Why no iDSi engine for the new Jazz?

[guest164]

Something all us UK Jazz drivers share is the engine type. Whether you are a 1.2 or a 1.4 person you're being pulled along very efficiently by the iDSi engine.

I drive a manual transmission Jazz pretty much every time I get my car serviced (when they don't give me a Mazda 2) and the one thing I can say in my 100 mile roundtrip commute is that I really do love my CVT-7 over the noisy manual car! I like, for instance, 2000rpm 60mph crusing for one! Or around 1000rpm for most of the time driving around the town, without the engine being laboured.

In fact the smart iDSI engine with its clever way of firing the two spark plugs in each cylinder either together or one after the other depending on the engine speed is its strength and a fantasic partner for the CVT-7 transmission.

It's at low and very high revs that this sequential sparking behaviour happens and brings with it some torque. Now in the manual car this gives a little kick as you start to accelerate around the 900 to 1300rpm range which is nice but doesn't last long whereas in the CVT transmission cars, where you can effectively spend lots of time in this region, it makes the car wonderfully drivable and very quiet.

So why have Honda picked VTEC technology over iDSI for the new 2009 Jazz. They are clever people so perhaps I shouldn't worry but I am quite nervous of what to expect from the new VTEC engines. Here's hoping that the new generation 2009 Jazz VTEC CVT-7 cars will be as fantastic as the iDSI engined models were...

Food for fellow Jazzer thinkers out there.

[guest494]

I believe that the new 1.5 i-vtec engine should be as clean as the old 1.4 i-dsi
but a lot more power so the auto versions should be a lot nicer to drive

[guest238]

I think the new 1.3 retains the twin spark plugs per cylinder but a 16-valve dual-stage VTEC cylinder head?

That's the case with the 1.3-litre VTEC petrol engine in the Civic Hybrid?

[culzean]

If the VTEC engine is anything  like the one used in overseas Jazz (Fit) models it does not have twin spark (unlike the 2 valve per cylinder i-DSI, the 4 valves per cylinder on the VTEC do not allow any room for 2 spark plugs, just one central plug per cylinder). This means that the compression ratio will be lower, because the twin spark plugs on the i-DSI allow an unheard of 10.8:1 compression ratio on 95RON petrol, this can only be achieved by shortening the flame path by 'lighting' the fuel/air mixture from both sides

I have read, and can vouch for it from experience on previous VTEC Honda cars that I have had that the i-DSI, although on paper it has less power, it is much more driveable because the torque comes in lower down the rev range.  I have never been in the 'wrong gear' in my 1.4 I-DSI because it is such a forgiving engine, but this 'wrong gear' situation used to happen all the time on the VTEC's and I regularly had to change down and 'give it some revs' (especially on hills with bends in them that didn't allow you to keep up a decent speed).

There is no doubt that the VTEC is a lovely engine for smoothness and out-and-out power, but the i-DSI is much more 'driveable' for everyday use.

[guest809]

Is it me?

I don't recognise this description of the 1.4 I-DSI engine. We love the Jazz for what it is - great sit up and beg driving position, really clever folding rear seats, great build quality (most of the time), excellent residuals etc etc.

But really - a flexible engine? I find my wife's manual 1.4 Jazz is really underpowered and breathless.

Should I have it investigated for a problem or is there a particular way of driving them?

[culzean]

Flexible doesn't mean having loads of power at high revs, it means being able to pull away in second gear on flat ground and being able to change into top gear before 30mph and the engine doesn't jerk and grumble.  The Jazz  has peak torque at around 2700rpm and a pretty good spread from 1500 to 3000rpm, this may not be as low as a diesel, but for its capacity, (remember it is only a 1400cc) the Jazz copes pretty well with everyday commuting demands. It may run out of breath near the redline but most people never go there. Even with a Honda engine you can't have a car with 50mpg+ consumption with the performance a Ferrari.

[guest809]

Culzean

Thanks for your reply and I am sorry now that I used the word "breathless" because that does indeed imply I am expecting high rev performance.

In fact I meant the opposite - i.e. the low down flexibility you describe.

When I drive it I find I have to change down when I want the engine to respond even in quite modest overtaking/hill climbing situations. In fairness I am conscious of two things:

1. I have quite a gentle right foot so perhaps I need to give it a bit more throttle if I am asking it to respond.

2. This is my wife's car and I normally drive a mid-sized diesel saloon - so you would expect more torque to be available at low revs.

My main question remains though. Whilst I am not expecting diesel or large petrol engine performance, is there more I should expect from the Jazz?

What I might try soon is changing the plugs as the car has a full service history but because it has not reached 24K I suspect the original plugs are still in.

[culzean]

If you really are experiencing lack of power (or torque) low down you may want to get the EGR valve checked. If the car is only normally used for short runs the valve can clog up which causes it to stick in the open position.  This valve is designed to divert some of the exhaust gases around into the inlet manifold at higher revs to 'cool' the combustion and lower emissions, but if it stays open when it should be closed it will ruin the performance of the engine at lower revs. There are plenty of posts in this forum about EGR valve problems.

[culzean]

Just another thought,  make sure your wife doesn't use the dreaded 'supermarket' fuel, I find that my jazz feels more lively running on Shell 'V power' or BP 'ultimate' fuel, and OK on 'normal' garage petrols, but supermarket fuels seem to do it no good at all.  This is a purely subjective opinion based on using different fuels in the tank.  The fuel consumption is a bit better using the premium fuels as well, which offsets the higher price.