Shimming Metering head

[coullstar 0]

At the recent RR day at Star I was speaking to a guy (Dave Mason with the uber Audi) and he mentioned something about shimming the metering head to gain a little power. I have done a search on this forum and managed to find a Kjet manual which has explained a lot.

I realise that if you shim the flap to open further then more fuel will be added to the mixture but I am unsure of exactly where they go and what size shims you need. Can anybody help?

This ,to me, effectively seems to have the same effect as the WUR mod which I have looked at and understand (reducing control pressure etc) or can both mods work in conjunction. I take it the WUR is only really beneficial at high rpm/loads to prevent leaning out. Do these mods drastically effect fuel consumption?

 

Alos can somebody point out exactly where the WUR is.

[aide 0]

i assume you'd shim the cylindrical piston which rests on the metering flap, don't know how much tho if you do it let us know how it feels!

 

WUR is on right hand side of engine, below the cold start valve i think?

[h100vw 0]

I think this shimming would be required on a well modified kjet motor. Chnaging teh control pressure will cause a richening/weakening throughout the rev range.

 

The sahpe of teh cone in the metering head is what controls the mixture. If you are running out of fuel at the top end then changing the cone is the 'right way' to adjust the problem.

 

You can get the mixture you need, at the expense of richening everywhere else( more fuel consumption), by reducing the contol pressure further or increasing the mixture setting or adjusting the mixture at each cylinder. Under the cap by each outlet on the metering head is another 'mixture screw'. clockwise to richen anti to weaken.

 

IMHO Vsam and Kstar are the best solution to this issue. You can get the richeing you need yet still maintain good economy. Both come up secondhand for little money and they are almost infintely adjustable.

 

Again IMHO the Vsam Pro on my C did not make a noticeable difference when connected.

 

Gavin

[coullstar 0]

WUR is on right hand side of engine, below the cold start valve i think?

 

By RHS do you mean drivers side? Could you point it out roughly on the pic above.

[aide 0]

it's the thing with two pipes running to it, one flow and one return

 

just above blue cold start valve on picture above

[coullstar 0]

Here?

[aide 0]

AFAIK yep

[flusted 0]

Are you sure mean shimming the meterhead and not the fuel pressure regulator? You can shim the fuel pressure reg to increase overall fuel pressure

[coullstar 0]

That might be it. Know anymore Flusted?

[flusted 0]

Yeah its well easy.Look at meterhead where all the injector pipes go.Theres a 15mm nut on the right hand side of meterhead.Undo this and you will see a pin type thing with a spring over it and some small washers.The more washers you add the higher the system pressure will run at.Its worth noting system pressure is usually about 4.5bar and you want to up it to about 5.4 bar which is done by adding 1 washer of about 2mm thickness.Ive tried packing loads in there till my car didnt start then removed em till it did (probaly not advisable!!!!)

[flusted 0]

Also upping the pressure doesnt richin mixture.Injectors open at 3.3bar so if you wack 5.4 bar at them they will open easier with a better spray pattern but they WONT spray more fuel!

[h100vw 0]

You can adjust the warm control pressure with the WUR. In the back under a tamperproof cap is a 4mm allen key. Clockwise will REDUCE the control pressure and up the CO. Anti clockwise will INCREASE the control pressure and reduce the CO. When you go WOT the vacuum connection reverts the WUR back to a 'cold' condition, this jacks up the fuelling.

 

If you want to be well read on this subject I would suggest reading 'how to tune and modify Bosch fuel injection systems' or similarly worded title. It has a shot of a MK2 16V on the front I think. A very good book. You should also invest in a fuel pressure gauge for the k-jet system so you can see exactly what changes you have made, rather than changing variables and never being able to go back to where you started.

 

Gavin

[Bora Bora 0]

My C is running on a little bit when turning off the engine.It is also quite juddery when cold until it warms up.

 

I have been told that this something to do with the metering head.

 

I have a Bosch specialist nearby. After phoning them up, I have been quoted £100 to sort out these problems, this will include getting the injectors and metering head cleaned.But not any parts needed.

 

Seems quite pricey? Anybody had the same type of problems or done these jobs themselves?

 

If I am to get this work done by Bosch, I will enquire about mod's mentioned above.

[aide 0]

'how to tune and modify Bosch fuel injection systems' or similarly worded title

 

I've just ordered this off amazon, sees very comprehensive - £12.75 inc P&P.

[corradophil 3]

Price sounds about right, but I was advised not to bother with cleaning the mechanical injectors, by a specialist I apporached to have mine cleaned. I replaced mine with brand new ones from Euro car parts (GSF are similarly priced) for around £120. Took 15 mins to replace all 4 and made a noticable power improvement.

[h100vw 0]

You could take the rightangled elbow off the top of the metering head and make sure it's free from oil residue. If you lift the flap in the middle with a pair of pliers, when you let go it should return to rest smoothly. If it doesn't that could be a cause of the running on.

 

Also you could give it a wipe out with a clean rag. I would squirt WD40 or something similar to thin the oil residue and wipe it out gently. If you lift the flap carefully then you can clean the edges of it and the metering cone.

 

You could check the injectors are firing ok by pulling them out of the manifold, set them to squirt into a jar or bottle. Prime the fuel system by turning the ign on/off a couple of times. The injectors should not be leaking with this pressure behind them.

 

Next lift the flap in the metering head, this will allow fuel to flow thru the injectors. It should come out in a cone shape.

 

CLICK HERE!

 

You need one of these to pull injectors without damaging them.

 

DISCLAIMER :mrgreen:

 

You will know whether you have the ability to carry out the above. If in any doubt please pay someone, rather than torch yourself. Don't come running to me if you break a leg :cry:

 

Gavin

 

*mod edit - Link from hell shortened a bit! - Henny*

[davidwort 0]

At the recent RR day at Star I was speaking to a guy (Dave Mason with the uber Audi) and he mentioned something about shimming the metering head to gain a little power. I have done a search on this forum and managed to find a Kjet manual which has explained a lot.

I realise that if you shim the flap to open further then more fuel will be added to the mixture but I am unsure of exactly where they go and what size shims you need. Can anybody help?

This ,to me, effectively seems to have the same effect as the WUR mod which I have looked at and understand (reducing control pressure etc) or can both mods work in conjunction. I take it the WUR is only really beneficial at high rpm/loads to prevent leaning out. Do these mods drastically effect fuel consumption?

 

Alos can somebody point out exactly where the WUR is.

 

There's a lot of talk about this on the Club GTI Forum as a number of mk2 16v owners have modified and 2.0L 16v's running K-jet injection.

Best bet is to have your car set up properly on a rolling road by someone who knows the K-jet system well, as mentioned you only really need to start modifying the injection system if you wan't to supply fuel to get the most out of modified cylinder heads and non-standard cams etc.

K-jets do like to be set up a little richer than spec though, about 2% CO at idle (by adjusting the idle mixture screw on the metering head) and possibly a bit richer via the warm up regulator, you can do this all yourself, but at the very least get your CO checked by an MOT station and make sure your plugs aren't fouling by over fuelling. If you do the WUR, only use fractions of a turn, as 1/4 of a turn can put your engine over the 3% CO allowed at MOT time and may loose you power.

If done properly it doesn't use a noticeabl;e amount of extra fuel.

 

David.

[flusted 0]

My C is running on a little bit when turning off the engine.It is also quite juddery when cold until it warms up.

 

I have been told that this something to do with the metering head.

 

I have a Bosch specialist nearby. After phoning them up, I have been quoted £100 to sort out these problems, this will include getting the injectors and metering head cleaned.But not any parts needed.

 

Seems quite pricey? Anybody had the same type of problems or done these jobs themselves?

 

If I am to get this work done by Bosch, I will enquire about mod's mentioned above.

 

A hour on the rollers would be cheaper and you would get a before and after power graph. I drove 150miles to stealth just for this and it was well worth it,i gain 42bhp :lol:

[Bora Bora 0]

Thanks for the advice fella's.

 

Can anybody recommend somewhere within 100 mile of Hartlepool, that has "rollers" and a good knowledge of K-Jet systems???