As title suggests my Sierra Cosworth is running rich under load as shown up on a dyno run tonight.
The afr is 14 on idle but drops to 9-10 under boost which is way too rich.
It's running a Motorsport developments stage 1 chip / actuator.
The ATS and CTS map and Amal sensors have all been changed and fuel pressure and boost are as they should be.
Any ideas much appreciated. I've also emailed Stu at Motorsport developments for advice as he is usually very helpful.
And before you say just take it to Motorsport developments I'm up in John O Groats so that's not really an option for me.
Cheers
Derek.

 

I would wait for Stu and consider sending the ecu to him. Has it had a new fuel pressure regulator fitted?

 

It's still running the original fuel pressure regulator. It was 3 bar at idle and 4.5bar on boost.
I'm sure Stu will have some advice but thought it no harm asking here as well.
Cheers.

 

Its almost impossible to get a stage one that rich under load, the injectors are maxed out and 99% of the time they still struggle to stay rich enough to be safe.

Id advise to check the whole spec, injector part numbers etc.

 

Thanks James, I will check everything over. The injectors are standard yellows which were refurbed about a year ago. Maybe they could be at fault? The car has a new engine loom, fuel pump loom, wasted spark and all sensors are new. It holds 1 bar boost pressure under load but runs very rich. Strange one if a stage 1 should not run this rich!
Wish I lived close to a reputable Cosworth tuner to get it sorted.
Here's last nights graphs to see if that helps.

 

The new looms etc will certainly help with maintaining battery voltage, which will help things, did you try an extra 2psi of boost to see if the AFR started to correct? it will be on the top line of the map at 14psi, and on a stage 1 will be heavily using the WOT adders too,

You should set your fuel pressure to 3.5bar with the vac line disconnected.
The fact its up under load shows it is raising rate.

Do you have an AFR plot?

The next step would be to drag some data from the ECU to check all the sensors are operating well and calibrated ok,
If all is well, the fix is quite easy, if the AFR is good everywhere else, a simple reduction in the WOT table would probably fix the issue.

 

Thanks James,
We do not have an afr plot, we used a handheld device to test afr under load.
I've also not tried adjusting boost pressure to see if this helped. Do you think this could be all that's at fault?
If so I will try to go back for another rolling road session this weekend as the guy is away for 2 weeks from Monday.
I take it the boost is raised by just winding in the actuator rod a few turns?
Cheers
Derek.

 

It would be good to see an AFR against Boost plot really to see what is going on, certainly worth a test to add 2 lb of boost and see if the fuelling starts to level out.

max of 4mm preload on the actuator, the rest to be done by jetting the amal valve, if the boost is tailing off it may explain it, so if you can get it to hang onto some extra boost at high RPM the fuelling may correct.

 

Thanks James,
I'll speak to Stu and take it from there. I've I'd guess 3mm preload on the actuator so will not wind it in any more.
I've a spare Amal valve so may try jetting it once the guy with the rolling road is back home from touring in his mclaren in a couple of weeks!
Alright for some!
Cheers.
Derek,

 

Stu is on holiday i think so may not get a reply until next week.

 

all that graph shows is a dirty finger pointing lol

Mark

 

Ha ha, I thought it may be useful but it seems not!

 

you need a boost and fueling plot show rpm to be able to get any useful advice

Mark

 

Thanks for the advice so far, Anyone have any ideas on where to look next?
Whilst I had the bottom outer crank pulley removed I noticed the key way was a bit worn meaning the crank pulley was a degree or two further anti-clockwise than it maybe could be.Could this affect the timing enough to cause the rich running?
The car starts,idles and runs fine. Any help much appreciated.