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Improved cold weather running

NPS

NPS

Cruisin' Guzzisti
GT Contributor
Joined
Dec 11, 2008
Messages
262
Location
Churchdown, Gloucester, UK
I have a Breva 1100 which is fitted with wide-band lambda.
The bike runs ok in closed loop mode using the lambda signal to run around 14.7 AFR.
However, in open loop mode when warming up the engine runs rich at about 12 - 13 AFR. Below 8C the ECU never goes into closed loop mode. Between 8-10C it may take as long as 30 minutes to switch to closed loop mode.
In wide open throttle it goes to open loop and the AFR can drop to 11.

A solution that appears to work quite well is to place a 2400 ohm resistor in parallel across the inlet air temperature thermister located in the airbox. This fools the ECU to thinking that the air temperature is around 38C warmer. The result is that the ECU switches to closed loop within a minute or so of starting (could be longer to warm up more). In addition, the wide open throttle AFR is now around 12.5 - less lickley to hesitate as it did before being over rich. This due to hotter air being less dense and requriing less fuel.

I'm sure this has been done before but just thought others might benefit from my experience, especially in colder climates. To lessen the effect a resistor of 4k or 6k could be used for 28C and 20C, respectively.
 
There has been written before about this subject as you mentioned. For example in this Stelvio topic:
https://www.guzzitech.com/forum/topic.html?f=190&t=2170&hilit=air+sensor&start=30
There they talk about a resistor of about 20 kOhms. That resistence will only have influence to the lower temperatures as mentioned. When you use a resistor of about 5 kOhms, it will also influence the higer temperatures in my opinion. For example: an airtemperature of 20 degrees Celcius. The sensor resistance itself is 3.75 kOhms at that temperature. Resulting parallel resistance af 3.75 and 5 is 2.12 kOhm. The ECU thinks the airtemperature is about 35 degrees Celcius. In higher temperatureranges the influece will be more I think. Is this OK? Or should the resistance be about 20 kOhm as they mention?
 
In my area have done similar tweaking using a switched resistor to the engine temperature sensor. Leave the resistor out of the circuit when starting and the first few minutes, then switching it in after a couple miles. This makes a big improvement in P8 and 15M bikes in that they only ran in open loop. Engine temperature seemed to impact fuel mix more than air temperature. I'm not sure how much the closed loop sensor system would compensate for having a parameter lie to the ECU.
 
On my Breva I needed a low resistance of 2k4 in order to get a higher AFR. I dont think a 20k ohm resistor would make much difference as it adds about 8C at a temperature of 0C and 5C at 20C temperature.
 
These bikes are a pain in cold weather. Below 10C it takes about 10-15 miles on the open road to come of the cold running rich setting.
On my Breva 1200 it is returning approx. 25mpg (U.K.) during this period.
So for your daily commute a good portion of the ride will be a expensive one at todays fuel prices.

Surely Guzzi could resolve this. No bike I have had ever needed warming up for it to run properly over this distance.
My old BMW R1100s just had a manual throttle body lifter to increase revs for a few minutes but I never had to ride with it on. Even the old manual choke system was more fuel efficient, at least you could control when it went off.

Playing around with resisitors on the air/engine sensors plus a Fat Duc (which I have) should be unnecassary on a properly designed fuel injection system . Resolving one issue may not be good for overall running and certainly not for the warranty.
Maybe with todays strict emission targets water cooling will be the only way forward, look how quick a car temp. gauge goes to normal even in cold conditions.

I love the Breva but I do think the constant back firing and poor cold weather fuel economy could and should have been resolved during the design process and detracts from a otherwise nice bike.
 
davem said:
These bikes are a pain in cold weather. Below 10C it takes about 10-15 miles on the open road to come of the cold running rich setting.
On my Breva 1200 it is returning approx. 25mpg (U.K.) during this period.
So for your daily commute a good portion of the ride will be a expensive one at todays fuel prices.

Surely Guzzi could resolve this. No bike I have had ever needed warming up for it to run properly over this distance.
My old BMW R1100s just had a manual throttle body lifter to increase revs for a few minutes but I never had to ride with it on. Even the old manual choke system was more fuel efficient, at least you could control when it went off.

Playing around with resisitors on the air/engine sensors plus a Fat Duc (which I have) should be unnecassary on a properly designed fuel injection system . Resolving one issue may not be good for overall running and certainly not for the warranty.
Maybe with todays strict emission targets water cooling will be the only way forward, look how quick a car temp. gauge goes to normal even in cold conditions.

I love the Breva but I do think the constant back firing and poor cold weather fuel economy could and should have been resolved during the design process and detracts from a otherwise nice bike.
Click to expand...

Daven,

I pretty much agree. I also work on BMWs and they do have to reach a certain engine temperature before closed loop operation begins, but the warm up period is brief. Yes BMWs run lean and the early 1100s and 1150s did surge some but the dual plugging in later (2004) R1150 cured that issue. My wife's R1150RS was set up perfectly from the factory. To this day she gets better mileage than any of my Guzzis (although my 1100 Breva is only a mile or 2 per gallon less), but the BMW just isn't as much fun to ride from my point of view.
 
do we think the new o2 optimizer would be the hot ticket for this issue?
 
Guys,
The last couple of weeks I've been driving my Breva 1200 with a 10 kOhm resistor parallel to the oiltemperature sensor and one parallel to the airtemperature sensor. The fuelconsumption really has been improved by doing this. Before the bike used 1:13 (km/ltr), now the consumption is about 1:16 for short rides. On long calm rides its even better. So I think some resistors really do help.
Therefore I now made a more definitive solution. I made a construction with a connector and a plug. In warmer spring and summertimes I can pull out the plug in which the resistors are soldered to get the original situation and levels.
 
According to the spec sheet for the air temperature sensor increasing the resistance by 10k would at 10C actual
temperature fool the ecu into a temperature of -10C thus richening the mixture even more, or have I missed something here?
Regarding the oil temperature sensor you refer to, do you mean the engine temperature sensor fitted to the r/h cylinder if so the above also applies.
http://www.mmcompsys.com/product.php?id=140
 
@ davem:
Hello,
I think this is what you miss:
The resultant resistance of two parallel resistors can be calculated with the formula 1/Rv = (1/R1) + (1/R2) or
Rv = R1xR2 / (R1+R2)
I think you counted the resistors together.

Using the upper formula you will see that there is a considerable influence at low temperatures and almost no influence at high temperatures.
 
I'm open to any solution to get the best out of the Guzzi engine.
Regarding the cold weather fuel economy the problem has I see it lies with the engine temperature sensor which is designed to measure internal water temperature not placed next to a external surface in a plastic holder, hence the numerous threads to improve it's conductivity.
No doubt the Guzzi FI guy allowed for a bit of variation between external and internal engine temperature but in my opion it's a poor compromise hence the piss poor fuel economy in cold weather.
 
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