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Air Fuel ration

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Air Fuel ration
Nick Mayne Offline
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#1
28-06-2022, 12:47 PM
For my A7 pepped up engine I have an SU carb with a needle modified by Pigsty Racing by abrading the profile in a lathe. The mixture still smells rather rich so does anyone know of an inexpensive lamda sensor and appropriate handheld gauge so I could check the A/F myself? I do have a plugged threaded inset. Getting a bit sophisticate I know but just interested.
Thanks, Nick
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Alan Offline
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Location: Cheshire
Car type: Race Ulster, 1926 Special, 1927 Chummy, 1930 Box
#2
28-06-2022, 04:37 PM (This post was last modified: 28-06-2022, 04:37 PM by Alan.)
All you really need is a wide band lambda sensor and a voltmeter that reads accurately in the 0 to 1volt range. Some sensors have a heating arrangement others don’t, take your pick - I use a heated one but you don’t need to. Calibration charts are available if you Google for it.
Alan Fairless
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Charles P Offline
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#3
28-06-2022, 05:15 PM
Alan is right but I'm lazy. I bought a new orphaned lambda sensor for tenner and one of these AFR meters. http://www.dtmpower.com/fuelmeter
Works well but unless you intend to keep on trying to change things you may find just paying a rolling road is better value

Charles
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Nick Mayne Offline
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#4
28-06-2022, 08:22 PM
I did pay MAAS for a rolling road check several years ago but you don't get a chance to play around with machining needles etc. The problem with playing around with the SU needle at home is that it needs to be done with load and so, yes, I have realised you need a rolling road. I think I will give up that idea.
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Charles P Offline
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#5
29-06-2022, 12:33 AM
(28-06-2022, 08:22 PM)Nick Mayne Wrote: I did pay MAAS for a rolling road check several years ago but you don't get a chance to play around with machining needles etc. The problem with playing around with the SU needle at home is that it needs to be done with load and so, yes, I have realised you need a rolling road. I think I will give up that idea.

I reckon you need to find a better rolling road. Any I've used understood SUs and expected to adjust timing and swap needles/jets etc. Otherwise, what's the point?

The other, mildly sub-optimal option is the lambda/AFR meter and a nice uphill stretch of straight road. Expect to keep going back and changing settings. 

C
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Hugh Barnes Offline
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#6
29-06-2022, 08:23 AM
Nick - Regency Autos in Cambridge can provide Rolling Road services. The great Pete Baldwin has moved his facilities there and has been training up a successor. As I mentioned in another thread, Pete turned 31bhp into 42bhp at the wheels on my old Riley Nine in 90 minutes..

https://www.regency-autos.co.uk/

hth...
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