Yet another MOT failure....emissions:(

Prof · February 18, 2011, 01:25:38 PM

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

pdtaylor18 · February 18, 2011, 01:43:08 PM

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.

Adam fc · February 18, 2011, 07:08:54 PM

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.

m1tch · February 18, 2011, 09:32:03 PM

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!

Adam fc · February 18, 2011, 11:31:41 PM

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.

m1tch · February 19, 2011, 11:22:29 AM

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

Adam fc · February 21, 2011, 08:42:50 PM

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.

Prof · February 21, 2011, 08:58:31 PM

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?

Adam fc · February 21, 2011, 09:17:44 PM

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

Prof · February 21, 2011, 10:22:10 PM

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.

Adam fc · February 21, 2011, 11:26:09 PM

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.

Adam fc · March 21, 2011, 05:55:23 PM

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!