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lambda measurement

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I do wonder if someone here has installed a wideband lambdasonde and some kind of simple measurement to keep an eye on the correct fuel-air mix in different conditions, loads,enginespeeds etc. on a NA dellortho car. (esprit S1,S2,S2.2,S3).

 

The point is. To have a correct view on the fuel -air mix , one has to have a lamda for each cilinder?

I have a stainless steel (SJ) exhaust collector; Where should the bung be welded in for a correct reading? ( Distance from the engine)

Any thoughts or experience on this subject?

 

The measurement is simple enough, with a wideband sensor and a small controller.

But is it worth the money and effort to do it?

 

Geert

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Hi Geert. Interesting question, I have been discussing the tunning of my S2.2 with a local engine tuner. He is very keen to do just what you ask about. The proposal is to weld a boss into the collector and attach the installed sensor to a simple led display on the dash, benefit being that you can keep an eye on the air fuel mix as you drive along. This is of course the side benefit the real purpose of the exercise being to enable a very accurate read of the fuel air mix during the tunning process (on the rolling road) when a sophisticated sensor and measurement equipment would be connected. I understand that this is a much more accurate method than pushing a probe into the tail pipe and more suited to the sensitive measurement equipment. We may get around to doing this in the coming weeks. I'll let you know how it goes. Cheers john.

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Been looking/thinking about this for a while, but not much happened yet. This is useful: http://wbo2.com/lsu/lsuworks.htm

 

Also, the Bosch chip to control the sensor is available, I was planning to buy a few to play with, have got pricing and availability. It is a CJ 125 series, BOSCH part.

 

Can buy a complete test unit, but I was thinking of building a custom one and putting one in the car for on the road analysis and readings.

 

The mounting of the sensor is reasonably sensitive, so has to be about 600-900mm down the exhaust pipe I seem to recall. As you suggest, weld a bung to the exhaust.

 

cheers, Clive

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Hi Shaman, Clive

 

I look forward to your reports regarding this.

The thing is , with our old fashioned dellorto carburator cars ( love them), where do you mount the sensor ? cyl 1, 2 ,3 or 4 ,or maybe just behind the collector ?

The accellerator pumps may be different in the two carbs or the float hight is not the same in carb 1 and 2. So , with certain  jets installed, you have good readings in cyl1, while cyl 3 and 4 may be to lean.

With throttle bodies and fuel injection, this is no issue.

 

Geert

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You could always keep it simple and use a voltmeter set for the range, the heater doesn't need to be used in you case, it's there for quicker warmup of the probe on newer cars. In the '80s the O2 sensor they were using (cheaper too) had only one wire. This should be more than enough for what you plan to do.

 

Luc

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Luc, the sensor and electronics required is not simple, but the chip does all the hard stuff to make it pretty simple. The heater is critical, and must maintain the temperature accurately.

 

Just checked, need to place sensor about 1m from nearest exhaust valve. But for tuning purposes might be possible to place sensor mush closer and increase sensing accuracy.

 

I can't find the detailed specs, but it may well be possible to match the output to a cylinder, as I expect the response time to be pretty good, but that would need a cam position sensor too, or maybe a spark detector on each lead to indicate which cylinder is exhausting.

 

Does sound like an interesting project!

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Heaters were added only in mid '80s by the way, what I specified in the last post comes from a Bosch document...

Edited by Mesprit87

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The old style O2 sensor is quite narrow band, so probably not so good for this application. I read a description in a workshop manual which said the output in conjunction with the feedback loop(ECU) basically oscillated around the ideal point. The new wideband ones can give very good feedback on combustion, like the Bosch LSU 4.9

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I have bought the Innovative Motorsports MTX-L Wideband air/fuel ratio to be used as a permanent gauge.

http://www.innovatemotorsports.com/products/MTXL.php

It is indeed usefull, especial on a turbo charged engine.

The probe is to be used downstream after the TC.

For constant monitoring you can mount the probe in each runner just after the exhaust valve, due the the high temperature.

However, with well balaned carburetors, i will be pretty accurate on the air fuel ratio.

Haven,t installed it yet, but to be done for this season.

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That looks to be very interesting, and good value, thanks for that.

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In case of the NA stainless steel exhaust manifold from SJ sportscars, if the bung ( for the sensor) is welded in the collectorpiece where the 4 tubes come together, this is about 900cm to 1m from the exhaust port.

Would that be a good place, or is it preferred to choose 1 of the 4 cilinderexhaust tubes ? 

 

I think it is a good idea to have a controller with 2 out, just to have the possibility to connect a gauge and at the same time also a computer to register things or maybe in a later stadium going to a closed loop fuel injection.

 

Geert

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