Looking for some advice on things to check,

Just failed SVA on emissions on a pre 95 engine

It's running beautifully, no smoke, idles clean and all pipes warm equally..


Left Exhaust:
CO 0.22% HC 1608
Right Exhaust:
CO 0.39% HC 2951

Limits:
CO 3.5% HC 1200


Any ideas what I should be looking at here? There are no running problems with the thing whatsoever...

James

It's running too rich, hence the unburnt fuel in the exhaust.

running weak will cause high HC,just richen it up a bit

Look at the CO figures, it's running too weak! The hydrocarbons will drop if it's richened up. As to whether or not it will reduce them enough? the only way is to adjust it and recheck. If HC is still too high there is a problem with the engine/ignition . There should be some other figures , post them up.

Thats that only two figures measured on the non CAT test...

The tester thought it was too lean too....

Trouble is without a gas tester I have no way to tune it...


Do I need to be twiddling the idle screws mixture screws?

James

[Edited on 25/3/09 by cloudy]

This document is good:

http://www.autoshop101.com/forms/h56.pdf

I've learnt something today!

That graph is pure gold - thanks! Would estimate AFR up at 22!

Could I tune it by welding in mounts for ox sensors in the headers and then using an AFR guage to get it right?

James

Could you have an air leak on the inlet manifold?

What engine is it? Carbs?

carbs on a gsxr 1100wp, definately no intake leaks, replaced the carb rubbers a while back...

James

Yep defo too weak. There should be some idle mixture adjustment screws on the carbs. Probably underneath, and possibly under some covers. Unscrew them 0.25 of a turn and have another go. The SVA man might let you twiddle with them on the machine once you know where they are and how to adjust it.

The other option is speak to a local garage and see if they will let you borrow their gastester for 30mins (you will need to book it in for an 'MOT' to be legally allowed to drive it there though).

David

A colortune is quite helpful here. I've got a bike one for a ST1100 (10mm). Feel free to borrow it if you want. Very useful in my experience for setting up the idle mixture....

[Edited on 25/3/09 by BenB]

That might be handy - I'm on the lookout for an AFR gauge - but it means welding in bungs in all the exhaust headers...

Whereabouts are you? Could I paypal some money for you to post?

James

I'm in London (NW6). End of the M1....
I can post it, but it'll probably be the weekend before I get to the garage so you'ld have it middle of next week???

My neighbours just told me he has a 2 gas analyser and a colourtune!

job done!

Are the carbs set up for the better exhuast and air filter? I had this with my first engine. Was told it had been set up right by the previous owner, only to find at MOT time that it was running lean. With the new engines and carbs it was rich with a stock air filter. Removed it and the emissions dropped straight into the green on the MOT computer. The new stuff had been set to run with a decent filter and exhaust, the old stuff hadn't.

stock air box, and the exhaust is more restrictive if anything....



James

another thought, are the carbs balanced spot on? They are weak, but poor balance can wack the HC right up. Ans a pipe in the ear is probably not accurate enough...though if miles out should help get into the right ballpark.

Have reset the idle screws using a colourtune and 2 gas analyser...

They were slightly off book settings, and came good around the book setting...

The left side moved to about 2% CO and 1400 ish HC's a little tweaking got it down to 880HC's - a pass. The right hand side I can't get close - managed about 1400HC absolute best...

Ignition is dyna 2000, dyna coils, dyna leads, new iridium plugs, all plugs correct colour, no carbon or oil, engine idles and runs perfectly. I'm at a complete loss - it shouldn't be this hard right?

James

If the engine has adjustable tappets , shim or otherwise, test for tight tappet clearance. Also check plugs, leads etc and if you have a compression tester check compressions. A cylinder that is not running correctly may not show up as a misfire but will show up as increased hydrocarbons.

I will balance the carbs tomorrow, I dont have access to a compression tester, so i'll have to try and buy one (won't be in time)

I did check the timing (I can time the two pairs seperately and 2 and 3 were about 3 degrees out which can't help)

Will balance carbs then try again tomorrow, I don't think i'm going to be able to do it... Sods law says even if I scrape it through at home it'll be high at SVA

James

Offer of a compression tester also stands

Thanks ben, i'll see how I get on today and give you a shout, I think if I can't sort emissions today i'll have to cancel SVA on tuesday anyway as it could be serious engine work...


James

A good balance has got them down to 2%CO and hovering between 1200 and 1500 both sides now... Still not close enough

Cam cover off and all the valve clearances are bang on the middle of the the tolerance - can I take you up on the comp tester offer ben?

Closer, got it to 3% CO and 1100 HC, but ONLY when the headlights are on!! about 1250 without....

If I drop the idle revs to match the loaded state, HC's stay high...

Hopefully SVA man lets me leave the lights on for the test, but anyone got any ideas what that might suggest as the problem?

James

Found an intake leak on 2 and 3, but i'm not sure it's going to make a great deal of difference (after all 2 is part of the left pair which is giving an OK reading)

I have a dyna2000 ignition which I believe runs 4 degrees advance over stock (40) at idle... Would it be worth pulling this back to zero?

James

[Edited on 28/3/09 by cloudy]

Idle advance should be more than that I would have though. More like 8-10 deg?

I've just read the manual - dyna2000 runs 15 degrees at idle, ramping it up as you approach 2000 rpm to the full 40 degrees...

james

If there's a leak in 2 and 3 then maybe fixing that will bring both sides down.

Hmmm..
At my SVA at Exeter last month, the examiner tested for HC's at nearer 2000rpm.
He explained that as a bike engine has no fly wheel, it relies on a relatively rich mixture (and higher revs) at idle to ensure the engine runs smoothly. This can lead to higher HC's and so he increased the revs slightly to see if the HC's significantly dropped (which they did).
He was happy that the bike engine was behaving as it had been designed to do and gave it a pass. Mind you, Byron at Exeter is a very reasonable guy.)

What were your various readings? (and at what rpms)

I give up with the bloody car, still no better - got right hand side down to 400 went to tweak the left and got it to 900 came back to the left and it was at 2200 !!

No idea what to do now, I can't afford to take it to a tuning company, and I feel its a waste as it's on the SVA exhausts...

James

Just dug out the emissions slip from the test. Unfortunately all it states is that at idle speed CO was 1.42 and HC was 413. Which was a pass on both counts. (pre-95 blade engine and so within parameters of CO 3.5% max and 1200 HC)
However, I do recall HC's being much nearer the 1200 limit at true idle (approx 1100 rpm,) so I think he's just used 2000rpm as the idle speed for purposes of the test!
Have you tried taking a HC reading at 2000 rpm to see if it significantly drops?

[Edited on 29/3/09 by andrew.carwithen]

If i raise the idle to 2000 the HC's go through the roof to 2000 so that's not even an option...


I wouldn't definately say as the engine warms up it gets worse, at 50-80 degrees water temp its fine, but as it seeks about 90-100 on fan its high....

James

[Edited on 29/3/09 by cloudy]

Just a few thoughts and probably 'teaching granny to suck eggs' so bear with me....
When you balanced the carbs, did you have to remove a blanking plug/screw from each carb in turn first to enable you to attach the carb balancer? (and replaced them afterwards, obviously!)
Just thinking if they were possibly missing, then you'd be sucking in air and consequently running lean..
I don't know how the Suzuki carbs compare to 'blade in terms of setting up, but on the blade, one of the carbs has a spigot which is blanked off with a removeable cap and the other three have blanking screws.
The carb with the spigot is the datum carb and the other three carbs are balanced to this one. Once set, then idle speed is re-set using the adjuster under the carbs.
Have you had the carbs apart, at all?
Are float heights all ok? Are the jets and needles of uniform size and set correctly?
I'm assuming the carbs are of the CV type and hence are the diaphragms in the carb tops all serviceable/not split etc?

I HATE IT I HATE IT I HATE IT

Wish I hadn't started, another few hours out there and nothing to show but burnt hands and even worse results

I really am at a loss now, I can't afford a new engine and I can't find any problems with this one I don't even have anything left to try.

Yes all replaced, the problem is nothing stays equal, you can fiddle and get it right at 400-900 and then the next reading is 3000 there's no rhyme or reason to it...

Can you afford to get it stripped and rebuilt?

YEEEEESSSSS


Swapped out the coil packs and managed to get a stable 1000 on the right and 400 on the left - but only when the lights are on!

It'll be pure luck if it goes through the SVA....

James

Well just tested again in case it was a fluke, and still getting 1000-1200 each side from lukewarm. I'm really hoping a good blat to SVA will give me a little bit to play with... It's all so up and down I wouldn't be surprised if I get there and its 3000 again though

James

This is why I'm thinking of stripping it down, or at least all the parts that would affect the figures. That way you can put them all back together and make sure they're working properly.

There are only 3 things left really,

It must be being brought up artifically, i've defintately got it to the "sweet" spot CO about 2 - 2.5% both sides which I think is about right..

That leaves

Leaking valve stems
leaking/burnt exhaust seats
Oil+Piston Rings


All three are beyond my current skill level ,budget and time but if I can't get it through on tuesday i'll have to start looking into it...


Kames