L jetronic for performance

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BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

L jetronic for performance

Post by BEEK »

i would like peoples opinions on putting a l jetronic system on a performance motor. the intened specs are:
10.4-1 compression 2.0l
42-82 cams
big valves, ported and polished head
lancia beta intake with a 60 cfl throttle body

will probably have to replace the afm with a maf

or just use a pair of 42 dcnf's?
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
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divace73
Posts: 1380
Joined: Sun Oct 17, 2010 5:59 am
Your car is a: 1980 Fiat 124 Spider Silver
Location: Sydney, Australia

Re: L jetronic for performance

Post by divace73 »

if you are going down the FI performance path, I'd do (am doing I should say, but is a looong process for me) Mesgasquirt, you can use the exisiting harness for the most bits and it is fully programable, you also have the choice of spark control, with little upgrade

like you mention the standard AFM will choke your engine, I don't know if there is a MAF that is swappable??

I though the dcnf's were for a E/W configuration?? May have to look up the carbie codes...I know the 44 IDF's are standard upgrade.

The twin carb set up may be the 'easier' thing do to, but may want the get them set up and tuned for your specs.
Cheers David
-=1980 silver Fiat 124 Spider=-
If you want to see pics of my car (and other random stuff) >>click here<< OR
see my >>You tube channel<<
BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: L jetronic for performance

Post by BEEK »

yes this engine is for a scorpion. i realy dont want to learn how to build and program a megasquirt. i do have the lancia ecu, i know how to turn up the fuel on a jetronic, and think a maf converter will be able to work. its all about resistance
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
User avatar
divace73
Posts: 1380
Joined: Sun Oct 17, 2010 5:59 am
Your car is a: 1980 Fiat 124 Spider Silver
Location: Sydney, Australia

Re: L jetronic for performance

Post by divace73 »

BEEK wrote:yes this engine is for a scorpion. i realy dont want to learn how to build and program a megasquirt. i do have the lancia ecu, i know how to turn up the fuel on a jetronic, and think a maf converter will be able to work. its all about resistance
You can buy MS built (which is What I did for ease), and there are base maps available but you will need to fine tune for performance on a dyno (I guess like on any engine whether carbs of FI??)

If you can get a MAF to match the resistance of the AFM, it may be worth a try. I have played around with Fuel pressures a little and found when I did increase the pressure, it did make top end better but would bog down at the low end when I floored it.
I have actually thought about relocating the afm sweep with the TPS and have an open inlet??

I reckon if you can do both, Do the FI first and if the performance isn't up to expectation try the carbs.

The carbs will sound better. ork ork....
Cheers David
-=1980 silver Fiat 124 Spider=-
If you want to see pics of my car (and other random stuff) >>click here<< OR
see my >>You tube channel<<
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ga.spyder
Posts: 3478
Joined: Tue Nov 06, 2007 7:19 pm
Your car is a: 1982 Spider 2000
Location: Blairsville ,Ga.

Re: L jetronic for performance

Post by ga.spyder »

Very interesting post,Beek.Keep us informed on what you do.I would love to see our Lemons race car with fuel injection.After 3 races we still cant get the carbs tuned correctly.It is very frustrating to have to baby the throttle coming out of slow turns,as people you just outbraked and passed,go back around you!
Craig Nelson

1982 Spider 2000...pride and joy
1981 Fiat X1/9..gone but not forgotten
1976 124 Spider..the self-healer
2001 BMW 328ci daily driver and track car
Fling It Around Turns !
So Cal Mark

Re: L jetronic for performance

Post by So Cal Mark »

it's not difficult to use a larger afm if you're looking for more top end. The big issue is with the L-jet and those cams you listed. The L-Jet doesn't like much overlap at lower rpms. You'll find it's difficult to get the fuel mixture right all through the rpm range
BEEK
Posts: 1833
Joined: Wed Mar 24, 2010 10:45 pm
Your car is a: 1975 Spider
Location: clermont fl

Re: L jetronic for performance

Post by BEEK »

is the overlap issue the afm door?
Automotive Service Technology Instructor (34 year Fiat mechanic)
75 spider
, 6 Lancia Scorpions, 2018 Abarth Spider, 500X wifes, 500L 3 82 Zagatos. 82 spider 34k original miles, 83 pininfarina, 8 fiat spider parts cars
son has 78 spider
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