rb968
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| posted on 12/4/11 at 10:21 AM |
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Help needed setting up ZX9 carbs for IVA
First of all apologies for posting this again but I really need some advice. I had posted in the IVA section about emissions.
Linky
As you can see below the results of my first pass at emissions with the current setup was some way off the mark so I need some advice particularly
from anyone who has got a post 95 bike engine on carbs through the IVA emissions test.
As stated in the other thread the carbs are marked as having been modded which I am assuming means bigger jets but need to check. I understand the
pilot screws allow me to adjust the mixture and I have already set these to the default factory settings in the Haynes Manual of 1.5 turns. The tester
at the garage said it was as if the cat wasn't there so do we think I need to lean the mixture and get the cat a lot hotter?
Any advice on how you got down to the limits would be great as I am struggling to know where to start.
Cheers
Rich
Idle
 
Emissions Idle results
Fast Idle
 
Emissions Fast idle Results
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cliftyhanger
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| posted on 12/4/11 at 10:32 AM |
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Hmm, I am no expert, but looks like the carbs are running miles too rich, and overcoming the CAT. I assume the cat was nice and hot etc before the
test? But also it may take a while to burn the excess fuel off it as well.
I suspect the carbs need a proper setup on a rolling road, but the cat would complicate it. Maybe they take the cat off to set them up?
Beware just leaning th ecarbs right down to pass, as it could cause engine meltdown if it goes superlean at high rpm. Hence the need for a rolling
road, or at least a AFR meter and wideband lambda sensor.
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coyoteboy
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| posted on 12/4/11 at 11:00 AM |
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You're running super lean. First test was at ~18:1, surprised it was even running at that point. Either that, or you have an air leak in the
exhaust. Even on the second attempt it was at ~16:1 which is fairly lean. A guess would be that your fairly high HC is from lean misfires too.
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mistergrumpy
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| posted on 12/4/11 at 11:08 AM |
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I've got my 98 ZX9 through SVA. You said that your carbs are marked as being modified. What marking is this? I think that you have to strip them
and have a look for yourself at the jet sizes and needles first. I can explain how to do this if needs be and I've a few saved threads on ZX9
carbs that I could point you towards. You need to know which way to turn the adjustment screw too to make it rich or lean, I remember that what I
thought was rich was actually lean. I'll have to have a dig around on here so that I remember myself though, I do remember commenting on it once
after the SVA.
ETA screwing the mixture screw in leans the mixture out if that helps.
[Edited on 12/4/11 by mistergrumpy]
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rb968
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| posted on 12/4/11 at 11:27 AM |
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Thanks for the comments.
Forgive my ignorance I now realise (having spent 5 mins understanding AFR) that I am over the 1.00 Lambda or 14.7:1 AFR and so am lean. I am surprised
as I assumed the high readings meant too much fuel therefore too much CO/HC.
An air leak is a possibility. I have done my best to seal it but possible it leaks a bit around the 4-2-1 section as this is a push fit. Exhaust is a
bit if a make do from a manifold that came with the engine to the original owner from ZCars. I will have another go at that.
I will look at the markings on the carbs tonight. PRP in Lincoln for ZCars it has engraved (badly) on one end . I seem to recall it may state the jets
size but will look again.
I do want to get it setup properly but was hoping to do that post IVA. If needs be it will have to go somewhere before but would like to sort it
ourselves. My dad and I have stripped the carbs previously to clean (dad was a mechanic all his life but not familiar with bike carbs)
At what point do the main jets come into effect? I understood at idle the pilot jets (with the butterflies closed) provided the fuel and hence why I
reset these to the factory setting.
Is it best to set up the carbs without the cat on there first then introduce it to scrub the gases for the test?
Cheers
Rich
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mistergrumpy
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| posted on 12/4/11 at 11:39 AM |
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I have to nip out so will add more later if I can but you need to do your best to seal that exhaust, mine leaked and threw the reading right out. You
need to set it up with the cat on too. No point doing it without as it needs to be right for IVA. Just to add the carbs may have been tinkered with
before but combine a different exhaust or airbox and it@ll throw the fuelling out again. Just as a start, mine have 136 jets in.
I found this write up by Si moto helped me understand things a lot.
[Edited on 12/4/11 by mistergrumpy]
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coyoteboy
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| posted on 12/4/11 at 11:46 AM |
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Always best to have the CAT out of the way while tuning, to get yoru best tune, then improve on that, IMO.
Wideband lambda is the best £130 I ever spent on my car.
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mistergrumpy
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| posted on 12/4/11 at 01:03 PM |
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Why would you want to set it up without the cat? Its a long process anyway doing it at home with lots of tweeking and fettling. To get it right then
have to redo it after adding the cat into the system would be a real pain in the backside. Do the job once is what I say.
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40inches
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| posted on 12/4/11 at 01:13 PM |
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quote:
Originally posted by mistergrumpy
Why would you want to set it up without the cat? Its a long process anyway doing it at home with lots of tweeking and fettling. To get it right then
have to redo it after adding the cat into the system would be a real pain in the backside. Do the job once is what I say.
Very true. I set mine up without the cat, then when I fitted the cat had I to do it all again, way out!
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cliftyhanger
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| posted on 12/4/11 at 01:23 PM |
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My thoughts about doing it without the cat is that it removes CO and HC from the exhaust, so at a rolling road where do they stick the sensor??
If using an AFR meter then I guess it just screws into the bung in the manifold, assuming there is one.
And air leaks cause massive problems with lambda readings. Really needs to be really well sorted, even if it won't last very long. High temp
silicone sealants? I think there is one available for exhausts.
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rb968
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| posted on 12/4/11 at 01:49 PM |
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Thanks everyone.
Mistergrumpy have printed that thread for a read later ! Look very useful and I am beginning to get my head around it.
So I guess I need to find out
1. main jet sizes
2. needle position
and see where we are after that. Hopefully should be able to get back to the garage to retest when I need to. First go was just to see where it stood.
It idles Ok and seems to run pretty well. No misfired or stuttering on the pretty short runs I have done so far.
I will be back with more questions but main priority is to get it right to pass IVA then remove the cat and either tinker further or bite the bullet
and get someone to tune it properly.
Cheers for now.
Rich
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rb968
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| posted on 12/4/11 at 06:53 PM |
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Quick question for anyone still reading this ;-)
Are the 4-2-1 collectors usually just a push fit onto the pipes from the manifold? They are on mine hence perhaps an issue with the leaks I suspect I
have.
Thinking of a way to clamp all 4 branches into the collector to seal them better. Welding in position will be tricky as you won't be able to get
into the centres of the four?
Mmm just wondering are most peoples welded up if so how do you remove the exhaust?
Want to get this sorted before arsing about with carbs.
Rich
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40inches
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| posted on 12/4/11 at 06:56 PM |
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Use exhaust sealant, smear it around the pipes before you assemble them into the collector, make sure you use Cat friendly sealant.
Silicon is better SILICONE SEALANT AUTO EXHAUST CAT SAFE ASSEMBLE PASTE | eBay UK is the best sort.
[Edited on 12-4-11 by 40inches]
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