28 replies to this topic

[klivins]

Hi all, an advice / opinion please. A fresly rebuilt 1275 (now 1293 i guess) with HIF 44 and 266 cam. I have installed a lambda and AFR gauge for setup purposes, and playing with couple of needles i had in the carb prior the rebuild. On cruise sometimes, but not allways the AFR shows leaning out. Any ideas, what could cause this? Is it may be normal behaviour, as the throttle opens / closes slightly?

I will try to attach video I took of the gauge. It was taken on a cruising speed of about 90 - 95 kmh.

https://youtu.be/ANCZgmOAQTA

 

[Spider]

Where have you position your Lambda Sensor ?

[klivins]

The sensor is in the exaust next to the gear change mechanism, as the car has 'spider' exaust this was the first and most practical place to put it. 

Edited by klivins, 15 April 2021 - 08:46 AM.

[Ethel]

Could be worth double checking the wiring.

[klivins]

You mean for the sensor?

[Maccmike8]

My understanding, which isnt necessarily correct, the sensor wants to be as far from the manifold as possible?

 

From your video much of it is too lean so are you sure the carb/timing is adjusted correctly?

 

I also think on part throttle and when letting off, you naturally run leaner anyway.

[klivins]

Well, I sort of aimed for a bit on the lean side on cruise. What I can't have explanation for is: on constant speed and what feels like constant throttle opening it gradually gets very lean. Some time later on similar stretch of road it doesn't do that.

[sonscar]

Is it a wideband sensor and corresponding AFR gauge?or is it a narrowband sensor with approximate gauge?Have you a vacuum gauge to see if the manifold vacuum alters?Just a few thoughts.Steve..

[PoolGuy]

It’s a wideband, narrow only reads around 14/15. As for the video, how in sync is the sound? It’s always difficult with video to tell if the sound is a reflection of what the engine is doing as there can be a lag. An afr will always be changing unless you’re on a constant throttle, on a level road, even then there’ll be some small variation. Having said that, your cruise is too lean imo, mine only goes that lean when I lift off, at cruise on a straight, level road it’s around 16. 

[KTS]

if an air leak or fuel supply issue i would have thought you'd 'feel' it through the engine; change in engine note, faltering etc

 

maybe worth double-checking the AFR gauge installation to make sure all connections are correct and secure

[klivins]

Thanks. The engine feels fine up to AFR 16, after that it shows usual lean sort of spluttering (so to speak). 15.5 - 16 was what I was aiming at, so pretty pleased with the modified needle (so far). Am pretty confident the installation is good, as all the wiring is brand new, and the lambda is new as well. I will, hovewer check all of the connections again. 

What would the carb icing be like on the AFR gauge? The dashpot of the carb felt very cold on the touch after the drive, but not yet frosty. 

[ACDodd]

Thin that oil out in the dashpot it’s much to rich on acceleration.

Ac

[klivins]

Thanks AC. Will do!

[Ethel]

Yes, I mostly meant sensor wiring, is the sensor also facing down slightly so it doesn't gather condensation?

[ACDodd]

Is it a genuine Bosch sensor?

Ac