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O2 Sensor Location

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I have a Phoenix 3-2-1 manifold on my TR6, my O2 sensor bung is fitted in the 12 O'clock position on the joint where the two pipes become one and then the single pipe runs to the rear. I am using a new Spartan controller & Bosch 4.2 sensor, the readings are a little erratic and Emerald commented on this when they remoted into my ECU. I'm happy to buy a new sensor to see if that improves things, however, I'm wondering if I should perhaps use an extension to take the sensor out of the direct stream, what do others do?

Ian

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Presume you have a 6-2-1?    I have a 6-3-1, with the sensor mounted at three o'clock on the 3-to -1 collector, the equivalent position to yours.   Its at three o'clock for lack of headroom, but that will stop condensation gettongbto.it, which is the objctive.

This is the optimum position, in the had stream of all the ports, but near enough to be kept hot enough to work.   If your readings are erratic, then perhaps the two streams are not mixed enough.  A small.mixing baffle in the collector?   Or insert the sensor further into the pipe?

 

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Hi,

 I used a couple of  4.2 sensors. the 4.9 is superior. 

https://www.ecotrons.com/accurate_lambda_meter/bosch_lsu_49_is_superior_to_lsu_42_sensors/

I have an LC1 & LC2 stashed away somewhere; they never ran good for any length of time. Running the type with gauge & 0-5VDC o/p to ECU.

Air getting in thru joints? Clean supply Voltage & common clean ground?

I bought a new Bosch 4.9 off EBay for around £25.00. From China. My present expensive sensor is has started to read continuously excessively rich will only go weak on high rpm under decel.

Cheers,

Iain.

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If I’m understanding right the sensor position sounds ok.

Ian raises some valid points though my LC-1 has actually been pretty faithful. Sensor failed a couple of months back but it’s done 10 years.

To be clear, do you have the Spartan 1 or the Spartan 2 which has now superseded it? Former uses the 4.2 sensor and the latter the 4.9

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Thanks for the responses chaps:

I have a Spartan 2 so a 4.9 sensor. Today I connected up my LM-2 with a new 4.9 and put that in the tailpipe, its reading were jumping around too so the Spartan might well be reading correctly. I had screwed up the Spartan wiring, I had it going to a permanent live rather than switched however, I have changed that but no difference. The ground isn't common, however, I ran a wire to the ECU ground and it made no difference, the other ground is connected correctly to the ECU. I have removed the TBs now and the manifolds, I am going to fit a thicker gasket and spray some instant gasket on it to try and improve the seal, it's certainly difficult to get at some of the lower nuts with the Phoenix manifold.

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Hi,

 So you believe the reading to be factual & have a possible air leak?

It's erratic it all loads and RPM's?

Cheers,

Iain.

 

 

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38 minutes ago, spitfire6 said:

Hi,

 So you believe the reading to be factual & have a possible air leak?

It's erratic it all loads and RPM's?

Cheers,

Iain.

 

 

I haven't checked when on the road Iain, it's certainly erratic at all RPM's in my garage. One of the manifold studs had partially stripped, I'm suspecting there was a leak there, I have obviously ordered a replacement. I'm also going for a thicker gasket.

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Reading this again..... I presume you mean it's a 6-3-1 manifold?  And the sensor is positioned in or just after the 3-1 collector?

On a Vit/GT6 Pheonix 6-3-1 the collector is detachable via simple slip-joints and is notorious for leakage at that point.  I've a feeling that the TR6 and saloon versions are one piece and welded at that point?

Does sound like you have a leak somewhere though I would have thought you would hear the blow if it is enough to cause issues.....

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Yes Nick, it’s a 6-3-1 and the sensor is on top of the collector. The collector itself isn’t removable, it’s part of the manifold and the joint is a few inches after the collector. I certainly don’t hear any blow from this end. The inlet manifold gasket was intact, there is a thickness discrepancy between both manifolds, I have attempted to address that with a blob of weld being added to one end of the manifold clamps and that being placed against the slightly thinner inlet manifold flanges. I’m not completely happy with the studs mounting the TB’s, I have a Racestorations inlet manifold which came with imperial studs, Jenvey supply metric bolts, I’m using the supplied studs but they aren’t threaded all the way and I’ve had to use washers to take up the slack. I’m going to an engineering works today to confirm the stud size, I’ll then see if I can order some appropriately sized socket headed bolts to see if that improves the mounting.

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It's a 6-3-1 after all?  Good man!  6-2-1s don't work as resonators.

As this  IS a resonator, the impulses will be 'bouncing' from the collector to the inlets and back, with the corresponding pressure waves that apply additional suctionthat aids ectraction from the ports.    Which will therefore be doing the same at the collector, and possibly sucking in air, if that slip joint isn't a perfect fit.

Suggest putting a longer tail on the collector, so that the joint with the tail pipe, currently " a few inches after the collector" is further away from the sensor.   Then any internal plume of air cannot reach the sensor.

John

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56 minutes ago, JohnD said:

It's a 6-3-1 after all?  Good man!  6-2-1s don't work as resonators.

As this  IS a resonator, the impulses will be 'bouncing' from the collector to the inlets and back, with the corresponding pressure waves that apply additional suctionthat aids ectraction from the ports.    Which will therefore be doing the same at the collector, and possibly sucking in air, if that slip joint isn't a perfect fit.

Suggest putting a longer tail on the collector, so that the joint with the tail pipe, currently " a few inches after the collector" is further away from the sensor.   Then any internal plume of air cannot reach the sensor.

John

Hi John, the joint is downstream of the collector, I can’t see that a leak there would allow any air to move in an upstream direction with the engine running, surely the exhaust gas pressure would push the incoming air from a leak towards the tailpipe?

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Iani,

The whole point of a 6-3-1 is to allow the pressure pulses from each port to resonate in the primaries, at a certain small rev range.      Those pulses are biphasic, they go positive and negative.   See the red line below, and the dark blue, cylinder pressure.  EVO = Exhaust Valve Opening.  Ignore the light blue line, it's intake port pressure:

Intake Port, Exhaust Port and In-cylinder Pressures with Effective Tuning

 

The length of the primaries allows that pressure wave to resonate at a certain rev range, which will amplify the pulse, and reflect it back to the other port in the pair where it will arrive just in time to assist scvenging the other post - and vice versa.

The pressure pulse must go on down the secondaries to the  collector, where it could have a transient negative component big enough to entrain air through a leak, whoch if close enough to the sensor could make it erratic.

This might be shown by the error being dependant on engine speed.  I'd expect it to be worst at the resonant speed, which with 15" prinaries is 4-5K.  Try that?

JOhn

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1 hour ago, JohnD said:

Iani,

The whole point of a 6-3-1 is to allow the pressure pulses from each port to resonate in the primaries, at a certain small rev range.      Those pulses are biphasic, they go positive and negative.   See the red line below, and the dark blue, cylinder pressure.  EVO = Exhaust Valve Opening.  Ignore the light blue line, it's intake port pressure:

Intake Port, Exhaust Port and In-cylinder Pressures with Effective Tuning

 

The length of the primaries allows that pressure wave to resonate at a certain rev range, which will amplify the pulse, and reflect it back to the other port in the pair where it will arrive just in time to assist scvenging the other post - and vice versa.

The pressure pulse must go on down the secondaries to the  collector, where it could have a transient negative component big enough to entrain air through a leak, whoch if close enough to the sensor could make it erratic.

This might be shown by the error being dependant on engine speed.  I'd expect it to be worst at the resonant speed, which with 15" prinaries is 4-5K.  Try that?

JOhn

I’m still running this engine in John, not going near 4.5k RPM just yet :-) Once I refit the TB’s this week I’ll see what the AFR looks like, if it’s still erratic then I’ll look at the exhaust.

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4-5K   Four to five thousand rpm.

Ok, I'll be most ineterested to know what you find!

Good luck!

John

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Hi,

 Search for this on ebay:

0258017025 Oxygen Sensor Lambda Sensor 5 Wire 17025 Lsu 4.9 For Bosch Denso zv

Around £20. I have bought one but not tried yet, so cannot say if they are any good! Hope so as if I have to replace every year to get a working one happy days!

Cheers,

Iain.

 

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On 12/2/2019 at 10:36 AM, iani said:

Hi John, the joint is downstream of the collector, I can’t see that a leak there would allow any air to move in an upstream direction with the engine running, surely the exhaust gas pressure would push the incoming air from a leak towards the tailpipe?

You would think so. But pulses of gas & diameter changes can induct outside air to the mix. Not suggesting this is the cause, but saying it is possible.

Cheers,

Iain.

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13 hours ago, spitfire6 said:

Hi,

 Search for this on ebay:

0258017025 Oxygen Sensor Lambda Sensor 5 Wire 17025 Lsu 4.9 For Bosch Denso zv

Around £20. I have bought one but not tried yet, so cannot say if they are any good! Hope so as if I have to replace every year to get a working one happy days!

Cheers,

Iain.

 

I've ordered one, worth a go at this price.

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Hi Ian,

I have a TR6 with Emerald EFI and a Cannon inlet manifold, and after-market exhaust manifold, complete with a Lamda probe.

1. The thickness of the inlet manifold flange, will be thicker than your exhaust manifold, no doubt. The issue here is, when you bolt it up to the head, it will not be flush, due flange thickness. The only way to address this, is to relieve metal from the flange in the areas where your exhaust toggles fit, to a similar thickness to your exhaust manifold.

In addition, the after market Payen inlet manifold gaskets available, are not the best quality. They are not that strong with regards to material, and after so many months start to deteriorate and break down. I have seen this for my own eyes.  Bastuck in Germany do an excellent quality item, that is exceptional high quality. Part number: MD9TR6. 7.15EUR.

The air leak, as perhaps mentioned above, will affect your AFR reading for sure. 

Good luck.

 

 

Cheers.

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15 hours ago, spitfire6 said:

Hi,

 Search for this on ebay:

0258017025 Oxygen Sensor Lambda Sensor 5 Wire 17025 Lsu 4.9 For Bosch Denso zv

Around £20. I have bought one but not tried yet, so cannot say if they are any good! Hope so as if I have to replace every year to get a working one happy days!

Cheers,

Iain.

 

Hello All

              I wonder how long they will last?  

The best price I found for a Bosch one was about £60!

Roger

 

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3 hours ago, rogerguzzi said:

Hello All

              I wonder how long they will last?  

The best price I found for a Bosch one was about £60!

Roger

 

The do seem to be something of a consumable, the Bosch one supplied by Innovate only lasted me a couple of years, I'll see how it goes.

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4 hours ago, TRTOM2498EFI said:

Hi Ian,

I have a TR6 with Emerald EFI and a Cannon inlet manifold, and after-market exhaust manifold, complete with a Lamda probe.

1. The thickness of the inlet manifold flange, will be thicker than your exhaust manifold, no doubt. The issue here is, when you bolt it up to the head, it will not be flush, due flange thickness. The only way to address this, is to relieve metal from the flange in the areas where your exhaust toggles fit, to a similar thickness to your exhaust manifold.

In addition, the after market Payen inlet manifold gaskets available, are not the best quality. They are not that strong with regards to material, and after so many months start to deteriorate and break down. I have seen this for my own eyes.  Bastuck in Germany do an excellent quality item, that is exceptional high quality. Part number: MD9TR6. 7.15EUR.

The air leak, as perhaps mentioned above, will affect your AFR reading for sure. 

Good luck.

 

 

Cheers.

Thanks Tom, unfortunately they aren't the easiest to buy from online, I'm not going through this nonsense of someone calling me to take card details. I've just fitted a thicker gasket from Revingtons this afternoon, the idle has improved and the AFR, although not constant, is certainly not quite as wild as it was before. I will check the exhaust joints over the weekend and see if there's any leakage through there.

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