Author Topic: Injection Systems  (Read 6757 times)

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Neil_Corrado

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Re: Injection Systems
« Reply #20 on: February 14, 2006, 03:08:41 pm »
Im sure you could fry your ecu on a golf, I think its sparking they dont like so much.
K-jet is good but its old now and not that fuel efficient.

Thanks for pointing out the broken dip stick tube as a air leak i hadnt thought of that.

Not that fuel efficient compaired to what?

orggti

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Re: Injection Systems
« Reply #21 on: February 14, 2006, 06:26:13 pm »
Compared to modern electronic fuel injection and even digifant. K-jet is supposedly more fuel efficient than carbs but then VW did use solex carbs which nobody has ever raved about and my 1.6 gti k-jet uses way more fuel than my girls 1.5 carby model. The problem with K-jet is it runs richer and richer as it wears out, also a problem  is its age now, its never been 20 years old before, but now it is. Thats the thing with cars like audis, everyone used to own one and thinks they know what goes wrong but these cars have never been 20 - 30 years old before and nobody knows what goes wrong after that time. Except for everything.
 K-jet WAS very good but now COMPARED to new fuel rail systems its old gas guzzling worn out and difficult unless it just works well.

Neil_Corrado

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Re: Injection Systems
« Reply #22 on: February 14, 2006, 09:08:07 pm »
True, but K-jet appears easy to adjust with the correct equipment.

Offline rambo_005

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Re: Injection Systems
« Reply #23 on: February 14, 2006, 09:32:15 pm »
My Digifant Mk2 will do 600-700km to a tank round town driving if you're driving efficiently.
NZ: 1988 Mk2 Golf VR6 3 door manual
UK: 2008 Mk5 Golf R32 3 door manual

Neil_Corrado

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Re: Injection Systems
« Reply #24 on: February 14, 2006, 09:34:20 pm »
If im being nice the Kjet KR will return around 7.5 to 8.4L per 100km.

orggti

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Re: Injection Systems
« Reply #25 on: February 15, 2006, 08:51:27 am »
True, but K-jet appears easy to adjust with the correct equipment.
Appears easy to adjust with the right equipment? what do you mean?

Neil_Corrado

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Re: Injection Systems
« Reply #26 on: February 15, 2006, 09:16:48 am »
Fuel pressure is easy to increase or adjust as required(by shimming the regulator), the mixture can be adjusted. None of which can be done with modern systems. K jet is great in the fact that it is a 'simple' system.

orggti

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Re: Injection Systems
« Reply #27 on: February 15, 2006, 09:27:23 am »
Well I hadnt heard of you being able to shim the regulator and ive never heard of anybody actually doing this, I dont think this is nessisarily an adjustment but a way to get the correct fuel pressure. I dont think you can shim the pressure up to make it go faster?
And yea you can adjust the mixture by turning a screw that raises or lowers the air flap but once again its just a matter of getting it right if its been knocked or moved or worn slightly.
 The System is simple sort of (tho it seems very few acctually really understand it) but you can get some very tricky faults with it and unless you want to replace everything at a cost of about twice what any old K-jet car is worth you can have a hell of a time with it.
How bout i bring you a 90 quattro over thats been giving me some probs and you show me how simple and easy it is to fix and get running right ;D

Neil_Corrado

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Re: Injection Systems
« Reply #28 on: February 15, 2006, 11:36:56 am »
Ive got a performance book at home that tells you how to set up k-jet's base settings.
If you shim the pressure reg by 2mm you get a pressure increase of 10psi.

GolfGeek

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Re: Injection Systems
« Reply #29 on: February 15, 2006, 02:59:43 pm »
Fuel pressure is easy to increase or adjust as required(by shimming the regulator), the mixture can be adjusted. None of which can be done with modern systems. K jet is great in the fact that it is a 'simple' system.
Mixture is adjusted automatically by the ecu in new systems even digifant and manual adjustment is not required. The ecu ensures optimal mixture so why do you want to fiddle with it?

The Admiral

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Re: Injection Systems
« Reply #30 on: February 15, 2006, 05:01:31 pm »
Mixture is adjusted automatically by the ecu in new systems even digifant and manual adjustment is not required. The ecu ensures optimal mixture so why do you want to fiddle with it?

Don't forget that Digifant-II as used in Mk2 Golf was open-loop (for non California/US models) and as such had no feedback. Mixture adjustments on that system were just based on mapping of various sensor inputs against VW's known fueling under those particular conditions. Wear couldn't be taken into consideration.

Later models had exhaust sensors (lambda, for those who don't know) which measured the oxygen content in the exhaust and trimmed fuel to suit the engine load conditions. This system could compensate for wear.

Hope that helps!

The Admiral

orggti

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Re: Injection Systems
« Reply #31 on: February 15, 2006, 05:30:02 pm »
It helps me admiral not so sure bout the others :)
 we could all shim up our K-jet systems and watch our old injectors leak  ;D

I suppose my audi 200s computerised dizzy is all pretty much closed loop as you say as well. When did they start to react or open loop? 

Offline typ53

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Re: Injection Systems
« Reply #32 on: February 15, 2006, 09:09:08 pm »
Fuel pressure is easy to increase or adjust as required(by shimming the regulator), the mixture can be adjusted..

It strikes me that that would be a rather broad-stroke method of adjustment - Wouldn't shimming it would adjust the pressure across the board, so it would perhaps improve system pressure in the range where the mixture is a little lean, but potentially would leave it too rich in the part of the rev-range that's already fairly rich?  I understood that the variation of mixture with RPM (ie airflow) handled by the shape of the cone in the airflow meter, and thus rather difficult to change.

Please correct me if I'm wrong, because my opinion above is the basis for my link computer retro-fit project, and it would save a whole lot of work...
The Fleet:
Orange Roughy:'90 16v Corrado
'89 Carrera 4. 
'12 330d Touring
Still trying to figure out how to get 'em all to fit in a single garage....

hartster

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Re: Injection Systems
« Reply #33 on: February 15, 2006, 10:30:17 pm »
If you're running K-Jet, and you're a DIY-er, it helps to have something like this:

http://www.mytoolstore.com/toolaid/diagn02.html

Just don't lend it to your 'mates' as I have found to my cost and intense frustration!

Neil_Corrado

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Re: Injection Systems
« Reply #34 on: February 15, 2006, 10:34:35 pm »
It strikes me that that would be a rather broad-stroke method of adjustment - Wouldn't shimming it would adjust the pressure across the board, so it would perhaps improve system pressure in the range where the mixture is a little lean, but potentially would leave it too rich in the part of the rev-range that's already fairly rich?  I understood that the variation of mixture with RPM (ie airflow) handled by the shape of the cone in the airflow meter, and thus rather difficult to change.

Please correct me if I'm wrong, because my opinion above is the basis for my link computer retro-fit project, and it would save a whole lot of work...

Yes your right, its an increase across the rev range.
Why are you changing the ECU? If you look at the metering head and injectors there is nothing electrical there at all. As far as i can tell for Kjet it does nothing with the actual fuel injection, its simply mechanical. The amount of fuel is controlled by the air sensor plate, the further up ward it moves (more air) the more fuel the metering head gives. No ECU input what so ever.
The ECU controls the cold start injector and warm up regulator but thats it, i think. (which is why you never see upgrade chips for Kjet!)
There are two type of 80mm cone, those with a 6.35mm lip and 3.2mm lip, the thick lip cone runs slightly richer than the thin. The European (which our KR's are) fuel distributor has different valving to richen the mixture at high RPM.
« Last Edit: February 15, 2006, 10:38:04 pm by Neil »

Offline typ53

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Re: Injection Systems
« Reply #35 on: February 15, 2006, 11:25:43 pm »
Yeah, that's  all true to my somewhat limited knowledge. It's been a long time since I've been anywhere near a dyno, but I seem to recall that the mixture was rich down low, a bit lean in the mid-range and rich up at the top end again.  I my rather vague memory is correct then I guess shimming would fix the mid-range issue, but what would it do to the performance elsewhere?  Plug fouling from low-RPM cruising? Lessor fuel economy I guess, if that's important.  Perhaps Jeremy might shed some light here? 

I drove a jetta 16v a number of years ago that had an 'inject'? computer system (ie fully electronic injection), with no other mods and it really pulled, especially in the mid-range. Needless to say, i was impressed.  Not impressed enough to spend $2k on the computer he was selling at the time, but it left an impression.

I know the conventional wisdom is that K-jet is good for 'x' horsepower, but I'm sure that with other mods like cams the ability to fine-tune fuel flow at various RPM/load settings would produce results. That airflow plate has got to be producing a reasonable pressure drop in the intake system too.  I don't know if it's a limiting factor with a standard setup, but the potential is there.

A computerised system also has the advantage of an oxygen sensor and closed-loop mixture adjustment whilst cruising. 

Those are all reasons for the change, and I know there are a myriad number of reasons against it too.  The truth is: I've had the car 12 years now, I know the car reasonably well and I'm a little bored with the performance of the 16v as standard. I like to tinker and reckon it will be an interesting project. A number of guys on The Vortex seem to be changing to EFI with reasonable results if you believe their posts. 

I'm a bit of a skeptic, but reckon it's worth a crack.  End of the day, if I'm careful with the implementation of it and it doesn't work well I can always put the k-ket back in and go back to the way it was.

Mind you, it's not going to happen anytime soon: I bought the computer a couple of years ago and so far the loom is only partly installed.  Still, the house renovations are nearly finished, so the excuses are starting to run out...

The Fleet:
Orange Roughy:'90 16v Corrado
'89 Carrera 4. 
'12 330d Touring
Still trying to figure out how to get 'em all to fit in a single garage....

Offline typ53

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Re: Injection Systems
« Reply #36 on: February 15, 2006, 11:27:21 pm »
My that turned into rather a long rant.  Oops.  :-\

Sorry if it's hijacked the thread...
The Fleet:
Orange Roughy:'90 16v Corrado
'89 Carrera 4. 
'12 330d Touring
Still trying to figure out how to get 'em all to fit in a single garage....

orggti

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Re: Injection Systems
« Reply #37 on: February 16, 2006, 07:39:29 am »

K-jet is all mechanical and adjusting shims is to get the pressure correct only. No benifit at all increasing it.
Some newer K-jet has a basic ecu that alters ignition timinmg only like my 200. The warm up valve at the front of the motor deals with cold running and a thermo sensor activates the cold start injector. Its best to just disconect the cold start injector.
 If you have the time and money fitting electronic injectors and a link computer means that finally its worth going to a dyno shop and telling them how you want the car to run, ie flat out at top end or nice and smooth for round town.
K-jet is non adjustable and is now old tecnology and wearing out fast. Also, as is constantly made aware to me, nobody seems to understand it properly. Its completely basic and once worn it runs rich. And yes it is all in the shape of the cone that dictates how much fuel it gives at certain air speeds. They spent a long time getting it right.

« Last Edit: February 16, 2006, 07:43:51 am by orggti »

Neil_Corrado

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Re: Injection Systems
« Reply #38 on: February 16, 2006, 08:23:58 am »
What sort of power figure do you want? Or is it the adjustability your after? Kjet with standard injectors will supply enough fuel for 400hp. Although in the US with turbo applications Callaway only used it up to around 230hp. Rossi's Corrado drives very well, thats got a 9A block with cams and standard injection.

Offline typ53

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Re: Injection Systems
« Reply #39 on: February 16, 2006, 09:17:47 am »
I don't really have a power target in mind Neil, to be perfectly honest, it's more the exercise than anything else that's driving this - It's the Engineer in me coming out.  It seems worthwhile and I'm curious to see what sort of difference it will make and whether or not I can do it. 

It might be an expensive exercise for sure, but hey! everyone's got to have a hobby, right?   :)

I have most of the parts that I need now, it's just a matter of finding replacement pins for the VW electrical connectors, someone to make up some fuel lines for me, and emptying my garage so that I can get in and start work.  The latter is going to be the big hold up.  At the moment I can't get much past the door.  :-[
The Fleet:
Orange Roughy:'90 16v Corrado
'89 Carrera 4. 
'12 330d Touring
Still trying to figure out how to get 'em all to fit in a single garage....