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"I did not see a need to try and understand what was happening at anything other than idle-one only has to look at the AFR value spread in a given cell"
True...but the returned value from the MAF is wandering, touching other cells, affecting what the fuel/timing will be...but the actual airflow to the engine _isnt_.
This is the problem many have had with poor airflow patterns across hotwire and karman MAF's with aftermarket intake systems...long honeycombs _usually_ resolve these issues.
The eis looks like a nice smooth system, but its more about the distribution of uniform flow across the entirety of the hotwire. How that system works requires that at an even CFM flow, the measured resistance of the wire remains stable. An uneven mass/uneven areas of mass, of air, make the wire heat and cool irregularly, and you see a wandering '+' in the live map.
The stock airbox resolves this..air flows theu the filter smoothly down the MAF throat. Thats also why you see an air horn ahead of the AFM in the earlier cars.
How the airbox looks, #5, a nice uniform mass/velocity flow into the MAF.
Now...the EIS...it would tend that two pipes that meet the way they do, will have a higher velocity (mass flow) at the center of the MAF, and not entirely uniform.
I can't confirm you have the correct terminals as I'm not in the office. But as the pot has no end stops, someone may have continued to turn the pot clockwise even though it was at max.
Try turning the pot 4 or 5 turns anti clockwise and see if the resistance starts to decrease. This can sometimes damage the pot.
If the resistance doesn't decrease then either the pot is damaged or you have the wrong terminals.
I think I had the wrong terminals, I measured between terminal 1 and 2 and found the resistance could be varied by turning the screw adjustment. Not sure what it was set at originally as I have turned it a few times but I have now set it to 300 ohms. At least I will be ball park now when I test tomorrow
If you look in the harness side of the connector there are only 2 pins there - can work out which 2 (I forget if its 1/2 or 2/3.. I usually just look in the plug when measuring the pot )
Somewhere in this forum I also posted about how to convert a non-cat car to using O2 loop, with pics etc.
Hi, I checked out the plug for the CO pot and your right there are only 2 terminals connected and they are terminals 1 and 2.
Didn’t get a chance to try it last night but will try to make time tonight.
New rubber hoses arrive for the intake and ISV / oil breather tomorrow so can whip of the manifold and change all these to eliminate them.
On the effect of the cams Colin confirmed that they will idle at both S4 and GT target without the issues I am having.
Out of interest I am going to try fitting the new MAF/TB rubber boot first to see if this alone could be the issue. I did swap this boot for a spare I had which seemed to have tighter connections to the plastic hoses which connect into the side of it and that seemed to improve things slightly, inasmuch as when I wiggled the MAF with the car running it did not stall straight away.
So I tried fitting the new rubber boot between the MAF and the TB, wow the new boot is super tight for the plastic side pipes compared to the old one. So much so that I decided to pull the manifold and fit all the new pipes.
Hopefully I will get a chance over the next couple of days to get the job completed, tested and feedback
The manifold is off which let me deal with a small weep from the water bridge (sealant as well as the rubber ring).
First off, the new pipes and boot is all so much tighter than old ones, a lot more effort to fit together, especially the plastic y connectors which go into the rubber TB boot. The old ones where a very easy fit, the new ones completely different.
To state the obvious, this will eradicate any leaks I might have had.
I also have to say that I am glad these are all getting replaced given the difference to the new parts.
I had a very helpful conversation with John Speake on Friday which highlighted a few thing, so I will be loading up both GT maps for the EZK and LH along with fitting the air filter which I was omitting from doing.
So when Fred was talking about equalising the flow of air over the MAF he was potentially very close. I didn’t appreciate how sensitive the MAF could be.
Just need to get everything back on and see where I get to.
I suspect that the boot and other fitments that you are replacing have a life of about 10 years, after that there is a small but progressive decline. The options are to replace said items or one can do as I have done for some time and use RTV to help seal the push in joints and then secure them with lightly tightened clamps. I recently had my manifold off to replace the knock sensors and the ISV. inspected the rubber bits and at face value seemed ok but ideally I should have replaced them. Just have to pull the manifold next year [again!].
After fitting the new ISV rubber pipes, MAF / TB rubber boot, vacuum rubber pipes and fitting the air filter the car now idles properly. No issues at cold or hot idle.
I am not going to guess which was the route cause as there could have been both an air leak and uneven flow over the MAF from the lack or air filter.
The idle is pretty good, and the A/F ratio looks pretty good on the ST2. I was wondering whether the ST2 feature of using the O2 sensor would be any benefit for my non car car ?
It does have the recommended WB sensor but I am unsure if this would work or whether there would be any benefit?
After fitting the new ISV rubber pipes, MAF / TB rubber boot, vacuum rubber pipes and fitting the air filter the car now idles properly. No issues at cold or hot idle.
I am not going to guess which was the route cause as there could have been both an air leak and uneven flow over the MAF from the lack or air filter.
The idle is pretty good, and the A/F ratio looks pretty good on the ST2. I was wondering whether the ST2 feature of using the O2 sensor would be any benefit for my non car car ?
It does have the recommended WB sensor but I am unsure if this would work or whether there would be any benefit?
Do nor use a WB to pretend to be a NB. Use each for their intended purpose.
After fitting the new ISV rubber pipes, MAF / TB rubber boot, vacuum rubber pipes and fitting the air filter the car now idles properly. No issues at cold or hot idle.
I am not going to guess which was the route cause as there could have been both an air leak and uneven flow over the MAF from the lack or air filter.
The idle is pretty good, and the A/F ratio looks pretty good on the ST2. I was wondering whether the ST2 feature of using the O2 sensor would be any benefit for my non car car ?
It does have the recommended WB sensor but I am unsure if this would work or whether there would be any benefit?
I am getting mostly 14.7, I am still playing with setting and maps on the ST2 but am finding the GT map about the best so far with the limited time I have had.
The GT map seems to hold the idle higher at cold to get the engine warmed up a bit before dropping the revs, this seems to be very handy for Colins Cams as they have additional list and duration over the GT cams.
The S4 and GTS maps don't seems to have this cold start feature.
I will keep experimenting to try and get the idle smoother although it's not at all bad.
Change your coding plug to a cat car and add a factory fit NB O2 sensor. This is much better than the CO pot and will always be self adjusting.
Do not use the simulated NB output of any WB O2 sensor system. It will work OK, then swing wildly and cause you to chase your tail!
Cool, glad to hear your idle is sorted.
Hopefully it was just something to do with the hose connections, and all is good and will remain so. If it happens again I'd be suspicious of the MAF connector on the harness side if its original - the insulation inside the rubber boot on the 6-pin AMP connector cracks and can short inside the boot, causing similar issues.
05-02-2018, 05:23 PM
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