Well, the plot thickens even more.

With an event tomorrow, and not having time to connect up & analyse the EGT's I thought I would connect all 4 injectors to drive 1 so all cylinders are the same. In theory, there should be no change to mapping apart from very slight drop in fuel pressure as all 4 injectors open together.

The result was unexpected. The mixture went very weak across all the range, especially at idle. It also became VERY unstable and unpredictable. When cruising, AFR gauge was going between 10:1 and 18:1 with slight throttle movements.
Changing to drive 2 made no difference.
My first thoughts were voltage drop on the power ground wire to the ECU causing the drives to drop out. That proved not to be the case:

Trace2 = injector drive
Trace1 = power gnd at ECU relative to engine gnd.
Shows a rise up to about 0.2V on the power ground, with injector drive stable.


The above trace did show a dip in voltage during the off period. This co-incides with the ignition charge time:

Trace2 = injector drive
Trace1 = IGT drive signal.


Further monitoring of voltage at the injector balast common shows some large dips in voltage (up to 2V), both when the ignition is charging and when the injectors are driven:

Trace2 = injector drive
Trace1 = Voltage at injector balast (AC coupled)


My suspicion is that the extra load from driving several injectors together is dropping the voltage to the point where the injectors are struggling to pull in, especially if the injector is called to pull in during ignition charge time, which is most likely at higher RPM. It is possible this has been the problem all along but has been highlighted by increasing the load.

My solution was to add a relay next to the ballast supplying +12 straight from battery + via a heavy wire. The mapping when driving all 4 together is now, if anything, slightly richer than previous 2+2.

_________________
If at first you don't suck seed, try drier grain.

Interesting stuff Chris, how did you get on today, did the engine stay in one piece?

_________________
Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

Engine did well today - or at least well enough to stay in 1 piece even if I did get beaten by the 3 novices

I was running basic actuator pressure and loads of fuel so should have been safe. AFR's are still a bit unpredictable though. One minute idling nicely on 14.4 then 10 minutes later down at 12. More study needed before I even think about winding up boost or leaning out mixture.

_________________
If at first you don't suck seed, try drier grain.

Good to hear you were able to drive home with everything in one piece. Sounds as though further research is warranted if the AFR's are up and down........

_________________
Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

That's very lean for the high-rpm area of the map Chris. I get it to more like 11.5 up there, if you're doing your autotest stuff and know you're going to be banging off the limiter chuck even more in, to try and help the engine out as much as possible, perhaps more like 10-10.5:1.

Why are you deliberately retarding the timing? That just causes more heat and loses power.

What ECU are you playing with these days?

At the RR day my afr meter was reading about 1 higher than the RR. Mixture was originally set to 11.5 to 11.8 on my gauge which showed 10.5 to 11 on the surrey RR. I suspected my AFR gauge was out as I could see black smoke and people who followed me said it smelt well rich.
I'm now suspecting the fueling is uneven between cylinders hence starting to look at waveforms and fitting individual EGT's. Not had time to connect these to study yet so jusr running 0.6 bar and richened right up.

_________________
If at first you don't suck seed, try drier grain.

Individual AFR sensor in each runner? Do it Chris, you know you want to!!!

Surely a man of your calibre could set up a controller to run all 4 together? £240 for the sensors and a couple of quid for the clever electronic stuff (that I don't understand). You could put that scrap metal money towards paying for the sensors!

Too late. Money's gone on food already

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If at first you don't suck seed, try drier grain.

Well, it's gone again.

Car has been run on actuator boost (0.8BAR max) and very rich fueling on boost, with a good warning system for charge and water temps so no charge temps over 40C while boosting and ditto water temps of 100C. Also a full set of ST185 pistons were fitted this time round.

Death was very rapid once again. I unplugged the coil and checked the cranking was even after the last event a couple of weeks back. Took it for a run to Devon on Saturday. I could hear the cranking was uneven when starting in Devon, and by the time I got home the cabin was filling up with smoke and it was running on 3.

A quick compression test shows 170/180/20/180 so No. 3 only and possibly No.1. That sort of puts paid to my theory of a fault in the second injector drive from the ECU otherwise No.2 would have gone.

Sadly, I never got round to connecting up my EGT probes so no data from that.

I'm begining to think it's blow-by on the rings (bores are pretty shot now) causing local overheating of the piston.

Anyone got any other ideas ?

_________________
If at first you don't suck seed, try drier grain.

What condition are the injectors? i.e. have they been tested for flow and spray pattern?

_________________
Kris
95 ST205 - slept for 10 years, now waking up...
Avensis
http://www.gtfours.co.uk
_______________________________________
Turbocharging - the replacement for displacement

Not tested, but they are different injectors to the ones fitted the first time ringlands failed.

_________________
If at first you don't suck seed, try drier grain.

After reading the above posts, maybe the retarded ignition is to blame... this will not be good for cylinder temps, and I agree the AFR should be around 11 > 11.5:1 to be safe, even though max power is 12.5:1

_________________
Kris
95 ST205 - slept for 10 years, now waking up...
Avensis
http://www.gtfours.co.uk
_______________________________________
Turbocharging - the replacement for displacement

My wideband sensor has died completely now, but I've richened up the top end from the map I was running at surrey RR and that showed it as below 11:1 so should be safe.

Just looked at the ignition map and it should be running about 20 degrees (absolute) at the boost levels I'm running, also only a degree or two off det. at mid range RPM on 95ron (now running tesco 99 only) so I don't think it's massively retarded.

I'm planning to build up my 185 bottom end with s/h pistons and new rings as the next step, and make up some electronics to monitor the EGT probes. Tempted to go straight for forged but I'd rather diagnose the problem first on an engine I'm not worried about blowing up.

_________________
If at first you don't suck seed, try drier grain.

You seem to having as much luck as I have in general with those ringlands Chris. You're a lot clever man than me so I am sure you will sort it (hopefully this time) sorry I don't have any useful ideas, but wish you all the best with it. Has made interesting reading (and looking up what half of it means lol) I dunno how my block is but you are welcome to it if its any use to you

So what at the symptoms of ringland failure?

Without stripping everything down, how can you tell by the way the car runs?

Lump idle? Loud clanging?

I assume this is down to the design and build of the OEM Toyota pistons and you will never have ringland failure again after replacing your pistons with forged ones?