Author Topic: What MPG are you getting from your Mk1 Honda Jazz ?  (Read 201426 times)

guest7979

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #270 on: December 05, 2018, 09:47:45 PM »
Starting to think i have a problem, struggling to keep it at 41mpg and regulary get 39mpg.
14-20mile round trip daily with some traffic but daul carrige ways mostly.
Would the egr be worth cleaning?
Tyre pressures are good.
Only had the car 3 months and was "recently serviced" before i brought it but have no proof so its on my to do list asap. Might go buy parts tomorrow after work and do it the weekend.

superb

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #271 on: December 07, 2018, 07:28:51 AM »
Mid to high 30's, which I thought was pretty low as my commute is mostly A roads. Checked tyre pressures and they were all around 10-15 psi which probably explains part of the mpg and weird steering feel.

Gave it a major service last weekend (all filters, oil, sparks, brake fluid) and according to the computer I got 46mpg from this tank. 2007 1.4 se with 129k miles.

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #272 on: December 07, 2018, 07:47:30 PM »
Mid to high 30's, which I thought was pretty low as my commute is mostly A roads. Checked tyre pressures and they were all around 10-15 psi which probably explains part of the mpg and weird steering feel.

Gave it a major service last weekend (all filters, oil, sparks, brake fluid) and according to the computer I got 46mpg from this tank. 2007 1.4 se with 129k miles.

How did pressures get that low ? You may well have damaged sidewalls running them at that low pressure as sidewalls can flex way too much.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

guest7979

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #273 on: December 08, 2018, 12:08:08 AM »
Just to keep this updated.
Cleaned my egr valve and pumped my tyres up (mid 20's) and my dash currently reads 51mpg....huge dofferance. It didnt even look that dirty. Seems to pull off smoother aswell which is a welcome bonus

superb

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #274 on: December 10, 2018, 01:19:18 PM »
Mid to high 30's, which I thought was pretty low as my commute is mostly A roads. Checked tyre pressures and they were all around 10-15 psi which probably explains part of the mpg and weird steering feel.

Gave it a major service last weekend (all filters, oil, sparks, brake fluid) and according to the computer I got 46mpg from this tank. 2007 1.4 se with 129k miles.

How did pressures get that low ? You may well have damaged sidewalls running them at that low pressure as sidewalls can flex way too much.

They wouldn't have got damaged at that PSI in a short space of time. The car was sat for almost a year before I bought it.

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #275 on: December 10, 2018, 01:51:29 PM »
Mid to high 30's, which I thought was pretty low as my commute is mostly A roads. Checked tyre pressures and they were all around 10-15 psi which probably explains part of the mpg and weird steering feel.

Gave it a major service last weekend (all filters, oil, sparks, brake fluid) and according to the computer I got 46mpg from this tank. 2007 1.4 se with 129k miles.

How did pressures get that low ? You may well have damaged sidewalls running them at that low pressure as sidewalls can flex way too much.

They wouldn't have got damaged at that PSI in a short space of time. The car was sat for almost a year before I bought it.

If the car hit a pothole with the tyres at that pressure damage is inevitable,  it is surprising how quickly sidewalls can be damaged by heat buildup due to excessive flexing - I guess you have never experience a blowout, well there is always a first time  :o
« Last Edit: December 10, 2018, 04:25:12 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

machedon

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #276 on: December 22, 2018, 09:23:02 AM »
Hi there
My car is doing like 29-31 on dual carriageway and 40-43 on motorway at 70miles constant
Tire pressure is k
Before I Service it it was doing 36 on dual carriageways now it went allot down
I always use shell vpower.
It has only 41000 miles
What can be the problem?
It is a honda jazz 1.4 idsi sport auto
« Last Edit: December 22, 2018, 09:34:48 AM by machedon »

peteo48

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #277 on: December 22, 2018, 11:00:09 AM »
The cold weather can be a massive factor at this time of year. As you can see from my avatar my average is 43.8 on a Mk3 but, over the last 90 miles, the computer is showing 35 which is probably a genuine 32/33.

machedon

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #278 on: December 23, 2018, 09:52:02 AM »
Tks.
So should i relax i think.
Is my first car and i was woried a bit.
I think i am going to try the regular petrol from shell not the vpower.
Do ypu guys think is alright for this car?

Love my Jazz
 8)

MicktheMonster

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #279 on: December 23, 2018, 10:24:08 PM »
Any petrol is fine mate, no need to worry, some do have additives or higher RON rating (measure of the concentration of energy in the fuel) that your car may, or may not, run better on, some cars will show an increase in performance and some won't, it's a bit of trial and error to find one you are happy with, none of them will harm your car.

I generally buy supermarket petrol and have done for decades as it is generally cheaper (and Morrisons is the only full time petrol station in my town), I have never had any issues as a result of using this so I can only assume it is all fine or half the town would have broke down cars.

Kenneve

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #280 on: December 24, 2018, 09:40:53 AM »
I to used to run on Supermarket fuel many years ago, whilst running a Landrover Freelander.
At one point, I reported an engine issue to my dealer and was asked what fuel I was using.
They recommended  I change to one of the well known brands, which i did, it solved the problem and I found I got better MPG, which more than paid the increase in costs. Currently running on BP regular.

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #281 on: December 24, 2018, 10:45:27 AM »
Any petrol is fine mate, no need to worry, some do have additives or higher RON rating (measure of the concentration of energy in the fuel) that your car may, or may not, run better on, some cars will show an increase in performance and some won't, it's a bit of trial and error to find one you are happy with, none of them will harm your car.

I generally buy supermarket petrol and have done for decades as it is generally cheaper (and Morrisons is the only full time petrol station in my town), I have never had any issues as a result of using this so I can only assume it is all fine or half the town would have broke down cars.

Higher octane fuel ( higher research octane number ) actually has less energy than lower octane, it has more additives and less 'fuel' to enable it to be harder to detonate, hence it can stand the heat of higher compression ratio ( feel the end of a bicycle pump when you have inflated a couple of tyres ) without prematurely exploding ( exploding before the spark tells it to ).  It has less total energy than lower octane but because the ignition point can be controlled better the engine can burn it more efficiently.  When the anti-knock sensors on an engine detect the sound and vibration signature of knocking or pinging the ECU retards the point on ignition ( fires the spark later in the piston stroke ) to limit the knocking ( which is actually trying to reverse the piston movement and send it back the way it came up rather than go through TDC and then push it down the way it was going ).  Retarding the ignition point means the engine produces less power.

As the spark ignites fuel and it starts to burn and the flame travels away from plug, the pressure in the chamber increases and with lower octane this can cause remaining mixture to ' pre-ignite' in an uncontrolled way causing knocking, so to stop knocking the spark is ignited later in the stroke by ECU, this drops engine power, with higher octane with less tendency to pre-ignition the spark can be advanced to fire earlier in the stroke, this gives fuel more time to burn properly in a controlled way, extracting more power from the compressed mixture. So even though the anti knock additives in higher octane reduce the energy content of fuel, they allow it to burn and be used more efficiently by the engine, Honda Jazz is around 11:1 compression ratio and although some tricks like spark plug being in the centre of combustion chamber and the actual shape of the chamber being designed to give even combustion there are limits to preventing knocking.  My motorbike with about same CR as Jazz has twin spark plugs ( like the Jazz GD has) to get better controlled of mixture combustion.

Modern ECU will listen to the knock sensor and advance the ignition until it hears knocking and then back it off a little,  with higher octane fuel the ignition will be more advanced before knocking is detected and this means engine can produce more power.  Your are most likely to get knocking at lower revs on a hill when the engine is 'slogging' (so ECU will retard timing just when you need the power more).
« Last Edit: December 24, 2018, 03:35:45 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

peteo48

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #282 on: December 24, 2018, 11:16:35 AM »
Interestingly the Compression Ratio on the Mk3 is 13.5:1 - higher than the MK1 or MK2. I've often wondered if this is a possible reason for using higher octane fuel.

culzean

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #283 on: December 24, 2018, 01:30:48 PM »
Interestingly the Compression Ratio on the Mk3 is 13.5:1 - higher than the MK1 or MK2. I've often wondered if this is a possible reason for using higher octane fuel.

The mk3 is direct injection and the fuel can be injected during the burn and this prevents pre ignition effect, and means the fuel / air mixture can be a bit leaner as well.  The direct injection system was designed to be able to use higher CR and not have knocking because the fuel mist is injected near the spark plug,  IIRC The Mazda sky active DI system has an even higher CR of about 16:1.

The bottom line is that DI do not need higher octane fuel to prevent knocking, which is dealt with by the mechanism of the DI system, the DI injectors work at much higher pressure than normal port injection ( the mk3 has an electric lift pump in the tank and an engine driven fuel pump for the high pressure). DI injectors have the solenoid replaced by a piezoelectric mechanism to work at much higher speed to enable the extremely precise timing of injection.

http://blog.jepistons.com/gdi-gasoline-direct-injection-the-future-of-high-perf-engines

https://www.theengineer.co.uk/issues/24-october-2003/perfect-piezo/
« Last Edit: December 24, 2018, 01:45:07 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

MicktheMonster

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Re: What MPG are you getting from your Mk1 Honda Jazz ?
« Reply #284 on: December 24, 2018, 02:46:40 PM »
Good stuff, I stand enlightened (well... As far as I can understand/follow it anyway).

Thanks.

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