High CO emissions on S2

[KenS]

Seeking advice - the car is an S2, closed loop, 1499 ID prom, 2.25 piper exhaust (7year+) originally with sports cat (marked - not for road use). Always has been touch and go to get through CO emissions. Last year I welded in a 2" M100 aftermarket cat and fitted new injectors to help it get through - but is still only just got in. This year I have replaced the o2 sensor (Bosch), general service, new thermostat, washed out the K&N air filter, fitted new fuel regulator (PR92) - but it failed. Copy or results:

results.jpg

The garage advise that it needs a new/better cat, since cheap after market cats only last a year or two.
Quandary now is if to buy another Piper sports cat, or buy another but better after market 2.25" cat and weld it in - and if this will be a robust solution, or could there be some other reason for high CO emissions?
Looks from ebay ads that cracks in the exhaust manifold are very common, could a small crack cause the MOT fails? Would such a crack be obvious with sound under the bonnet? (I don't have any noticeable sound of blowing).


I did run elanscan, while sitting on the drive but I cannot see anything obviously bad like a sensor, - tried to add listing but failed!
Do other S2 owners have problems with CO emissions with or without cats?
Do I need a 200 / 300 / 400 cspi cat to have no more problems?
Any thoughts appreciated

[KenS]

Found how to add the Elanscan file (by zipping it)

[GeoffSmith]

There is nothing obvious in the ES data and your figures are similar to mine (although CO is higher and I have no cats). The following is merely a summary of my observations which you may or may not find useful:

The garage (or their test equipment) have obviously looked up the emissions limits in the emissions book. The only entry is for: Type 100 Elan S2 from VIN No SCC100ZT1RHA26001 Engine Type ZT1, Engine VIN Code ZT1 and the procedure requires that they find an exact match. As the engine code is quoted in the emissions book, the tester should confirm that the engine is type ZT1 but this can be problematic because a) they are not allowed to move or clean anything and b) the engine doesn't appear to have a code marked on it. If they confirm an exact match then they test with the limits quoted. If they don't find an exact match then they should carry out a non CAT test with limits of 3.5% for CO and 1200ppm for HC. They may not follow the latter path because a) it's quicker and easier not to, b) some automatic exhaust gas analysers do not have an option to select 'engine not listed' if there is only one engine option and c) the engine type is included in the vehicle VIN and in the text of the procedure, the onus is on the owner to prove that a different engine is fitted.

[Saltire]

Here are the results from my S2; standard turbo and exhaust with cat. First from 2018:
forum.lotuselancentral.com/viewtopic.php?f=21&t=25947&start=80#p341134

And 2019:
forum.lotuselancentral.com/viewtopic.php?f=21&t=25947&start=140#p350801

And finally 2020:

D266DF53-A675-4C9D-9483-601E847DD6D3.jpeg

[Simon_P]

I just checked and the blue car which has a pre-cat but no main cat had a similar pass to Jonathan's.

The Green car has a 2.25 Piper with sports cat. Never failed on emissions, but I have been asked by the tester to take it for a drive to make sure the engine is really hot. the fuel was at least a year old and the test station was local.

Looking at your scan at 1116 seconds and comparing to a similar scan (in brackets)
Check for vac leaks IAC should be 20 at idle yours is 17
Injector pulse width 1.6 ms (1.3ms)
Injector duty cycle 1.3 (1.00)
So your car is fueling more than mine.

Exhaust leaks are difficult - usually if there is a leak it sucks in air and the oxygen throws the lambda out.

Thoughts:
When was the last time you took it for a good drive? The Cat needs to be up to temperature to work... Drive it like you stole it!
Get it really hot (fans cycling ) when they do the test.
How old is the fuel?
Check the base timing and idle - IAC is 17 which indicates a small vac leak - See wiki.
Have you reset the ECU after the component changes?

[GeoffSmith]

Engine oil temperature check: Temperature gauge showed warm engine

Was it at ½ scale?

[Simon_P]

Engine oil temperature check: Temperature gauge showed warm engine

Was it at ½ scale?

I don't think that there is a stat on the oil cooler so it probably isn't warm unless it the fans are cycling.

[Rambo]

Whether it be an SE or S2, always make sure your engine is hot, hot, hot.

Particularly if you come in and around the 3.5% threshold. My NMY usually runs 3-3.5% and can be problematic whereas the Black Beastie always seems to achieve 0.2% or under

Incidentally, come MOT time, I always top up with 99% RON plus I add a Redex (or similar) conditioner. And I usually add 3 or 4 large bags of coal in the boot. Stops the MOT guy inspecting the spare wheel and helps with any rear brake issues you may have if bordering on the limits

[Simon_P]

Looks from ebay ads that cracks in the exhaust manifold are very common, could a small crack cause the MOT fails? Would such a crack be obvious with sound under the bonnet? (I don't have any noticeable sound of blowing).

Exhaust manifold leaks can sound like tappets. Our manifolds suffer with hairline cracks, they aren't usually that bad, the cast iron rusts and the inside gets coated with soot. A small leak is usually identifiable and is a failure in itself, if it was a problem people would be failing due to defective manifold - Was the ebay observation of a sales pitch or that most were cracked?

[Simon_P]

always make sure your engine is hot, hot, hot.

https://youtu.be/rbc_LxfhSoY

[KenS]

Thanks for all the comment - I tried to cover most things - I did fill with 99 RON fuel the day before the MOT, so probably 70% was new fuel. I ran it hard on a duel carriage way for 4 miles, then the last 1.5 miles to the test station at high revs in lower gears trying to keep it as hot as possible.
I will have a harder look for bad vacuum pipes, I have pulled a vac pipe with the engine running and the revs do increase, but I have replaced some over the last year since they are getting quite hard so there is a chance they are not helping.
Prior to changing the fuel regulator the exhaust on start-up did smell of fuel, maybe that has ruined the cats prematurely. So even if I find a vac pipe issue, I think the easiest immediate solution is a new Piper Sports cat and rapidly get it tested (an try to find its spec to help gauge it against other options incase I am in the same position next year.
Many thanks

[KenS]

The ebay reference about exhaust manifold cracks being common came from an ad for a part with a crack, with the comment "this is normal. In fact, every single I have removed is the same. ". I am not keen on trying to remove my manifold and probably breaking its studs, without knowing if cracks are bad and need fixing. So at the moment I'll leave it alone.

[Simon_P]

Which components have you changed since the last MOT?

My MOT station is about the same distance. If the car has been standing I preceed the drive with 20 mins on tickover, or 10 miles of good road and dual carriageway with an existing MOT..

[KenS]

I have looked over all the vac pipes and they seem OK. But have also checked compression which does not look too good:
Cyl 1 = 162psi
Cyl 2 = 135psi
Cyl 3 = 135psi
Cyl 4 = 170 psi
These are with the engine just warm, just a minute or two at idle to ensure the tappets are quiet and fully pumped up, throttle fully opened and around 5 piston cycles to ensure a peak value.
I ran through them twice, both runs giving very similar values (and I ran a cold test yesterday, those results were about 10-psi lower - around 150,125,125,160).
I guess this difference is enough to warrant removing the head to find what could be leaking between 2 and 3 - hopefully HGF and not a head crack, which is a worry since there is a record in the cars history folder of a possible crack but its not clear what action was taken - but that was over 7 years ago. I have owned the car for over 6 years and it has run fine without engine issues, been to France and Spain covering a reasonable mileage, but every year it is always very close to the MOT CO emission levels, and now failing this year. Knowing these pressures, would this be the obvious cause of the high CO emissions?
- Probably over thinking this - the car always starts first turn when cold or just stopped for up to 30 mins, but if left for more than 30 mins and still warm, it takes 4 or 5 seconds to fire up. I know other cars have this quirk, so I assumed it normal, but wonder if its related.
Since last years MOT (which needed some Tester skill in getting it to pass emissions) I have changed the O2 sensor, the fuel regulator and the CTS, the previous year I changed the injectors and replaced the piper sports cat with a new but cheap after market cat. none of which made a significant difference. During the MOTs they have ensured the fans kick in.
Any comments appreciated before I go and source a new head gasket + bits. Thanks

[Rambo]

Some owners do appear to have this problem of warm cranking Ken (I had it on my Collapso red and it was a minor irritation at times) I believe it is due to the engine being warm and the petrol vapourising in the fuel line

[Simon_P]

Ken, Have you reset the ecu, got the engine really hot, gone for a good duel carriageway drive and then gone for a retest with the fans running?

Compression tests are interesting to prove/add weight to a theory ie burnt valve, blown head gasket, worn rings but you weren't suspecting any of these so not sure how you can conclude anything from the results. Is your car running rough? If it isn't there isn't much wrong. There are further tests to do and then a leakdown test before you can make a diagnosis.

Compression tests start with the engine at normal operating temperature ie when various bits of metal and fluid are in their normal operating condition in the current weather conditions that is about 20 minutes at idle. You won't prove anything with a cold or lukewarm engine - the piston doesn't fit the bore!

There is a chance that you have a leak between cylinders 2 & 3 and an outside chance that this is affecting your emissions (Nothing is impossible) I'd redo the compression test with the engine hot - make a note of the values and then put them in your file for future reference!

[KenS]

Hi Simon, thanks for the comments. Its good news that the pressures are not necessarily unacceptable.
I have been for a retest after disconnecting, waiting and reconnecting the battery, re-checked the timing in service mode (still at 16 deg btdc), added some Cataclean to the fuel and ran it about 8 miles to the MOT station. The fans did not come on during the run but did while they checked emissions. The result on the equipment was around 0.9 and the chap said it still looks the same and probably requires a new cat.
The car runs well, the spark plugs were nice grey when I checked them on the first compression test a few days ago, they were a little sooty after running just a few minutes for the second compression test yesterday, but I think thats expected. It uses very little oil, never needing top up between oil changes. It has 2.25 exhaust, wastegate ported and chip, it has never boosted much above 0.7, but I think that is probably the calibration of the gauge.

I have an upper gasket set A100E6184S on its way from Kelvedon (seems a bargain price £80+VAT especially since it looks like it includes the valve stem seals) so I will have the option to change the head gasket.

I will follow your advise and run the engine up to temp and re-check the compressions.
I will recheck the timing in service mode with an old style neon strobe (provided I can find it) just in-case the one I always use (adjustable xenon) has an offset.
Hopefully have time to do these tomorrow.

Then it will be decision time to either change the head gasket/inspect the head and/or take the chance that a a new cat will fix the problem, either a pre cat (I need to check that the bowl is still there, infront of the piper system) or just a new piper sports cat

[Simon_P]

To put it into context 0.9 is a lot lower than an SE at 3.0 so plugs and valves will be pretty clean. Just not good enough for the MOT.

The Head set is a sensible if you run out of options/ideas its going to be on the list and you get to check things like the EGR valve, lap valves and do the tappets while you are at it. Make sure that the HG has the tab on the end.

Check the idle while you are in service mode and reset the ecu if you make any adjustments.

some thoughts...
Do you know if the starter cat is still in situ or has it been hollowed out? _ just reread your comment.

You mention .7 bar what chip do you have normal is 0.5 to 0.62 max

Which injectors did you buy? are they 2.0 Ohm peak and hold? - check by unplugging one and measuring the resistance.

An outside chance - the S2 has a sensor on the EGR valve make sure that it is unplugged. It is not used and is nothing to do with the nearby unused socket that it looks like it should be plugged into.

I'M chasing an electrical fault and I noticed in the closed loop manual that there are some checks for rich mixture. It made reference to the purge system - worth a check.

[KenS]

Had some time today to investigate:

Do you know if the starter cat is still in situ or has it been hollowed out?
The casting is there but I do not know if it contains anything yet.

You mention .7 bar what chip do you have normal is 0.5 to 0.62 max
The chip is Everest, fitted by previous owner Paulous ( viewtopic.php?f=44&t=22390&p=282365&hilit=Paulous#p282261 ) at the time of fitting it apparently did give 0.9 boost.

Which injectors did you buy? are they 2.0 Ohm peak and hold? - check by unplugging one and measuring the resistance.
They do measure 2.0 to 2.1 ohm.

An outside chance - the S2 has a sensor on the EGR valve make sure that it is unplugged. It is not used and is nothing to do with the nearby unused socket that it looks like it should be plugged into.
The temperature sensor on the EGR is plugged in. Its two black wires connect to a grey and an orange:

egr wire.jpg

I cannot find these in the circuit diags, but I guess that if the sensor is good, it should not affect anything, but I will measure the sensor to check if its OK. Next MOT I shall unplug it, just in case.

I have read the Closed loop manual, I didn't realise it gave so much info. I have checked the EGR and EECS solenoids operate correctly and that the EGR valve moves and its diaphragm is good. I have not yet proven the sealing of the actual EGR valve nor the operation of the purge valve. I will investigate these a bit more. I have also re-run the compression check with the engine hot, the numbers are still very similar with 2 and 3 about 25psi lower than 1 and 4.
The gasket set has arrived from Kelvedon, so I think I will start the head gasket change at the weekend, at least it gets the job done now rather than in a few years time when I may be less capable! Is the turbo head gasket 'tab' the one in the photo below?

head gasket2.jpg

Thanks

[KenS]

I have slowly been disconnecting, labelling and cleaning/painting parts in order to change the head gasket. I am leaving the inlet manifold/plenum attached to the head but have removed the turbo/exhaust manifold, happy to find no cracks in the manifold.
Just removed the 2 fuel pipe connections at the back of the plenum and was looking for the knock sensor which I thought were the last parts to disconnect but noticed the secondary throttle vacuum parts may need removing, but they are very hard to reach, see or photograph. Any tip appreciated - are the actuator, reservoir and solenoid all connected to the head/inlet manifold or do parts or pipes need to be removed or disconnected when removing the head? Thanks

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