Author Topic: 2 questions  (Read 1482 times)

BlueMonday

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2 questions
« on: March 21, 2023, 05:13:40 PM »
Hello all,

I have 2 questions that I would appreciate answers to.

1) On start up, should I run the engine for a while before moving off?
With my previous car (Ford Focus) the owners manual stated that it was not necessary to warm the engine up before driving off, just drive easy for a few minutes. I could not find anything in the Honda Jazz owners manual although it is a thick book.

2) Is there a way to turn the boot light off without removing the bulb?
2019 Honda Jazz 1.3 i-VTEC CVT

Jocko

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Re: 2 questions
« Reply #1 on: March 21, 2023, 06:16:52 PM »
I never ever run an engine before moving off. I just start up and go.

embee

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Re: 2 questions
« Reply #2 on: March 21, 2023, 06:21:02 PM »
It certainly isn't necessary to "fully" warm-up an engine before driving off, indeed it can be detrimental to leave an engine idling from cold for prolonged periods (condensation and oil contamination etc).
However it is useful from a true cold start to allow the engine to run for long enough that any cranking/afterstart fuelling has time to ramp off and surfaces and items such as spark plugs get warm enough to minimise chances of cold fouling, this is typically only 20sec or similar.
A modern car (say less than 10yrs old) will be running stoichiometric fuelling (on feedback from the exhaust lambda sensors) within a minute from a cold start, possibly less.
It is advisable to drive gently while the engine warms up to normal operating temperature while components (bores/pistons) heat up and expand to normal running conditions. This will minimise mechanical wear and oil contamination and optimise the engine service life.

From a proper cold start I usually let the engine idle for around 20sec and then drive off gently. I live in a 30mph town limit so it fits with the principle nicely. By the time I exit the 30/40 limits it's pretty well up to temp.

jazzaro

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Re: 2 questions
« Reply #3 on: March 21, 2023, 09:56:56 PM »
Hello all,

I have 2 questions that I would appreciate answers to.

1) On start up, should I run the engine for a while before moving off?
No, you should run gently for about the double of the time you spend to see the blue cold temp light off in the dash. When it disappears, it means that the cooling liquid reaches 110F°, wait still some minutes and then the engine will be fully ready.
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2) Is there a way to turn the boot light off without removing the bulb?
No

BlueMonday

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Re: 2 questions
« Reply #4 on: March 22, 2023, 11:41:58 AM »
Many thanks for the answers, I appreciate it.
2019 Honda Jazz 1.3 i-VTEC CVT

degzi

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Re: 2 questions
« Reply #5 on: March 22, 2023, 01:48:56 PM »
Just drive gently when cold as others have said. Sitting idling doesn't really help anything on modern cars. The most essential thing is to make sure you change oil every 6 months to ensure the oil stays a decent viscosity to protect at startup.

I have always changed oil with a fully synthetic cheapo brand every 6months on every car I have owned and they always easily do well over 160,000 miles with no issues.

jazzaro

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Re: 2 questions
« Reply #6 on: March 22, 2023, 02:34:51 PM »
Just drive gently when cold as others have said. Sitting idling doesn't really help anything on modern cars. The most essential thing is to make sure you change oil every 6 months to ensure the oil stays a decent viscosity to protect at startup.
6 months? A modern sinthetic 0W20  oil can easily resist more than a year.

Lord Voltermore

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Re: 2 questions
« Reply #7 on: March 22, 2023, 04:49:06 PM »
Its generally recommended that you do not  warm up before moving off (once  your windows are clear of mist/ice. )The fuel  is better used to also gently travel a few miles/km.   But beware of immediately going onto a motorway etc  and driving at 130 kph. Stick to 80 kph/50 mph for a short time  until the engine has warmed up.    This is assuming the car doesnt run so badly when cold that you are a hazard to other traffic. In which case it probably needs mechanical attention.
Some boot lights may have a switch on the light itself. , with off meaning it never comes on. If there is no switch and for some reason you never want it to come on you might have to remove the bulb  (or fit a simple switch.)   If it stays on when the boot is shut  there may is a fault with the contact switch  on the boot surround. It may be corroded, and some types are adjustable by screwing a contact pin or plate   in or out.   (but check any  switch on the light itself is not three position  - off/ on when the boot is open/always on.More common on interior lights )
 
« Last Edit: March 22, 2023, 05:07:28 PM by Lord Voltermore »
  Trust a dog to guard your house  , but not your sandwich

TnTkr

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Re: 2 questions
« Reply #8 on: March 23, 2023, 05:11:52 AM »
Jazz engine doesn't really warm up when idling, at least not in any feasible time. Therefore as soon as the engine has started, it's ready to go. Generally I'd avoid using upper 1/3 of the rpm range as long as the blue temperature sign is on. After the sign is off I consider that manufacturer's intention was to express that full performance can be used.

But I must say, that from Nordic perspective any discussion of a cold start in UK sounds a bit amusing.  ;D

Regarding the oil change, I don't see any reason not to follow the maintenance schedule defined by Honda.

jazzaro

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Re: 2 questions
« Reply #9 on: March 23, 2023, 08:07:49 AM »
Jazz engine doesn't really warm up when idling, at least not in any feasible time. Therefore as soon as the engine has started, it's ready to go. Generally I'd avoid using upper 1/3 of the rpm range as long as the blue temperature sign is on. After the sign is off I consider that manufacturer's intention was to express that full performance can be used.
Approved for me, not more than 1/3 of rpm and 1/3 of gas pedal, just to avoid high torque requests when internal parts are still not warmed.
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But I must say, that from Nordic perspective any discussion of a cold start in UK sounds a bit amusing.  ;D
;D ;D ;D ;D From Italy I must stay quiet.
Approved for me nr°2. The blue light comes off at 44°C. I use to wait some minutes more, oil is slower to  warmup than water, even if it can reach higher temperatures.
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Regarding the oil change, I don't see any reason not to follow the maintenance schedule defined by Honda.
Approved for me nr°3
Ok, an monthly oil change won't damage the engine, but there is no reason to do it with oils following Honda specifications about SAE, API or ACEA.
« Last Edit: March 23, 2023, 10:54:46 AM by jazzaro »

TnTkr

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Re: 2 questions
« Reply #10 on: March 23, 2023, 12:52:17 PM »
Jazz engine doesn't really warm up when idling, at least not in any feasible time. Therefore as soon as the engine has started, it's ready to go. Generally I'd avoid using upper 1/3 of the rpm range as long as the blue temperature sign is on. After the sign is off I consider that manufacturer's intention was to express that full performance can be used.
Approved for me, not more than 1/3 of rpm and 1/3 of gas pedal, just to avoid high torque requests when internal parts are still not warmed.
Actually I ment not more than 2/3 i.e. about 4000 rpm. In my opinion high torque with cold engine is not really an issue, but high speed between two surfaces separated by oil film is more critical.

In fact oil temperature would be more accurate criteria than coolant temperature, but that information is not available in Jazz.
« Last Edit: March 24, 2023, 11:35:22 AM by TnTkr »

embee

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Re: 2 questions
« Reply #11 on: March 23, 2023, 09:42:01 PM »
....But I must say, that from Nordic perspective any discussion of a cold start in UK sounds a bit amusing.  ;D

I know what you mean, having been in the industry doing engine calibrations for potentially arctic markets (Canada etc). We had to guarantee an unassisted start after a 12hr soak at -35C with a 70% battery. It's quite normal for some form of protection or assistance to be used in conditions below this.
What I mean by a cold start doesn't really refer to the ambient temperature as such, it's really meaning starting the engine after it has not been run for a prolonged period, overnight etc. This will be when the calibrations will be for an "ambient" start rather than having any residual warmth in the engine oil and coolant etc.
If the engine has run within the last few hours then things will be different.
Whatever the conditions, fuelling can often be different from the normal during cranking and for a number of seconds or revolutions after the engine sustains running, I always like to give it time for these fuelling strategies to ramp off before driving, but as said earlier this is typically only 20 or 30sec. We used to do plug foul tests which consisted of blipping the throttle repeatedly during this cold afterstart period, that's the way to get plug fouling if it's going to happen, soft carbon and water condensation together will foul plugs.

jazzaro

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Re: 2 questions
« Reply #12 on: March 23, 2023, 10:18:36 PM »

Actually I ment not more than 2/3 i.e. about 4000 rpm. In my opinion high torque with cold engine is not really an issue, but high speed between two surfaces separated by oil film is more critical.
Some user manuals say clearly to not exceed a specific rpm AND gas pressure, they are both important. High torque request means that pistons will be pushed on cylinder walls and since their temperature are not  optimal, also their thermal expansion will be not ok. And cold oil will not ensure full lubrication due to density.
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In fact oil temperature would be more accurate criteria than coolant temperature, but that information is not available in Jazz.
yep. I'm happy for my Suzuki Vstrom, it has a water/oil heat exchanger and this means oil cooled when oil is hot, but also oil warmed when water is warming up faster.

TnTkr

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Re: 2 questions
« Reply #13 on: March 24, 2023, 07:16:23 AM »
When the engine is running below normal operating temperature, it wears more. The colder it is, the more it wears. Therefore it is important to get it warm as soon as possible after cold start (not so much time in sec but number of revolutions), but of course not to cause any damage. Engine warms up when it has to work i.e. there is load. Without load the warming of a modern engine is very slow, which prolongs the time of running cold.

Our older cars warm nicely and windows are sufficiently clear after idling 10-15 minutes in moderate winter temperatures, and reach normal operating temperature (i.e. thermostat opens) in 30 minutes, but not Jazz. Jazz needs really do some work to warm up. Without coolant thermometer is is not possible to know, when the thermostat is opened. I should get a ScanGauge II. Two kilometres uphill would be nice in winter mornings.
« Last Edit: March 24, 2023, 07:29:37 AM by TnTkr »

jazzaro

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Re: 2 questions
« Reply #14 on: March 24, 2023, 08:54:11 AM »
When the engine is running below normal operating temperature, it wears more. The colder it is, the more it wears. Therefore it is important to get it warm as soon as possible after cold start (not so much time in sec but number of revolutions), but of course not to cause any damage. Engine warms up when it has to work i.e. there is load. Without load the warming of a modern engine is very slow, which prolongs the time of running cold.
Approved nr4.
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Our older cars warm nicely and windows are sufficiently clear after idling 10-15 minutes in moderate winter temperatures, and reach normal operating temperature (i.e. thermostat opens) in 30 minutes, but not Jazz. Jazz needs really do some work to warm up. Without coolant thermometer is is not possible to know, when the thermostat is opened. I should get a ScanGauge II. Two kilometres uphill would be nice in winter mornings.
As far I can remember, the thermostat should open about at 75°C, the working temperature is lower than usual. I refer to my Jazz, L13B2 atkinson engine. I will be more precise next time I will connect my  EOBD gauge.

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