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 Slow to get to normal mixture

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lcjohnny
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PostSubject: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Fri Jul 23, 2021 4:38 pm

Hi all
and specially map specialists like Mark

My GRiSO seems to stay on the rich starting mixture for about 40 min or 30 miles.
I am judging by the way that the dispalyed fuel consumption starts to drop at about 30 miles ( at 1 to 100m asl and in UK temps 11ºc to 28ºc )

This seems a long time to run on the enriched mixture.
Back when there used to be chokes on things called carburettors the longest you needed to use them was 2 miles or 10 minutes.

Has anyone experimented with reducing the length/time of the enriched period?

Advantages of shortening the enriched period might be
1) reduced bore wear through less petrol to wash oil away
2) warmer cylinder heads (rich mixures run cooler)
3) less fuel pollution of the lubricating oil
4) longer range through less fuel wastage
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beetle
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Fri Jul 23, 2021 4:50 pm


The warm-up period lasts for 2000 engine revolutions. That's it. No more.

If you're engine is running too rich for a long period, you might want to check your intake temperature sensor, or the engine temperature sensor.





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lcjohnny
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sat Jul 24, 2021 3:52 am

Thanks Mark that is very useful

I guess i could assess the responsiveness of the engine temperature sensor by startign from cold and watching the reading in Guzzi Diag? It gets above 60ºc in about 5-10 min.


Is the intake air temperature sensor the external one in the little rubber hood or is there one in the airbox? It doesn't show on the parts manual

I had better find the sensors and clean the contacts to start


Last edited by lcjohnny on Sat Jul 24, 2021 4:27 am; edited 1 time in total (Reason for editing : thought a bit more)
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beetle
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sat Jul 24, 2021 4:21 am


Intake sensor is on the right side of the airbox, near the front of the lid.

Engine sensor is on the inside of the right cylinder. It's a tank off job.




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voulga77
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sat Jul 24, 2021 11:21 am

Cracked engine temp sensor holder has caused me trouble in the past.
Check that.
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lcjohnny
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sat Jul 24, 2021 11:49 am

Thanks both - the air temperature sensor looked dirty on one side but undaged - i wiped the dirt off carefully and refitted - the wires and plugs are in good condition.
Mark do you have any service information on that sensor - resistance maybe?

The engine temp sensor shows a consistent response when I set CO trim - up to 67ºc - i have had it up to about 98ºc.

Really want to be able to identify a fault before I lash out £75 to £90 on a sensor Sad


Last edited by lcjohnny on Mon Jul 26, 2021 3:16 pm; edited 1 time in total
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beetle
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sat Jul 24, 2021 3:33 pm


From the SM.

Intake sensor:

[You must be registered and logged in to see this image.]


Engine sensor:

[You must be registered and logged in to see this image.]


The ETS is also affected by air cooling. That's silly extension/holder that voulga77 mentions makes it stick up too far (IMO). Engine temperature while stationary can differ quite a bit from engine temperature at speed.



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lcjohnny
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sun Jul 25, 2021 5:53 am

Thanks Mark
the version of the pdf manual that i have wont allow word searches or bookmarks so it takes ages to find the bits I want to look at even when i am expecting the words that Guzzi use to describe stuff Smile

The Intake Air temperature sensor appears to be a ntc thermistor 'bulb' type.
According to this site hella IAT sensors they will show faults if dirty so I am hoping that the greasy dirt that i wiped off it was the problem - gonna check it against the table from the manual and then take it for a ride.

Regarding the head temperature thermistor - has anyone tried filling the hole with aluminium dust to get better contact with the thermistor tip?
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Evilgarfield
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sun Jul 25, 2021 6:49 am

Wouldn't thermal paste work better?
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voulga77
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sun Jul 25, 2021 10:17 am

Evilgarfield wrote:
Wouldn't thermal paste work better?

There's no thermal paste for such high temperatures.
Have tried copper paste, but seems to drip off the bottom after a while.
Perhaps aluminum foil is a good solution.
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lcjohnny
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sun Jul 25, 2021 11:11 am

I checked resistance of the air temperature sensor from -20º to 30ºc it matched the table pretty well.
Put it back cleaned and the mpg is now high for the firse 2-3 miles and then drops to the running mpg.

To get an even tickover i was running the CO trim at -10 but I wonder if the dirty temperature sensor was fooling the ecu into running the wrong mixture requiring that -10 correction?
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Evilgarfield
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sun Jul 25, 2021 11:22 pm

voulga77 wrote:
Evilgarfield wrote:
Wouldn't thermal paste work better?

There's no thermal paste for such high temperatures.
Have tried copper paste, but seems to drip off the bottom after a while.
Perhaps aluminum foil is a good solution.

What temps are we talking about 350°C thermal paste is not too hard to find. 200°C is pretty generic. If i remember correctly we have 1200°C thermal paste at work.
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voulga77
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Sun Jul 25, 2021 11:27 pm

I remember when I was looking for it was only able to find thermal paste for cpu. 100 degrees max.
200 degrees would be fine. Can you appoint a product?
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lcjohnny
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Mon Jul 26, 2021 1:00 pm

Looks like someone has used thermal paste on my sensor but there is not much evidence that it was in contact with the housing.

[You must be registered and logged in to see this image.]

The bore
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The tip
[You must be registered and logged in to see this image.]


I note there is only 1mm gap between the end of the sensor and the end of the bore.
Have wrapped the sensor tip and body in aluminium foil to improve contact or at least reduce that air space.
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voulga77
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Mon Jul 26, 2021 11:21 pm

Wow, the cast holder of the 8v is a lot better that the bakelite the 2v has
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Oz1200Guzzi
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Tue Jul 27, 2021 12:03 am

You could just use a good quality grease...
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lcjohnny
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Tue Jul 27, 2021 12:28 am

I am just glad no one mentioned the corrosion in there cheers
I have cleaned and touched up what i could but without a proper strip and rebuild it all looks the worse for 12 years of uk rain and roadsalt.

I bet the Australian and US bikes look better.

Jon
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Evilgarfield
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PostSubject: Re: Slow to get to normal mixture   Slow to get to normal mixture Icon_minitime1Tue Jul 27, 2021 1:43 am

voulga77 wrote:
I remember when I was looking for it was only able to find thermal paste for cpu. 100 degrees max.
200 degrees would be fine. Can you appoint a product?

Some CPU pastes claim up to 300°C working range like the thermal grizzly kryonaut

Or you could go for something like that
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