Pinking on WOT
Discussion
blitzracing said:
Not far off- but i would not take too much heed to the closed loop values- as long term trim is is set at idle, and for those conditions only- so in you case of WOT and open loop the fuel requirements will be way in excess of those at idle, so a whole set of new variables comes into play. Certainly fuel pressure is worth checking- but it needs to be at WOT, which can be somewhat difficult to read a gauge strapped on somewhere at 100 plus leptons, unless you have access to a rolling road. The nice thing about the Lambda output is it perfectly possible to get a passenger to read a test meter when you floor it.
Is it not unusual to have such a high long term (and occasional short term trim)? I often bark up the wrong tree but does the fact that the ECU believes it is under fueling at idle suggest there is something going on with fuel delivery which will also be affecting WOT? Or do the other factors mean they may be seperate issues altogether?Anyways I am just trying to get my head around how everything works so will do some further testing in the meantime.
Cheers
Edited by Danblez on Tuesday 1st September 13:30
Danblez said:
gruffalo said:
Just a quick thought have you checked the throttle POT is doing what it should, that is also used to decide fueling and they can wear.
Good call, this is on my list of things to test although because there seems to be an issue with the car underfuelling at idle I put this lower down the list!It takes 10 mins to set it up but I can't remember what voltage between which wires you need.
M
gruffalo said:
If the throttle pot is out at idle it will be out all the way up the range it gets magnified as the throttle opening gets bigger.
It takes 10 mins to set it up but I can't remember what voltage between which wires you need.
Cheers I have the 14cux manual which has the info I need. It takes 10 mins to set it up but I can't remember what voltage between which wires you need.
gruffalo said:
If the throttle pot is out at idle it will be out all the way up the range it gets magnified as the throttle opening gets bigger.
It takes 10 mins to set it up but I can't remember what voltage between which wires you need.
Not so when running the cat map so long as the ECU sees a linear sweep coming from the TPS its happy, if you go ahead and elongate the TPS mounting holes to set the TPS then dont forget to reset the ECU i.e unplug it and then reconnect, there is a reason why the later cat vehicles have not already got the TPS mounting holes elongated its because its not necessary any small errors will just be trimmed back by the 02 sensors anyway It takes 10 mins to set it up but I can't remember what voltage between which wires you need.
The 14CUX is more clever than you think- it will self calibrate the throttle pot withing certain limits, and these are:
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
So its quite a wide range.You only need to elongate the TP holes if you are outside this range. The cr*p written on the RPI site about setting the voltages is based on the older 14CU ECU that could not self calibrate. The TP is not used to determine the WOT fueling, its purely there to say if the car is at idle (TP low voltage), or if you have nailed it, when the rapid shift in TP voltage tells the ECU to dump in 10% more fuel for hard acceleration (fuel enrichment) for a short period. This is in addition to whatever the base fueling is in the fuel map . Its very difficult to measure when the fuel enrichment stops and you are just running on the fuel map values without a rolling road as you simply cant hold a TVR or like flat out for long enough at peak RPM on the public road to get a sensible reading without killing yourself. If you are measuring the lambda outputs, you might see as high as 1.4 volts during fuel enrichment phase,(around 12.5:1 AFR) that may drop to around 1.2 volts at AFR's or around 13:1, but as these are narrow band probes, and not supposed to be used in this AFR range there reading do vary a bit between probes depending on how old they are. Mind you the probe output wont drop to 0 volts until you are below 14.7:1 AFR, which is far too lean to make peak power, and could well cause pinking.
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
So its quite a wide range.You only need to elongate the TP holes if you are outside this range. The cr*p written on the RPI site about setting the voltages is based on the older 14CU ECU that could not self calibrate. The TP is not used to determine the WOT fueling, its purely there to say if the car is at idle (TP low voltage), or if you have nailed it, when the rapid shift in TP voltage tells the ECU to dump in 10% more fuel for hard acceleration (fuel enrichment) for a short period. This is in addition to whatever the base fueling is in the fuel map . Its very difficult to measure when the fuel enrichment stops and you are just running on the fuel map values without a rolling road as you simply cant hold a TVR or like flat out for long enough at peak RPM on the public road to get a sensible reading without killing yourself. If you are measuring the lambda outputs, you might see as high as 1.4 volts during fuel enrichment phase,(around 12.5:1 AFR) that may drop to around 1.2 volts at AFR's or around 13:1, but as these are narrow band probes, and not supposed to be used in this AFR range there reading do vary a bit between probes depending on how old they are. Mind you the probe output wont drop to 0 volts until you are below 14.7:1 AFR, which is far too lean to make peak power, and could well cause pinking.
Edited by blitzracing on Wednesday 2nd September 12:37
blitzracing said:
The 14CUX is more clever than you think- it will self calibrate the throttle pot withing certain limits, and these are:
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
So its quite a wide range.You only need to elongate the TP holes if you are outside this range. The cr*p written on the RPI site about setting the voltages is based on the older 14CU ECU that could not self calibrate. The TP is not used to determine the WOT fueling, its purely there to say if the car is at idle (TP low voltage), or if you have nailed it, when the rapid shift in TP voltage tells the ECU to dump in 10% more fuel for hard acceleration (fuel enrichment) for a short period. This is in addition to whatever the base fueling is in the fuel map . Its very difficult to measure when the fuel enrichment stops and you are just running on the fuel map values without a rolling road as you simply cant hold a TVR or like flat out for long enough at peak RPM on the public road to get a sensible reading without killing yourself. If you are measuring the lambda outputs, you might see as high as 1.4 volts during fuel enrichment phase,(around 12.5:1 AFR) that may drop to around 1.2 volts at AFR's or around 13:1, but as these are narrow band probes, and not supposed to be used in this AFR range there reading do vary a bit between probes depending on how old they are. Mind you the probe output wont drop to 0 volts until you are below 14.7:1 AFR, which is far too lean to make peak power, and could well cause pinking.
Tried the elongating TPS trick years ago Mark it made no difference for me or others (no surprise) but this was before knowing any better about the CUX and dealing with you way Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
So its quite a wide range.You only need to elongate the TP holes if you are outside this range. The cr*p written on the RPI site about setting the voltages is based on the older 14CU ECU that could not self calibrate. The TP is not used to determine the WOT fueling, its purely there to say if the car is at idle (TP low voltage), or if you have nailed it, when the rapid shift in TP voltage tells the ECU to dump in 10% more fuel for hard acceleration (fuel enrichment) for a short period. This is in addition to whatever the base fueling is in the fuel map . Its very difficult to measure when the fuel enrichment stops and you are just running on the fuel map values without a rolling road as you simply cant hold a TVR or like flat out for long enough at peak RPM on the public road to get a sensible reading without killing yourself. If you are measuring the lambda outputs, you might see as high as 1.4 volts during fuel enrichment phase,(around 12.5:1 AFR) that may drop to around 1.2 volts at AFR's or around 13:1, but as these are narrow band probes, and not supposed to be used in this AFR range there reading do vary a bit between probes depending on how old they are. Mind you the probe output wont drop to 0 volts until you are below 14.7:1 AFR, which is far too lean to make peak power, and could well cause pinking.
Edited by blitzracing on Wednesday 2nd September 12:37
back in about 2007 
the 14CUX manual says fuel enrichment happens when the ECU detects the throttle is fully open which is what made it on to my "suspect" list?
For anyone following this, the site which blitz posted a while ago is very informative.
http://www.g33.co.uk/fuel_injection.htm
Links at the bottom to the 14CUX manual which has a great trouble shooting section.
For anyone following this, the site which blitz posted a while ago is very informative.
http://www.g33.co.uk/fuel_injection.htm
Links at the bottom to the 14CUX manual which has a great trouble shooting section.
Edited by Danblez on Wednesday 2nd September 13:53
The point being fuel extra enrichment is only during the acceleration phase, not at constant load- so yes a throttle pot that goes from 0 to full voltage in a second will let the ECU know you have hit the throttle hard, so it puts in more fuel as the RPM rises. If however you accelerate gently, the rate of TP voltage change is much slower, so the ECU does not add the extra fuel, even when the TP has reached its full voltage. Either way once you have reached a steady load state at full throttle you will rely on the fuel map value for overall fueling, regardless of the throttle pot.
I managed to spend some time on this at the weekend.
Firstly I tested the fuel pressure.
Idle 1.6 bar
Light throttle 1.6 bar
Full throttle 2.2 bar - no fall in pressure all the way up the rev range. Altugh I believe to test this fully you need a long hill and 10 mins of full throttle.
Vacuum line to the FP regulator removed 2.5 bar
I also tested the lambda output and exactly as Blitz described cycling between 0-1.2 volts at idle and cruising and then 1.39volts when on WOT throttle all the way.
So the plot thickens and I dont know where to go now? I started to question whether I am going mad........
I wonder if it is intermittent. Should I test the lambda output on the opposite bank or is the likely hood on it running lean on one bank remote?
Firstly I tested the fuel pressure.
Idle 1.6 bar
Light throttle 1.6 bar
Full throttle 2.2 bar - no fall in pressure all the way up the rev range. Altugh I believe to test this fully you need a long hill and 10 mins of full throttle.
Vacuum line to the FP regulator removed 2.5 bar
I also tested the lambda output and exactly as Blitz described cycling between 0-1.2 volts at idle and cruising and then 1.39volts when on WOT throttle all the way.
So the plot thickens and I dont know where to go now? I started to question whether I am going mad........
I wonder if it is intermittent. Should I test the lambda output on the opposite bank or is the likely hood on it running lean on one bank remote?
I bit like the VW beetle on the Top Gear Botswana expedition........ my standard 400 ECU is now back with me and available, if you want to check that it isn't the mapping of yours that is the problem.
I must immediately say that I haven't checked that it works fine itself. I have a modified 5 litre, so cannot test it, and I bought it in a job lot of spares. However, it most likely was a working one removed by someone upgrading to megasquirt.
Alternatively, perhaps a better solution would be if you know someone locally with a 400, just do an ECU swap and see if his pinks on WOT with your ECU in, and yours doesn't with his ECU in. That was you are trying one that you know works fine. Or if you don't know anyone with a 400, just put out an appeal for anyone in your part of the country willing to try the test with you. There must be quite a few 400 owners near you. It cannot damage their ECU.
I must immediately say that I haven't checked that it works fine itself. I have a modified 5 litre, so cannot test it, and I bought it in a job lot of spares. However, it most likely was a working one removed by someone upgrading to megasquirt.
Alternatively, perhaps a better solution would be if you know someone locally with a 400, just do an ECU swap and see if his pinks on WOT with your ECU in, and yours doesn't with his ECU in. That was you are trying one that you know works fine. Or if you don't know anyone with a 400, just put out an appeal for anyone in your part of the country willing to try the test with you. There must be quite a few 400 owners near you. It cannot damage their ECU.
This is weird- to recap. You have the max timing advance at 28'- that should be fine. Your lambdas (both sides??) are showing plenty of fuel at WOT, so its not fuel pressure ECU, or sensors. I suppose it would be possible to have one injector partly blocked just to make one chamber pink- I doubt the lambda would pick that up as a lean mixture. Next step remove all 8 plugs and compare the colours or any sighs of overheating. The only other thing I can think off is excess carbon build up in the combustion chamber that raises the compression, but modern fuels dont carbon up any more...
The 7 is quite a cold plug, and tends to run a dark brown as the carbon does not get burnt off that quickly. I would think it will be quite clear that the insulators are completely white if there is an over temp issue due to lack off fuel in any cylinders. Hot spots in the combustion chamber can pre ignite the fuel, just like wrong timing, so overheating plugs or red hot carbon in the combustion chamber can have a similar affect. The point being about is lack of fuel is you loose the cooling affect as the fuel is injected into the combustion chamber, so things get too hot and you get pre ignition. Officially you should "plug chop" to get a reading, but holding the car under load, then killing the engine and coast to a stop. The idea is you dont allow the plugs to re colour at a lower RPM when the fuelling might be different, but TBH ive never seen a plug colour change that quickly. Pulling plugs out of a hot engine also has its own problems.
Gassing Station | Chimaera | Top of Page | What's New | My Stuff