Madinventions
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| posted on 24/12/09 at 01:05 AM |
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Wideband Lambda positioning
Here's an early pic of my exhaust layout on my Mojo.
The current engine is a Zetec SE 1242cc with a mighty 75bhp and I'm gathering the parts to change this to a 1600 Zetec SE with GSXR600 TBs and a
Megasquirt. I've got a Techedge wideband lambda sensor on the way to help with the tuning of the MS but the instructions for the WB kit states
that the sensor should be a fair way down the exhaust to prevent overheating issues and as you can see in the pic the boss for the Ford narrowband
sensor is right at the top of the manifold, with the cat bolted directly beneath it.
So, one option is to blank off the Ford boss and fit a new one further down the pipe and mount the WB sensor after the cat. I know this will affect
the readings, but by how much?
The only other alternative that I can see is to replace the entire exhaust system from manifold to tailpipe and use a silencer with an internal cat.
I've priced this up at around £530 so I'd like to avoid this if at all possible, although the more I think about it, the more I feel
it's the best course of action. Not very Locost though...
Anyone got any bright ideas?
Cheers,
Ed.
PS: I hope Santa brings me a welder...
PPS: The Mojo is currently registered and on the road so IVA will not be an issue, although the MOT in 2 years might be as the car is on an age
related P plate so will need the cat test.
[Edited on 24/12/09 by Madinventions]
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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prawnabie
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| posted on 24/12/09 at 01:26 AM |
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I would think it needs to be before the cat?
All the sensors I have seen after the cat give a pretty steady reading until somet is a miss.
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turbodisplay
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| posted on 24/12/09 at 08:45 AM |
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First i would say you could try to place where it is, the boss temp (thread) cannot exceed 500C(ish), actual sensor 750C.
Never fit after cat!
option 2 make or get made a threaded spacer so sensor is not in exhaust stream, will slow response but not by much.
Spacer will have fins to act as a radiator to disipate heat. Prob need to relocate sensor by 15- 20mm.
Darren
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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brianthemagical
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| posted on 24/12/09 at 10:27 AM |
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Will you not hsve a differnt exhaust with the new engine? Or is it the same setup. One poss is to make a nice tubular setup, sans cat, for day to day
use and then fit the cat system for MOT time. Can;t take more than 2 mins to swap them with so much space.
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fatbaldbloke
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| posted on 24/12/09 at 10:28 AM |
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As I recall the Innovate wide band sensor kit comes with details of a heat shroud to protect the sensor. It's like a cone that fits instead of
the washer that usually goes between the sensor and the boss. It's a bit like the collar you fit to a cat or dog to stop it scratching its
ears. 
I don't know if you can buy one ready made or have to make it. I'll see if I can find the paperwork over the christmas break and post a
picture.
[Edited on 24/12/09 by fatbaldbloke]
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Brommers
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| posted on 24/12/09 at 01:09 PM |
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I can't really see any sensible option other than getting new headers made up with a cat further down the exhaust system. Mind you, if
you're changing the engine to get more power, and swapping to ITBs, then using a cast iron manifold seems a bit counter-intuitive since I
can't imagine it'll do anything for the engine's power output. Probably worth the cash given the increase in power you'll get
from a decent exhaust.
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Madinventions
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| posted on 24/12/09 at 01:29 PM |
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Wow, thanks for all your advice guys!
I've found the details of the Innovate copper heatsink (basically a 100mm square copper washer) and found that they also do these bung extenders
(£60 each...)
Other extenders seem to be available so I think I'll do some Googling over Christmas. There does seem to be quite some debate about how much
venturi effect a bung extender would cause, but I expect that this is mostly conjecture. 
The new engine will have a different manifold to allow for the larger exhaust ports, but it's still a cast iron lump. There were a few 1600
Zetecs that had a tubular exhaust manifold that might work, and I'm also playing with the idea of using one of these with an inline cat such as
those from a Rover 400 series.
Ed.
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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sebastiaan
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| posted on 24/12/09 at 02:57 PM |
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Just stick it in the manifold; it's also there in the OEM setup and the sensor should be up to the job.
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MikeRJ
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| posted on 24/12/09 at 03:41 PM |
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Only one thing is certain, you can't fit it after the cat and expect it to give useful results!
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fatbaldbloke
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| posted on 25/12/09 at 11:31 AM |
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quote:
Just stick it in the manifold; it's also there in the OEM setup and the sensor should be up to the job
Remember that the OEM sensor is a narrowband lambda sensor and a considerably less sophisticated piece of kit than a wide band sensor, so likely to be
less sensitive to the ambient conditions.
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sebastiaan
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| posted on 25/12/09 at 06:27 PM |
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Yes, but have a look at where the widebands are in their OEM application; same place as a narrowband would be.
The often used LSU 4.9 is OK up to 930 deg C operation temp and 1030 deg C max.
See here: http://www.bosch-motorsport.com/pdf/sensors/lambda/LSU49.pdf
From that PDF: "Install at a point where the gas is as hot as possible."
Without exceeding above stated temperatures of course... On a 1.6 zetec SE you'll be OK when mounted in the manifold as per OEM.
[Edited on 25/12/09 by sebastiaan]
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sebastiaan
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| posted on 25/12/09 at 06:33 PM |
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quote:
Originally posted by sebastiaan
Yes, but have a look at where the widebands are in their OEM application; same place as a narrowband would be.
The often used LSU 4.9 is OK up to 930 deg C operation temp and 1030 deg C max.
See here: http://www.bosch-motorsport.com/pdf/sensors/lambda/LSU49.pdf
From that PDF: "Install at a point where the gas is as hot as possible."
Without exceeding above stated temperatures of course... On a 1.6 zetec SE you'll be OK when mounted in the manifold as per OEM.
And
[Edited on 25/12/09 by sebastiaan]
this document agrees.
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