LC-1 installed on SLK 230 - compare readings ? - Page 2 - PeachParts Mercedes-Benz Forum

salty325 · #16 03-19-2009, 02:27 PM

The HFM system on the 111.973 engine will back off the ignition timing if it senses pre-ignition (there is a piezo on the cyl head), so it would not knock ulness it was drastically lean or overheating.
Also, most ecus go into 'open loop' above a certain load point / throttle position, so it will not correct fuel delivery for a lean condition above that load point. The stock narrow band is referenced for closed loop only.
So, either it is really going lean, or, all is well and the mysterious smog air pump (if at all there is one) is throwing off the wide band at wot.
Just wish I knew where the pump was, so I could try and disable it and then check the AFR.

JayRash · #17 03-19-2009, 02:32 PM

i like the fact that u seem to know ur stuff. thats gr8 to have u on our forum man.

c280nz · #18 03-19-2009, 03:16 PM

yes you are doing well at describing your problems, i have a lc1 on my c280 and it runs alot richer than that at WOT, do you have any tubes connecting into your exhaust header? what year is ur 23k? what chassis code? w202....?

salty325 · #19 03-19-2009, 04:18 PM

Thanks Jayrash and C280nz.
Its a '98 R170 chassis with the 111.973 engine.
No lines or pipes connecting to the exhaust manifold as far as I can see, but I will drop the heat shields tomorrow to get a better look at the manifold and supercharger ( I read some sketchy stuff on another forum about there being a smog pump built into the s'charger housing).
Thing is, I don't feel good about going wot until I know whats going on.

JayRash · #20 03-19-2009, 04:26 PM

Salty,

if ur car is stock and feels like it has 193 hp in the engine time a run fro 0-100mph. compare to stock numbers on the net should be abt 20 sec, now if u get like 22 or something on the count of a bad start try and see 60 to 100 time and compare that to what u find on the internet.

i know its far from the best way for checking, but i still think ur car is fine unless u really feel like something is off in the power output.

hope that helps

salty325 · #21 03-19-2009, 04:38 PM

Think I'll try that. I guess 0-100 mph is a long enough run to eliminate some of the error that one would get in a 0-60. Thanks for looking up the 0-100 time.

c280nz · #22 03-19-2009, 09:10 PM

http://www.detali.ru/cat/oem_mb0.asp?TP=1
i just had a look aorund on here and i cant see any sort of exhaust emissions system

Turbo E320 · #23 03-19-2009, 11:58 PM

Its the Secondary Air system which I guess is a smog pump system. On your car its a bypass in the supercharger but it should only operate when the car isn't fully warmed up or you have sat in traffic. Then again my Secondary Air system hums to life all the time and not just in the required situations.

whipplem104 · #24 03-20-2009, 10:53 AM

The supercharger is the smog pump on this engine. What happens is the ecu activates the clutch at idle only and makes boost in the intake piping but not the intake manifold. Then it opens the diverter valve and the boost is piped into the exhaust. The pipe goes in the block first though, if I remember correctly. This is not your problem though. If you were to lean then you would have a code for adaptations. If you are really concerned you could have the adaptations checked or have a technician take it on a test drive to see what the ms of injection duration is at full throttle. Mercedes has all this information on the SDS and the nominal values.
I also would not be surprised to see a fairly lean condition on this car. It has only a maximum of 7lbs of boost and is 9:1 compression.

salty325 · #25 03-22-2009, 03:32 AM

C280Z, I checked those diagrams earlier and could'nt find anything either.
Turbo E320 and Whipplem104 - so it seems the smog pump should only be active during warmup / idle - that makes sense.
However, on the SLK 230, the ecu engages the supercharger clutch only at around 2000 - 2500 RPM.
There is a by-pass valve between the air filter housing and the supercharger outlet that allows the engine to draw air directly from the air filter, instead of through the supercharger, while the supercharger is disengaged.
Anyway, will drop the exhaust manifold heatshield to see if there are any lines from the supercharger housing to the engine / exhaust.

JayRash · #26 03-25-2009, 08:21 AM

Salty,
We are still waiting your update

salty325 · #27 04-01-2009, 05:08 AM

hi, dropped the heatshield (pita), still couldn't find anything, unless there is a line between the s'charger housing direct to the cyl head.
I've decided to forget about the smog pump (if there even is one) for now.
Strange thing is, AFR now is consistently approx 14.1 to 14.2 at wot (earlier it was above 15.0), except upwards of 5000 RPM where it creeps to 15.0 I did'nt change anything, so was just wondering...
So, I guess there is a wee bit of fuel delivery problem at the top end. Checked the plugs - insulators were white. Changed to plugs 2 steps colder, insulators still white - it really is lean.

Pagz · #28 04-05-2009, 04:42 PM

Heres a stock dyno run on my C230K,it seems similar to your afr.
Sure If you were running more boost you would need to bring it down alittle but on the stock engine with 5.5psi i cant see that afr being a problem as long as you run good fuel.

However if you wanted more power over economy that would be a good place to start =)

salty325 · #29 04-07-2009, 07:37 AM

Hey Pagz, thanks for the chart. And yes, the AFR seems exactly like it was on my car. But the AFR spike at the end should not really be there, should it ? Power curve also drops quite a bit, at the same time as the AFR spike (hope I'm reading it right).

Ok, so this may sound strange - I ran the car for a bit with the oil breather disconnected from the air box. Guess what, it gradually got a bit richer every time I floored it. MAF getting cleaner by itself ? (or just seeing cean air) ?? Built a catch tank for the breather, plugged the breather inlet on the airbox.

Now the AFR is consistently 13.7 - 13.9 at wot, all the way to the redline. Sounds wierd, but I'm just glad it seems ok now. Hope the AFR stays that way.

Pagz · #30 04-07-2009, 08:12 PM

Hey,
From the point where acceleration drops off at 138km/h (rev limit in 3rd gear) it shows that boost(after the small flat spot) and afr rise...this may be due to the TB closing and the ecu cutting fuel...im not totally sure.

Interesting about the catch can,i wouldnt have thought that would make much difference unless you were pumping oil through(any blue smoke?),infact if anything it may make it more rich as your pumping in hot air with the engine vent to intake?.
Did you reconnect it and re-check wot afr?

afr under wot may be a bit tricky to compare day by day....i mean if the engine is slightly hotter...or the ambiant temps are different then the maps may say make that slightly richer for saftey sake?

Cheers,
Paul