Dyno run AFR & detonation
Discussion
My car is a totally stock engine 500 Griffith, 103k miles with a top end rebuild including cam around 6000 miles ago.
I've just had a dyno run to see where dogs lie and the concern is detonation where the two dips occur on the AFR graph at around 3800rpm & at 4750rpm. Both the dyno knock sensor detected it & it could also be heard.
AFR seems to be heading in the wrong direction after it goes lambda open loop above 3250rpm and the operator's opinion was a lean burn induced knock.
What is the opinion of the plots from those people with experience of this engine?
Kev
I've just had a dyno run to see where dogs lie and the concern is detonation where the two dips occur on the AFR graph at around 3800rpm & at 4750rpm. Both the dyno knock sensor detected it & it could also be heard.
AFR seems to be heading in the wrong direction after it goes lambda open loop above 3250rpm and the operator's opinion was a lean burn induced knock.
What is the opinion of the plots from those people with experience of this engine?
Kev
Motorsport developments in Bispham by any chance ?
That does look to be running weak. 12.5 - 12.8. Would be more where you’d want to be at wide open throttle.
Have you checked your ignition timing re the pinking.
Your down a fair bit on bhp as well.
That does look to be running weak. 12.5 - 12.8. Would be more where you’d want to be at wide open throttle.
Have you checked your ignition timing re the pinking.
Your down a fair bit on bhp as well.
Edited by carsy on Friday 13th July 13:59
carsy said:
Motorsport developments in Bispham by any chance ?
That does look to be running weak. 12.5 - 12.8. Would be more where you’d want to be at wide open throttle.
Have you checked your ignition timing re the pinking.
Your down a fair bit on bhp as well.
Yes, I'm local to the area. That does look to be running weak. 12.5 - 12.8. Would be more where you’d want to be at wide open throttle.
Have you checked your ignition timing re the pinking.
Your down a fair bit on bhp as well.
Edited by carsy on Friday 13th July 13:59
Timing was also suggested so will pull the timing light out of hibernation.
Yes, power isn't quite what I had hoped but the curves seem the right shape and it's a high miler. Oh & just discovered on RoverGauge that throttle pot is only opening to 75% on the pedal but pulls to 96% under the bonnet. Think the throttle stop requires a small adjustment
Just plugged in RoverGauge and fault 23 seems to point to fuel supply/pressure.
Edited by Kev Bamber on Friday 13th July 16:45
Kev Bamber said:
just discovered on RoverGauge that throttle pot is only opening to 75% on the pedal but pulls to 96% under the bonnet.
Not only are you restricting airflow but also the 14CUX needs 84% for 1994 Griffith or 80% 1995on to activate the full load additional fuel. (91% for Land Rovers)Kev Bamber said:
Just plugged in RoverGauge and fault 23 seems to point to fuel supply/pressure.
We all know there is no fuel pressure sensor, fault code 23 Low Fuel Pressure is simply set when the short term trim is maxed out lean and therefore could be triggered by several other issues like an air leak.I’ve had a closer look at code for these fault codes
23 – Both short trims are near to max (extra fuel)
28 – One short trim is maxed out (extra fuel)
I guess 23 could mean low fuel pressure or an air leak effecting both banks as both short trims are near maxing out, where as 28 means only one bank is effected so maybe an air leak effecting one bank or an injector issue on one bank.
Fix your pedal full throttle and check your fuel regulator vacuum pipe then see how it goes.
23 – Both short trims are near to max (extra fuel)
28 – One short trim is maxed out (extra fuel)
I guess 23 could mean low fuel pressure or an air leak effecting both banks as both short trims are near maxing out, where as 28 means only one bank is effected so maybe an air leak effecting one bank or an injector issue on one bank.
Fix your pedal full throttle and check your fuel regulator vacuum pipe then see how it goes.
That's the easy job done, now getting full throttle.
Thanks for the guidance, will check for leaks first, then the pressure regulator with vac pipe both on & off, & if that checks out okay, then rig up a fuel pressure gauge in the car so can see what happening at WOT. Then some AFM volt checks.
So from what you described, probably lots lambda fuelling correction being added whilst closed loop <3250rpm then when goes open loop, leans off even more after switching to map only?
Thanks for the guidance, will check for leaks first, then the pressure regulator with vac pipe both on & off, & if that checks out okay, then rig up a fuel pressure gauge in the car so can see what happening at WOT. Then some AFM volt checks.
So from what you described, probably lots lambda fuelling correction being added whilst closed loop <3250rpm then when goes open loop, leans off even more after switching to map only?
Kev Bamber said:
So from what you described, probably lots lambda fuelling correction being added whilst closed loop <3250rpm then when goes open loop, leans off even more after switching to map only?
Correct, but only below 80% or 84% throttle the effect of the lambda trims gradually decay to 3,400 rpm (as in your power run), above 80% throttle closed loop is immediately disabled regardless of rpm, therefore your 76% throttle is holding closed loop longer and maybe causing your fault codes, you are also missing out on the full throttle fuel enichment.We live in hope, Steve
Edited by stevesprint on Monday 16th July 22:49
Kev Bamber said:
My car is a totally stock engine 500 Griffith, 103k miles with a top end rebuild including cam around 6000 miles ago.
I've just had a dyno run to see where dogs lie and the concern is detonation where the two dips occur on the AFR graph at around 3800rpm & at 4750rpm. Both the dyno knock sensor detected it & it could also be heard.
AFR seems to be heading in the wrong direction after it goes lambda open loop above 3250rpm and the operator's opinion was a lean burn induced knock.
What is the opinion of the plots from those people with experience of this engine?
Kev
At no point in that graph is the fuelling in closed loop.I've just had a dyno run to see where dogs lie and the concern is detonation where the two dips occur on the AFR graph at around 3800rpm & at 4750rpm. Both the dyno knock sensor detected it & it could also be heard.
AFR seems to be heading in the wrong direction after it goes lambda open loop above 3250rpm and the operator's opinion was a lean burn induced knock.
What is the opinion of the plots from those people with experience of this engine?
Kev
Though the general trend is weakening towards the top end everything from about 2000rpm onwards is going too weak for full throttle mixture anyway. I'm surprised the dyno operator didn't stop the run, it's obviously wrong early on and getting wronger every second.
Kev Bamber said:
Fuel pressure down by around 3psi
How was that taken? Was it pump on (Rovergauge ) and engine static? - the value that really matters is WOT under load at peak RPM with you should have full pressure to stop the engine leaning out.As for the lean error on lambda, it will only monitor the mixture in closed loop and less than 2/3 throttle, so to lean out in this situation would be pretty severe fuel starvation.
Edited by blitzracing on Thursday 19th July 15:59
I've run up to 5500rpm at WOT and fuel pressure is dropping from 2.5 to 2.4 bar (1.5psi drop)
Should it hold rock-solid or is a slight drop expected?
Fault code 23 is no longer appearing since correcting the static test fuel pressure up to 2.5bar.
Should it hold rock-solid or is a slight drop expected?
Fault code 23 is no longer appearing since correcting the static test fuel pressure up to 2.5bar.
Edited by Kev Bamber on Monday 23 July 21:24
That's the fuel filter changed and checked for crimped fuel & return lines.
Whilst under there did some voltage checks. I'm seeing around a 2.75 volt drop between battery & fuel pump. So, around 9.5 volts at pump engine off & 11.2 volts engine running.
Cleaned & remade obvious connectors and terminals, no significant difference but think getting closer to the root cause.
Whilst under there did some voltage checks. I'm seeing around a 2.75 volt drop between battery & fuel pump. So, around 9.5 volts at pump engine off & 11.2 volts engine running.
Cleaned & remade obvious connectors and terminals, no significant difference but think getting closer to the root cause.
Cleaned all terminals and connectors I can access. The only one I can't locate is described as being a brown plug/socket on the bulkhead under heater control unit. I guess part of the dash has to come out to access that.
On the Bertram Hill wiring schematic the pump -ve is just shown earthed, but I presume earths come back on the loom to the front of the car. My earth disappears off into the boot with the +ve.
If no improvement after this, will then consider pulling some thicker wire.
On the Bertram Hill wiring schematic the pump -ve is just shown earthed, but I presume earths come back on the loom to the front of the car. My earth disappears off into the boot with the +ve.
If no improvement after this, will then consider pulling some thicker wire.
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