Recent Posts
91
Honda Jazz Mk3 2015 - 2020 / Re: 2 questions
« Last post by embee on March 24, 2023, 10:39:59 AM »The Jazz uses a thermostat on inlet (into engine), "traditional" engines typically used a themostat on outlet (from engine).
A 'stat on inlet will typically operate at around 10degC lower than a 'stat on outlet type, essentially it works at desired radiator outlet temp (cooled) rather than radiator inlet temp (hot). Temp rise across an engine will typically be around 10degC at moderate/high load.
The advantages of a 'stat on inlet are that it minimises the temperature cycling within the engine.
When an outlet type begins to open it requires coolant to pass through the radiator, back to the pump, and through the engine again before it reaches the stat again, and it is inevitably cold to begin with (near ambient). The cold coolant then causes the stat to close down while the engine heats up again, and thus the hot/cold cycle gets repeated. The greater the volume of the cold circuit the worse the cycling tends to be (e.g. rear engines and front radiators, MGF and Lotus Elise were classic examples causing head gasket failures due to the temp cycling).
With a stat on inlet (to the pump) it senses the temp in the bypass circuit (engine out directly back to pump inlet) and when warm enough it begins to open to allow cold coolant in from the radiator. This mix of cold/hot coolant goes directly over the stat and so it reacts immediately and closes down a bit, preventing the system being filled with cold.
A 75C inlet stat will mean the engine runs typically around 85C outlet, which is more or less "normal" (often 88C stat on outlet). My Yaris has an 80C inlet stat.
A 'stat on inlet will typically operate at around 10degC lower than a 'stat on outlet type, essentially it works at desired radiator outlet temp (cooled) rather than radiator inlet temp (hot). Temp rise across an engine will typically be around 10degC at moderate/high load.
The advantages of a 'stat on inlet are that it minimises the temperature cycling within the engine.
When an outlet type begins to open it requires coolant to pass through the radiator, back to the pump, and through the engine again before it reaches the stat again, and it is inevitably cold to begin with (near ambient). The cold coolant then causes the stat to close down while the engine heats up again, and thus the hot/cold cycle gets repeated. The greater the volume of the cold circuit the worse the cycling tends to be (e.g. rear engines and front radiators, MGF and Lotus Elise were classic examples causing head gasket failures due to the temp cycling).
With a stat on inlet (to the pump) it senses the temp in the bypass circuit (engine out directly back to pump inlet) and when warm enough it begins to open to allow cold coolant in from the radiator. This mix of cold/hot coolant goes directly over the stat and so it reacts immediately and closes down a bit, preventing the system being filled with cold.
A 75C inlet stat will mean the engine runs typically around 85C outlet, which is more or less "normal" (often 88C stat on outlet). My Yaris has an 80C inlet stat.
92
Honda Jazz Mk4 2020 - / Re: Engine noise
« Last post by embee on March 24, 2023, 10:20:34 AM »A friend has recently got a mk4, going from a Peugeot diesel. He has noted (complained?) about the engine noise when accelerating hard.
I explained that it's because when you demand max power the technology is there to provide it .... straight away. He is used to the engine speed and noise building up as the car accelerates. The hybrid Jazz engine will go directly to max power output and stay there while the demand persists.
In my years in engine development it never ceased to amaze me just how noisy engines are at max power. When you hear and see one on a test bed you wonder why anyone happily sits a couple of feet behind one in a car without thinking it's about to blow up. A 500+bhp twin turbo V8 at full chat is quite a fearsome thing when you can see and hear it. On a motorbike you have the engine between your legs!
Try red-lining a "normal" car through the gears and see what it sounds like, that's what the mk.4 Jazz does in effect.
Obviously to some this will be intrusive and/or offensive, and it may or may not be deemed "acceptable". I know manufacturers go to considerable lengths to mitigate the noise in the cabin but inevitably noise suppression is a compromise of what is achievable with cost and weight taken into account. I suppose the full answer is pure EV with no engine.
Does anyone notice electrical system whine? You can get various sorts of whining type noises from control systems/inverters/motors etc.
I explained that it's because when you demand max power the technology is there to provide it .... straight away. He is used to the engine speed and noise building up as the car accelerates. The hybrid Jazz engine will go directly to max power output and stay there while the demand persists.
In my years in engine development it never ceased to amaze me just how noisy engines are at max power. When you hear and see one on a test bed you wonder why anyone happily sits a couple of feet behind one in a car without thinking it's about to blow up. A 500+bhp twin turbo V8 at full chat is quite a fearsome thing when you can see and hear it. On a motorbike you have the engine between your legs!
Try red-lining a "normal" car through the gears and see what it sounds like, that's what the mk.4 Jazz does in effect.
Obviously to some this will be intrusive and/or offensive, and it may or may not be deemed "acceptable". I know manufacturers go to considerable lengths to mitigate the noise in the cabin but inevitably noise suppression is a compromise of what is achievable with cost and weight taken into account. I suppose the full answer is pure EV with no engine.
Does anyone notice electrical system whine? You can get various sorts of whining type noises from control systems/inverters/motors etc.
93
Honda Jazz Mk4 2020 - / Re: Engine noise
« Last post by Lord Voltermore on March 24, 2023, 09:58:52 AM »Like the others I find if you floor it the engine can be louder for a short time, and occasionally does it without driver input, for no obvious reason. Also if you have heating or aircon operating you can sometimes hear the fans etc running. Could that be the constant whistle referred to? Conventional cars also make this fan noise except its normally unnoticed among general engine noise. .
Anyone thinking of buying a mk 4 should not be concerned that its going to be noisy. Any extra engine noise is usually no worse than a normal car would always be making in similar circumstances .You might notice it more because the mk4 car is usually so quiet. Sometimes almost eerily quiet.
As others have said sometimes ,if the car is having to work hard , on a long steep hill for instance, the engine may start itself and run faster and more noisily than you might expect or would normally drive a car. . But its not that often and might even startle you the first time it happens to you. There is nothing wrong , it rarely lasts long and the car will reduce the revs as soon as it can. Sometimes you can get it to quieten down immediately with no noticeable loss in progress by coming off the throttle slightly. Possibly also by switching off heating/aircon.
For me this occasional engine racing its a small price to pay to have a car thats so economical on fuel and so quiet and refined the vast majority of the time.
Anyone thinking of buying a mk 4 should not be concerned that its going to be noisy. Any extra engine noise is usually no worse than a normal car would always be making in similar circumstances .You might notice it more because the mk4 car is usually so quiet. Sometimes almost eerily quiet.
As others have said sometimes ,if the car is having to work hard , on a long steep hill for instance, the engine may start itself and run faster and more noisily than you might expect or would normally drive a car. . But its not that often and might even startle you the first time it happens to you. There is nothing wrong , it rarely lasts long and the car will reduce the revs as soon as it can. Sometimes you can get it to quieten down immediately with no noticeable loss in progress by coming off the throttle slightly. Possibly also by switching off heating/aircon.
For me this occasional engine racing its a small price to pay to have a car thats so economical on fuel and so quiet and refined the vast majority of the time.
94
Honda Jazz Mk4 2020 - / Re: Engine noise
« Last post by Bristol_Crosstar on March 24, 2023, 09:38:21 AM »I find the revs are greatest after approaching a steep uphill section with the battery at 20 or 30%, then the engine has to supply all the electrical energy for climbing the hill, it's worst if travelling at higher speeds (eg motorways).
Generally it can be avoided just by being gentle on the accelerator, not really an issue overall.
Generally it can be avoided just by being gentle on the accelerator, not really an issue overall.
95
Honda Jazz Mk3 2015 - 2020 / Re: 2 questions
« Last post by jazzaro 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.
96
Honda Jazz Mk4 2020 - / Re: Engine noise
« Last post by Nicksey on March 24, 2023, 07:48:55 AM »As this is my first hybrid AND auto gearbox, it has taken me 7k to get used to a different way of driving. The engine does respond in a different way, and sometimes sounds like its high revving... almost like you're clutch slipping. A couple of times I have put my foot down too heavily and the revs increase dramatically before catching up with itself. I have also now experienced that algorithm with the revs that Honda built in to make it sound like the gears are changing (pointless).
I think what Travis means though, is that sudden engine noise that kicks in for no reason that the driver has intended. Again, like the others have mentioned.. I now accept the engine configuration is doing what it needs to to to optimise performance and efficiency. I only really notice it at slow speeds, when I am using things that drain the battery quickly too often.
I think what Travis means though, is that sudden engine noise that kicks in for no reason that the driver has intended. Again, like the others have mentioned.. I now accept the engine configuration is doing what it needs to to to optimise performance and efficiency. I only really notice it at slow speeds, when I am using things that drain the battery quickly too often.
97
Honda Jazz Mk3 2015 - 2020 / Re: 2 questions
« Last post by TnTkr 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.
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.
98
New Members / Re: New Member
« Last post by aphybrid on March 24, 2023, 06:42:39 AM »Welcome, enjoy.
99
Honda Jazz Mk4 2020 - / Re: Engine noise
« Last post by Kremmen on March 24, 2023, 05:22:56 AM »I've never experienced any unexpected engine noise.
There have been a couple of occasions I've floored it from a standing start and the noise, has been what I would expect from any engine.
In the main though I drive sedately and the only time I hear the engine is in my driveway. Once I'm on the move I rarely notice it.
There have been a couple of occasions I've floored it from a standing start and the noise, has been what I would expect from any engine.
In the main though I drive sedately and the only time I hear the engine is in my driveway. Once I'm on the move I rarely notice it.
100
Honda Jazz Mk3 2015 - 2020 / Re: 2 questions
« Last post by jazzaro on March 23, 2023, 10:18:36 PM »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.
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.
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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.
