 931 S1 ignition map so I know what I'm working with.. Lets see if I can understand these curves..

So, if I set my timing to 20BTDC at 2k rpms, that will put me right on the 0 zero line on those curves..

I think it's going to be something like..
Base timing (20BTDC) + centrifugal variable by RPM + vacuum variable by MAP = actual timing

So at 1000RPM (distributor half speed) and idle vacuum my timing will be
-20 base + -1 centrifugal + -6.5 vacuum = total 27.5btdc .. I think..

2000 on boost
-20 + 0 + 9 = 11btdc

3000 on boost
-20 + .5 + 9 = 10.5BTDC

4000RPM on boost..
-20 base + -1 centrifugal + + 9 vac = 12BTDC on boost..

6000RPM on boost
-20 + .5 + 9 = 10.5BTDC

So on boost from 2-6k timing should go 11-10.5-12-10.5

If my math is right..


Compared to everyone elses tuned maps in this thread, they are all running about 10 dbtdc MORE advance than the OEM 931 setup, so my 931 timing is very conservative and very safe, being a whole 10 degrees more retarded..

Is my math right on this?
I'm not sure if I understand those Porsche maps and how to put them all together..

Raceboy wrote:

And this from Gulf:



The gulf is a 931 engine like mine but very modified.. I don't recall the CR or piston design (flat tops?).. Huge turbo..

Raceboy (or others), do you think I could just borrow that map, take maybe about 5 degrees out of it on boost for safety?

Raceboy wrote:

Stock 931 is MBT limited and anything in the region of stock boost levels results in overly advanced engine if one is using premium gas (which it should). If you go over 1 bar then it becomes det limited but that won't happen until 1.5 bars or so.


So use that map exactly up to 165 and pull back the 200 and 250 columns a bit?

Hmmm..
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