Notices
928 Forum 1978-1995
Sponsored by:
Sponsored by: 928 Specialists

84 auto L-jet brain...anyone have one? norcal lemons UPDATE..FIXED

Thread Tools
 
Search this Thread
 
Old 11-16-2009 | 11:25 AM
  #16  
mark kibort's Avatar
mark kibort
Rennlist Member
 
Joined: Feb 2003
Posts: 29,956
Likes: 180
From: saratoga, ca
Default

Its when folks keep on trying to start it, thinking that the starter fluid will help it catch. it drys the cylinder walls out and it will sieze. 5 seconds, no, but any more than that, possibly. one thing nice about the Ljet systems, is that if it is working, the car will start, if it isnt, it wont. it may run rough if something is off like temp 2, injector issue, etc., but you dont need to coax it.
have you narrowed down the issue, or is it a damaged Ljet box?

Originally Posted by vwdmc16
yeah we firgured something is amiss. so how can I sieze the engine by fueling for 5 seconds with brake clean?
Old 11-16-2009 | 02:44 PM
  #17  
Mark Anderson's Avatar
Mark Anderson
The Parts Whisperer
Rennlist
Site Sponsor

 
Joined: Nov 2002
Posts: 7,085
Likes: 392
From: Anaheim Ca
Default

Originally Posted by Richard S
Is it the same as an 80 L-jet brain? If so, I have one or two.

Rich
The 1980 does does not have an O2 sensor output
Old 11-16-2009 | 02:58 PM
  #18  
PorKen's Avatar
PorKen
Inventor
Rennlist Member

 
Joined: Sep 2002
Posts: 10,174
Likes: 412
Default

'80 L-Jet has an oxygen sensor input.

'80-'84 L-Jet brains are interchangeable for running. '80 probably has a slightly different fuel curve. '82-'84 brains have an extra injector pulse output @ pin 11 for the fuel consumption gauge.

USA '80 had less strict emission requirements than '81-'84, and so does not have an airpump. The distributor has a different ignition curve, and the fueling may be slightly better for performance than '81-'84.
Old 11-16-2009 | 03:06 PM
  #19  
UncleMaz's Avatar
UncleMaz
Nordschleife Master
 
Joined: Aug 2005
Posts: 8,004
Likes: 20
From: So Cal
Default

Originally Posted by PorKen
'80 L-Jet has an oxygen sensor input.

'80-'84 L-Jet brains are interchangeable for running. '80 probably has a slightly different fuel curve. '82-'84 brains have an extra injector pulse output @ pin 11 for the fuel consumption gauge.

USA '80 had less strict emission requirements than '81-'84, and so does not have an airpump. The distributor has a different ignition curve, and the fueling may be slightly better for performance than '81-'84.
Thanks for that, I thought my air pump was deleted.
Old 11-16-2009 | 06:43 PM
  #20  
IcemanG17's Avatar
IcemanG17
Thread Starter
Race Director
 
Joined: Sep 2004
Posts: 16,271
Likes: 75
From: Stockton, CA
Default

Good news....IT WAS THE TEMP II......it was reading high...around 4.3k when it should be under 3k for the temp....we pulled it...engine would fire off the cold start..then die.....we "jumped" the temo II and it ran...kinda rough till it got warm...but once warm it ran like a champ....

I new one is on order....but we found a correct reading one off an Ljet volvo motor and installed it.....it reads properly and we set the ignition timing to factory spec....it was a smidge too high at 22' @ 3000rpm where spec is 20" @ 3000....at 22' degree's it was really dying past 5k...but the 20' made a nice flat power curve with our highest ever dyno # of 193.3whp....we did loose some torque but still have plenty....

The response of the engine is much improved and it just feels stronger......
Attached Images  
Old 11-16-2009 | 06:57 PM
  #21  
mark kibort's Avatar
mark kibort
Rennlist Member
 
Joined: Feb 2003
Posts: 29,956
Likes: 180
From: saratoga, ca
Default

what is with those lame curves! where is the RPM???? did you cut out at 5500rpm or something. Looks like its peaking out there and sure, it would be nice to run over the peak and down the other side for max power utilization, but running under it, only averages your power from 190 to 150, so 170 average is not bad.

Originally Posted by IcemanG17
Good news....IT WAS THE TEMP II......it was reading high...around 4.3k when it should be under 3k for the temp....we pulled it...engine would fire off the cold start..then die.....we "jumped" the temo II and it ran...kinda rough till it got warm...but once warm it ran like a champ....

I new one is on order....but we found a correct reading one off an Ljet volvo motor and installed it.....it reads properly and we set the ignition timing to factory spec....it was a smidge too high at 22' @ 3000rpm where spec is 20" @ 3000....at 22' degree's it was really dying past 5k...but the 20' made a nice flat power curve with our highest ever dyno # of 193.3whp....we did loose some torque but still have plenty....

The response of the engine is much improved and it just feels stronger......
Old 11-17-2009 | 01:50 AM
  #22  
vwdmc16's Avatar
vwdmc16
Instructor
 
Joined: Feb 2009
Posts: 141
Likes: 0
From: sacramento
Default

yeah for some reason we cant get the rpm to be printed on the paper. The software on the dyno sucks. But the run was from 2500 to 5650rpm by 5400 it really didnt want to pull much more, and there is NO reason to really hammer on this old engine just to get another hp on the screen. wouldnt it suck to throw a rod 4 days before the race, that could happen! it will be beaten plenty this weekend,


I tell you all this stress from it working and failing and deciding to work is just too much! i told you it wasnt the kill switch, which is working just fine BTW.

also finished the tranny oil cooler tonight, its a cleaned up 2nd gen RX7 oil cooler with the thermostat removed for more flow, mounted up front, it should get tons of airflow, these coolers are massively efficent. yes it will impede the radiators efficency somewhat but that wont be problem in the cool weather.

Now all that remains is a few trivial things but techncally it is ready for racing
Old 11-17-2009 | 02:10 AM
  #23  
mark kibort's Avatar
mark kibort
Rennlist Member
 
Joined: Feb 2003
Posts: 29,956
Likes: 180
From: saratoga, ca
Default

cut a big hole where mine was in the hood. it will be good for some decent downforce up front, even without a splitter.

Yes, I get that it was not the kill switch. It just you were doing things last min an blazing new trails where things can go wrong. There is just a lot of knowledge here to set up things like that , along with comments of the drawbacks of things that could go wrong, or things to look out for. thats all.

looks like you got it all together. Told you it was probably the Temp IIl BTW!

mk
Originally Posted by vwdmc16
yeah for some reason we cant get the rpm to be printed on the paper. The software on the dyno sucks. But the run was from 2500 to 5650rpm by 5400 it really didnt want to pull much more, and there is NO reason to really hammer on this old engine just to get another hp on the screen. wouldnt it suck to throw a rod 4 days before the race, that could happen! it will be beaten plenty this weekend,


I tell you all this stress from it working and failing and deciding to work is just too much! i told you it wasnt the kill switch, which is working just fine BTW.

also finished the tranny oil cooler tonight, its a cleaned up 2nd gen RX7 oil cooler with the thermostat removed for more flow, mounted up front, it should get tons of airflow, these coolers are massively efficent. yes it will impede the radiators efficency somewhat but that wont be problem in the cool weather.

Now all that remains is a few trivial things but techncally it is ready for racing
Old 11-17-2009 | 02:12 AM
  #24  
Andre Hedrick's Avatar
Andre Hedrick
Rest in Peace
Rennlist Member
 
Joined: Sep 2006
Posts: 5,384
Likes: 1
From: Concord, CA
Default

I have a factory new one in the box.
Old 11-17-2009 | 02:18 AM
  #25  
IcemanG17's Avatar
IcemanG17
Thread Starter
Race Director
 
Joined: Sep 2004
Posts: 16,271
Likes: 75
From: Stockton, CA
Default

Originally Posted by Andre Hedrick
I have a factory new one in the box.
Andre
That is good to know.....luckily for us the one in the "estate" works fine...PM sent



Quick Reply: 84 auto L-jet brain...anyone have one? norcal lemons UPDATE..FIXED



All times are GMT -3. The time now is 01:46 AM.