Bosch K-jetronic CIS - WUR Mod - How-to + Why
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- Опубликовано: 22 май 2022
- #bosch #niche #youtube
This is the next instalment of the K-jet videos. The WUR mod or warm up regulator modification.
In this video I show you exactly how to carry out this modification and explain the reasons behind it by using my model K-jet unit along with a demonstration on a running vehicle showing what happens to the control pressure when adjustments are made which then confirms what has been discussed.
Standard control pressure with a working WUR (UK Models)
- Cold Start Pressure 1.7 - 2.1 Bar (24 - 30 psi) approximately
- Warm Pressure 3.4 - 3.8 Bar (49 - 55 psi) approximately
I have set my control pressure to 3 Bar which as noted in the video provides an AFR of 13 at 6700rpm which works for my 1.9ltr 16v engine.
But as a rule of thumb lowering the control pressure to 35 - 40 psi will have the desired effect in performance gain.
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Superb video, beautifully explained.
Really taught me that the WUR and the distributor are essentially a hydraulic control system with gasoline as the fluid.
👍🏻👍🏻
Excellent video. Thank you!
Excellent job. Well done. Thanks for sharing.
What a perfect explanation of the inner workings of the WUR! 👍
Thanks
Great video again…the unusual use of “orifice” again 👏🏻
Brilliant!
Thank you for the extremely helpful explanation. Im a visual learner and this really helps me understand the system. Dealing with my first CIS system (83 240 GLT) and excited to dig into it!
No worries and hopefully it helps
What a great vídeo 👍👍👍
Thanks
Good 👍 stuff
K-Jet For Life! 🥰
100% It was well ahead of its time
Wow! Amazing explanation...
Thanks
@@GreyGooseRestorations What are the parts required for the conversion of CIS-E to K - Jetronic?
All you need to do is put a plain CIS metering head on the car and the electrical plug for the CIS-E just put it tidy out the way
Good video and some clear explanations. I have a question though. You have a double diaphragm WUR. That means the vacuum take off changes the pressure on the pin. The bit that moves under vacuum only affects the inner spring seat, and that is the bit that you are adjusting with the allen key. Effectively it is fuel enrichment at WOT (when vacuum is lowest). My thoughts are that the allen key adjustment is to control the effect the vacuum has on the control pressure, allowing you to tune for WOT. When you look at how a WUR is supposed to be set-up for cold/warm pressure, it focusses on moving the bimetallic strip or the fuel cell in and out of the WUR. I'm convinced that the allen key is there for adjusting control pressure in line with vacuum. A normal WUR (with no vacuum) only has one spring, so I'm convinced there is logic in may argument but I've been unable to find any discussion on it. Do you have a view on that?
Theres only one diagram in the WUR.
The engine vacuum reduces the force on the metal diagram allowing more fuel to pass out of the control line reducing control pressure. So when vacuum is applied via opening the throttle this removes force on the metal diagram momentarily dropping the control pressure allowing the fuel pin to rise more providing more fuel
The bimetallic strip again reduces pressure on the metal diagram allowing more fuel to pass through untill its warmed up then the pressure is increased so x amount of fuel is passing through.
The allen key physically removes pressure off the metal diagram so once its all warmed up there is more fuel passing through providing a reduction in control pressure
great video I have a spare WUR I will do this mod with sometime.How does this WUR mod compare to shimming the metering head fuel pin/rod?
Thanks, the WUR have a different effect compared to shimming the metering head which just raises the system pressure that helps with residual pressure in the injector lines once they are opened at 3bar.
K-jet + Turbo owner here. Major thing that you didn't tell people is that there's a possibility that the airflow meter plate will move up too easily if the control pressure (one that is regulated by WUR) is too low. Meaning, you can enrich your fuel mix at lower RPM, but when you will go WOT at above 4000 RPM the airflow meter plate will top up and fuel mix will become VERY lean. Resulting in engine damage even. So, the best is to measure AFR to see if the engine has started to lean out at high RPM after you've decreased your control pressure.
In principle yes but k-jetronic generally drops rich as soon as the throttle is opened then settles and starts to go lean top end.
The WUR mod allows the plate to rise more thus uncovers more of the fuel slits providing more fuel up top.
The 16v doesn't breathe hard at low rpm so the plate won't rise that much to overfuel enough to cause any damage, remembering this mod had been done since the mid 90s
In an ideal world the WUR mod should be done in conjunction with RR and AFR or live road testing.
❤Love your work.
I own a 9A 16V motor that's really heavy on fuel and misfires everytime the engine cools down for a bit. And also has a slight knocking sound on start up then goes away but can be heard knocking again at 3500-4000rpm
Thanks
Is your engine timing and ignition timing set correctly
@GreyGooseRestorations yes timings perfect..it's just I think the kject system isn't working 100% because it's missing a few parts...can I perhaps catch you on whatsapp
Yeah no problems, on my Facebook page click the WhatsApp button thing
Very happy for another Golden Kjet Video.
So in a nutshell you are saying that the hole needs to be drilled in the WUR housing to expose an allen key slot which when turned the correct direction will decrease the counteracting fuel pressure on top of the fuel pin which then allows the fuel pin to move higher up the chamber and expose more fuel slots?
I have the following questions:
1) You mention that you decreased WUR pressure from 50 to 30 pSi because this was optinal for your car. What are the considerations to be taken into to recognise the correct WUR pressure for your vehicle?
2) I assume that the modification of the WUR does not require tinkering of the AFR because the air flap and fuel pin are both moving higher upwards due to decreased cou teracting WUR pressure?
3) You mentioned previously to me that honing of the fuel pin is not worthwhile and that one should rather modify the WUR. But one can also play with the master system pressure via the fuel pressure regulator on the side of the metering head. Would this not also increase fuel to the injectors? Won't you also do a video for us on the fuel pressure regulator?
4) Where does one purchase the gaskets for the WUR when doing refurbishment?
Again, excellent vid!
Thanks
The WUR mod alters the control pressure and either richens or weakens the mixture right across the revs.
K-jetronic engine tend to run lean at higher revs and benefit from checking and getting the control pressure spot on.
But having proof of the current setting on mine achieving an AFR of 13 at 6700rpm.
I also run just over 6bar system pressure not the ideal 5.5bar however this will only have a direct effect on injector residual pressure (once they have opened at 3bar)
I will see what I can do 👍
@@GreyGooseRestorations forgot to ask... won't decreasing the WUR fuel pressure at some threshold pressure value cause the risk that the fuel pin won't be pushed back down the channel? (Sticking fuel pin)
Nope, if all is well and functional then there is still sufficient pressure to keep the pin doing what is needs to do 👍
i have an audi 2.3 with a KE3, ive heard that you can get more out of it by adjusting fuel pressures since theyre set for emissions out the factory. but the KE3 has a EHA valve instead of a WUR so i was wondering if youre capable to show something like that too
Yes you can adjust the small 2mm allen key hidden behind the flat head screw on the back of the EHA valve on the metering head
I made a rookie mistake and made both the adjustment you describe and the adjustable pin method. Is there a base setting on your modification that I should target on my WUR?
Unfortunately, it's hard to have a base setting as there are too many variables with where the fuel cell sits, the heating element pin site and the spring rates on both the springs and how well the vacuum diaphragms are working
Hi mate Iv had a problem with my jetta and still do when cold it start lovely when hot and turning it off for 15 minutes and back on still fine .. but leave it for hour or so it start like lack of fuel like it evaporated
Or the fuel has returned back on itself and run terrible for 10 seconds what could that be ? Grate video on the k-jet
Have you looked into the fuel accumulator that’s just in front of the fuel pump?
Where about do you get your rebuild seal kit?
www.missingparts.de
Your Beautiful assistant is looking nice on the Audi rims...
Does the warm up regulator get a constant 12v?
Nope, it should only get voltage when cranking, its fed from the fuel pump relay if memory serves me correctly
@@GreyGooseRestorationsdo you mean it runs constant 12volts when the engine runs/cranks?? Does the 12v not cut off sometime during the engine operation? I just want to get a clear understanding on how the electric side works...I'm currently working on a mk2 8valve gti which I bought and previous owner removed the connector plug so the engine cuts off and idles low when it's hot but high on idle when cold...that's when I came across your videos n channel which I'm subscribed to.
Its not constant no, ill have to dig out wiring diagram, tad rusty 😅 possibly connected to the starter solenoid allowing voltage to heating element. Ill have to check
@@GreyGooseRestorations ok...Thank you very much...that will help a lot...I was thinking of connecting it to the ignition but who knows what would happen...I don't want that element to burn out...
@@GreyGooseRestorations I got this link with a diagram that shows it connects to the Aux Air Valve...though I can't make out what the guy is saying...We just have to confirm is this the right way to go...ruclips.net/video/7I8omMFRAi0/видео.html
Where abouts is your garage located please.
After changing a code plug on my e21 and having to remove this.
It’s running rich and cannot run for long.
Thanks
Hi, im located in Wiltshire, I have a Facebook page with contact details if your need
Thanks Iv found tbe Facebook page and following. I’ll message you on there and give you a call if that’s ok.
I need mine sorting after remining it to replace a core plug😫😂
Great video, thanks for the explanation but this is for warm pressure regulation. How do you set up the cold pressure? I don't have a good idle on cold and stalls after a few seconds from start. Probably the cold pressure is wrong. Starts easily on cold and warm and runs good on warm. On warm I have 3,5bar from 30degree celsius and on.
Thanks, cold pressure is really what it is, it can be reset by adjusting the housing.
What pressure do you have on cold?
@@GreyGooseRestorations
@@GreyGooseRestorations I have 1,2 bar at 21 celsius degree. 2.0bar at 35 and 2.1 at 42. I have checked the 020 WUR and it is inside range. It seems lack of air. The air idle screw is open at maximun and even that, stalls.
The WUR pressures aren't the issue, have you checked your C02 adjustment screw at the metering head
@@GreyGooseRestorations No, I have not the gas analyzer for performing the test, I will take the car to a garage with it, thanks.
Thanks for the videos explaining the inner workings of K-Jetronic so well! I have some troubles with the engine of my 1986 Audi 90 running lean on part load (engine runs rough). Adjusting CO only masks the problem, on idle CO is way too high now but after a drive the spark plugs are really white so the mixture seems to remain lean. I will lower the control pressure - already made that hole after refurbishing the WUR, it may be the reason (although according to the fuel pressure gauge I have, that pressure is spot on - 4.1 bar - this is as per the documentation for the WUR fitted on my car, but still this may be too high for some reason). Should you have any different views I'd love to hear them! FYI: fuel distributer and WRU have been refurbished and injectors replaced, air flow meter position seems to be correct: centered and 1.9mm below the edge (I haven't touched this).
Glad it was helpful, have you check all your vacuum hoses? Has the ignition timing been set/checked?
@@GreyGooseRestorations Hi, yes, all vacuum hoses checked a dozen times by multiple people and ignition timing is correct as well. Warm/cold start is great, acceleration is flawless. Just when running the car in low rpms (e.g. when driving 50 km/h in 4th or 5th gear) the engine is running rough if CO is set to the correct level. With increased speed the problems disappears. The issue is driving me mad, spent quite a lot of money on it already but it's hard to find expertise on this system nowadays...
Is your throttle stop set correctly?
Small 8mm nut and threaded section.
Loosen the nut and unscrew the threaded section a bit.
Loosen the mirco switch and let the throttle close fully.
Screw the threaded section untill it just touches the throttle arm, turn a further half turn and lock the nut.
Adjust the microswitch so that it is pressed in with the throttle closed.
@@GreyGooseRestorations I would need to check. My car does not have a micro switch AFAIK - it's all mechanical (JS engine, also used on some VW Passats from that era). Question if I may, what does the throttle stop control?
Controls the amount of air the will pass the closed throttle which goes hand in hand with the idle screw and stops it wedging itself shut.
Why are you doing this?
To adjust the fuel pressure?
Can't you just do that by adding a shim to the line out nut?
Are you raising the whole fuel pressure or just the warm up pressure?
Please explain
This is the control pressure (WUR Pressure) lowering the control pressure in simple terms allows the fuel plunger to raise easier providing more fuel.
@@GreyGooseRestorations So to increase fuel pressure, shim the return pipe.
To make response faster, lower the WUR as in your video?
My WUR does not appear to have the Allen screw under the lower spring. I have the WUR from a US model 88 Cabriolet JH code CIS Lambda. So how would I modify my WUR to reduce the warm control pressure using a screw or bolt?
Ah ok so yours will be presumably one without the vacuum section. These can still be set but require the fuel chamber and the heating element pin knocking either in or out to get the desired pressure
That will require tapping or somehow having fine control while pushing the chamber down, or pulling it up. I installed a bolt in the cold control pressure pin to adjust it in or out, but I’d like something similar for the warm side.
@seanporter6795 you can so the same on the warm side so both parts have screw threads that hold the parts in position, personally i prefer the harder way to actually press/knock the relevant parts in or or out as they stay put, with the tapped bolt and lock nut method leaves it open to coming loose as there are a lot of vibrations going through these.
It would be nice to create a puller that could latch onto the fuel fittings and pull the fuel chamber out. Then I could tap it down (back in) using a hammer. I think lowering the warm/hot control pressure means pulling the chamber out.@@GreyGooseRestorations
@seanporter6795 normally if its stock its a case of knocking them in and test but its hard on the car as you need to do it when its stone cold then see what its like warm then adjust then leave it to get cold then check, very long winded but once set it more reliable
Is this the same for the Mercedes 300e w124
In principle yes, pressures may be slightly different tho
Does this work on WURs that have the brass plate on the back?
Do you mean the large flat plate? If so nope
@@GreyGooseRestorations I think it's slightly dished or conical. Its about 1.5 to 1.75 inch or 30 to 40 mm diameter. Presuming this mod doesn't work for me,
have you seen the digital wur, and if so what do you think of them? They are very expensive but may be a convenient solution. I have actually adapted this system to a suzuki samurai and it worked very well for a while. But now it runs rich always and I cannot get it to lean. I just dont want to throw $$$$ at it because its my beater 4wd.
@deadbrother5355 yeah thats the type for a faster warm up type, best bet is to get a 16v golf wur with the vacuum unit and adjust that like the video
Yes seen those, very good but hell of alot of money for what they are, personally id stay with OEM stuff, its worked good for 30+ years
@@GreyGooseRestorations thanks for the feedback.
Where would I find one? Junkyard?
@deadbrother5355 more likely ebay or contact dubstock
I have a mercedes with k jetronic and I dont get any resistance on the air metering unit when I press it down and when I crack the lines going to the injectors very little amount of fuel comes out could that have to do anything with WUR?
It could be WUR issue or system pressure issue, are you able to check your system pressures
@@GreyGooseRestorations unfortunatelly no I don't have the equipement needed,I would like to get the testing equipement thought because more than likely I would end up with more K jetronic cars,could the WUR being clogged prevent fuel getting to the distributor?
Missingparts.de are very good with parts and their test kits.
Its always worth taking the WUR off to spray some cleaner through the inlet and outlet ports.
System pressure is the first port of call as that will point you to your issue
@@GreyGooseRestorations thanks but those testing equipment they have don't have the right fittings to connect to mine unfortunately😒 you thing then that I could try to spray something like a carb cleaner throught the holes to see if I can get it to unblock without removing the WUR because it's in a very bad location on my car I should also remove the oil filter as well. Thanks by the way for helping me much appreciated.Could I find you on social to add you?
Yeah just take the two banjo bolts/lines off and spray some through
Think this would apply to a 1984 380SL?
Hi, yes the same principle will apply to all cars with a WUR with vacuum enrichment chamber
@@GreyGooseRestorations Thanks! I have a rebuild kit coming in the mail, so I might as well give it a shot
Hi can I do mod to my ford capri 2.8 wur
Yes, same principles apply 👍
Great vid!! Doing this mod on a MK1 DX 1.8 GTI engine, the original wur has no vacuum connection. The 16V wur has one. Should I block the vacuum inlet on the wur? Or connect it to the vacuum system of the throttle body? Thanks so much for the info!
No worries, you'll need to use the vacuum on the 16v WUR, normally i T peice them into to long idle valve pipe that runs across infront of the inlet manifold.
@@GreyGooseRestorations great 👍 will look into that! Thanks for the speedy reply 😉
Wait can I drive the KR K Jet and the whole system with it on a PL?
Yes, the PL and KR block the same engine so will work fine with KR K-jetronic system
@@GreyGooseRestorations I got both laying and also both heads and the big intake so should I use the KR parts for better performance?
Out of the heads the early 027 cylinder heads are generally better and the larger 50mm intake will allow for more air flow.
@@GreyGooseRestorations good to hear that 😁I think I need to rebuild some stuff then
Are interested in doing any private work on my cars your knowledge is second to none £££
Yes, but not for a month or so as im booked up with 2 16vs for set ups and a metering head rebuild. Send me a message via the Facebook page Grey Goose Restorations and we can sort something out 👍
I was literally getting brainwashed when watching this I didnt understand where it was, but at the location you have it, I dont have ANYTHING related to that box you are talking about, the WUR
I do have the '87 GTI 16v KR, yet nothing like this
Is my model too old or something?
If its a k-jetronic then it needs an should have a WUR as that is what sets the control pressure.
Gdym rozumial po angielsku tez bym sie cieszyl..... a tak walcze z k jetem.
How could i help?