hi, all. mine's a 2016 1.8 TSI Superb calling for RON 95 . i use 98 all the time. will it be of any power/economy benefit to get my engine tuned to run at a higher compression ratio ? i don't suppose the ECU can bump up compression ratios when higher octanes are used ? thanks, from New Zealand

Is 95 ron not the minimum octane fuel for your car as shown on the Filler Flap?

Easy enough to use tanks of 95 ron unleaded and then 98 ron and know yourself if you feel a smoother more efficient engine or any performance benefit or even better economy.

 

http://volkswagen.co.uk/need-help/owners/Fuel

 

Your 1.8TSI should love that higher octane fuel.

In the UK Super Unleaded from filling station comes in 97 ron minimum or 99 ron minimum.

Edited 18 July, 20187 yr by Offski

10 hours ago, Offski said:

Is 95 ron not the minimum octane fuel for your car as shown on the Filler Flap?

Easy enough to use tanks of 95 ron unleaded and then 98 ron and know yourself if you feel a smoother more efficient engine or any performance benefit or even better economy.

 

http://volkswagen.co.uk/need-help/owners/Fuel

 

Your 1.8TSI should love that higher octane fuel.

In the UK Super Unleaded from filling station comes in 97 ron minimum or 99 ron minimum.

 

I use only 98 and my car acts much better than using 95. There is also slight improvement in fuel consumption but I doubt if there is any finantial gain as 98 is bit more expencive. 

 

Your Superb's filler flap should actually say that 95 is minimum octane that could be used in your car. 

There are world regions where there are Skoda / VW Models that do show lower than 95 Octane as 'Minimum Octane' that can be used, New Zealand is not one of those though.

Edited 19 July, 20187 yr by Offski

On 18/07/2018 at 20:07, chrisluciofg said:

hi, all. mine's a 2016 1.8 TSI Superb calling for RON 95 . i use 98 all the time. will it be of any power/economy benefit to get my engine tuned to run at a higher compression ratio ? i don't suppose the ECU can bump up compression ratios when higher octanes are used ? thanks, from New Zealand

 

Hi,

 

I think you're trying to solve a problem you've not got (or create a problem for yourself)

 

A petrol engine will (or at least can) develop more power with higher compression. A consequence of higher compression is that higher octane fuels are required. For a given level of compression, the higher octane fuel will burn more slowly and in a more controlled way. Higher octane fuels do not have greater energy density, but higher compression engines are better at extracting power from those fuels more effectively.

 

Because the pressure in the cylinder builds as the flame front from the explosion spreads across the cylinder, the ignition timing is such that the spark occurs slightly before the piston reaches the top of the compression stroke. The idea being that maximum downwards pressure on the piston crown is achieved just after the top of the stroke so there's maximum force pushing the piston down and in turn turning the crank. If you put higher octane fuel in without increasing the compression ratio or changing the ignition timing, the burn is slower so the force on the piston occurs further after the top of the stroke; in effect the explosion and it's force is chasing the piston down the cylinder.

 

To "tune" an engine to run a higher compression ratio, requires one or more of

- higher compression/domed pistons

- longer throw crankshaft with appropriately matched head

- bigger turbo/supercharger (or a more aggressive use of variable vane turbo output and maximum pressure)

- different camshafts with less overlap

 

None of which are straightforward jobs

 

Engines these days tend to have "knock sensors" to allow them to cope with you putting in fuel that's too low an octane (if the fuel burns too quickly that point of maximum thrust occurs at or before the top of the stroke causing the engine to "knock"; the ECU will delay the spark such that the thrust from the faster burn comes later), but they don't tend to advance the ignition to respond to higher octane fuels.

 

(with made up figures) if an engine with 10:1 ratio runs fine on 95 RON, that car may require 98 RON and a change to the ignition timing to run as well (and with a little more power) if the ratio is increased to 12:1.

 

If however you put 98 RON in a car that is designed/tuned to run on 95 RON, it won't do any damage, it may seem slightly smoother (as the burn will be slightly slower/more controlled) but you're unlikely to be gaining anything in real terms.

 

https://en.wikipedia.org/wiki/Octane_rating is worth a read.

 

Hope that made sense

 

 

Speaking from actual experience with a VAG 1.8T engine running on 99 OCTANE Shell V Power unleaded this what I found as standard and after stage 1 re-map.

Stock engine should produce 177bhp and 173lb/ft ON REGULAR UNLEADED.

Actual rolling road results as stock but run on 99 OCTANE SUPER UNLEADED was 190bhp and 190lb/ft.

Actual rolling road on 99 OCTANE SUPER UNLEADED with STAGE 1 RE-MAP was 230bhp and 230lb/ft.

This work was carried out by AmD in Essex, England.

Top speed increased from 142mph to 148mph on my 2003 SEAT LEON CUPRA. Work was done in 2004, and I owned the car from new.

ONLY FACTS NO BULL!

Removed my like on above post when I noticed the should word 

 

"Stock engine should produce 177bhp and 173lb/ft ON REGULAR UNLEADED"

 

I think it's fairly accepted that most VAG engines produce higher power/torque than rated spec especially when new, i.e. it's a minimum to expect.

 

Were the top speeds stock unleaded/remapped actually measured with calibrated equipment?

 

So the facts are in fact not facts.

Edited 25 August, 20187 yr by xman

i wonder why VAG under-state their performance figures , but over-state that of fuel economy 

Published performance should be a minimum (when new).

 

Economy results are government mandated tests and there is always a disclaimer nowadays.

37 minutes ago, xman said:

Removed my like on above post when I noticed the should word 

 

"Stock engine should produce 177bhp and 173lb/ft ON REGULAR UNLEADED"

 

I think it's fairly accepted that most VAG engines produce higher power/torque than rated spec especially when new, i.e. it's a minimum to expect.

 

Were the top speeds stock unleaded/remapped actually measured with calibrated equipment?

 

So the facts are in fact not facts.

Based upon revs in 6th gear always used Shell V Power absolutely no point running a performance car and putting inferior fuel (bit like using the cheapest oil available). For example standard engine (190bhp on 99 octane) produced maximum power at 5,500 revs and after re-map (230bhp) maximum power developed at 6,000 revs from rolling road data which equated to the extra 6mph. Autocar road test quoted top speed at 142mph for the car they tested and we can assume that an extra 40bhp should easily raise the top speed by a paltry 6mph!

43 minutes ago, chrisluciofg said:

i wonder why VAG under-state their performance figures , but over-state that of fuel economy 

Can't remember what the official combined figure for the Cupra was but as I was 15 years younger I drove for SMILES NOT MILES (to quote NOAIM). But the 55 litre tank would normally give me around 360 mile range (12.1 gallons or rough 30MPG). Technology has improved so much in this time that my current car pushing out 302bhp now averages 40.96mpg.

2 hours ago, chrisluciofg said:

i wonder why VAG under-state their performance figures , but over-state that of fuel economy 

Is it not to cover their backsides as people will run these cars in all sorts of climates and altitudes? Therefore you could have differing results somewhere hot and wet compared to somewhere cooler and drier or at sea level and a few thousand feet up. 

 

Fuel economy...new legislation is mandated from 1st of September I believe which will show actual CO2 and more realistic mpg / km/l. Every manufacturer's current figures are always over stated as they were carried out in non realistic and non obtainable conditions. So it's definitely not just VAG group!

^^^ They were carried out in a temperature controlled building and if you drive to work in a temperature controlled building, weigh very little, have no optional extras 

and over inflate the tyres and put diesel in the engine oil then submit your test results they are totally achievable.

http://skoda.co.uk/pages/fuel-consumption-statement.aspx 

 

With the WLTP / RDE they will not be filling the available seat or the luggage compartment or the fuel tank to the brim either, 

or turning on the lights, heated rear screen, mirrors, radio and switching off stop / start.

You only have to read threads on any motor forum to see that widely differing m.p.g. results are achieved with same model of car. So, why is it so difficult to accept that the claimed consumption figures are merely for comparative measures? If you take them and factor in the man in the street real life figures (% of claimed) then you can, if you feel the need, check out comparative results. Never was supposed to be anything different until, I guess, the marketing people got hold of it.

 

The new WLTP controls simply claim to give a more realistic comparison to real life. At the moment this stuff has to be done in controlled laboratory conditions in order to give a standardised result. There are too many variables (see Offski's examples above)  in real life for the results ever to be more than indicative and the tech to carry out on-road testing doesn't yet have the repeatability/accuracy required for standardised testing.

 

So we are not getting Real Driving Emissions (RDE) testing until September 2019. Those will be on-road conditions and a much longer test. Again their purpose is really to monitor progress towards environmental targets rather than provide consumer data.  Of course the marketing people will want to use that data for the consumer and I guess the consumer will want to know the results. But those who expect 100% accuracy and repeatability will I fear be disappointed.

Despite WLTP and even RDE, it seems thatVW will still be sticking to old NEDC figures until 2021 in line with "government guidelines”

 

https://www.volkswagen.co.uk/owners/wltp

 

We currently anticipate that taxation, registration and fleet emission targets may continue to based on NEDC values until 2020/2021. Until that changes, and as there will be a mix of NEDC type approved and WLTP type approved vehicles in the market, consumers need a method facilitating direct comparison between different models and different manufacturers. In line with Government guidance, NEDC figures will therefore continue to be stated, even for WLTP typeapproved vehicles and, where necessary, these figures will be derived from the WLTP data using an industry standard conversion procedure developed by the European Union, CO2MPAS. These derived values are known by various terms: "NEDC derived", "NEDC equivalent" or "NEDC correlated".

 

In the case of the 2019 Passat estate 2.0tdi they are still quoting the old NEDC figures despite claiming WLTP compliance, and not CO2MPAS converted NEDC derived. Maybe they think "where necessary" doesn't apply to current models.

 

Fuel consumption and CO2 emissions figures are obtained under standardised EU test conditions (or, in cases of vehicles with WLTP type approval, are the NEDC figures provided pursuant to Government 
guidance until further notice). These figures facilitate direct comparison between different models from different manufacturers, but may not represent the actual fuel consumption achieved in ‘real world’ 
driving conditions. More information is available at www.volkswagen.co.uk/owners/wltp

Edited 25 August, 20187 yr by xman