K-Jet vs. L-Jet
08-01-2006, 09:22 AM
#1
Burning Brakes
Thread Starter
K-Jet vs. L-Jet
Can someone please explain the difference between K-Jet and L-Jet? Is it simply improved technology for newer (relatively speaking) year models? Thanks.
08-01-2006, 10:01 AM
#2
Gluteus Maximus
Rennlist Member
Rennlist Member
Join Date: Nov 2004
Posts: 6,365
Likes: 0
Received 0 Likes
on
0 Posts
They're very different.
K-Jet = Continuous Injection System (CIS). The fuel is injected in a continuous stream. The volume flow rate is regulated to engine demand thru largely mechanical means.
L-Jet = Electronic Fule Injection (EFI). Pulses of fuel are injected. The duration and frequency of the pulses are controlled entirely electronicly.
K-Jet = Continuous Injection System (CIS). The fuel is injected in a continuous stream. The volume flow rate is regulated to engine demand thru largely mechanical means.
L-Jet = Electronic Fule Injection (EFI). Pulses of fuel are injected. The duration and frequency of the pulses are controlled entirely electronicly.
08-01-2006, 10:14 AM
#3
Official Rennlist
Borat Impersonator
Rennlist Member
Borat Impersonator
Rennlist Member
It is a completely different type of fuel injection system. There are some who would argue wether L-Jet is an improvement on K-Jet, I have heard that K-Jet systems breathe much better. The major difference is that k-jet is a mechanical fuel injection and l-jet is electronic. In a k-jet car the air is measured by a circular plate that directly controls the plunger in the fuel distributor. The fuel distributor does exactly what its called. distributes the fuel to the injectors via individual fuel rails. The injectors are pressure controlled and the more fuel pressure, the more they open. The downfall of k-jet is that it is very difficult to troubleshoot and tune for someone lacking a thorough understanding of the system and expensive set of guages. BUT, once the system is working correctly, it is very realiable. Another negative of k-jet is if the car sits for long periods of time, the system can go bad, starting with the fuel distributor.
The l-jet meters air with a swinging square "barn door" plate. That information is relayed to the injection brain, which controls the electronic fuel injectors. The fuel pressure is vaccuum controlled I believe through fuel pressure dampners on the fuel rails. I do not know what the common fail points of l-jet systems are, I have heard of gummed up fuel injectors and the brain going bad, but not much is heard of l-jet issues 'round here. I read a lot more about the lh-jet problems. lh-jet is an improvement on l-jet, where l-jet is a whole new techonology compared to k-jet.
The l-jet meters air with a swinging square "barn door" plate. That information is relayed to the injection brain, which controls the electronic fuel injectors. The fuel pressure is vaccuum controlled I believe through fuel pressure dampners on the fuel rails. I do not know what the common fail points of l-jet systems are, I have heard of gummed up fuel injectors and the brain going bad, but not much is heard of l-jet issues 'round here. I read a lot more about the lh-jet problems. lh-jet is an improvement on l-jet, where l-jet is a whole new techonology compared to k-jet.
08-01-2006, 11:11 AM
#4
Burning Brakes
Thread Starter
Thanks, Borys.
Can you tell me what years had either system and what parts, if any are interchangeable? I'm assuming since the K is mechanical and L is electronic the injectors and fuel rails are significantly different, is that correct? Thanks.
David
Can you tell me what years had either system and what parts, if any are interchangeable? I'm assuming since the K is mechanical and L is electronic the injectors and fuel rails are significantly different, is that correct? Thanks.
David
08-01-2006, 11:23 AM
#5
Hi Dave,
The K-Jet was on 77-79 cars.
L-Jet was on 81-84 cars
Injectors and fuel rails are different. Your car had the barn Air Flow Meter (AFM(Barn Door)) replaced as well as the injectors rebuilt and flow balanced.
You looking to retrofit the K-Jet to your car?
BTW, you are scoring points with my wife for taking good care of "her baby".
The K-Jet was on 77-79 cars.
L-Jet was on 81-84 cars
Injectors and fuel rails are different. Your car had the barn Air Flow Meter (AFM(Barn Door)) replaced as well as the injectors rebuilt and flow balanced.
You looking to retrofit the K-Jet to your car?
BTW, you are scoring points with my wife for taking good care of "her baby".
08-01-2006, 11:48 AM
#6
Burning Brakes
Thread Starter
Originally Posted by Scott C
Hi Dave,
The K-Jet was on 77-79 cars.
L-Jet was on 81-84 cars
Injectors and fuel rails are different. Your car had the barn Air Flow Meter (AFM(Barn Door)) replaced as well as the injectors rebuilt and flow balanced.
You looking to retrofit the K-Jet to your car?
BTW, you are scoring points with my wife for taking good care of "her baby".
The K-Jet was on 77-79 cars.
L-Jet was on 81-84 cars
Injectors and fuel rails are different. Your car had the barn Air Flow Meter (AFM(Barn Door)) replaced as well as the injectors rebuilt and flow balanced.
You looking to retrofit the K-Jet to your car?
BTW, you are scoring points with my wife for taking good care of "her baby".
and not really looking to retro-fit, I just found a K-Jet car that may be no more than an organ donor (or a track car 
, boss' permission, of course) and trying to figure out what would be usable; engine OK, body and interior very rough. Not to mention he wants waaaaaaaaayyyyyy too much; I can wait... It may be more of a project than I would have time for. Hell, I was just excited to see another 928 in town!Tell your wife you should've bought stock in Meguiar's; her, uh, my baby is kept very clean...
Trending Topics
08-01-2006, 01:11 PM
#8
Official Rennlist
Borat Impersonator
Rennlist Member
Borat Impersonator
Rennlist Member
what they said about the years. As far as intake, the whole thing is different between k-jet and l-jet. Maybe the plenum and or throttle body is interchangeable, but everything else is different.
08-01-2006, 05:21 PM
#9
Nordschleife Master
Join Date: Sep 2004
Location: Not close enough to VIR.
Posts: 9,429
Likes: 0
Received 2 Likes
on
2 Posts
Originally Posted by Scott C
Hi Dave,
The K-Jet was on 77-79 cars.
L-Jet was on 81-84 cars
Injectors and fuel rails are different. Your car had the barn Air Flow Meter (AFM(Barn Door)) replaced as well as the injectors rebuilt and flow balanced.
The K-Jet was on 77-79 cars.
L-Jet was on 81-84 cars
Injectors and fuel rails are different. Your car had the barn Air Flow Meter (AFM(Barn Door)) replaced as well as the injectors rebuilt and flow balanced.
77-83 Euro K-Jet
78-79 US K-jet
80-84 US L-jet
84+ Euro LH-jet
85+ US LH-jet
08-01-2006, 06:48 PM
#10
Rennlist Member
Like they said, K-Jet does not like to be left standing. My 83 Euro improved a lot with regular use and cleaned injectors. Gauges are not expensive - $59 is all mine cost. Manual from Amazon $15. I am continually surprised at how well this system handles cold starts , and its cold driveability is surperb.
jp 83 Euro S AT 50k
jp 83 Euro S AT 50k
08-01-2006, 10:02 PM
#11
Agreed. The K-jet or its derivatives were used by MB up through 95. My first Porsche had the CIS system and was still in top shape when I sold it with 300K miles. As mentioned earlier, the CIS system can get clogged when allowed to sit for long periods with old fuel. i.e. if you got it, drive it.
Dennis
Dennis
08-01-2006, 11:41 PM
#12
Originally Posted by 1981 Shark
No problems at present and not really looking to retro-fit, I just found a K-Jet car that may be no more than an organ donor (or a track car , boss' permission, of course) and trying to figure out what would be usable; engine OK, body and interior very rough. Not to mention he wants waaaaaaaaayyyyyy too much; I can wait... It may be more of a project than I would have time for. Hell, I was just excited to see another 928 in town!
Tell your wife you should've bought stock in Meguiar's; her, uh, my baby is kept very clean...
and not really looking to retro-fit, I just found a K-Jet car that may be no more than an organ donor (or a track car , boss' permission, of course) and trying to figure out what would be usable; engine OK, body and interior very rough. Not to mention he wants waaaaaaaaayyyyyy too much; I can wait... It may be more of a project than I would have time for. Hell, I was just excited to see another 928 in town!Tell your wife you should've bought stock in Meguiar's; her, uh, my baby is kept very clean...
right now.
