The JTS 2.2 and fuel

[SeleMatt]

After owning a Brera with this motor and running it on Shell V Power 98 almost exclusively in that time for around 18 months, the car never once started first stab of the button. I mentioned this to Mick at Monza Motors a few months ago and he suggested trying 95ron fuel. So I did this and the car has started first stab of the button every time. I should point out that the book recommends a minimum of 95 but I've owned other cars that don't recommend 98 and they've all started first kick. Amazing the difference that 3ron can make to this engine.

[Ascari32]

Can he, or anyone provide an explanation as to why?

I run my 3.2 JTS on 97,98 and frequently 99 and recently because I pulled into a garage which only had RON 95. However, I can't say I have noticed a difference - although, I do recall now with the 95 it started - on the button, firing instantaneously. However, until the next fill, I was constantly listening for "Pinging", but never detected any.

Aware of this now - thanks - I will make a mental note to check ease of start - up from now on.

[bazzbazz]

If memory serves me correct 95 Octane has a slightly lower Auto-ignition Temperature, which may well help starting.

[Ascari32]

Doh! Of course it has, that's why additives additives are there to inhibit pre-ignition. Thanks! That was washed to the back of my memory until you jogged it. 

[kaleuclint]

I received similar professional advice for the TBi engine and its propensity for the rearmost oxygen sensor to trigger a fault code.  Though I can't say switching to 95RON fixed it.  To be fair I might not use the car enough for this to take effect.

[Ascari32]

Copied from a post I created a few hours ago - just realised it probably ought to have been here in any case, bearing in mind the association between the two.

Hi,

I was looking for the post of a few days ago when I commented my Q4 started on the button after I filled with RON 95. The response to that was 95 has a lower self ignite level - made sense and it jogged my memory about the issue.

Found it! Quote BazzBazz "If memory serves me correct 95 Octane has a slightly lower Auto-ignition Temperature, which may well help starting."


However, again I filled up with 95, simply because it was the max grade at a garage I have never used before. No issues before given I am doing a fair number of urban/low speed driving, so I didn't foresee any problems.

However, what was totally unexpected was:-

I had a standing post - cat lambda alarm for weeks which I was going to investigate once my new cat arrived, so it was ignored. Also, I too have sooty tail pipes - they didn't take long to foul given these are my new "Noisy" boxes. This too I expected to have sorted when the exhaust system is competed and I have the AFR checked - I think she is running rich.

The drive home from filling up with 95 was quite short and everything seemed to be OK, albeit with the above conditions prevailing.

Today however, we went for a little jaunt to a local Marina, some 25 miles away. Soon after leaving home and before the car really had much chance to fully warm up, the dash alarms cleared. "Get Engine Checked" cleared and I now no longer have any engine management alarms - after weeks and weeks of them being continuously displayed.

I have not reset the Average consumption trip for about 600 miles~ so that any improvement in economy causes a very slow improvement in the dash figure.

The roads to the Marina are small, through villages, twisty and undulating. Average consumption moves from 25.4 to 25.7 mpg. Not much amiss there I say to myself. However, on parking up at the Marina, on checking the tail pipes, they are devoid of soot. Starting to get a "Brownish" tinge to the deposits.

Now I remember some time ago watching a YouTube video about using high grade fuel - the drift of it being it is a waste and does not benefit either the engine or economy. The chap was not saying use low grade stuff, just the appropriate grade for the engine.

So, have my sooty exhausts be a consequence of incomplete burn due to additive in the 98/99 ron I hitherto have been using? I believe Alfa state a minimum of 97 for the 3.2 JTS. But that is probably appropriate for high speed motorway use and long journeys. 95 seems to suit my engine, despite the heads being skimmed, The block too being skimmed/dressed and therefore the compression ratio a little higher than spec!

Can anyone throw further light on this phenomenon?