Mk2 or Mk3??

[robark]

I have been giving it a drive around this morning and the roughness is most noticeable at about 1500rpm in 1st gear
If you are stuck in traffic doing 8 -10 mph then its not pleasant to drive.
Also when you are changing up then the revs drop to the rough area again so I'm having to keep the revs up more.
I must also add that's its a secondhand Mk3 with 4000 miles on the clock

I also have a mark 3 manual with the 1.3 engine. It exhibits the same rough behaviour you describe at low revs, in fact it sounds almost like a diesel with increased noise accompanying the roughness until the revs build up.
I attribute this characteristic to the fact that at low revs the engine is working in the "Atkinson" mode which is characterised by a higher efficiency caused by an increased increased compression ratio (which is in turn caused by a modification in the valve timing at low revs).
I agree with John Ratsey when he makes the point that the higher revs that the cvt versions exhibit on pull away is to overcome the weak engine porformance at low revs. It appears to me that the cvt version of the mark 3 is the better option to buy, if you want decent acceleration from standstill, unless you are prepared to make more than average use of the accelerator pedal with the manual version.

[culzean]

I attribute this characteristic to the fact that at low revs the engine is working in the "Atkinson" mode which is characterised by a higher efficiency caused by an increased increased compression ratio (which is in turn caused by a modification in the valve timing at low revs).

I think Atkinson cycle (the Honda i-VTEC version) leaves the inlet valves open as the piston is going up, this forces some of the cylinder petrol / air mixture back into inlet manifold,  while this is happening the throttle is actually open more than it should be for the revs (a bit magical) this reduces 'pumping losses' that happen when engine is sucking against a closed / partially closed inlet manifold.  Allowing some of the mixture to escape actually reduces compression ratio at low throttle openings,  which is 'Atkinson cycle' ala Honda. 

http://asia.vtec.net/Engines/RiVTEC/

Apparently Honda have in the pipeline a direct injection Atkinson cycle engine ?? but direct injection engines, whether diesel or petrol suffer from high Nox emissions - but maybe Honda have a trick,  direct injection engines allow a higher compression ratio (up to over 16:1) because fuel is not compressed with the air in the cylinder,  but is injected when compression stroke is nearly finished, this prevents engine knocking (pre-ignition).

[edam]

So basically I have not just changed from a type of gearbox but also I have changed from a type of engine  as well.
Too many steps perhaps .

[robark]

I attribute this characteristic to the fact that at low revs the engine is working in the "Atkinson" mode which is characterised by a higher efficiency caused by an increased increased compression ratio (which is in turn caused by a modification in the valve timing at low revs).

I think Atkinson cycle (the Honda i-VTEC version) leaves the inlet valves open as the piston is going up, this forces some of the cylinder petrol / air mixture back into inlet manifold,  while this is happening the throttle is actually open more than it should be for the revs (a bit magical) this reduces 'pumping losses' that happen when engine is sucking against a closed / partially closed inlet manifold.  Allowing some of the mixture to escape actually reduces compression ratio at low throttle openings,  which is 'Atkinson cycle' ala Honda. 

You are correct and I was wrong, the compression ratio is reduced during the Atkinson mode of operation. The 13.5 compression ratio seems to quite high for a petrol power plant. Maybe a higher octane fuel may help prevent the roughness that I and others have experienced with this engine at low revs. I will try some Shell Nitro Plus and see if that has any affect.

http://asia.vtec.net/Engines/RiVTEC/

Apparently Honda have in the pipeline a direct injection Atkinson cycle engine ?? but direct injection engines, whether diesel or petrol suffer from high Nox emissions - but maybe Honda have a trick,  direct injection engines allow a higher compression ratio (up to over 16:1) because fuel is not compressed with the air in the cylinder,  but is injected when compression stroke is nearly finished, this prevents engine knocking (pre-ignition).

[John Ratsey]

I'm not 100% convinced that the rough engine problem is normal. At the end of August before I confirmed my order for the Mk 3 my dealer took me for a spin in his newly-received Mk 3 manual (hence I got him to drive - I didn't want to trash the gearbox!) but everything seemed to run very smoothly but perhaps we didn't do much crawling along at the problem rev range.

Go up a long reasonable steep hill where you can give the engine a good workout. That might blow out a few cobwebs and get it running like new.

[ColinS]

As I said before, mine is absolutely fine so it cannot possibly be a generic problem or they would all be like it.

[Madelvic]

Pros and cons

Mk 3

More economical
Better spec by a long way
Better ride

Mk 2

Less evidence of cost saving
More storage space
Better trimmed (it's an insult to carpets to call the floor lining in the Mk3 a carpet)
Better looking (in my opinion)

Sadly I think both are way off the mark in terms of state of the art engines.  Daughter has a 1.0 triple VW Polo and it is a sewing machine in comparison  to the Jazz engines.  Quiet, rev, economical. Ford get a great write up too for their 1.0 engines

As long as they've had the recall work done, I guess.  Plenty have went pop due to coolant loss.

http://www.honestjohn.co.uk/user-article/111213/ford-focus-1-0

As for the GK Jazz, I think it's very poor VFM and with very few options, (only one engine and three trim levels to choose from), it's hard to get excited about it.

Interesting perspective Chris.  I didn't know about the Ford issue and I've yet to drive one.

As for vfm I think the Jazz stacks up pretty well.  We had a look at a lot of competitor vehicles and a pro for me was all the options are included in the price which reflects in the residuals.  I've just sold an old Audi, that new had more than the cost of a new Jazz in extras, for heavens sake.   I was fortunate in being able to find a private buyer who valued the extras, but in recent conversations with dealers they gave no allowance for all the extras on my Audi

A choice of engines would be good.  Ours is noticeably loosening up with 1500 miles so I may have been a bit too harsh in my comments

[ColinS]

A choice of engines would be good.  Ours is noticeably loosening up with 1500 miles so I may have been a bit too harsh in my comments

I agree.  I was most disappointed when I first drove mine but the salesman assured me that it would improve with miles.  Indeed, I now have just over 2000 miles on the clock and it has much better performance.

[edam]

I think my problem with stuttering at low revs is worse when the air con is on. Despite another visit to a service dept. no fault has been found.
I think this will have to wait until I can compare it to a loan car when the service is due.

Also I'm surprised how low geared it is.
When I'm driving in 6th I still feel that I should change up to another gear. I can overtake on a motorway without having to change down to 5th and that was when I was going uphill!!!
Something else to check on a loan car

[ColinS]

Also I'm surprised how low geared it is.
When I'm driving in 6th I still feel that I should change up to another gear. I can overtake on a motorway without having to change down to 5th and that was when I was going uphill!!!

I am now getting quite intrigued.  How many revs are you showing at say 60mph in sixth grear?

[VicW]

The GE manual 1.4 that I had was very low geared at about 21mph/1000rpm.
My current GE facelift CVT is very highly geared at about 30mph/1000rpm but the CVT is very responsive changing down when a bit of boot is applied.

Vic.

[robark]

According to the info given at www.automobile-catalog.com , the gearing for the latest Manual version of the Jazz is, 22.2 mph/1000 rpm in 6th gear

[edam]

According to the info given at www.automobile-catalog.com , the gearing for the latest Manual version of the Jazz is, 22.2 mph/1000 rpm in 6th gear

That seems about right as I was doing 70mph in 6th gear at 3000rpm.

I was expecting 6th to be more of a overdrive, from reading other comments on the forum, but that is not the case.

Also its worth noting that my Jazz has 4000 miles on the clock

[John Ratsey]

I would have also expected Honda to have provided higher gearing on the 6th gear. We know from the CVT version that the engine has the power at around 2200 rpm to move the car at 70mph. I now appreciate why I couldn't understand the reviewers who complained about engine noise on the motorway - they were obviously driving a manual Jazz.

Running the aircon inherently puts more load on the engine. It's possible that the CVT version increases the revs a bit to compensate.

[edam]

The low gearing on the manual explains why the CVT is more economical.

Also I feel that rather than adding another gear to the Mk2 5 speed they have put another gear between 4 and 5 on the old box.
So you are driving 1, 2, 3, 4, 4.5 ,5 if that makes sense