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9A Fuelling adjustment...

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9A Fuelling adjustment...

Post by mrbeige on Fri Apr 03, 2009 4:35 am

Right, quick question. With respect to my old 9A Corrado, how would you go about increasing the fuel delivery in line with a ported/polished head and KR cams? Does the WUR mod normally associated with the KR still apply? I would expect not... Question

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Re: 9A Fuelling adjustment...

Post by JNLRacing on Fri Apr 03, 2009 5:16 am

Depends on what the head flows really. Also I'm not a fan of the WUR mod. I wen't about it a different way that I learned from an Audi 10v Turbo man.

If you look carefully at your distribution block next to all the fuel lines there is a tiny little 3mm allen key. If you undo these you can adjust the fueling to each individual injector. After 100K miles+ that they have all seen you'll find not each injector flows the same anymore.

So what we used to do is unscrew all the covers to gain access to the 3mm grub adjustment screw inside. Then put a co meter into the tailpipe of the car and at idle first we adjust the car to perfect 1 lambda using the main control screw.

We then switched the engine of and used a colourtune tuning kit where you can see the colour of the flame through an inspection hole on cylinder number 1. Depending on the colour of the flame we would then turn the grub screw of injector one up or down until the colour was right. This process was then repeated for the other cylinders. So they where all showing the right colour.

Replacing the safety caps afterwards. Once that was done we'd shim up the fuel pressure return to increase the fuel pressure to the injectors and adjust the co idle screw to bring her back to perfect lambda at idle.

That was enough to support upto 280hp on a turbo'd 10v without any other changes allowing the WUR to correctly fuel throughoutthe rev range instead of being locked out for the top end only.

Never tried it on a KR but I would expect it have a similar effect and well worth a go as a first port of call for the DIY enthusiast.

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Re: 9A Fuelling adjustment...

Post by Flusted on Mon Apr 06, 2009 7:31 am

you dont have a WUR on 9a! you can adjust it with a multi meter, there was a how to guide on web somehwere
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Re: 9A Fuelling adjustment...

Post by mrbeige on Mon Apr 06, 2009 11:46 am

JNLRacing wrote:If you look carefully at your distribution block next to all the fuel lines there is a tiny little 3mm allen key. If you undo these you can adjust the fueling to each individual injector. After 100K miles+ that they have all seen you'll find not each injector flows the same anymore.

So what we used to do is unscrew all the covers to gain access to the 3mm grub adjustment screw inside. Then put a co meter into the tailpipe of the car and at idle first we adjust the car to perfect 1 lambda using the main control screw.

We then switched the engine of and used a colourtune tuning kit where you can see the colour of the flame through an inspection hole on cylinder number 1. Depending on the colour of the flame we would then turn the grub screw of injector one up or down until the colour was right. This process was then repeated for the other cylinders. So they where all showing the right colour.

Replacing the safety caps afterwards. Once that was done we'd shim up the fuel pressure return to increase the fuel pressure to the injectors and adjust the co idle screw to bring her back to perfect lambda at idle.

That was enough to support upto 280hp on a turbo'd 10v without any other changes allowing the WUR to correctly fuel throughoutthe rev range instead of being locked out for the top end only.

Never tried it on a KR but I would expect it have a similar effect and well worth a go as a first port of call for the DIY enthusiast.
That sounds like a much better solution than the WUR mod. So two questions

1) What the chuff is a colourtune tuning kit
2) Where are these inspection holes on the engine?
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Flusted wrote:you dont have a WUR on 9a! you can adjust it with a multi meter, there was a how to guide on web somehwere
This isn't really for me. I have a mate who has a 9A and he wants my old head with the KR cams and was wondering if there was a means to adjust the fuelling. From what I've read the WUR mod, although a more simple option, it can lead to thinning of the oil and thus main bearing failure if you don't get it right Smile

I'll have a look for it anyway. Smile

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Re: 9A Fuelling adjustment...

Post by davidwort on Mon Apr 06, 2009 1:59 pm

the 9A can be remapped I believe, as the ECU controls both ignition and fuelling as it uses an electronic differential pressure regulator (on side of metering head) instead of the mechanical WUR, no idea if anywhere would still be able to actually do the job though or if it's any better or worse than tweaking the WUR on a plain k-jet, in theory you could affect enrichment at different revs, unlike the WUR mod on plain k-jet.
My modded WUR does a really good job with the flowed head, although it does run a little on the rich side, but I can get away with that on plain K-jet as there's no CAT or lambda to bugger up with unburnt fuel.
One of the great things about the K-jet is it's pretty tolerant of engine mods, yes you will run leaner at the top end with a flowed head but K-jet tends to do that anyway.
It's really the shape of the metering head cone that is the basic 'map' though so pretty much anything else you do to K-jet or KE-jet is going to affect the whole rev range as it's pretty crude.
I'd imagine the only danger of upping the mixture by guesswork alone is as you say, getting fuel in the oil, but it would be churning out heaps of black smoke I'd have thought.
The allen caps on the metering head only balance the flow of fuel to the four injectors, so I'd have thought only shimming the main pressure up would affect total fuel delivery.
What I did find was that a rolling road setup gained me nearly 10bhp even though the car was running very well when it went in, good CO at idle, good power, economy and not running hot.
A few people have just whacked in a KR inlet cam and a flowed head on a 9A with KE-jet with good results, so I'd just do that and see how it runs, plug colour will give you plenty of idea if it's running too lean or rich.

I keep thinking Megasquirt and wideband mine, but TBH it runs so well and reliably on K-jet I'm loathed to cause myself problems!

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Re: 9A Fuelling adjustment...

Post by dirtytorque on Mon Apr 06, 2009 2:08 pm

does k-jet use a knock sensor aswell?
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Re: 9A Fuelling adjustment...

Post by davidwort on Mon Apr 06, 2009 2:13 pm

not the KR engine 1.8 16v plain k-jet, only the 6a/9a engines running KE jet have knock sensors

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Re: 9A Fuelling adjustment...

Post by boost panda on Mon Apr 06, 2009 3:56 pm

yeah, KRs are pretty old school! There's a few bosch books that cover their tuning and maintenance etc.
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Re: 9A Fuelling adjustment...

Post by JNLRacing on Mon Apr 06, 2009 4:06 pm

^^^^ davidwort like you say the allen caps only balance the injectors the point being until the system is balanced you dont want to be doing anything else to it. Once balanced you up the fuel pressure and turn down the co adjustment screw to compensate overfueling at idle. If co is set correctly at idle it will then automatically set itself through the design of the cone. As a rule of thumb I would go up 15thou at a time and see how the car runs do WOT pass at kill the ignition whilst on WOT at 6000rpm. Coast to a halt and check the colour of the plugs. I did a very similar process to a carb'd v8 with an adjustable secondary vacuum and adjustable jets. Tuned the car on the road like that with plug reading to go and do 11.5 and 11.6 sec passes. Tedious but the results make it all the worthwhile.

As for running rich on kjet not being a problem because no cat or lambda is a dangerous one. The number 1 reason for KR's coming into the workshop for a rebuild is a spun big end due to overfueling. As you run rich it mix's with the oil. Fuel being an abrasive designed to strip carbon deposits of your valves will then subsequently be wearing away at your bearings.

I've seen ones so badly overfueling that with less than 3000 miles on the clock the thrust washers are practically disintegrated from town driving as the fuel also makes your rings and bearings brittle. Which is also a primary reason for piston slap on some of these engines as the rings wear thinner wobbling about in their grooves.

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Re: 9A Fuelling adjustment...

Post by davidwort on Tue Apr 07, 2009 1:17 am

oh, yep, I wasn't suggesting it ran that rich, just that K-jets tend to run a bit better slightly richer than specs. I always keep a close eye on plug colour for the health of my engine and I guess it's about time I had it on the rollers again just to check everything is spot on, it runs with a lot of base advance ~8 deg I'm guessing the P&P head helps with that.

One thing I've never got my head around (I'm not an engineer by any stretch of the imagination, just an reasonably enthusiastic DIY bodger Smile )
is the relationship between the control pressure (WUR altered) and the system pressure and fuel delivery.
The way I sort of understand it, is the WUR reduces control pressure so the metering flap moves further?/more easily? so more fuel gets delivered through the slits in the metering head.
So why is the WUR mod any different to increasing the system pressure? - isn't it just different sides of the balancing act?

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Re: 9A Fuelling adjustment...

Post by JNLRacing on Tue Apr 07, 2009 1:23 am

If you can imagine the WUR is a pressure control valve that is controlled by a bimetallic strip. Temperature/voltage control the amount of pressure it provides. Giving additional pressure on cold start. Once the engine is warm fueling is reduced. Unbolting it from the block means it never gets to temp and carries on delivering excess fuel pressure.
All the WUR mod is making this a mechanically adjusted device so it only has specific predetermined pressure settings. This means inadvertantly if you got it fueling right at the top end it is bogging down the lower end of the rev range and visa versa.
Changing fuel pressure at the return valve doesn't effect the factory operation of the WUR.

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Re: 9A Fuelling adjustment...

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