failed emissions, need some weber jet advice (lehiguy?) (1 Viewer)

Joined
Feb 10, 2011
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Fort Collins, CO
Hey all,
So she failed pretty bad, nearly three times the limit on CO, and was getting close to the HC limit. Colorado does a "complete driving range" test so I dont know exactly how it was doing at idle vs load. But they do show you a graph and CO is through the roof under acceleration, and levels out but still over the limit when at a cruising speed. HC spikes while shifting.

So right now my jets are 45 idle, 140 main, 190 air. I'm thinking of buying a set of 35's and 40's to try on the idles, and going to 135 on the mains. Not sure if I should mess with the airs.

Honestly this is a big surprise... She drives great, gets 16 on the highway, exhaust maybe smells a tiny bit but not like "damn that thing's rich!" Doesn't always like a warm start so also a rich problem maybe?

Anyway I'm hoping to avoid spending 100 bucks on jets if I can...

Thoughts?
Lehiguy you there?

Thanks in advance for any advice!!

-Andy
 

2mbb

SILVER Star
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have you gone through the emissions manual and made sure that all the systems are working properly? High altitude compensation? Air injection?

Do you have any numbers to post up, especially residual O2?
 
Joined
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heh heh- none of the OEM systems are even present, I'll wager.

And yeah, my WAG is that you're headed the right direction. One jet will make a big
change in mixture. If you end up with a carb that goes lean as you wind it out,
then making the air correctors smaller will richen it back up.

The spikes- that's problemmatic. I always see them too, and haven't found a way to change them much.

hth

t
 
Joined
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Fort Collins, CO
Yeah none of the oem stuff is there. Well, the air pump and egr are there but just to pass visual. I should be able to get this through without it them working.

On closer inspection of the graphs the spikes are on acceleration, and my levels seem to be good and low during idle and significantly dropping during shifting. This leads me to think my idle jets are good, and I sort of tested that by leaning out the mixture screws which made my idle nearly die. So not rich at idlemaybe even lean with the 45's in there.

I think a step or two down on the mains and maybe a step up on the airs is in order. (Should I mess with the airs?)

I wish there was a way to know for sure but it seems to be trial and error. I suppose I can look at the plugs after going wide open throttle. Not sure how reliable that is.

No residual o2 number given. My smog pump is gutted so there isn't any.air going in there anyway. My cat is probably dead too, but that stuff really just masks problems. I want this thing running perfect and not polluting.
 
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Yeah none of the oem stuff is there. My smog pump is gutted so there isn't any.air going in there anyway. My cat is probably dead too, but that stuff really just masks problems.
That is focking hilarious. If your pump worked, and you got a generic cat from Summit for 60 bucks it would smell better and pass with ease. If you had to go one step down... :meh:

I want this thing running perfect and not polluting.
:clap:
 
Joined
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Washington, UT. The Promised Land
 
 
You should be able to pass with a funcioning cat. If NOX is low and CO is high, try more ignition advance. That will lower CO at the cost of a rise in NOX but it sounds like you can afford it. If you are running one of those dumb little square air cleaners that come with the Weber, get rid of it. They are too small and restrict air flow to the point that it is a very noticable difference when you remove it. Make sure your vaccum advance and mechanical advance are both working. Make sure the vacuum advance on the distributor holds vacuum and is plumbed to a ported vacuum signal on the Weber. The HC spike when shifting is due to the sudden closing of the throttle plate that essentially starves the engine for sufficient air to completely burn the fuel already in the intake. If you are the guy at the helm when all this takes place (????) close the throttle slowly and don't let it close all the way in between gears.
 
Joined
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Fort Collins, CO
Well no I dont get to drive while all this happens. How do I test the advance? The port (I'm using the inner one only) holds vacuum.

I think I will advance the timing a bit, and go with 135 on the main jet and see where that puts me. I see quite a few guys running that size at this elevation.

Just did the baseline idle stuff on the weber and with 50's in there my mix screws are a half turn richer than the range they recommend. So according to them I should have 55's in there.

I'm going to go through one more time and if it fails I'll replace the cat.
 
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But thinking more on this a cat won't do anything for CO levels will it. I'm sure HC will come down as I get my mixture straightened out.
 
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The Weber reccomendations and what actually works on a Cruiser will be different. Its a motor with a low VE and has its own character and fuel needs. The idle jets are going to make the biggest difference. 50s for your elevation are too much. Some extra ignition adavance should help. The mechanical advance is checked by simply twisting the rotor; it should move freely and return to its original position.
 
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Fort Collins, CO
So are you saying webers way of getting lean best idle is wrong? Honestly off-idle my truck is great. Plenty of power down low and I see no reason (from a driveability standpoint) to up my idle jet size.
 
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So are you saying webers way of getting lean best idle is wrong? Honestly off-idle my truck is great. Plenty of power down low and I see no reason (from a driveability standpoint) to up my idle jet size.
Don't increase it, if anything, decrease it since your smog test results are what they are. Here is a quick rule of thumb for mixture; if it will run well when cold with the choke disabled, you are too rich. Webers can give you the sensation that all is well even when they are, in fact, too rich.
 
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Fort Collins, CO
Well it doesn't run well cold with choke disabled. I had the idle set around 650-700, and when I screwed in the mixture screws a turn, from 2.25 out to 1.25 out, the truck wouldn't idle, so I don't think I should go smaller than 45.

Timing right now is a degree or two past 7 in the advance direction, I'll go a bit further.

But according to the graph they gave me showing speed versus various pollutant output, when the truck is idling its very clean. Acceleration is horrible though. I know idle jets are in play throughout the driving range. Wish I could test various jets on emissions without paying for it. Haha
 
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Nelson, BC
 
 
Is your float level within spec? If it is too high, it will run rich.

If float level is fine and the needle valve is good, I would go to smaller mains. Yes the idle jets are delivering fuel throughout the throttle range, but your mains start functioning as soon as you open the throttle plate.

Also, adjust the mixture leaner than best idle for the test. As long as it doesn't start to miss, it will help.

Good luck.
 
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Cool that's what I was thinking. I'm gonna stick with 45 isles and lean it out as far as it'll go and hold a 700 rpm idle.

I think my float is good, I checked it a while back, not sure of the exact technique or measurement for the 38. I found somethin online a while back but it wasn't official. No driveability issues so I'm guessing its close. Do you know how to set float on these? Needle valve is new.
 
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Hey, I see what you might be missing-
the 'idle' jet feeds the idle screw, but it's not much of a restrictor.
If you go rich as you transition from idle to load, that's more of what the 'idle' jets themselves meter.
All of the little holes in the body get their supply from that circuit. They're really 'transition' jets.

I'd certainly try to get them smaller for smog purposes. Might not run as well, but running well and smog... don't always agree.

Don't spend money on air correctors until the mains are right- they're totally dependant
on main jetting, so you need to get that right first.

Grr- can't find my Haynes Weber book- it has the 38 float info.

t
 
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Ok, found Haynes-

38 DGAS brass float- closed 40mm, open 50mm stroke 10mm
38 DGAS plastic float closed 34.3mm, open 44.3mm, stroke 10mm.

Check it from the edge of the lid (no gasket) to the lowest part of the float.

For the 32/36, they give 39mm closed, 11mm stroke (so 50mm open) if that helps anyone else.

t
 
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Well, failed again but I was much closer. I leaned out my mixture screws a half turn, went to 135 mains, and advanced timing a bit.

I think the plan now is to drop in the 200 airs, lean out another half turn, and advance timing until right before it pings. I was at kit under a third of allowable NOx so I think I have room to play here.

Doing this right now unless someone catches me in the next hour with a better idea!
 
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Well, failed again but I was much closer. I leaned out my mixture screws a half turn, went to 135 mains, and advanced timing a bit.

I think the plan now is to drop in the 200 airs, lean out another half turn, and advance timing until right before it pings. I was at kit under a third of allowable NOx so I think I have room to play here.

Doing this right now unless someone catches me in the next hour with a better idea!
Keep up the heat to burn all the fuel. As I said, you can essentially trade NOX for HCO by going leaner and/or more ignition advance which makes it burn hotter raising NOX but lowering HC. If I ever had an issue, it was high NOX. I would plug my vacuum advance prior to testing. You have the opposite problem.
 

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