|
924Board.org Discussion Forum of 924.org
|
View previous topic :: View next topic |
Author |
Message |
flosho
Joined: 01 Jul 2004 Posts: 3155 Location: Eau Claire, Wisconsin
|
Posted: Mon Sep 03, 2012 11:20 am Post subject: |
|
|
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. _________________ [This Space For Rent] |
|
Back to top |
|
|
ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
|
Posted: Tue Sep 04, 2012 12:58 am Post subject: |
|
|
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). _________________ erstwhile owner of just about every 924 variant ever made |
|
Back to top |
|
|
gegge
Joined: 27 Jul 2007 Posts: 1124 Location: Sweden
|
Posted: Wed Sep 05, 2012 2:26 am Post subject: |
|
|
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 _________________ Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
|
Back to top |
|
|
flosho
Joined: 01 Jul 2004 Posts: 3155 Location: Eau Claire, Wisconsin
|
Posted: Wed Sep 05, 2012 6:04 am Post subject: |
|
|
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. _________________ [This Space For Rent] |
|
Back to top |
|
|
flosho
Joined: 01 Jul 2004 Posts: 3155 Location: Eau Claire, Wisconsin
|
Posted: Wed Sep 05, 2012 1:09 pm Post subject: |
|
|
_________________ [This Space For Rent] |
|
Back to top |
|
|
Raceboy
Joined: 01 Mar 2004 Posts: 2326 Location: Estonia, Europe
|
Posted: Thu Sep 13, 2012 9:19 pm Post subject: |
|
|
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. _________________ '83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche |
|
Back to top |
|
|
ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
|
Posted: Thu Sep 13, 2012 10:36 pm Post subject: |
|
|
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. _________________ erstwhile owner of just about every 924 variant ever made |
|
Back to top |
|
|
WEASEL149
Joined: 19 Aug 2005 Posts: 595 Location: UK, Sheffield
|
Posted: Thu Sep 13, 2012 11:55 pm Post subject: |
|
|
+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. _________________ 1979 UK 932 |
|
Back to top |
|
|
Raceboy
Joined: 01 Mar 2004 Posts: 2326 Location: Estonia, Europe
|
Posted: Fri Sep 14, 2012 2:34 am Post subject: |
|
|
Here's the advance tables.
This from the turbocharged euro 924:
And this from Gulf:
_________________ '83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche
Last edited by Raceboy on Mon Sep 17, 2012 7:51 pm; edited 1 time in total |
|
Back to top |
|
|
Scorpio
Joined: 05 Jul 2007 Posts: 1957 Location: Brisbane, Australia
|
Posted: Mon Sep 17, 2012 7:47 pm Post subject: |
|
|
^ Raceboys graph sharing makes me happy _________________ 1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT
Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!! |
|
Back to top |
|
|
gegge
Joined: 27 Jul 2007 Posts: 1124 Location: Sweden
|
Posted: Tue Sep 18, 2012 12:16 am Post subject: |
|
|
Thanks Raceboy! Much appreciated info. _________________ Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
|
Back to top |
|
|
Scorpio
Joined: 05 Jul 2007 Posts: 1957 Location: Brisbane, Australia
|
Posted: Wed Mar 04, 2015 7:34 pm Post subject: |
|
|
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..? _________________ 1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT
Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!! |
|
Back to top |
|
|
leadfoot
Joined: 11 Dec 2002 Posts: 2222 Location: gOLD cOAST Australia
|
Posted: Mon Mar 09, 2015 6:52 pm Post subject: |
|
|
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 _________________ 1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
|
Back to top |
|
|
Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
|
Posted: Fri Jul 13, 2018 7:50 am Post subject: |
|
|
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.. _________________ 80 Turbo - Slightly Modified |
|
Back to top |
|
|
Fasteddie313
Joined: 29 Sep 2013 Posts: 2596 Location: MI
|
Posted: Sat Jul 27, 2019 6:22 am Post subject: |
|
|
This is what I get after plotting the stock 931 advance curve to a map..
Does it look right as far as a copy of what those curves do?
And some 3D views..
Viewed from the top down so you can see the curves..
From the low RPM side you can see the advance fall off to the left as intake pressure rises..
Ah but you know what I forgot the darn thing has that ported vacuum tap on the TB so at idle you would lose all of the vacuum advance..
So wherever you are at idle you are going to lose about 6 degrees of advance.
Or in other words, when the throttle is closed in vacuum the timing retards about 6 degrees for idle..
Should idle around 21.25 btdc @ 1kRPM or 21.75 @ 750RPM..
#s aren't exact because of the margin for error on the Porsche curves, I tried to pick decent numbers in the middle of the zones.. _________________ 80 Turbo - Slightly Modified |
|
Back to top |
|
|
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|