Hi all, Ive recently had my fc3s turbo 2 put through an mot to find out \'surprise surprise\' the emission\'s were way off!
(http://i664.photobucket.com/albums/vv7/identiti1/l002-1.jpg)
Ive recently installed a front mount intercooler and new fuel pump along with all the filters and a new set of plugs with magnacor leads. I allso swapped the after market ecu out for the standard one hoping it wouldnt run so rich in preperation for the mot.
From the results it seems its running rich and isnt burning the fuel and its hunting like it has an air leak which i was half expecting from fitting a front mount intercooler as theres plenty of chances for air leaks on the new connections.
Im guessing this issue is a collective of of problems rather than an single fault?
If anyone has any info or knowlage please share as i dont know where to start:( cheers Adam
What fuel pump did you go for?
Walbro pumps are much more efficient than the stock pump, and hence they produce more pressure than the stock one when running through the resistor at idle. It seems that this can increase fuel to air during idle, and this isn\'t corrected by the lambda as it\'s not used below about 1500rpm.
You can probably correct it a bit by adding another resistor in series with the standard fuel pump resistor (this will be safe, as both resistors will be out of the circuit when you are under load).
Other things to try:
- New Plugs
- Make sure it\'s fully warmed for the MOT
- Ask him if it will pass on the fast idle test (if HC or CO test is a pass at normal idle, they can run the car revs higher to see if the other reading will come good.)
- Make sure water temp sensor on the back of the water pump is properly plugged in - if not, the car will overfuel to correct an apparent cold condition
Its running a walbro 255lph pump at the moment. My mate was following me and he said he could smell how rich the car was running and could see fumes coming from the exhaust. All this was before i fitted the walbro pump so kinda hoping it might not be related to that :)
That temp sensor sounds like a likely culprit as i assume the system will be in closed loop if its not recieving info from that sensor?
Since putting the FMIC on and a larger exhaust would this increase the HC count in the exhaust?
Are you still running the airpump?
At idle, the car will be running off fixed maps for fueling - with an overide for water temperature - running richer when cold.
As you open the throttle, it will adjust fueling based on the airflow meter signal, but at idle this is assumed to be closed, and any air coming in is via the small bypass adjustment - a little screw usually capped off on the AFM - you can remove the cap and gain access to the adjuster - that might help you a bit.
No the air pump is long gone im afraid,it wasnt plumed in when i removed it.
Quote from: Adam fc;742819No the air pump is long gone im afraid,it wasnt plumed in when i removed it.
That\'s an impressive CO figure then - mine is usually at or near the 3.5% (higher when cold) !!
I had assumed you\'d still got that plumbed in.
Okay well ive got an afm gauge which came with the car plumed in so ill have a tinker with this AFM adjustment screw and see what effect this has to the running.
Im allso going to have a go at setting the TPS tomorrow. Could this be a factor in the emissions as i was told the MOT tester will also check fast idle and half of the engines maximum rpm?
Quote from: Prof;742821That\'s an impressive CO figure then - mine is usually at or near the 3.5% (higher when cold) !!
I had assumed you\'d still got that plumbed in.
No sorry forgot to mention that! My understanding is that HC are produced by unburnt fuel?
yep - HC is unburnt fuel - it could be poor ignition either because the mixture is rich or plugs are bad / fouled, or coils not giving a good spark. It could also be down to rich mixture - giving a lot of unburnt fuel in the exhaust. I suppose it could also be down to excess oil not getting burnt off.
CO is down to partial burn - so not enough oxygen in the fuel / air mix for complete combuston. This would normally be converted to CO2 in the cat with a supply of air (air pump).
It\'s worth checkng a lot of things - vac leaks, air leaks, spark quality, plugs, temp sensor, fueling, fuel pressure (if you can monitor it), idle air adjustment (AFM / BAC), timing.
Okay well thats given me a direction to start looking in as before i didnt know where to start!
Ill report back tomos! cheers Adam
Well ive been through pretty much all the vacuum conections today allong with all concections and earths.
Ive reset the TPS to within the the given parameters using the multi meter method and ive allso run the car with the aftermarket ECU but this had litte or no effect of how rich she was running at idle.
Ive booked her in at RX Motors for next monday with Tim so ill hang on and see what they make of it.
Be interesting to find out what the issue is though. Cheer Adam :)
Quote from: Prof;742806What fuel pump did you go for?
Walbro pumps are much more efficient than the stock pump, and hence they produce more pressure than the stock one when running through the resistor at idle. It seems that this can increase fuel to air during idle, and this isn\'t corrected by the lambda as it\'s not used below about 1500rpm.
You can probably correct it a bit by adding another resistor in series with the standard fuel pump resistor (this will be safe, as both resistors will be out of the circuit when you are under load).
Other things to try:
- New Plugs
- Make sure it\'s fully warmed for the MOT
- Ask him if it will pass on the fast idle test (if HC or CO test is a pass at normal idle, they can run the car revs higher to see if the other reading will come good.)
- Make sure water temp sensor on the back of the water pump is properly plugged in - if not, the car will overfuel to correct an apparent cold condition
Just been trawling through the US site rx7club.com and there have been issues of people adding the walbro 255 and thus overwhelming the stock FPR and making the car run rich at idle and light throttle.
So by adding another resistor in series with the existing one this should bring the voltage down and thus reduce the flow rate on idle??
If so should i go for another resistor the same as the stock one allready fitted?
Ive allso noticed that the stock fuel pump resistor gets bloody hot. cheers
The following link on the GTO / Stealth 316 site is all about fuel pump upgrades:
http://www.stealth316.com/2-fuelpumpguide.htm
The FC pump isn\'t listed, but from my measurements, it flows less than an FD pump which is in the comparison, and also draws a little more current.
Basically - at 40 psi (stock idle pressure) and 13V the FC pump would draw around 10+ Amps compared to the 7-8 that a Walbro would use.
When Mazda sized the resistor for the fuel pump they had that higher current draw in mind, and the resistor is designed to drop the voltage to around 8-9 volts. This resistor only drops the Walbro to about 10-11 volts (depending on wiring quality in the car), and hence the drop isn\'t as much. Couple this with the fact the pump will flow a lot more at this voltage / pressure than the stock (at 13v comparison for Walbro and FD pump is 265 to 229, but this would be even worse for the FC pump comparison).
So the problem is two fold:
1) The Walbro flows more at any given voltage
2) The more efficient pump drops less current, so would effectively run at a higher voltage on the same wiring / resistor settings as a stock pump.
You could try running 2 stock resistors in series - that should bring the voltage down and help reduce that difference - the added advantage is that the resistors will only have 1/2 of the power dissipated in them, so run less hot :)
I think ill go for that first then and see if it brings the mixture ratio down abit. You were saying that these resistors arnt used under load or boost?
Last noob question to conect the two resistors together i assume id unplug the origional and just splice the other resistor into the existing resistors wiring?
Im guessing it doesnt matter which wire id cut into on the origional resistor then?
Quote from: Adam fc;743571I think ill go for that first then and see if it brings the mixture ratio down abit. You were saying that these resistors arnt used under load or boost?
Last noob question to conect the two resistors together i assume id unplug the origional and just splice the other resistor into the existing resistors wiring?
Im guessing it doesnt matter which wire id cut into on the origional resistor then?
Under load the relay contacts short out the resistor, so the pump sees full voltage (in actual fact it\'s fail safe, as the relay is open when on light load/cruise leaving the resistor in circuit, if the relay were to fail, the pump sees full 12v). Pin 1K on the ECU is grounded to operate the relay under idle/light load/cruise - at all other times this is floating (normally pulled to 12v by relay coil).
Yep - the resistor is mounted on that angle bracket that sits behind the drivers headlight - there\'s a relay and resistor - just cut either wire to the resistor and wire the additional one in there - one wire to each end of the cut. This mod shouldn\'t be done on the stock pump, as it will not get enough voltage !
The service manual says the resistor is 0.7-0.9 Ohms - so I suppose you could substitute this for a resistor of 1.5-1.8 ohms of suitable power if you wanted to substitute your own resistor in there.
Power required (based on 10A current worse case) would be IxI*R which is 10x10x1.5 or 150W !!
Going by the walbro current of 8A it would be 8x8x1.5 =96W
You can get close by using a pair of these 3.3 ohm 50W resistors in parallel from RS:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0160916
or better still allow for some safety margin and use three 4.7 ohm 50W in parallel:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0158323
Also your stock ECU will more than likely make it run richer than your aftermarket one. I swopped mine around on my old white FC and the aftermarket one was far better.
Cool! well i think ill run my existing resistor along with a 1.8 ohm resistor thrown in and see what results i get from that. Failing that ill run three 4.7ohm resistors.
Im thinking that 70% of the overfuelling is down to the 255lph pump and 30% is probably down to a bad tune or worn sensors as shes always run abit rich but nothing to worry about.
I have tried running both ecu\'s but the afm doesnt seem to indicate any difference. Saying that i havent got a wideband lambda sensor so i only get a vague indication of how rich or lean shes running.
I think my aftermarket ECU is mapped for all my mods so i think ill try and put it through the mot with the aftermarket one and see if there is any change in how rich the mixture is at idle.
My FC has the same pump, CO and PPM are MOT passes with my air pump, mine runs stupidly rich/off the scale lean on the O2 due to the air pump on idle, let me know what works and I will probably do that with mine!
Yeah im interested in as to how much introducing extra resistance into the power supply to the pump will affect it. Its going in for an MOT on tuesday!
My mates got a cat that he usually welds in for MOT\'s if a car has high emissions then takes it out after lol.
Mine isn\'t running any cat at all, CO is 0.18% I think :) mine has no issues on MOT day, just a massive health risk when idling
Okay, well i got my 1.8 ohm resistor today and wired it in with the existing resistor which came out with a total resistance value of 3.0 ohms lol.
I connected it back up and started the car which seemed to be running allot leaner on the gauge but was missing all the time and you couldnt put any throttle on apart from WOT other wise it would just stall. Anything over 4000rpm was fine as i assume that was the pump seeing full voltage.
Im guessing the wiring to my pump must be dropping quite allot of voltage then as it seems the 1.8ohm resistor along with my standard resistor was causing to much resistance and not enough to power the pump?
Could try a lower resistantce resistor and see how we get on with it.
Quote from: Adam fc;744526Okay, well i got my 1.8 ohm resistor today and wired it in with the existing resistor which came out with a total resistance value of 3.0 ohms lol.
I connected it back up and started the car which seemed to be running allot leaner on the gauge but was missing all the time and you couldnt put any throttle on apart from WOT other wise it would just stall. Anything over 4000rpm was fine as i assume that was the pump seeing full voltage.
Im guessing the wiring to my pump must be dropping quite allot of voltage then as it seems the 1.8ohm resistor along with my standard resistor was causing to much resistance and not enough to power the pump?
Could try a lower resistantce resistor and see how we get on with it.
Try just the 1.8 ohm on it\'s own in place of the existing one - 3 ohms is too much resistance - which is why it\'s missing.
What power rating is the 1.8 ohms?
Cool okay sorry i misread your previous post. The 1.8 ohm resistor is a 50w model.
Once i had the two resistors wired up the 1.8 ohm resistor was bloody hot to the point where it was starting to create a burning smell. Would a 50w 1.8ohm resistor be safe to run on its own due to the amount of heat it was generating? Cheers
Quote from: Adam fc;744538Cool okay sorry i misread your previous post. The 1.8 ohm resistor is a 50w model.
Once i had the two resistors wired up the 1.8 ohm resistor was bloody hot to the point where it was starting to create a burning smell. Would a 50w 1.8ohm resistor be safe to run on its own due to the amount of heat it was generating? Cheers
Probably not - You want 100W or 150W of resistor.
I\'ve think I\'ve got a spare stock resistor if you want to try 2 of those in series - that will more than handle the power and will certainly be better than running just the one resistor. I have a look for it tomorrow evening (got no light in my garage :) ).
If you want to make a resistor \'pack\' up with 50W resistors - you\'ll need 3 4.7 Ohms in parallel (4.7/3 = 1.56) and they would handle 150W.
Cool well thanks for the offer but ive got another standard resistor in the post coming my way soon so ill splice that one in and see what kind of results i get.
\'\'If\'\' it passes its MOT tomorrow ill take it back with the twin resistor set up and get them to measure the HC and see if has reduced or not.
Failing that ill move onto the burning of oil lol.
Well an update on the emission\'s issue! We found a massive air leak just after the afm on the turbo inlet trunking and a load of burnt out wiring in the ecu loom.
Once these problems had been sorted the car\'s HC count was down to 800ppm!
Thats without the extra resistor in the circuit but id like to give the extra resistor a go to see if it can better the emissions and running of the car on idle and light throttle.
Ill aim to introduce another stock resistor and then get my mate the MOT tester too do a quick emissions check on her to see what we get once shes all MOT\'d up!
Cheers for all the help chaps! specially Prof on this difficult issue! :)