Lambda wiring mod
Discussion
Over the year's i've tried various things to improve low throttle stability (aka "shunting"). Bodies- bearing mods, pot mods, better tune / balance etc. Even tried a new coil pack etc (the latter made no diff btw). The body mods made the biggest improvement...got close to good, but when watching the consistency of the adaptaives at idle and at very low throttle opeings (@1500 rpm you can hardly see that you've moved the butterflies !) I realised I was wasting my time...you could change the reading from lovely and stable to +/-10% different just by a brief fast idle spell (2K-2.5K ish) and then release back to idle -> adaptives would hunt to a diffent point (and hence be wrong)...eventually returning to close to where they started (meaning several minutes of dodgey running). I've had several experiences in the past where after an M-way blast, then come off to a traffic queue, the engine wanted to die on light throttle application...only to correct itself a few minutes later (would idle fine but was clearly hopelessly lean as you pressed the throttle to creep forward)
Finally tried the lambda ground mod...what a difference. Stable, easy to drive at low revs, nice throttle pick up, predictability of throttle response after a long M-way stretch etc etc.
If you haven't had it done...its a no brainer.
Finally tried the lambda ground mod...what a difference. Stable, easy to drive at low revs, nice throttle pick up, predictability of throttle response after a long M-way stretch etc etc.
If you haven't had it done...its a no brainer.
2002
4 wire
Take the heater ground wires at the plug and separate from the common spliced ground
So 2x ground wires now join instead to a separate ground feed attached to the engine using one of the timing chest cover bolts as a pick up point
I took the crimps out of the connector to make a neat job but you could just as easily snip the 2 wires and re join them to the new feed
4 wire
Take the heater ground wires at the plug and separate from the common spliced ground
So 2x ground wires now join instead to a separate ground feed attached to the engine using one of the timing chest cover bolts as a pick up point
I took the crimps out of the connector to make a neat job but you could just as easily snip the 2 wires and re join them to the new feed
Just done mine, I will post a pic later. Sadly for me it came too late, the earth to the sensors had failed meaning I had no AFR control. This resulted in the lambda's burning out. Luckily I run decats so it didn't take the cats out too as I must have run for about 500 miles before I realised what the problem was!
As said above just cut the lambda heater ground that is spliced together in the early models style and connect it to the nearest solid engine ground. You don't have to connect it directly to the battery ground as the engine should have a good ground connection anyway. If this is not the case you would already have noted other issues as the ECU main ground is connected to the engine as well (bell housing bolt).
With separating the heater ground from the signal ground you will prevent "signal rushing" caused by the current of the heater coil.
With separating the heater ground from the signal ground you will prevent "signal rushing" caused by the current of the heater coil.
Check out the 4 wire Titania sensor wiring here
http://www.lambdasensor.com/main/mcolours1.htm
You need to splice out the wire from the white and ground it. I suggest using the battery -ve because this is the purest ground on any car, being the ultimate reference point for everything on the car not least of which is the alternator. It also acts as a giant smoothing capacitor for the alternator and engine meaning that the slightest resistance buildup on the engine ground could start to put noise on the sensor ground.
I take your point that if the ECU is grounded on the bellhousing, this is moot!
http://www.lambdasensor.com/main/mcolours1.htm
You need to splice out the wire from the white and ground it. I suggest using the battery -ve because this is the purest ground on any car, being the ultimate reference point for everything on the car not least of which is the alternator. It also acts as a giant smoothing capacitor for the alternator and engine meaning that the slightest resistance buildup on the engine ground could start to put noise on the sensor ground.
I take your point that if the ECU is grounded on the bellhousing, this is moot!
More precisely it's the engine loom ground. It goes to the ECU ground. If you don't trust me, follow the lead... or disconnect it and try to start the engine...
You are right, the battery - is best point to ground, but you have so many sensors in the engine, you cannot ground them all directly to the battery. That is why it is important to have a good connection from battery ground to the engine.
You are right, the battery - is best point to ground, but you have so many sensors in the engine, you cannot ground them all directly to the battery. That is why it is important to have a good connection from battery ground to the engine.
Well you shouldn't be adding grounds to any of the sensors from the engine because if the main engine ground drifts even slightly, stuff like the starter motor, alternator, ignition etc will start putting current via the sensors - not good.
The problem with the lambda sensors is that as standard, their heaters are grounded via the sensor ground, and because of the current they draw, it's enough to pick up the ground potential at the ECU, which in turn results in a particular problem with the way the lambdas are (almost uniquely from what I've read) implemented on these engines.
The problem with the lambda sensors is that as standard, their heaters are grounded via the sensor ground, and because of the current they draw, it's enough to pick up the ground potential at the ECU, which in turn results in a particular problem with the way the lambdas are (almost uniquely from what I've read) implemented on these engines.
Hey John...interesting
After I called you pre-xmas it set me thinking about why the engine was running like a dog after the m-way blast...and lambda mod came to mind. Well, fingers crossed, no repeat performance since re-wiring
I looked at the fuel pressure regulator as we discussed but realised the way its set up is just plain wrong...regulator is supposed to see the vaccuum from the *inside* of the buttefly to allow more return to the tank at low throttle opening => big differential pressure across injector would over fuel otherwise (in theory). But the tiv has the vac pipe to the air box i.e. outside the butterflies => I reckon that will do diddly squat. So I decided to leave well alone and checked the wiring mod first
Looks like it was the right call.
After I called you pre-xmas it set me thinking about why the engine was running like a dog after the m-way blast...and lambda mod came to mind. Well, fingers crossed, no repeat performance since re-wiring
I looked at the fuel pressure regulator as we discussed but realised the way its set up is just plain wrong...regulator is supposed to see the vaccuum from the *inside* of the buttefly to allow more return to the tank at low throttle opening => big differential pressure across injector would over fuel otherwise (in theory). But the tiv has the vac pipe to the air box i.e. outside the butterflies => I reckon that will do diddly squat. So I decided to leave well alone and checked the wiring mod first
Looks like it was the right call.Sorry, posted that a bit quick from my phone. I should have written:
On the AJP engines, the vacuum feed to the fuel pressure reg does little else than adjust for a blocked air filter. On my Cerb, it's left off altogether.
On a forced induction engine, this would simply not work, but on a naturally aspirated engine, it can be mapped around. It jus tmeans the injector duty is even shorter at idle and light throttle than it might otherwise be
There is no way to reliably get one "manifold vacuum" value which is why the engine isn't mapped by manifold pressure either but has to resort to throttle position with a correction value, and even that system has redundancy.
What puzzles me is that the fuel pressure regulator also acts as a barometric adjustment, so why the engine management system maintains the need for a MAP sensor I don't know. Anyone?
On the AJP engines, the vacuum feed to the fuel pressure reg does little else than adjust for a blocked air filter. On my Cerb, it's left off altogether.
On a forced induction engine, this would simply not work, but on a naturally aspirated engine, it can be mapped around. It jus tmeans the injector duty is even shorter at idle and light throttle than it might otherwise be
There is no way to reliably get one "manifold vacuum" value which is why the engine isn't mapped by manifold pressure either but has to resort to throttle position with a correction value, and even that system has redundancy.
What puzzles me is that the fuel pressure regulator also acts as a barometric adjustment, so why the engine management system maintains the need for a MAP sensor I don't know. Anyone?
3 wire sensors stay as they are. The 4 wire sensors benefit from the earth as the ECU earth is on the back of the block and the lambdas are "a long way" from that earth point on a thin wire linked into the loom. By doing the earth mod and earthing with a shorter link to the block you remove the noise and give a cleaner reading for the ECU. The lambdas generate a very small voltage so any interference causes problems.
J
J
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