effects of upping fuel pressure k jet?

[wes csi]

wondering if kjet fuel pressure can be increased and what effect it has on performance bec ive reading a bit bout it apperantly by adding shims to the metering head is this true so far ive replaced injectors(new) and it starts brilliantly cold or hot but with mods like oversise pisons and cam(276) dont think it performs like it should it overfueled with faulty injectors and revved more agressively oh yes its 1.8 8valve kjet engine code ev any advise or pics how to go about it would be appreciated

[h100vw]

You need to check the AFR to see if it's running rich or weak. Upping the control pressure will make it richer and that might not be what it needs.

[h100vw]

Bosch K-Jetronic Fuel Injection Manual

Have a read of this

The most important thing to remember that anything you do will affect the fuelling over the whole spectrum. The mixture once warm is controlled by the profile of the metering head.

There are ways to change this but you need to use either a 5th injector or frequency valve to modulate the fuel pressure. The 2 ways of doing that, that I know of, have dropped out of the market place since being introduced in the early 90s when the UK dropped leaded petrol.


Prove it's wrong before messing it up.
Gavin

[Jmac]

wondering if kjet fuel pressure can be increased and what effect it has on performance bec ive reading a bit bout it apperantly by adding shims to the metering head is this true so far ive replaced injectors(new) and it starts brilliantly cold or hot but with mods like oversise pisons and cam(276) dont think it performs like it should it overfueled with faulty injectors and revved more agressively oh yes its 1.8 8valve kjet engine code ev any advise or pics how to go about it would be appreciated

There is numerous check on Kjet with the right gear. Kjet is awesome IMO when right. i loved it back in the day. i could go on and on here. Get the gauge on it and check system pressure and control pressure. No need to muck around with the fuel pressure if its right. Yes you can shin the bolt on the metering head, you can also tap the plunger doen on the warm up reg, this up the pressure, you have to do this when the warm up reg gets tired. You wont need to touch this if it starts nice mate. You are talking performance, did the cam get dialled in???? Do you have a vernier cam wheel??? doesnt take much to retard it mate.
Jmac

[Bora Sport]

One of the virtues of the basic Kjet system is the simplicity. The dunny seat as we used to call it moves up or down in accordance with the volume of air going in. Therefore when you improve the air flow into the engine (by mods or increase in capacity) then the system automatically puts in more fuel. Obviously there are parameters but for example I changed my 1.8 KR 16V to a 2.0 9A 16V and the fueling was fine without touching anything. The problem IMHO is more likely as Jmac says to be with the timing either cam or ignition timing. The problem there is that it is basically a fixed setup in the ignition module. I ended up getting a VSAM programable ignition fitted to mine and after that it flew.

[Preen59]

wondering if kjet fuel pressure can be increased and what effect it has on performance bec ive reading a bit bout it apperantly by adding shims to the metering head is this true so far ive replaced injectors(new) and it starts brilliantly cold or hot but with mods like oversise pisons and cam(276) dont think it performs like it should it overfueled with faulty injectors and revved more agressively oh yes its 1.8 8valve kjet engine code ev any advise or pics how to go about it would be appreciated

Mate, that might make sense to you, but that post is a shambles.

If you want decent help, ask your questions in points and be more clear about your issues and what you are trying to achieve.


Also, you say it over fueled with faulty injectors? Don't confuse poor atomisation from a bad spray pattern with over fueling.

[wes csi]

thanx for the advice the car with 1deg retard cam timing (vernier) is peaky kicks at about 4500rpm when the cam timing is spot on its more torqey kicks in at about 3500 rpm but both ways its seems to run out of steam or fuel at about 6000rpm iwant it to pull all the way to 6500rpm got to wait three weeks to dyno it since they are fully booked (reputable ) but the atitued is the same for all tuners they wanna sell other injection systems to me my fear is that if it doesent make power kjet is gonna be blamed without really jacking the kjet properly so in the mean time im trying to get up too speed with kjet as for the injectors they dripping alota fuel when the car was parked any further opinions are appreciated pls hope the info is specific enough

[roccodingo]

Maybe if there trying to sell you a different fuelling system then there not fully conversant the K jet injection and its principles, one of which is reliability. I would go along with the other guy's, My K jet in the scirocco daily has hardly anything ever done to it in the last 23 years other than basic maintenance and tuning. For all the mileage its done it still runs well.

[GOLFBALLS]

thanx for the advice the car with 1deg retard cam timing (vernier) is peaky kicks at about 4500rpm when the cam timing is spot on its more torqey kicks in at about 3500 rpm but both ways its seems to run out of steam or fuel at about 6000rpm iwant it to pull all the way to 6500rpm got to wait three weeks to dyno it since they are fully booked (reputable ) but the atitued is the same for all tuners they wanna sell other injection systems to me my fear is that if it doesent make power kjet is gonna be blamed without really jacking the kjet properly so in the mean time im trying to get up too speed with kjet as for the injectors they dripping alota fuel when the car was parked any further opinions are appreciated pls hope the info is specific enough

Dude did you hear preeny?

I'm not trying to be a prick, but have you ever thought of using fullstops and paragraphs???!!!

Your posts are a like a jumble of non-stop words!

Just trying to help...

[Jmac]

Dude did you hear preeny?

I'm not trying to be a prick, but have you ever thought of using fullstops and paragraphs???!!!

Your posts are a like a jumble of non-stop words!

Just trying to help...

Ha Golf balls you saved me from saying that!!!!!!!!!!!!!!!!!!!!!
Jmac

[Preen59]

Ha Golf balls you saved me from saying that!!!!!!!!!!!!!!!!!!!!!
Jmac

And me saying it AGAIN! haha.

[Oneofthegreats]

Judging by what I can sort of decipher from your posts & also agreeing with everyone else.

It would make it much much easier if you make your posts clearer with actual sentences & explaining your problems in point form.

That way some of use can read & interpret your info as best as possible & hopefully give you some sort of direction.

Now if these people are trying & pushing you to install EFI for nearly stock VW Golf. Its because they have not one idea between them about the system!

A good place to start would also be purchasing a book on Bosch K-Jet fuel injection as already advised & learning how the system operates.

After all. How can you start modifying & playing around with things, if you have no clue how it works in the first place?



First & foremost.

If your K-Jet system is 100% & has no problems eg. hard start, faulty accumulator, leaky injectors etc, then I'd start looking at other things. But to start off with

The system "must" be in 100% operating condition


Now! Straight away I'd be checking exactly what your A/F ratio is & just as importantly, your CO%.

In NA (normally aspirated) form I always set my K-Jet cars up with 2.0% CO. This is without any additional loads. Eg. lights on, thermo fans running etc.

Your mixture/airflow rate is all in the design of the air flow sensor bowl. If you've seen enough of them, you'll see there is differences in how they are shaped. This defines how your car adjust's its A/F ratio through out load/air flow requirements,

If your CO% is approx 2.0%, then I'd be looking into your fuel system pressure.

System pressure

68-78psi

Control Pressure

Cold (10°C) approx 15-20psi
Hot approx 49-55psi

If this is right, then you can look into increasing your fuel pressure, or as I've found & used several times over & recommended it to anyone & everyone with VW K-jet cars before increasing fuel pressures -

Install a K-Jet airflap & metering head out of a larger capacity K-Basic car!

I always recommend a setup out of a early 80's Volvo 2.1-2.2L car. The airflap is larger diameter, lifts up more (increasing fuel flow through the metering head plunger slots) & also the metering head flows more fuel to suit the larger capacity engine.

(The VW K-Jet injectors are one of the highest flowing injectors, so there is no need to go in search of better ones.)

This provides very noticeable increases to throttle response, bottom end torque & high rpm fueling. This fueling system will also be able to handle approx 200+hp in FI (forced induction) form, as I've proved with my own install.

But it has to be working 100%!

If tuned right eg. 2.0% CO your fuel consumption shouldn't increase by all that much either.

I've been using this setup for over 14+ years now & have never had a problem with it & still get high 7's-mid 8's litres per 100km. This is even with the K-Jet turbo install!

Just recently I got 440km out of 35L!!!!!. Not bad for a turbo'd car using K-Jet!

Thats 7.95L per 100km!

My K-Jet turbo build for interest sake

http://www.vwwatercooled.org.au/f55/76er-swallowtail-k-jet-turbo-build-38095.html

[Preen59]

Read Tim's info he has posted carefully and possibly print it out for your mechanic- He knows his ****.

[Jmac]

Agree and again i say K jet in its day was an awesome set up when it was right. i loved it. Still do, only in the Uk teebag fuel filler necks killed them , they hate water and crap. they also hate lying around, had many 911s out of for a Sunday once in 6mths die. Get the Bosch K jet book, well worthwhile read, also includes L and Digifant FTW.
Jmac

[wes csi]

Im really impressed with u guys i feel your expertise does not match up too your english skills. There i used a full stop happy. Now can u please give me some vw technical advice because i feel that the question was clear enough although gammatically incorrect and yes you are a prick because i think u know nothing about kjet and as of now i am not interested in anything you have too say, if you really want to talk about something speak to your wife, shrink, dog i think your get the point. As for the gents that gave good and serious advise thanks for being genuine about my problem.