What's in your tank?!

[George Elliott]

Like Peter, I too get more range on a tank with the good quality fuel.(approx +20%)
The engine sounds much nicer under load between 3000 & 5000rpm.
Last check I did on a 220mile round trip incl heavy traffic (Dublin) and motorway driving, was 27.6mpg - I cannot believe how economical my car is.
Interesting info Rick
George

944t
964

 

[eastendr]

ORIGINAL: sawood12

Good stuff Rick, that does clear up alot of loose ends in my mind. However you say that knock protection does not run in closed loop,, then what controls timing advance? If the ECU doesn't advance timing upto the knock threshold, say under WOT, then what does it use to determine how much advance to use and when? Surely it can't be via engine vacuum like my old MK3 Escort?

The timing comes from a static map in the DME chip. This is programmed in a table of RPM /airflow and is mapped for the engine / fuel.

The advance will only be as great as that programmed in the map. Higher octane allows faster burning so more ignition advance. If the fuel is lower quality than is mapped for, the engine knock is picked up by the knock sensor which will then retard the ignition by maximum 6 degrees until the knock stops.

 

[Diver944]

So I was always wrong in thinking 'the car will advance as much as possible until it detectes knock'

Can a layman therefore say 'the car will start off at the optimum pre-programmed advance, and will retard as soon as it detects knock'?

That makes more sense

 

[eastendr]

That about sums it up.

More modern ECU's can incorporate a learning or adaptive strategy whereby the ECU 'learns' an adaptive map on top of the preset values, using knock sensors for ignition and lambda probes for fuel trim values. Typically draining or disconnecting the battery will lose these values and allows reset back to base settings, the car will then re-learn the trim values over time as it is driven.

 

[Hilux]

Simply using higher occtane fuel (99 instead of 95) will not release more power unless the timing and fuelling map are optimized for the additional octane.

Well done Rick, hit, nail and head come to mind.

Lots of myths out there []

I`ll bet the standard mapping (not seen it) on a turbo will probably be fairly unrefined for that reason and therefore larger parameters allowed hence the negation of better power and economy that `could` be achieved with a remap. Basically in standard form it will (should) accept all fuels with marginal differences in output or put another way, with no particular advantage.

 

[John Sims]

ORIGINAL: Hilux

......I`ll bet the standard mapping (not seen it) on a turbo will probably be fairly unrefined for that reason and therefore larger parameters allowed hence the negation of better power and economy that `could` be achieved with a remap. Basically in standard form it will (should) accept all fuels with marginal differences in output or put another way, with no particular advantage.

That would account for why, years ago, one of the favoured ways of getting more omph out of a Turbo was to have it "Wayned". ie Have a bespoke map written by Wayne Schofield.

 

[Hilux]

Yup, on a 3D map you can identify peaks and troughs at all load and rev configurations so can trully map for optimum performance. Trouble is that using inferior or `different` fuel thereafter creates a marked and very noticeable difference in performance

 

[appletonn]

Ok, now I understand - thanks Rick and everyone else!

One last question (for today!), are any Turbo owners running anything other than the standard induction setup and would a K&N etc panel filter make a scrap of difference (despite the makers' claims) or is it just kiddology?

I don't really want to remove the airbox and put a cone type filter directly onto the throttle body as it would lose out on the cold airflow (or so it would appear?!), but are there any alternatives out there?

In 9 days time (and counting [8|]) I will finally get my hands on the car & then the questions will stop (for a while) and the driving will begin...!

Thanks again

 

[George Elliott]

Nick
a K&N is the very top of a long slippery slope.......good luck on the way down, it can last years........and £ears and ££ars an£££[8|]

I put one on my car and would say its a good filter, but theres a lot more difference in performance if the ambient temp changes 10 degrees than there is between a std paper or a K&N filter.

I have no regrets about fitting mine.

Nice looking car
George
944t

 

[sawood12]

ORIGINAL: Hilux

Simply using higher occtane fuel (99 instead of 95) will not release more power unless the timing and fuelling map are optimized for the additional octane.

Well done Rick, hit, nail and head come to mind.

Lots of myths out there []

I`ll bet the standard mapping (not seen it) on a turbo will probably be fairly unrefined for that reason and therefore larger parameters allowed hence the negation of better power and economy that `could` be achieved with a remap. Basically in standard form it will (should) accept all fuels with marginal differences in output or put another way, with no particular advantage.

OK if this is the case then why can't you map your car for higher octain fuel, say 99 RON, and if you fill it up with 95 rely on the knock system to retard the timing to suit the lower octain? Does that require more than 6 degs of ignition retardation?