GOLFMK7
GOLFMK6
GOLFMKV
FORUM OPTIONS
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Go Back   GOLFMK7 - VW GTI MKVII Forum / VW Golf R Forum / VW Golf MKVII Forum > Regional Forums > CANADA


Reply
 
Thread Tools Display Modes
Old 11-08-2017, 11:28 AM   #35
amiriten
Junior Member
 

Join Date: Sep 2017
Posts: 1
2017 5dr golf trendline automatic since 01/09/2017 and already at 23k. I have only fed it 87 octane with 85/15 city/hghw and average speeds of 120 on highway.
I get 6.5 and I do have a heavy foot in the city. My best stat was after my first oil change at 15k about 2 weeks ago when I achieved 860 km on a full tank of 52 liters.

Sent from my VS995 using Tapatalk
amiriten is offline   Reply With Quote
Old 11-21-2017, 08:33 PM   #36
kri$han
Member
 
Drives: GTi 5-door Performance
Location: Toronto
Join Date: Sep 2017
Posts: 31
Quote:
Originally Posted by Zednix View Post
I drive a mix of city and highway, slightly more in city. I've been getting around 450km per tank on 91 in a stock 17 GTI+PP. Had the car since August and that has been roughly the average point the empty like comes on.
Same. Picked 'er up In September, and I only run 91, as well.

Quote:
Originally Posted by KingKhan View Post
I do mostly highway driving, but I have been routinely getting 600+ km per tank of 48L Regular. I imagine I can probably squeeze a few extra KM if I were to switch to premium\

I have just under 22K km on my 17 GTI
I think the opposite is true: lower octane tends to favor lower gas mileage (more efficiency), whereas those of us running 91 are getting a little less mileage. I'm usually around the 500km mark when the gas light comes on.

I notice this trend with my motorcycle as well; it feels more enthusiastic on 91, but it burns through the tank much faster than on 87.
kri$han is offline   Reply With Quote
Old 11-23-2017, 05:30 AM   #37
Tsi7
Member
 
Drives: 2015 golf 1.8 tsi
Location: Ontario
Join Date: Nov 2017
Posts: 86
Technically 91 is more efficient as it's less prone to uncontrolled combustion (aka detonation), but the idea is that if the car doesn't require 91 you'll just have more fuel that is unburnt. I'm pretty sure that's how octane works... now I can't speak for the tsi engines and if the ecu compensates for the difference in octane rating, but judging that the 170hp rating for the 1.8t was acheived using 91, I assume the ecu compensates since we can run 87. I've only done one take so far, got 483 (8.6 L/100km) but that was mainly because I had some fun with the new car. This tank trip computer says 7.8 but I'm guessing that's a little optimistic. Driving is anywhere from 50-50 or 60 city 40 highway
Tsi7 is offline   Reply With Quote
Old 02-13-2018, 06:37 AM   #38
Summons
Junior Member
 
Drives: 2018 Golf R DSG
Location: Toronto
Join Date: Jan 2018
Posts: 3
Quote:
Originally Posted by Tsi7 View Post
Technically 91 is more efficient as it's less prone to uncontrolled combustion (aka detonation), but the idea is that if the car doesn't require 91 you'll just have more fuel that is unburnt. I'm pretty sure that's how octane works... now I can't speak for the tsi engines and if the ecu compensates for the difference in octane rating, but judging that the 170hp rating for the 1.8t was acheived using 91, I assume the ecu compensates since we can run 87. I've only done one take so far, got 483 (8.6 L/100km) but that was mainly because I had some fun with the new car. This tank trip computer says 7.8 but I'm guessing that's a little optimistic. Driving is anywhere from 50-50 or 60 city 40 highway
Higher octane fuel detonates/knocks at a higher pressure and temperature than lower octane fuel. It also burns more slowly than low octane fuel at the same temp and pressure.

On an engine designed for 87, higher octane is likely a waste unless pushing the engine to extremes - by that I mean towing up hill on an old engine or such. In that case, the engine is working so hard, chamber temps climb, and the ECU can't do enough by enriching the mixture and adjusting timing to cool the temps to prevent detonation/knock.

If the engine is made for 91 and you feed it 87, you might get away with it if gentle and/or accept poor fuel economy. The ECU will dump extra fuel into the engine to prevent knock/detonation - the extra fuel acts as an octane boost, if I remember right, by cooling the charge (evaporate some more fuel and the phase change sucks up a bunch more heat) and over successive strokes, by preventing full combustion (due too rich) also cooling the chamber temps.

So in a turbo vs a normally aspirated engine of the same design (pretend you add a turbo to a N/A engine), the turbo is cramming more air in, raising the pressure, and when a turbo compresses the air it heats it up, so raises the temps as well, thus requiring higher octane fuel to prevent detonation and make sure the flame front is controlled as well.

On a side note that doesn't really apply to our tiny car engines, if the octane is way too high, you can burn your exhaust valves... This can happen in the typically huge aero piston engines. There, if the octane is too high for the engine, the flame front hasn't burnt all the fuel before the exhaust valve opens and you blow fire past the fragile valve edges... These engines have huge pistons - damn near paint can sized vs the pop can sized pistons cars typically use.
Cheers,
Eric
Summons is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 11:17 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.