Idle, Emerald, Mapping, Fuelling Problem

[ben7]

I have stripped and cleaned my Jenvey DTH TB's as part of a wider overhaul of all things engine related.  I've also installed a bosch wideband lambda and Plex AFR module and DM-6 gauge (very trick!)

I have set up the idle as per Emerald's instructions and from cold this afternoon, she fired up first time and purred beautifully at 1100 rpm, despite having very lively cams.

After around 5 mins of idling, the AFR gradually moves from around 13 (on start up) to bang on 14.7 as the T's P's start to normalise a little (still cold though).

A couple of blips of the throttle (up to around 4,500rpm) and the engine returns to 1100 idle no problem (no dipping below and having to catch itself).

Then for apparently no reason at all, after around 5 seconds on idle, the fuel will lean out to 16+ AFR, the engine will cough, start to die, then catch itself as it drops below 1100, stabilises, then after another 5 seconds the same thing happens again.

I suspect it is a setting in the map somewhere.  Over run cut out is set at +2,500 rpm, so I don't think it's that, plus the fuelling leans out as opposed to cuts out.

Any ideas?

[oilyhands]

Get a screen shot of the live adjustments page of the Emerald software while this is happening, it could be that one of the sensors is acting up, if the air temp sensor is over reading, it will lean off because to thinks the inlet charge is hotter and less dense, also, please include a screen shot of the injection map.

Oily

[ben7]

Thanks Oily.

I've managed to fix it.  It was a setting in the Injection Corrections tab.  It jumped from 22 at 40deg to 8 at 50deg.  With the car partially warmed up, the coolant was at 40/50 degs and the ecu was trying to smooth the large gap.  I sorted it by upping the 50deg correction to 18, then 60deg to 9.

Ben

[MacP]

I have a similar issue on my engine (1.9 VVC DVA K06a with plenum and Emerald K6).

It happens sometimes on a cold start.  The engine fires briefly (almost immediately) but then dies immediately. On a restart it won't start without throttle and dies immediately if throttle removed*.  It runs steadily on throttle at 1,500 but hunts between 1,000 and 1,500 if throttle is eased off.

*It is possible that this only happens if the ignition is turned off following the stall (i.e. ECU is powered off).  I have had one recurrence of the problem since I thought of this a couple of weeks ago and it's possible that on that occasion I turned the key far enough to power off the ECU .

I have watched the live adjustments screen when this hunting is happening and it is making large adjustments to the fuelling (not IACV or ignition).

The only fix that's worked once this problem has occurred is to warm up the engine fully on throttle then switch off for (at least) five minutes after which it will fire up and run with no problems.

If I try to start the perfectly warm engine after a minute or so (rather than waiting for 5-10 minutes) it still won't run without throttle and continues the hunting routine.

Any thoughts?  

[ben7]

Interesting as this was what mine was doing before making a few adjustments, which then lead to the issue in this thread.

I have DTH TB's as opposed to a plenum so rather than go through what I did, it might be helpful to have a look at this first? http://www.tsmotor.com/coppermine/albums/userpics/10001/Emerald_K6_IACV___Cold_start_crib_sheet.pdf

 

[ben7]

Ok, back again.

This is a different problem but involves the bits in the title so thought I'd re use it.

Was blatting last week.  Managed to disconnect the threaded rod that connects to the throttle cable to the dthtb's (it wasn't screwed in enough to one of the ball joints) when I was embarking on an enthusiastic overtaking manoeuvre.

Anyhow, I have now managed to reattach it, but have obviously screwed it in more, therefore shortening the overall length which is in turn leaving the tb's more open than previously on idle i.e they don't shut properly.

I started car and obviously revs race away before quickly turning it off.  Adjust the TPS in map along with idle control to reflect new TPS lowest number.

Now I try to start engine and it just catches, coughs, bangs and dies.  Sounds dreadful.  Applying throttle doesn't help, it just dies again.  I stopped trying once black smoke appeared from the tb's(!), and the butterflies are now carbonised.

The car was working perfectly on the blat before linkage came loose (and it rev'd freely on first start up before I adjusted the tps albeit up to 3.5k rpm before I turned it off).  And my simple brain is telling me that the only thing that should be different is that the idle should be running a lot higher than it was (as the tb's are more open).

Any ideas what on earth is going on?

[Mr Locust]

 

Any ideas what on earth is going on?

 

Short answer; by your own admission you buggered it up!

Longer answer; the job of the ECU is to maintain the air fuel ratio, AFR.  And you adjusted the AFR values of most of the load sites in your ECU maps, making them leaner than when the mapping was configured.

Explanation:

The fuel map cells deliver an amount of fuel which is based on how long the injector is switched on.

For most Caterham/Emerald/DTH throttle implementations, the active cell of the fuel and ignition maps is determined by engine rpm and throttle position sensor, TPS.  These are the axes of your maps when you access the calibration software unless your setup is calibrated to reference manifold air pressure, MAP (unlikely).  The purpose of the TPS% in the setup is to give an accurate approximation of the airflow into the engine as the engine has no other airflow meter (as found in many volume production car fuel injection setups).

At small throttle openings, a small change in throttle angle will give a massive change in the airflow into the engine.

If you opened the throttle wider, then reset the TPS operating range and made no other changes, you made the whole fuel map leaner at every load site except wide open throttle or 100%TPS.  You allowed more air for each TPS%, most significantly for the 0% (and near 0%), lines of the maps and provided the same fuel value.

Assuming that the engine ran well before and that you haven't adjusted anything else, the best solution would be to reset the throttle stop back to the previous position and recalibrate the TPS.  Even better if you noted the TPS values before you reset and reinstate these, then set the idle stop back to 0%.  Any adjustments should be made by adjusting your cable and linkage and setup, not by rescaling the TPS.

Hope this helps.

 

[ben7]

Yep, I'd figured your first line out at least!  

Doh, yes of course that makes complete sense.  My logic hadn't reached that far!

Hypothetical question.  If I loaded up the previous map (that worked before I buggered it up), does that also reset the TPS in the ECU?  I know practically that's no good as I'd be idling at 3000rpm or whatever, or does the emerald 'remember' the new TPS position regardless of whatever map you load up?

So the number one rule would appear to be don't touch the TPS.  I do know the previous 0% figure, as the idle control was set to it.  My simple brain suggests that the original 100% position will be the new 100% position minus the difference between the new 0% position and the original 0% position won't it?

If I am 'just out' with the 100% figure (say within 1% of the original TPS number), then map will stretch/compress accordingly?

Throttle cable.  Why did I not think of adjusting the throttle cable!!!

[ben7]

And thanks!