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Help. I need an inside picture of an ECU D-Jetronic Computer 3CU

XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Help. I need an inside picture of an ECU D-Jetronic Computer 3CU

 
  #21  
Old 05-14-2019, 11:41 AM
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Originally Posted by warrjon View Post
Stock lift is 0.374" or is that a typo
That is correct. I had them do a .419 lift with the same duration. Also, with a wider lobe separation.
If I did it again. I would have kept the stock duration, but, increased the lift to about .430. Close lash adjustment would be in order to prevent noise.
As for my cam, it is very good for everything. It's not too temperamental. But, power starts to fall off around 5700 rpm on a loaded dyno. Not the 6000 they advertised. Yet, this is with my increased lobe separation I asked for... And I have no idea what the lobe lift is at .050 lift. Some cams ramp up quicker, therefore, more aggressive. Mine is quite tame. I would have gone more aggressive, but, my piston compression is 9:1, so I would not burn the fuel properly if I went with a more aggressive cam.

My vacuum is ok. But I have no means of measuring it.
 

Last edited by virtue; 05-14-2019 at 11:43 AM.
  #22  
Old 05-15-2019, 08:48 AM
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Originally Posted by virtue View Post

My vacuum is ok. But I have no means of measuring it.
When tuning this project you need to know what the vacuum profile is. This is super important at idle, light and part throttle.
Get a vacuum gauge. The MPS influences the fueling considerably. See if adding a few degrees of timing provides a better a vacuum profile at part throttle and thus more accurate fueling.

Do you still have a single coil and stock ignition module, if so you're luck it even make it over 5000 RPM. Consider an crane ignition module and a modern high capacity coil. A v12 going at 6000RPM is like a V8 going at 9000 RPM.. That's a lot to ask of a coil.
 
  #23  
Old 05-15-2019, 03:49 PM
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I know Norm used single Marelli coils on the race cars which were good for 7500rpm
 
  #24  
Old 05-15-2019, 05:00 PM
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i use the Crane X700 computer , had original from 1994, a Advance auto standard hi-output coil! 1978 Pre He , V12, tried the Crane X3000 module,(ran like crap), burnt up the coil, NOT compatible with 12 cylinders, V8 or less only!

my engine will rev past 6500rpm no problem(but not pulling tho). shifts best at 5700/6000rpm! Crane RACE cams, .410lift, new springs from Grp44 racing,shimmed .060 thou. Grp 44 oversize valves single piece forged Stainless steel. 9.2 compression pistons, low drag Moly rings! the usual port/polish modded ports!,, almost forgot, inlet manifolds and plenums completely EXTRUDE HONED, no humps and injector bumps! OS TBS.

i also use a stanalone fuel system SDSEFI.com,, had it since 1994, but as they advanced in technology, they upgraded at NO charge, 1998!
again company owner emailed,around 2006, they were changing there basic systems, and sent back and completely new board(same box and plugs), No charge, just shipping Calgary!

i do like it ,but in beginning a lot of tuning/retuning/and retuning!! learning curve is an UNDERSTATEMENT,, OH Yeah!!
but now i'm pretty sure i got it covered,(i think),LOL. for me i could not be without the mixture control,Lean/rich, and AFR gage!
of course trans and rear gear mods, usual stuff!

probably forgot some stuff,, 26yrs ago build, if i were to do it over , it would be TWIN TURBO, E85/or methanol!
ron





 
  #25  
Old 05-16-2019, 07:42 PM
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Originally Posted by icsamerica View Post
When tuning this project you need to know what the vacuum profile is. This is super important at idle, light and part throttle.
Get a vacuum gauge. The MPS influences the fueling considerably. See if adding a few degrees of timing provides a better a vacuum profile at part throttle and thus more accurate fueling.

Do you still have a single coil and stock ignition module, if so you're luck it even make it over 5000 RPM. Consider an crane ignition module and a modern high capacity coil. A v12 going at 6000RPM is like a V8 going at 9000 RPM.. That's a lot to ask of a coil.
I have upgraded my single coil ignition. I have a Crane xr700, going through a MSD box, with a dry race coil. Yes, I agree, a single coil can't do 6000 rpms. My car on the dyno started to cough out around 4800 rpms with the Crane and MSD box. The MSD liquid coil could not energize and spark fast enough. So, I had to put a race coil in. Fixed the problem. So spark is good.
I still have not gotten a vacuum guage...
 
  #26  
Old 05-16-2019, 07:46 PM
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Originally Posted by warrjon View Post
I know Norm used single Marelli coils on the race cars which were good for 7500rpm
Two single coils are good. But, one single coil is no good. I experienced this on the dyno. Infact they had to increase the sensitivity of their pick up wire to max, just to get a reading at higher rpms. The spark fizzled out.
 
  #27  
Old 05-18-2019, 02:57 PM
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the original V12s had only one coil with Lucas stuff, and most would rev at least 6500rpms?

just maybe something else going on?
 
  #28  
Old 05-18-2019, 05:45 PM
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No, the cars had 2 coils until the mid 80's. Then the low resistance Ducallier coil came in and was able to charge fast enough to use a single coil. If you use a single coil with a primary resistance under 0.5 ohm it should work fine. In contrast, an older coil for points ignition is about 3 ohms.
 
  #29  
Old 05-18-2019, 05:55 PM
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Originally Posted by Jagboi64 View Post
No, the cars had 2 coils until the mid 80's. Then the low resistance Ducallier coil came in and was able to charge fast enough to use a single coil. If you use a single coil with a primary resistance under 0.5 ohm it should work fine. In contrast, an older coil for points ignition is about 3 ohms.
l

look at my 1st pic , shows a single coil standard Advance auto high output coil, and in the dizzy i use the Crane XR700 optical sensor setup! with my preference for advance curve simple weight/spring setup!

coil cost in 1994 $28. bucks still ok!
ron
 
  #30  
Old 05-18-2019, 05:58 PM
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i dont think i ever seen a Jag V12 with POINTS??.
 
  #31  
Old 05-21-2019, 08:31 PM
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Originally Posted by icsamerica View Post
When tuning this project you need to know what the vacuum profile is. This is super important at idle, light and part throttle.
Get a vacuum gauge. The MPS influences the fueling considerably. See if adding a few degrees of timing provides a better a vacuum profile at part throttle and thus more accurate fueling.

Do you still have a single coil and stock ignition module, if so you're luck it even make it over 5000 RPM. Consider an crane ignition module and a modern high capacity coil. A v12 going at 6000RPM is like a V8 going at 9000 RPM.. That's a lot to ask of a coil.
I finally bought a vacuum tester. My car is floats around 18 - 21 Hg. Better than nothing I guess...
 
  #32  
Old 05-21-2019, 10:30 PM
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Originally Posted by virtue View Post
I finally bought a vacuum tester. My car is floats around 18 - 21 Hg. Better than nothing I guess...
That's at idle? I see you're in Calgary too, that's not bad for our elevation. As a comparison, I had a 1995 VDP and it generated 16" Hg at idle.
 
 
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