[Guest]

A VW friend of mine is trying to talk me into bossing my spare intake for CIS fuel injectors and running a GTI fuel injection system. It actually doesn´t sound like a bad idea, better fuel distribution, no carb issues, and since it is all mechanical injection, no wiring harnesses to worry about, the only custom things I´ll have to do are add an electric fuel pump, make a fuel pump blockoff plate, run a cable from the linkage to the throttle body, have the manifold bossed for injectors and get a shop to create the adapter to mount a throttle body on the manifold... possibly a 90 degree to mount the tb forward to make it easier to run the intake tube. The hardest part I really see is finding a mounting point for the airbox/fuel distributer and possibly needing custom lenght fuel injector lines.

I figure I could do it for $150-200 including all machine work and parts from the yard.


Does this sound like an idea worth pursuing? It would definately be cheaper than a webber 40 carb and is very adjustable for fuel mixture (turn an allen in the fuel distributer).

 

[Guest]

Bosch K-Jetronic does NOT like radical cams. It would barely run if you utilized a 300 degree camshaft.

 

[Guest]

Thanks for the advice, I´m not that familiar with CIS and since you seem to know you **** I´ll take your word for it.

Dan

 

[Guest]

No problem, I´d just hate to see you go through all that trouble to adapt it and then to have to take it back off.

 

[Guest]

would it be a good alternative for someone who wan´t planning on building a beast? If you wanted to stay with the stockish cam and wanted the convenience of fuel injection?

 

[Guest]

I´d say yes. I know of people with 2100 cc stroker VW´s that have everything BUT a radical cam, and it seems to work well until about 160 hp, then it hits a cap. If you´re gonna run a 1.9 or 2.0 litre, you´ll never hit 160 hp unless you DO have a hot cam, so I´d say the K-Jetronic would be fine for anything you´d likely run on the street.

 

[Guest]

Are you guys talking about running with the same ECU, manifold and injectors? Even the bore and stoke are inverse to Opels (over vs under square) so wouldn´t the ECU be mapped wrong. How do you adapt something so foreign?

 

[Guest]

He´s talking about the old mechanical injection from early VW´s. Pretty crude, with constant-flow injectors (not pulsed like electronic), but enough adjustments to compensate for added airflow and different engine characteristics. Also fairly trouble free.

Dan also insinuated he´d be adapting a carbureted intake, but an Opel FI intake would be far better, both in terms of airflow and power band. The Opel FI intake manifold has much longer runners and better torque. The stock carbureted intake, as we all know, has severe airflow limitations unless modified. It would be just as easy to weld the new CIS injector bosses onto the FI intake as it would the carb´d intake.

 

[Guest]

Thanks for clearing that up. (I should have reread and saw Dan said "mechanical")

This system doesn´t have a max air flow problem like a stock Opel FI system, and therefore allows for higher revs?

 

[Guest]

Actually the Opel´s L-Jetronic flows enough air, it´s just that the metering flap on the MAF is maxed out at 4500 rpm´s or so, and at that point stops measuring increases in airflow...so the engine has a progressive fuel curve up to that point, then it becomes linear...no more fuel can be added, it doesn´t know there´s any more air! It won´t run lean unless significant additional mods are made to increase higher rpm airflow. This is a good application for a rising rate fuel pressure regulator, it senses the increase in manifold pressure as rpm´s rise, and adds fuel pressure accordingly. You could tweak the tensioner (reduce spring pressure) on the metering flap, but this merely adds more fuel throughout the rpm band. So while it may run better at 7000 rpms, it will likely be too rich at lower rpms. L-Jetronic has severe limitations, which is why I don´t use it. I´ll go with a programmable ECU if I want injection.

 

[Guest]

The early 80´s Saab´s used a variant of the Bosch k-jetronic pulse time EFI on their motors, including the Turbo models. I am personally hip deep into retrofitting the Saab computer, sensors, and wiring to my Opel EFI manifold with the intention of utilizing the turbo at some later date. I´m detailing the wiring and mechanical mods, and taking lots of pictures. I figure that if it works it may be a viable alternative for others to consider too. I´ll keep everyone posted.

 

[Guest]

You mean L-Jetronic, right? Or LE- Jetronic or LH-Jetronic? These are all electronic, pulsed injection systems. The K-jetronic is mechanical constant flow injection. In the SAAB system, does it have an air flow meter with a flap, or a hot-wire MAF? If it´s an airflap, you´ll still have the air/fuel tuning issues the Opel has, even if the SAAB system still has higher airflow capacity. The only difference is the SAAB system should at least be digital (and possibly reprogrammable) instead of analog like the Opel.

 

[Guest]

You´re right, it is a LH jetronic with lambda. It is all electronic, and the air flow meter is calibrated and sized for much larger air flow than the Opel motor will ever see.
The Opel system is actually "easier" to "reprogram" because it is mostly analog in nature. The system times the injector pulses off engine speed, ie. more speed more pulses. The computer then adjusts the size of each pulse based on engine temp, air flow, and such. Withe this type of system, a different input can be compensated for by the very careful adjustment (read replacement) of input biasing resistors to the computers comparitors. A larger air flow meter could therefore be installed and the computer could be "calibrated" to use it just fine. Mine has been using a Mercedes airflow meter for years, because it mounts easier in the Kadett and the air filters are more readily available. I still get a steady 28mpg with an automatic, and there are no quirky spots in accelerating.
The Saab system has the further benefit of actually using the oxygen sensor to readjust the fuel mixture in real time and should get an additional 10-15% in milage, which is my real goal, without any loss in power. This also means that as long as the fuel air mapping in the ECU gets it close, the computer should be able to compensate with the oxygen sensor and get it right along the whole RPM range.
For guys without a whole lot of EFI experience, I would actually recommend one of 2 much easier options:
-The first is a Holly projection 2bbl TBI unit. they sell for around $700 and can be mounted on any V-8 or in line-6 up to 275 HP. A good shop or home mechanic should be able to mount it on an Opel 4 cylinder, and if you Opel gets more than 275 hp, we all would love to hear about it.
-The second option I´d recommend is to contact Turbo City and have a TBI system made for your Opel. They specialize in making stand-alone TBI systems to your specs using easy to find GM TBI components. The cost is significantly higher, $1400-2000, but I´ve never met anyone who wasn´t thoroughly pleased with what they got. Their systems us MAP sensors, and have very little impact on air flow, and since you are having it made, they can calibrate it for you cam, nitrous, gearing, etc in your car.
I´m sticking with the cheap old Saab option because I´m cheap in nature, and if the motor blows, I´ve got a 2.8 MPI GM V-6 with a 700R-4 waiting on the floor of my garage to go in. In a Kadett I can do that kind of mod and still un-do it later, but the GT guys just don´t have the room.

 

[wrench459 (R.I.P.)]

A word about "closed loop" fuel control.
The narrow band is just that.
High voltage .800mv means the exhaust gas has less oxygen than atmospheric.

Let's backup a few notch's
The O2 needs to warm up to somewhere ~650F before it starts to switch.
Most of the late model cars has heater's to speed the output up a hair.

As a side point ..a 32-36 or a 38 DGAS can switch a narrow band.

Yikes back to fuel control..
When the 02 is seeing .8mv the pcm/ecm will subtract a percentage of fuel to hit the target.
Of course it goes the other way around .
Say the 02 is reporting a reading of .2mv
The oxygen content is high
So guess what ...the puter commands more fuel.
Easy stuff

 

[Frozen Tundra GT]

this is officially the worst case of necroposting and reviving an old thread i have ever seen .

was there even interwebs in 2002?

 

[Knorm65]

this is officially the worst case of necroposting and reviving an old thread i have ever seen .

was there even interwebs in 2002?

I was only 7 years old haha!

 

[Gary]

/

this is officially the worst case of necroposting and reviving an old thread i have ever seen .

was there even interwebs in 2002?

LOL. This is an old thread! 3/9/2002 was the date the site went live with this style forum program.

Those "Guest" posts were from the old forum program we used back then. When I switched to the current vBulletin forum program, I had to write a script to convert the threads and posts as the databases had different formats. I knew very little about PHP/MySQL programming and it took a couple of weeks of trial and error (mostly error) before I was able to port them over. The members names did not get linked to the posts and the quotation marks turned into "./

 

[wrench459 (R.I.P.)]

Now lets get into self tuning.
First you'll need a good idea of the needed fuel across the map.
Then work up a base chart.
I love charts
Ok the PCM/ECM needs to hit the target right?

So it subtracts or adds fuel...this is done with long term fuel trims.
Also known as "adaptive fuel control" -self learning.

 

[wrench459 (R.I.P.)]

The minimum amount of air flow will also need to be taken into account.
Well yes a nice idle is needed right?

A hint ...spark advance helps when a long duration cam is used.
The vacuum is low at idle there by making the bypass valve almost useless.
As everyone knows if you increase spark timing at idle the vacuum will also magical increase.